Estrogenic agonism and antagonism of the soy isoflavone genistein in uterus, bone and lymphopoiesis in mice

Malic Enzyme 1 (ME1) Promotes Adiposity and Hepatic Steatosis and Induces Circulating Insulin and Leptin in Obese Female Mice

Malic Enzyme 1 (ME1) supports lipogenesis, cholesterol synthesis, and cellular redox potential by catalyzing the decarboxylation of L-malate to pyruvate, and the concomitant reduction of NADP to NADPH. We examined the contribution of ME1 to the development of obesity by provision of an obesogenic diet to C57BL/6 wild type (WT) and MOD-1 (lack ME1 protein) female mice. Adiposity, serum hormone levels, and adipose, mammary gland, liver, and small intestine gene expression patterns were compared between experimental groups after 10 weeks on a diet. Relative to WT female mice, MOD-1 female mice exhibited lower body weights and less adiposity; decreased concentrations of insulin, leptin, and estrogen; higher concentrations of adiponectin and progesterone; smaller-sized mammary gland adipocytes; and reduced hepatosteatosis. MOD-1 mice had diminished expression of Lep gene in abdominal fat; Lep, Pparg, Klf9, and Acaca genes in mammary glands; Pparg and Cdkn1a genes in liver; and Tlr9 and Ffar3 genes in the small intestine. By contrast, liver expression of Cdkn2a and Lepr genes was augmented in MOD-1, relative to WT mice. Results document an integrative role for ME1 in development of female obesity, suggest novel linkages with specific pathways/genes, and further support the therapeutic targeting of ME1 for obesity, diabetes, and fatty liver disease.

Skeletal impact of 17β-estradiol in T cell-deficient mice: age-dependent bone effects and osteosarcoma formation

Estrogen (E₂)-dependent ER+ breast cancer, the most common breast cancer subtype, is also the most likely to metastasize to bone and form osteolytic lesions. However, ER+ breast cancer bone metastasis human xenograft models in nude mice are rarely studied due to complexities associated with distinguishing possible tumoral vs. bone microenvironmental effects of E₂. To address this knowledge gap, we systematically examined bone effects of E₂ in developing young (4-week-old) vs. skeletally mature (15-week-old) female Foxn1^nu nude mice supplemented with commercial 60-day slow-release E₂ pellets and doses commonly used for ER+ xenograft models. E₂ pellets (0.05-0.72 mg) were implanted subcutaneously and longitudinal changes in hind limb bones (vs. age-matched controls) were determined over 6 weeks by dual-energy X-ray absorptiometry (DXA), microCT, radiographic imaging, and histology, concurrent with assessment of serum levels of E₂ and bone turnover markers. All E₂ doses tested induced significant and identical increases in bone density (BMD) and volume (BV/TV) in 4-week-old mice with high bone turnover, increasing bone mineral content (BMC) while suppressing increases in bone area (BA). E₂ supplementation, which caused dose-dependent changes in circulating E₂ that were not sustained, also led to more modest increases in BMD and BV/TV in skeletally mature 15-week-old mice. Notably, E₂-supplementation induced osteolytic osteosarcomas in a subset of mice independent of age. These results demonstrate that bone effects of E₂ supplementation should be accounted for when assessing ER+ human xenograft bone metastases models.

Human-relevant potency threshold (HRPT) for ERα agonism

The European Commission has recently proposed draft criteria for the identification of endocrine disrupting chemicals (EDCs) that pose a significant hazard to humans or the environment. Identifying and characterizing toxic hazards based on the manner by which adverse effects are produced rather than on the nature of those adverse effects departs from traditional practice and requires a proper interpretation of the evidence regarding the chemical’s ability to produce physiological effect(s) via a specific mode of action (MoA). The ability of any chemical to produce a physiological effect depends on its pharmacokinetics and the potency by which it acts via the various MoAs that can lead to the particular effect. A chemical’s potency for a specific MoA—its mechanistic potency—is determined by two properties: (1) its affinity for the functional components that comprise the MoA, i.e., its specific receptors, enzymes, transporters, transcriptional elements, etc., and (2) its ability to alter the functional state of those components (activity). Using the agonist MoA via estrogen receptor alpha, we illustrate an empirical method for determining a human-relevant potency threshold (HRPT), defined as the minimum level of mechanistic potency necessary for a chemical to be able to act via a particular MoA in humans. One important use for an HRPT is to distinguish between chemicals that may be capable of, versus those likely to be incapable of, producing adverse effects in humans via the specified MoA. The method involves comparing chemicals that have different ERα agonist potencies with the ability of those chemicals to produce ERα-mediated agonist responses in human clinical trials. Based on this approach, we propose an HRPT for ERα agonism of 1E-04 relative to the potency of the endogenous estrogenic hormone 17β-estradiol or the pharmaceutical estrogen, 17α-ethinylestradiol. This approach provides a practical way to address Hazard Identification according to the draft criteria for identification of EDCs recently proposed by the European Commission.

