Developmental effects of dietary phytoestrogens in Sprague-Dawley rats and interactions of genistein and daidzein with rat estrogen receptors α and β in vitro
Developmental effects of dietary phytoestrogens in Sprague-Dawley rats and interactions of genistein and daidzein with rat estrogen receptors α and β in vitro
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DOI：
10.1093/toxsci/51.2.236
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发表时间：
1999-10-01
影响因子：
3.8
通讯作者：
Heck, HD
中科院分区：
文献类型：
--
作者：
Casanova, M;You, L;Heck, HD
雌激素类黄酮，如染料木黄酮和大豆黄酮，几乎存在于所有以大豆为蛋白质来源的天然成分啮齿动物饮食中。由于这些化合物具有内分泌活性，因此确定啮齿类动物饮食中存在的量是否足以影响性发育非常重要。本研究包括体外和体内两部分。在体外部分中，人肝癌细胞用大鼠雌激素受体（ER）α或β加雌激素响应性荧光素酶报告基因转染。染料木黄酮和大豆苷元是两种ER的完全激动剂，染料木黄酮比大豆苷元更有效，两种化合物对ER β的作用比ER α更有效。在与雌二醇的联合研究中，金雀异黄素在体外与雌二醇产生累加效应。在研究的体内部分中，六只怀孕的Sprague-Dawley雌性动物的组被喂食以下四种饮食之一，并且幼仔保持相同的饮食直到青春期：（1）每100 g饲料含有16 mg染料木黄酮和14 mg大豆苷元的天然成分、开放式啮齿动物饮食（NIH-07）：（2）不含大豆和苜蓿的饮食（SAFD），其中酪蛋白和玉米油分别代替不含可检测到的大豆黄酮的大豆和苜蓿粉以及大豆油;（4）含有0.1%染料木黄酮的SAFD（GE.1）。在GE.1组中，饮食染料木素的影响包括体重增加率降低，出生后第21天（PND）子宫/体重（U/BW）比值显著增加（2.3倍），雌性青春期显著加速，出生后第56天（PND）腹侧前列腺重量略有下降。然而，喂食SAFD、GE.02或NIH-07的各组之间的发育差异很小，表明在正常饮食水平下植物雌激素的影响很小。特别是，在pnd 21，GE. 02和NIH-07组的U/BW比与SAFD组无显著差异。在喂食SAFD和NIH-07的组之间仅检测到一个统计学显著差异：喂食NIH-07的母鼠在出生后第1天的雌性新生儿的肛门生殖器距离（AGD）比喂食SAFD的母鼠的新生儿大12%。结果表明，在天然成分的啮齿动物饮食中的植物雌激素的正常量可能会影响一个发育参数，女性AGD，和更高的剂量可以影响其他几个参数在男性和女性。基于这些发现，我们不建议在大多数发育毒理学研究中用不含植物雌激素的饮食取代以大豆和苜蓿为基础的啮齿动物饮食。然而，建议在低剂量的内分泌毒理学研究中使用不含植物雌激素的饮食，以确定饮食中的植物雌激素和人造化学品之间是否会发生相互作用。
Estrogenic isoflavones, such as genistein and daidzein, are present in virtually all natural-ingredient rodent diets that use soy as a source of protein. Since these compounds are endocrine-active, it is important to determine whether the amounts present in rodent diets are sufficient to affect sexual development. The present study consisted of in vitro and in vivo parts. In the in vitro portion, human hepatoma cells were transfected with either rat estrogen receptor (ER) alpha or beta plus an estrogen-responsive luciferase reporter gene. Genistein and daidzein were complete agonists at both ERs, genistein being more potent than daidzein, and both compounds were more potent at ER beta than ER alpha. In combined studies with estradiol, genistein exerted additive effects with estradiol in vitro. In the in vivo portion of the study, groups of six pregnant Sprague-Dawley females were fed one of the following four diets, and the pups were maintained on the same diets until puberty: (1) a natural-ingredient, open-formula rodent diet (NIH-07) containing 16 mg genistein and 14 mg daidzein per 100 g of feed: (2) a soy- and alfalfa-free diet (SAFD) in which casein and corn oil were substituted for soy and alfalfa meal and soy oil, respectively, that contained no detectable isoflavones; (3) SAFD containing 0.02% genistein (GE.02); or (4) SAFD containing 0.1% genistein (GE.1). In the GE.1 group, effects of dietary genistein included a decreased rate of body-weight gain, a markedly increased (2.3-fold) uterine/body weight (U/BW) ratio on postnatal day (pnd) 21, a significant acceleration of puberty among females, and a marginal decrease in the ventral prostate weight on postnatal day (pnd) 56. However, developmental differences among the groups fed SAFD, GE.02, or NIH-07 were small and suggested minimal effects of phytoestrogens at normal dietary levels. In particular, on pnd 21, the U/BW ratio of the GE.02 and NIH-07 groups did not differ significantly from that of the SAFD group. Only one statistically significant difference was detected between groups fed SAFD and NIH-07: the anogenital distance (AGD) of female neonates on pnd 1 whose dams were fed NIH-07 was 12% larger than that of neonates whose dams were fed SAFD. The results suggest that normal amounts of phytoestrogens in natural-ingredient rodent diets may affect one developmental parameter, the female AGD, and that higher doses can affect several other parameters in both males and females. Based on these findings, we do not suggest replacing soy- and alfalfa-based rodent diets with phytoestrogen-free diets in most developmental toxicology studies. However, phytoestrogen-free diets are recommended for endocrine toxicology studies at low doses, to determine whether interactive effects may occur between dietary phytoestrogens and man-made chemicals.