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PubMed2004

Daidzein together with high calcium preserve bone mass and biomechanical strength at multiple sites in ovariectomized mice.

As the prevalence of osteoporosis is increasing, and the adverse effects of hormone replacement therapy are evident, women are searching for natural alternatives such as soy isoflavones to help prevent postmenopausal osteoporosis. Daidzein is one of the most abundant isoflavones present in soy and it is unique as it can be further metabolized to equol, a compound with greater estrogenic activity than other isoflavones. The objective of this study was to determine the effects of purified daidzein in combination with high calcium (Ca) on preserving femur and lumbar vertebrae (LV1-LV4) bone mineral density (BMD) and biomechanical bone strength at three different sites (femur midpoint, femur neck and LV3) in ovariectomized mice. Sham (SH) mice (n = 12) received control diet (AIN93G) containing 2 g Ca/kg diet and ovariectomized mice were randomized to 1 of 6 groups (n = 12/group): OVX (2 g Ca/kg diet), HCa (25 g Ca/kg diet), HD (2 g Ca + 200 mg daidzein/kg diet), HDCa (25 g Ca + 200 mg daidzein/kg diet), LD (2 g Ca + 100 mg daidzein/kg diet) or LDCa (25 g Ca + 100 mg daidzein/kg diet) for 12 weeks. HDCa preserved femur and vertebrae BMD and biomechanical bone strength (at all three sites) compared to the OVX group, however, only femur yield load (at midpoint) was preserved to a level that was greater (P < 0.05) than HCa alone. Mice fed HD diet had greater (P < 0.05) femur BMD than OVX group, however, daidzein alone (HD) did not appear to preserve trabecular bone (i.e., vertebrae BMD and vertebra peak load). All mice fed daidzein produced equol and there were no uterotrophic effects of daidzein at either dose. Both daidzein and Ca attenuated the increase in serum IL-1beta observed in the OVX group. The results from this study suggest that the combination of daidzein and high Ca favorably affect cortical and trabecular bone as indicated by femur and lumbar vertebrae BMD and biomechanical strength but much of this effect is mediated by the high Ca diet. Further investigation is required to determine optimal dietary levels of daidzein and Ca with the long-term goal of developing a dietary strategy to prevent postmenopausal osteoporosis and related fragility fractures.

Animals↗
PubMed2006

Concentrations of isoflavones in plasma and urine of post-menopausal women chronically ingesting high quantities of soy isoflavones.

Soy food or food supplements based on soy containing isoflavones (Isos) are increasingly available in Western countries. However, the variability of Isos levels in urine and plasma in humans during chronic ingestion is poorly documented. Nevertheless, this is the way these compounds will most probably be used in the future, especially if the soy-based supplements market goes on increasing. Here, glycosilated Isos in an enriched extract of Prevastein equal to 100 mg of equivalent Isos aglycone was given daily to 27 post-menopausal women for 30 days and to 12 post-menopausal women for 60 days. Volunteers were given Prevastein in a cereal bar (25 mg Isos) and in a yoghurt (25 mg Isos) both at breakfast and dinner. Plasma samples were collected after overnight fasting. Urine samples were aliquots of a 24 h collection checked on volume and creatinin excretion levels. Genistein, daidzein and equol were measured at day 0 and every 15 days afterwards, using original specific ELISAs. Constant levels were reached from the 15th day. About 59.2% of the volunteers were significant equol producers in the first experiment and 58.3% in the second. A large variability in plasma and urine levels was observed among post-menopausal women consuming 100 mg Isos per day, although remaining relatively stable in each individual subject. This could partly account for the controversial effects of Isos recorded so far in clinical studies. So Isos plasma levels would have to be assayed during chronic exposures, and could help to better understand the large variability of the effects classically observed in clinical studies. ELISA techniques could be easily exported to analytical laboratories to help physicians and nutritionists with their prescriptions.

Aged↗
PubMed2005

Comparative study of oestrogenic properties of eight phytoestrogens in MCF7 human breast cancer cells.

