Association between IGF-2 gene and fat-free mass in response to resistance training

Abstract

BACKGROUND: It is well established that the human aging process is associated with a significant decline in neuromuscular function and performance. Twin studies demonstrate that genetic factors partially explain the inter-individual variation of fat-free mass (FFM) and muscle strength. PURPOSE: To examine the association between the polymorphism of the gene IGF-2 with phenotypes strength and muscle mass of elderly women pre and post resistance training. METHODS: 76 elderly women participated in this analysis. These volunteers, who should be sedentary for at least 6 months before the study, were assigned four groups in relation to allele GAGG, AA, GAAA and GG. The first analysis compared 60 elderly women with GG and GA allele (GAGG) versus 16 elderly women with AA allele. The second analysis compared 54 elderly women with GA and AA (GAAA) versus 22 elderly women GG allele. The Body mass index, fat free mass, fat mass and Isokinetic Muscle Peak Torque were measured. All volunteers were participating in the Resistance Training program. The DNA was extracted from peripheral venous blood leukocytes using a salting out protocol. The primer for IGF-II gene exon 9 was 5’-GTCCCTGAACCAGCAAAGAG-3’ 0.5 μM (0.625 μl) Primer R-5’-TGATGGAAAAGGGAGTGAGG-3’ 0.5 μM (0.625 μl), Taq DNA Polimerase enzime 0.5 U (0.1 μl), água milli-Q (3.8 μl) 5 hg de DNA (3 μl). PCR amplification was performed in a programmable thermal cycler GeneAmp? PCR System 9700. RESULTS: The results of the first analysis GAGG × AA versus the group AA showed the relative increase in knee extensor peak torque relative and also in the fat-free mass and showed a decrease in the fat mass percentage in the GAGG group. The second analysis considered the group GAAA versus group GG showed decreases in the fat-free mass percentage in the GAAA group, also showed the relative increase in the fat-free mass in the GG group and decrease in the fat mass percentage in the GG group. CONCLUSIONS: The results of this study show that 24 weeks of the resistance training improved strength and muscle mass and decreased the fat mass. The results confirm this assertion and suggest the G allele presents more influence over the A allele, in relation to phenotypes strength and muscle mass in elderly women after resistance training.