Evaluation of the isoflavones and estrogen effects on the rat adrenal

The aim of this study was to evaluate the morphometry and the gene expression of Ki-67, VEGF and caspase 3 and the stress oxidative in the adrenal gland of ovariectomized rats treated with estrogen or isoflavones. We used 15 Wistar rats ovariectomized treated with isoflavones or estrogen during 30 days. At the end of the treatment, the left adrenal gland was removed for subsequent histological studies and the right was used to evaluate gene expression of angiogenesis (VEGF-A), cell proliferation (Ki-67), apoptose (caspase 3 clivated) and oxidative stress. Treatment with estrogen showed a largest increase in the layers of the adrenal cortex than with isoflavones. These hypertrofic effects agree with higher expression elevation of Ki67 and VEGF, which did not occur with the caspase 3, indicating that isoflavones have great proliferative effect on the adrenal gland. Similar results were also observed on superoxide quantification show that isoflavone has a protective effect against oxidative stress. Our results indicate positively the trophic therapeutic potential of isoflavones has a protective effect and can contribute to the development of effective therapies to decrease the symptoms of menopause.

Genistein treatment increases bone mass in obese, hyperglycemic mice

BACKGROUND

Obesity and type 2 diabetes mellitus are associated with elevated risk of limb bone fracture. Incidences of these conditions are on the rise worldwide. Genistein, a phytoestrogen, has been shown by several studies to demonstrate bone-protective properties and may improve bone health in obese type 2 diabetics.

METHODS

In this study, we test the effects of genistein treatment on limb bone and growth plate cartilage histomorphometry in obese, hyperglycemic ob/ob mice. Six-week-old ob/ob mice were divided into control and genistein-treated groups. Genistein-treated mice were fed a diet containing 600 mg genistein/kg for a period of 4 weeks. Cross-sectional geometric and histomorphometric analyses were conducted on tibias.

RESULTS

Genistein-treated mice remained obese and hyperglycemic. However, histomorphometric comparisons show that genistein-treated mice have greater tibial midshaft diameters and ratios of cortical bone to total tissue area than the controls. Genistein-treated mice also exhibit decreased growth plate thickness of the proximal tibia.

CONCLUSION

Our results indicate that genistein treatment affects bone of the tibial midshaft in the ob/ob mouse, independent of improvements in the hyperglycemic state and body weight.

Soy Isoflavones and Osteoporotic Bone Loss: A Review with an Emphasis on Modulation of Bone Remodeling

Osteoporosis is an age-related disorder that affects both women and men, although estrogen deficiency induced by menopause accelerates bone loss in older women. As the demographic shifts to a more aged population, a growing number of men and women will be afflicted with osteoporosis. Since the current drug therapies available have multiple side effects, including increased risk of developing certain types of cancer or complications, a search for potential nonpharmacologic alternative therapies for osteoporosis is of prime interest. Soy isoflavones (SI) have demonstrated potential bone-specific effects in a number of studies. This article provides a systematic review of studies on osteoporotic bone loss in relation to SI intake from diet or supplements to comprehensively explain how SI affect the modulation of bone remodeling. Evidence from epidemiologic studies supports that dietary SI attenuate menopause-induced osteoporotic bone loss by decreasing bone resorption and stimulating bone formation. Other studies have also illustrated that bone site-specific trophic and synergistic effects combined with exercise intervention might contribute to improve the bioavailability of SI or strengthen the bone-specific effects. To date, however, the effects of dietary SI on osteoporotic bone loss remain inconclusive, and study results vary from study to study. The current review will discuss the potential factors that result in the conflicting outcomes of these studies, including dosages, intervention materials, study duration, race, and genetic differences. Further well-designed studies are needed to fully understand the underlying mechanism and evaluate the effects of SI on osteoporosis in humans.

