Rapidly elevated levels of PGC-1α-b protein in human skeletal muscle after exercise: exploring regulatory factors in a randomized controlled trial

Individuals with high skeletal muscle mitochondrial content have a lower risk to acquire cardiovascular and metabolic disease, obesity, and type II diabetes. Regular endurance training increases mitochondrial density through a complex network of transcriptional regulators that in an accumulated way are affected by each single exercise bout. The aim of the present study was to investigate the effect of a single exercise bout on the levels of PGC-1 alpha and related regulatory factors important for the initial phase of skeletal muscle adaptation. Ten men and ten women were randomized to either an exercise group (60 min cycling at a work load corresponding to 70% of peak oxygen uptake) or a nonexercising control group. Skeletal muscle biopsies were taken before, at 30 min, and at 2, 6, and 24 h after the intervention. Twenty-two mRNA transcripts and five proteins were measured. With exercise, protein levels of PGC-1 alpha-ex1b increased, and this elevation occurred before that of total PGC-1 alpha protein. We also demonstrated the existence and postexercise expression pattern of two LIPIN-1 (LIPIN-1 alpha and LIPIN-1 beta) and three NCoR1 (NCoR1-1, NCoR1-2, and NCoR1-3) isoforms in human skeletal muscle. The present study contributes new insights into the initial signaling events following a single bout of exercise and emphasizes PGC-1 alpha-ex1b as the most exercise-responsive PGC-1 alpha isoform.