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PubMed1989

Variations in catechol O-methyltransferase activity in rodent tissues: possible role in estrogen carcinogenicity.

Catechol-O-methyltransferase (COMT) [EC 2.1.1.6] is a ubiquitous cytosolic enzyme which has a pertinent role in the inactivation of both natural and synthetic catechol estrogens in mammalian tissues. We have compared the COMT activity in mouse, hamster and rat kidney, liver and red blood cells and examined the kinetic characteristics of this enzyme in the latter two species using various catechol estrogens as substrates. Results presented here indicate that the ratios of COMT activity in the kidney versus the liver of the rat and mouse are nearly identical, 0.48-0.52, whereas there is a 29-fold ratio between the level of COMT activity in these two tissues in the hamster. In red blood cells, the level of COMT activity is 4- and 12-fold lower in the hamster compared to mouse and rat, respectively. When the kinetic characteristics of this enzyme were assessed in the hamster and rat kidney and liver, except for 2-hydroxymoxestrol which had an apparent Km value of 15-48 microM, the other catechol estrogen substrates exhibited Km values ranging from 1-10 microM. Generally, the Vmax values were markedly higher in the rat kidney and liver than those observed in corresponding hamster tissues. The significantly lower COMT activity in the hamster liver and red blood cells suggests that under chronic estrogen treatment at high doses, the concentration of catechol estrogens in these tissues may exceed the capacity of COMT to effectively catalyse their O-methylation into inactive metabolites. The resulting accumulation of catechol estrogens may contribute to the estrogen carcinogenicity observed in the hamster liver and kidney. Additionally, when 2-hydroxyestrone was used as a substrate, the estrogen-induced renal carcinoma exhibited only 8.6% of the COMT activity found in the normal kidney.

Animals↗
PubMed1997

Formation of catechol estrogen glutathione conjugates and gamma-glutamyl transpeptidase-dependent nephrotoxicity of 17beta-estradiol in the golden Syrian hamster.

In an animal model of hormone-mediated carcinogenesis, male golden Syrian hamsters develop renal carcinoma following prolonged exposure to 17beta-estradiol. The basis for the species and tissue specificity is unclear. Detailed information on the disposition of 17beta-estradiol in this model is lacking. Because catechol estrogens have been implicated in this model of carcinogenesis, we investigated the metabolism and nephrotoxicity of 17beta-estradiol in golden Syrian hamsters, with emphasis on the formation of catechol estrogen thioethers. 17beta-Estradiol (50 micromol/kg, i.p.) is a mild nephrotoxicant, causing significant elevations in the urinary excretion of gamma-glutamyl transpeptidase (gamma-GT), alkaline phosphatase, glutathione S-transferase (GST) and glucose. Increases in renal protein carbonyls and lipid hydroperoxides, which are markers of oxidative damage, also occur after administration of 17beta-estradiol (50 micromol/kg, i.p.). 17beta-Estradiol-mediated nephrotoxicity is reduced by treating animals with acivicin, an inhibitor of gamma-GT, implying that toxicity is mediated by metabolites requiring metabolism by this enzyme. Following administration of 17beta-[14C]estradiol (100 micromol/kg) to hamsters, 9.7% of the dose is recovered in bile after 5 h, the majority (7.9%) representing aqueous metabolites. Seven catechol estrogen GSH conjugates were identified, 2-hydroxy-1,4-bis-(glutathion-S-yl)-17beta-estradiol, 2-hydroxy-4-(glutathion-S-yl)-17beta-estradiol, 2-hydroxy-4-(glutathion-S-yl)-estrone, 4-hydroxy-1-(glutathion-S-yl)-estrone, 2-hydroxy-1-(glutathion-S-yl)-estrone, 4-hydroxy-1-(glutathion-S-yl)-17beta-estradiol, and 2-hydroxy-1-(glutathion-S-yl)-17beta-estradiol. At 5.4 micromol/kg of 17beta-estradiol, a dose-reflective of daily exposure levels in the hamster model of nephrocarcinogenicity, 12% of the dose is recovered within 5 h as a combination of GSH conjugates of 2- and 4-hydroxy-17beta-estradiol and 2- and 4-hydroxyestrone. In summary, oxidation of catechol estrogens, followed by GSH conjugation, occurs in vivo and 17beta-estradiol is a mild nephrotoxicant in a manner dependent on the activity of gamma-GT.

