Quercetin and d-chiro-inositol combined alleviate hepatic insulin resistance

The hypoglycemic effects and underlying molecular mechanisms of combining two dietary compounds, quercetin (Que) and d-chiro-inositol (DCI) on hepatic insulin resistance in C57BL/6J mice that were fed a high fat diet and saturated palmitic acid (PA)-treated hepatocytes were studied. Catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) are important antioxidant enzymes . Insufficient secretion of these enzymes will inhibit the normal phosphorylation of insulin receptors in the liver, thereby limiting the transmission of insulin signals and producing insulin resistance. The results showed that QD (both Que and DCI) led to the recovery of the activity of CAT, SOD, GPx, suggesting that QD was helpful in preventing mice hepatic insulin resistance. In PA-induced human hepatoma cells (HepG2), QD improved the antioxidant level in cells. The fluoro-immunoassay showed that QD effectively reduced the translocation of protein kinase Cε to cell membranes in the HepG2. Western blotting results suggested that QD increased the signal transduction in the IRS-2/PI3K/Akt/FoxO1 pathway. Overall, these results showed that the combination of 5 μmol Que and 5 μmol DCI ameliorated high fat diet-induced hepatic insulin resistance.