Effects of the phytoestrogen genistein on the development of the reproductive system of Sprague Dawley rats

OBJECTIVES: Genistein is known to influence reproductive system development through its binding affinity for estrogen receptors. The present study aimed to further explore the effect of Genistein on the development of the reproductive system of experimental rats. METHODS: Eighteen post-weaning female Sprague Dawley rats were divided into the following groups: (i) a control group that received vehicle (distilled water and Tween 80); (ii) a group treated with 10 mg/kg body weight (BW) of Genistein (Gen 10); and (iii) a group treated with a higher dose of Genistein (Gen 100). The rats were treated daily for three weeks from postnatal day 22 (P22) to P42. After the animals were sacrificed, blood samples were collected, and the uteri and ovaries were harvested and subjected to light microscopy and immunohistochemical study. RESULTS: A reduction of the mean weekly BW gain and organ weights (uteri and ovaries) were observed in the Gen 10 group compared to the control group; these findings were reversed in the Gen 100 group. Follicle stimulating hormone and estrogen levels were increased in the Gen 10 group and reduced in the Gen 100 group. Luteinizing hormone was reduced in both groups of Genistein-treated animals, and there was a significant difference between the Gen 10 and control groups (p<0.05). These findings were consistent with increased atretic follicular count, a decreased number of corpus luteum and down-regulation of estrogen receptors-a in the uterine tissues of the Genistein-treated animals compared to the control animals. CONCLUSION: Post-weaning exposure to Genistein could affect the development of the reproductive system of ovarian-intact experimental rats because of its action on the hypothalamic-pituitary-gonadal axis by regulating hormones and estrogen receptors.

Efeitos das isoflavonas em altas doses sobre o útero da rata / Effects of high-dose isoflavones on rat uterus

OBJETIVO: Avaliar o efeito de altas doses de isoflavonas no útero de ratas adultas castradas. MÉTODOS: Ratas virgens ovariectomizadas (n = 40) foram tratadas por 30 dias consecutivos com veículo (GCtrl) ou genisteína nas concentrações 42 (GES42), 125 (GES125) e 250 (GES250) µg/g de peso corporal ao dia. O extrato de soja e o veículo (propilenoglicol) foram administrados por gavagem. Ao final do experimento, foi realizada dosagem sérica de 17 β-estradiol e progesterona, avaliou-se o peso dos animais e dos úteros e foi feito exame colpocitológico. Fragmentos do terço médio dos cornos uterinos foram fixados em formol a 10 por cento e processados para inclusão em parafina para estudo histológico. Cortes de 5 µm de espessura foram corados pelo HE e destinados a estudo em microscopia de luz. Analisou-se a histomorfologia do endométrio, área endometrial, número e área ocupada pelas glândulas, assim como a concentração de eosinófilos presentes na lâmina própria. Os dados numéricos obtidos foram submetidos à análise de variância complementada pelo teste de Tukey-Kramer (p < 0,05). RESULTADOS: Verificou-se que o peso do útero, as áreas endometrial e glandular e o número de glândulas e de eosinófilos foram maiores nos animais dos grupos GES250 > GES125 do que nos outros grupos (GES250 > GES125 > GES42 = GCtrl; p < 0,05). Os dados morfológicos mostraram proliferação endometrial nos grupos ES125 e ES250, que apresentavam endométrio mais desenvolvido que outros grupos. Em todos os animais do grupo ES250 notou-se a presença de metaplasia escamosa. CONCLUSÃO: A administração de isoflavonas em altas doses promove metaplasia escamosa no endométrio.

