Protective role of cGAS in NASH is related to the maintenance of intestinal homeostasis

Abstract

AbstractBackground & AimsVarious intracellular pathways regulate inflammation in NASH. Cyclic GMP‐AMP synthase (cGAS) is a DNA sensor that activates STING and plays a role in inflammatory diseases. Here, we explored the role of cGAS in hepatic damage, steatosis, inflammation, and liver fibrosis in mouse models of NASH.MethodscGAS deficient (cGAS‐KO) and STING deficient (STING‐KO) mice received high fat‐high cholesterol‐high sugar diet (HF‐HC‐HSD) or relevant control diets. Livers were evaluated after 16 or 30 weeks.ResultsHF‐HC‐HSD diet, both at 16 and 30 weeks, resulted in increased cGAS protein expression as well as in increased ALT, IL‐1β, TNF‐α and MCP‐1 in wild‐type (WT) mice compared to controls. Surprisingly, liver injury, triglyceride accumulation, and inflammasome activation were greater in HF‐HC‐HSD cGAS‐KO compared to WT mice at 16 and to a lesser extent at 30 weeks. STING, a downstream target of cGAS was significantly increased in WT mice after HF‐HC‐HSD. In STING‐KO mice after HF‐HC‐HSD feeding, we found increased ALT and attenuated MCP1 and IL‐1β expression compared to WT mice. Markers of liver fibrosis were increased in cGAS‐ and STING‐KO mice compared to WT on HF‐HC‐HSD. We discovered that cGAS‐KO mice had a significant increase in circulating endotoxin levels on HF‐HC‐HSD that correlated with changes in intestinal morphology which was exacerbated by HF‐HC‐HSD compared to WT mice.ConclusionOur findings indicate that cGAS or STING deficiency exacerbate liver damage, steatosis, and inflammation in HF‐HC‐HSD diet‐induced NASH, which might be linked to the disruption of the gut barrier.