Chemogenetic activation of hepatic G signaling ameliorates hepatic steatosis and obesity.

Objective: Hepatic steatosis, the early stage of nonalcoholic fatty liver disease (NAFLD), currently lacks targeted pharmacological treatments. G protein-coupled receptors (GPCRs) in hepatocytes differentially regulate lipid metabolism depending on their coupling profile of G protein subtypes. Unlike G, G, and G signaling, the role of G signaling in hepatic steatosis remains elusive. The objective of this study was to investigate the effect of G signaling on hepatic steatosis and obesity and its mechanisms.

Methods: We generated mice expressing a G-coupled designer GPCR in a liver-specific manner. We performed phenotypic analysis in the mice under the condition of fasting (acute hepatic steatosis model) or high-fat diet feeding (chronic hepatic steatosis model).

Results: In acute and chronic hepatic steatosis models, chemogenetic activation of hepatic G signaling suppressed the progression of hepatic steatosis. The treatment led to an increased triglyceride secretion with little effect on mitochondrial respiratory activity, fatty acid oxidation, de novo lipogenesis, and fatty acid uptake. Furthermore, in a high-fat-diet-induced obesity model, activation of the G-coupled designer GPCR exerted anti-obesity effects with increased whole-body energy expenditure and fat oxidation. Anti-FGF21 antibody treatment showed that the anti-obesity effects of the hepatic GD activation relied in part on the hepatokine FGF21.

Conclusions: Our findings indicate that the activation of G signaling in the liver has the potential to prevent hepatic steatosis and obesity. This discovery provides a strong rationale for the development of drugs targeting G-coupled GPCRs expressed in the liver.