Assessing estrogenic activity of phytochemicals using transcriptional activation and immature mouse uterotrophic responses

Increased aggressive behavior and decreased affiliative behavior in adult male monkeys after long-term consumption of diets rich in soy protein and isoflavones

Estrogen produced by aromatization of gonadal androgen has an important facilitative role in male-typical aggressive behavior that is mediated through its interaction with estrogen receptors (ER) in the brain. Isoflavones found in soybeans and soy-based dietary supplements bind ER and have dose- and tissue-dependent effects on estrogen-mediated responses. Yet, effects of isoflavone-rich diets on social and aggressive behavior have not been studied. We studied the effects of long-term (15 months) consumption of diets rich in soy isoflavones on spontaneous social behavior among adult male cynomolgus macaques (Macaca fascicularis) (n = 44) living in nine stable social groups. There were three experimental conditions which differed only by the source of dietary protein: casein and lactalbumin (no isoflavones), soy protein isolate containing 0.94 mg isoflavones/g protein, and soy protein isolate containing 1.88 mg isoflavones/g protein. In the monkeys fed the higher amount of isoflavones, frequencies of intense aggressive (67% higher) and submissive (203% higher) behavior were elevated relative to monkeys fed the control diet (P's < 0.05). In addition, the proportion of time spent by these monkeys in physical contact with other monkeys was reduced by 68%, time spent in proximity to other monkeys was reduced 50%, and time spent alone was increased 30% (P's < 0.02). There were no effects of treatment on serum testosterone or estradiol concentrations or the response of plasma testosterone to exogenous gonadotropin-releasing hormone (GnRH). The results indicate that long-term consumption of a diet rich in soy isoflavones can have marked influences on patterns of aggressive and social behavior.

A Natural Antioxidant Mixture from Spinach Does Not Have Estrogenic or Antiestrogenic Activity in Immature CD-1 Mice

The use of natural antioxidants and flavonoids in nutritional and pharmaceutical applications is increasing. Because some phytochemicals such as genistein, found in soy products, have estrogenic activity, we investigated the estrogenic potential of a natural antioxidant mixture (NAO) isolated from spinach leaves, using an in vivo uterotrophic bioassay and an in vitro transcriptional activation assay for the estrogen receptor (ER). Outbred female CD-1 mice (17 d old) were given subcutaneous injections of 17beta-estradiol or genistein [500 and 500,000 microg /(kg x d), respectively] as positive controls or NAO [1000 to 1,000,000 microg/(kg x d)] for 3 d. Uterine wet weight/body weight ratios were determined. Both 17beta-estradiol and genistein significantly increased uterine wet weight ratios compared with untreated controls, but NAO did not. Histological examination of the uterus showed that 17beta-estradiol and genistein increased epithelial cell height, number and gland development, but NAO did not. Estrogenic activity of NAO was investigated in vitro using the ER transcriptional activation assay. BG1Luc4E2 cells expressing ER were stably transfected with a luciferase reporter gene responsive to estrogens. 17beta-estradiol dose dependently increased luciferase activity; NAO had no effect. When NAO was tested for antiestrogenic activity, it did not lessen the effects of 17beta-estradiol. These data suggest that NAO does not have estrogenic or antiestrogenic activity. Thus, an antioxidant mixture has been identified that does not have potentially adverse estrogenic activity.

Evaluation of an estrogen receptor-beta agonist in animal models of human disease

The discovery of a second estrogen receptor (ER), called ERbeta, in 1996 sparked intense interest within the scientific community to discover its role in mediating estrogen action. However, despite more than 6 yr of research into the function of this receptor, its physiological role in mediating estrogen action remains unclear and controversial. We have developed a series of highly selective agonists for ERbeta and have characterized their activity in several clinically relevant rodent models of human disease. The activity of one such compound, ERB-041, is reported here. We conclude from these studies that ERbeta does not mediate the bone-sparing activity of estrogen on the rat skeleton and that it does not affect ovulation or ovariectomy-induced weight gain. In addition, these compounds are nonuterotrophic and nonmammotrophic. However, ERB-041 has a dramatic beneficial effect in the HLA-B27 transgenic rat model of inflammatory bowel disease and the Lewis rat adjuvant-induced arthritis model. Daily oral doses as low as 1 mg/kg reverse the chronic diarrhea of HLA-B27 transgenic rats and dramatically improve histological disease scores in the colon. The same dosing regimen in the therapeutic adjuvant-induced arthritis model reduces joint scores from 12 (maximal inflammation) to 1 over a period of 10 d. Synovitis and Mankin (articular cartilage) histological scores are also significantly lowered (50-75%). These data suggest that one function of ERbeta may be to modulate the immune response, and that ERbeta-selective ligands may be therapeutically useful agents to treat chronic intestinal and joint inflammation.