Abstract A93: Ethnic and anthropometric correlates of IGF axis in the United States

Abstract

Abstract A93 Insulin-like growth factor-1 (IGF-1) levels are positively related to some cancers and negatively related to cardiovascular disease. These conditions are also related to insulin resistance and high body weight leading to the hypothesis that IGF-1 levels may, in part, mediate the association of high body weight with these health outcomes. Using the National Health and Nutrition Examination Survey (NHANES) III population, we examined the associations between IGF-1, IGFBP-3, and the IGF-1/IGFBP-3 molar ratio with anthropometric measures in a large, United States population-based study where these associations could also be stratified by race/ethnicity and gender. The study population consisted of 3168 women and 2635 men who participated in NHANES III and provided a fasting morning serum sample. The study population was 44% non-Hispanic white, 28.2% non-Hispanic black, and 27.7% Mexican-American. On average, the female participants in the study were approximately 45 years old with a body mass index (BMI) of 26.3 while the male participants were approximately 43 years old with a BMI of 26.9. Linear regression models were used to determine the associations of IGF-1, IGFBP-3 and IGF-1/IGFBP-3 molar ratio with anthropometric variables across race/ethnicity and gender. The anthropometric measures included height, weight, waist-to-hip ratio, waist circumference, sum of skinfolds, and percent body fat and were obtained by trained personnel in the NHANES mobile examination center. IGF-1 and IGFBP-3 were measured by staff at Diagnostic System Laboratories (DSL, Inc., Webster, TX). BMI, waist-to-hip ratio, and waist circumference were inversely associated with IGF-1 levels across all race/ethnicity and gender subgroups except for non-Hispanic black men. The magnitude of the regression coefficients differed across racial/ethnic groups. In contrast, very few anthropometric measures where significantly associated with IGFBP-3 levels. The exception to this is non-Hispanic black men, where all anthropometric measures except height were positively associated with IGFBP-3 levels. The IGF-1/IGFBP-3 molar ratio was inversely associated with all anthropometric measures, except height, in all subgroups of the population. In addition, when examining mean levels of biomarkers across tertile of BMI, Mexican-American men and women had the lowest levels of IGF-1 and non-Hispanic white men and women had the highest levels of IGFBP-3. For the IGF-1/IGFBP-3 molar ratio, non-Hispanic black men and women had the highest ratios across all tertiles of BMI. The racial and ethnic differences in the levels of IGF-1, IGFBP-3, and the IGF-1/IGFBP-3 molar ratio and longitudinal evaluation of their associations with anthropometrics measures merit further investigation since IGF-1 levels have been hypothesized to be a contributor to many health outcomes. Our data are not consistent with the hypothesis that the association of high IGF-1 levels with health outcomes such as increased cancer risk is mediated through high BMI. Citation Information: Cancer Prev Res 2008;1(7 Suppl):A93.