Myotube growth is associated with cancer-like metabolic reprogramming and is limited by phosphoglycerate dehydrogenase and pyruvate kinase M2

Abstract

Skeletal myofiber size and oxidative metabolism are inversely related. Glycolytic fast type myofibers are larger than high high oxidative, slow type myofibers. Paradoxically, despite their lower capacity for protein synthesis (lower myonucluar density and RNA content), glycolytic, low oxidative are more responsive to an anabolic stimulus. We hypothesized that glycolytic myofibers may make use of a Warburg-like metabolic reprogramming in response to an anabolic stimulus. The Warburg effect links growth and glycolysis in tumor cells to generate glycolytic intermediates for synthesis of nucleotides and amino. The aim of this study was to test whether a similar ‘glycolysis-for-anabolism’ metabolic reprogramming also occurs in post-mitotic, hypertrophying myofibers. For this purpose, we first induced C2C12 myotube hypertrophy with IGF-1. We then added 14C glucose to the differentiation medium and measured radioactivity in isolated protein and RNA to establish whether 14C had entered anabolism. We found that especially protein became radioactive, suggesting a glucose → glycolytic intermediates → non-essential amino acid(s) → protein series of reactions, the rate of which was increased by IGF-1. Next, to investigate the importance of glycolytic flux and non-essential amino acid synthesis for myotube hypertrophy, we exposed C2C12 and primary mouse myotubes to the glycolysis inhibitor 2-Deoxy-D-glucose (2DG). We found that inhibiting glycolysis lowered C2C12 and primary myotube size. Similarly, siRNA silencing of PHGDH and PKM2, key enzymes of the Warburg-like metabolic reprogramming, reduced C2C12 and primary myotube growth; whereas retroviral PHGDH overexpression increased C2C12 myotube size. Together these results suggest that glycolysis is important for hypertrophying myotubes, which reprogramme their metabolism to facilitate anabolism, similar to cancer cells. Brendan M. Gabriel was supported by fellowships from the Novo Nordisk Foundation (NNF19OC0055072) & the Wenner-Gren Foundation, an Albert Renold Travel Fellowship from the European Foundation for the Study of Diabetes, and an Eric Reid Fund for Methodology from the Biochemical Society. Abdalla D. Mohamed was funded initially by Sarcoma UK (grant number SUK09.2015), then supported by funding from Postdoctoral Fellowship Program (Helmholtz Zentrum München, Germany), and currently by Cancer Research UK. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.