11/01/2023
Before answering this question, we highlight a key difference in terms of anabolism between proliferating cells and hypertrophying muscle fibres. Proliferating cells need to replicate their entire genome during each cell cycle. This means that each proliferating human cell will synthesise 6.4 billion nucleotides plus nucleotides for mRNA and ribosomal biogenesis before dividing into two daughter cells. In contrast, a hypertrophying muscle fibre “only” synthesises nucleotides for mRNA and ribosome biogenesis [16] as it has “outsourced” replication and the generation of new myonuclei to proliferating satellite cells. The fact that ribose, the pentose sugar in RNA, and deoxyribose, the pentose sugar in DNA, are primarily synthesised from glucose [17] is one reason for why proliferating cells take up more glucose. However, the ribosome biogenesis of hypertrophying muscle fibres [16] will also require glucose to synthesise the nucleotides and rRNA from which ribosomes are made. Hosios et al. have directly compared the contribution of radioactive or stable isotope tracers such as 14C/13C-glucose or 14C/13C-glutamine to the cell mass of proliferating C2C12 myoblasts and differentiated C2C12 myotubes [10]. They found that glucose and glutamine contributed 15% and 8% to cell mass in proliferating C2C12 myoblasts in a steady state and 6% and 3% to cell mass in differentiated but not hypertrophy-stimulated C2C12 myotubes after 6 days of incubation, respectively [10]. In summary, proliferating and hypertrophying cells both generate biomass via anabolic reactions but only proliferating cells synthesise DNA for replication.