5‐Aza‐2′‐deoxycytidine‐mediated DNA hypomethylation with and without concurrent insulin resistance suppresses myotube mitochondrial capacity

Abstract

Type 2 diabetes is characterized by elevated blood glucose and reduced insulin sensitivity in target tissues. Moreover, reduced mitochondrial metabolism and expressional profile of genes governing mitochondrial metabolism (such as peroxisome proliferator‐activated receptor gamma coactivator 1‐alpha [PGC‐1α]) are also reduced during insulin resistance. Epigenetic regulation via DNA methylation of genes including PGC‐1α may contribute to diminished mitochondrial capacity, while hypomethylation of PGC‐1α (such as that invoked by exercise) has been associated with increased PGC‐1α expression and favorable metabolic outcomes. The purpose of the present report is to characterize the effects of DNA hypomethylation on myotube metabolism and expression of several related metabolic targets. C2C12 myotubes were treated with 5‐Aza‐2′‐deoxycytidine (5‐Aza) for either 24 or 72 h both with and without hyperinsulinemic‐induced insulin resistance. Mitochondrial and glycolytic metabolism were measured via oxygen consumption and extracellular acidification rate, respectively. Metabolic gene and protein expression were assessed via quantitative real time polymerase chain reaction and western blot analysis, respectively. Though expression of PGC‐1α and other related targets remained unaltered, insulin resistance and 5‐Aza treatment significantly reduced mitochondrial metabolism. Similarly, peak glycolytic metabolism was diminished by 5‐Aza‐treated cells, while basal glycolytic metabolism was unaltered. 5‐Aza also reduced the expression of branched‐chain amino acid (BCAA) catabolic components, however BCAA utilization was enhanced during insulin resistance with 5‐Aza treatment. Together the present work provides proof‐of‐concept evidence of the potential role of DNA methylation in the regulation of mitochondrial metabolism and the potential interactions with insulin resistance in a model of skeletal muscle.