Metabolic reprogramming is one of the most important hallmarks of malignant tumors. Specifically, lipid metabolic reprogramming has marked impacts on cancer progression and therapeutic response by remodeling the tumor microenvironment (TME). In the past few decades, immunotherapy has revolutionized the treatment landscape for advanced cancers. Lipid metabolic reprogramming plays pivotal role in regulating the immune microenvironment and response to cancer immunotherapy. Here, we systematically reviewed the characteristics, mechanism, and role of lipid metabolic reprogramming in tumor and immune cells in the TME, appraised the effects of various cell death modes  on lipid metabolism, and summarized the antitumor therapies targeting lipid metabolism. Overall, lipid metabolic reprogramming has profound effects on cancer immunotherapy by regulating the immune microenvironment; therefore, targeting lipid metabolic reprogramming may lead to the development of innovative clinical applications including sensitizing immunotherapy. The history of drug therapy for malignancies, such as cancer, has developed from chemotherapy to targeted therapy and then to immunotherapy. Currently, immunotherapy is the most promising antitumor treatment Metabolic reprogramming is one of the 14 important hallmarks of tumorigenesis in which the energy metabolism network of tumor cells is reset to support their growth, proliferation, and metastasis under the metabolic stress of the TME and immune surveillance Lipids are classified as simple and complex lipids; the simple lipids include triglycerides (TAGs), commonly known as fats. The complex lipids include sterols and their esters, phospholipids (PL), and glycolipids. In addition, ketone bodies, although not lipids are important intermediates of fatty acid oxidation (FAO). Lipids play an important function in cellular activities. In addition to serving as a key energy source Lipid metabolic reprogramming not only plays an important role in the oncogenesis and development of tumors but also modifies the TME by affecting the recruitment, survival, and function of immune cells Lipid metabolic reprogramming plays a critical role in sensitizing immunotherapy. Immunotherapy combined with therapies targeting lipid metabolism will provide a new direction for tumor treatment The most prominent function of lipids is to provide energy for cellular activities. TAGs are an important energy supply and storage material for cells. TAGs break down to yield fatty acids (FA), which undergo FAO and mitochondrial oxidative phosphorylation (OXPHOS) to produce large amounts of ATP. Lipids are not preferentially used by cells. Tumor and other immune cells rely on glucose metabolism when the supply is sufficient. However, when cells are activated or starving, especially under the metabolic stress of the TME, they switch to lipids for energy and material basis In addition, the intermediates of FAO, ketone bodies, are also available for cellular utilization. Immune cells can use ketone bodies as an alternative energy source in the absence of glucose; however, some tumor cells, such as glioblastoma (GBM), are classified as "glycolysis subtype" for the lack of ketone body oxidases, such as 3-hydroxybutyrate dehydrogenase (BDH1) or 3-succinyl-CoA transferase (OXCT1), because of genetic mutations or mitochondrial damage Lipids are the precursors of signaling molecules (lipid mediators), which participate in intra- and extra-cellular signal transduction. Arachidonic acid (AA) derivatives, including prostaglandins (PGs), thromboxanes (TXs), and leukotrienes (LTs), mediate the evolution of chronic inflammation into the tumor 2+ and induce calcium overload, and DAG activates protein kinase C (PKC) leading to oxidative stress, thereby disrupting intracellular homeostasis. In addition, LPA binds to the G protein-coupled receptors (GPCRs) on the membranes of tumor and immune cells and activates RAS, RAC, and RHO signaling pathways Metabolites of PL, including inositol triphosphate (IP3), diacylglycerol (DAG), and lysophosphatidic acid (LPA), are associated with multiple oncogenic signaling pathways and tumor immune responses Exosomes are one of the important forms of intercellular communication. Tumor cells can secrete numerous tumor-derived exosomes (TDEs) to transport signaling molecules to immune cells, thereby changing their metabolic state and inducing tumor immunosuppression. Lipids are the signaling molecules and also participate in the formation of the TDE membrane Lipids are important components of biological membranes and are involved in the transport of energy, materials, and information across membranes The type and saturation of FAs in the membrane affect its structural stability and function The key enzyme that regulates the type and saturation of FA in the membrane is stearoyl-CoA desaturase (SCD). Its Inhibition reduces the MUFA/SFA ratio and contributes to the induction of ferroptosis in tumor cells Lipid rafts are microdomains in cell membranes that are rich in cholesterol and sphingomyelin with long SFA chains; these chains contribute to the anchoring of LPs and the formation of relatively stable liquid regions. High levels of lipid rafts are present in the tumor cell membranes, where many tumorigenic proteins, such as CD44, epidermal growth factor receptor (EGFR), and insulin-like growth factor receptor are localized The great variability among lipids, in terms of their structure and properties, contributes to the remarkable diversity of lipid modifications. Among them, the most important is the acylation modification of proteins, in which FA is covalently linked to the peptide chain in the form of an acyl group Metabolic reprogramming of tumor cells can lead to abnormal lipid modification. In turn, the changes in lipid modification affect tumor metabolism and the occurrence and development of tumors Lipid metabolism, especially anabolism, is highly active in tumor cells to promote their survival and development in the TME, which is characterized by the high expression of receptors and key enzymes involved in lipid uptake, synthesis, storage, and decomposition. However, the expression of key enzymes is different because of the different types, stages, and microenvironments of tumors Table  61.The supply of exogenous lipids is easily affected by dietary intake. The occurrence and development of tumors are closely related to the amount and type of lipids consumed. High-fat diets  can increase the risk of cancer The transmembrane transport of exogenous lipids can be achieved through a variety of pathways. Low-density lipoprotein (LDL) enters the cell through endocytosis mediated by LDL receptor (LDLR), and it is subsequently digested by lysosomal acid lipase (LAL) to release free fatty acids (FFA) and cholesterol. LDLR is highly expressed in tumors and enhances the EGFR, PI3K/Akt, and sterol regulatory element-binding protein (SREBP) signaling pathways. Tumor metastasis is also associated with persistently high expression of LDLR De novo synthesis of FA begins with acetyl coenzyme A (AcCoA), which is mainly produced by glucose, glutamine Acetyl-CoA carboxylase (ACC/ACAC) catalyzes the conversion of AcCoA to malonyl-CoA, which can inhibit carnitine palmitoyltransferase 1 (CPT1)-mediated FAO in mitochondria, thereby regulating the balance between synthesis and decomposition of FA. In addition, activated AMP-activated protein kinase (AMPK) inhibits the activity of ACC1/2 Palmitic acid is subsequently elongated by the activity of elongation of the very long chain fatty acid (ELOVL) family of enzymes and converted to MUFA by SCD1. SCD1 can relieve the inhibitory effect of SFAs  on the activity of upstream ACC by reducing the SFA levels and subsequently increasing the production of malonyl-CoA, which affects FAO Furthermore, SCD1 affects the sensitivity of the cells to ferroptosis. On the one hand, inhibition of SCD decreases the MUFA/UFA in the membrane, and MUFA has an antiperoxidative effect, which, in turn, promotes ferroptosis A high level of cholesterol is essential for the proliferation and metastasis of tumor cells to fulfill the requirement for membrane structure. cholesterol also stabilizes PD-L1 on the tumor cell surface, thus inhibiting tumor immunity Cholesterol is primarily synthesized through the mevalonate (MVA) pathway. The key enzyme is HMG-CoA reductase (HMGCR), which is highly expressed in many cancers, and targeted inhibition of this enzyme has emerged as a potential therapeutic approach Excess lipids are stored in LDs in the form of TAG and cholesterol ester (CE). The number of LDs and the amount of stored TAG and CE inside them abnormally increases in tumor cells and tumor-associated immune cells  The core of an LD consists of neutral fats (mainly including TAG and CE) and is surrounded by a single layer of PLs and several proteins. Various enzymes involved in the synthesis of TAG and lipolysis are localized on the surface of LDs LD is a dynamically changing and multifunctional organelle The main function of FAO, known as β-oxidation, is to provide energy. In addition, it serves as a source of NADPH especially when glucose is deficient or the pentose phosphate pathway  is compromised The basic structure of cholesterol is cyclopentane polyhydrophenanthrene, which cannot be degraded completely. However, its oxidative metabolites, such as 27-hydroxycholesterol , affect tumor development. In the TME, 27-HC is mainly derived from macrophages and endothelial cells. 27-HC inhibits the uptake and synthesis of FA and cholesterol by inhibiting the SREBP pathway and activating the liver X receptor (LXR) pathway The catabolism of ketone bodies in tumor cells of the "ketone metabolic subtype" serves as an important energy source The expression of various key enzymes in lipid metabolism can be regulated by several signaling pathways, including AMPK and mammalian target of rapamycin (mTOR), peroxisome proliferator-activated receptors (PPAR), SREBP, and LXR signaling pathways. These pathways are further regulated by upstream signaling pathways such as p53, BRAF, PTEN, Ras, and Myc 2+ level, and oxidative stress increase AMP/ATP or ADP/ATP ratio and activate AMPK in cells, which promote catabolism and inhibit anabolism and confer resistance to metabolic stress AMPK and mTOR are mutually antagonistic key molecules in the regulation of energy metabolism. The factors, such as energy stress, increased CaSpecifically, AMPK enhances FA uptake through the upregulation of CD36 and other lipid transporters and inhibits SREBP signaling. In addition, AMPK activates autophagy directly or indirectly by inhibiting mTORC1 However, AMPK can also promote tumor growth and metastasis in some cases. For example, AMPK can prevent lipid peroxidation and inhibit antitumor immune responses by activating the production of antioxidants and inhibiting inflammatory responses through the NF-κB pathway When nutrients are sufficient, mTOR is activated instead of AMPK to promote anabolism and inhibit catabolism. mTORC1 and mTORC2 are two different complexes in the cell. mTORC1 promotes anabolism by activating ribosomal protein S6K (S6K) and inhibiting EIF4E-binding protein (4EBP) and is sensitive to rapamycin, whereas the mTORC2 promotes cell survival and proliferation by activating protein kinases such as AKT, SGK, and PKC and is not sensitive to rapamycin However, over-activation of mTOR can accelerate cell senescence and even induce cell death. Contrary