Metabolomic and Lipidomic Signature of Skeletal Muscle with Constitutively Active mTORC1

Regulation of mTORC1 plays an important role in aging and nutrition. For example, caloric restriction reduces mTORC1 signaling and extends lifespan, whereas nutrient abundance and obesity increase mTORC1 signaling and reduce lifespan. Skeletal muscle specific knockout of DEP domain-containing 5 protein (DEPDC5) results in constitutively active mTORC1 signaling, muscle hypertrophy and an increase in mitochondrial respiratory capacity. The metabolic profile of skeletal muscle, in the setting of hyperactive mTORC1 signaling, is not well known. To determine the metabolomic and lipidomic signature in skeletal muscle from female and male wildtype and DEPDC5 knockout mice. Tibialis anterior (TA) muscles from wildtype (WT) and transgenic (conditional skeletal muscle specific DEPDC5 knockout, KO) were obtained from female (F) and male (M) adult mice. Polar metabolites and lipids were extracted using a Bligh-Dyer extraction from 5 samples per group and identified and quantified by LC-MS/MS. Resulting analyte peak areas were analyzed with t-test, ANOVA, and volcano plots for group comparisons (e.g., WT vs KO) and multivariate statistical analysis for genotype and sex comparisons. A total of 162 polar metabolites (organic acids, amino acids and amines and acyl carnitines) and 1141 lipid metabolites were detected in TA samples by LC-MS/MS. Few polar metabolites showed significant differences in KO muscles compared to WT within the same sex group. P-aminobenzoic acid, β-alanine and dopamine were significantly higher in KO male muscle whereas erythrose- 4-phosphate and oxoglutaric acid were significantly reduced in KO females. The lipidomic profile of the KO groups revealed an increase of muscle phospholipids and reduced triacylglycerol and diacylglycerol compared to the WT groups. Sex differences were detected in polar metabolome and lipids were dependent on genotype. Metabolomic profile of mice with hyperactive skeletal muscle mTORC1 is consistent with an upregulation of mitochondrial function and amino acid utilization for protein synthesis.