Protein Phosphatase 3 (PPP3R1) Gene Polymorphism Influences Muscle Volume Response To Strength Training

Abstract

The PPP3R1 gene encodes for a calcium-binding regulatory protein, calcineurin B, which has been shown to play an important role in hypertrophy of myocytes by interacting with insulin-like growth factor-1, GATA-2, and NF-ATc1. PURPOSE To determine whether polymorphisms in the PPP3R1 gene influence the effect of strength training (ST) on muscle size and function. METHODS One-repetition maximum (1-RM) strength and muscle volume (MV) of the knee extensors (KE) were measured in 96 previously sedentary older (66±8 yrs) men (n=37) and women (n=59) before and after a 10 wk unilateral ST program. MV was measured by computed tomography. DNA was extracted from whole blood samples and genotypes for the PPP3R1 gene, at exon 2, were determined resulting in 16 A-allele homozygotes (AA, 7 men, 9 women, 66±9 yrs), 59 heterozygotes (AG, 21 men, 38 women, 65±9 yrs), and 21 Gallele homozygotes (GG, 9 men, 12 women, 66±7 yrs). RESULTS The results from ANCOVA revealed a significant difference in change in MV between AA and GG (90±15 vs 134±19 cm3, P=0.04). The difference in change in MV between AG and GG approached significance (104±7 vs 134±19 cm3, P=0.06). When AA and AG genotype groups were combined and compared with GG the change in MV was still significant (102±7 vs 134±19 cm3, P=0.04). At baseline, there were no significant differences in MV or KE 1-RM strength among PPP3R1 genotype groups. Also there were no differences in changes in KE 1-RM strength with ST among PPP3R1 genotype groups. CONCLUSION These data indicate that PPP3R1 genotype influences MV response to ST in older adults. Supported by NIH Grants RO1 AG4-2148, AG1620501, and AG022791