to AMPK, mTORC1 induces mitochondrial oxidative stress by inhibiting the transcription factor PGC-1α, which promotes lipid peroxidation and calcium overload PPARs are ligand-induced nuclear receptors and are involved in several peroxide proliferation reactions, including metabolic and apoptotic pathways related to lipid metabolism. PPARs are generally highly expressed on tumor cells, and their expression is dependent on several factors such as PPAR subtype and type and stage of the tumor SREBPs are members of the nuclear transcription factor family. SREBP1 regulates FA metabolism The SREBP signaling pathway is abnormally activated in tumor and immune cells. Abnormally activated intracellular PI3K/Akt/mTOR signaling pathway promotes the expression of SREBP1 Similarly, LXRs synergize with SREBPs as key regulators of cholesterol homeostasis in cells. LXRs are activated by intracellular cholesterol or 27-HC and subsequently promote transcription of target genes encoding ATP-binding cassette transporter A1/G1 (ABCA1/G1), SREBP1a, and LDLR Immune cells can recognize and destroy tumor cells during immune surveillance. However, in the process of tumor immune editing, the products of tumor lipid metabolism not only modify the TME but also affect the recruitment and function of tumor-associated immune cells. Therefore, immune cells can act as guardians (antitumor immunity) as well as bystanders or even supporters (protumor immunity) Immune cells can be divided into two types based on their effect on tumors. Antitumor immune cells include effector CD8+T (Teff) cells, antitumor CD4+ (CD4+conv) cells, memory CD8+T (Tmem) cells, B cells, natural killer T (NKT) cells, NK cells, M1 macrophages, dendritic cells (DCs), and N1 neutrophils. Protumor immune cells include Treg cells, regulatory B (Breg) cells, M2 macrophages, myeloid-derived suppressor cells (MDSCs), and N2 neutrophils. Lipid metabolic reprogramming plays a crucial role in regulating the phenotype and function of immune cells. Although certain types of antitumor/protumor cells rely on both types of metabolism, in general, antitumor immune cells tend to rely on glucose metabolism to exert anti-tumor function, whereas protumor immune cells tend to rely on lipid metabolism to exert tumor immunosuppressive function  and TNF-α, and CD4+conv cells mainly exert an indirect antitumor effect by assisting Teff cells. Teff cells require an adequate supply of glucose for their antitumor functions. Although enhanced glycolysis is critical for T-cell activation, the upregulation of the TCA cycle and OXPHOS is equally important, and specifically, FAO also maintains the antitumor function of Teff cells Similarly, the metabolic bypass of glycolysis, that is PPP, is also upregulated with the activation of T cells to provide NADPH for lipid synthesis. However, the dependence of CD4+T cells on FAO promotes their differentiation into Treg cells Notably, CD8+T cells can generate a memory cell population (Tmem cells), which can persist after the tumor response fades; therefore, these cells are the key to long-term tumor control. Unlike Teff cells, Tmem cells, as quiescent cells, preferentially rely on FAO instead of glycolysis. These cells have significant mitochondrial reserves of FAs and further upregulate OXPHOS after activation B cells differentiate into plasma cells and produce tumor-specific antibodies to recognize and mediate tumor lysis through antibody-dependent cytotoxicity (ADCC) or complement-dependent cytotoxicity. B cells also promote the activation of T cells. In addition, B cells can directly kill tumor cells by secreting granzyme B and tumor necrosis factor-related apoptosis-inducing ligand NKT cells have the characteristics of both adaptive and innate immune cells and mainly recognize lipid antigens to play an immunomodulatory role. Therefore, lipid metabolism can promote the activation of NKT cells and regulate their cytotoxic effect. High levels of lactic acid in the TME reduced the expression of PPARγ in NKT cells, thereby decreasing lipid synthesis and production of IFN-γ. In addition, high levels of cholesterol in the TME can promote the secretion of IFN -γ by NKT cells and enhance the TCR signaling at immunological synapses of NKT cells NK cells can directly kill tumor cells by releasing cytotoxic granules and inflammatory cytokines or through ADCC. Glycolysis and OXPHOS are upregulated during the activation of NK cells, which is mediated by Myc, SREBP, and mTORC1 signaling pathways. Myc is regulated by mTORC1 and promotes glycolysis and OXPHOS in NK cells by promoting the expression of glucose transporter protein (GLUT) and key enzymes of glycolysis M1 macrophages exert antitumor immune responses by producing pro-inflammatory cytokines and inducible nitric oxide synthase and participating in ADCC. When TLR is activated, M1 macrophages show increased glucose uptake and lactic acid production. However, the lack of glucose and the accumulation of lactic acids in the TME promotes the transformation of macrophages from antitumor M1 to protumor M2 phenotype. In addition, M1 macrophages depend on NADPH produced through PPP. In the TME, PUFAs promote the aggregation of M1 macrophages accompanied by an increase in ROS, while SFAs inhibit the antitumor function of M1 macrophages. Notably, exogenously modified lipids, such as phosphotyrosine cholesterol, can polarize or even re-induce the antitumor M1 phenotype DCs, an important APC in antitumor response, switch from OXPHOS to glycolysis after activation. The transition process is mainly related to LPS/HIF-1α and TLR/PI3K/AKT pathways. In the lipid-rich TME, DCs tend to accumulate PL and TAG  rather than cholesterol and CE, which enhances the secretion of pro-inflammatory cytokines and chemokines, thereby playing a stronger antigen cross-presentation function and effectively activating NK, NKT, and Teff cells. In addition, 27-HC was found to induce the maturation of DCs. However, high levels of oxidized lipids and high accumulation of LDs limit the formation of the MHC I complex and impair the ability of DCs to present antigens and activate T cells. In addition, liver kinase B1 is an important metabolic regulator of DCs and the loss of its expression can activate the mTOR signaling pathway, resulting in metabolic disorders in DCs N1 neutrophils can exert antitumor effects by producing ROS, reactive nitrogen species, and IFN-α/β and phagocytosis. They can activate NK cells and inhibit IL-17-producing T cells Treg cells are the key cell population involved in adaptive tumor immunosuppression. Treg cells secrete inhibitory factors such as IL-4, IL-10, and transforming growth factor-β (TGF-β) and express inhibitory molecules such as CTLA-4, PD-1, and LAG-3 to inhibit the activation and function of other immune cells. Treg cells preferentially utilize the TCA cycle and OXPHOS for their metabolism. However, Treg cells are more dependent on FAO under the metabolic stress of the TME. In contrast to Teff cells, Treg cells show lower levels of GLUT1 and higher levels of monocarboxylate transporter 1 (MCT1), CD36, and FANS, which increase lactic acid and lipid metabolism to replace glucose metabolism. Similarly, the expression of genes and proteins related to glucose metabolism is downregulated in Treg cells, which are activated by TLR8 Breg cells also have an immunosuppressive function and inhibit the activation of T and NK cells. They also promote the protumor effect of Treg cells, MDSCs, and M2 macrophages by secreting IL-10, TGF-β, and ROS and upregulating PD-L1 and CTLA-4 The phenotype of tumor-associated macrophages (TAMs) is mainly the immunosuppressive M2 phenotype. M2 macrophages secrete various protumor factors such as arginase 1 (Arg1). M2 macrophages, like Treg cells, are mainly dependent on FAO. M2 macrophages tend to take up more lipids from the TME and enhance the synthesis of FAs to maintain their protumor function. For example, oleic acid can induce M2 polarization through the mTOR signaling pathway MDSCs are also important immunosuppressive cells that establish a complex tumor immunosuppressive network with other immune cells. Although glycolysis and OXPHOS are upregulated in MDSCs, these cells rely on FAO to maintain their protumor function Tumor-associated neutrophils (TANs) have protumor N2 phenotype. These neutrophils secrete Arg1, myeloperoxidase, neutrophil elastase, matrix metalloproteases, and neutrophil extracellular traps to promote tumor development and inhibit the activation and proliferation of T and NK cells The TME plays an important role in tumor immunity and immunotherapy. Tumor cells can alter the metabolism of the cells present in the TME, especially tumor-associated immune cells, which, in turn, interfere with the metabolism of tumor cells. Tumor cells have a high nutrient requirement; however, limited nutrient supply leads to metabolic stress in the TME, which mainly manifests as a hypoxic environment caused by a lack of oxygen and as energy competition caused by a lack of glucose. In addition, metabolites from tumor cells or other cells accumulate to create a low pH environment caused by lactic acid accumulation and a lipid peroxidative environment caused by lipid and ROS accumulation. Therefore, tumor and immune cells undergo metabolic reprogramming to circumvent these limitations, thereby affecting tumor immune response Figure  165.The number and composition of immune cells in the TME are heterogeneous. Some tumors are classified as “cold tumors” because of a lack of immune cell infiltration and present an “immune desert.” However, some tumors are classified as "hot tumors" because they are rich in immune cells. Apparently, a “hot tumor” is more responsive to immunotherapy than a “cold tumor” In addition to immune cells, cancer-associated fibroblasts (CAFs) are the most important component of stromal cells in the TME and are the center of cross-communication between various cells. CAFs can secrete several cytokines, chemokines, and extracellular matrix proteins, thereby promoting the occurrence and development of tumors Tumor cells have high oxygen requirements to support their rapid proliferation but the relatively slow and abnormal angiogenesis causes insufficient oxygen supply, which often leads to local hypoxia in tumor tissues. Necrosis, occurring in the hypoxic area, releases tumor antigens to activate the tumor immune response The functions of some key enzymes of lipid metabolism are affected in a hypoxic environment. For example, SCD1 needs oxygen to catalyze the formation of carbon double bonds to desaturate FAs. Therefore, SFAs are accumulated in the absence of oxygen by preventing the formation of UFAs. Tumor cells enhance the uptake of UFA and its release from LD to restore the SFA/UFA balance. However, hypoxia can also increase the expression of SCD1 through the regulation of SREBP1 HIF-1α and hypoxia-related genes, such as EPAS1, are highly expressed in various hypoxic tumor tissues, which play an important role in tumor angiogenesis, metabolism, and immunity Tumor cells are more sensitive to glucose deficiency than other cells in the TME because of their high energy requirements. Tumor-associated immune cells can partially use ketone bodies as alternative energy sources but "glycolysis subtype" tumor cells cannot use ketone bodies instead of glucose However, glucose metabolism plays an irreplaceable role in the occurrence and development of tumors. As an important carbon