Hepatic Ago2 Regulates PPAR[alpha] for Oxidative Metabolism Linked to Glycemic Control in Obesity and Post Bariatric Surgery

Argonaute 2 (Ago2) is the main component of the RNA-induced silencing complex. We recently showed that liver-specific Ago2-deficiency in mice (L-Ago2 knockout [KO] mice) enhances mitochondrial oxidation and alleviates obesity-associated pathophysiology. However, the precise mechanisms behind the role of hepatic Ago2 in regulating the mitochondrial oxidation associated with glucose metabolism are still unclear. Here, we show that hepatic Ago2 regulates the function of peroxisome proliferator-activated receptor [alpha] (PPAR[alpha]) for oxidative metabolism. In both genetically and diet-induced severe obese conditions, L-Ago2 KO mice developed obesity and hepatic steatosis but exhibited improved glucose metabolism accompanied by lowered expression levels of pathologic microRNAs (miRNAs), including miR-802, miR-103/107, and miR-152, and enhanced expression of PPAR[alpha] and its target genes regulating oxidative metabolism in the liver. We then investigated the role of hepatic Ago2 in the outcomes of vertical sleeve gastrectomy (VSG) in which PPAR[alpha] plays a crucial role in a drastic transcription reprogram associated with improved glycemia post VSG. Whereas VSG reduced body weight and improved fatty liver in wild-type mice, these effects were not observed in hepatic Ago2-deficient mice. Conversely, glucose metabolism was improved in a hepatic Ago2-dependent manner post VSG. Treating Ago2-deficient primary hepatocytes with WY-14643, a PPAR[alpha] agonist, showed that Ago2-deficiency enhances sensitivity to WY-14643 and increases expression of PPAR[alpha] target genes and mitochondrial oxidation. Our findings suggest that hepatic Ago2 function is intrinsically associated with PPAR[alpha] that links Ago2-mediated RNA silencing with mitochondrial functions for oxidation and obesity-associated pathophysiology. Key Words: obesity, bariatric surgery, RNA silencing, Argonaute 2, PPAR[alpha]