Bile Acid–Mediated Activation of Brown Fat Protects From Alcohol-Induced Steatosis and Liver Injury in Mice

Mingjie Fan, Yangmeng Wang, Lihua Jin, Zhipeng Fang, Jiangling Peng, Jui Tu, Yanjun Liu, Eryun Zhang, Senlin Xu, Xiaoqian Liu, Yuqing Huo, Zhaoli Sun, Xiaojuan Chao, Wen Xing Ding, Qingfeng Yan, Wendong Huang

Research output: Contribution to journalArticlepeer-review

Abstract

Background & Aims: Alcohol-associated liver disease (AALD) is one of the most common causes of liver injury and failure. Limited knowledge of the mechanisms underlying AALD impedes the development of efficacious therapies. Bile acid (BA) signaling was shown to participate in the progression of AALD. However, the mechanisms remain poorly understood. Methods: C57BL/6J wild-type (WT), Takeda G-protein–coupled bile acid receptor 5 (TGR5) knockout (KO) and brown adipose tissue (BAT)-specific TGR5 knockdown mice were subjected to ethanol feeding–induced AALD. Liver samples from alcoholic hepatitis patients were used to examine the BA circulation signaling. Human Embryonic Kidney Cells 293 were used for the TGR5 reporter assay. 23(S)-methyl-lithocholic acid was used as a molecular tool to confirm the regulatory functions of BAT in the AALD mouse model. Results: Ethanol feeding increased the expression of the thermogenesis genes downstream of TGR5 in BAT of WT, but not TGR5 KO, mice. TGR5 deficiency significantly blocked BAT activity and energy expenditure in mice after ethanol feeding. Alcohol increased serum BA levels in mice and human beings through altering BA transportation, and the altered BAs activated TGR5 signaling to regulate metabolism. Compared with ethanol-fed WT mice, ethanol-fed TGR5 KO mice showed less free fatty acid (FFA) β-oxidation in BAT, leading to higher levels of FFA in the circulation, increased liver uptake of FFAs, and exacerbated AALD. BAT-specific TGR5 knockdown mice showed similar results with TGR5 KO mice in AALD. Agonist treatment significantly activated TGR5 signaling in BAT, increased thermogenesis, reduced serum FFA level, and ameliorated hepatic steatosis and injury in AALD mice, while these effects were lost in TGR5 KO mice. Conclusions: BA signaling plays a protective role in AALD by enhancing BAT thermogenesis. Targeting TGR5 in BAT may be a promising approach for the treatment of AALD.

Original languageEnglish (US)
Pages (from-to)809-826
Number of pages18
JournalCMGH
Volume13
Issue number3
DOIs
StatePublished - Jan 2022

Keywords

  • Alcohol-Associated Liver Disease (AALD)
  • BAT-Liver Crosstalk
  • TGR5 (GPBAR1)
  • Thermogenesis

ASJC Scopus subject areas

  • Gastroenterology
  • Hepatology

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