Skeletal muscle mitochondrial dysfunction in contemporary antiretroviral therapy: a single cell analysis

Interactions of mitochondrial and skeletal muscle biology in mitochondrial myopathy

Mitochondrial dysfunction in skeletal muscle fibres occurs with both healthy aging and a range of neuromuscular diseases. The impact of mitochondrial dysfunction in skeletal muscle and the way muscle fibres adapt to this dysfunction is important to understand disease mechanisms and to develop therapeutic interventions. Furthermore, interactions between mitochondrial dysfunction and skeletal muscle biology, in mitochondrial myopathy, likely have important implications for normal muscle function and physiology. In this review, we will try to give an overview of what is known to date about these interactions including metabolic remodelling, mitochondrial morphology, mitochondrial turnover, cellular processes and muscle cell structure and function. Each of these topics is at a different stage of understanding, with some being well researched and understood, and others in their infancy. Furthermore, some of what we know comes from disease models. Whilst some findings are confirmed in humans, where this is not yet the case, we must be cautious in interpreting findings in the context of human muscle and disease. Here, our goal is to discuss what is known, highlight what is unknown and give a perspective on the future direction of research in this area.

Hepatic Steatosis and Weight Gain During the Coronavirus Disease 2019 Pandemic Among People With Human Immunodeficiency Virus: Impact of Therapy With Tenofovir Alafenamide

Background

Lockdown due to the coronavirus disease 2019 (COVID-19) pandemic led to increases in weight in part of the population. Weight gain leads to hepatic steatosis (HS). Antiretroviral treatment could also influence HS in people with human immunodeficiency virus (PWH). The impact of lockdown on HS in PWH is unknown. The aim of this study was to analyze the changes in HS, as measured by the controlled attenuation parameter (CAP), during the COVID-19 pandemic in PWH.

Methods

This was a cohort study that included PWH who attended a tertiary care center in southern Spain from January 2018 to December 2021. The CAP was evaluated by transient elastography. Only those who had a valid CAP before and after March 2020 were included. HS was defined as CAP ≥248 dB/m.

Results

Six hundred eighty PWH were attended and 488 (71.8%) were included. Two hundred and fourteen (43.9%) had HS at baseline and 239 (49%) at the end of the follow-up (P = .036). The median change in CAP among PWH taking tenofovir alafenamide (TAF) was 8.5 (interquartile range [IQR], -24 to 46.3) dB/m versus -4 (IQR, -35 to 27) dB/m among PWH receiving TAF-free regimens (P = .003). After multivariate analysis, adjusted by sex and age, weight gain (adjusted odds ratio [AOR], 1.09 [95% confidence interval {CI}, 1.05-1.14]; P < .001), TAF therapy (AOR, 1.59 [95% CI, 1.07-2.35]; P = .021), plasma triglycerides (AOR, 1.01 [95% CI, 1-1.01]; P < .001), and fasting blood glucose (AOR, 1.01 [95% CI, 1-1.02]; P = .027) were associated with HS at the end of follow-up.

Conclusions

The frequency of HS increased during the COVID-19 pandemic among PWH. TAF is associated with HS development, regardless of metabolic factors.

The kynurenine pathway in HIV, frailty and inflammaging

Kynurenine (Kyn) is a circulating tryptophan (Trp) catabolite generated by enzymes including IDO1 that are induced by inflammatory cytokines such as interferon-gamma. Kyn levels in circulation increase with age and Kyn is implicated in several age-related disorders including neurodegeneration, osteoporosis, and sarcopenia. Importantly, Kyn increases with progressive disease in HIV patients, and antiretroviral therapy does not normalize IDO1 activity in these subjects. Kyn is now recognized as an endogenous agonist of the aryl hydrocarbon receptor, and AhR activation itself has been found to induce muscle atrophy, increase the activity of bone-resorbing osteoclasts, decrease matrix formation by osteoblasts, and lead to senescence of bone marrow stem cells. Several IDO1 and AhR inhibitors are now in clinical trials as potential cancer therapies. We propose that some of these drugs may be repurposed to improve musculoskeletal health in older adults living with HIV.