Nonalcoholic fatty liver disease is becoming the most common chronic liver disease in Western countries, and limited therapeutic options are available. Here we uncovered a role for intestinal hypoxia-inducible factor (HIF) in hepatic steatosis. Human-intestine biopsies from individuals with or without obesity revealed that intestinal HIF-2α signaling was positively correlated with body-mass index and hepatic toxicity. The causality of this correlation was verified in mice with an intestine-specific disruption of Hif2a, in which high-fat-diet-induced hepatic steatosis and obesity were substantially lower as compared to control mice. PT2385, a HIF-2α-specific inhibitor, had preventive and therapeutic effects on metabolic disorders that were dependent on intestine HIF-2α. Intestine HIF-2α inhibition markedly reduced intestine and serum ceramide levels. Mechanistically, intestine HIF-2α regulates ceramide metabolism mainly from the salvage pathway, by positively regulating the expression of Neu3, the gene encoding neuraminidase 3. These results suggest that intestinal HIF-2α could be a viable target for hepatic steatosis therapy.

No abstract

Nonalcoholic steatohepatitis (NASH) is the progressive stage of nonalcoholic fatty liver disease that may ultimately lead to cirrhosis and liver cancer, and there are few therapeutic options for its treatment. Glycyrrhizin (GL), extracted from the traditional Chinese medicine liquorice, has potent hepatoprotective effects in both preclinical animal models and in humans. However, little is currently known about its effects and mechanisms in treating NASH. To explore the effects of GL on NASH, GL or its active metabolite glycyrrhetinic acid (GA) was administered to mice treated with a methionine- and choline-deficient (MCD) diet-induced NASH model, and histologic and biochemical analyses were used to measure the degree of lipid disruption, liver inflammation, and fibrosis. GL significantly improved MCD diet-induced hepatic steatosis, inflammation, and fibrosis and inhibited activation of the NLR family pyrin domain-containing 3 (NLRP3) inflammasome. GL significantly attenuated serum bile acid accumulation in MCD diet-fed mice partially by restoring inflammation-mediated hepatic farnesoid X receptor inhibition. In Raw 264.7 macrophage cells, both GL and GA inhibited deoxycholic acid-induced NLRP3 inflammasome-associated inflammation. Notably, both intraperitoneal injection of GL's active metabolite GA and oral administration of GL prevented NASH in mice, indicating that GL may attenuate NASH via its active metabolite GA. These results reveal that GL, via restoration of bile acid homeostasis and inhibition of inflammatory injury, can be a therapeutic option for treatment of NASH.