Alkaline Phosphatase↗
PubMed2002

Catechol estrogen formation in liver microsomes from female ACI and Sprague-Dawley rats: comparison of 2- and 4-hydroxylation revisited.

Estradiol (E(2))-hydroxylation was studied in liver microsomes from ACI and Sprague-Dawley female rats, which differ markedly in their susceptibility to E(2)-induced formation of mammary tumors. NADPH-dependent oxidation of E(2) by liver microsomes from ACI and Sprague-Dawley rats produced several metabolites of which 2-hydroxyestradiol (2-OH-E(2)), estrone (E(1)), and 2-hydroxyestrone (2-OH-E(1)) were predominant. Incubations with either low (9 nM) or high (50 microM) concentrations of radiolabeled E(2) and with varying amounts of microsomal protein indicated the formation of only small amounts of 4-hydroxyestradiol (4-OH-E(2)). The ratio of 2-OH-E(2) to 4-OH-E(2) formed with the low concentration of E(2) was about 10:1 regardless of the amount of microsomal protein used, and about 20:1 using a high concentration of E(2). Thus, oxidation of E(2) by liver microsomes from female ACI and Sprague-Dawley rats occurs primarily via 2-hydroxylation, and 4-hydroxylation is only a minor pathway. These results are in disagreement with a recent report indicating substantial 4-hydroxylation of E(2) by liver microsomes from female ACI rats.

Animals↗
PubMed2003

Lifespan is prolonged in autoimmune-prone (NZB/NZW) F1 mice fed a diet supplemented with indole-3-carbinol.

Dietary modulation has the potential to prevent or ameliorate systemic lupus erythematosus (SLE). Indole-3-carbinol (I3C), which is abundant in cruciferous vegetables, was evaluated in a murine model of SLE because of its antiestrogenic activities. Female (NZB x NZW) F1 mice, which develop SLE, were fed an AIN76A diet without or with 0.2 g/kg I3C, starting soon after weaning or at 5 mo of age. At 12 mo of age, 80% of mice fed the I3C-supplemented diet soon after weaning were alive compared with only 10% of controls. When experimental diets were initiated at 5 mo of age, 100% of I3C fed mice and 30% of controls were alive at 12 mo of age. Anti-double-stranded DNA (dsDNA) antibodies developed in all groups, although at several time points, the levels produced in I3C-fed mice were significantly lower. Renal disease (proteinuria, histologic changes, IgG immune complex deposition, subepithelial deposits and diffuse epithelial cell foot process effacement) was more severe in controls with both protocols. The estrogen urinary metabolite ratio of 2- to 16alpha-hydroxyestrone was increased in I3C-fed mice. These findings demonstrate a profound effect of dietary I3C in experimental SLE.

Animals↗
PubMed2006

Sesame ingestion affects sex hormones, antioxidant status, and blood lipids in postmenopausal women.

Sesame ingestion has been shown to improve blood lipids in humans and antioxidative ability in animals. Sesamin, a sesame lignan, was recently reported to be converted by intestinal microflora to enterolactone, a compound with estrogenic activity and also an enterometabolite of flaxseed lignans, which are known to be phytoestrogens. Whether sesame can be a source of phytoestrogens is unknown. This study was designed to investigate the effect of sesame ingestion on blood sex hormones, lipids, tocopherol, and ex vivo LDL oxidation in postmenopausal women. Twenty-six healthy subjects attended, and 24 completed, this randomized, placebo-controlled, crossover study. Half of them consumed 50 g sesame seed powder daily for 5 wk, followed by a 3-wk washout period, then a 5-wk 50-g rice powder placebo period. The other half received the 2 supplements in reverse order. After sesame treatment, plasma total cholesterol (TC), LDL-C, the ratio of LDL-C to HDL-C, thiobarbituric acid reactive substances in oxidized LDL, and serum dehydroepiandrosterone sulfate decreased significantly by 5, 10, 6, 23, and 18%, respectively. The ratio of alpha- and gamma-tocopherol to TC increased significantly by 18 and 73%, respectively. All of these variables differed significantly between the 2 treatments. Serum sex hormone-binding globulin and urinary 2-hydroxyestrone (n = 8) increased significantly by 15 and 72%, respectively, after sesame treatment, and these concentrations tended to differ (P = 0.065 and P = 0.090, respectively) from those after the placebo treatment. These results suggest that sesame ingestion benefits postmenopausal women by improving blood lipids, antioxidant status, and possibly sex hormone status.

