title: Early ethnic difference in insulin-like growth factor-1 is associated with African genetic admixture.
abstract: IGF-1 is a growth-promoting hormone. Numerous studies have reported higher systemic concentrations of IGF-1 among African Americans (AA) compared with European Americans (EA) before puberty. We conducted this cross-sectional analysis to determine whether African ancestral genetic background, dietary factors, energy expenditure, adiposity, and socioeconomic status contribute to this difference. Children were prepubertal, AA and EA males and females. Genetic admixture was assessed from approximately 20 ancestry informative genetic markers. Body composition was determined by dual-energy x-ray absorptiometry; intake of energy, carbohydrate, protein, and fat by 24-h dietary recall; activity-related energy expenditure by doubly labeled water and indirect calorimetry; and socioeconomic status (SES) according to the Hollingshead scale. IGF-1 and IGF binding protein-3 (IGFBP-3) were measured using immunoradiometric assays. AA children had significantly greater IGF-1 compared with EA children (p < 0.01). In addition, AA children had lower SES and greater protein intake relative to EAs (p < 0.05 for both). Multiple linear regression analysis revealed that the only significant independent predictors of IGF-1 were IGFBP-3 and African admixture (p < 0.01 for both). Thus, our data suggest that the greater IGF-1 of AA relative to EA children could have a genetic basis.
authors.affiliation: Department of Nutrition Sciences and the Clinical Nutrition Research Center, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA. higginsp@uab.edu
authors.forename: Paul B
authors.initials: PB
authors.lastname: Higgins
authors.forename: José R
authors.initials: JR
authors.lastname: Fernández
authors.forename: Michael I
authors.initials: MI
authors.lastname: Goran
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Gower
mesh_terms: D050154:Adiposity; D044383:Black People / Q000235:genetics*; D002648:Child; D004032:Diet; D005006:Ethnicity / Q000235:genetics*; D005260:Female; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000235:genetics; D007334:Insulin-Like Growth Factor I / Q000502:physiology*; D008297:Male; D012923:Social Class; D001741:Black or African American
chemical_list: D018972:Insulin-Like Growth Factor Binding Protein 3; D007334:Insulin-Like Growth Factor I