Skeletal muscle-specific over-expression of the nuclear sirtuin SIRT6 blocks cancer-associated cachexia by regulating multiple targets

Unlocking the Nexus of Sirtuins: A Comprehensive Review of Their Role in Skeletal Muscle Metabolism, Development, and Disorders

The sirtuins constitute a group of histone deacetylases reliant on NAD+ for their activity that have gained recognition for their critical roles as regulators of numerous biological processes. These enzymes have various functions in skeletal muscle biology, including development, metabolism, and the body's response to disease. This comprehensive review seeks to clarify sirtuins' complex role in skeletal muscle metabolism, including glucose uptake, fatty acid oxidation, mitochondrial dynamics, autophagy regulation, and exercise adaptations. It also examines their critical roles in developing skeletal muscle, including myogenesis, the determination of muscle fiber type, regeneration, and hypertrophic responses. Moreover, it sheds light on the therapeutic potential of sirtuins by examining their impact on a range of skeletal muscle disorders. By integrating findings from various studies, this review outlines the context of sirtuin-mediated regulation in skeletal muscle, highlighting their importance and possible consequences for health and disease.

Single nuclei profiling identifies cell specific markers of skeletal muscle aging, frailty, and senescence

Aging is accompanied by a loss of muscle mass and function, termed sarcopenia, which causes numerous morbidities and economic burdens in human populations. Mechanisms implicated in age-related sarcopenia or frailty include inflammation, muscle stem cell depletion, mitochondrial dysfunction, and loss of motor neurons, but whether there are key drivers of sarcopenia are not yet known. To gain deeper insights into age-related muscle loss, we performed transcriptome profiling on lower limb muscle biopsies from 72 young, elderly, and frail human subjects using bulk RNA-seq (N = 72) and single-nuclei RNA-seq (N = 17). This combined approach revealed changes in gene expression that occur with age and frailty in multiple cell types comprising mature skeletal muscle. Notably, we found increased expression of the genes MYH8 and PDK4, and decreased expression of the gene IGFN1, in aged muscle. We validated several key genes changes in fixed human muscle tissue using digital spatial profiling. We also identified a small population of nuclei that express CDKN1A, present only in aged samples, consistent with p21cip1-driven senescence in this subpopulation. Overall, our findings identify unique cellular subpopulations in aged and sarcopenic skeletal muscle, which will facilitate the development of new therapeutic strategies to combat age-related frailty.