title: The truncated splice variants, NT-PGC-1α and PGC-1α4, increase with both endurance and resistance exercise in human skeletal muscle.
abstract: Recently, a truncated peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) splice variant, PGC-1α4, that originates from the alternative promoter was shown to be induced by resistance exercise and to elicit muscle hypertrophy without coactivation of "classical" PGC-1α targets involved in mitochondrial biogenesis and angiogenesis. In order to test if distinct physiological adaptations are characterized by divergent induction of PGC-1α splice variants, we investigated the expression of truncated and nontruncated PGC-1α splice variants and PGC-1α transcripts originating from the alternative and the proximal promoter, in human skeletal muscle in response to endurance and resistance exercise. Both total PGC-1α and truncated PGC-1α mRNA expression were increased 2 h after endurance (P < 0.01) and resistance exercise (P < 0.01), with greater increases after endurance exercise (P < 0.05). Expression of nontruncated PGC-1α increased significantly in both exercise groups (P < 0.01 for both groups) without any significant differences between the groups. Both endurance and resistance exercise induced truncated as well as nontruncated PGC-1α transcripts from both the alternative and the proximal promoter. Further challenging the hypothesis that induction of distinct PGC-1α splice variants controls exercise adaptation, both nontruncated and truncated PGC-1α transcripts were induced in AICAR-treated human myotubes (P < 0.05). Thus, contrary to our hypothesis, resistance exercise did not specifically induce the truncated forms of PGC-1α. Induction of truncated PGC-1α splice variants does not appear to underlie distinct adaptations to resistance versus endurance exercise. Further studies on the existence of numerous splice variants originating from different promoters are needed.
authors.affiliation: Department of Physiology and Pharmacology, Karolinska Institutet Stockholm, Sweden.
authors.forename: Mia
authors.initials: M
authors.lastname: Ydfors
authors.affiliation: Department of Laboratory Medicine, Karolinska Institutet Stockholm, Sweden.
authors.forename: Helene
authors.initials: H
authors.lastname: Fischer
authors.affiliation: The Swedish School of Sport and Health Sciences Stockholm, Sweden.
authors.forename: Henrik
authors.initials: H
authors.lastname: Mascher
authors.affiliation: Department of Physiology and Pharmacology, Karolinska Institutet Stockholm, Sweden ; The Swedish School of Sport and Health Sciences Stockholm, Sweden.
authors.forename: Eva
authors.initials: E
authors.lastname: Blomstrand
authors.affiliation: Department of Physiology and Pharmacology, Karolinska Institutet Stockholm, Sweden.
authors.forename: Jessica
authors.initials: J
authors.lastname: Norrbom
authors.affiliation: Department of Laboratory Medicine, Karolinska Institutet Stockholm, Sweden.
authors.forename: Thomas
authors.initials: T
authors.lastname: Gustafsson
keywords: Exercise; PGC-1α; human; skeletal muscle