Previous studies have compared the oestrogenic properties of phytoestrogens in a wide variety of disparate assays. Since not all phytoestrogens have been tested in each assay, this makes inter-study comparisons and ranking oestrogenic potency difficult. In this report, we have compared the oestrogen agonist and antagonist activity of eight phytoestrogens (genistein, daidzein, equol, miroestrol, deoxymiroestrol, 8-prenylnaringenin, coumestrol and resveratrol) in a range of assays all based within the same receptor and cellular context of the MCF7 human breast cancer cell line. The relative binding of each phytoestrogen to oestrogen receptor (ER) of MCF7 cytosol was calculated from the molar excess needed for 50% inhibition of 3H]oestradiol binding (IC50), and was in the order coumestrol (35x)/8-prenylnaringenin (45x)/deoxymiroestrol (50x)>miroestrol (260x)>genistein (1000x)>equol (4000x)>daidzein (not achieved: 40% inhibition at 10(4)-fold molar excess)>resveratrol (not achieved: 10% inhibition at 10(5)-fold molar excess). For cell-based assays, the rank order of potency (estimated in terms of the concentration needed to achieve a response equivalent to 50% of that found with 17beta-oestradiol (IC50)) remained very similar for all the assays whether measuring ligand ability to induce a stably transfected oestrogen-responsive ERE-CAT reporter gene, cell growth in terms of proliferation rate after 7 days or cell growth in terms of saturation density after 14 days. The IC50 values for these three assays in order were for 17beta-oestradiol (1 x 10(-11)M, 1 x 10(-11)M, 2 x 10(-11)M), and in rank order of potency for the phytoestrogens, deoxymiroestrol (1 x 10(-10)M, 3 x 10(-11)M, 2 x 10(-11)M)>miroestrol (3 x 10(-10)M, 2 x 10(-10)M, 8 x 10(-11)M)>8-prenylnaringenin (1 x 10(-9)M, 3 x 10(-10)M, 3 x 10(-10)M)>coumestrol (3 x 10(-8)M, 2 x 10(-8)M, 3 x 10(-8)M)>genistein (4 x 10(-8)M, 2 x 10(-8)M, 1 x 10(-8)M)/equol (1 x 10(-7)M, 3 x 10(-8)M, 2 x 10(-8)M)>daidzein (3 x 10(-7)M, 2 x 10(-7)M, 4 x 10(-8)M)>resveratrol (4 x 10(-6)M, not achieved, not achieved). Despite using the same receptor context of the MCF7 cells, this rank order differed from that determined from receptor binding. The most marked difference was for coumestrol and 8-prenylnaringenin which both displayed a relatively potent ability to displace [3H]oestradiol from cytosolic ER compared with their much lower activity in the cell-based assays. Albeit at varying concentrations, seven of the eight phytoestrogens (all except resveratrol) gave similar maximal responses to that given by 17beta-oestradiol in cell-based assays which makes them full oestrogen agonists. We found no evidence for any oestrogen antagonist action of any of these phytoestrogens at concentrations of up to 10(-6)M on either reporter gene induction or on stimulation of cell growth.

Biological Assay↗
PubMed2005

Phytoestrogen metabolites are much more active than phytoestrogens themselves in increasing prostaglandin F(2alpha) synthesis via prostaglanin F(2alpha) synthase-like 2 stimulation in bovine endometrium.

Phytoestrogens have recently been suggested to be the cause of infertility by stimulating luteolytic prostaglandin (PG) F(2alpha) secretion from endometrium in cattle. The purpose of this study was to examine the enzymatic and molecular mechanisms involved in the preferential induction of PGF(2alpha) synthesis by phytoestrogens, and whether phytoestrogens influence endometrial cell viability. Cultured bovine endometrial epithelial and stromal cells were exposed to phytoestrogens (daidzein and genistein) and their metabolites (equol and p-ethyl phenol) for 24h. Prostaglandin F(2alpha) and PGE2 were stimulated by phytoestrogens in both stromal and epithelial cells, with a preference for PGF(2alpha) synthesis in epithelial cells (P<0.001). Although RT-PCR and Western Blot analyses did not reveal the influence of phytoestrogens on either gene expression or protein level of cyclooxygenase-2 (COX-2) and PGE2 synthase (PGES) in stromal and epithelial cells (P>0.05), the stimulative effects of equol and p-ethyl phenol on PGF(2alpha) synthase-like 2 (PGFSL2) gene expression and protein level were observed only in epithelial cells (P<0.05). The same compounds did not affect PGFSL2 gene expression and protein in stromal cells (P>0.05). Exposure to phytoestrogens and their metabolites decreased cell viability in both stromal and epithelial cells. Stromal cell viability decreased to 50% of the control and was more evident than that in epithelial cells (P<0.001). The overall results suggest that infertility in cattle, caused by phytoestrogen-dependent preferential stimulation of luteolytic PGF(2alpha) synthesis, is caused by increasing PGFSL2 in epithelial cells, and by decreasing stromal cell viability, which are the main source of luteotropic PGE2 production.

