Novel effects of reverse transcriptase inhibitor supplementation in skeletal muscle of old mice

Abstract

Aging is the primary risk factor for the development of many chronic diseases, including dementias, cardiovascular disease, and diabetes. There is significant interest in identifying novel "geroprotective" agents, including by repurposing existing drugs, but such treatments may affect organ systems differently. One current example is the nucleoside reverse transcriptase inhibitor 3TC, which has been increasingly studied as a potential gerotherapeutic. Recent data suggest that 3TC may reduce inflammation and improve cognitive function in older mice; however, the effects of 3TC on other tissues in aged animals are less well characterized. Here, we use transcriptomics (RNA-seq) and targeted metabolomics to investigate the influence of 3TC supplementation on skeletal muscle in older mice. We show that 3TC 1) does not overtly affect muscle mass or functional/health markers, 2) largely reverses age-related changes in gene expression and metabolite signatures, and 3) is potentially beneficial for mitochondrial function in old animals via increases in antioxidant enzymes and decreases in mitochondrial reactive oxygen species. Collectively, our results suggest that, in addition to its protective effects in other tissues, 3TC supplementation does not have adverse effects in aged muscle and may even protect muscle/mitochondrial health in this context.NEW & NOTEWORTHY Recent studies suggest that the nucleoside reverse transcriptase inhibitor 3TC may improve brain health and cognitive function in old mice, but its effects on other aging tissues have not been comprehensively studied. This is the first study to use a multiomics approach to investigate the effects of 3TC treatment on skeletal muscle of old mice. The results suggest that 3TC reverses age-related transcriptomic and metabolite signatures and is potentially beneficial for mitochondrial function in aged muscle.

Keywords: aging; metabolomics; mitochondria; skeletal muscle; transcriptomics.

Figure 1.. 3TC modulates the muscle transcriptome.

(a) MA plot of gene expression differences in muscle of old vs. young mice. (b) Gene ontology analyses of significantly differentially expressed genes with age. (c) MA plot of gene expression difference in muscle of 3TC-treated old mice vs. old controls. (d and e) Top 100 genes/transcripts increased and decreased with aging and their relative changes with 3TC treatment in old animals. (f and g) Relative expression of genes associated with interferon response and mitochondria, respectively, in old vs. young and old 3TC-treated vs. control animals. n=6/group (3m/3f).

Figure 2.. 3TC modulates the muscle metabolome.

(a) 3TC levels in muscle of young, old and 3TC-treated old mice. (b) Log2 fold metabolite differences in the same tissue samples. (c) Heatmap showing relative effects of aging and 3TC treatment on muscle metabolites (note that differences with aging are largely reversed with 3TC treatment). (d) Pathway analysis of metabolites reversed with 3TC treatment. n=6/group (3m/3f).

Figure 3.. Effects of 3TC on markers of mitochondrial health.

(a) Western blot images and (b-d) quantifications of Total OXPHOS, VDAC1, and Catalase protein levels in young, old and 3TC-treated old mice. Data displayed as fold change relative to young reference group and presented as means ± standard deviation. Lines in the blot images are an artifact from an older camera/imaging system. (e) Mitochondrial ROS levels in the same groups of mice as analyzed by EPR. Closed circles represent females, open circles represent males. n=6/group (3m/3f).

Figure 4.. GWENA network analysis of transcriptome data.

(a) Number of genes per module from GWENA output. (b) heat map of gene module correlations with functional measures and protein expression (Western blot) levels. (c) Gene ontology analysis of genes within module 8. (d) Log2 fold differences of genes in module 8 in old vs. young, and 3TC-treated vs. old control mice. (e) Gene ontology analysis of genes within module 8 that were increased with 3TC treatment.