Skeletal muscle bioenergetic health and function in people living with HIV: association with glucose tolerance and alcohol use

Alcohol Impairs Bioenergetics and Differentiation Capacity of Myoblasts from Simian Immunodeficiency Virus-Infected Female Macaques

Alcohol misuse and HIV independently induce myopathy. We previously showed that chronic binge alcohol (CBA) administration, with or without simian immunodeficiency virus (SIV), decreases differentiation capacity of male rhesus macaque myoblasts. We hypothesized that short-term alcohol and CBA/SIV would synergistically decrease differentiation capacity and impair bioenergetic parameters in female macaque myoblasts. Myoblasts from naïve (CBA-/SIV-), vehicle [VEH]/SIV, and CBA/SIV (N = 4-6/group) groups were proliferated (3 days) and differentiated (5 days) with 0 or 50 mM ethanol (short-term). CBA/SIV decreased differentiation and increased non-mitochondrial oxygen consumption rate (OCR) versus naïve and/or VEH/SIV. Short-term alcohol decreased differentiation; increased maximal and non-mitochondrial OCR, mitochondrial reactive oxygen species (ROS) production, and aldolase activity; and decreased glycolytic measures, ATP production, mitochondrial membrane potential (ΔΨm), and pyruvate kinase activity. Mitochondrial ROS production was closely associated with mitochondrial network volume, and differentiation indices were closely associated with key bioenergetic health and function parameters. Results indicate that short-term alcohol and CBA non-synergistically decrease myoblast differentiation capacity. Short-term alcohol impaired myoblast glycolytic function, driving the bioenergetic deficit. Results suggest potentially differing mechanisms underlying decreased differentiation capacity with short-term alcohol and CBA, highlighting the need to elucidate the impact of different alcohol use patterns on myopathy.

Alcohol and Skeletal Muscle in Health and Disease

PURPOSE

Alcohol-related myopathy is one of the earliest alcohol-associated pathological tissue changes that is progressively exacerbated by cumulative long-term alcohol misuse. Acute and chronic alcohol use leads to changes in skeletal muscle mass and function. As discussed in this evidence-based review, alcohol-mediated mechanisms are multifactorial with effects on anabolic and catabolic signaling, mitochondrial bioenergetics, extracellular matrix remodeling, and epigenomic alterations. However, systematic studies are limited, especially regarding the acute effects of alcohol on skeletal muscle.

SEARCH METHODS

This review focuses on peer-reviewed manuscripts published between January 2012 and November 2022 using the search terms "alcohol" or "ethanol" and "skeletal muscle" in MEDLINE, PubMed, and Web of Science using EndNote reference management software.

SEARCH RESULTS

Eligible manuscripts included full-length research papers that discussed acute and chronic effects of alcohol on skeletal muscle mass and function in both clinical and preclinical studies. The review also includes alcohol-mediated skeletal muscle effects in the context of comorbidities. The three databases together yielded 708 manuscripts. Of these, the authors excluded from this review 548 papers that did not have "alcohol" or "muscle" in the title and 64 papers that were duplicates or did not discuss skeletal muscle. Thus, of all the manuscripts considered for this review, 96 are included and 612 are excluded. Additionally, relevant papers published earlier than 2012 are included to provide context to the review.

DISCUSSION AND CONCLUSIONS

Both acute and chronic alcohol use decrease protein synthesis and increase protein degradation. Alcohol also impairs mitochondrial function and extracellular matrix remodeling. However, there is a gap in the literature on the known alcohol-mediated mechanisms, including senescence, role of immune activation, and interorgan communication, on the development of alcohol-related myopathy. With increased life expectancy, changing alcohol use patterns, and increasing frequency of alcohol use among females, current observational studies are needed on the prevalence of alcohol-related myopathy. Additionally, the compounding effects of acute and chronic alcohol use on skeletal muscle with aging or exercise, in response to injury or disuse, and in the context of comorbidities including diabetes and human immunodeficiency virus (HIV), call for further investigation. Though evidence suggests that abstinence or reducing alcohol use can improve muscle mass and function, they are not restored to normal levels. Hence, understanding the pathophysiological mechanisms can help in the design of therapeutic strategies to improve skeletal muscle health.

