Project description:Microgravity and prolonged periods of inactivity cause a variety of diseases, including skeletal muscle mass loss and weakening as well as cardiovascular deconditioning. The primary causes of the inadequate preventative measures for these deconditionings are the lack of biomarkers and unknown underlying mechanisms of cardiovascular and skeletal muscle deconditioning in these conditions. Here, we used a hindlimb unloading (HU) mouse model that replicates astronauts in space and bedridden patients to first evaluate cardiovascular and skeletal muscle performance. Serum samples from these mice were used to identify new biomarkers using metabolomic and proteomic approaches. Three weeks of unloading resulted in alterations in cardiovascular system function in C57/Bl6 mice, as measured by changes in mean arterial pressure and heart weight. Unloading for three weeks also altered skeletal muscle function, resulting in a decrease of grip strength in HU mice, as well as skeletal muscle atrophy, as shown by a drop in muscle mass. A two-week recovery time from the unloading condition partially reversed these alterations, stressing the importance of the recovery process.
Project description:To investigate the possible changes of genes expression during muscle atrophy, we performed bulk RNA-seq of skeletal muscle from C57 BL/6 mice with or without denervation (2 weeks).
Project description:Calorie restriction (CR) is a dietary intervention that extends lifespan and healthspan in a variety of organisms. CR improves mitochondrial energy production, fuel oxidation and reactive oxygen species scavenging in skeletal muscle and other tissues, and these processes are thought to be critical to the benefits of CR. PGC-1a is a transcriptional coactivator that regulates mitochondrial function and is induced by CR. Consequently, many of the mitochondrial and metabolic benefits of CR are attributed to increased PGC-1a activity. To test this model for the first time, we examined the metabolic and mitochondrial response to CR in mice lacking skeletal muscle PGC-1a (MKO). Surprisingly, MKO mice demonstrated a normal improvement in glucose homeostasis in response to CR, indicating that skeletal muscle PGC-1a is dispensable for the whole-body benefits of CR. In contrast, gene expression profiling and electron microscopy demonstrated that PGC-1a is required for the full CR-induced increases in mitochondrial gene expression and mitochondrial density in skeletal muscle. These results demonstrate that PGC-1a is a major regulator of the mitochondrial response to CR in skeletal muscle, but surprisingly show that neither PGC-1a nor mitochondrial biogenesis in skeletal muscle are required for the metabolic benefits of CR. Control (FLOX) and PGC-1a skeletal muscle specific knock out (MKO) mice were placed on a control diet [C] or a calorie restriction diet [CR] for 12 weeks. RNA was isolated from TA/EDL muscles for microarray analysis. The following numbers of mice were analyzed from each group: C FLOX: n = 6; C MKO: n = 7; CR FLOX: n = 6; CR MKO: n = 7. Mice were mixed C57/BL6 and 129 background.
Project description:Skeletal muscle accounts for the largest proportion of human body mass, on average, and is a key tissue in complex diseases and mobility. It is composed of several different cell and muscle fiber types. Here, we optimize single-nucleus ATAC-seq (snATAC-seq) to map skeletal muscle cell-specific chromatin accessibility landscapes in frozen human and rat samples, and single-nucleus RNA-seq (snRNA-seq) to map cell-specific transcriptomes in human. We additionally perform multi-omics profiling (gene expression and chromatin accessibility) on human and rat muscle samples.
Project description:Gene transcription profiling in muscle following muscle versus normal diet in C57/Bl6 mice. Switched the diet when mice were 5 weeks old, then sampled at 8 days, 3 weeks and 15 weeks.
Project description:The Hippo signalling pathway effector Yap positively regulates adult skeletal muscle mass. However, the biological processes that are modulated by Yap in skeletal muscle remain elusive. Using an integrated transcriptomics and proteomics approach, we define the transcriptional programme regulated by Yap in adult skeletal muscle and demonstrate that Yap is a regulator of metabolic substrate utilisation. Inhibition of Yap in mammalian skeletal muscle results in increased, but incomplete, oxidation of fatty acids and features of lipotoxicity. In line with these findings, we demonstrate that Yap abundance is reduced in the skeletal musculature of obese db/db mice, and in muscle biopsies from obese, insulin-resistant humans where YAP levels positively correlate with whole-body metabolic flexibility. Increasing Yap abundance in the striated muscle of db/db mice attenuated the accumulation of fat mass and development of hepatic steatosis. Our findings demonstrate a vital role for Yap in skeletal muscle as a mediator of metabolic substrate utilisation. Modulating Yap activity in skeletal muscle warrants consideration as part of comprehensive approaches to treat metabolic disease.
