Association Between the 4 bp Proinsulin Gene Insertion Polymorphism (IVS‐69) and Body Composition in Black South African Women |
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| Authors: | Peter Berman Malcolm Collins Ingrid Baumgarten Cathal Seoighe Courtney L. Jennings Yael Joffe Estelle V. Lambert Naomi S. Levitt Mirjam V. Faulenbach Steven E. Kahn Julia H. Goedecke |
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| Affiliation: | 1. Division of Chemical Pathology, University of Cape Town, Cape Town, South Africa;2. UCT/MRC Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, University of Cape Town, Cape Town, South Africa;3. South African Medical Research Council, Cape Town, South Africa;4. Institute for Infectious Disease and Molecular Medicine, University of Cape Town, Cape Town, South Africa;5. Department of Mathematics, Statistics and Applied Mathematics, National University of Ireland, Galway, Ireland;6. Endocrine Unit, Department of Medicine, University of Cape Town, Cape Town, South Africa;7. Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, VA Puget Sound Health Care System and University of Washington, Seattle, Washington, USA. |
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| Abstract: | 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/m2) and 138 obese (BMI ≥30 kg/m2) premenopausal women. The frequency of the insertion allele was significantly higher in the class 2 obese (BMI ≥35kg/m2) 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 cm2, 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. |
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