Diets High in Corn Oil or Extra-Virgin Olive Oil Provided From Weaning Advance Sexual Maturation and Differentially Modify Susceptibility to Mammary Carcinogenesis in Female Rats

Abstract

Based on the importance of early-life events in breast cancer risk, we have investigated the effects of high-fat diets on maturation, mammary gland development, and its susceptibility to transformation. Female Sprague-Dawley rats were fed a lowfat (LF), high corn oil (HCO), or high extra-virgin olive oil (HOO) diet from weaning and gavaged with 7,12-dimethylbenz[a]anthracene. Body weight and mass increased in the HCO group compared to the LF group. The vaginal opening was advanced in both high-fat groups, especially in the HCO group. This HCO group also had increased body weight around puberty, more corpora lutea at post-puberty, and tended to have higher kisspeptin levels in the hypothalamus. Both high-fat diets induced subtle modifications in the morphology of the mammary gland, with no changes on β-casein or hormone receptors expression in the gland. The HCO diet had a clearly stimulating effect of carcinogenesis, inducing the earliest appearance of tumors and the highest tumor incidence and yield, whereas the HOO diet seemed to have a weak enhancing effect, increasing tumor yield. Our data suggest a strong influence of the HCO diet in sexual maturation and mammary cancer risk, while rats fed the HOO diet were more similar to the controls.

ACKNOWLEDGMENTS

The authors wish to thank Dr. X. Cañas for his technical advice and Dr. J. Ruberte for the use of his laboratory. This work was supported by grants from the Plan Nacional de I + D + I 2004-2007 (AGL2006-07691/ALI); Fundación Patrimonio Comunal Olivarero 2008–2012 (FPCO2008-165.396); Agencia para el Aceite de Oliva del Ministerio de Medio Ambiente y de Medio Rural y Marino 2008–2012 (AAO2008-165.471); Organización Interprofesional del Aceite de Oliva Español 2009–2013 (OIP2009-165.646); and Sociedad Española de Senología y Patología Mamaria 2008. The sponsors had no role in the study design, data collection and analysis, interpretation of results, the preparation of the manuscript, the decision to submit the manuscript for publication, and the writing of the manuscript.

Notes

^a Values are mean ± SE of 5–6 animals per group at each time point. PND = postnatal day; LF = lowfat group; HCO = high corn oil group; HOO = high extra-virgin olive oil group. *P < 0.05 compared to the control LF group (Tukey's test).