Glucagon-like peptide-1 (GLP-1) has a broad spectrum of biological activity by regulating metabolic processes via both the direct activation of the class B family of G protein-coupled receptors and indirect nonreceptor-mediated pathways. GLP-1 receptor (GLP-1R) agonists have significant therapeutic effects on non-alcoholic fatty liver disease (NAFLD) and steatohepatitis (NASH) in animal models. However, clinical studies indicated that GLP-1 treatment had little effect on hepatic steatosis in some NAFLD patients, suggesting that GLP-1 resistance may occur in these patients. It is well-known that the gut metabolite sodium butyrate (NaB) could promote GLP-1 secretion from intestinal L cells. However, it is unclear whether NaB improves hepatic GLP-1 responsiveness in NAFLD. In the current study, we showed that the serum GLP-1 levels of NAFLD patients were similar to those of normal controls, but hepatic GLP-1R expression was significantly downregulated in NAFLD patients. Similarly, in the NAFLD mouse model, mice fed with a high-fat diet showed reduced hepatic GLP-1R expression, which was reversed by NaB treatment and accompanied by markedly alleviated liver steatosis. In addition, NaB treatment also upregulated the hepatic p-AMPK/p-ACC and insulin receptor/insulin receptor substrate-1 expression levels. Furthermore, NaB-enhanced GLP-1R expression in HepG2 cells by inhibiting histone deacetylase-2 independent of GPR43/GPR109a. These results indicate that NaB is able to prevent the progression of NAFL to NASH via promoting hepatic GLP-1R expression. NaB is a GLP-1 sensitizer and represents a potential therapeutic adjuvant to prevent NAFL progression to NASH.
Fatty liver disease: A gutsy way to prevent disease progression: A treatment for non-alcoholic fatty liver disease that incorporates a metabolite found in the gut could prevent progression to a more serious liver condition. Drugs that enhance the activity of glucagon-like peptide-1 (GLP-1), a protein involved in regulating metabolic processes, have shown promise in targeting non-alcoholic fatty liver disease and the more serious condition, steatohepatitis. However, some patients appear resistant to treatment. Jian-Gao Fan at Shanghai Jiao Tong University in China, Huiping Zhou at McGuire VA Medical Center in Richmond, USA, and co-workers demonstrated that a gut metabolite called sodium butyrate may help encourage responsiveness to GLP-1 treatment. The team found that liver GLP-1R expression was considerably reduced in patients with liver disease compared with healthy controls. Experiments on mouse models showed that treatment incorporating sodium butyrate improved GLP-1R levels and reduced fatty liver deposits.