Animals↗
PubMed2002

Binding affinities of hepatic nuclear estrogen receptors for phytoestrogens in rainbow trout (Oncorhynchus mykiss) and Siberian sturgeon (Acipenser baeri).

Phytoestrogens are dietary estrogenic contaminants capable of inducing vitellogenin synthesis in rainbow trout and Siberian sturgeon. A competitive-binding assay on their hepatic estrogen receptors (ER) was performed to determine the relative affinity of phytoestrogens compared to estradiol (E(2)). Phytoestrogen concentrations used were 1000 times higher than for E(2), except for genistein and formononetin. For each compound, the competition with 50%-bound labelled E(2) (DC(50)) was considered in order to classify phytoestrogens according to their affinity for ER. The affinities are compared for each species. In rainbow trout, estradiol (DC(50): 7 nM)>formononetin (DC(50): 260 nM)>genistein (DC(50): 570 nM)>equol (DC(50): 5.3 microM)>daidzein (DC(50): 9 microM)>biochanin A (DC(50): 100 microM). In sturgeon, estradiol (DC(50): 5 nM)>genistein (DC(50): 220)>formononetin (DC(50): 1 microM)>equol>(DC(50): 8.3 microM)>daidzein>(DC(50): 80 microM)>biochanin A (DC(50): 100 microM). These results demonstrate that phytoestrogens, mimicking estradiol, can disturb the endocrine system by competing for ER. Also, the higher sensitivity to genistein observed in vivo in Siberian sturgeon (vitellogenin synthesis), compared to rainbow trout, is not due to a higher affinity of genistein for the hepatic ER. Thus, the metabolism of phytoestrogen could be species dependent and affect sensitivity.

Animals↗
PubMed2004

Inulin effects on bioavailability of soy isoflavones and their calcium absorption enhancing ability.

The effect of inulin on isoflavone absorption and the effect of isoflavones and synergy with inulin on calcium absorption in rats was investigated. Rats (n = 48) were divided into three groups and fed inulin (50 mg/g), isoflavone (8 mg/g) or inulin + isoflavone (50 mg/g + 8 mg/g) diets for 21 days. After a 2-h fast, rats were given (45)Ca orally or intraperitoneally, together with 25 mg of calcium as calcium acetate. Blood and femurs were collected 4 days later. Sera were analyzed for isoflavones using HPLC-MS, femurs for (45)Ca by beta-scintillation counting, and total femoral calcium by atomic absorption spectroscopy. Both groups fed isoflavones had similar and significantly higher weight-adjusted total femoral calcium content compared to the inulin-fed group (p < 0.0001). (45)Ca absorption was significantly higher (p < 0.01) when isoflavones were added to the diet, and serum equol was significantly lower (p < 0.01) when inulin was added to the diet containing isoflavones. We conclude that isoflavones enhance calcium absorption, without synergy from inulin, and that inulin decreases equol production.

Absorption↗
PubMed1995

Metabolites of daidzein and genistein and their biological activities.

A number of metabolites of daidzein and genestein have been synthesized and their biological activities determined. Equol [3], 5,7,4'-trihydroxyisoflavan [5], 4,7,4'-trihydroxyisoflavan [6], dihydrodaidzein [8], and dihydrogenistein [9] were synthesized either from daidzein [1] or genistein [2] by hydrogenation. Similarly, the derivatives 4, 7, and 11 were synthesized from 3, 6, and 10, respectively. During acetylation and nmr experiments, 9 was converted to a novel enol intermediate [10]. Antifungal, antibacterial, mosquitocidal, nematocidal, and topoisomerase inhibition activities of these compounds were evaluated, with equol [3] being the most active of the compounds tested against topoisomerase I.

Acetylation↗
PubMed2001

The vascular activity of some isoflavone metabolites: implications for a cardioprotective role.

