Fenugreek is a well known annual herb widely used in both medicine and food. Four flavonoid glycosides have been separated from fenugreek seeds in our previous study. In this study, the effects of the four flavonoid glycosides on regulating glycolipid metabolism and improving mitochondrial function were investigated. Isoorientin showed a very significant activity among these flavonoid glycosides. First, isoorientin decreased the accumulation of lipid droplets in 3T3-L1 preadipocytes by reducing the expression of adipokines including PPARγ, C/EBPα, and FAS. Second, isoorientin restored insulin-stimulated glucose uptake in dexamethasone-induced insulin-resistant 3T3-L1 adipocytes by reactivating Akt and AMPK. Finally, isoorientin improved mitochondrial dysfunction induced by dexamethasone in 3T3-L1 adipocytes. Isoorientin also reversed dexamethasone-induced decrease in mitochondrial membrane potential (MMP) and intracellular ATP production, reduced accumulation of intracellular reactive oxygen species (ROS), and protected mitochondrial DNA (mtDNA) from oxidative damage. At the same time, mitochondrial biogenesis is promoted. Therefore, isoorientin may be an attractive candidate as a glucose-lowering and insulin-resistance-improving agent for the treatment of diabetes.
Keywords: 3T3-L1 adipocytes; fenugreek seeds; flavonoid glycosides; insulin resistance; isoorientin; mitochondrial function.