Effects of genistein in combination with conjugated estrogens on endometrial hyperplasia and metabolic dysfunction in ovariectomized mice

Tissue-selective estrogen complex (TSEC), which combines a selective estrogen receptor modulator (SERM) with one or more estrogens, is a novel approach to menopausal therapy. It has been demonstrated that the phytoestrogen genistein (GEN) exhibits mixed estrogen receptor agonist and antagonist activity, suggesting that GEN may have potential for use as a natural SERM. We evaluated, for the first time, the effects of GEN, conjugated estrogens (CE), and their pairing effects as a TSEC treatment on estrogen-induced endometrial hyperplasia and metabolic dysfunction in ovariectomized (OVX) mice fed a high-fat diet. CE replacement prevented fat accumulation in the adipose tissue and liver, improved glucose homeostasis, and induced endometrial hyperplasia in OVX mice. GEN at 100 mg/kg showed CE mimetic effects in preventing ovariectomy-induced metabolic dysfunctions without endometrial stimulation. Combination treatments with CE and GEN prevented metabolic dysfunctions more strongly than CE alone, but at both low and high doses, GEN did not reverse CE-induced endometrial hyperplasia. In addition, we found that in a TSEC regimen, a typical SERM raloxifene maintains the metabolic benefits of CE while simultaneously protecting the endometrium in OVX mice. These findings indicate that GEN acts as an estrogen agonist in metabolic regulation, but has no SERM function in the uteri of OVX mice.

The association of dietary quality and food group intake patterns with bone health status among Korean postmenopausal women: a study using the 2010 Korean National Health and Nutrition Examination Survey Data

BACKGROUND/OBJECTIVES

Osteoporosis and osteoporosis-related disease are drawing a lot of attention in Korea as one of the serious health problems. Bone health status may be influenced by the general dietary quality and dietary pattern.

SUBJECTS/METHODS

To determine the relationship between dietary quality and intake patterns and bone health status, the %RNI, NAR, DDS, and food group intake patterns were assessed according to their bone health status for 847 postmenopausal women using the 2010 KNHANES data after eliminating those of likely changing their diet under the advice of doctors or those taking estrogen.

RESULTS

Bone health became worse as dietary quality deteriorated. All NAR and %RNI values were highly associated with bone health levels and the consumption frequency of Ca sources, DDS and the food group intake patterns also confirmed the findings.

CONCLUSIONS

This study confirmed that dietary quality and dietary patterns were important for bone health. Nutritional education on eating foods from the five basic food groups has to be emphasized to prevent osteoporosis among older women.

Dose-dependent effects of genistein on bone homeostasis in rats' mandibular subchondral bone

AIM

To investigate the effect of genistein on bone homeostasis in mandibular subchondral bone of rats.

METHODS

Female SD rats were administered with genistein (10 and 50 mg/kg) or placebo by oral gavage for 6 weeks. Then the animals were sacrificed, and histomorphology and micro-structure of mandibular condyle were examined using HE staining and micro-CT analysis, respectively. The expression levels of alkaline phosphatase (ALP), osteocalcin (OC), osteoprotegerin (OPG), the receptor activator of nuclear factor κB ligand (RANKL) and estrogen receptors (ERs) in mandibular condyle were detected using real-time PCR. Cultured osteoblasts were prepared from rat mandibular condyle for in in vitro study. The cells were treated with genistein (10(-7) or 10(-4) mol/L) for 48 h. The expression of the bone homeostasis-associated factors and estrogen receptors (ERs) was detected using real-time PCR, and ER silencing was performed.

RESULTS

At both the low- and high-doses, genistein significantly increased the bone mineral density (BMD) and bone volume, and resulted in thicker subchondral trabecular bone in vivo. In both in vivo and in vitro study, the low-dose genistein significantly increased the expression of ALP, OC and OPG, but decreased the expression of RANKL and the RANKL/OPG ratio. The high-dose genistein decreased the expression of all these bone homeostasis-associated factors. Both the low and high doses of genistein significantly increased the expression of ERβ, while ERα expression was increased by the low dose genistein and decreased by the high dose genistein. ERβ silencing abrogated most of the effects of genistein treatment.

CONCLUSION

In rat mandibular condylar subchondral bone, low-dose genistein increases bone formation and inhibit bone resorption, while excess genistein inhibits both bone formation and resorption. The effects of genistein were predominantly mediated through ERβ.