Legume-derived isoflavones such as genistein, diadzein and equol have been associated with a reduction in risk of cardiovascular disease. In the current study, we explore the vascular activity of several isoflavone metabolites namely dihydrodaidzein, cis and trans-tetrahydrodaidzein and dehydroequol for potential cardioprotective properties. Rat isolated aortic rings were used. 17beta-oestradiol, equol, and all four of the metabolites studied significantly antagonized contractile responses to noradrenaline. The direct vasodilatory action of these compounds were examined and in contrast to 17beta-oestradiol, the vasodilatory effect of which was demonstrated to be endothelium independent, the dilatory action of all four compounds could be inhibited by endothelium denudation. Further, the dilatory action of both dihydrodaidzein and cis-tetrahydrodaidzein were inhibited by the nitric oxide synthase inhibitor, N(omega)-nitro-L-arginine (NOLA), by the soluble guanylate cyclase inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) and by 40 mM KCl. Dilatory responses to dehydroequol and trans-tetrahydrodaidzein, on the other hand, were inhibited by 40 mM KCL but not by NOLA nor ODQ. Finally, we examined the protective potential of these compounds in inhibiting endothelium damage by oxidized low density lipoprotein (ox-LDL). Trans-tetrahydrodaidzein was at least 10 fold more potent than 17beta-oestradiol in protecting against ox-LDL induced damage. We conclude that the isoflavone metabolites, dihydrodaidzein, cis- and trans-tetrahydrodaidzein and dehydroequol, may potentially represent a novel series of cardioprotective therapeutics.

Animals↗
PubMed2003

Bioavailability of phyto-oestrogens.

The term phyto-oestrogen encompasses isoflavone compounds, such as genistein and daidzein, found predominantly in soya products and the lignans, such as matairesinol and secoisolariciresinol, found in many fruits, cereals and in flaxseed. There is evidence that they have potential health benefits in man particularly against hormone-dependent diseases such as breast and prostate cancers and osteoporosis. This has led to intense interest in their absorption and biotransformation in man. The metabolism of isoflavones and lignans in animals and man is complex and involves both mammalian and gut microbial processes. Isoflavones are present predominantly as glucosides in most commercially available soya products; there is evidence that they are not absorbed in this form and that their bioavailability requires initial hydrolysis of the sugar moiety by intestinal beta-glucosidases. After absorption, phyto-oestrogens are reconjugated predominantly to glucuronic acid and to a lesser degree to sulphuric acid. Only a small portion of the free aglycone has been detected in blood, demonstrating that the rate of conjugation is high. There is extensive further metabolism of isoflavones (to equol and O-desmethylangolensin) and lignans (to enterodiol and enterolactone) by gut bacteria. In human subjects, even those on controlled diets, there is large interindividual variation in the metabolism of isoflavones and lignans, particularly in the production of the gut bacterial metabolite equol (from daidzein). Factors influencing absorption and metabolism of phyto-oestrogens include diet and gut microflora.

Adult↗
PubMed2005

Effect of consumption of soy isoflavones on behavioural, somatic and affective symptoms in women with premenstrual syndrome.

Up to 80 % of the Western female population experience premenstrual syndrome (PMS). Long-term pharmacological therapy is unacceptable to most women, and is not warranted for moderate symptoms. Nutritional therapies are popular, but lack a clear evidence base. Anecdotal evidence suggests beneficial effects of soy isoflavones because of their influence on endogenous oestrogen and actions on specific tissues. The effect of isolated soya protein (ISP) containing 68 mg/d (aglycone equivalents) soy isoflavones (IF) on premenstrual symptom severity was studied in a seven-menstrual cycle, double-blind, placebo-controlled, crossover intervention study in twenty-three women with prospectively confirmed PMS aged 18-35 years and BMI 19-30 kg/m(2). ISP containing IF or milk protein placebo was consumed for two complete menstrual cycles. ISP containing IF (genistein, daidzein, equol) were measured in 24 h urine samples. After two cycles of ISP containing IF intervention, total symptoms (F(2,36) 8.20, P=0.000) and physical symptoms (F(2,36) 8.18, P=0.000) were significantly reduced compared with baseline after both active and placebo treatments, although differences between active and placebo treatment were non-significant. Specific premenstrual symptoms, headache (F(2,32) 4.10, P=0.026) and breast tenderness (F(2,32) 4.59, P=0.018), were reduced from baseline after soy IF, but not milk protein placebo. Cramps (F(2,32) 4.15, P=0.025) and swelling (F(2,32) 4.64, P=0.017) were significantly lower after active treatment compared with placebo. Concentrations of genistein and daidzein were increased following soy IF consumption, but equol production did not enhance symptom reduction. The present study showed that ISP containing IF may have potential to reduce specific premenstrual symptoms via non-classical actions.

