P38 gamma modulates the lipid metabolism in non-alcoholic fatty liver disease by regulating the JAK-STAT signaling pathway

Non-alcoholic fatty liver disease (NAFLD) is a major health problem in Western countries and has become the most common cause of chronic liver disease. Although NAFLD is closely associated with obesity, inflammation, and insulin resistance, its pathogenesis remains unclear. The disease begins with excessive accumulation of triglycerides in the liver, which in turn leads to liver cell damage, steatosis, inflammation, and so on. P38 gamma is one of the four isoforms of P38 mitogen-activated protein kinases (P38 MAPKs) that contributes to inflammation in different diseases. In this research, we investigated the role of P38 gamma in NAFLD. In vivo, a NAFLD model was established by feeding C57BL/6J mice with a methionine- and choline-deficient (MCD) diet and adeno-associated virus (AAV9-shRNA-P38 gamma) was injected into C57BL/6J mice by tail vein for knockdown P38 gamma. The results indicated that the expression level of P38 gamma was upregulated in MCD-fed mice. Furthermore, the downregulation of P38 gamma significantly attenuated liver injury and lipid accumulation in mice. In vitro, mouse hepatocytes AML-12 were treated with free fatty acid (FFA). We found that P38 gamma was obviously increased in FFA-treated AML-12 cells, whereas knockdown of P38 gamma significantly suppressed lipid accumulation in FFA-treated AML-12 cells. Furthermore, P38 gamma regulated the Janus Kinase-Signal transducers and activators of transcription (JAK-STAT) signaling pathway. Inhibition of P38 gamma can inhibit the JAK-STAT signaling pathway, thereby inhibiting lipid accumulation in FFA-treated AML-12 cells. In conclusion, our results suggest that targeting P38 gamma contributes to the suppression of lipid accumulation in fatty liver disease.