Influence of promoter region variants of insulin-like growth factor pathway genes on the strength-training response of muscle phenotypes in older adults

Abstract

To examine the influence of insulin-like growth factor (IGF) pathway gene polymorphisms on muscle mass and strength responses to strength training (ST), we studied 128 White and Black men and women before and after a 10-wk single-leg knee extension ST program. One-repetition maximum strength, muscle volume (MV) via computed tomography, and muscle quality (MQ) were assessed at baseline and after 10 wk of ST. There was a significant combined IGF1 cytosine adenine (CA) repeat gene effect, which included both the IGF1 CA repeat main effect and IGF1 CA repeat x PPP3R1 insertion-deletion (I/D) gene x gene interaction effect, on the changes in strength (P < 0.01) and MQ (P < 0.05) with ST. There was a trend for a significant gene x gene interaction between IGF1 CA repeat and PPP3R1 I/D for changes in strength (P = 0.07) and MQ (P = 0.06) with ST. The influence of the PPP3R1 A-202C gene polymorphism on change in MV with ST approached significance (P = 0.06). The IGF1 CA repeat polymorphism had a significant influence on the change in strength and MV combined with ST (P < 0.05), whereas the influence of the PPP3R1 I/D polymorphism approached significance (P = 0.08). There were no associations between the IGFBP3 A-202C gene polymorphism and the muscle phenotypic responses to ST. These data suggest that two of the three IGF pathway gene polymorphisms identified in this study influence muscle phenotypic responses to ST in both black and white older men and women.

Fig. 1

Influence of calcineurin B (PPP3R1) insertion-deletion (I/D) × insulin-like growth factor 1 (IGF1) cytosine adenine (CA) repeat genotype groups on change in 1-repetition maximum (1 RM) strength with strength training (ST). There was a trend for a significant gene × gene interaction between IGF1 CA repeat and PPP3R1 I/D (P = 0.072). Individuals homozygous for PPP3R1 II who were also heterozygous for IGF1 192 allele had significantly greater increases in 1 RM strength with ST than individuals homozygous for PPP3R1 II who were also IGF1 noncarriers of the 192 allele (*P = 0.003). Values are covaried for age, hormone replacement therapy status and sex, race, height, body mass index, and baseline 1 RM strength. Values are means ± SE.

Fig. 2

Influence of insulin-like growth factor binding protein 3 (IGFBP3) A-202C genotype × race groups on change in 1 RM strength with ST. There was a trend for a significant IGFBP3 A-202C gene × race interaction (P = 0.094). Black subjects homozygous for IGFBP3 AA had significantly greater increases in 1 RM strength with ST than White subjects homozygous for IGFBP3 AA (*P = 0.005). Values are covaried for age, hormone replacement therapy status and sex, race, height, body mass index, and baseline 1 RM strength. Values are means ± SE.

Fig. 3

Influence of calcineurin B (PPP3R1) I/D genotype groups on change in muscle volume (MV) with ST. There was a trend for individuals homozygous for PPP3R1 II to have greater increases in MV with ST than the PPP3R1 D allele carriers (P = 0.059). Values are covaried for age, hormone replacement therapy status and sex, race, height, body mass index, and baseline MV. Values are means ± SE.

Fig. 4

Influence of calcineurin B (PPP3R1) I/D × IGF1 CA repeat genotype groups on change in muscle quality (MQ) with ST. The gene × gene interaction between IGF1 CA repeat and PPP3R1 I/D approached significance (P =0.057). Individuals homozygous for PPP3R1 II who were also heterozygous for IGF1 192 allele had significantly greater increases in 1 RM strength with ST than PPP3R1 II homozygote individuals who were also IGF1 noncarriers of the 192 allele (*P = 0.004). Values are covaried for age, hormone replacement therapy status and sex, race, height, body mass index, and baseline MQ. Values are means ± SE.