The TSPO ligand 3,17,19-androsten-5-triol attenuates NASH by increasing FXR expression and autophagy.

Translocator protein (TSPO; 18 kDa) is a ubiquitous high-affinity cholesterol- and drug-binding protein located in the outer mitochondrial membrane. 3,17,19-androsten-5-triol (19-Atriol) is a ligand binding at the cholesterol recognition amino acid consensus domain of TSPO. Our previous study suggested that TSPO deficiency ameliorated methionine-choline-deficient induced non-alcoholic steatohepatitis (NASH) through downregulation of bile acid synthesis (Li et al., iScience 24: 102457, 2021). We examined the role of cholesterol binding to TSPO in NASH using the 19-Atriol on high-fat-fructose-cholesterol diet (HFFC)-induced NASH in rats. After HFFC-feeding for 13weeks, the rats were subcutaneously administered daily 19-Atriol (20mg/kg) for 2 weeks (weeks 13-15). The ratio of liver/body weight and serum triacylglycerol content were significantly reduced in 19-Atriol- compared to vehicle-treated rats. Immunoblot analyses indicated that liver inflammation (TNFα) and fibrosis markers (COL1A1, ACTA2) were reduced following 19-Atriol treatment. Farnesoid X receptor (FXR), a bile acid receptor, was upregulated in response to 19-Atriol treatment in HFFC-fed rats. In search of the mechanism mediating the effects of 19-Atriol we observed an increase in autophagy flux and the levels of phosphorylated transcription factor EB (TFEB), a major regulator of autophagy and lysosomal biogenesis. Taken together these results suggest that blocking cholesterol binding to TSPO by 19-Atriol leads to the attenuation of NASH by increasing FXR expression levels and activating of autophagic degradation as was the case in TSPO-deficient rats.