LOOH-induced muscle atrophy with age

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Project Summary (From the Parent Grant AG074535) Maintenance of skeletal muscle mass is essential for healthy aging and plays a significant role in quality of life. Age-induced skeletal muscle atrophy (sarcopenia) not only reduces mobility but also increases the propensity to develop metabolic and cardiovascular diseases. Although skeletal muscle atrophy has broad clinical impact in the increasingly sedentary and aging population, a pharmacologic therapy for muscle mass loss does not exist. Reactive oxygen species (ROS) likely induce muscle atrophy by accelerating proteolysis and depressing protein synthesis. However, ROS refers to a collection of radical molecules whose cellular signals are vast, and it is unclear which of the downstream consequences of oxidative stress are responsible for the loss of muscle mass and function that occurs with age or disuse. In this application, we will test our hypothesis that lipid ROS (LOOH) promotes muscle atrophy through accelerating autophagy/lysosome-dependent protein degradation. 1) Cellular LOOH is neutralized by phospholipid hydroperoxidase (GPx4), preventing its accumulation and degradation to form reactive lipid aldehydes. We will determine whether neutralization of LOOH by N-acetylcarnosine treatment (lipid aldehyde scavenger) will suppress age and/or disuse-induced skeletal muscle atrophy. 2) Suppression of polyunsaturated fatty acid (PUFA) incorporation by lysophosphatidylcholine acyltransferase-3 (LPCAT3) inhibition prevents LOOH-induced cell death. We will investigate whether LPCAT3 deletion can protect mice from muscle atrophy, and perform subcellular fluxomics to examine intracellular fate of LPCAT3 product during oxidative stress. 3) GPx4 deletion increases protein degradation by accelerating lysosomal degradation. We will test our hypothesis that LOOH supercharges autophagic machinery by its lipidation with LC3.