Soy protein diet and exercise training increase relative bone volume and enhance bone microarchitecture in a mouse model of uremia

Soy protein consumption and exercise training have been widely studied for their effects on the vasculature and bone in healthy populations, but little is known about the effectiveness of these interventions in chronic kidney disease (CKD). Cardiovascular disease and bone fracture risk are significantly elevated in CKD, and current pharmacological interventions have been unsuccessful in treating these conditions simultaneously. The purpose of this study was to compare the effects of a soy protein diet and endurance exercise training, alone or in combination, on cardiovascular and bone health in a mouse model of renal insufficiency. At 8 weeks of age, 60 female apolipoprotein E(-/-) mice underwent a two-step surgical procedure to induce uremia. These mice were then randomized at 12 weeks of age to one of four treatment groups for the 16-week intervention period: sedentary, control diet (n = 16); sedentary, soy protein diet (n = 18); exercise, control diet (n = 14); and exercise, soy protein diet (n = 12). There were no significant treatment effects on atherosclerotic lesion areas or aortic calcium deposits. We demonstrated a significant main effect of both diet and exercise on relative bone volume, trabecular number, trabecular separation, and trabecular connective density in the proximal femur as measured by microcomputed tomography. There were no treatment effects on trabecular thickness. We also showed a main effect of diet on plasma urea levels. These data suggest that soy protein intake and exercise training exert beneficial effects on properties of bone and plasma urea levels in mice with surgically induced renal impairment.

Aqueous leaf extracts display endocrine activities in vitro and disrupt sexual differentiation of male Xenopus laevis tadpoles in vivo

The occurrence of natural substances acting as endocrine disrupting compounds (EDC) in the environment is to date poorly understood. Therefore, (anti)androgenic and (anti)estrogenic activities of three different aqueous leaf extracts (beech, reed and oak) were analyzed in vitro using yeast androgen and estrogen screen. The most potent extract was selected for in vivo exposure of Xenopus laevis tadpoles to analyze the potential effects on development and reproductive biology of amphibians. Tadpoles were exposed from stage 48 to stage 66 (end of metamorphosis) to aqueous oak leaf extracts covering natural occurring environmental concentrations of dissolved organic carbon. Gene expression analyses of selected genes of the hypothalamus-pituitary-gonad and of the hypothalamus-pituitary-thyroid axis as well as histological investigation of gonads and thyroid glands were used to evaluate endocrine disrupting effects on the reproductive biology and development. Female tadpoles remained unaffected by the exposure whereas males showed severe significant histological alterations of testes at the two highest oak leaf extract concentrations demonstrated by the occurrence of lacunae and oogonia. In addition, a significant elevation of luteinizing hormone beta mRNA expression with increasing extract concentration in male tadpoles indicates an involvement of hypothalamus-pituitary-gonad axis mainly via antiandrogenic activity. These results suggest that antiandrogenic EDC of oak leaf extract are responsible for inducing the observed effects in male tadpoles. The present study demonstrates for the first time that in surface waters, natural occurring oak leaf compounds at environmentally relevant concentrations display antiandrogenic activities and have considerable effects on the endocrine system of anurans affecting sexual differentiation of male tadpoles.

Antiresorptive effects of phytoestrogen supplements compared with estradiol or risedronate in postmenopausal women using (41)Ca methodology

INTRODUCTION

Reduction of ovarian estrogen secretion at menopause increases net bone resorption and leads to bone loss. Isoflavones have been reported to protect bone from estrogen deficiency, but their modest effects on bone resorption have been difficult to measure with traditional analytical methods.

METHODS

In this randomized-order, crossover, blinded trial in 11 healthy postmenopausal women, we compared four commercial sources of isoflavones from soy cotyledon, soy germ, kudzu, and red clover and a positive control of oral 1 mg estradiol combined with 2.5 mg medroxyprogesterone or 5 mg/d oral risedronate (Actonel) for their antiresorptive effects on bone using novel (41)Ca methodology.

RESULTS

Risedronate and estrogen plus progesterone decreased net bone resorption measured by urinary (41)Ca by 22 and 24%, respectively (P < 0.0001). Despite serum isoflavone profiles indicating bioavailability of the phytoestrogens, only soy isoflavones from the cotyledon and germ significantly decreased net bone resorption by 9% (P = 0.0002) and 5% (P = 0.03), respectively. Calcium absorption and biochemical markers of bone turnover were not influenced by interventions.

CONCLUSIONS

Dietary supplements containing genistein-like isoflavones demonstrated a significant but modest ability to suppress net bone resorption in postmenopausal women at the doses supplied in this study over a 50-d intervention period.

