Abstract A78: Associations between IGF-axis, testosterone and nutrients in healthy African American and Caucasian men at increased risk for prostate cancer

Abstract

Abstract Introduction: African American men have the highest incidence and death rates from prostate cancer in the United States. The insulinlike growth factor (IGF) axis has been implicated in the carcinogenesis of prostate cancer. Several epidemiological studies have shown increased serum concentrations of IGF-1 and alterations of the associated binding proteins-IGFBP-2 and IGFBP-3, as strong risk factors for prostate cancer. This study examined racial differences in risk factors for prostate cancer in a healthy high risk screening population of African American and Caucasian males. The associations between IGF-1, IGFBP-2, IGFBP-3, prostate-specific antigen (PSA), testosterone, body mass index (BMI) and specific dietary macronutrients were examined. Methods: Serum was collected from 461 African American and Caucasian men aged ≥25 years who participated in prostate cancer screening programs located at two university hospitals in Washington, DC. Serum concentrations of IGF-1, IGFBP-2, IGFBP-3, PSA, and testosterone were analyzed using immunoassays from Diagnostic Systems Laboratories (Webster, TX). Height and weight were used to create BMI, which was calculated as weight/height2 (kg/m2). A food-frequency questionnaire was administered over the telephone to 128 study participants who consented. Wilcoxon rank sums test and chi square test examined mean differences and associations with other risk factors. Multiple linear regression analysis was used to examine racial differences in IGF-1, IGFBP-3, IGFBP-2, testosterone, PSA and specific macronutrients, adjusted for covariates such as age and BMI. Results: African American men had significantly lower concentrations of IGFBP-2 (p=0.035), and significantly higher concentrations of IGFBP-3 and testosterone when compared to Caucasian men, p=0.031 and p=0.033 respectively. There were no significant differences found for concentrations of IGF-1 by race. Levels of IGFBP-2 exhibited a significant inverse association with BMI for both races and a positive association with age for Caucasians. African American men had higher mean intakes of total calories, total fat, protein and carbohydrate, but only dietary fat intake was significantly higher when compared to intakes in Caucasian men (p=0.026). Multiple regression analysis revealed no significant relationships between nutrient intake and concentrations of IGF-1, IGFBP-3, IGFBP-2, PSA and testosterone by race. Finally, IGFBP-2 exhibited a significant univariate negative correlation with total calories, protein and total fat, with a somewhat stronger association among Caucasian than African American men. Conclusion: We provide evidence of racial variation in concentrations of IGFBP-2, IGFBP-3 and testosterone, but not for IGF-1. In this sample, African American men had a significantly higher consumption of total dietary fat intake than Caucasians. Further work is needed to determine whether these observations may explain the racial disparity in prostate cancer incidence and mortality in the U.S. Funded by: Department of Defense DAMD17-00-1-0024 Citation Information: Cancer Epidemiol Biomarkers Prev 2010;19(10 Suppl):A78.