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

OBJECTIVE: To quantify mitochondrial function in skeletal muscle of people treated with contemporary anti-retroviral therapy. DESIGN: Cross-sectional observational study. METHODS: Quantitative multiplex immunofluorescence was performed to determine mitochondrial mass and respiratory chain complex abundance in individual myofibres from tibialis anterior biopsies. Individual myofibres were captured by laser microdissection and mitochondrial DNA (mtDNA) content and large-scale deletions were measured by real-time PCR. RESULTS: 45 anti-retroviral therapy (ART) treated people with HIV (PWH, mean age 58 years, mean duration of ART 125 months) were compared with 15 HIV negative age-matched controls. Mitochondrial complex I (CI) deficiency was observed at higher proportional levels in PWH than negative controls (p 0.008). Myofibre mitochondrial mass did not differ by HIV status. No ART class was significantly associated with mitochondrial deficiency, including prior exposure to historical NRTIs (nucleoside analogue reverse transcriptase inhibitors) associated with systemic mitochondrial toxicity. To exclude an effect of untreated HIV, we also studied skeletal muscle from 13 ART-naïve PWH (mean age 37). These showed negligible CI defects, as well as comparable myofibre mitochondrial mass to ART-treated PWH. Most CI-deficient myofibres contained mtDNA deletions. No mtDNA depletion was detected. CONCLUSION: Here we show that PWH treated with contemporary ART have mitochondrial dysfunction in skeletal muscle, exceeding that expected due to age alone. Surprisingly, this was not mediated by prior exposure to mitochondrially toxic NRTIs, suggesting novel mechanisms of mitochondrial dysfunction in contemporary ART-treated PWH. These findings are relevant for better understanding successful ageing in PWH.