title: Longitudinal analysis of the insulin-like growth factor system in African-American and European American children and adolescents.
abstract: BACKGROUND
  IGF-I and its binding proteins influence growth, development, and disease risk. Studies have revealed ethnic variations in the IGF system.
  
  
  OBJECTIVE
  This longitudinal study was undertaken to test the hypothesis that the ethnic differences in the IGF system exist throughout the pubertal transition, and these differences are mediated at least in part by inherent differences in insulin dynamics.
  
  
  METHODS
  This was a longitudinal study. Annual evaluations were conducted for pubertal maturation, body composition, acute insulin response to glucose (AIRg), and reproductive-endocrine profile. Hormones and binding proteins were determined using standard assays, the AIRg during a frequently sampled iv glucose tolerance test, and body composition by dual-energy x-ray absorptiometry. Mixed model analyses were used to identify and characterize ethnic differences in the IGF system across the pubertal transition after adjusting for ethnicity, sex, age, maturation status, body composition, and reproductive hormones, and to identify the contribution of insulin to IGF binding protein (IGFBP)-1.
  
  
  METHODS
  Subjects included African-American (AA) and European American children (n = 162 at baseline) aged 7-16 yr, evaluated across the pubertal transition.
  
  
  METHODS
  Annual data on IGF-I, IGFBP-1, and IGFBP-3 were examined.
  
  
  RESULTS
  IGF-I was higher in AA children at pubertal stage 1 only (P < 0.001). However, IGFBP-3 and IGFBP-1 concentrations were lower in AAs through much of puberty (P < 0.05). The lower IGFBP-1 of AAs was in part explained by greater AIRg.
  
  
  CONCLUSIONS
  Our data suggest that the higher IGF-I and lower IGFBP-1 and IGFBP-3 levels in AAs as compared with European Americans during puberty suggest potential ethnic differences in circulating bioavailable IGF-I. In addition, higher AIRg in AAs may lead to greater bioavailable IGF-I. Whether these differences in the IGF system account for disparities in disease risk warrants further investigation.
authors.affiliation: Department of Nutrition Sciences, 1675 University Boulevard, Room WEBB 415, University of Alabama at Birmingham, Birmingham, Alabama 35294-3360, USA. kristac@uab.edu
authors.forename: Krista
authors.initials: K
authors.lastname: Casazza
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: D015502:Absorptiometry, Photon; D000293:Adolescent; D001741:Black or African American; D000375:Aging / Q000502:physiology; D001786:Blood Glucose / Q000378:metabolism; D001823:Body Composition / Q000502:physiology; D002648:Child; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000235:genetics / Q000502:physiology; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000378:metabolism; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008137:Longitudinal Studies; D008297:Male; D011627:Puberty / Q000502:physiology; D012098:Reproduction / Q000502:physiology; D012727:Sex Characteristics; D012741:Sexual Maturation; D013002:Somatomedins / Q000502:physiology*; D044465:White People
chemical_list: D001786:Blood Glucose; D007328:Insulin; D018970:Insulin-Like Growth Factor Binding Protein 1; D018972:Insulin-Like Growth Factor Binding Protein 3; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I
references.citation: Clin Endocrinol (Oxf). 2005 Jul;63(1):94-102
references.pmid: 15963068
references.citation: Cancer Epidemiol Biomarkers Prev. 2006 Nov;15(11):2298-302
references.pmid: 17119061
references.citation: J Clin Endocrinol Metab. 2000 Feb;85(2):808-14
references.pmid: 10690895
references.citation: J Clin Endocrinol Metab. 1997 Jun;82(6):1923-7
references.pmid: 9177407
references.citation: J Lab Clin Med. 1998 Nov;132(5):383-9
references.pmid: 9823932
references.citation: Pediatr Res. 2005 Nov;58(5):850-4
references.pmid: 16183814
references.citation: Diabetes Obes Metab. 2008 Mar;10(3):198-211
references.pmid: 18269635
references.citation: Horm Res. 2006;65 Suppl 1:3-8
references.pmid: 16508327
references.citation: Calcif Tissue Int. 2002 Mar;70(3):146-52
references.pmid: 11907710
references.citation: J Clin Endocrinol Metab. 2002 Oct;87(10):4817-20
references.pmid: 12364479
references.citation: World J Urol. 2001 Aug;19(4):225-33
references.pmid: 11550779
references.citation: Diabetes. 1999 Aug;48(8):1515-21
references.pmid: 10426367
references.citation: J Pediatr. 1999 Sep;135(3):296-300
references.pmid: 10484792
references.citation: J Pediatr Endocrinol Metab. 2000 May;13(5):497-503
references.pmid: 10803867
references.citation: Stat Med. 1997 Oct 30;16(20):2349-80
references.pmid: 9351170
references.citation: BMJ. 1990 Jan 27;300(6719):230-5
references.pmid: 2106931
references.citation: Cancer Epidemiol Biomarkers Prev. 1999 Dec;8(12):1107-10
references.pmid: 10613344
references.citation: Pediatr Res. 1995 Aug;38(2):149-55
references.pmid: 7478808
references.citation: Annu Rev Med. 1968;19:283-300
references.pmid: 4297619
references.citation: J Clin Endocrinol Metab. 2006 Aug;91(8):3150-7
references.pmid: 16720666
references.citation: Urology. 2005 Sep;66(3):587-92
references.pmid: 16140083
references.citation: Acta Endocrinol (Copenh). 1992 May;126(5):381-6
references.pmid: 1377853
references.citation: Endocr Rev. 1997 Dec;18(6):801-31
references.pmid: 9408744
references.citation: Public Health Nutr. 2007 Jan;10(1):97-105
references.pmid: 17212848
references.citation: Am J Epidemiol. 2007 Sep 1;166(5):518-26
references.pmid: 17602136
references.citation: Growth Horm IGF Res. 2004 Jun;14(3):216-25
references.pmid: 15125883
references.citation: J Natl Cancer Inst. 2000 Oct 4;92(19):1592-600
references.pmid: 11018095
references.citation: J Pediatr. 1999 Sep;135(3):270-1
references.pmid: 10484785
references.citation: Carcinogenesis. 2007 Oct;28(10):2154-9
references.pmid: 17724372
references.citation: J Clin Endocrinol Metab. 2005 Mar;90(3):1483-8
references.pmid: 15598684
references.citation: Cancer Epidemiol Biomarkers Prev. 2004 Sep;13(9):1444-51
references.pmid: 15342444
references.citation: Oncology. 1999 Nov;57(4):330-40
references.pmid: 10575321
references.citation: Cancer Epidemiol Biomarkers Prev. 2005 Sep;14(9):2147-53
references.pmid: 16172224
references.citation: Urology. 1999 Jul;54(1):178-82
references.pmid: 10414748
references.citation: Circulation. 2002 Aug 20;106(8):939-44
references.pmid: 12186797
references.citation: J Biol Chem. 1991 Oct 5;266(28):18868-76
references.pmid: 1717456
references.citation: Pediatrics. 2002 Nov;110(5):911-9
references.pmid: 12415029
references.citation: J Pediatr. 2000 Dec;137(6):826-32
references.pmid: 11113840