Aged↗
PubMed1997

Changes in levels of urinary estrogen metabolites after oral indole-3-carbinol treatment in humans.

BACKGROUND: The oxidative metabolism of estrogens in humans is mediated primarily by cytochrome P450, many isoenzymes of which are inducible by dietary and pharmacologic agents. One major pathway, 2-hydroxylation, is induced by dietary indole-3-carbinol (I3C), which is present in cruciferous vegetables (e.g., cabbage and broccoli). PURPOSE: Because the pool of available estrogen substrates for all pathways is limited, we hypothesized that increased 2-hydroxylation of estrogens would lead to decreased activity in competing metabolic pathways. METHODS: Urine samples were collected from subjects before and after oral ingestion of I3C (6-7 mg/kg per day). In the first study, seven men received I3C for 1 week; in the second study, 10 women received I3C for 2 months. A profile of 13 estrogens was measured in each sample by gas chromatography-mass spectrometry. RESULTS: In both men and women, I3C significantly increased the urinary excretion of C-2 estrogens. The urinary concentrations of nearly all other estrogen metabolites, including levels of estradiol, estrone, estriol, and 16alpha-hydroxyestrone, were lower after I3C treatment. CONCLUSIONS: These findings support the hypothesis that I3C-induced estrogen 2-hydroxylation results in decreased concentrations of several metabolites known to activate the estrogen receptor. This effect may lower estrogenic stimulation in women. IMPLICATIONS: I3C may have chemopreventive activity against breast cancer in humans, although the long-term effects of higher catechol estrogen levels in women require further investigation.

Adult↗
PubMed2000

Estrogens as endogenous genotoxic agents--DNA adducts and mutations.

Estrogens induce tumors in laboratory animals and have been associated with breast and uterine cancers in humans. In relation to the role of estrogens in the induction of cancer, we examine formation of DNA adducts by reactive electrophilic estrogen metabolites, formation of reactive oxygen species by estrogens and the resulting indirect DNA damage by these oxidants, and, finally, genomic and gene mutations induced by estrogens. Quinone intermediates derived by oxidation of the catechol estrogens 4-hydroxyestradiol or 4-hydroxyestrone may react with purine bases of DNA to form depurinating adducts that generate highly mutagenic apurinic sites. In contrast, quinones of 2-hydroxylated estrogens produce less harmful, stable DNA adducts. The catechol estrogen metabolites may also generate potentially mutagenic oxygen radicals by metabolic redox cycling or other mechanisms. Several types of indirect DNA damage are caused by estrogen-induced oxidants, such as oxidized DNA bases, DNA strand breakage, and adduct formation by reactive aldehydes derived from lipid hydroperoxides. Estradiol and the synthetic estrogen diethylstilbestrol also induce numerical and structural chromosomal aberrations and several types of gene mutations in cells in culture and in vivo. In conclusion, estrogens, including the natural hormones estradiol and estrone, must be considered genotoxic carcinogens on the basis of the evidence outlined in this chapter.

Animals↗
PubMed1981

Interactions of catecholestrogens with cytoplasmic and nuclear estrogen receptors in rat pituitary gland and hypothalamus.

The affinity of a series of catecholestrogens for 7S cytoplasmic receptor proteins from hypothalamus and pituitary gland of ovariectomised rats was assessed in vitro by a competitive charcoal binding assay at 4 degrees C. The equilibrium dissociation constants (Ki) of catecholestrogens 4-hydroxyestradiol, 4-hydroxyethynylestradiol, 2-hydroxyestradiol, 2-hydroxyethynylestradiol, and 4-hydroxyestrone were of the same order (Ki: 0.3-0.6 nM) as those of estradiol and ethnylestradiol (Ki: 0.1 nM). Methylation of 2-hydroxyestradiol led to a substantial loss of binding affinity. Tritium-labelled receptor complexes were demonstrated in KCl extracts of purified nuclei from pituitary and hypothalamic tissue 1 h after intravenous injection of 0.1 mCi tritiated 2- or 4-hydroxyestradiol. These macromolecular complexes sedimented in the 5-6S region of 5-20% (w/v) sucrose gradients containing 0.4 M-KCl. Further evidence for the translocation of estrogen receptors by catecholestrogens into the nuclei of rat pituitary and hypothalamus was the increase in nuclear receptor concentrations, measured by exchange assay, 1 h after the intraperitoneal injection of 0.1 mg unlabelled catecholestrogen. Administration of 4-hydroxyestradiol and 4-hydroxyethynylestradiol increased nuclear receptor concentrations to the same maximal levels as those following application of the same dose of estradiol or ethynylestradiol, whereas the respective 2-hydroxylated compounds exhibited only 60-70% of the maximal translocating capacity. The in vivo translocating capacities of the various catecholestrogens tested at this dose correlated well with their binding affinities for cytosol receptors determined in vitro.

