Ciliary neurotrophic factor (CNTF) genotype and body composition

Exogenous ciliary neurotrophic factor ( CNTF) administration causes significant weight loss in both humans and animal models, but the effects of endogenous CNTF and the CNTF null allele on body composition are not fully understood. A recent study in a European cohort demonstrated a significantly higher body weight and body mass index (BMI) in older males homozygous for the CNTF null allele (A/A genotype). We sought to replicate these findings in three cohorts: the Baltimore Longitudinal Study on Aging (BLSA) consisting of 422 adult men and women ( 19 - 90 years); the Study of Osteoporotic Risk in Men ( STORM) consisting of 333 older men ( 50 - 84 years); and a third sample obtained by combining older males aged 59 - 73 years from the BLSA and STORM cohorts (n = 286). In contrast to the European study, we were unable to detect a significant association between CNTF genotype and body weight in the BLSA ( P = 0.49), the STORM ( P = 0.28), or the combined samples ( P = 0.72). There was also no significant association observed between CNTF genotype and BMI in the BLSA ( P = 0.59), the STORM ( P = 0.34) or the combined ( P = 0.56) samples. In addition, we were unable to detect a significant association between CNTF genotype and total body fat ( P = 0.95) or fat-free mass ( P = 0.86) in the BLSA cohort. Our results do not support an effect of the CNTF null allele on body composition, contrary to previous findings.