Circulating Leptin, Adiponectin, And Breast Density In Premenopausal Mexican Women: The Mexican Teachersí Cohort

Sabina RINALDI, International Agency for Research on Cancer, France
DOSSUS L. 1 , BIESSY C. 1 , HERNANDEZ M. 1 , LAJOUS M. 2,3 , MONGE A. 2 , ORTIZ-PANOZO E. 2 , YUNES E. 2 , LOPEZ-RIDAURA R. 2 , TORRES-MEJÍA G. 2 , ROMIEU I. 1,2

1 International Agency for Research on Cancer, Lyon, France
2 Center for Research on Population Health, National Institute of Public Health, Mexico
3 Department of Epidemiology, Harvard School of Public Health, Boston, MA

Purpose
Leptin and adiponectin are adipocytokines produced by the adipose tissue. Mammographic density (MD) is the strongest predictor of breast cancer (BC), and is highly influenced by adiposity. How MD directly influences BC risk is still unknown, especially in premenopausal women, where adiposity seems to be protective for BC. The aim of the present study was to explore the association between circulating leptin, adiponectin, and their ratio, with mammographic density in Mexican pre-menopausal women who are part of the large Mexican Teachers’ Cohort (MTC), a cohort of over 100,000 teachers recruited in 2006-2008 in 12 Mexican states.
 
Methods
A subsample of 2,084 women from the MTC participated in a clinical evaluation (anthropometric measurements, a mammogram, collection of biological specimens). Of them, 574 premenopausal women were randomly selected for this study, proportionally to size sampling from four MD strata. A single radiologist performed MD in all regions, taking cranio-caudal views on each breast. Leptin and adiponectin concentrations were measured in serum by immunoassays.  Multivariate regression analyses were performed to compare means of MD by quartiles of leptin, adiponectin and their ratio.
 
Results
After adjustment for BMI, high leptin levels were significantly associated with lower percentage MD compared to low leptin levels (31.02% vs 43.38%, first vs fourth quartile, ptrend<0.0001). No significant association was observed between adiponectin concentrations and MD. The leptin/adiponectin ratio was significantly associated with a lower percentage MD, although this association lost significance after adjustment for BMI.
 
Conclusions
Low percentage MD is associated with high leptin concentrations, suggesting that the inverse association observed between BMI and BC in premenopausal women might be mediated by leptin, but not adiponectin.
 
Funding sources
American Institute for Cancer Research, CONACyT (Consejo Nacional de Ciencia y Tecnología, Mexico), the Ministry of Health of Mexico, AVON, Banorte