Lack of association between adipose tissue distribution and IGF-1 and IGFBP-3 in men and women.

Insulin, insulin-like growth factor-1 (IGF-1), IGF binding protein-3 (IGFBP-3), and obesity, and in particular visceral obesity, are putative cancer risk factors. Little is known, however, about the relationship between IGFs and obesity. We investigated the relationship between adipose tissue distribution and IGF-1 and IGFBP-3. Single-slice abdominal computed tomography scanning through the L4-L5 interspace was used to measure visceral adipose tissue (VAT) and subcutaneous adipose tissue (SQAT) in 432 community-based subjects (267 men, 165 women; ages, 55-77), participating in a cancer screening trial. Insulin, IGF-1, IGFBP-3, and the ratio of IGF-1:IGFBP-3, measured by radioimmunoassay, were compared with age, body mass index, absolute and relative VAT and SQAT, and total abdominal fat. We found that men had a higher mean IGF-1 (129.5 versus 108.9 ng/ml; P < 0.0001) and more VAT (201.5 cm(3) versus 166.6 cm(3); P < 0.0001) than women. In men and women, there was no correlation between IGF-1, IGFBP-3, or the ratio of IGF-1:IGFBP-3 with body mass index, total fat, VAT or SQAT, or fasting insulin. In contrast, fasting insulin was highly correlated to all measures of obesity (P = 0.0001). We conclude that obesity, adipose tissue distribution, and in particular VAT are not correlated with IGF-1, IGFBP-3, or the molar ratio of IGF-1:IGFBP-3. The lack of association between obesity and the IGF-1 axis suggests that the IGF-1 axis is not a likely mediator between VAT and disease.