Lifestyle and Dietary Correlates of Plasma Insulin-Like Growth Factor Binding Protein-1 (IGFBP-1), Leptin, and C-Peptide: The Multiethnic Cohort

Abstract

Circulating insulin-like growth factor binding protein 1 (IGFBP-1), leptin, and insulin are 3 proteins modified by obesity and have been associated with cancer at several sites in past studies. We conducted a cross-sectional study to describe the correlation of these proteins with gender, race/ethnicity, anthropometric indexes, and dietary and lifestyle factors. We measured fasting plasma levels of IGFBP-1, leptin, and C-peptide, used here as a stable measure of insulin secretion, in a random sample of 450 male and 352 postmenopausal female Hawaii and Los Angeles Multiethnic Cohort Study (MEC) participants (age range 47–82 yr at blood draw). Through a series of multiple linear regressions, we found that the most parsimonious model for plasma IGFBP-1 included inverse associations with age, body mass index (BMI), and regular soda intake. A term for interaction between age and BMI was positively associated with plasma IGFBP-1. Adjusted mean plasma leptins were highest among Whites and African Americans and lowest among Hawaiians and Japanese Leptin was also inversely associated with age and positively associated with the interaction between age and race/ethnicity, female gender, and BMI. A model with only race/ethnicity and BMI (positive association) was best for plasma C-peptide. Adjusted means for C-peptide were highest for Japanese and Whites and lowest for African Americans. The overall percent of variance in protein levels explained by these models was low for IGFBP-1(R² = 0.17) and C-peptide (R² = 0.11) and higher for leptin (R² = 0.57). We saw no clear correlation between racial/ethnic trends in protein levels with those of colorectal, breast, or prostate cancer incidence rates in the MEC. Research to clarify factors associated with determination of these proteins and their relationship with cancer etiology is warranted.

Acknowledgments and Notes

This work was done at the University of Southern California, Keck School of Medicine in Los Angeles, California, in collaboration with the Cancer Research Center of Hawaii, in Honolulu, and the International Agency for Research on Cancer in Lyon, France. This work was supported by National Cancer Institute Grants CA54281 and CA63464. The authors would like to thank Jennifer Yamamoto for help with data analysis.

Notes

^a Abbreviations are as follows: IGFBP, insulin-like growth factor binding protein; LS, least squares; CL, confidence limit; BMI, body mass index.

^b P value testing homogeneity of LS Means across race/ethnicity derived from analysis of variance models.

^a Means presented are LS means of transformed hormone levels exponentiated back to physiological levels. IGFBP-1 and C-peptide levels are crude levels. Leptin levels are adjusted for gender only. Abbreviations are as follows: IGFBP, insulin-like growth factor binding protein; Q, quartile; L,; BMI, body mass index; METs, metabolic units.

^b P values for homogeneity, categorical variable.

^c P values for trend, categorical continuous variable.

^a Abbreviations are as follows: LS, least squares; IGFBP, insulin-like growth factor binding protein; AA, African Americans; H, Native Hawaiians; J, Japanese Americans; W, Whites; L, Latinos. Protein concentrations are adjusted for covariates found to be significant in multivariate model (see Table 3). LS Mean levels in ng/ml.

^b Cancer incidence rates are truncated to ages 50–74 per 100,000 and age adjusted to the U.S. 1970 standard population.

^a Abbreviations are as follows: IGFBP, insulin-like growth factor binding protein; BMI, body mass index. Whites are reference group.

^b P testing the null hypothesis that the parameter is not significantly different from zero.

^c Multivariate R ²adjusting for all variables in model.