Myoblast mitochondrial respiration is decreased in chronic binge alcohol administered simian immunodeficiency virus-infected antiretroviral-treated rhesus macaques

Abstract

Work from our group demonstrated that chronic binge alcohol (CBA)-induces mitochondrial gene dysregulation at end-stage disease of simian immunodeficiency virus (SIV) infection in antiretroviral therapy (ART) naïve rhesus macaques. Alterations in gene expression can disrupt mitochondrial homeostasis and in turn contribute to the risk of metabolic comorbidities characterized by loss of skeletal muscle (SKM) functional mass that are associated with CBA, human immunodeficiency virus (HIV) infection, and prolonged ART. The aim of this study was to examine the interaction of CBA and ART on SKM fiber oxidative capacity and myoblast mitochondrial respiration in asymptomatic SIV-infected macaques. SKM biopsies were obtained and myoblasts isolated at baseline and 11 months post-SIV infection from CBA/SIV/ART+ and from sucrose (SUC)-treated SIV-infected (SUC/SIV/ART+) macaques. CBA and ART decreased succinate dehydrogenase (SDH) activity in type 1 and type 2b fibers as determined by immunohistochemistry. Myoblasts isolated from CBA/SIV/ART+ macaques showed decreased maximal oxygen consumption rate (OCR) compared to myoblasts from control macaques. Maximal OCR was significantly increased in control myoblasts following incubation with formoterol, a beta adrenergic agonist, and this was associated with increased PGC-1α expression and mtDNA quantity. Additionally, formoterol treatment of myoblasts isolated from CBA/SIV/ART+ macaques partially restored maximal OCR to levels not significantly different from control. These results show that CBA in combination with ART impairs myoblast mitochondrial homeostasis in SIV-infected macaques. Moreover, our findings suggest that adrenergic agonists can potentially ameliorate mitochondrial dysfunction. Future studies will elucidate whether physical exercise in HIV patients with alcohol use disorder can improve mitochondrial health.

Keywords: Chronic alcohol; HIV; SIV; mitochondria.

Figure 1

Succinate dehydrogenase activity. Skeletal muscle (SKM) tissue isolated from sucrose (SUC)‐ or chronic binge alcohol (CBA)‐administered macaques with and without antiretroviral therapy (ART) was stained for succinate dehydrogenase (SDH) activity and compared to naïve control (CTRL) macaque SKM tissue. (A) Representative micrographs of SDH activity in the muscle. (B) There was a significant CBA × ART interaction (P < 0.05) to decrease SDH activity in Type 1 and Type 2b skeletal muscle fiber types. (C) There was a main effect of CBA to decrease SDH activity in type 2a fibers. (D) There was a main effect of ART to decrease SDH activity in type 2b fibers. Optical density quantification was normalized to control (Dotted line; n = 4) for each of the following groups: SUC/SIV/ART‐ (white open bars, n = 5), SUC/SIV/ART+ (white hatched bars, n = 3), CBA/SIV/ART‐ (gray bars, n = 3), and CBA/SIV/ART+ (gray hatched bars, n = 4). Data are expressed as mean ± SEM.

Figure 2

Myoblast oxygen consumption rates (OCR). OCR of macaque myoblasts were measured using the Seahorse XF24e extracellular flux analyzer in response to 1.0 μmol/L oligomycin (Oligo), 2.0 μmol/L carbonyl cyanide‐p‐trifluoromethoxyphenylhydrazone (FCCP), and 0.5 μmol/L Rotenone/antimycin A (Rot/A). There were no significant differences in Basal OCR. Maximal OCR was significantly lower in CBA/SIV/ART+ compared to CTRL (Inset). *P < 0.05. Data are expressed as mean ± SEM. N = 3–4/group.

Figure 3

Control and CBA/SIV/ART+ myoblast formoterol treatment. (A) Oxygen consumption rates (OCR) of myoblasts measured using the Seahorse XF24e extracellular flux analyzer in response to 1.0 μmol/L oligomycin (Oligo), 2.0 μmol/L carbonyl cyanide‐p‐trifluoromethoxyphenylhydrazone (FCCP), and 0.5 μmol/L Rotenone/antimycin A (Rot/A). There were no significant differences in Basal OCR. (B) Maximal OCR was significantly increased with formoterol‐treated control (CTRL) myoblasts. Maximal OCR was significantly lower in CBA/SIV/ART+ (‐FORM) compared to CTRL. CBA/SIV/ART+ (+FORM) was not different from CTRL. *P < 0.05 from CTRL (‐FORM). (C) There was a significant increase in the expression of PGC‐1a at 6 h after formoterol treatment in CTRL myoblasts. (D) There was a significant increase in mitochondrial DNA copy number (mtDNA/Nuclear DNA expression) at 24 h after formoterol treatment in CTRL myoblasts. There was a 1.6‐fold increase (P = 0.07) in formoterol treated CBA/SIV/ART+ myoblasts. *P < 0.05. Data are expressed as mean ± SEM. N = 3–4/group.