source, intermediates of glycolysis and aerobic oxidation, such as glucose-6-phosphate and pyruvate, can be used as the essential material basis. Specifically, the TCA cycle and PPP provide AcCoA and NADPH for lipid synthesis, respectively. Glycolysis also provides glycerol 3-phosphate for the synthesis of TAG. Compared with FAO and OXPHOS, the rapid energy supply provided by glycolysis can meet the emergency energy needs of tumor cells during proliferation or metastasis. Glycolysis reduces the dependence on oxygen and mitochondrial function, which reduces the production of ETC-derived ROS and inhibits lipid peroxidation. The lactic acid produced by glycolysis can acidify the TME and induce tumor immunosuppression. Hexokinase (HK), a key glycolytic enzyme, inhibits the apoptosis of tumor cells Therefore, tumor cells compete for glucose and outdo immune cells by upregulating GLUT and other pathways The supply of glucose is equally important for the activation of immune cells, specifically antitumor immune cells. The lack of glucose hinders the activation of T cells, and T cells undergo metabolic reprogramming and shift toward lipid metabolism for survival by activating the AMPK pathway, PPARα signaling pathway, and FAO. In addition, T cells differentiate into Treg cells in response to low glucose levels, which is dependent on the activity of AMPK and PPARα signaling pathways Accumulation of lactic acid produced by glycolysis lowers the pH of the TME. The acidic environment can theoretically lead to apoptosis, thus playing an antitumor role. However, lactic acid transported to the stroma is quickly taken up by tumor cells through MCT1 and utilized in the normal oxygen supply area, thereby maintaining optimal lactic acid levels in the TME for protumor effect. Moreover, metabolic stress of the TME can promote the expression of MCT1, which can also activate the NF-κB signaling pathway Lactic acid has traditionally been considered a metabolic waste; however, a study has indicated that it can upregulate the expression of vascular endothelial growth factor (VEGF) and HIF-1 + have long been regarded as negative regulators of immunity, but recent studies have indicated that lactic acid can have immune-promoting effects. Lactic acid and H+ can inhibit the survival and function of T cells by inhibiting the MPAK signaling pathway + should be distinguished while evaluating the effect of low pH on antitumor responses.Lactic acid and H+ produced by redox reactions occurring in tumor cells can be mainly transported out of the cell via V-ATPases to prevent acidosis and maintain a low pH environment 2 produced by intracellular decarboxylation reaction can diffuse to the TME, which results in a low pH environment and affects the survival and function of immune cells In addition to lactic acid, HFor lipid metabolism, acidic conditions mediate the transport of FA by CD36 and promote the storage of PUFA in LDs, thereby increasing lipid accumulation in tumor cells Most solid tumors are rich in lipids, which are obtained from the surrounding cells or bloodstream. Tumor cells can induce metabolic changes in adjacent adipocytes to release FFA and cholesterol into the TME and then absorb them through FATP Tumor cells often upregulate lipid uptake and storage to adapt to the low-glucose and high-fat TME. The uptake of ox-LDL by tumor cells promotes the occurrence and progression of tumors because it affects mitosis, regulates the expression of cyclin, and induces the expression of endoplasmic reticulum localization protein (Nogo-B) The high-fat environment has a bidirectional effect on tumor immune response. The high level of FA can activate PPARα signaling in T cells, which, in turn, promotes FAO and OXPHOS; however, the depletion of FA in T cells hinders their proliferation and antitumor effect Autophagy is considered a self-protective mechanism of cells. In the TME, metabolic stress, oxidative stress, and immune signals can induce autophagy by increasing the activity of autophagy-related genes and the ability of intracellular lysosome transport, which allows for efficient degradation of cellular components. Autophagy is regulated by two antagonistic regulatory kinases, AMPK (activator) and mTORC1 (inhibitor) 2+ and increases the intracellular labile iron pool. In addition, mtDNA stress triggered autophagy-dependent ferroptosis Tumor cells can achieve energy recycling and substance renewal through autophagy, which increases the lipid pool and helps tumor cells adapt to the nutrient competition Autophagy also affects the tumor immune response. Autophagy can selectively degrade MHC I molecules, thereby reducing the immunogenicity of tumor cells. In contrast, the inhibition of autophagy in tumor cells can increase the expression of tumor surface antigens. Autophagy in MDSCs degrades MHC II molecules and inhibits the activation of T cells Overall, autophagy is a double-edged sword for tumor and immune cells. Inhibition of autophagy promotes antitumor immune responses to a certain extent and represents a novel direction for cancer immunotherapy Lipid peroxidation is the process by which ROS reacts with PL, enzymes, membrane receptors, and other PUFA side chains to form lipid peroxidation products (LPO) such as MDA and HNE. It eventually destroys membranes and important cellular components such as proteins and nucleic acids 2O2 by superoxide dismutase (SOD). Moreover, the clearance rate of ROS is lower in tumor cells. Unlike normal cells, tumor cells have low levels of antioxidant enzymes and their antioxidant barrier is defective. Therefore, tumor cells inhibit lipid peroxidation by reducing mitochondrial activity (Warburg effect), increasing the production of PGs, and reducing the level of PUFA in the membrane. Low levels of ROS are often maintained in tumor stem cells and tumor cells in the proliferative state or with drug resistance Tumor cells are more susceptible to lipid peroxidation than normal cells. The production rate of ROS is higher in tumor cells. ETC is prone to leak out ROS during OXPHOS because of the defects in intracellular mitochondria and the dependence of energy metabolism on them. In addition, intracellular NADPH oxidase can produce superoxide, which is rapidly converted to HHowever, long-term maintenance of moderate levels of ROS is beneficial for tumor progression. ROS-induced DNA damage leads to genomic instability, which drives the accumulation of oncogenic mutations. A certain level of ROS and LPO act as secondary messengers to activate related transcription factors and participate in the regulation of signaling pathways, such as PI3k/Akt, RTK/Ras, VEGF, NF-κB, and COX-2, to promote tumor inflammation and immune response Taken together, the bidirectional effect of lipid peroxidation on tumors suggests that different types and stages of tumors and immune responses have different requirements for the expression of ROS and LPO; therefore, tumor immunotherapy targeting lipid peroxidation should be carefully designed Ferroptosis, a newly emerged form of non-apoptotic regulatory cell death caused by LPO overload in the membrane, is considered a by-product of abnormal lipid metabolic reprogramming. The balance between ferroptosis-related peroxidation and antioxidation systems determines whether the cell undergoes apoptosis or not Oxygen and iron are essential factors in the ferroptosis-related peroxidation system that drive lipid peroxidation to produce phospholipid peroxides (PLOOH), which can damage the structure of membrane lipids if not effectively neutralized. ACSL4 converts PUFAs into their respective acyl-CoA, while LPCAT3 promotes the esterification and incorporation of PUFA-CoA into membrane PLs The System X-(SXC)/GSH /GPX4 and FSP1/CoQ10/NADPH axes are two major monitoring systems in the ferroptosis-related antioxidant defense system to inhibit PL peroxidation and prevent ferroptosis. SXC, GPX4, and FSP1 are highly expressed in tumors and are related to the poor prognosis of patients, suggesting that tumor cells tend to inhibit their ferroptosis Notably, ferroptosis may also occur in immune cells, and this may be a specific mechanism of tumor immunosuppression. For example, CD36-mediated uptake of FA by CD8+T cells in the TME can induce lipid peroxidation and ferroptosis, which reduce the production of cytotoxic cytokines and decreases their antitumor ability 2+ is a necessary cofactor for enzymes that mediate basic cellular functions, including mitochondrial respiration and redox reactions. Although Cu2+ does not participate directly in the mitochondrial respiratory chain, it promotes the activity of key enzymes in the TCA cycle and inhibits the leakage of ROS from the respiratory chain. Therefore, compared with normal cells, tumor cells need higher levels of Cu2+ to maintain mitochondrial metabolic activity and intracellular redox balance. The level of Cu2+ in serum or tumor cells of tumor patients is higher than that in normal individuals, which can induce cuproptosis in cells Cu2+ can directly bind to the lipoacylated components of the TCA cycle, such as dihydrolipoic acid transacetylase (DLAT), and result in the abnormal aggregation of insoluble DLAT and subsequent downregulation of Fe-S cluster proteins, eventually leading to proteotoxic stress and ultimately cell death. Therefore, cells dependent on mitochondrial respiration are more sensitive to Cu2+ ions than cells that rely on glycolysis 2+ promotes the accumulation of ROS and induces lipid peroxidation. Cu2+ can also directly activate various angiogenic factors, including VEGF, fibroblast growth factor 2, TNF-α, and IL-1, thereby promoting tumor angiogenesis. Cu2+ regulates autophagy through ULK1 and ULK2 (serine/threonine kinases). High levels of Cu2+ are associated with an increased expression of PD-L1, which may help tumors resist immunotherapy 2+ and tumor-associated immune cells and established models to predict the effect of Cu2+ on tumor immunotherapy.Excessive Cu2O2 -dependent Ca2+ channel) on the surface of tumor cells in the TME leading to massive Ca2+ influx. The excessive intracellular Ca2+ further increases the uptake of Ca2+ by mitochondria, which leads to the formation of calcium phosphate deposits and inhibits ATP synthesis. Consequently, the activity of the Ca2+ pump in the endoplasmic reticulum and cell membrane further decreases, which, in turn, increases intracellular Ca2+ levels. Then, excessive Ca2+ can abnormally activate various Ca2+-dependent degradation enzymes. For example, the phospholipase activation promotes the hydrolysis of PLs, resulting in membrane destruction Mitochondria, as an intracellular calcium pool, are involved in the regulation of intracellular calcium homeostasis. Lipid peroxidation increases the permeability of the membrane under oxidative stress. ROS activate TRPM2  channels are associated with the proliferation of tumor cells. Notably, extracellular zinc exerted rapid inhibitory effects on SOCE and intracellular Ca2+ oscillations in the ESCC cells, thereby suggesting a possible molecular basis for zinc-induced cancer prevention However, cell migration and invasion in some tumors, such as glioblastoma and esophageal squamous cell carcinoma (ESCC), are critically dependent on Ca2+ nanoparticles and calcium hydride (CaH2) administration, are being evaluated to induce calcium overload in tumor cells to assist immunotherapy and develop a new tumor treatment strategy, namely ion interference therapy Calcium overload can activate