Altered sexually dimorphic nucleus of the preoptic area (SDN-POA) volume in adult Long-Evans rats by dietary soy phytoestrogens

Naturally occurring estrogen-like molecules in plants (phytoestrogens), pre sent via soy, in animal diets can alter morphology and physiology in rodent s. Phytoestrogens have the ability to bind estrogen receptors and exert man y of the biological responses evoked by physiological estrogens. This study characterized the effects of dietary phytoestrogens on the expression of b ody and prostate weight, circulating testosterone and estradiol levels, pub erty onset, vaginal cyclicity, and volume of the sexually dimorphic nucleus of the preoptic area (SDN-POA) in Long-Evans rats. Using different experim ental protocols, animals were fed either a phytoestrogen-rich (Phyto-600) o r a phytoestrogen-free (Phyto-free) diet. Animals fed the Phyto-600 diet di splayed significantly decreased body weights (in males and females), prosta te weights and delayed puberty in females compared to that of animals fed t he Phyto-free diet. Circulating testosterone or estradiol levels in males o r estrous cyclicity were not altered by the diets. The volume of the SDN-PO A was significantly altered by a cham,e in diet at 80 days of age where one -half of the males or females fed the Phyto-600 diet (from birth) were swit ched to the Phyto-free diet until 120 days of age. Males initially fed a Ph yto-600 diet but changed to a Phyto-free diet had significantly smaller SDN -POA volumes compared to males fed the Phyto-600 diet (long-term). These da ta suggest that consumption of phytoestrogens via a soy diet, significantly : (1) decreases body and prostate weight, (2) delays puberty onset, and (3) alters SDN-POA volumes during adulthood. (C) 2001 Elsevier Science B.V. Al l rights reserved.