An aerobic exercise intervention to improve metabolic health among people living with HIV with at-risk alcohol use: the ALIVE-Ex research study protocol

BACKGROUND

Effective antiretroviral therapy (ART) in people living with HIV (PLWH) has improved life expectancy and increased risk of age-associated cardiometabolic comorbidities. At-risk alcohol use is more frequent among PLWH and increases the risk of health challenges. PLWH with at-risk alcohol use are more likely to meet criteria for prediabetes/diabetes and this is associated with impaired whole-body glucose-insulin dynamics.

METHODS

The Alcohol & Metabolic Comorbidities in PLWH: Evidence Driven Interventions Study (ALIVE-Ex Study, NCT03299205) is a longitudinal, prospective, interventional study to determine the effects of an aerobic exercise protocol on improving dysglycemia among PLWH with at-risk alcohol use. The intervention is a moderate intensity aerobic exercise protocol implemented 3 days per week for 10 weeks at the Louisiana State University Health Sciences Center-New Orleans. Participants who have a fasting blood glucose level between 94 and 125 mg/dl will be enrolled in the study. Oral glucose tolerance tests, fitness assessments, and skeletal muscle biopsies will be performed pre- and post-exercise intervention. The primary outcome is to determine whether the exercise protocol improves measures of whole-body glucose-insulin dynamics, cardiorespiratory fitness, and skeletal muscle metabolic and bioenergetic function. Secondary outcomes are to determine whether the exercise intervention improves cognitive function and overall quality of life. Results generated will demonstrate the effect of exercise on glycemic measures in PLWH with subclinical dysglycemia and at-risk alcohol use.

CONCLUSIONS

The proposed intervention will also have the potential to be scalable to promote lifestyle changes among PLWH, particularly in underserved communities.

Mitochondrial Dysfunction: At the Nexus between Alcohol-Associated Immunometabolic Dysregulation and Tissue Injury

Alcohol misuse, directly or indirectly as a result of its metabolism, negatively impacts most tissues, including four with critical roles in energy metabolism regulation: the liver, pancreas, adipose, and skeletal muscle. Mitochondria have long been studied for their biosynthetic roles, such as ATP synthesis and initiation of apoptosis. However, current research has provided evidence that mitochondria participate in myriad cellular processes, including immune activation, nutrient sensing in pancreatic β-cells, and skeletal muscle stem and progenitor cell differentiation. The literature indicates that alcohol impairs mitochondrial respiratory capacity, promoting reactive oxygen species (ROS) generation and disrupting mitochondrial dynamics, leading to dysfunctional mitochondria accumulation. As discussed in this review, mitochondrial dyshomeostasis emerges at a nexus between alcohol-disrupted cellular energy metabolism and tissue injury. Here, we highlight this link and focus on alcohol-mediated disruption of immunometabolism, which refers to two distinct, yet interrelated processes. Extrinsic immunometabolism involves processes whereby immune cells and their products influence cellular and/or tissue metabolism. Intrinsic immunometabolism describes immune cell fuel utilization and bioenergetics that affect intracellular processes. Alcohol-induced mitochondrial dysregulation negatively impacts immunometabolism in immune cells, contributing to tissue injury. This review will present the current state of literature, describing alcohol-mediated metabolic and immunometabolic dysregulation from a mitochondrial perspective.

Alcohol use, physical activity, and muscle strength moderate the relationship between body composition and frailty risk among people living with HIV

BACKGROUND

Antiretroviral therapy has improved life expectancy among people living with HIV (PLWH). Despite increased longevity, PLWH are at increased risk of age-related comorbidities, including frailty. We examined the relationship between body composition and frailty among PLWH, and moderation of this relationship by substance use, physical activity (PA), and physical function.