the GSDME protein, which induces pyroptosis in tumor cells and sensitizes immunotherapy. Currently, several methods, such as CaTargeting lipid metabolism is more sensitive and beneficial than targeting glucose metabolism for tumor immunotherapy. Tumors with metabolic heterogeneity are more adaptable to interventions in glucose metabolism. Further, drugs that target glucose metabolism can also inhibit antitumor immune cells because of their dependence on glucose. In contrast, protumor immune cells are mainly dependent on lipid metabolism and tumor cells are more sensitive to lipids than glucose. In addition, existing drugs for disorders of lipid metabolism and NSAIDs can also be reused to treat abnormal lipid metabolism in the TME However, although lipid metabolic reprogramming leads to an immunosuppressive TME, lipid remains the important energy and material basis of the cells for antitumor immune response. Therefore, therapies targeting lipid metabolism should be specific and targeted to certain components and pathways of lipid metabolism in different types and stages of tumor and immune cells to maximize their sensitizing effects on immunotherapy CD36 inhibitors hinder tumor development, specifically metastasis and angiogenesis in the TME In addition, the potential protumor role of the FABP has been demonstrated. The inhibition of FATP reduces lipid uptake, invasion, and growth in tumors such as melanoma in vivo efficacy of existing ACLY inhibitors in tumor models  has not been definitive; however, the recently identified 3D structure of ACLY holoenzyme tetramer is expected to provide new insights into the mechanism of ACLY inhibition leading to the development of effective ACLY inhibitors The development of tumor cells and immune cells is affected by the expression of ACLY and its product AcCoA. Inhibition of ACLY can reduce the levels of intracellular FA and cholesterol and inhibit upstream glucose metabolism The pathway of AcCoA synthesis by acetyl-CoA synthetase (ACSS) can bypass the inhibition of ACLY, which makes tumor cells resistant to ACLY inhibitors. Therefore, ACSS2 inhibitors not only hinder the growth of acetate-dependent tumors but also improve the antitumor effect of ACLY inhibitors. In addition, ACSS2 inhibitors promote antitumor immune responses. The expression of ACSS2 in cervical squamous cell carcinoma is proportional to that of PD-L1 and is associated with the infiltration of B cells, CD4+T cells, CD8+T cells, and CAFs ACC inhibitors can impede the growth of the tumor and enhance the efficacy of chemotherapy and targeted drugs FASN inhibitors inhibit the energy supply of tumor cells and disrupt their membrane composition. Specifically, FASN inhibitors can induce ferroptosis in tumor cells by reducing the levels of intracellular TAG and PC and increasing the levels of PUFA in the membrane through the Lands cycle. In addition, FASN inhibitors promote the formation of lipid rafts and the activation of the TLR4 signaling pathway Currently, SCD1 inhibitors are in the preclinical stage, and the existence of SCD1 compensatory or alternative pathways can easily make tumor cells resistant to SCD1 inhibitors. The expression of the transcription factor FOSB, which regulates the activity of SCD1, rapidly restores the SCD1 level and induces drug resistance The expression of monoacylglycerol lipase (MAGL) is markedly elevated in many tumor cells, which leads to an increase in intracellular FFA levels that are closely related to cancer-associated cachexia The drug-resistant tumor cells, such as TNBC, exhibit dependence on FAO COX-2 inhibitors are effective in the prevention and treatment of tumors  and prostate cancer The mechanism of COX-2 inhibitors is not entirely dependent on the role of COX-2 but is related to COX-1 or even independent of the PGE2 pathway. COX-1 is highly expressed (even more than COX-2) in ovarian and cervical cancers. Therefore, COX-1 inhibitors are more effective in treating these COX-1-dominated tumors LDLR is upregulated through EGFR/PI3K/AKT/SREBP-1 signaling, which enhances the uptake of LDL-C and plays an important role in the growth of cancers such as lung cancer and breast cancer Statins, in addition to lowering blood lipids, can inhibit the activity of HMGCR. They can remodel the cytoskeleton and lipid rafts by reducing cholesterol in the membrane, thereby inhibiting the proliferation and metastasis of the tumor Of note, fat-soluble statins have better antitumor effects than water-soluble statins but the mechanism is unknown Squalene synthase (SQS) and squalene epoxidase (SQLE) also affect the synthesis of cholesterol and tumor immune response. SQS inhibitors not only interfere with the squalene synthesis downstream but also increase the CoQ10 synthesis upstream, which may diminish their antitumor effect The high expression of ACAT1 in tumor-associated immune cells can reduce the level of intracellular free cholesterol and promote the composition and function of the membrane. For example, ACAT1 inhibitors can enhance the cholesterol level in the membranes of CD8+T cells and promote the formation of immune synapses, which enhances immune recognition and cytotoxic effects of CD8+T cells In contrast to the key enzymes and receptors specific for lipid metabolism, targeting the upstream regulatory pathways is more complicated because such pathways are also involved in regulating other cellular processes, such as glucose metabolism, amino acid metabolism, and autophagy. The drugs targeting the regulation of lipid metabolism fail to achieve ideal therapeutic effects and show various side effects or even the paradoxical phenomenon that both forward and reverse regulation of the same signaling pathway will produce antitumor effects. Therefore, underlying mechanisms need to be further studied Presently, some AMPK agonists, such as metformin, have been reported to have good antitumor effects and are being tested in clinical trials AMPK pathways act through mTORC1 inhibition; therefore, inhibition of mTOR signaling has been explored as an antitumor strategy but the results were not optimal The function and expression of PPARs are heterogeneous in different types and stages of tumors. PPARα/γ agonists exert antitumor effects by lowering blood lipids and promoting FAO. In addition, PPARγ agonists have been found to inhibit tumor proliferation, invasion, and angiogenesis. PPARγ agonists can also enhance the function of CD8+T cells and promote the effectiveness of anti-PD-1 therapy SREBP1 inhibitors can significantly inhibit the growth of tumor cells. Currently, most of the SREBP1 inhibitors are in the preclinical evaluation stage. SREBP1 inhibitors can enhance the effect of radiotherapy, anti-PD-1 therapy, and polyadenosine diphosphate ribose polymerase inhibitors. SREBP1 inhibitors have also been found to reverse the immunosuppressive effect of Treg cells and reduce the protumor effect of M2 macrophages LXR agonists can cause the depletion of cholesterol in tumor cells and thus reduce lipid raft signaling. In addition, LXR agonists can induce caspase-dependent apoptosis and block survival signals such as EGFR and Akt KD therapy activates ketogenesis in the body through a high-fat low-carbohydrate diet, thereby increasing the concentration of ketone bodies in the blood to replace glucose as the main energy source. This therapy inhibits "glycolysis subtype" tumor cells but is less effective against immune cells. Furthermore, KD therapy can improve the ability of immune cells to resist oxidative stress and thus promote antitumor immunity In addition to directly targeting tumor cells, CD8+T cells can also promote the ferroptosis of tumor cells. T-cell-derived IFN-γ combines with arachidonic acid to activate ACSL4, and the activated enzyme increases the levels of PUFA in the cell membrane, thereby changing the lipid distribution pattern of tumor cell membranes. These changes increase the susceptibility of membranes to lipid peroxidation and naturally induce ferroptosis of tumor cells. However, ACSL4 is the key enzyme of lipid metabolism, which mediates the remodeling of GPLs and the activation of FAs LPCAT3 further increases the ferroptosis sensitivity of tumor cells. LPCAT3 knockout reduced the composition of PUFA-PL in tumor cells, thereby inhibiting ferroptosis and promoting tumor progression Iron-catalyzed oxidation and enzymatic oxidation ultimately lead to ferroptosis and are the two targets in the context of current research on ferroptosis-targeting therapies. The growth of tumor cells  depends on the role of iron, and high iron intake increases the risk of tumors (such as HCC and breast cancer) GPX4 and SXC are key enzymes that inhibit ferroptosis. Knockout of GXP4 or inhibition of SXC leads to the accumulation of intracellular LPO, resulting in ferroptosis of tumor cells. Many antineoplastic drugs targeting GPX4 and SXC are also being studied or used clinically; these drugs include SLC7A11 inhibitors  Targeting ferroptosis in tumor cells may exert unintended effects on CD8+T cells in the TME. CD8+T cells are more sensitive to ferroptosis induced by GPX4 inhibitors, and overexpression of FSP1 induces ferroptosis resistance and maintains CD8+T cell function (antitumor activity) in the TME. Therefore, FSP1 may have potential therapeutic applications in cancer immunotherapy. Promoting the ferroptosis of immunosuppressive cells, such as Treg cells, M2 macrophages, and MDSC, is a potential antitumor strategy and ferroptosis-targeting drugs may emerge in the future The therapies targeting lipid metabolism exploit the biological characteristics of lipids, whereas the physical and chemical properties of lipids, such as liposolubility and polarity, determine their use as effective drug carriers, including exosomes and liposomes.Currently, the immunotherapy strategies that target exosomes mainly inhibit the production of TDEs or interfere with the exosomes released from immune cells. GW4869 is an inhibitor of neutral sphingomyelinase, which inhibits the production of TDEs and exerts an antitumor effect. DC-derived exosomes contain tumor antigens; therefore, TAE-DC vaccines have been developed to activate T cells in the TME Several key enzymes and products of lipid metabolic pathways can be used as markers for the development of tumors and tumor immunity Lipid metabolic reprogramming plays an essential role in TME and cancer immunotherapy. Here, we described the characteristics, mechanism, and role of lipid metabolic reprogramming in tumor and immune cells interacting in the TME. Importantly, lipid metabolic reprogramming even could determine cell fate, which is manifested in the regulation of different cell death modes, especially ferroptosis. Further, we summarized the potential clinical applications of targeting lipid metabolic reprogramming for antitumor therapies and as a tumor biomarker. Given the complexity of lipid metabolic reprogramming and the continuous research efforts to identify the critical genes and pathways involved, researchers will discover several candidate genes/proteins for diagnostic and therapeutic purposes. In addition, lipid metabolic biomarkers have shown potential for monitoring immunotherapy; therefore, they should be the primary focus of future research. Overall, an improved understanding of lipid metabolic reprogramming will provide useful insights into mechanisms of tumorigenicity and may lead to the development of novel therapeutic approaches for patients with cancer.


