The Anti‐Retroviral Therapy Emtricitabine Affects Skeletal Muscle DNA Methylation and Transcriptome Patterns in a Male HIV Mouse Model

ABSTRACT Background Although antiretroviral therapies (ART) have substantially reduced HIV‐associated mortality, HIV infection is still linked to an unexplained earlier onset and increased incidence of aging‐associated conditions like sarcopenia that negatively impact healthspan. Complex syndromes, like sarcopenia, often arise from a combination of genetic and environmental factors, so in this study, we investigated effects of short‐term treatment with emtricitabine (2′,3′‐dideoxy‐5‐fluoro‐3′‐thiacytidine; FTC), an FDA‐approved ART, on skeletal muscle DNA methylation patterns and transcriptome‐wide responses in a male murine model of HIV phenotypic biology (Tg26 mice). Methods We treated 6‐month‐old male Tg26 (+/−) mice or wildtype (WT) littermates on a C57BL/6 genetic background with FTC in the drinking water for 1 month; control groups received drinking water vehicle alone (VEH). Muscle function and body composition were measured longitudinally. Skeletal muscle methylation patterns, transcriptional changes and histological features were quantified at sacrifice. Results Although neither gross structural nor functional muscle deficits were observed in this short‐term study with ART usage, relative decreases in muscle endurance measured by hang time over the study were twofold more severe in the Tg26 as compared to WT mice ( p = 0.0453), and markers of myogenic cell maturation ( Myf5, Myf6 ) were disrupted in the Tg26 HIV model as compared to WT littermates in a manner exacerbated by FTC treatment. Fat mass, measured by DXA, also tended ( p = 0.085) to be uniquely increased by FTC treatment in the Tg26 mice over the study. Differential methylation patterns and pathway enrichment data suggested that the presence of an HIV phenotype and exposure to an FTC regimen altered the methylation status in skeletal muscle genes such as Camk2B, Pcolce2 and Lima1 in a manner consistent with promoting eventual functional impairment in muscle. Additionally, RNAseq revealed differential gene expression profiles and key regulatory pathways including cellular differentiation, regulation of lipid metabolism and neuroactive ligand‐receptor interactions. Lipodystrophy‐related genes including Lep and Adipoq involved in fat distribution and metabolism along with skeletal genes related to regulation of muscle strength were affected by the presence of an HIV phenotype and ART treatment. Conclusions The current study provides insights into mechanisms by which a clinically relevant ART may influence DNA methylation and transcriptome changes in skeletal muscle in the context of HIV biology. The differentially regulated pathways suggest novel targets for understanding and eventually abrogating the harmful effects of long‐term ART use in people living with HIV (PLWH) on skeletal muscle mass and function.