ASSOCIATION AND LINKAGE STUDIES BETWEEN THE IGF-1 GENE AND BODY COMPOSITION: THE HERITAGE FAMILY STUDY

38 Insulin-like growth factor-1(IGF-1) has strong anabolic effects and blood levels are inversely correlated with abdominal visceral fat (AVF) and positively correlated with fat free mass (FFM). We investigated the relationships between a DNA microsatellite polymorphism in the promoter region of the IGF-1 gene and body composition phenotypes at baseline (B) and following the 20-wk endurance training program (Δ) of the HERITAGE Family Study. B and Δ levels of fat mass (FM), FFM and AVF were measured on 530 Caucasian subjects (98 families; 194 parents and 336 adult offspring). PCR was used to type the polymorphism (11 alleles; frequency of the 189 bp allele=0.71). In association studies, the 189 bp homozygote male parents had a higher B-AVF (170 ± 7 vs 145 ± 8 cm2, p<0.02). The 189 bp homozygote female parents had a significantly lower Δ-AVF than the other IGF-1 genotypes (-3 ± 2 vs -11 ± 3 cm2; p<0.03). Using sib-pair linkage, a strong linkage between IGF-1 and Δ-FFM was observed (308 full sibs, p<0.0002 after adjustment for age, sex and B-FFM), but only a weak linkage with B-AVF (p<0.02 after adjustment for age, sex and B-FM). In conclusion, associations were detected between the IGF-1 gene marker and B-AVF in male and Δ-AVF in female parents. Moreover, the IGF-1 gene was found to be linked with changes in FFM in response to endurance training.