The impact of high fat feeding and Parkin overexpression on skeletal muscle mass, mitochondrial respiration and H2O2 emission

Obesity is a major risk factor for developing various health problems, including insulin resistance and type 2 diabetes. Although controversial, accumulation of mitochondrial dysfunction, and notably an increase in mitochondrial reactive oxygen species (ROS) production, was proposed as a key contributor leading to obesity-induced insulin resistance. Here, our goal was to investigate whether Parkin overexpression, a key regulator of the removal of dysfunctional mitochondria through mitophagy, could confer protection against obesity-induced mitochondrial dysfunction. To this end, intramuscular injections of adeno-associated viruses (AAV) were performed to overexpress Parkin in limb muscle of 6-month-old mice fed a control diet (CD) or a high fat diet (HFD) for 12 weeks. An AAV expressing GFP was used as control. HFD increased fat mass, altered glycemia and resulted in insulin resistance. Parkin overexpression resulted in an increase in muscle mass in both CD and HFD mice. In CD mice, Parkin overexpression increased maximal mitochondrial respiration and lowered H2O2 emission. HFD increased mitochondrial respiration and, surprisingly, also lowered H2O2 emission. Parkin overexpression did not significantly impact mitochondrial function in HFD mice. Taken altogether, our results indicate that Parkin overexpression positively impacts muscle and mitochondrial health under basal conditions and challenge the notion that intrinsic mitochondrial dysfunction is involved in the development of insulin resistance caused by high fat feeding.