Predictors of variation in serum IGF1 and IGFBP3 levels in healthy African American and white men.
BACKGROUND
Individual variation in circulating insulinlike growth factor-1 (IGF1) and its major binding protein, insulinlike growth factor binding protein-3 (IGFBP3), have been etiologically linked to several chronic diseases, including some cancers. Factors associated with variation in circulating levels of these peptide hormones remain unclear.


METHODS
Multiple linear regression models were used to determine the extent to which sociodemographic characteristics, lifestyle factors, personal and family history of chronic disease, and common genetic variants, the (CA)n repeat polymorphism in the IGF1 promoter and the IGFBP3-202 A/C polymorphism (rs2854744) predict variation in IGF1 or IGFBP3 serum levels in 33 otherwise healthy African American and 37 white males recruited from Durham Veterans Administration Medical Center.


RESULTS
Predictors of serum IGF1, IGFBP3, and the IGF1:IGFBP3 molar ratio varied by race. In African Americans, 17% and 28% of the variation in serum IGF1 and the IGF1:IGFBP3 molar ratio, were explained by cigarette smoking and carrying the IGF1 (CA)19 repeat allele, respectively. Not carrying at least 1 IGF1 (CA)19 repeat allele and a high body mass index explained 8% and 14%, respectively, of the variation IGFBP3 levels. These factors did not predict variation of these peptides in whites.


CONCLUSIONS
If successfully replicated in larger studies, these findings would add to recent evidence, suggesting known genetic and lifestyle chronic disease risk factors influence IGF1 and IGFBP3 circulating levels differently in African Americans and whites.
Hoyo
Cathrine
C
Department of Community and Family Medicine, Duke University Medical Center, Box 2914, Durham, NC 27710, USA. hoyo0001@mc.duke.edu
Grubber
Janet
J
Demark-Wahnefried
Wendy
W
Lobaugh
Bruce
B
Jeffreys
Amy S
AS
Grambow
Steven C
SC
Marks
Jeffrey R
JR
Keku
Temitope O
TO
Walther
Phillip J
PJ
Schildkraut
Joellen M
JM
D000328:Adult; D001741:Black or African American / Q000706:statistics & numerical data*; D000483:Alleles; D015992:Body Mass Index; D014644:Genetic Variation; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins / Q000235:genetics / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D008019:Life Style; D016014:Linear Models; D008297:Male; D011237:Predictive Value of Tests; D011401:Promoter Regions, Genetic; D012907:Smoking / Q000453:epidemiology; D012959:Socioeconomic Factors; D014481:United States / Q000453:epidemiology; D044465:White People / Q000706:statistics & numerical data*
C515497:IGFBP3 protein, human; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I