Mixture of five herbal extracts ameliorates pioglitazone-induced aggravation of hepatic steatosis via activating the adiponectin receptor 2/AMP-activated protein kinase signal pathway in diabetic KKAy mice

Abstract

Objective: To assess the effect of a mixture of five herbal extracts (FT-5) on insulin resistance, glucose/lipid metabolism, hepatic steatosis, and to investigate whether the combination of FT-5 and pioglitazone would provide a robust effect on diabetes treatment, while may minimize undesirable side-effects of pioglitazone in diabetic Ay gene (KKAy) mice.

Methods: Seven-week-old KKAy mice were randomly divided into five groups: control (CON) group, FT-5 (2.0 g/kg) group, pioglitazone (20 mg/kg) (PIO) group, pioglitazone (20 mg/kg) + FT-5 (2.0 g/kg) (P + F) group. Age-matched C57BL/6J mice were used as the control group. After seven weeks of continuous intragastric administration of medication, the glucose metabolism, insulin sensitivity and lipid metabolism of KKAy mice were evaluated by assessing the fasting blood glucose (FBG), oral glucose tolerance test (OGTT), fasting serum insulin (FINS), insulin tolerance test (ITT), homeostasis model of assessment-insulin resistance index (HOMA-IR), total cholesterol (TC), total triglycerides (TG), and free fatty acids (FFA) in plasma and liver. Plasma and hepatic adiponectin were measured via enzyme-linked immunosorbent assays. Genes related to adipogenesis and lipolysis in white adipose tissues (WAT) and liver were examined by real-time polymerase chain reaction. Lipid metabolism-related protein expression in the liver of KKAy mice were detected by Western blotting.

Results: PIO treatment remarkably improved insulin resistance. However, it also showed substantial side effects. FT-5 group exhibited no significant decrease in serum glucose. However, it reduced fasting plasma TG levels and improved hepatic steatosis of KKAy mice. P + F group showed improved insulin resistance and similar body weight gain, as compared with control group. The mRNA expression of genes related to fatty acid oxidation was markedly up-regulated in the liver of P + F group. Pioglitazone administration markedly decreased the phosphorylation levels of AMPK, as compared with all other groups. Besides, even though plasma adiponectin increased in PIO, FT-5, P + F group, adipoR2 gene expression significantly decreased in the liver of PIO group.

Conclusion: FT-5 decreased plasma TG and alleviated aggravating hepatic steatosis induced by pioglitazone in KKAy mice. FT-5's mechanism might be associated with its ability to activate the AdipoR2/AMPK pathway.

Keywords: AMP-activated protein kinases; FT-5; Hepatic steatosis; KKAy mice; Pioglitazone; Insulin resistance.