Hepatocyte miR-33a mediates mitochondrial dysfunction and hepatosteatosis by suppressing NDUFA5

Emerging evidence suggests that microRNAs (miRNAs) are essential for metabolic haemostasis of liver tissues. Among them, miR-33a is supposed to modulate the cholesterol export and fatty acid oxidation, but whether miR-33a involves in the process of fatty liver disease is unclear. To disclose the hypothesis, we utilized miR-33a mimic and antisense to explore their effects in primary hepatocytes or high-fat diet (HFD)-fed mice. Treatment with palmitic acid (PA) or HFD significantly increased the expression of miR-33a in hepatocytes or liver tissues. In primary hepatocytes, miR-33a mimic decreased mitochondrial function, including reduction of ATP production and oxygen consumption, whereas miR-33a inhibition protected PA-induced mitochondrial dysfunction. Interestingly, miR-33a selectively suppressed mitochondrial complex I activity and protein expression, but not other complexes. Through bioinformatics prediction, we found miR-33a directly targeted on the 3'-UTR of NDUFA5. Dual-luciferase reporter analysis further confirmed the direct suppression of miR-33a on NDUFA5 expression. More importantly, administration of miR-33a antisense could effectively restore HFD-induced mitochondrial dysfunction through up-regulation of NDUFA5 levels. Mice treated with miR-33a antisense also exhibited improved liver function and structural disorders under obese status. Taken together, miR-33a was an important mediator of hepatocyte mitochondrial function, and the therapeutic benefits implied miR-33a antisense had the potential clinical application in combating the fatty liver disease.