Racial variation in insulin-like growth factor-1 and binding protein-3 concentrations in middle-aged men.
African-American men have the highest and Asian-American men have the lowest prostate cancer incidence rates in the United States; internationally, rates for the Asian continent are among the lowest. Higher insulin-like growth factor (IGF)-1, which participates in the control of cellular growth and differentiation and is modulated by IGF-binding protein-3 (IGFBP-3), was associated with an increased prostate cancer risk in three recent studies. We, therefore, investigated whether plasma levels of IGF-1 and IGFBP-3 vary by race in United States men selected from among members of the Health Professionals Follow-up Study who were 47-78 years old in 1993-1995 when they provided blood (n = 18,000). All of the men who described their major ancestry as African American (n = 63) and a random sample of 75 Asians and 75 Caucasians were invited to provide a second blood sample in 1997, of whom 42, 52, and 55, respectively, did so. IGF-1 and IGFBP-3 concentrations were determined by ELISA. We used nonparametric methods to assess racial variation in age-adjusted levels. Caucasians had the highest median IGF-1 level (224 ng/ml), followed by Asians (208 ng/ml) and African Americans (205 ng/ml). Median IGFBP-3 concentration was similar between Caucasians and Asians but was more than 13% lower in African Americans. Median molar IGF-1:IGFBP-3 ratio was greatest in Caucasians and lowest in Asians. The lower IGF-1 blood levels relative to IGFBP-3 levels among Asian men are consistent with their lower prostate cancer incidence. Although differences in circulating IGF-1 do not seem to account for the greater prostate cancer risk among African-American men, their absolute lower levels of IGFBP-3 may be contributory.
Platz
E A
EA
Department of Nutrition, Harvard School of Public Health, Boston, Massachusetts, USA. eplatz@jhsph.edu
Pollak
M N
MN
Rimm
E B
EB
Majeed
N
N
Tao
Y
Y
Willett
W C
WC
Giovannucci
E
E
D017677:Age Distribution; D000368:Aged; D044466:Asian People / Q000235:genetics*; D044383:Black People / Q000235:genetics*; D005500:Follow-Up Studies; D018740:Genetic Heterogeneity; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D006801:Humans; D015994:Incidence; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D011471:Prostatic Neoplasms / Q000453:epidemiology* / Q000235:genetics*; D012307:Risk Factors; D018709:Statistics, Nonparametric; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology; D044465:White People / Q000235:genetics*; D001741:Black or African American
D018972:Insulin-Like Growth Factor Binding Protein 3; D007334:Insulin-Like Growth Factor I