OBJECTIVE: To evaluate the effects of high-dose isoflavones on the uterus of castrated adult rats. METHODS: Adult, ovariectomized virgin rats (n = 40) were treated by gavage during 30 consecutive days with vehicle (propylene glycol, group GCtrl) or different doses of genistein: 42 (group GES42), 125 (GES125), or 250 (GES250) µg/g body weight per day. Animals were killed, weighed, vaginal and uterine samples were taken for cytologic evaluation, and serum levels of 17 β-estradiol and progesterone were determined. The middle third of the uterine horns was dissected, fixed in 10 percent formaldehyde and processed for paraffin inclusion; 5-µm thick sections were obtained and stained with HE for further histological study under light microscopy. The endometrial morphology and area, number and area of glands, and number of eosinophils in the lamina propria were analyzed. ANOVA and the Tukey-Kramer test were used for statistical analyses. RESULTS: Uterine weight, endometrial glandular area, and number of glands and eosinophils were all higher in GES250 > G125 than in the other groups (GES250 > GES125 > GES42 = GCtrl; p < 0.05). Morphological data showed signs of endometrial proliferation upon treatment with genistein, especially in animals in GES125 and GES250 compared to other groups. In all animals in GES250, signs of uterine squamous metaplasia were observed. CONCLUSION: A short treatment period with high daily doses of isoflavones can promote endometrial squamous metaplasia in ovariectomized rats.

Efeitos de altas doses de genisteína sobre o epitélio mamário de ratas / Effects of high doses of genistein on mammary gland of female rat

OBJETIVO: avaliar os efeitos de altas doses de genisteína sobre o epitélio mamário de ratas adultas. MÉTODOS: após 28 dias da ooforectomia, cinquenta ratas adultas foram divididas em cinco grupos, a saber: um controle (Ctrl), três que receberam genisteína (GEN) nas doses de 46 mg/kg (GEN46), 125 mg/kg (GEN125) e 250 mg/kg (GEN250), e um que recebeu estrogênios conjugados equinos na dose de 50 µg/kg (ECE). As substâncias foram administradas diariamente durante 30 dias consecutivos por gavagem e na última semana de tratamento foi efetuado exame colpocitológico durante sete dias consecutivos. Após o tratamento, os animais foram anestesiados, amostras de sangue foram retiradas para determinação do estradiol e da progesterona, e o primeiro par de mamas inguinais retirado e processado para análise histomorfométrica. Os dados obtidos foram submetidos à análise de variância complementada pelo teste de Tukey-Kramer (p<0,05). RESULTADOS: nos grupos Ctrl e tratados com as diferentes doses de GEN as mamas apresentaram-se atróficas, no entanto mostraram-se desenvolvidas no grupo ECE, onde se notou a presença de inúmeros ductos e alvéolos mamários contendo material eosinófilo em seu interior. A morfometria mostrou maior área de parênquima mamário no grupo ECE (98.870,1±550,4 µm²* por mm²; p<0,05) comparado aos outros grupos (Ctrl=36.875,6±443,4; GEN46=37.001,7±557,4; GEN125=36.480,8±658,3 e GEN250=37.502,8±669,3). O mesmo ocorreu em relação ao número de alvéolos e ductos mamários no grupo ECE (33,2±6,9* por mm²; p<0,05) em relação aos outros grupos (Ctrl=10,4±2,1, GEN 46=11,2±3,1; GEN 125=11,6±2,1 e GEN 250=12,3±2,3). Os níveis de estradiol mostraram-se aumentados no grupo ECE em relação aos outros grupos (9,4±1,7 pg/mL; p<0,05), sendo que os níveis séricos de progesterona mostraram-se semelhantes em todos os grupos de estudo. CONCLUSÃO: a administração de genisteína em altas doses não apresentou efeito proliferativo no tecido mamário de ratas.

PURPOSE: to evaluate the effects of high doses of genistein on the mammary glands of adult female rats. METHODS: Twenty-eight days after oophorectomy, 50 adult female rats were divided into five groups, as follows: a control group (Ctrl), three rats that received genistein (GEN) at the doses of 46 mg/kg (GEN46;), 125 mg/kg (GEN125) and 250 mg/kg (GEN250); one group received conjugated equine estrogen at the dose of 50 µg/g (ECE50). The substances were administered daily for 30 consecutive days by gavage and in the last week of the period of treatment, colpocytological exams were carried out for seven consecutive days. After treatment, the animals were anesthetized, blood samples were collected for estradiol and progesterone determination and the first pair of inguinal mammary glands was removed and processed for histomorphometric analysis. Collected data were subjected to analysis of variance supplemented by the Tukey-Kramer test (p<0.05). RESULTS: the ctrl group and the ones treated with different doses of GEN showed atrophic mammary glands, whereas the glands were more developed in the ECE group, where numerous mammary ducts and alveoli were observed. Morphometry showed a larger area of mammary parenchyma in the ECE group (98.870.1±550.4 µm²* per mm²; p<0.05) compared with other groups (Ctrl=36.875.6±443.4; GEN46=37.001.7±557.4; GEN125=36.480.8±658.3 and GEN250=37.502.8±669.3). The same occurred in the number of alveoli in the ECE group (33.2±6.9* per mm²; p<0.05) compared to the other groups (Ctrl=10.4±2.1, GEN46=11.2±3.1; GEN125=11.6±2.1 and GEN250=12.3±2.3). The estradiol level was higher in the ECE group compared to the other groups (9.4±1.7 pg/mL; p<0.05), whereas serum levels of progesterone were similar in all groups. CONCLUSION: the administration of genistein at high doses had no trophic effect on the mammary glands of rats.

