Soy diet during early development may influence spermatogenesis in male rats

I Papaioannidis1, I Makaronidis2, T Papamitsou1, I Kyriakidis2, F Tsanakalis2, M Dermentzopoulou1, P Papaioannidou2. 1Aristotle University of Thessaloniki, Medical Faculty, Department of Histology and Embryology, Greece, 2Aristotle University of Thessaloniki, Medical Faculty, Department of Pharmacology, Greece

Introduction: Soy and soy products are recommended in human diet because of their beneficial effects in menopause and their potential protective effects in cancer and other diseases such as osteoporosis, hypercholesterolemia and heart disease. Nevertheless, a concern has been raised among scientists, due to their estrogenic effect. Genistein and other phytoestrogens contained in soy act as weak estrogenic agonists and bind to estrogen receptors α and β. Although they bind to estrogen receptors and they increase the expression of estrogen responsive genes with much weaker affinity than estradiol, they may disrupt the endocrine system by modulating the hypothalamic-pituitary-gonadal axis. Thus, genistein and other phytoestrogens contained in soy and soy products could influence the development of the reproductive system during crucial stages of life like gestation, lactation and early development after birth.

Objectives: The main objective of this study was to test the effect of soy diet on the development of the reproductive system of male rats, during early development.

Materials and Methods: Two groups of male Wistar rats 5 weeks old were used: The parents of the animals comprising the study group received ad libidum food enriched in soy protein before mating and during gestation and lactation, while the offsprings went on receiving the same food up to the age of five weeks. The control group and their parents received ad libidum the standard food before and during gestation, during lactation and up to the age of five weeks. Both groups were grown under the same conditions and according to the rules of Good laboratory Practice. The study was approved by the local Ethics Committee.

Five weeks after birth, the animals were sacrificed and specimens of the reproductive organs were prepared and stained for microscopic examination. The preparations were observed under optical microscope and assessed by two different persons, blinded on the source of the specimen. Statistical analysis was performed with the statistical package SPSS.

Results: There was no important difference between the study and the control group on the basic histological structure of the young rat reproductive organs. The seminiferous tubules, the seminiferous epithelium and the interstitial cells of the testes had no basic differences in both groups. Nevertheless, the number of spermatocytes and the density of interstitial cells was lower in rats fed with soy during gestation, lactation and early life, compared to the rats fed with standard food.

Conclusions: Soy diet during gestation, lactation and early development does not seem to have important effects on the basic structure of the reproductive organs but it seems to influence the number of spermatocytes and interstitial cells of the testes, having thus an effect on spermatogenesis and on the production of androgens. This effect may have an impact on normal masculinization and on the future fertility of the animals, and must be taken into consideration in dietary habits during pregnancy, lactation and early stages of life.