title: 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 >or=30 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.
authors.affiliation: Keck School of Medicine, University of Southern California, Los Angeles, California 90033-0800, USA. kahender@usc.edu
authors.forename: Katherine Delellis
authors.initials: KD
authors.lastname: Henderson
authors.forename: Michael I
authors.initials: MI
authors.lastname: Goran
authors.forename: Laurence N
authors.initials: LN
authors.lastname: Kolonel
authors.forename: Brian E
authors.initials: BE
authors.lastname: Henderson
authors.forename: Loïc
authors.initials: L
authors.lastname: Le Marchand
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D015331:Cohort Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005006:Ethnicity; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000208:ethnology* / Q000378:metabolism*; D012306:Risk
chemical_list: D018972:Insulin-Like Growth Factor Binding Protein 3; D007334:Insulin-Like Growth Factor I