title: Relationships between IGF-1 and IGFBP-1 and adiposity in obese African-American and Latino adolescents.
abstract: The purpose of this study was to examine interrelationships between insulin-like growth factor 1 (IGF-1), IGF binding proteins (IGFBPs), and adiposity in 49 African-American and 77 Latino obese adolescents (15.3 ± 0.1 and 15.4 ± 0.2 years; BMI: 33.0 ± 0.7 and 35.0 ± 1.0 kg/m(2), respectively). Immunoradiometric assays were used to measure IGF-1, IGFBP-1, and IGFBP-3. Total fat and soft lean tissue were measured by dual-energy X-ray absorptiometry and visceral adipose tissue (VAT), subcutaneous abdominal adipose tissue (SAAT), and hepatic fat fraction (HFF) were measured by magnetic resonance imaging. IGF-1 levels were 23.1% higher and IGFBP-1 were 40.4% higher in African Americans compared to Latinos after adjustment for total lean and total fat mass. IGF-1 and IGFBP-1 were inversely correlated with BMI, total fat mass, VAT, and HFF (r = -0.20 to -0.33, P < 0.05) while IGFBP-1 was inversely correlated with SAAT (r = -0.22, P < 0.05). These relationships did not differ by ethnicity, however, the relationship between IGF-1 and SAAT, as well as IGFBP-1 and HFF, differed by ethnicity. Predicted mean IGF-1 levels were 30.7% higher for African Americans at the 75th compared to 25th percentile of SAAT and only 11.7% higher for Latinos. Predicted mean IGFBP-1 levels were 158% higher for African Americans at the 25th compared to the 75th percentile of HFF while IGFBP-1 levels were 1.7% higher for Latinos at the 75th compared to the 25th percentile. These results demonstrate that the relationship between IGF-1 and SAAT as well as IGFBP-1 and HFF are different in African-American and Latino adolescents and may contribute to the higher IGF-1 levels in African-Americans.
authors.affiliation: Department of Preventive Medicine, University of Southern California, Los Angeles, California, USA.
authors.forename: Tanya L
authors.initials: TL
authors.lastname: Alderete
authors.forename: Courtney E
authors.initials: CE
authors.lastname: Byrd-Williams
authors.forename: Claudia M
authors.initials: CM
authors.lastname: Toledo-Corral
authors.forename: David V
authors.initials: DV
authors.lastname: Conti
authors.forename: Marc J
authors.initials: MJ
authors.lastname: Weigensberg
authors.forename: Michael I
authors.initials: MI
authors.lastname: Goran
mesh_terms: D015502:Absorptiometry, Photon; D000273:Adipose Tissue / Q000000981:diagnostic imaging / Q000378:metabolism*; D000293:Adolescent; D001741:Black or African American; D001823:Body Composition; D005260:Female; D006630:Hispanic or Latino; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D050152:Intra-Abdominal Fat / Q000378:metabolism; D008099:Liver / Q000000981:diagnostic imaging / Q000378:metabolism*; D008297:Male; D009765:Obesity / Q000000981:diagnostic imaging / Q000208:ethnology / Q000378:metabolism*; D011627:Puberty; D014481:United States / Q000208:ethnology
chemical_list: D018970:Insulin-Like Growth Factor Binding Protein 1; D007334:Insulin-Like Growth Factor I