Al Rifai 1 In patients with recurrent symptoms after revascularization, stress imaging can reveal myocardial ischaemia as the underlying cause of symptoms and provides prognostic information. In a meta-analysis including a total of 12 874 symptomatic or asymptomatic patients with a history of revascularization, abnormal results at nuclear myocardial perfusion imaging (MPI) or stress echocardiography were associated with an average of two-fold risk of cardiac events.2 More recently, the presence of inducible ischaemia on stress perfusion cardiac magnetic resonance was found an independent predictor of cardiovascular events after CABG.3Patients remain at risk of cardiovascular events after coronary artery bypass graft surgery (CABG) that is partly related to the progression of coronary artery disease (CAD) in native coronary arteries and bypass grafts.4 Furthermore, impaired MBF and myocardial flow reserve (MFR) in response to vasodilator stress is a strong prognostic marker.5 In patients with prior CABG, the ischaemic burden on PET provides prognostic information in predicting all-cause mortality and cardiac deaths.6 However, the prognostic value of MFR assessed by PET is unclear in this population.Positron emission tomography (PET) myocardial perfusion imaging accurately detects obstructive CAD. Measurement of myocardial blood flow (MBF) in absolute units  using PET can improve the diagnostic evaluation of CAD over relative perfusion differences.et al.7 report the prognostic value of MFR in a cohort of 836 patients with a history of CABG who underwent rest-stress 82Rb PET MPI due to a clinical indication for evaluation of ischaemia. Up to 66% of patients had MFR <2, a pre-defined cut-off value for abnormal MFR.4 Patients with abnormal MFR were older and more often men, hypertensive and diabetic, had lower left ventricular ejection fraction (LVEF), and were more likely to have scar or regional inducible ischaemia. Over a median follow-up time of 12 months, 122 patients suffered an adverse event, including 46 heart failure admissions, 28 all-cause deaths, 23 myocardial infarctions, and 25 unplanned late revascularizations. Reduced MFR was a predictor of outcome in adjusted analyses on top of early revascularization, clinical variables, and other PET parameters, including LVEF, LVEF reserve, regional perfusion defects, and transient ischaemic dilatation. Patients with abnormal MFR had a higher rate of the composite outcome  than those with normal MFR; the cumulative incidence of events being 18.4 vs. 7.1%.Al Rifai 8 In the study of Al Rifai et al., both regional ischaemia and abnormal MFR were common findings in patients with a history of CABG.7 However, there was no interaction between ischaemia and MFR in predicting the outcome, and MFR was prognostic irrespective of the presence of scar. Thus, regional perfusion abnormalities and MFR may identify different prognostic phenotypes and have implications for the selection of therapy. Observational studies have found that the reduced MFR may identify patients with survival benefit from early revascularization when compared with medical therapy.9 Such a study requires a large patient cohort and remains to be studied in patients with a history of CABG in whom the decision to proceed with repeat revascularization requires careful weighing of the risks and potential benefits. The use of evidence-based medical therapy is strongly associated with favourable outcomes after myocardial revascularization,10 and there is also an interest in reduced MFR as a potential target for novel therapies.8Impaired MFR may be due to obstructive epicardial CAD, diffuse CAD, or microvascular dysfunction.11 Hybrid imaging with coronary CTA and stress MPI has been shown to provide useful complementary information in patients with a history of CABG enabling the integration of myocardial perfusion abnormalities with the anatomy of subtending coronary arteries or bypass grafts.13In patients with a history of CABG, incomplete revascularization, occlusion of bypass grafts, and progression of CAD in the native coronary arteries can contribute to the presence of residual ischaemia. Coronary computed tomography angiography (CTA) has been shown to accurately identify stenosis in both venous and arterial bypass grafts. The presence of coronary artery territories supplied by an obstructed native coronary artery in the absence of patent bypass graft, or obstruction of a coronary artery distal to the graft insertion, predicts adverse cardiac events in patients with a history of CABG.14 A study found that impaired MFR is independently associated with diastolic dysfunction and risk of heart failure hospitalization in patients with preserved LVEF.15 Notably, in the study of Al Rifai et al., reduced MFR showed a particularly strong association with heart failure admissions (hazard ratio 2.92).7 Furthermore, both LVEF and MFR were significant predictors of the primary outcome in the adjusted model.Coronary microvascular dysfunction often co-exists with epicardial CAD, but is also common in the absence of CAD in patients with various forms of cardiomyopathy and heart failure with either reduced or preserved LVEF.et al. extends the evidence regarding the prognostic value of reduced MFR in CAD to patients with a history of CABG, suggesting that MFR may provide incremental risk prediction beyond regional myocardial ischaemia and LVEF. The study encourages further evaluation of the value of MFR in optimizing therapies to improve outcomes after myocardial revascularization.The study of Al Rifai


Pharmacogenetics (PGx) is the study and application of how interindividual differences in our genomes can influence drug responses. By evaluating individuals’ genetic variability in genes related to drug metabolism, PGx testing has the capabilities to individualise primary care and build a safer drug prescription model than the current “one-size-fits-all” approach. In particular, the use of PGx testing in psychiatry has shown promising evidence in improving drug efficacy as well as reducing toxicity and adverse drug reactions. Despite randomised controlled trials demonstrating an evidence base for its use, there are still numerous barriers impeding its implementation. This review paper will discuss the management of mental health conditions with PGx-guided treatment with a strong focus on youth mental illness. PGx testing in clinical practice, the concerns for its implementation in youth psychiatry, and some of the barriers inhibiting its integration in clinical healthcare will also be discussed. Overall, this paper provides a comprehensive review of the current state of knowledge and application for PGx in psychiatry and summarises the capabilities of genetic information to personalising medicine for the treatment of mental ill-health in youth. Interindividual differences in our genomes occur within and between demographic populations, leading to genomic variation and individual phenotype presentation . VariatiThe factors affecting drug efficacy and toxicity can have significant consequences for patient health outcomes and contribute to personal and national economic loss associated with avoidable hospital admission. In regard to the United States Food and Drug Administration’s (FDA) top ten highest-grossing drugs, for every person experiencing a therapeutic benefit, it is estimated that between three and 24 individuals fail to show any response . A recenMental health disorders represent a significant proportion of the burden of disease in youth worldwide . People This review comprises three sections. The first section presents an overview of PGx and its role in clinical practice, with a particular focus on the role of cytochrome P450 (CYP) drug-metabolizing enzymes. The second section investigates the involvement of CYP enzymes in the metabolism of antidepressant medication and the use of PGx in improving mental health outcomes in randomized clinical trials. The third section addresses the application of PGx testing in youth mental health, evaluating the existing barriers hindering the implementation of PGx in primary healthcare. It explores the gaps in the literature pertaining to PGx in psychiatric care and provides recommendations for future research required to progress PGx into routine clinical practice.PGx comes under the umbrella term “pharmacogenomics”, encompassing the understanding of how an individual’s genetic makeup (genotype) may influence their metabolic status (phenotype) and overall response to a drug, in the context of both efficacy and toxicity . PharmacGenetics influences pharmacodynamic and pharmacokinetic properties. In particular, affecting how a drug is absorbed, distributed, metabolised, and excreted in an individual, all factors contributing to drug efficacy and tolerability  Kalow, . VariatiVariations in genes encoding drug metabolizing enzymes, transporters, and/or pharmacological receptors have been shown to have a profound impact on an individual’s drug response . InvolveCYP2C9, CYP1A2, etc.)  . Current2, etc.) . A numbe2, etc.) . Recognibolisers . This inCYP2C19 has been reported in Asian populations (∼15–30%) compared to populations of European, African, and Arab decent (∼3–6%) (CYP2D6 gene appears to be higher in Europeans and Caucasian Americans (∼7%) than in Asian populations (∼1%). Differences in CYP allele carriage such as these may possibly lead to large variances in clinical drug responses between ethnically diverse groups, disadvantaging minority backgrounds  . Similarkgrounds .de novo mutations, but more likely to provide advantageous evolutionary traits (Hypericum perforatum) extract has long been associated with relieving the symptoms of mild depression, demonstrating a high safety and efficacy profile  related to their prescription medication . By currMental health disorders are among the most prevalent health conditions in Western society . The WorCYP1A2-encoded enzymes, 5% by CYP2B6, 38% by CYP2C19, 85% by CYP2D6, and 38% by CYP3A4, however, this may vary subject to age, sex, and ethnicity related differences , selective serotonin reuptake inhibitors (SSRIs), and serotonin-noradrenaline reuptake inhibitors (SNRIs) , over 40 variations are known to encode inactive or non-functional enzymes, with other variations encoding ‘normal’ or increased enzymatic activity  are ultrarapid metabolisers  . The intactivity . Similarbolisers . With thoutcomes . DemonstCYP2D6 and CYP2C19 alleles with antidepressant metabolism in patients with depression, intermediate metabolisers have shown better responses to antidepressant medication with ultrarapid metabolisers presenting a higher risk of suicide than other metabolic phenotypes  assessing the clinical utilisation of PGx testing as a predictive tool to guide prescription. Two RCTs published by CYP2D6, CYP2C19, CYP1A2, as well as two genes encoding serotonin transporters (SLC6A4) and receptors (HTR2A). Similarly, two recent meta-analyses examining 1,737 participants over five RCTs and 5,347 participants over 11 RCTs, showed that PGx-guided treatment and tailored prescription and dosing were associated with higher remission rates and faster response times when compared to standard treatment in difficult-to-treat-depressive patients  are often the first level of contact in the Australian healthcare system, with mental health related issues representing one of the most common health issues managed by GPs . HoweverAlthough the studies above illustrate a keen understanding on the usefulness for PGx testing in the primary care setting, with no endorsed guidelines on the use of PGx testing in clinical practice, many GPs have expressed the need for further research that explores the translation of new genetic technologies into clinical practice to help inform the development of such guidelines. The review by As well as those of GPs, the knowledge and attitudes of the patient towards PGx testing are reported in the literature. Lastly, societal expectations around data privacy, equity, and economic values may provide a hurdle in normalising PGx-guided treatmentTo navigate the barriers and educate the public on the potential benefits of PGx-guided treatment for improved mental health outcomes in youth, it is important that researchers engage with the communities that will benefit from the adoption of this technology.Mental health conditions are becoming increasingly prevalent in Australian society and throughout the Western world, particularly in our youth. The management of mental health conditions in youth is complex and, if not handled correctly, can exacerbate mental ill-health and risk the persistence of these conditions into adulthood. Although there have been improvements in symptom recognition, diagnostic guidelines, and the availability of pharmacotherapies, there remain many challenges in the management of mental health in young people. PGx testing has been shown to provide an increased chance of achieving a therapeutic outcome, minimising harmful ADR and their flow on effects. Current research suggests that an informed knowledge of youth’s specific PGx characteristics could be expected to enhance the treatment and recovery from mental illness. Although there are barriers to the use of genomic testing in youth, the field of PGx continues to develop and advances in this area have led to an increased accessibility of DNA testing and PGx-guided treatment. Whilst emerging literature has shown PGx testing may be utilised in the care of young people with mental illness, there is a need for more large-scale age-appropriate studies to resolve conflicting research. In addition, further studies are needed to explore how this testing could be incorporated into standard clinical practice, navigating social, behavioural, and economic barriers. With most mental illness in Australia managed in primary care, it is important that the application of PGx testing in youth is extensively studied in the context of primary healthcare settings. Therefore, future research in PGx-guided treatment needs to acknowledge the experiences of youths themselves and the concerns of their primary care providers, involving key stakeholders in the research process to ensure personalised and effective care.


