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Examining the Impact of Different Exercise Protocols on PGC‐1α and FNDC5 mRNA Expression in Human Skeletal Muscle

A recent overexpression model demonstrated that peroxisome proliferator‐activated receptor coactivator 1‐alpha (PGC‐1α) regulates the expression of fibronectin type III domain containing protein 5 (FNDC5); a novel myokine with a potential role in stimulating brown‐fat‐like development in white adipose tissue. Although FNDC5 mRNA expression remains unaltered following an acute bout of endurance exercise (END) and high intensity interval training (HIIT), it is unclear whether FNDC5 mRNA expression increases following aerobic exercise protocols that demonstrate elevations in PGC‐1α mRNA expression. Therefore, the purpose of the present study was to test the hypothesis that aerobic exercise protocols that increase PGC‐1α mRNA expression will concomitantly increase FNDC5 mRNA expression in human skeletal muscle. Skeletal muscle biopsies were obtained from healthy men at rest (PRE) and three hours after one bout of moderate intensity interval exercise (MIIT; n = 10; 11 one‐minute intervals at 73% WR at VO2peak separated with one‐minute rest periods), HIIT (n = 10; 8 one‐minute intervals at 100% WR at VO2peak separated with one‐minute rest periods), or sprint interval training (SIT; n = 14; 8 20‐second intervals at 170% WR at VO2peak separated with 10 second rest periods). All samples and PGC‐1α mRNA expression data were obtained from previously published studies (1,2). PGC‐1α mRNA expression significantly (p < 0.05) increased following MIIT (+393% ± 345%), HIIT (+720% ± 392%), and SIT (+284% ± 140%). However, FNDC5 mRNA expression did not change following acute MIIT (−8% ± 29%, p = 0.3), HIIT (+16% ± 32%, p = 0.3), or SIT (−5% ± 18%, p = 0.3). Furthermore, changes in PGC‐1α and FNDC5 mRNA expression did not significantly correlate following any exercise protocol. This study demonstrates that although PGC‐1α mRNA expression increased following all exercise protocols, FNDC5 mRNA did not change. Therefore, these results suggest that interval exercise protocols that induce increases in PGC‐1α mRNA expression do not increase FNDC5 mRNA expression.