Animals↗
PubMed1986

16 alpha-hydroxylation of estradiol: a possible risk marker for breast cancer.

From these results we may conclude that estradiol 16 alpha-hydroxylation is highly correlated with tumor incidence, and that the reaction is partly regulated by MMTV and the rest by genetic influences. Elevated hydroxylation appears to be an autosomal dominant trait that is highly specific for estradiol. It is also pertinent that the product of the 16 alpha-hydroxyestrone reaction is a potent estrogen that is capable of binding covalently to amino acids and nucleotides, including the estrogen receptor molecule. The results obtained in these studies establish the usefulness of the mouse model for studying the interrelationship between enhanced 16-hydroxylation of estradiol and the incidence of mammary tumors.

Age Factors↗
PubMed1965

Radiolysis of estrone and estradiol.

Gamma irradiation of estrone and estradiol in 1 Naqueous sodium hydroxide results in the formation of 2-hydroxyestrone and 2-hydroxyestradiol, respectively. Estrolactone (16a-oxa-D-homoestrone) was not encountered.

Chemical Phenomena↗
PubMed1965

Microbiological aspects in the hydroxylation of estrogens by Fusarium moniliforme.

A strain of Fusarium moniliforme (IH4), isolated from soil, showed outstanding enzymatic abilities to hydroxylate a number of estrogens. Estrone and estradiol were transformed into the 15alpha-hydroxy derivatives, and estradiol 3-methyl ether was transformed into the corresponding 6beta-hydroxy derivative. Delta(6)-Estrone was not hydroxylated. The accumulation of 15alpha-hydroxyestrone was influenced by the nutritional conditions of the fungus. Maximal yield was obtained when the organism grew in Czapek solution supplemented with yeast extract, although good conversion was also found in a peptone-corn molasses medium. Substitution of NO(3)-N in Czapek medium with NH(4)-N, lactalbumin hydrolysate, Casitone, or Casamino Acids resulted in limited hydroxylation of estrone. A remarkable strain specificity was demonstrated in this conversion. Of 13 strains of F. moniliforme and Gibberella fujikuroi under investigation, only 2 strains (IH4 and ATCC 9851) accumulated substantial amounts of the 15alpha-hydroxylated product. However, marked quantitative variations were observed which are attributable to a different ability of the organisms to degrade the steroid nucleus. Biochemical instabilities were also found through the appearance of spontaneous variants lacking steroid-hydroxylating activity. Replacement culture studies revealed that 15alpha-hydroxylation of estrone was dependent on the supply of external phosphate; exogenous nitrogen or energy sources were not required. Most of the enzymatic activity was confined to the mycelia. Microconidia showed a very limited hydroxylating activity, even in the presence of supplements or energy sources.

Culture Media↗
PubMed1975

Evidence for 16alpha-hydroxylation of estrone 3-sulphate by guinea pig liver slices.

[6,7-3H,35S]Estrone 3-sulfate (E13S) of 3H/35S = 3.57 was incubated with female guinea pig liver slices. Small amounts of free steroid and estrone-3-glucuronide, each containing 3H, were found. In addition, E13S, 17beta-estradiol 3-sulfate, and a 'disulfate' fraction, with 3H/35S = 4.4, 4.3, and 4.7, respectively, were also isolated from the incubated tissue. The latter fraction was a major metabolite and about 45% of it consisted of 'disulfates' of 16alpha-hydroxyestrone and estriol, thus providing strong evidence for 16alpha-hydroxylation in guinea pig liver slices.

Animals↗
PubMed1978

Precursor role of 15alpha-hydroxyestradiol and 15alpha-hydroxyandrostenedione in the formation of estetrol.

