Association between the 4 bp proinsulin gene insertion polymorphism (IVS-69) and body composition in black south african women

The objective of the study was to examine the association between a functional 4 bp proinsulin gene insertion polymorphism (IVS-69), fasting insulin concentrations, and body composition in black South African women. Body composition, body fat distribution, fasting glucose and insulin concentrations, and IVS-69 genotype were measured in 115 normal-weight (BMI 25 kg/m 2) and 138 obese (BMI 30 kg/m 2) premenopausal women. The frequency of the insertion allele was significantly higher in the class 2 obese (BMI 35kg/m 2) compared with the normal-weight group (P = 0.029). Obese subjects with the insertion allele had greater fat mass (42.3 0.9 vs. 38.9 0.9 kg, P = 0.034) and fat-free soft tissue mass (47.4 0.6 vs. 45.1 0.6 kg, P = 0.014), and more abdominal subcutaneous adipose tissue (SAT, 595 17 vs. 531 17 cm 2, P = 0.025) but not visceral fat (P = 0.739), than obese homozygotes for the wild-type allele. Only SAT was greater in normal-weight subjects with the insertion allele (P = 0.048). There were no differences in fasting insulin or glucose levels between subjects with the insertion allele or homozygotes for the wild-type allele in the normal-weight or obese groups. In conclusion, the 4 bp proinsulin gene insertion allele is associated with extreme obesity, reflected by greater fat-free soft tissue mass and fat mass, particularly SAT, in obese black South African women.