Soy isoflavones in the management of postmenopausal osteoporosis

This is a review article designed to address the effects of soy isoflavones on bone metabolism in postmenopausal women and their place in the prevention and treatment of postmenopausal osteoporosis. Soy isoflavones are natural products that could be used as an alternative to menopausal hormone therapy because they are structurally and functionally related to 17beta-estradiol. In vitro and animal studies have shown that they act in multiple ways to exert their bone-supporting effects. They act on both osteoblasts and osteoclasts through genomic and nongenomic pathways. Epidemiological studies and clinical trials suggest that soy isoflavones have beneficial effects on bone mineral density, bone turnover markers, and bone mechanical strength in postmenopausal women. However, there are conflicting results related to differences in study design, estrogen status of the body, metabolism of isoflavones among individuals, and other dietary factors. The long-term safety of soy isoflavone supplements remains to be demonstrated.

Comparison of the effects of genistein and zoledronic acid on the bone loss in OPG-deficient mice

Using osteoprotegerin (OPG)-knockout mice, we demonstrated that in vivo the effects of both genistein and 17beta-estradiol (E2) on bone metabolism were completely abolished. In contrast, zoledronic acid could effectively suppress bone resorption and prevent bone loss.

INTRODUCTION

The anti-resorptive effects of E2 on bone metabolism are considered to be mediated via modulation of the osteoblast-derived paracrine factor OPG. Recently, the phytoestrogen genistein was found to suppress bone resorption by enhancing osteoblastic production of OPG. However, the mechanism underlying the in vivo effects of E2 and genistein on bone is not entirely understood, and a central question in this regard is whether E2 regulates bone metabolism via an OPG-dependent pathway.

METHODS

After mating heterozygous (OPG+/-) mice, homozygous (OPG-/-) and wild-type (WT) with a mixed C57BL/6J x 129/SV background were obtained. The study involved 6-week-old female OPG-/- (n=40) and WT mice (n=8). The OPG-/- mice were randomly divided into 5 groups (n=8 per group) as follows: (1) genistein-treated mice (Gen) that were subcutaneously injected with genistein at a maximal dose (0.8 mg/day); (2) E2-treated mice (E2) that were subcutaneously injected with E2 at a dose (0.03 microg/day); (3) DMSO control mice (DMSO) that were subcutaneously injected with a mixture of dimethylsulfoxide (DMSO) and polyethyleneglycol-300; (4) zoledronic acid-treated mice (Zol) that were subcutaneously injected with zoledronic acid at a dose of (150 microg/kg) twice per week; and (5) H2O control mice that were subcutaneously injected with sterilized water twice per week. The doses of genistein, estrogen and zoledronic acid were selected based on the results of dose-response effect of agents on bone versus uterus in OPG-/- mice. The mice were sacrificed 6 weeks after this intervention. The microarchitecture of the trabecular and cortical bone was assessed by performing microcomputed tomography (micro-CT) for the right proximal tibia. The bone mineral density (BMD) of the left femur was measured by dual-energy X-ray absorptiometry (DXA). The biomechanical parameters of the right femur were determined by a three-point bend testing. Serum levels of bone alkaline phosphatase (B-ALP), tartarate-resistant acid phosphatase-5b (TRACP-5b), and receptor activator of nuclear factor kappaB ligand (RANKL) were determined by performing ELISA.

RESULTS

DXA analysis revealed that the total BMD of the femur was not significantly altered in the Gen, E2, H2O, and DMSO groups. The three-point bending test revealed no significant differences in the biomechanical parameters, including ultimate loading, ultimate stress, stiff index, and elastic modulus, and micro-CT analysis revealed that the microarchitectural parameters of the trabecular bone (vBMD, tBMD, BVF, BSF, SMI, Tb.N, Conn.D, Tb.Sp, and Tb.Th) and cortical bone (Ct.Th, Mm, In.Pm, Ot.Pm, Ma.Ar, Ct.Ar, Tt.Ar, Ct.BMD, and Ct.BMC) did not differ among the groups. Genistein and E2 treatment did not alter the serum TRACP-5b, B-ALP, or RANKL levels. However, in addition to increasing the bone mass, zoledronic acid could effectively improve biomechanical parameters and could completely prevent deterioration of the bone architecture in the OPG-/- mice.

CONCLUSIONS

The effects of genistein and E2 on bone metabolism in vivo were lost completely in OPG-deficient mice, suggesting that the effect of these agents on bone metabolism seems to be entirely dependent on OPG. In contrast, zoledronic acid could effectively suppress bone resorption and completely prevent the bone loss in the OPG-/- mice--an effect that is likely to be independent of the OPG pathway.

