Project description:Metabolic rewiring is a well-established feature of muscle cells and a hallmark of cancer. In isocitrate dehydrogenase 1 and 2 mutant tumors, increased production of the oncometabolite D-2-hydroxyglutarate (D2-HG) is associated with myopathy. The connection between metabolic changes and proteomic remodeling in skeletal muscle remains poorly understood. We demonstrate that D2-HG impairs NAD+ redox homeostasis in myocytes, causing activation of autophagy via de-acetylation of microtubule-associated protein 1 light chain 3-II (LC3-II) by the nuclear deacetylase Sirt1. We integrated multi-omics data from mice treated with D2-HG and demonstrate that autophagy activation leads to skeletal muscle atrophy and sex-dependent metabolic and proteomic remodeling. We also characterized protein and metabolite interactions linking energy-substrate metabolism with chromatin organization and autophagy regulation. Collectively, our multi-omics approach exposes mechanisms by which the oncometabolite D2-HG induces metabolic and proteomic remodeling in skeletal muscle, and provides a conceptual framework for identifying potential therapeutic targets in cachexia.
Project description:Autophagy is a critical process in the regulation of muscle mass, function and integrity. The molecular mechanisms regulating autophagy are complex and still partly understood. Here, we identify and characterize a novel FoxO-dependent gene, d230025d16rik which we named Mytho (Macroautophagy and YouTH Optimizer), as a regulator of autophagy and skeletal muscle integrity in vivo. Mytho is significantly up-regulated in various mouse models of skeletal muscle atrophy. Short term depletion of MYTHO in mice attenuates muscle atrophy caused by fasting, denervation, cancer cachexia and sepsis. While MYTHO overexpression is sufficient to trigger muscle atrophy, MYTHO knockdown results in a progressive increase in muscle mass associated with a sustained activation of the mTORC1 signaling pathway. Prolonged MYTHO knockdown is associated with severe myopathic features, including impaired autophagy, muscle weakness, myofiber degeneration, and extensive ultrastructural defects, such as accumulation of autophagic vacuoles and tubular aggregates. Inhibition of the mTORC1 signaling pathway in mice using rapamycin treatment attenuates the myopathic phenotype triggered by MYTHO knockdown. Skeletal muscles from human patients diagnosed with myotonic dystrophy type 1 (DM1) display reduced Mytho expression, activation of the mTORC1 signaling pathway and impaired autophagy, raising the possibility that low Mytho expression might contribute to the progression of the disease. We conclude that MYTHO is a key regulator of muscle autophagy and integrity.
Project description:MYTHO: a novel regulator of skeletal muscle autophagy and integrity mRNA expression data for the mouse muscle (n=4 per group) were obtained using Affymetrix Mouse Clariom S Assay (Affymetrix, Santa Carla, CA) according to the manufacturer’s recommendations.
Project description:Protein aggregates and cytoplasmic vacuolization are major hallmarks of multisystem proteinopathies (MSP) that lead to muscle weakness. Here, we identify METTL21C as a novel skeletal muscle-specific lysine methyltransferase. Insertion of a -galactosidase cassette into the Mettl21c mouse locus revealed METTL21C is specifically expressed in MYH7 positive skeletal muscle fibers. Ablation of the Mettl21c gene reduced endurance capacity and led to accumulation of cellular residuals due to incomplete autophagy in the skeletal muscle of Mettl21c-/- mutants during aging. Moreover, denervation-induced muscle atrophy highlighted further impairments of autophagy-related proteins, including LC3, p62, and cathepsins in Mettl21c-/- muscles. In addition, we demonstrate METTL21C interacts with the ATPase p97 (VCP), which is mutated in various human MSP conditions. We also reveal METTL21C trimethylates p97 on Lys315 residue, and found loss of this modification reduced p97 hexamer formation and ATPase activity in vivo. We conclude the methyltransferase METTL21C is an important modulator of protein degradation in skeletal muscle under both normal and enhanced protein breakdown conditions due to its ability to trimethylate and regulate p97.
Project description:Reducing circulating serotonin by inhibition of Tph1 increases the sensitivity of BAT cells and this drives thermogenesis by fat and glucose oxidation. Here we report Insulin sensitivity changes by regulating Serotonin on skeletal muscle. Improved glucose tolerance and insulin sensitivity in HFD Tph1 KO mice. Inhibiting Tph1 increases AMPK activity, glucose uptake, myofiber size and decreases lipid droplet accumulation in HFD mice skeletal muscle. Inhibiting Tph1 in muscle showed activation of SIRT1/LKB1/AMPK pathway in skeletal muscle cells and increased p-ACC. Theses results indicates that protected insulin resistance and myosteatosis on skeletal muscle by lack of Serotonin by Tph1 on skeletal muscle.
Project description:Utilizing glycerol intramuscular injections in M. musculus provide a models of skeletal muscle damage followed by skeletal muscle regeneration. In particular, glycerol-induced muscle injury triggers accute activation of skeletal muscle stem cells, called satellite cells. However, aging dramatically impairs the regenerative capacity of satellite cells. We characterized genome-wide expression profiles of young and old satellite cells in the non-proliferative and activated state, freshly isolated to non-injured or damaged muscles, respectively. Our goal was to uncover new regulatory signaling specific to satellite cells entry into the activation and myogenic program that are affected with age. Satellite cells were isolated in either quiescent / non-proliferative or activated state from uninjured or 3 days after glycerol-induced injury of tibialis anterior, gastrocnemius and quadriceps, respectively. Young (2-4 months old) and old (20-24 months old) wildtype C57BL/6J male were used, with five to six biological replicates per group.
Project description:Utilizing glycerol intramuscular injections in M. musculus provide a models of skeletal muscle damage followed by skeletal muscle regeneration. In particular, glycerol-induced muscle injury triggers accute activation of skeletal muscle stem cells, called satellite cells. However, aging dramatically impairs the regenerative capacity of satellite cells. We characterized genome-wide expression profiles of young and old satellite cells in the non-proliferative and activated state, freshly isolated to non-injured or damaged muscles, respectively. Our goal was to uncover new regulatory signaling specific to satellite cells entry into the activation and myogenic program that are affected with age.