Ethnic Disparity in the Relationship between Obesity and Plasma Insulin-Like Growth Factors: The Multiethnic Cohort

Abstract

Previous studies on the relationship between obesity and circulating insulin-like growth factor (IGF) hormones show inconsistent findings and have not considered the possibility of racial/ethnic -specific differences that may exist. We therefore examined the relationship between obesity status [as measured by body mass index (BMI)] and plasma levels of the IGF proteins, IGF-I, IGF-binding protein 3 (IGFBP-3), and the molar ratio of IGF-I/IGFBP-3 in Whites, African Americans, Latinos, Japanese Americans, and Native Hawaiians from the ongoing Hawaii and Los Angeles Multiethnic Cohort Study. We measured plasma IGF-I and IGFBP-3 by ELISA in a random sample of 811 Multiethnic Cohort participants (53% male, age range = 47-82 at blood draw). In a multivariate regression of IGF-I levels, we found a statistically significant interaction between race/ethnicity and obesity status (P = 0.005).Plasma IGF-I levels declined with increasing BMI most dramatically in Latinos and Japanese. This decline was attenuated in Whites and absent in African-American and Native Hawaiian subjects. In Japanese, the quadratic term (BMI 2 ) was statistically significant in a multivariate model (P = 0.002). In Latinos, the adjusted least-squares mean IGF-I levels in ng/mL for BMI < 25, 25 to 29.99, and z30 were 184.6, 147.7, and 132.7, respectively. No interaction between race/ethnicity and BMI explained the plasma IGFBP-3 levels in these data. These results may help to resolve the uncertainty in the relationship between circulating IGF levels and obesity and highlight the potential importance of racial/ethnic -specific effects among these factors in explaining ethnic disparities in obesity-related cancers. (Cancer Epidemiol Biomarkers Prev 2006;15(11):2298 -302)

Prostate Cancer Risk in Relation to Insulin-like Growth Factor (IGF)-I and IGF-Binding Protein-3: A Prospective Multiethnic Study

“…Although differing associations of body mass index with IGFs among ethnic groups Table 2. Age-adjusted ORs and 95% CIs for prostate cancer risk in relation to prediagnostic IGF-I, IGFBP-3, and IGFto-IGFBP-3 ratio All (N = 512) Blacks (n = 153) Whites (n = 184) Asians (n = 175) may affect results (21), in our population no clear patterns were observed. Although we did not observe differences in the risk relationships associated with ethnicity, caution is required in interpretation due to small numbers for subgroup analyses.…”

A Prospective Study of Body Size and Breast Cancer in Black Women

“…This finding suggests that increases in postmenopausal estrogen levels, as occurs with increasing BMI, may not have as much effect on breast cancer incidence in Black women. In the same cohort, levels of plasma insulin-like growth factor I, which is part of the pathway for negative feedback on growth hormone secretion, declined with increasing BMI in Latinas, Japanese, and White women, but increased with increasing BMI in African American women (48). Insofar as growth hormone plays a role in the etiology of breast cancer, the differing relation of obesity to insulin-like growth factor-I levels by ethnic group may explain the relative lack of association of obesity with breast cancer risk in postmenopausal Black women.…”

The association of diabetes mellitus and high-grade prostate cancer in a multiethnic biopsy series

“…The mechanisms underlying the potential interactions of DM and high-grade disease with race and obesity remain unclear. A prior study found that overweight and obese CM had lower free IGF-1 levels than all AAM, regardless of obesity status, and non-obese CM [24]. Moreover, obese CM have lower levels of testosterone than all AAM, regardless of obesity status, and non-obese CM [25].…”