Diabetic kidney disease (DKD) is one of the main complications of diabetic microangiopathy. The pathogenesis of DKD is very complex, including autophagy, inflammation, oxidative stress. Although a series of treatment intervention have achieved certain results in the treatment of diabetic nephropathy, still cannot reverse the kidney injury of diabetic nephropathy. The kidney is one of the most important organs of energy metabolism. Renal function is highly dependent on phagocytosis of mitochondria, and aberrant or defective autophagic mechanisms are central to the pathology of many renal diseases. Under high glucose conditions, mitochondrial fragments accumulate in the kidney, suggesting that mitochondrial clearance mechanisms may be attenuated with changes in mitochondrial transformation mechanisms. However, the exact mechanism of mitophagy regulation in DKD has not been elucidated. Recent advances in autophagy have renewed interest in these signaling pathways and molecules in the pathogenesis of DKD. Investigating autophagy and its associated signaling molecules may provide potential unique targets for therapeutic intervention in DKD. Increasing attention has been paid to its role in the development of various diseases such as tumors, neurological diseases, diabetes and its complications. The autophagic process mainly consists of 5 stages: initiation, elongation, formation of autophagosomes, fusion and degradation of autolysosomes.,4 Biological activity of autophagy is associated with numerous signaling pathways and regulatory factors, which are mainly divided into mTOR-dependent  and mTOR-independent signaling regulation. In recent years, with the development of epigenetic studies, more and more attention has been paid to the regulation of autophagy-related molecule expression.Autophagy, can recognize and degrade damaged macromolecular proteins, organelles, as well as invading pathogens for cellular recycling, which is a biological regulatory process that maintains cellular homeostasis. In diabetic nephropathy, excessive energy supply inhibits autophagy protection in the kidney, leading to accumulation of damaged proteins and organelles and aggravating the progression of diabetic nephropathy.,8 Also, hyperglycemia induces hyperactivation of mTOR complex 1 (mTORc1), which inhibits autophagic activity in podocytes and proximal tubular cells. However, improving autophagic activity in the kidney not only reduces the accumulation of intracellular metabolic damage products and oxidative stress in the kidney, but also improves renal extracellular matrix (ECM) deposition, inflammation and fibrosis, and blocks or delays the development of diabetic kidney disease (DKD). These data suggest that impaired autophagy may be involved in the pathogenesis of DKD, and autophagy activation is promising as a potential therapy for the treatment of DKD.Studies have shown that autophagy plays a protective role in maintaining glomerular and tubular homeostasis and is important role in human health and disease. Although an increasing number of studies have confirmed that the development of DKD is influenced by factors such as genetics, energy supply, oxidative stress as well as autophagic activity,13 and regulation of autophagy-related signaling molecules has also received increasing attention, the role of autophagy in the development of DKD remains inadequately, and more experiments are needed to further improve this field.DKD, as one of the major microvascular complications of diabetes, has become the most important component of hospitalized patients with chronic kidney disease, the pathogenesis has not been fully elucidated, and there are inadequate effective therapeutic agents to control the progression of DKD.In this review, we systematically elaborated the relationship between DKD related pathogenic mechanisms from the beginning of blood glucose and energy metabolism in DKD, and analyze the regulation of DKD pathogenic mechanisms by major autophagy-related signaling molecules, which is of great significance for the treatment of DKD via improvement renal autophagic activity. On the one hand, blood glucose entering the cell mainly generates oxygen and energy required for cellular metabolism through mitochondrial electron transport respiratory chain coupled with oxidative phosphorylation via glycolysis and tricarboxylic acid cycle pathways. On the other hand, under hormonal regulation, tissues such as liver, kidney, intestine and muscle use glucose to synthesize glycogen or adipose tissue. Finally, excess circulating glucose is filtered through the glomeruli into the tubular lumen. When the renal glucose threshold is exceeded, blood glucose is excreted in the urine and occurs glycosuria.Physiologically, it is mainly absorbed into the blood by the villi of intestine and subsequently utilization by cells after food enters the digestive tract. With the increase of blood glucose concentration, pancreatic β-cells secrete insulin and bind to the corresponding receptors on the cell surface, which regulates blood glucose metabolism and maintains the stability of blood glucose and energy. Nurit Kaiser et al found that GLUT1 protein was more abundant in smooth muscle cells compared with endothelial cells, and reduced by approximately 50% in smooth muscle cells when the glucose concentration of the medium was increased from 1.2 to 22 mmol/L for 24 hours. In addition, aldose reductase is a catalytic enzyme widely distributed in many tissues of the human body involved in the formation of glycation products. It has the highest immunological activity in the medullary part of the kidney, but its expression is very low in tissues such as the stomach, intestine, liver, spleen, and lung. Therefore, kidney, heart and other major diabetic target organs damage may be closely related to specific molecular biological characteristics in these tissues. However, understanding what pathophysiological changes occur in the kidney of diabetic hyperglycemia is particularly necessary to understand the pathological process of DKD.In general, the cell surface insulin-independent glucose transporter 1 (GLUT1) is involved in regulating intracellular and extracellular glucose transport, but different tissue and cell types have different ability to regulate intracellular and extracellular glucose. However, clinical studies have found that blocking either of the above mechanisms of action alone is not effective in blocking the progression of DM (diabetes mellitus) microangiopathy . The intermediate products of the glycolytic pathway are closely related to the formation of the above 4 pathogenesis of DKD, while a large amount of reduced NADH/FADH2 products via the tricarboxylic acid cycle enters the mitochondrial electron transport respiratory chain generate superoxide products is considered to be a common factor in the accelerated progression of the above pathomechanism.,25 Therefore, it will help to understand the overall mechanism of DKD by investigating how hyperglycemia leads to increased intracellular oxidative stress and the internal connection to the above 4 pathogenic mechanisms.In addition to oxidative stress, renal cell injury in DKD mainly includes 4 pathogenic mechanisms: activation of polyol metabolic bypass, generation of Advanced Glycation End products and activation of their receptors (AGEs-RAGEs), activation of protein kinase C (PKC), and overactivation of hexosamine bypass. However, under hyperglycemic conditions, a large amount of glucose enters the tricarboxylic acid cycle to generate a large amount of NADH and FADH2, which increase the voltage gradient on both sides of the mitochondrial inner membrane, resulting in electrons carried by CoQ are unable to be efficiently transmitted to complex III, not to oxygen molecules, leading to superoxide generation, which is degraded to hydrogen peroxide (H2O2) by superoxide dismutase from mitochondria, generates water and oxygen atoms. However, under the DM, hyperglycemia activates the polyol bypass, resulting in the consumption of large amounts of NADPH, production of superoxide dismutase (SOD) decreased, which relies on NADPH anti-oxygen free radicals and eventually intracellular reaction oxygen species (ROS) and oxidative stress increased.Physiologically, glucose enters tissue cells to successively generate ATP via the glycolytic pathway, the tricarboxylic acid cycle, and mitochondrial electron transport respiratory chain coupled with oxidative phosphorylation to provide the energy required for survival and metabolism of tissue cells. Glucose undergoes the action of aldose phosphatase to generate sorbitol, which consumes a large amount of NADPH, which reduces the synthesis of reduced glutathione that scavenges superoxide and causes an intracellular oxidation-antioxidant imbalance, resulting in increased intracellular oxidative pressure. A pervious study suggest that mitochondrial DNA damage is likely to occur with increased superoxide in mitochondria and resulting in activating poly (ADP-ribose) polymerase required for DNA repair, although the activation of this enzyme has a certain positive effect on mitochondrial DNA repair, it also inhibits glyceraldehyde 3-phosphate dehydrogenase activity like hyperglycemia, reduces the reaction rate of the glycolytic pathway, and aggravates the development of the pathogenic mechanisms of DKD. However, another study showed that hyperglycemia did not increase in production of ROS when the voltage gradient on the mitochondrial membrane was disrupted by uncoupling protein 1 (UCP-1) or generated oxygen radicals were degraded by manganese superoxide dismutase (MnSOD). Thus, oxidative stress resulting from hyperglycemia is thought to be an upstream signaling pathway common to pathogenic mechanisms.Multiple pathogenic mechanisms of DKD originate from intermediates in glucose glycolysis, and oxidative stress resulting from hyperglycemia contributes to the development of the above 4 pathogenic mechanisms of DKD. Physiologically, glyceraldehyde 3-phosphate generates glycerate 1,3 diphosphate under the action of its dehydrogenase, following continues glycolysis and enters the tricarboxylic acid cycle, but hyperglycemia inhibits the activity of glyceraldehyde 3-phosphate dehydrogenase, resulting in accumulation of large amounts of prophase glycolytic products, which leads to polyol bypass activation.Oxidative stress and the above 4 pathogenic mechanisms lead to renal injury mainly via 2 ways. The first is through affecting multiple balance systems, such as oxidation-antioxidant balance, protein homeostasis and mitochondrial quality control, the second is through regulating the gene transcription and translation processes of intracellular DKD-related pathogenic molecules, such as PKC activation and hexosamine pathway hyperactivation. Under the regulation of NADPH/NADP+, glutataione (GSH) and cysteine (Cys) undergo the interconversion of oxidative and reduced states, so they can be continuously activated and inactivated according to the desired state, so reduced glutathione continuously acts as an electron donor to reduce H2O2 to water and maintaining intracellular oxidative balance.,33 However, due to the inhibitory effect of hyperglycemia and oxidative stress on glyceraldehyde 3-phosphate dehydrogenase in glycolysis, the polyol bypass pathway is activated, which not only consumes a large amount of NADPH, but also reduces the production of reduced glutathione, fails to remove a large amount of superoxide in time, which relies on NADPH, resulting in aggravating intracellular oxidative damage.Hyperglycemia induced glucose metabolism disorders are the main cause of massive generation of superoxide and increased oxidative stress in the kidney. In order to reduce the damage of oxidative stress to cells, the body initiate antioxidant defense systems to scavenge free radicals.,36 In order to maintain intracellular proteostasis, the cell itself initiates a series of mechanisms to maintain proteostasis, and the proteasome system is the most important intracellular protein degradation mechanism . It catalyzes the degradation of proteins that are no longer needed, damaged, or even weakened by the cell itself in an ATP-dependent manner by recognizing and combining hydrophobic structures exposed after protein damage.,38 In addition, to prevent oxidatively damaged proteins from accumulating during mild oxidative stress, chaperone heat shock proteins refold damaged proteins by recognizing and binding exposed hydrophobic protein sequences, or leave unfolded proteins in a dissolved state to avoid forming multimers with other damaged proteins.,40Unlike the reversible redox reactions mentioned above, protein carbonylation is a non-enzymatic protein oxidation, which is regarded as a marker of severe chronic oxidative damage due to causing irreversible damage to proteins.,41 There is a study about mitochondrial quality control in vitro showed that when mitochondria are damaged, PINK1 exposure on the outer membrane surface increases, where it can activate the ubiquitin ligase of parkin, ubiquitinates the mitochondrial membrane surface protein (Lys63), and binds to the adaptor protein P62 of autophagy, meanwhile it binds to ATG8 on the autophagic vacuole membrane through the microtubule associated protein light chain 3 interacting region (LIR), then promotes recruitment of ubiquitin binding mitophagy receptors to promote capture by the autophagosome. Newly formed autophagic vacuoles firstly associate with acidified endosomes to form autophagosomes and then fuse with lysosomes to form autolysosomes. Thus, damaged organelles or biomacromolecules are degradated to nucleotide fragments and fatty acids, which is not only maintains intracellular proteostasis, but also releases degradation products into the cytoplasm to provide raw materials for new