Ethanol Shifts Myoblast Bioenergetic Phenotype: Implications for Muscle Regeneration

Abstract

At‐risk alcohol use is nearly twice as prevalent among people living with HIV (PLWH) as the general population. Alcohol and HIV can independently and synergistically increase risk for metabolic diseases, including myopathy. Decreased functional skeletal muscle (SKM) mass is associated with morbidity and all‐cause mortality. A major focus of our research is to investigate the independent and combined effects of alcohol and HIV on SKM regenerative capacity and its contribution to myopathy development. Previously, we showed that in vitro ethanol decreases myoblast extracellular acidification rate (ECAR), indicative of decreased glycolytic function, and that the decrease in ECAR was associated with decreased myoblast differentiation. The objective of this study was to determine effects of prior and recent alcohol exposure and simian immunodeficiency virus (SIV) on bioenergetic function in myoblasts from naïve and SIV‐infected rhesus macaques. Female rhesus macaques (6‐10 years of age) were administered chronic binge alcohol (CBA; peak blood alcohol concentration=50‐60 mM, 5 days per week) or isovolumetric water vehicle (VEH) beginning 3 months prior to infection with SIVmac251. Daily antiretroviral therapy (ART) was initiated 2.5 months after SIV infection, and macaques were humanely euthanized 9 months later. SKM samples were collected for myoblast isolation prior to CBA or VEH (naïve, N=6) and at study end point (VEH/SIV, N=6; CBA/SIV, N=6). Myoblasts from each group were incubated with ethanol (0 and 50 mM) for 3 days prior to Mito Stress Test, Glycolysis Stress Test, and ATP Rate Assay using an XFe96 Extracellular Flux Analyzer. There were no significant differences due to CBA or SIV on mitochondrial or glycolytic function for any measure. During the Mito Stress Test, ethanol exposure significantly (p<0.05) decreased ECAR at baseline and after the addition of oligomycin (ATP synthase inhibitor), indicative of decreased glycolytic function, without significant changes in mitochondrial function. Similarly, ethanol exposure decreased all parameters in the Glycolysis Stress Test (non‐glycolytic acidification, glycolysis, glycolytic reserve, and glycolytic capacity). An ATP rate assay confirmed that ethanol exposure significantly decreased glycolytic ATP production, contributing to a decrease in total ATP production. These results indicate that recent exposure to an intoxicating concentration of ethanol shifts myoblast bioenergetic phenotype, impairs glycolysis, and produces a bioenergetic deficit regardless of prior alcohol exposure or SIV/ART. The shift away from glycolysis occurs under basal and stressed conditions. We propose that altered glycolytic enzyme activity underlies the alcohol‐mediated decrease in glycolytic function, negatively impacting myoblast differentiation and SKM regenerative capacity.