Bone development in female rats maintained with soy-free or soy-containing food as determined by computer-assisted tomography and serum bone markers

The development of bone in immature rats and in aged rats has not been thoroughly studied. Therefore, we investigated the development of bones in young, middle-aged, and aged female rats. Because most rat chows contain soy proteins, including estrogenic isoflavones, as a source of protein, comparison of effects on mineral density and on areas of the cancellous and cortical parts of the metaphysis of the tibia as measured by quantitative computer tomography in animals fed with soy-free and soy-containing food was made. As surrogate parameters of bone metabolism serum, osteocalcin (OC) and the breakdown products of bone collagen--the Crosslaps--were also determined. The cancellous density increased between day 25 after birth to reach peak bone mass at 90 days of age; in 18-and 20-month-old animals, significant reduction was observed that was more profound in the animals fed with soy-free food. Serum OC and the Crosslaps were highest in 15-day-old and lowest in 9-, 18-, and 20-month-old animals. Animals fed with soy-containing food had significantly higher osteocalcin levels at day 15 and at 9 and 18 months of age. In the aged animals, intake of soy isoflavones that have an estrogenic effect appears to exert beneficial effects as these aged animals lost less cancellous bone, as indicated by their surrogate parameters of metabolism in the serum. It is concluded that exorbitantly high bone turnover is present in immature and peripubertal rats. Raising and keeping female rats under soy-free or soy-containing conditions has marked effects on several bone parameters that are of particular relevance in aged animals.

Isoflavones--safe food additives or dangerous drugs?

The sales volume of products containing isoflavone has increased since the publication of the Women's Health Initiative. The many apparently contradictory results published on the effects of isoflavones on a variety of estrogen-regulated organs point to both beneficial as well as adverse effects on human health. It is of particular importance that psychovegetative climacteric complaints such as hot flushes are, if at all, only slightly influenced by isoflavones. The substances appear to have weak anti-osteoporotic effect. Their anti-atherosclerotic action is debatable, as not all authors find any beneficial effect on lipids. Most importantly, there is dispute as to whether isoflavones derived from soy or red clover have negative, positive or any effect at all on the mammary gland or endometrium. It is beyond any doubt that soy products may have cancer preventing properties in a variety of organs including the mammary gland. However, these properties may only be exerted if the developing organ was under the influence of isoflavones during childhood and puberty. This may also explain the often quoted "Japanese Phenomenon", the fact that breast cancer occurs to a lesser extent in Japanese women. When administered to isoflavone "inexperienced" women at the time of menopause, the phytoestrogens appear to share the same effects as estrogen used in classical preparations for hormone replacement therapy, i.e. they may stimulate the proliferation of endometrial and mammary gland tissue with at present unknown and unpredictable risk to these organs. Therefore, the following question arises for the clinician: Why should soy or red clover products containing isoflavone be recommended, if the positive effects are only negligible but the adverse effects serious?

Bone mass and soy isoflavones in socially housed, premenopausal macaques

BACKGROUND

Soy consumption is associated with a lower incidence of hip fracture in Asian than in Western women, an effect often attributed to estrogen-like compounds (isoflavones) in soy. It is not known whether premenopausal soy exposure initiated in adulthood can increase bone mass and thereby reduce fracture risk.

OBJECTIVE

We aimed to determine whether a high-isoflavone soy diet influences bone mass in soy-naïve, premenopausal cynomolgus monkeys (Macaca fascicularis).

DESIGN

Ninety-four skeletally mature females were randomly assigned to consume diets whose protein content came from either high-isoflavone soy or casein and lactalbumin. Animals were socially housed. Bone mass and circulating isoflavone concentrations were measured at baseline and 19 and 31 mo after the start of treatment; bone biomarkers were measured at baseline and 31 mo.

RESULTS

There were no significant differences at any timepoint in whole-body bone mineral content between casein-fed (112.5 +/- 2.1, 119.2 +/- 1.9, and 120.7 +/- 2.1 g) and soy-fed (117.2 +/- 2.1, 122.4 +/- 2.0, and 125.4 +/- 2.3 g; P=0.12) monkeys. Similar results were seen for spinal bone mineral density (casein-fed: 0.46 +/- 0.01, 0.50 +/- 0.01, and 0.52 +/- 0.01 g/cm(2); soy-fed: 0.47 +/- 0.01, 0.51 +/- 0.01, and 0.52 +/- 0.01 g/cm(2); P=0.30) and bone biomarker measurements-bone-specific alkaline phosphatase (soy-fed: 82.3 +/- 4.1 and 63.2 +/- 3.4 ng/mL; casein-fed: 94.1 +/- 4.5 and 61.7 +/- 4.3 ng/mL; P=0.22) and C-terminal crosslink of type 1 collagen (soy-fed: 0.944 +/- 0.06 and 0.89 +/- 0.08 nmol/L; casein-fed: 0.97 +/- 0.07 and 0.78 +/- 0.06 nmol/L; P=0.20).

