Serum IGF-I and C-reactive protein in healthy black and white young men: the CARDIA male hormone study.
OBJECTIVE
Animal and human studies suggest that C-reactive protein (CRP) may be inversely associated with serum insulin-like growth factor-I (IGF-I) concentrations. However, most human studies have not controlled adequately for confounding factors, particularly nutritional intake. This population-based study examined whether CRP is inversely associated with IGF-I and IGFBP-3 concentrations.


METHODS
In cross-sectional analysis, multivariable linear regression with adjustment for age, BMI, smoking status, alcohol intake, and nutritional factors was used to relate log CRP, the independent variable, to IGF-I and IGFBP-3 in a sample of black (n=364) and white men (n=486) separately by race.


RESULTS
Only black men had positive findings: log CRP was significantly associated with IGF-I (beta=-13.1 ng/ml, p=0.02) and the difference in mean IGF-I concentrations between the highest and lowest quartiles of CRP was 26 ng/ml. There was a statistically significant interaction between log CRP and smoking status (p=0.02); the regression coefficient for IGF-I predicted from log CRP was significant in smokers (beta=-39.8 ng/ml, p=0.0001), but not in non-smokers. The difference in mean IGF-I concentrations between highest and lowest quartiles of CRP was 100 ng/ml for black smokers. There were no associations for IGFBP-3.


CONCLUSIONS
In our study, CRP levels are inversely associated with IGF-I concentrations in black male smokers; however, the causal nature of the association is unclear and should be studied further.
Colangelo
Laura A
LA
Department of Preventive Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA. l-colangelo@northwestern.edu
Chiu
Brian
B
Kopp
Peter
P
Liu
Kiang
K
Gapstur
Susan M
SM
D000328:Adult; D001741:Black or African American; D002097:C-Reactive Protein / Q000378:metabolism*; D003430:Cross-Sectional Studies; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D044465:White People
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; D002097:C-Reactive Protein