Berberine Ameliorates Hepatic Insulin Resistance by Regulating microRNA-146b/SIRT1 Pathway

Objective: Hepatic insulin resistance is a major initiating factor for type 2 diabetes mellitus. In previous study, Gegen Qinlian Decoction containing berberine could enhance hepatic insulin sensitivity by SIRT1-dependent deacetylation of FOXO1. However, it is not clear whether berberine also can improve hepatic insulin sensitivity by SIRT1/FOXO1 pathway. This study aimed to evaluate the efficacy of berberine for improving hepatic insulin resistance and the possible molecular mechanisms involved. Methods: In vitro, HepG2 cells were induced with palmitic acid, and glycogen synthesis was examined. In vivo, a high-fat diet (HFD)-fed mouse model was established, and metabolic parameters were assessed. The expressions of miR-146b and sirtuin 1 (SIRT1) in liver were also examined. The relationship between miR-146b and SIRT1 was examined by the dual-luciferase reporter gene assay. Results: Serum biochemical parameters, such as glucose and HOMA-IR index, were increased in HFD mice; miR-146b and SIRT1 were abnormally expressed in HFD mice and palmitic acid-treated HepG2 cells. Interestingly, berberine reduced body weight and caused a significant improvement in glucose tolerance and HOMA-IR index without altering food intake in mice. Overexpression of miR-146b abolished the protective effect of berberine on palmitic acid-induced impaired glycogen synthesis in HepG2 cells. Luciferase assay showed that miR-146b directly targeted SIRT1. Conclusion: The present findings suggest that berberine could attenuate hepatic insulin resistance through the miR-146b/SIRT1 pathway, which may represent a potential therapeutic target for the prevention and treatment of metabolic diseases, particularly diabetes.