Satellite Cells Exhibit Limited Alignment with Human Skeletal Muscle Metabolic Responses: Insights into Metabolic Memory

Satellite cells, specialized muscle stem cells, play a critical role in muscle growth and repair by contributing new nuclei to muscle fibers, though their involvement in muscle memory remains debated. While much research on satellite cells has focused on muscle growth and strength, less is known about their role in preserving and replicating muscle metabolic functions. This study investigates whether satellite cells retain memory of skeletal muscle metabolic functions by examining cells isolated from human muscle biopsies and comparing their metabolic capabilities to those of the original muscle tissue. This work explores how muscle memory may extend beyond growth to include glucose and lipid metabolic functions. Satellite cells were isolated from quadriceps muscle biopsies taken during a previous study on lipid metabolism and insulin sensitivity in relation to nutrient-exercise timing in healthy overweight participants (Edinburgh et al., 2020). Biopsies were collected from three participant groups: non-exercise control, exercise before breakfast, and breakfast before exercise, at baseline (PRE) and after six weeks of exercise training (POST). The satellite cells were cultured and differentiated into myotubes to assess insulin sensitivity via insulin-stimulated [3H]2-deoxy-glucose uptake. The assay results showed no clear changes in glucose uptake between PRE and POST, contrary to the reported improvement in post-prandial insulin sensitivity from the original study. To further investigate the susceptibility of differentiated myotubes to insulin resistance, satellite cells from the non-exercise control group were treated with 1 mM palmitate (PM) for 24 hours. Live-cell immunofluorescence staining with Nile Red revealed a 2–4 fold increase in lipid accumulation in myotubes, confirming PM-induced lipid stress. Insulin-stimulated glucose uptake was reduced under PM, indicating insulin resistance. Quantification of immunofluorescent staining of CD36, free fatty acid transporter, using Cell Profiler software showed a significant drop with PM in PRE (P < 0.05) but only a decreasing trend in POST, a result mirrored in CD36 protein levels via immunoblotting. Conversely, CPT1B staining showed no differences between conditions. Protein expression analysis revealed no significant differences in insulin signaling proteins (INSR, pINSR, Akt2, pAkt, AS160, pAS160, and GLUT4) across conditions. Mitochondrial respiration protein complexes (OXPHOS) showed slight variations between PRE and POST but deviated from expected metabolic responses in human muscle, where PRE and POST are typically consistent. These findings highlight challenges in translating systemic metabolic patterns to satellite cell-derived myotubes, potentially due to the simplified in vitro environment lacking systemic factors such as hormonal, neural, and circulatory interactions. The small sample size (n=1; 3 biological replicas) may have introduced variability and masked significant trends. Future studies should increase sample sizes and consider additional factors such as diet and exercise to better understand satellite cells' ability to replicate exercise training benefits. Further research into satellite cells’ potential to carry skeletal muscle memory could inform therapeutic strategies for muscle regeneration and metabolic health, particularly for exercise-driven metabolic adaptations. Reference Edinburgh, R.M., Bradley, H.E., Abdullah, N.F.,.. Gonzalez, J.T., 2020. Lipid Metabolism Links Nutrient-Exercise Timing to Insulin Sensitivity in Men Classified as Overweight or Obese. J Clin Endocrinol Metab, 105(3), pp. 660-676. J.B. is funded by Chulabhorn Royal Academy. F.K. and J.T.G. are funded by MRC UK. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.