Resumen de Acute Response of PGC-1[alpha] and IGF-1 Isoforms to Maximal Eccentric Exercise in Skeletal Muscle of Postmenopausal Women
Christina M. Dieli-Conwright, Jacqueline L. Kiwata, Creighton T. Tuzon, Tanya M. Spektor, Fred R. Sattler, Judd C. Rice, E. Tood Schroeder
PGC-1[alpha]4, a novel isoform of the transcriptional coactivator PGC-1[alpha], was recently postulated to modulate the expression of anabolic and catabolic genes and therefore regulate skeletal muscle hypertrophy. Resting levels of PGC-1[alpha]4 messenger RNA (mRNA) expression were found to increase in healthy adults after resistance training. However, the acute effect of resistance exercise (RE) on PGC-1[alpha]4 expression in populations prone to progressive muscle loss, such as postmenopausal women, has not been evaluated. Here, we investigated alterations in mRNA expression of PGC-1[alpha]4 and PGC-1[alpha]1, a regulator of muscle oxidative changes, in postmenopausal women after high-intensity eccentric RE and analyzed these findings with respect to changes in insulin-like growth factor (IGF)-1 and catabolic gene expression. Nine postmenopausal women (age, 57.9 ± 3.2 years) performed 10 sets of 10 maximal eccentric repetitions of single-leg extension with 20-second rest periods between sets. Muscle biopsies were obtained from the vastus lateralis of the exercised leg before and 4 hours after the RE bout with mRNA expression determined by quantitative real-time polymerase chain reaction. No significant changes in the mRNA expression of either PGC-1[alpha] isoform were observed after acute eccentric RE (p > 0.05). IGF-1Ea mRNA expression significantly increased (p <= 0.05), whereas IGF-1Eb and mechano-growth factor (MGF) did not significantly change (p > 0.05). PGC-1[alpha]4 mRNA expression was associated with reduced mRNA expression of the catabolic gene myostatin (R = -0.88, p < 0.01), whereas MGF mRNA expression was associated with reduced mRNA expression of the catabolic gene FOXO3A (R = -0.81, p <= 0.05). These data demonstrate an attenuated response of PGC-1[alpha] isoforms to an acute bout of maximal eccentric exercise with short rest periods in postmenopausal women.