Ação das isoflavonas no estresse oxidativo na pós-menopausa da mulher: [revisão] / Effect of isoflavones on oxidative stress in postmenopausal woman: [review]

O presente trabalho apresenta uma revisão bibliográfica da ação das isoflavonas como agentes antioxidantes. Refere que a geração de radicais reativos ao oxigênio dentro da célula faz parte do metabolismo celular, o que culmina no desenvolvimento de mecanismos de defesa antioxidantes para a retirada desses radicais. Inúmeros trabalhos referem que os asiáticos apresentam menor índice de tumores mamários, de endométrio e de próstata, o que pode estar correlacionado com o mecanismo da ação das isoflavonas, tanto como moduladores seletivos dos receptores hormonais (SERMs) quanto por sua ação antioxidante. No entanto, procuramos chamar a atenção para sua ação antioxidante.

This paper presents a brief review of the action of isoflavones as antioxidants. Being the generation of free radicals within the cell a part of the cell metabolism, evolution predictably developed efficient antioxidant defense mechanisms to remove these radicals. Numerous studies report that Asians have lower rates of breast tumors, endometrial and prostate, a fact which could be postulated to correlate with the moderate to high daily intake of isoflavones-containing foods by these human groups. The effects of isoflavones significantly lowering cancer rates can be accounted for not only by their antioxidant action but by their action as selective hormone receptor modulators (SERMs) as well. This review focuses on the antioxidantaction of isoflavones.

Plasma levels of genistein following a single dose of soy extract capsule in Indian women.

BACKGROUND & OBJECTIVE: Soy isoflavones are being used as therapy for menopausal syndrome in many countries. Marketed preparations show variability in bioavailability and there are variations in kinetics due to ethnicity and diet. Inspite of soy isoflavone being available in the Indian market there are no studies to show whether the preparation is likely to be effective in women. This study was carried out to determine circulating levels of genistein, a bioactive soy isoflavone, in Indian women after a single dose of soy extract. METHODS: Six healthy vegetarian women volunteers, between 36 and 62 yr and with a mean body mass index (BMI) 25.01+/-2.02 (kg/m2), were enrolled after an informed consent. Women with antibiotic or Soy food intake within 1 month of study were excluded. A single dose of standardized soy extract capsule containing 64.12 mg of total isoflavones (genistein content equivalent to 31.76 mg) was ingested under supervised fasting condition and multiple blood samples were collected at 0, 1, 2, 4, 6, 8 and 24 h. Genistein levels were measured by high performance liquid chromatography (HPLC) method with a detection level of 2.5 ng/100 microl of injection volume. The intra- and inter-assay coefficients of variation were < 5.32 per cent. RESULTS: Genistein was detected (10.3 to 16.2 ng/ml) in 3 volunteers in baseline samples. Within one hour genistein levels rose from 42 ng to 215 ng/ml with a maximum concentration of 117 to 380 ng/ml at 4 to 8 h. A secondary peak suggestive of enterohepatic circulation was seen between 4 and 6 h in 2 out of 6 volunteers. The mean Cmax was 315.5 +/- 57.1 ng/ml. All women had detectable levels from 25.2 to 109.3 ng/ml at 24 h. INTERPRETATION & CONCLUSION: Our study showed adequate circulating levels of genistein in Indian vegetarian women after a single dose of soy extract. Variability in plasma levels of the soy isoflavones may explain differences in responses to therapy.