Adolescent↗
PubMed2004

Growth performance, carcass characteristics and bioavailability of isoflavones in pigs fed soy bean based diets.

A growth trial with 38 weaners (castrated male pigs) was designed to compare the growth performance and carcass quality of pigs fed diets containing either soy bean meal or soy protein concentrate in a pair-feeding design. Soy bean meal (SBM) and soy protein concentrate (SPC) differed in isoflavone (daidzein plus genistein) content (782 microg/g in SBM and 125 microg/g in SPC, respectively). During the experiment, all pigs were fed four-phases-diets characterized by decreasing protein concentrations with increasing age (weaner I, weaner II, grower, finisher diets). Rations of control and experimental groups were isoenergetic, isonitrogenous, and isoaminogen. The weanling pigs with an initial live weight of 8.4 +/- 1.1 kg were allotted to flat deck boxes. During the growing/finishing period (days 70-170 of age), the pigs were housed in single boxes. Both, the weaning and the grower/finishing performances (daily body weight gain, feed intake, feed conversion ratio) were similar in both groups. No differences were found between the groups in carcass composition (percentages of cuts, tissues, and protein/fat), and meat quality of pigs. Moreover, the IGF-1R mRNA expression in longissimus muscle was not influenced by the kind of soy product. However, circulating levels of isoflavones were clearly different between pigs fed SBM (genistein 239 +/- 44; daidzein 162 +/- 42; equol 12 +/- 4 ng/ml plasma) and animals fed SPC (genistein 22 +/- 9 and daidzein 8 +/- 3, and equol 10 +/- 3 ng/ml plasma). The results confirm the expected differences in the bioavailability of soy isoflavones, yet, there were no significant differences in performance of pigs fed either soy bean meal or soy protein concentrate.

Animal Feed↗
PubMed2003

Antioxidant and free radical scavenging activity of isoflavone metabolites.

1. Soy isoflavones have been extensively studied because of their possible health-promoting effects. Genistein and daidzein, the major isoflavone aglycones, have received most attention; however, they undergo extensive metabolism in the gut and liver, which might affect their biological properties. 2. The antioxidant activity, free radical-scavenging properties and selected cellular effects of the isoflavone metabolites equol, 8-hydroxydaidzein, O-desmethylangiolensin, and 1,3,5 trihydroxybenzene were investigated in comparison with their parent aglycones, genistein and daidzein. 3. Electron spin resonance spectroscopy indicated that 8-hydroxydaidzein was the most potent scavenger of hydroxyl and superoxide anion radicals. Isoflavone metabolites also exhibited higher antioxidant activity than parent compounds in standard antioxidant (FRAP and TEAC) assays. However, for the suppression of nitric oxide production by activated macrophages, genistein showed the highest potency, followed by equol and daidzein. 4. The metabolism of isoflavones affects their free radical scavenging and antioxidant properties, and their cellular activity, but the effects are complex.

Animals↗
PubMed1998

Effect of soy-derived isoflavonoids on the induced growth of MCF-7 cells by estrogenic environmental chemicals.