Studies were designed to elucidate the origin of estetrol (15alpha-hydroxyestriol (estra-1,3,5(10)triene-3,15alpha,17beta-tetrol) or E4) during late human pregnancy. 3H-Labelled 15alpha-hydroxyestradiol (3,15alpha-dihydroxyestra-1,3,5(10)-trien-17-one or 15E2) and 14C-labelled 17beta-estradiol (estra-1,3,5(10)-triene-3,17beta-diol or E2) were infused into the fetus during transfusion in utero for erythroblastosis fetalis, and in another study the same substrates were injected intravenously into the maternal circulation. In a third study, 3H-labelled 15alpha-hydroxyandrostenedion (15alpha-hydroxyandrost-4-ene-3,17-dione or 15delta4) and 14C-labelled E2 were infused into the fetus. Maternal urine was collected for 5--6 days, and after Glusulase hydrolysis, the following metabolites were isolated: estriol (estra-1,3,5(10)-triene-3,16alpha,17beta-triol or E3) containing 14C only and 15alpha-hydroxyestrone (3,15alpha-dihydroxyestra-1,3,5(10)-trien-17-one or 15E1), 15E2, and E4, all containing both labels. From the isotope content of these metabolites, it was concluded that E4 was derived from both fetal E2 and 15delta4 and only partially via 15E2. When administered to the fetus E2 and 15delta4 contributed approximately equal amounts to urinary E4. The yield of 15alpha-hydroxylated estrogens from E2 injected into the mother was very low indicating the predominantly fetal origin of the 15alpha-hydroxylase. 15delta4 was a better precursor than E2 for urinary 15E2.

Androstenedione↗
PubMed2005

Association of genetic polymorphisms with serum estrogens measured multiple times during a 2-year period in premenopausal women.

There is evidence that circulating estrogens are associated with breast cancer risk. In this study of premenopausal women, we explored the association of polymorphisms in genes in the estrogen synthesis and metabolism pathways with serum and urinary levels of estrone (E1) and estradiol (E2) and with the urinary ratio of 2-hydroxyestrone (2-OHE1)/16alpha-hydroxyestrone (16alpha-OHE1). This analysis included 220 women, who were participants in a 2-year randomized soy intervention. Blood specimens were collected in the luteal phase of the menstrual cycle an average of 4.4 times over 2 years. Overnight urinary specimens were collected on the same cycle day, only at baseline. Levels of E1, E2, 2-OHE1, and 16alpha-OHE1 were measured by enzyme immunoassays. The DNA samples were analyzed by PCR/RFLP for the COMT Val158Met, CYP1A1*2A, CYP1A1*2B, CYP1A2*1F, CYP1B1 Val432Leu, and CYP17 T27C polymorphisms. We applied mixed models to investigate the relations between genotypes and repeated serum hormone measurements and generalized linear models to assess associations between genotypes and urinary estrogen metabolites. The CYP1A2 C allele was significantly associated with lower serum E2 levels; in CC genotype carriers, serum E2 levels were 26.3% lower than in homo- and heterozygous common allele carriers combined (P = 0.01). CYP1A2*1F also affected the urinary 2-OHE1/16alpha-OHE1 ratio; carriers of the variant C allele had a markedly lower ratio than individuals with the AA genotype (1.37 versus 1.76; P = 0.002). These data suggest that CYP1A2*1F is associated with lower circulating levels of E2, and that it may be a susceptibility locus for breast cancer.

Adult↗
PubMed1982

Differential effects of catechol estrogens, progestins and CI-628 administered by constant infusion on the central and peripheral action of estradiol.

By means of continuous infusion by Alzet minipumps, we tested the ability of the catechol estrogens, 2-hydroxyestrone (2-OHE1) and 2-hydroxyestradiol (2-OHE2), as well as two progestins and the anti-estrogen, CI-628, to block the action of estradiol (E2) on sexual behavior, LH surge frequency, uterine weight increase and glucose-6-phosphate dehydrogenase (G6PDH) activity in the uterus and pituitary of ovariectomized rats. Neither catechol estrogen produced inhibitory effects, whereas the potent progestin, R-5020 (5 micrograms/h), and CI-628 (50 micrograms/h) inhibited the E2-induced increase in the LH surge frequency and lordosis response. Progesterone at 20 micrograms/h and CI-628 at 5 micrograms/h did not influence these end points. In the pituitary and uterus, the concurrent administration of R-5020 and E2 attenuated the increase of G6PDH activity. As expected, CI-628 inhibited the action of E2 on G6PDH but was more effective in doing so at the lower of the two doses. CI-628 (50 micrograms/h) also blocked the neuroendocrine and behavioral effects of 2-OHE2 (1 microgram/h) and 4-hydroxyestradiol (0.1 microgram/h). Taken together with our previous studies, these results are consistent with the notion that the catechol estrogens exert effects on sexual behavior and LH surge frequency by virtue of their estrogenic properties rather than by other means.