METHODS

Participants (n = 341; 71% male, 48 ± 10 years, body mass index (BMI) = 27.3 ± 7.0 kg/m2 ) enrolled in the New Orleans Alcohol Use in HIV (NOAH) study underwent measures of body composition, muscle strength, and gait speed. Whole blood phosphatidylethanol (PEth) was measured, and substance use and PA were self-reported. Frailty risk measures included the 58-Item Deficit Index (DI58) and the Veterans Aging Cohort Study (VACS) Index 1.0, where higher scores indicate greater frailty risk.

RESULTS

Multivariable linear regression adjusted for age, sex, and race showed that higher fat-free mass index (FFMI), body fat (%), waist-to-hip ratio, and body mass index (BMI) ≥ 25.0 kg/m2 vs. < 25.0 kg/m2 were significantly (p < 0.05) associated with decreased frailty risk measured by the VACS Index, whereas adjusted analyses showed no association between body composition variables and the DI58 score. Recent alcohol use, muscle strength, and PA, but not lifetime alcohol use or gait speed, significantly moderated associations between body composition variables and frailty risk with medium-to-large effect sizes. Subgroup analyses revealed a negative relationship between DI58 and FFMI among people with PEth > 8 ng/ml and negative relationships of VACS Index with FFMI and WHR in people with lower muscle strength. Overweight or obese BMI categories were positively associated with DI58 in people with lower muscle strength or higher PA level but negatively associated in those with higher muscle strength.

CONCLUSIONS

Our findings indicate that body composition has significant modulatory effects on frailty risk in PLWH, where obesity increases the risk of frailty and greater muscle mass may be protective, even in individuals who use alcohol. These results highlight the importance of considering body composition, physical activity, and physical function in assessing frailty risk in PLWH, particularly among individuals who use alcohol. Moreover, they support the implementation of physical activity interventions to ameliorate the risk of frailty in aging PLWH.

Cellular Bioenergetics: Experimental Evidence for Alcohol-induced Adaptations

At-risk alcohol use is associated with multisystemic effects and end-organ injury, and significantly contributes to global health burden. Several alcohol-mediated mechanisms have been identified, with bioenergetic maladaptation gaining credence as an underlying pathophysiological mechanism contributing to cellular injury. This evidence-based review focuses on the current knowledge of alcohol-induced bioenergetic adaptations in metabolically active tissues: liver, cardiac and skeletal muscle, pancreas, and brain. Alcohol metabolism itself significantly interferes with bioenergetic pathways in tissues, particularly the liver. Alcohol decreases states of respiration in the electron transport chain, and activity and expression of respiratory complexes, with a net effect to decrease ATP content. In addition, alcohol dysregulates major metabolic pathways, including glycolysis, the tricarboxylic acid cycle, and fatty acid oxidation. These bioenergetic alterations are influenced by alcohol-mediated changes in mitochondrial morphology, biogenesis, and dynamics. The review highlights similarities and differences in bioenergetic adaptations according to tissue type, pattern of (acute vs. chronic) alcohol use, and energy substrate availability. The compromised bioenergetics synergizes with other critical pathophysiological mechanisms, including increased oxidative stress and accelerates cellular dysfunction, promoting senescence, programmed cell death, and end-organ injury.

Chronic Binge Alcohol and Ovarian Hormone Loss Dysregulate Circulating Immune Cell SIV Co-Receptor Expression and Mitochondrial Homeostasis in SIV-Infected Rhesus Macaques

