Effects of detraining and retraining on muscle energy-sensing network and meteorin-like levels in obese mice.
BACKGROUND
Increased intramuscular peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) with exercise directly or indirectly affects other tissues, but the effector pathway of PGC-1α has not been clearly elucidated. The purpose of this study was to investigate the effect of exercise and/or dietary change on the protein levels of the soleus muscle energy-sensing network and meteorin-like (Metrnl), and additionally to analyze the detraining and retraining effects in high-fat diet (HFD)-induced obese mice.


METHODS
One hundred male C57BL/6 mice were divided into normal-diet + sedentary (CO, n = 20) and HFD + sedentary (HF, n = 80) groups, and obesity was induced in the HF group through consumption of a 45% HFD for 6 weeks. The HF group was subdivided into HF only (n = 20), HF + training (HFT, n = 20), dietary change + sedentary (HFND, n = 20), and HFND + training (HFNDT, n = 20) groups, and the mice in the training groups underwent a treadmill training for 8 weeks, 5 times per week, 40 min per day. The HFT and HFNDT groups underwent 8-week training, 8-week detraining, and 4-week retraining.


RESULTS
An 8-week training was effective in increasing the protein levels of soleus muscle AMP-activated protein kinase (AMPK), PGC-1α, and plasma Metrnl in the obese mice (P < 0.05). Moreover, exercise in obesity reduced body weight (P < 0.05), and exercise with dietary conversion was effective in reducing body weight (P < 0.05) and fat mass (P < 0.05) after 8-week training. 8-week detraining restored the increased protein level to the pre-exercise state, but, the previous exercise effect in body weight and fat mass (P < 0.05) of the HFNDT group remained until the end of 4-week detraining. 4-week retraining was effective in increasing the protein levels of soleus muscle AMPK, PGC-1α, blood Metrnl (P < 0.05), and reducing in body weight (P < 0.05) and fat mass (P < 0.05), when retraining with dietary change.


CONCLUSIONS
The results of this study suggest that regular exercise is indispensable to reduce body weight and fat mass through upregulation of the muscle energy-sensing network and Metrnl protein levels, and retraining with dietary change is necessary to obtain the retraining effects more quickly.
['Bae|Ju Yong|JY|', 'Woo|Jinhee|J|', 'Kang|Sunghwun|S|', 'Shin|Ki Ok|KO|']
D055372:AMP-Activated Protein Kinases D000273:Adipose Tissue D000818:Animals D059305:Diet, High-Fat D005786:Gene Expression Regulation D008297:Male D051379:Mice D008810:Mice, Inbred C57BL D008820:Mice, Obese D009043:Motor Activity D018482:Muscle, Skeletal D009414:Nerve Growth Factors D009765:Obesity D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha D010805:Physical Conditioning, Animal D057185:Sedentary Behavior D056564:Sirtuin 1
Detraining Retraining Meteorin-like PGC-1α AMPK SIRT-1