Isoflavonoids are natural plant compounds and possess antitumorigenic properties. Many environmental chemicals have been found to be estrogenic and can enhance tumor growth in estrogen receptor-positive cells. In the present study, the effects of genistein, daidzein, biochanin A, formononetin, and equol on the proliferation of estrogen receptor-positive MCF-7 cells induced by synthetic chemicals 1-(o-chlorophenyl)-1-(p-chlorophenyl)-2,2,2-trichloroethane (o,p'-DDT), 4-nonylphenol (4-NP), and 5-octylphenol (5-OP) found in the environment were investigated. Genistein, biochanin A, equol, and to some extent daidzein, but not formononetin, at < 10 microM can enhance the growth of MCF-7 cells in the absence of environmental chemicals. Formononetin was toxic to MCF-7 cells at the tested concentrations. The environmental chemicals 4-NP, 5-OP, and o,p'-DDT and the natural estrogen 17 beta-estradiol at 5, 5, and 10 microM and 5 nM, respectively, induced proliferation of MCF-7 cells. In the presence of isoflavonoids (> 25 microM), the environmental chemical-induced cell proliferation was inhibited. Individually, genistein (IC50 = 25-33 microM) was the most potent inhibitor against the induced proliferation of MCF-7 cells of the isoflavonoids needed for a 50% suppression of growth induced by 4-NP, 5-OP, and o,p'-DDT. A mixture of isoflavonoids was the most potent inhibitor against the induced proliferation. Estrogen receptor-dependent and -independent pathways could be involved in the inhibitory actions of isoflavonids. Because it is impossible to have a chemical-free environment, the in vitro data presented here are of practical importance to develop evolving dietary strategies and tactics against the adverse health effects of environmental chemicals.

Alkanes↗
PubMed2006

Effect of a nutritional supplementation on bone health in Chilean elderly subjects with femoral osteoporosis.

OBJECTIVE: To study the effects of a special nutritional supplement on bone mineral density and bone turnover markers in Chilean elderly subjects with femoral osteoporosis. SETTING: Public primary health care clinics in Chile. SUBJECTS: Free living elderly subjects with femoral osteoporosis. INTERVENTIONS: Subjects were randomized to receive the usual nutritional supplement provided by the Chilean Ministry of Health or a special nutritional supplement providing, among other nutrients, 90 mg isoflavones, 800 mg calcium, 400 IU vitamin D, 60 ug vitamin K and 31 g proteins per day. MEASURES OF OUTCOME: At baseline, and after six and twelve months of supplementation, body composition, bone mineral density, serum 25 OH vitamin D, intact parathyroid hormone (iPTH), osteocalcin, decarboxylated osteocalcin, urinary aminoterminal telopeptide of type I collagen (NTX), deoxypyridoline cross links (Dpd) and equol were measured. Every month, urinary daidzein was measured in a morning urine sample. RESULTS: No differences between treatment groups were observed in body composition or bone mineral density changes. The group receiving the special supplement had a significant increase in serum 25 OH vitamin D and a significant decrease in serum iPTH and decarboxylated osteocalcin. No association between daidzein or equol excretion and changes in bone mineralization was observed. CONCLUSIONS: A special supplement delivered to elderly subjects with osteoporosis improved serum vitamin D and reduced serum iPTH and undercarboxylated osteocalcin levels but did not affect BMD.

Aged↗
PubMed2004

Effect of circulating forms of soy isoflavones on the oxidation of low density lipoprotein.

Soy isoflavones are thought to have a cardioprotective effect that is partly mediated by an inhibitory influence on the oxidation of low density lipoprotein (LDL). However, the aglycone forms investigated in many previous studies do not circulate in appreciable quantities because they are metabolised in the gut and liver. We investigated effects of various isoflavone metabolites, including for the first time the sulphated conjugates formed in the liver and the mucosa of the small intestine, on copper-induced LDL oxidation. The parent aglycones inhibited oxidation, although only 5% as well as quercetin. Metabolism increased or decreased their effectiveness. Equol inhibited 2.65-fold better than its parent compound daidzein and 8-hydroxydaidzein, not previously assessed, was 12.5-fold better than daidzein. However, monosulphated conjugates of genistein, daidzein and equol were much less effective and disulphates completely ineffective. Since almost all isoflavones circulate as conjugates, these data suggest that despite the increased potency produced by some metabolic changes, isoflavones may not be effective antioxidants in vivo unless they are deconjugated again.

Adult↗
PubMed2000

Isoflavone phytoestrogens consumed in soy decrease F(2)-isoprostane concentrations and increase resistance of low-density lipoprotein to oxidation in humans.