Effective antiretroviral therapy (ART) has transitioned HIV to a chronic disease, with more than 50% of people living with HIV (PLWH) being over the age of 50. HIV targets activated CD4+ T cells expressing HIV-specific co-receptors (CCR5 and CXCR4). Previously, we reported that chronic binge alcohol (CBA)-administered male rhesus macaques had a higher percentage of gut CD4+ T cells expressing simian immunodeficiency virus (SIV) co-receptor CXCR4. Evidence also suggests that gonadal hormone loss increased activated peripheral T cells. Further, mitochondrial function is critical for HIV replication and alcohol dysregulates mitochondrial homeostasis. Hence, we tested the hypothesis that CBA and ovariectomy (OVX) increase circulating activated CD4+ T cells expressing SIV co-receptors and dysregulate mitochondrial homeostasis in SIV-infected female rhesus macaques. Results showed that at the study end-point, CBA/SHAM animals had increased peripheral CD4+ T cell SIV co-receptor expression, and a lower CD4+ T cell count compared to CBA/OVX animals. CBA and OVX animals had altered peripheral immune cell gene expression important for maintaining mitochondrial homeostasis. These results provide insights into how at-risk alcohol use could potentially impact viral expression in cellular reservoirs, particularly in SIV-infected ovariectomized rhesus macaques.

Alcohol Impairs Immunometabolism and Promotes Naïve T Cell Differentiation to Pro-Inflammatory Th1 CD4+ T Cells

CD4+ T cell differentiation to pro-inflammatory and immunosuppressive subsets depends on immunometabolism. Pro-inflammatory CD4+ subsets rely on glycolysis, while immunosuppressive Treg cells require functional mitochondria for their differentiation and function. Previous pre-clinical studies have shown that ethanol (EtOH) administration increases pro-inflammatory CD4+ T cell subsets; whether this shift in immunophenotype is linked to alterations in CD4+ T cell metabolism had not been previously examined. The objective of this study was to determine whether ethanol alters CD4+ immunometabolism, and whether this affects CD4+ T cell differentiation. Naïve human CD4+ T cells were plated on anti-CD3 coated plates with soluble anti-CD28, and differentiated with IL-12 in the presence of ethanol (0 and 50 mM) for 3 days. Both Tbet-expressing (Th1) and FOXP3-expressing (Treg) CD4+ T cells increased after differentiation. Ethanol dysregulated CD4+ T cell differentiation by increasing Th1 and decreasing Treg CD4+ T cell subsets. Ethanol increased glycolysis and impaired oxidative phosphorylation in differentiated CD4+ T cells. Moreover, the glycolytic inhibitor 2-deoxyglucose (2-DG) prevented the ethanol-mediated increase in Tbet-expressing CD4+ T cells but did not attenuate the decrease in FOXP3 expression in differentiated CD4+ T cells. Ethanol increased Treg mitochondrial volume and altered expression of genes implicated in mitophagy and autophagosome formation (PINK1 and ATG7). These results suggest that ethanol impairs CD4+ T cell immunometabolism and disrupts mitochondrial repair processes as it promotes CD4+ T cell differentiation to a pro-inflammatory phenotype.

A review of alcohol-pathogen interactions: New insights into combined disease pathomechanisms

Progression of chronic infections to end-stage diseases and poor treatment results are frequently associated with alcohol abuse. Alcohol metabolism suppresses innate and adaptive immunity leading to increased viral load and its spread. In case of hepatotropic infections, viruses accelerate alcohol-induced hepatitis and liver fibrosis, thereby promoting end-stage outcomes, including cirrhosis and hepatocellular carcinoma (HCC). In this review, we concentrate on several unexplored aspects of these phenomena, which illustrate the combined effects of viral/bacterial infections and alcohol in disease development. We review alcohol-induced alterations implicated in immunometabolism as a central mechanism impacting metabolic homeostasis and viral pathogenesis in Simian immunodeficiency virus/human immunodeficiency virus infection. Furthermore, in hepatocytes, both HIV infection and alcohol activate oxidative stress to cause lysosomal dysfunction and leakage and apoptotic cell death, thereby increasing hepatotoxicity. In addition, we discuss the mechanisms of hepatocellular carcinoma and tumor signaling in hepatitis C virus infection. Finally, we analyze studies that review and describe the immune derangements in hepatotropic viral infections focusing on the development of novel targets and strategies to restore effective immunocompetency in alcohol-associated liver disease. In conclusion, alcohol exacerbates the pathogenesis of viral infections, contributing to a chronic course and poor outcomes, but the mechanisms behind these events are virus specific and depend on virus-alcohol interactions, which differ among the various infections.