CONCLUSION

A soy diet high in isoflavones does not significantly affect bone characteristics in initially soy-naïve premenopausal monkeys.

The effects of soy extract on the uterus of castrated adult rats

OBJECTIVE

The aim of this study was to evaluate the effects of different doses of a standardized soy extract on the uterus of castrated rats.

METHODS

Fifty-six adult castrated female Wistar rats were randomly divided into seven groups (eight animals in each) that received: GI--drug vehicle (propylene glycol); GII--soy extract 10mg/kg per day; GIII--soy extract 50mg/kg per day; GIV--soy extract 100mg/kg per day; GV--soy extract 300mg/kg per day; GVI--soy extract 600mg/kg per day; GVII-conjugated equine estrogens (CEE) 200microg/kg per day. After 21 days of treatment, all animals were sacrificed and fragments of the uterine horns were immediately removed, fixed in 10% formaldehyde and submitted to routine histological techniques for morphometric study. The endometrial cell proliferation index was determined with the PCNA antibody PC-10 and expressed as the percentuals of the PCNA-positive nuclei relative to the total countings. Other fragments were immediately frozen in liquid nitrogen for RNA extraction and VEGF analysis using RT-PCR technique.

RESULTS

The minimal dose of soy extract that produced a significant increase of the morphometric parameters was 100mg/kg (GIV). The maximum effects on endometrial and myometrial morphometry were detected in the groups treated with 300 and 600mg/kg of soy extract (groups V and VI) and CEE (GVII). The expression of PCNA in the endometrial epithelium and stroma was increased by treatment with 100-600mg/kg per day of soy extract (groups IV-VI) or with CCE (group VII). Doses equal to or higher than 50mg/kg of soy extract (groups III-VI) and CEE stimulated the expression of VEGF.

CONCLUSION

The treatment of adult castrated rats during 21 days with doses of 100mg/kg per day or higher of soy extract may determine significant proliferation in the endometrium and myometrium.

Lack of Estrogenic or Antiestrogenic Actions of Soy Isoflavones in an Avian Model: The Japanese Quail

Isoflavones are soy compounds that possess weak estrogenic and antiestrogenic activities. In addition, phytochemicals, including isoflavones, may play a role in regulating seasonal reproductive cycles. As soy is a common constituent in poultry diets, the effect of these compounds on the reproductive system of production birds may be of concern. The present study examined the putative effects of soy isoflavones supplemented into the diet at 1 and 5% using endpoints of growth and reproduction in the Japanese quail. Isoflavones did not exert an effect on growth, feed intake, growth:feed, or the weight of the estrogen-sensitive immature oviduct in female quail. Furthermore, isoflavones did not influence the growth of the oviduct stimulated by exogenous estradiol. Similarly, isoflavones did not influence growth, feed intake, or growth:feed in male quail. However, isoflavones at 1%, but not 5%, in the diet reduced photoperiod-induced testis development 40% vs. control. In contrast, isoflavones did not influence testis regression stimulated by exogenous estradiol in sexually maturing male quail. The present results suggest that isoflavones may exert modest endocrine disruptor-like effects on reproduction in male, but not female, quail.

Genistein alone and in combination with the mammalian lignans enterolactone and enterodiol induce estrogenic effects on bone and uterus in a postmenopausal breast cancer mouse model

The use of phytoestrogens, such as isoflavones and lignans, for treatment of postmenopausal breast cancer is increasing, but their effects on bone and other major organs are not clear. While the isoflavone genistein (GEN) has been shown to prevent or slow the loss of bone mineral density (BMD), the effect of lignans enterodiol (END) and enterolactone (ENL) are unknown. In this study, we determined in ovariectomized mice with human MCF-7 breast tumor xenografts the effects of the lignans, and GEN, alone and in combination, on bone and uterus. Mice with established MCF-7 tumors were fed a basal diet (AIN-93G), divided into 5 groups, and given daily subcutaneous injections (10 mg/kg body weight) of either ENL, END, GEN, a mixture of these compounds (MIX), or vehicle as a negative control for 22 weeks. Results showed that GEN acts estrogenically in both the uterus and bone by increasing the uterus weight, femur BMD, and femur biomechanical strength (yield load), while the lignans do not. However, treatment with MIX induced minimal effects on femur biomechanical strength parameters but significantly increased uterus weight. A significant positive correlation was observed between MCF-7 tumor volume and femur BMD and biomechanical strength parameters (femur peak load and yield load) but not with uterus weight, suggesting that the uterus may respond differently to phytoestrogens compared to MCF-7 tumors and bone. It is concluded that GEN induces beneficial effects on bone but has adverse effects on tumors and uterus in this model of postmenopausal breast cancer. The lignans do not exert adverse effects on any tissue, however, when combined with GEN, they exert an adverse effect on the uterus.

