Conophylline inhibits non-alcoholic steatohepatitis in mice.

Yukiomi Nakade,Haruhisa Nakao,Takaya Yamamoto,Kazumasa Sakamoto,Yoshitaka Fukuzawa,Kazuo Umezawa,Kiyoaki Ito,Tadahisa Inoue,Norimitsu Ishii,Yuji Kobayashi,Masashi Yoneda,Tomohiko Ohashi,Taeko Yamauchi,Yoshio Sumida,Hervé Guillou

doi:10.1371/journal.pone.0178436

Abstract

Conophylline (CnP), a vinca alkaloid extracted from the leaves of the tropical plant Ervatamia microphylla, attenuates hepatic fibrosis in mice. However, little is known about whether CnP inhibits steatosis, inflammation, and fibrosis in non-alcoholic steatohepatitis (NASH) in mice. A methionine-choline-deficient (MCD) diet was administered to male db/db mice as a NASH model, and CnP (1 μg/kg/d) was co-administered. Eight weeks after the commencement of the MCD diet, hepatic steatosis, inflammation, and fibrosis, and hepatic fat metabolism-, inflammation-, and fibrosis-related markers were examined. Feeding on an MCD for 8 weeks induced hepatic steatosis, inflammation, and fibrosis. CnP significantly attenuated the MCD-induced increases in hepatic steatosis, as well as hepatic inflammation and fibrosis. The MCD diet increased hepatic transforming growth factor-β (TGF-β) mRNA levels, which are correlated with hepatic steatosis, inflammation, and fibrosis. The diet also attenuated acyl-coenzyme A oxidase 1 (ACOX1) and carnitine palmitoyltransferase 1 (CPT1) mRNA levels, which are involved in β-oxidation. The putative mechanism of the CnP effect involves reduced hepatic TGF-β mRNA levels, and increased mRNA levels of hepatic peroxisome proliferator-activated receptor (PPAR) α and its target genes ACOX1 and CPT1. The results of this study indicate that CnP inhibits steatohepatitis, possibly through the inhibition of hepatic TGF-β mRNA levels, and induces an increase in PPARα mRNA levels, resulting in the attenuation of hepatic steatosis, inflammation, and fibrosis in mice. CnP might accordingly be a suitable therapeutic option for NASH.

Highlights

Non-alcoholic fatty liver disease (NAFLD), which encompasses a wide range of disorders, has become a major health issue and the most common liver disease throughout the world [1]
We demonstrate that CnP improves steatohepatitis in mice via the downregulation of transforming growth factor-β (TGF-β) and upregulation of peroxisome proliferator-activated receptor α (PPARα) and its downstream targets involved in fatty acid oxidation
The MCD diet significantly increased hepatic TG contents, steatosis scores, and hepatic free fatty acid (FFA) contents, which were significantly decreased by CnP (Tables 1 and 2)

Summary

Introduction

Non-alcoholic fatty liver disease (NAFLD), which encompasses a wide range of disorders, has become a major health issue and the most common liver disease throughout the world [1]. High-fat and/or high-cholesterol diets have been used as obese NAFLD models [13, 14], whereas a methionine-choline-deficient (MCD) diet has been reported to induce steatohepatitis, which is morphologically similar to NASH [15]. Db/db mice spontaneously develop type 2 diabetes and fatty liver with obesity due to a partial functional defect in the long form of the leptin receptor [19]. These mice are hyperphagic when a high-fat or normal diet is administered, and hepatic steatosis in db/db mice is significantly increased compared with that in control mice, even when a normal diet is administered [18]. We demonstrate that CnP improves steatohepatitis in mice via the downregulation of transforming growth factor-β (TGF-β) and upregulation of peroxisome proliferator-activated receptor α (PPARα) and its downstream targets involved in fatty acid oxidation

Materials and methods

Results

Discussion