The Skeletal Muscle Metabolome Reflects Resistance Exercise-induced Skeletal Muscle Adaptation

Purpose: It is unknown how acute resistance exercise (RE) affects the human skeletal muscle metabolome and whether chronic RE will further change this response. Aim: To investigate the skeletal muscle metabolome acutely after a single RE session in the unadapted state and after a resistance training programme in the adapted state.
Methods: Six healthy male volunteers conducted 13 RE-bouts resistance training programme over five weeks. Vastus lateralis muscle biopsies were taken at rest, 45 min after the first and last bout of RE. Skeletal muscle metabolite levels were measured by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) following database-assisted metabolite annotation (Metabolon).
Results: We measured the relative abundance of 617 metabolites covering a broad range of metabolic pathways including protein breakdown, energy-, lipid- and nucleotide metabolism. While acute, unaccustomed RE changed the levels of 33 metabolites repeated RE training altered the concentration of 46 metabolites after RE in the trained state. During the study, slow type I and fast/intermediate type II muscle fibre diameter increased by 10.7% and 10.4%, respectively. Importantly, after RE we detected significant increases in the bile acid metabolite chenodeoxycholate and beta-citrylglutamate which support a growth-promoting environment in tissues. While we were able to support findings previously obtained in plasma, some results contradict those findings and emphasize a direct analysis of the skeletal muscle metabolome to be advantageous.
Conclusions: The skeletal muscle metabolome is sensitive towards acute RE in the trained and untrained state and partly reflects the adaptive process of skeletal muscle towards repeated stimulation.