Distorted expression of isoforms of the skeletal muscle myosin heavy chain (MHC) protein is a hallmark of altered protein metabolism in muscle of humans with obesity. The most striking feature of this, is a characteristic reduction in the content of the slow MHC-I isoform, which is responsible for determining the content of Type I muscle fibers. These fibers are characterized by increased capacity for glucose uptake, and in contrast to Type II fibers, maintain sensitivity to fuel metabolism within the adverse metabolic environment of obesity. Increased content of Type I fibers in skeletal muscle, and thus favorable metabolic effects in muscle, require increased expression of MHC-I in muscle. Importantly, the slow MHC-I gene drives the molecular mechanisms that determine the overall MHC protein metabolism and fiber type phenotype in skeletal muscle. The project seeks to determine the underlying biology that sustains distorted MHC protein metabolism in skeletal muscle of humans with obesity.~The investigators evaluate protein metabolism in skeletal muscle of humans with obesity and lean controls, and focus specifically on that of MHC isoforms. The investigators determine gene expression of the MHC isoforms and associated molecular factors implicated in activating Type I muscle fiber programming. Acute aerobic exercise and increase in plasma amino acids are employed as experimental tools to target biological processes of transcription and translation related to MHC genes expression in skeletal muscle. The overall findings will provide an understanding of mechanisms responsible for unfavorable MHC proteome and fiber type phenotype in skeletal muscle of humans with obesity.
Maintenance of protein homeostasis is impaired in skeletal muscle of humans with obesity. A hallmark of this defect is distorted expression of isoforms of the myosin heavy chain (MHC) protein, and this defect is linked to obesity-associated adverse health outcomes. By employing exercise and increase in plasma amino acids as investigational tools the investigators intend to modulate the metabolism of muscle MHC isoforms in order to unravel the biological mechanisms that sustain distorted MHC protein metabolism in muscle of humans with obesity.