biosynthesis. In the DKD state, renal autophagy activity is inhibited, resulting in increased accumulation of injured mitochondria, which further aggravates intracellular oxidative stress and renal structural and functional impairment. In addition, it has been reported that increased PINK1 protein is also able to activate peroxisome proliferator-activator receptor gamma coactivator 1α (PGC-1α) of the main regenerative regulatory molecule with promoting autophagy, following activates downstream nuclear respiratory factor (NRF) and mitochondrial transcription factor A (TFAM), to synthesizes new mitochondria to maintain the quantity and quality stability of mitochondria. Thereby, PGC-1α expression in the kidney is significantly downregulated in the DKD state, resulting in reduced mitochondrial production, and reduced synthesis of important proteins such as ATPase in injured mitochondria, insufficient ATP supply as well as caused impaired energy supply in the DKD, which are also important factors which aggravates structural changes and functional impairment in the kidney.Mitochondria is not only the starting point of oxidative stress, but also the main target organelle of oxidative damage and the repair, regeneration and autophagic degradation of mitochondria to maintain the quality control of mitochondria. It can also promote the expression of collagen fibers, proinflammatory factors and accelerate renal fibrosis through transcription factor β, plasminogen activator inhibitor 1 (PAI-1) and nuclear transcription factor-κB (NF-κB). In diabetic Klotho deficiency mice, the expression of PKC-α and p66SHC was upregulated and subsequently promoted the generation of ROS, resulting in podocyte injury and aggravating proteinuria levels. So, PKCα/p66SHC may play a role in mediated podocyte injury in diabetic nephropathy.PKC activation and increased oxidative stress can regulate the expression of a variety of DKD related pathogenic genes, such as downregulation the expression of nitric oxide synthase (NOS) of the vascular endothelial relaxing factor and upregulation the expression of endothelin 1 of the vascular endothelial contractile factor to reduce renal blood flow and improve renal hemodynamics.Hyperactivation of the hexosamine pathway culminates in the formation of uridine diphosphate and N-acetylglucosamine, the latter inhibits the phosphorylation of Akt/eNOS and HSP72 through kinase-like effects of serine/threonine phosphorylation, lead to increase the expression of transforming growth factor-β (TGF-β) and PAI-1, and promote oxidative stress and fibrosis in the DKD. It has been found that the mononuclear phagocyte system is activated in DM, releasing cytokines and recruiting, ultimately leading to inflammation-related structural changes. In addition, mast cells are capable of infiltrating the tubulointerstitium and releasing inflammatory mediators and proteolytic enzymes, which may be associated with decreased glomerular filtration rate (eGFR).Increasing evidence from clinical and experimental studies suggested that inflammation play a critical role in the development and progression of DKD, such as macrophages, and inflammatory cytokines, nuclear factor κB (NF-κB), Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathways. In models of DN, renal expression of IL-1 increases is related to subsequent expression of chemotactic factors. Another study also showed that IL-1 directly increases vascular endothelial cell permeability. Nosadini et al reported that IL-6 can promote neutrophil infiltration into tubulointerstitium, affecting ECM dynamics, and promoting overall renal hypertrophy, glomerular basement membrane thickening, which is associated with albuminuria. TNF-α is capable of inducing and differentiating inflammatory cells, cytotoxicity to renal cells, activating apoptosis, altering glomerular hemodynamics, increasing vascular endothelial permeability, and oxidative stress. It has been shown that TNF-α mRNA expression levels are elevated in glomerular and tubular cells during the early stages of diabetes. In db/db mice, caspase inhibitors reduced renal CASP1, IL-1β, IL-18, and NLRP3 inflammasome activation and ameliorated albuminuria and renal ECM accumulation.Cytokines are a group of polypeptide signaling molecules. In the kidney, different kidney cells can synthesize inflammatory cytokines, such as IL-1, IL-6, IL-18, and TNF-α, all of which are different extent involved in the pathogenesis of DKD. Cytokines can regulate cell activation, proliferation, recruitment, migration, and differentiation by activating this fundamental mechanism. It has already been reported that JAK/STAT was upregulated in glomerular from patients with early DKD and tubulointerstitial expression of various JAK and STAT isoforms increases with disease progression and is inversely correlated with eGFR. NF-kB is a key transcription factor activated by cytokines and oxygen radicals during renal inflammation in diabetes and is activated through JAKs/STATs, leading to the structural alterations and functional abnormalities in DKD. In renal cells, NF-kB is rapidly activated by multiple stimuli, including hyperglycemia, AGEs.JAK/STAT is an intracellular cytokine related signaling pathway that plays an important role in mediating paracrine stimulation and nuclear receptors. Hyperglycemia and oxidative stress increase AGEs and RAGEs production, resulting in a rapidly increase in oxidative stress and NF-κB expression in endothelial cells, which not only promotes adhesion molecule transcription, but also promotes glomerular epithelial cell differentiation into interstitial cells, reduces NOS activity, and accelerates renal vasoconstrictor dysfunction and vascular sclerosis. In addition, it has also been suggested that AGE diffusing out of cells and its precursors damage albumin in the circulation and activate the transcription and secretion of systemic inflammatory mediators.,65 Although no significant benefit has been found in DKD-III disease patients with anti-AGE agents in clinical trials, first-line drugs such as metformin for the treatment of DM/DKD, were shown to be able to reduce tubulointerstitial injury by activating AMP-activated protein kinase (AMPK), blocking the AGE-RAGE axis, and reducing the production of ROS and matrix metalloproteinase 2.–69The kidney has been found to be the earliest organ of AGEs injury in diabetes, meanwhile is also the main organ of AGEs filtration clearance.Of course, these modes of action are not isolated, and they tend to synergize to promote the progression of DKD. The key to the generation and aggravation of hyperglycemia and oxidative stress is to lead to metabolic abnormalities in vivo, while autophagy, as a major catabolic pathway, is involved in the degradation and recycling of macromolecules and damaged organelles to maintain intracellular homeostasis, leading to hypothesize that autophagy plays an important role in the development and progression of diabetic nephropathy and is a promising treatment option.–73 It has been found that these signaling molecules are involved in multiple links in the development of type 2 diabetes as well as diabetic nephropathy.mTOR, AMPK and NAD-dependent deacetylase sirtuin-1 (SIRT1) are an important regulator regulating mitochondrial function and autophagic activity.,75 The core complex of mTORC1 consists of mTOR, regulatory protein with mTOR, and mLST8 protein ,,77 which regulate cell growth mainly by promoting translation, ribosome biogenesis to inhibit intracellular autophagic activity. mTOR, as a major regulator of autophagy, is regulated by multiple upstream signaling pathways to directly or indirectly regulate related gene expression or protein modification.,80mTOR belongs to the PI3K-related protein kinase family and is a serine/threonine protein kinase, which consists of mTORC1 and mTORC2, and its activity correlates with intracellular nutrient levels and redox status. causing inhibition of glucose uptake and glycogen synthesis. Sakaguchi et al found that mTOR activation was induced by hyperglycemia was closely associated with proliferation and apoptosis of tubular cells in diabetic nephropathy, while tubular injury was ameliorated after knocking down the mTOR gene in proximal tubular cells.,84 Another study also showed that rapamycin, as a mTOR inhibitor, was not only able to increase blood glucose uptake by 17% and improve insulin resistance, but also significantly prolong the survival time of species. In addition, rapamycin is also able to reduce glomerular injury via multiple ways, such as improving glomerular basement membrane thickness, tubular epithelial transdifferentiation to mesenchymal cells, macrophage recruitment, reducing proteinuria, as well as improving renal autophagic activity.It has been found that a high-fat diet can overactivated mTORC1 and inhibit phosphorylation at the serine site of insulin receptor substrate 1 (IRS-1 Ser312 and Ser636 sites), thereby increasing insulin resistance in vivo,,87 Watanabe et al reported that inhibition of SIRT1 leads to activation of the mTOR pathway and decreases AMPK activation, activate autophagy-related proteins such as Atg5 by deacetylation, which promotes autophagic activity. In addition, sirt1 is also able to promote the synthesis of autophagosomes and lysosomes through activating the PINK1/parkin pathway, enhancing intracellular autophagy levels. Therefore, sirt1 may promote autophagy levels in different cells by regulating multiple links associated with autophagy.SIRT 1 is a member of the Sirtuins family of NAD-dependent deacetylases in mammals, and it is able to deacetylate a variety of substrate proteins in the presence of nicotinamide adenine dinucleotide (NAD+) and is involved in the repair process of multiple cell injuries such as anti-oxidative stress, autophagic activity and anti-aging, thereby improving multiple pathogenic mechanisms of DM/DKD.,90 It has been found that resveratrol, a SIRT1 agonist, can enhance the expression of SIRT1, not only improve blood glucose homeostasis and insulin resistance, promote mitochondrial regeneration, but also reduce mesangial cell proliferation, improve renal autophagy activity and reduce inflammation as well as reduce oxidative stress, play a role in the treatment of diabetic nephropathy.,92 In addition, in response to fasting, SIRT1 not only enhances gluconeogenesis and inhibits glycolysis by interacting with PGC-1α, FOXO 1, CRTC2, but also maintains energy supply and blood glucose stability through the regulation of PGC-1α and peroxisome proliferator activated receptor-α (PPAR-α), which promotes fatty acid oxidation, hepatic glucose output and gluconeogenesis.The expression level of SIRT1 protein is closely related to the development of diabetic nephropathy as well as hyperglycemic status. In STZ-induced and db/db diabetic kidneys, Sirt1 expression significantly decreases, which maybe due to Sirt1 activity is strictly regulated by intracellular NAD + concentrations, which are likely to decrease in diabetic organs. is highly expressed in various kidney cells. In diabetes experimental models, the expression of AMPK was downregulated and phosphorylation levels of AMPK were also significantly reduced in glomerular epithelial cells, while improving expression levels of AMPK has been found to restore energy homeostasis and improve insulin resistance. In addition, AMPK also plays a role in the treatment of DKD by improving renal filtration barrier injury and autophagic activity, reducing ECM deposition and renal fibrosis.,99AMPK is a member of serine/threonine protein kinase family, which consists of 3 subunits, a catalytic subunit α and 2 regulatory subunits β and γ and it is biologically active after the threonine 172 of its α subunit is phosphorylated, When the utilization rate of blood glucose decreases, ATP synthesis decreases, while AMP increases, increased AMP binds and activates AMPK, following serine at positions 1345 of tumor suppressor (TSC2) is phosphorylated by activated AMPK and has GTPase activity, leading to GTP hydrolyze to GDP, which weakens the binding of GTP-dependent Rheb to mTOR molecules, exerting the effect of inhibiting mTOR, thereby enhancing the autophagic activity of cells. Another study also showed that GSK3 phosphorylated TSC2 only when TSC2 had been previously phosphorylated by AMPK, whereas mutation of the AMPK site S1345A in TSC2 completely eliminated GSK3 phosphorylation, demonstrating that AMPK-priming phosphorylation was required for subsequent GSK3 phosphorylation, eventually inhibits mTORC1 expression. Recently, it has been found that AMPK is able to directly phosphorylate the raptor subunit of mTORC1 as predicted by tandem mass spectrometry and TSC2 knockdown analysis, thereby directly exerting an inhibitory effect on mTOR.AMPK is also a major sensor protein of energy status in eukaryotic cells and is able to inhibit mTOR and reduce protein synthesis according to changes in intracellular energy, thereby preferentially ensuring the energy supply of cells.In summary, there are also complex interaction networks between these autophagy-related signaling molecules, which are jointly involved in the regulation of multiple pathogenic factors in diabetic nephropathy. Current ample research evidence supports that multiple DM vascular complications, including DKD, can be ameliorated by modulating these signaling molecules. In diabetic conditions, altered expression of these stress-stimulated autophagy molecules may be beneficial in improving organelle dysfunction and subsequent worsening of diabetic nephropathy. Therefore, we provide a systematic review of the therapeutic effects of autophagy on diabetic nephropathy to help future research in this area.Writing – original draft: Peirong Zhang, Jiawei Yu, Yan Liu, Hongjie Li.Writing – review & editing: Peirong Zhang, Jiawei Yu.