Animals↗
PubMed1987

Effect of catechol estrogens on prolactin secretion in the rat: lack of correlation with estrogenic activity.

Temporal changes in plasma prolactin (PRL) levels caused by the administration of a number of different catechol estrogens to freely-moving conscious male rats were determined. The steroids with a wide range of affinity for the estrogen receptor were given in a single bolus (100 micrograms/kg) into the right atrium via an indwelling cannula. Plasma PRL concentration was monitored by taking blood samples every 2 min. The effect on PRL secretion was found to be more pronounced when the catechol estrogens were administered to rats bearing implants of estradiol and could not be correlated with their Kd values for the estrogen receptor. The synthetic estrogen, diethylstilbestrol, behaved anomalously by producing an elevation in plasma PRL only in estradiol-primed animals or after prolonged infusion. Diethylstilbestrol-treated rats showed no PRL response to 2-hydroxyestrone unlike those bearing Silastic capsules of estradiol. The experiments support the hypothesis that catechol estrogens generally act as short-term dopamine agonists, lowering PRL, but that those which possess estrogenic activity also show a more prolonged PRL-elevating effect. Thus, the overall action of this group of steroids will be determined by factors which influence these two parameters.

Animals↗
PubMed2004

Sex hormones influence on the immune system: basic and clinical aspects in autoimmunity.

Sex hormones seem to play an important role as modulators of the autoimmune disease onset/perpetuation. Generally, steroid hormones are implicated in the immune response, with estrogens as enhancers at least of the humoral immunity and androgens and progesterone (and glucocorticoids) as natural immunosuppressors. Synovial fluid levels (SF) of proinflammatory estrogens relative to androgens are significantly elevated in both male and female rheumatoid arthritis (RA) patients, as compared to controls, which is most probably due to increase of local enzymatic aromatase activity. Serum levels of estrogens have been found altered in RA patients, particularly estradiol in man. Thus, available steroid prehormones are rapidly converted to proinflammatory estrogens in the synovial tissue in the presence of inflammatory cytokines (i.e., TNFalpha, IL-1, IL-6). The increased estrogen concentrations observed in RA SF of both sexes are characterized mainly by the hydroxylated forms, in particular, 16alpha-hydroxyestrone, showing a mitogenic tumor growth stimulating role. Altered serum hydroxylated estrogens have been found also in serum of systemic lupus erythematosus (SLE) patients. As a matter of fact, our recent studies indicate that 17-beta estradiol (E2) clearly enhanced the expression of markers of cell growth and proliferation, whereas testosterone (T) induced an increase of markers indicating DNA damage and apoptosis. In particular, our data further shows that the enhancing role of estrogens on immune/inflammatory response is exerted by activating the NFkB complex pathway. In conclusion, locally increased estrogens (i.e., synovial tissue in RA or skin in SLE) might exert activating effects on cell proliferation, including macrophages and fibroblasts, suggesting new roles for estrogens in autoimmunity.

Androgens↗
PubMed1999

Effect of flaxseed consumption on urinary estrogen metabolites in postmenopausal women.

Flaxseed, the richest known source of plant lignans, has been shown to have chemoprotective effects in animal and cell studies. Some of its effects may be mediated through its influence on endogenous hormone production and metabolism. Two competing pathways in estrogen metabolism involve production of the 2-hydroxylated and 16 alpha-hydroxylated metabolites. Because of the proposed differences in biological activities of these metabolites, the balance of the two pathways has been used as a biomarker for breast cancer risk. We examined the effects of flaxseed consumption on urinary estrogen metabolite excretion in postmenopausal women. Twenty-eight postmenopausal women were studied for three seven-week feeding periods in a randomized crossover design. During the feeding periods, subjects consumed their usual diets plus ground flaxseed (0, 5, or 10 g/day). Urinary excretion of the estrogen metabolites 2-hydroxyestrogen (2-OHEstrogen) and 16 alpha-hydroxyestrone (16 alpha-OHE1) as well as their ratio, 2/16 alpha-OHE1, was measured by enzyme immunoassay. Flaxseed supplementation significantly increased urinary 2-OHEstrogen excretion (p < 0.0005) and the urinary 2/16 alpha-OHE1 ratio (p < 0.05) in a linear, dose-response fashion. There were no significant differences in urinary 16 alpha-OHE1 excretion. These results suggest that flaxseed may have chemoprotective effects in postmenopausal women.

Aged↗