Saturated Fatty Acids Promote Hepatocytic Senecence through Regulation of miR‐34a/Cyclin‐Dependent Kinase 6

Scope Obesity increases intracellular lipid accumulation in hepatocytes, which can induce non‐alcoholic fatty liver disease (NAFLD). With progression of NAFLD, a sizable fraction of patients develop non‐alcoholic steatohepatitis (NASH), eventually leading to cirrhosis and hepatocellular carcinoma (HCC). The mechanism involved in obesity‐induced NAFLD remains unclear. Free fatty acids and high‐fat diets, which induce hepatocyte senescence, are major risk factors for NAFLD. Therefore in this study, the mechanism of lipotoxicity‐induced hepatocyte senescence is investigated. Methods and Results The mice are fed a high‐fat diet (HFD) and BNL CL.2 cells are treated with palmitate acid (PA) to establish in vivo and in vitro models of lipotoxicity, respectively. SA‐β‐gal staining is used to analyze the positively stained senescent hepatocytes. The results show that both PA and HFD induce cellular senescence. Real‐time‐PCR quantitative analysis reveals that miR‐34a is significantly upregulated in the liver tissues of the HFD mice and in the PA‐treated BNL CL.2 cells. Western blotting analysis shows that cyclin‐dependent kinase inhibitor 1 (CDKN1, also known as p21) is upregulated, while cyclin‐dependent kinase 6 (CDK6) is downregulated. Further investigation of the mechanism reveals that CDK6 is a target of miR‐34a, which binds to the 3′ UTR of CDK6 and inhibits its expression. Conclusion The findings reveal that miR‐34a is upregulated in a high‐fat environment in the liver, and induces hepatocyte senescence by targeting CDK6. The miR‐34a‐CDK6 signaling axis may promote NAFLD development in a high‐fat environment and therefore represents a potential target for NAFLD therapy. High‐fat diet (HFD) or PA induces the hepatocyte senescence, and increases the miR‐34a. MiR‐34a mimic or inhibitor treated the BNL CL.2 respectively, and miR‐34a inhibitor treated HFD‐induced mice. Luciferase Reporter assays find that miR‐34a targets the 3′ UTR of CDK6 mRNA. It is revealed that miR‐34a upregulated in high fat environment and targeted CDK6 induces hepatocyte senescence.