BACKGROUND: Oxidative damage to lipids may be involved in the etiology of atherosclerosis, cardiovascular disease in general, and cancer. The soy isoflavone phytoestrogens, genistein and daidzein, and equol (a daidzein metabolite produced by intestinal microflora) are antioxidants in vitro; equol is a particularly good inhibitor of LDL oxidation and membrane lipid peroxidation. OBJECTIVE: We sought to investigate the effects of a diet enriched with soy containing isoflavones on in vivo biomarkers of lipid peroxidation and resistance of LDL to oxidation, compared with a diet enriched with soy from which the isoflavones had been extracted. DESIGN: : A randomized, crossover design was used to compare diets enriched with soy that was low or high in isoflavones in 24 subjects. Plasma concentrations of an F(2)-isoprostane, 8-epi-prostaglandin F(2)(alpha) (8-epi-PGF(2)(alpha)), a biomarker of in vivo lipid peroxidation, and resistance of LDL to copper-ion-induced oxidation were determined. RESULTS: Plasma concentrations of 8-epi-PGF(2)(alpha) were significantly lower after the high-isoflavone dietary treatment than after the low-isoflavone dietary treatment (326 +/- 32 and 405 +/- 50 ng/L, respectively; P = 0.028) and the lag time for copper-ion-induced LDL oxidation was longer (48 +/- 2.4 and 44 +/- 1.9 min, respectively; P = 0.017). Lag time for oxidation of unfractionated plasma and plasma concentrations of malondialdehyde, LDL alpha-tocopherol, polyunsaturated fatty acids, and isoflavonoids did not differ significantly between dietary treatments. CONCLUSIONS: Consumption of soy containing naturally occurring amounts of isoflavone phytoestrogens reduced lipid peroxidation in vivo and increased the resistance of LDL to oxidation. This antioxidant action may be significant with regard to risk of atherosclerosis, cardiovascular disease in general, and cancer.

Adult↗
PubMed2004

Behavioral effects of endocrine-disrupting substances: phytoestrogens.

A major source of endocrine-disrupting substances, usually not considered in laboratory animal experiments, is the diet used in research investigations. Soy represents the main protein source in almost all natural-ingredient commercially available formulated diets. Soy-derived isoflavones are the most abundant and in many ways the most studied phytoestrogens, and phytoestrogens (isoflavones) are known endocrine disruptors. Research is reviewed that identifies the physiological and behavioral endocrine-disrupting effects of dietary phytoestrogens (isoflavones) in animal diets, including most of the isoflavones, which are in a glycoside form and biologically inactive, and those in the gastrointestinal tract, which are biologically active. The isoflavones genistein and daidzein have similar molecular weights and structural characteristics to that of 17-beta estradiol, which may enable them to exert estrogenic and antiestrogenic properties are described and characterized. Daidzein can be further metabolized to the potent and abundant molecule equol, which in rodents is produced in very large amounts and represents the major circulating metabolite among all biologically active isoflavones. Equol has the unique and important ability to specifically bind 5 alpha-dihydro-testosterone, and to act in turn to inhibit the action of this potent androgen. The specific influence of dietary soy phytoestrogens on consumptive, learning and memory, and anxiety-related behaviors is identified. Regulatory behaviors such as food and water intake, adipose deposition and leptin, and insulin levels affected by dietary isoflavones are also discussed.

Animal Nutritional Physiological Phenomena↗
PubMed2002

Is daidzein non-metabolizer a high risk for prostate cancer? A case-controlled study of serum soybean isoflavone concentration.

BACKGROUND: It has been postulated that soybean isoflavones act as inhibitory factors in prostate cancer. However, to date there have been no case-controlled clinical studies carried out to compare the circulating concentrations of isoflavones in prostate cancer patients and control subjects. METHODS: The serum levels of genistein, daidzein and equol were determined and compared in 253 experimental subjects (141 prostate cancer patients and 112 cancer-free controls). RESULTS: The serum concentrations of isoflavones were compared in hospitalized and non-hospitalized subjects and for both the prostate cancer patients and the controls the concentrations were lower in the hospitalized subjects. The serum concentrations of genistein and daidzein were compared in subjects <70 years of age and subjects >/=70 years old and the levels were significantly lower in the younger group. Contrary to our expectation, comparison of the patient group and the control group revealed the serum concentrations of isoflavones to be higher in the patient group. Daidzein non-metabolizers were compared in the hospitalized experimental subjects of the patient group and the control group and they were significantly more common in the patient group. The poorly differentiated cancer patient group included a significantly lower percentage of daidzein metabolizers. CONCLUSIONS: The above findings revealed that equol itself or some unknown factor regulating the metabolism of daidzein is deeply involved in the biology of prostate cancer. Future studies are urgently needed to compare the incidence of daidzein metabolizers among various countries.

Aged↗