Berberine Attenuates Development of the Hepatic Gluconeogenesis and Lipid Metabolism Disorder in Type 2 Diabetic Mice and in Palmitate-Incubated HepG2 Cells through Suppression of the HNF-4α miR122 Pathway.

Shengnan Wei,Grant M Hatch,Yang Yu,Ming Zhang,Fan Yao,Li Chen,Xiaoxin Lan,Xin Yan,Mengwei Zang

doi:10.1371/journal.pone.0152097

Abstract

Berberine (BBR) has been shown to exhibit protective effects against diabetes and dyslipidemia. Previous studies have indicated that BBR modulates lipid metabolism and inhibits hepatic gluconeogensis by decreasing expression of Hepatocyte Nuclear Factor-4α (HNF-4α). However, the mechanism involved in this process was unknown. In the current study, we examined the mechanism of how BBR attenuates hepatic gluconeogenesis and the lipid metabolism alterations observed in type 2 diabetic (T2D) mice and in palmitate (PA)-incubated HepG2 cells. Treatment with BBR for 4 weeks improve all biochemical parameters compared to T2D mice. Treatment of T2D mice for 4 weeks or treatment of PA-incubated HepG2 cells for 24 h with BBR decreased expression of HNF-4α and the microRNA miR122, the key gluconeogenesis enzymes Phosphoenolpyruvate carboxykinase (PEPCK) and Glucose-6-phosphatase (G6Pase) and the key lipid metabolism proteins Sterol response element binding protein-1 (SREBP-1), Fatty acid synthase-1 (FAS-1) and Acetyl-Coenzyme A carboxylase (ACCα) and increased Carnitine palmitoyltransferase-1(CPT-1) compared to T2D mice or PA-incubated HepG2 cells. Expression of HNF-4α in HepG2 cells increased expression of gluconeogenic and lipid metabolism enzymes and BBR treatment or knock down of miR122 attenuated the effect of HNF-4α expression. In contrast, BBR treatment did not alter expression of gluconeogenic and lipid metabolism enzymes in HepG2 cells with knockdown of HNF-4α. In addition, miR122 mimic increased expression of gluconeogenic and lipid metabolism enzymes in HepG2 cells with knockdown of HNF-4α. These data indicate that miR122 is a critical regulator in the downstream pathway of HNF-4α in the regulation of hepatic gluconeogenesis and lipid metabolism in HepG2 cells. The effect of BBR on hepatic gluconeogenesis and lipid metabolism is mediated through HNF-4α and is regulated downstream of miR122. Our data provide new evidence to support HNF-4α and miR122 regulated hepatic gluconeogenesis and lipid metabolism as promising therapeutic targets for the treatment of T2D.

Highlights

Type 2 diabetes mellitus (T2D) is a metabolic syndrome characterized by a high circulating blood glucose level and a disorder of lipid metabolism [1,2,3]
The oral glucose tolerance test (OGTT) indicated that plasma glucose was elevated in drug treatment (DM) animals and the area under the glucose concentration curve (AUC) was approximately 3-fold greater in DM animals compared to controls (Fig 1)
BBR treatment of T2D mice inhibited the expression of liver Sterol response element binding protein-1 (SREBP-1), a transcription factor required for lipogenic gene expression, and expression of liver Fatty acid synthase-1 (FAS-1) a key protein involved in fatty acid synthesis

Summary

Introduction

Type 2 diabetes mellitus (T2D) is a metabolic syndrome characterized by a high circulating blood glucose level and a disorder of lipid metabolism [1,2,3]. As a major insulin sensitive organ, the liver plays a key role in both glucose and lipid homeostasis. Extensive effort has been focused on the treatment of the hepatic gluconeogenic and lipid metabolism disorders associated with T2D [1,4,5]. Drugs which could target both the hepatic gluconeogenesis as well as the lipid metabolism disorder of T2D would serve as promising therapies [6,7]. Hepatocyte Nuclear Factor-4α (HNF-4α) is a key transcriptional factor essential for differentiation of liver [8,9]. HNF4α was reported to be critical in the maintenance of hepatocyte differentiation and is a major in vivo regulator of genes involved in the control of lipid homeostasis [14]

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Conclusion