Insulin signaling pathway assessment by enhancing antioxidant activity due to morin using in vitro rat skeletal muscle L6 myotubes cells.
BACKGROUND
Plant-derived phytochemicals such as flavonoids have been explored to be powerful antioxidants that protect against oxidative stress-related diseases. In the present study, Morin, a flavonoid compound was studied for its antioxidant and antidiabetic properties in relation to oxidative stress in insulin resistant models conducted in rat skeletal muscle L6 cell line model.


METHODS
Evaluation of antioxidant property of morin was assayed using in vitro methods such as cell viability by MTT assay, estimation of SOD and CAT activity and NO scavenging activity. The anti-oxidative nature of morin on L6 cell line was conducted by the DCF-DA fluorescent activity. Glucose uptake in morin treated L6 myotubes are accessed by 2-NBDG assay in the presence or absence of IRTK and PI3K inhibitors. Further glycogen content estimation due to the morin treatment in L6 myotubes was performed. Antioxidant and insulin signaling pathway gene expression was examined over RT-PCR analysis.


RESULTS
Morin has a negligible cytotoxic effect at doses of 20, 40, 60, 80, and 100 µM concentration according to cell viability assay. Morin revealed that the levels of the antioxidant enzymes SOD and CAT in L6 myotubes had increased. When the cells were subjected to the nitro blue tetrazolium assay, morin lowered reactive oxygen species (ROS) formation at 60 µM concentration displaying 39% ROS generation in oxidative stress condition. Lesser NO activity and a drop in green fluorescence emission in the DCFDA assay, demonstrating its anti-oxidative nature by reducing ROS formation in vitro. Glucose uptake by the L6 myotube cells using 2-NBDG, and with IRTK and PI3K inhibitors (genistein and wortmannin) showed a significant increase in glucose uptake by the cells which shows the up regulated GLUT-4 movement from intracellular pool to the plasma membrane. Morin (60 µM) significantly enhanced the expression of antioxidant genes GPx, GST and GCS as well as insulin signalling genes IRTK, IRS-1, PI3K, GLUT-4, GSK-3β and GS in L6 myotubes treated cells.


CONCLUSION
Morin has the ability to act as an anti-oxidant by lowering ROS levels and demonstrating insulin mimetic activity by reversing insulin resistance associated with oxidative stress.
['Issac|Praveen Kumar|PK|http://orcid.org/0000-0003-3007-8792', 'Karan|Rupmanjari|R|', 'Guru|Ajay|A|http://orcid.org/0000-0002-8583-9352', 'Pachaiappan|R|R|', 'Arasu|Mariadhas Valan|MV|http://orcid.org/0000-0001-5898-2121', 'Al-Dhabi|Naif Abdullah|NA|http://orcid.org/0000-0002-2663-6328', 'Choi|Ki Choon|KC|', 'Harikrishnan|Ramasamy|R|http://orcid.org/0000-0002-4807-758X', 'Raj|Jesu Arockia|JA|http://orcid.org/0000-0002-0240-7141']
Antioxidant Morin Skeletal muscle L6 myotubes Glucose uptake Insulin mimic