The CNTF G1357A Polymorphism and Gender Alter the Muscle Strength Response to Resistance Training

Abstract

BACKGROUND: Limited investigation suggests that the ciliary nerotrophic factor G1357A (CNTF GA) polymorphism alters muscle function among middle-aged and older adults. PURPOSE: To examine associations between the CNTF GA polymorphism and muscle strength response to a unilateral, upper-arm resistance training (RT) program in healthy, young adults. METHODS: Subjects were 810 (mean ± SEM, 23.8 ± 0.4yr) men (42%) and women (58%). Of these, 75% were CNTF GG (248 men and 361 women), 22% CNTF GA (78 men and 97 women) and 3% CNTF AA (11 men and 15 women). Subjects performed a supervised 12wk (2d-wk) RT program of the non-dominant arm (trained, T) with the dominant arm (untrained, UT) as comparison. One-repetition maximum (1RM) measured peak dynamic elbow-flexor muscle strength in T and UT pre- and post-RT. Multiple variable and repeated measure ANO VA tested if muscle strength differed among CNTF genotypes and gender with body mass index, ethnicity, and age as covariates pre-, post-, and pre- to post-RT. Muscle strength phenotypes did not differ among CNTF GA and AA genotypes so these were combined and statistical analyses repeated. Results are reported comparing CNTF GG versus GA/AA genotypes. RESULTS: 1RM did not differ by CNTF genotype in T and UT in the total sample pre-, post-, or pre- to post-RT (P<0.05). However, gender interacted significantly with CNTF genotype to alter 1RM response to RT. Among men 1RM was not different between CNTF genotypes in T and UT pre- and post-RT (P<0.05). Similarly, the 1RM increase in T did not differ between CNTF genotypes pre-to post-RT (p>0.05).In contrast, men with the CNTF A allele (i.e., GA/AA) gained more absolute (1.4 ± 0.2 vs 0.7 ± 0.1kg), relative (12.2 ± 1.7vs 6.1 ± 0.9%), and allometric (0.2 ± 0.0 vs 0.1 ± 0. lkg-kg-0.67) 1RM in UT than CNTF GG homozygotes pre- to post- RT (p<0.05). Among women 1RM in T and UT was not different between CNTF genotypes pre-, post-, and pre- to post-RT (P<0.05). CONCLUSION: Men with the A allele of the CNTF GA polymorphism gained greater absolute, relative, and allometric dynamic muscle strength in UT than men with the CNTF GG genotype. The CNTF GA polymorphism did not alter muscle strength response to RT in T among men or women. Our findings suggest the CNTF GA polymorphism is involved with neurologic adaptations to RT among men.