Influence of divergent exercise contraction mode and whey protein supplementation on atrogin-1, MuRF1, and FOXO1/3A in human skeletal muscle

Knowledge from human exercise studies on regulators of muscle atrophy is lacking, but it is important to understand the underlying mechanisms influencing skeletal muscle protein turnover and net protein gain. This study examined the regulation of muscle atrophy–related factors, including atrogin-1 and MuRF1, their upstream transcription factors FOXO1 and FOXO3A and the atrogin-1 substrate eIF3-f, in response to unilateral isolated eccentric (ECC) vs. concentric (CONC) exercise and training. Exercise was performed with whey protein hydrolysate (WPH) or isocaloric carbohydrate (CHO) supplementation. Twenty-four subjects were divided into WPH and CHO groups and completed both single-bout exercise and 12 wk of training. Single-bout ECC exercise decreased atrogin-1 and FOXO3A mRNA compared with basal and CONC exercise, while MuRF1 mRNA was upregulated compared with basal. ECC exercise downregulated FOXO1 and phospho-FOXO1 protein compared with basal, and phospho-FOXO3A was downregulated compared with CONC. CON...