Genistein stimulates growth of human breast cancer cells in a novel, postmenopausal animal model, with low plasma estradiol concentrations

We have demonstrated that genistein (GEN) stimulates growth of estrogen-dependent breast tumors in vivo. In this study, we evaluated whether dietary GEN can act in an additive manner with low circulating levels of 17beta-estradiol (E2). We developed an E2 delivery system using silastic implants that yield low circulating plasma E2 levels similar to those observed in postmenopausal women. We inserted various concentrations of E2 silastic implants (1:127, 1:63, 1:31, 1:15 and 1:7 = E2:cholesterol) and injected estrogen-dependent human breast cancer (MCF-7) cells into ovariectomized athymic mice. The E2 implants tested (1:127-1:7) generated 30.1-101.6 pM E2 in plasma, which is comparable to the E2 levels observed in postmenopausal women. The E2 implants stimulated MCF-7 tumor growth in a dose-dependent manner. We selected the 1:31 ratio of E2 implant to evaluate if dietary GEN acts in an additive manner with low E2 levels to influence the growth of MCF-7 tumors. Ovariectomized mice were divided into four groups: MCF-7 control, 500 ppm GEN, 1:31 E2, and 1:31 E2 + 500 ppm GEN. At week 17, the average tumor sizes were 7.6, 32.1, 67.4 and 106.8 mm2 for these groups, respectively (P < 0.05), demonstrating that 500 ppm GEN additively stimulated MCF-7 tumor growth in the presence of low levels of E2. In summary, we established a preclinical mouse model that results in E2 blood concentrations similar to those found in postmenopausal women. Further, we observed that these concentrations regulate the growth rate of MCF-7 breast tumors. Using this model, we demonstrated that dietary GEN in the presence of low levels of circulating E2 act in an additive manner to stimulate estrogen-dependent tumor growth in vivo. Results from this study suggest that consumption of products containing GEN may not be safe for postmenopausal women with estrogen-dependent breast cancer.

Soy isoflavones and bone health: a double-edged sword?

Numerous publications and research studies on isoflavones have prompted a nationwide increase in the consumption of soy-based foods and supplements in the United States. Isoflavones are natural endocrine active compounds generally considered to promote health and prevent or slow the onset of certain chronic diseases such as osteoporosis. The beneficial effects of soy isoflavones on bone may, however, be life-stage specific and dependent on the estrogen receptor number and endogenous hormone milieu. Perimenopausal and early menopausal women may therefore be more receptive to the therapeutic effects of isoflavones on bone loss prior to the diminution of estrogen receptors that occurs in the postmenopausal years, whereas laboratory studies in developmental age range animals have demonstrated the potential for adverse effects following exposure to high levels of soy isoflavones. Clinical studies in developing humans that either support or refute findings in animal studies are lacking. The effects of chronic consumption of high levels of soy isoflavones at each life stage to assess risk-benefit ratios should be a high priority of research.

Immune responses and bone loss: the estrogen connection

In addition to its effects on sexual differentiation and reproduction, estrogen has important impact on the immune system and on bone. It has also been evident that the effects of estrogen on bone to a large extent are mediated via its action on immune cells. Estrogen has a dichotomous impact on the immune system by downregulation of inflammatory immune responses but simultaneous upregulation of immunoglobulin production. Consequently, immune-mediated diseases in humans and in animal models are modulated by estrogen. Estrogen deficiency after ovariectomy in mice and after menopause in women is associated with significant bone loss. In rheumatic diseases such as rheumatoid arthritis (RA), osteoporosis is frequent, and in patients with postmenopausal RA, the degree of bone loss is dramatically increased. Hormone replacement therapy (HRT) in murine and human arthritis has beneficial effects on bone loss, as expected, but it also ameliorates inflammation and inflammation-triggered joint destruction. Long-term use of HRT has been associated with increased risk of breast cancer, thrombosis, and possibly also stroke. Accordingly, there is great need for new activators of estrogen receptors (ERs) selectively reproducing only the beneficial effects of estrogen. To achieve this aim, better knowledge of the mechanisms of how activation of ER-alpha and ER-beta modulates the immune system and bone at the cellular and molecular levels is necessary.