Skeletal muscle is the main consumer of glucose after a mixed meal, and resistance exercise further increases muscle glucose uptake. Emerging evidence suggests that glucose uptake in muscles is not only stored as glycogen or used as a fuel but can also be incorporated into other biomass during growth. We aimed to study the utilization of glucose-derived carbons for protein, RNA, and lipid synthesis during human skeletal muscle (HSkM) cell growth. We also investigated whether muscle growth in vivo by resistance training (RT) affects the abundance of metabolites and enzymes required for these processes in human muscle. We found that differentiated HSkM cells incorporated glucose-derived carbon into proteins, RNA, and lipids, and anabolic stimulation further increased these processes. Liquid chromatography-mass spectrometry metabolomics and proteomics revealed that 10 weeks of RT in humans increased essential metabolites and enzymes for nucleotide, serine, and glycine synthesis, including phosphoglycerate dehydrogenase (PHGDH) in muscle. We also examined whether the PHGDH enzyme, starting the serine synthesis pathway branching from glycolysis, is sufficient and essential for human muscle protein, RNA, and lipid anabolism. We found that PHGDH inhibitors decreased protein synthesis and glucose-derived carbon incorporation into macromolecules, whereas manipulation of PHGDH abundance had mixed effects. Moreover, PHGDH was revealed to be important for myogenesis. The data suggest that glucose is not only used for ATP generation but also as a building block in human muscle cell growth. The results open new avenues for studies investigating the mechanisms of RT and muscle growth in improving muscle glucose metabolism.

Cells use glycolytic intermediates for anabolism, e.g., via the serine synthesis and pentose phosphate pathways. However, we still understand poorly how these metabolic pathways contribute to skeletal...