Aerobic training increases mitochondrial respiratory capacity in human skeletal muscle stem cells from sedentary individuals

The impact of aerobic training on human skeletal muscle cell (HSkMC) mitochondrial metabolism is a significant research gap, critical to understanding the mechanisms by which exercise augments skeletal muscle metabolism. We therefore assessed mito-chondrial content and capacity in fully differentiated CD56(+) thorn HSkMCs from lean active (LA) and sedentary individuals with obe-sity (OS) at baseline, as well as lean/overweight sedentary individuals (LOS) at baseline and following an 18-day aerobic training intervention. Participants had in vivo skeletal muscle PCr recovery rate by P-31-MRS (mitochondrial oxidative kinetics) and cardior-espiratory fitness (VO2max) assessed at baseline. Biopsies of the vastus lateralis were performed for the isolation of skeletal mus-cle stem cells. LOS individuals repeated all assessments posttraining. HSkMCs were evaluated for mitochondrial respiratory capacity by high-resolution respirometry. Data were normalized to two indices of mitochondrial content (CS activity and OXPHOS protein expression) and a marker of total cell count (quantity of DNA). LA individuals had significantly higher VO2max than OS and LOS-Pre training; however, no differences were observed in skeletal muscle mitochondrial capacity, nor in carbohy- drate-or fatty acid-supported HSkMC respiratory capacity. Aerobic training robustly increased in vivo skeletal muscle mitochon-drial capacity of LOS individuals, as well as carbohydrate-supported HSkMC respiratory capacity. Indices of mitochondrial content and total cell count were similar among the groups and did not change with aerobic training. Our findings demonstrate that bioenergetic changes induced with aerobic training in skeletal muscle in vivo are retained in HSkMCs in vitro without impacting mitochondrial content, suggesting that training improves intrinsic skeletal muscle mitochondrial capacity.

Automated summary

This study assessed the impact of aerobic training on mitochondrial metabolism of human skeletal muscle cells, and found that aerobic training can improve skeletal muscle mitochondrial capacity without affecting mitochondrial content.