Edible plants such as sweet potato are sources of natural antioxidants that can be exploited in the management and treatment of insulin resistance. This present study investigated the effects of the extracts of an orange-fleshed sweet potato on oxidative stress biomarkers (glutathione status and lipid peroxidation) and activities of antioxidant enzymes (catalase, CAT and glutathione peroxidase, GPx) in palmitate-induced insulin resistant C2C12 cells. The intracellular antioxidant status of the cells was also measured using Ferric reducing antioxidant power (FRAP) and Trolox equivalent antioxidant capacity (TEAC) assays. Furthermore, this study determined the effect of the extracts on the regulation of some type 2 diabetes associated genes; glucose transporter 4 (glut4), Nuclear respiratory factor 1 (nrf1), Myocyte enhanced factor 2A (mef2a), Carnitine palmitoyltransferase 1 (cpt1) and Acetyl-CoA carboxylase 2 (acc2). The results showed a significant (p < 0.05) increase in intracellular GSH level, a significant reduction in the level of malonaldehyde and a significant improvement in the intracellular antioxidant status upon treatment of the insulin resistant cells with the extracts. The extracts were also able to positively modulate the expression levels of the type 2 diabetes associated genes. On the other hand, HPLC-MS analysis of the extracts showed the presence of polyphenols which could have contributed to the bioactivity of the extracts through their antioxidant effects.
Keywords: diabetes; glutathione; insulin resistance; malonaldehyde; oxidative stress; palmitate.