Cells use actin-based protrusions not only to migrate, but also to sample their environment and take up liquids and particles, including nutrients, antigens and pathogens. Lamellipodia are sheet-like actin-based protrusions involved in sensing the substratum and directing cell migration. Related structures, macropinocytic cups, arise from lamellipodia ruffles and can take in large gulps of the surrounding medium. How cells regulate the balance between using lamellipodia for migration and macropinocytosis is not yet well understood. We recently identified CYRI proteins as RAC1-binding regulators of the dynamics of lamellipodia and macropinocytic events. This review discusses recent advances in our understanding of how cells regulate the balance between eating and walking by repurposing their actin cytoskeletons in response to environmental cues. Actin-based protrusions at the plasma membrane allow the cell to explore space in all directions and to make new contacts with or even engulf samples of extracellular substances. By extending itself, the cell can actively pull and push against extracellular barriers to allow movement or it can take in nutrients to fuel its activity. The main machinery enabling actin-based protrusion at the plasma membrane is the 5-subunit Scar/WAVE complex . This complex interfaces with the 7-subunit Arp2/3 complex to generate branched actin filament structures that are mechanoresponsive and capable of force generation. Arp2/3 is activated by WRC in the presence of the active small GTPase RAC1 and by interaction with actin filaments to create a burst of dendritic actin filament branches that push against the plasma membrane, resulting in sheet-like extensions, termed lamellipodia. RAC1, WRC and Arp2/3 form a feedback loop to sustain dynamic actin reorganisation, which is orchestrated by many other signalling and actin-interacting proteins. We recently described negative regulators of this feedback loop, CYRI proteins, which also interact with RAC1 and display plasma membrane localisation through a myristoyl lipid anchor on their N-terminus [Related to lamellipodia are membrane ruffles, which occur when a lamellipodium lifts off the substratum. Ruffles can morph into cup-shaped structures that take up large gulps of extracellular fluid in a process called macropinocytosis. Macropinocytosis is mediated by large (0.5–10 μm) membrane cups that collapse into vesicles and bud into the cytoplasm from the plasma membrane. Macropinocytic structures are considerably larger than cups or pits formed in other types of endocytosis, including clathrin and caveolin-mediated endocytosis, which take place on the sub-micrometer scale (reviewed in ). MacropMultiple types of cells perform macropinocytosis, including amoebas, cancer cells, immune cells, endothelial cells and mesenchymal cells. Endothelial cells can also perform stimulated macropinocytosis during angiogenesis, as vascular endothelial growth factor (VEGF) stimulates macropinocytosis of its own receptor, the VEGFR . EpithelIt can be helpful to think of macropinocytosis as a series of stages, to place molecular events into the order in which they occur and to determine the function of the various cellular machinery employed see .Protrusion — Initiation of macropinocytosis begins with the protrusion of a membrane ruffle driven by WRC and Arp2/3-mediated actin assembly . ProtrusDrosophila neural development [Closure of the cup — Cup closure involves the fusion of the extended membrane into a vesicle or series of vesicles that are then taken into the cell. This requires remodelling and disassembly of the actin structures and is accompanied a transient increase in CYRI-A followed by a decrease in RAC1 signal at the membrane of the nascent macropinosome ,17. Bothelopment ,19.Engulfment of the macropinosome — Stenmark and colleagues describe two main stages for macropinosome engulfment into mammalian cells, with the first being a closed vesicle that is highly deformed by the cortical actin network. The vesicle eventually squeezes through the actin network and becomes rounded as it traverses deeper into the cytoplasm ,21. The Movement into the cytoplasm — After capture by microtubules that penetrate through the cell cortex, macropinosomes traverse through the dense actin network and deeper into the cell in a dynein- and microtubule-dependent manner . JIP3 anFusion with lysosomes — Finally, the macropinosomes fuse with other endocytic organelles and eventually with lysosomes in a process mediated by phosphoinositide lipids and their contents are broken down into basic chemical building blocks to allow the cell to use the energy from proteins, lipids and sugars thus engulfed (reviewed in ).Perhaps the most well-understood function of macropinocytosis is nutrient uptake. Macropinocytosis allows cells to use alternative and larger-sized nutrients including lipids, proteins and cell fragments. This function is well known to fuel cancer growth (reviewed in ), as tumDictyostelium, where PtdIns3-kinase drives the formation of macropinocytic cups that generally oppose migration and fuel the axenic growth of cells [Dictyostelium normally feed on bacteria and as such prefer solid growth substrata. However, common laboratory strains readily grow axenically in liquid culture. Recently, the secret to survival in liquid medium was described as an activating mutation in the RAS GAP, NF1, in common laboratory strains [Dictyostelium RAS strongly localises to the centre of macropinocytic cups in these axenic strains, in a zone that is PtdIns3-rich. NF1 is proposed to restrict the size and frequency of initiation of such zones by controlling RAS activity [Macropinocytosis is also connected with cell migration, both directly via actin dynamics and indirectly via receptor trafficking. The best-understood example is in of cells ,13. Dict strains . Dictyosactivity  and mutaDictyostelium amoebas use separate structures for macropinocytosis and migration and that these can work in opposition [Dictyostelium, but it might be due to the repurposing of branched actin filaments away from lamellipodia and towards macropinosomes. Arp2/3 complex may simply become limiting for making new branched actin, or even actin itself may be limiting, as is found in budding yeast, where actin cables and actin patches play an opposing role limited by the availability of actin and actin-binding proteins [position ,25. It iproteins . Anotherproteins ,14, suggEvidence is building that macropinocytosis is an important controller of membrane trafficking for certain cell surface proteins and receptors. We recently found that disabling macropinocytosis by depletion of CYRI proteins led to enhanced surface integrin accumulation, enhancing invasiveness and adhesion of cancer cells . IntegriXenopus embryo endoderm cells, which has been termed ingression-type migration [Another major function of macropinocytosis is the rapid regulation of membrane surface area. Dendritic cells faced with navigation of narrow spaces will rapidly macropinocytose membrane to allow squeezing through tight places . The triigration . MultiplCYRI proteins are evolutionarily conserved proteins that directly interact with RAC1 and oppose RAC1-mediated activation of WRC  Figure . This inWe recently discovered that CYRI proteins are key controllers of macropinocytosis . The sigDictyostelium, the presence of PtdIns 3,4,5 P3 may distinguish macropinocytic cups from lamellipodia protrusions [Could CYRI proteins be coincidence detectors of RAC1 and a lipid at the plasma membrane surface? This could explain the differential recruitment of CYRI-A and CYRI-B. The proteins and lipids that define macropinocytic cups and lamellipodia are largely overlapping. However, in trusions ,12,13,37Salmonella, which enter using actin-based protrusions [CYRI proteins participate in enhancing lamellipodia dynamics and macropinocytosis, but do they also regulate other forms of plasma membrane-mediated cellular engulfment — e.g. microendocytosis or phagocytosis? Phagocytosis is a likely candidate, as CYRI seems to offer cells protection against the uptake of certain pathogens such as trusions . Evidenctrusions , but morCYRI proteins may have evolved to protect cells against the low-level engagement of RAC1-mediated ruffling, such as induced by contact with some pathogens or foreign particles. By having a buffer for RAC1-mediated protrusions, CYRI makes cell membranes more dynamic and more resistant to stimulation. This perhaps suggests a complex role for CYRI in the immune system, as it could be protective for pathogen entry, but if it has a positive role in the resolution of macropinocytosis, it could also promote pathogen entry via macropinocytosis.In summary, CYRI proteins increase cell membrane dynamics and thus shorten the lifespan of protrusions, while allowing cells to make crucial decisions about whether to use their actin cytoskeleton to migrate or to take samples of the environment. CYRI proteins sit at the centre of the eat vs walk decision and future research will hopefully reveal new mechanisms and connections between CYRI proteins and the cellular machinery controlling these processes. CYRI is clearly only one small player in a complex web of feedback loops controlling the cytoskeletal and membrane changes taking place during lamellipodia and macropinocytic cup dynamics. However, the study of CYRI holds promise to reveal new aspects of these processes.Gaining a better understanding of how cells control the balance between the assembly of lamellipodia for migration or for macropinocytosis is fundamentally important for understanding how cells balance energy-consuming processes, such as migration, with energy uptake and production. It also can potentially provide insights into how to control these processes or exploit them for therapeutic purposes. Delivery of nanoparticle drugs via macropinocytosis might provide enhanced targeting of chemotherapeutics to cancer cells (reviewed in ) and theEven though macropinocytosis was first described in the 1930s (reviewed in ), the fiFuture research should aim to identify the common basic principles and control mechanisms that are conserved and fundamental in macropinocytosis. Additionally, if we better understand the specialisations related to different cancer mutations, cell types, signalling or environmental cues, we have a chance to uncover unique opportunities to understand or exploit macropinocytosis and the eat vs walk machinery to combat cancer, pathogens or other diseases.