Phytoestrogens Induce Differential Estrogen Receptor Alpha- or Beta-Mediated Responses in Transfected Breast Cancer Cells

Increased intake of phytoestrogens may be associated with a lower risk of cancer in the breast and several other sites, although there is controversy surrounding this activity. One of the mechanisms proposed to explain the activity of phytoestrogens is their ability to bind and activate human estrogen receptor a (ERα) and human estrogen receptor β (ERβ). Nine phytoestrogens were tested for their ability to transactivate ERα or ERβ at a range of doses. Mammary adenocarcinoma (MCF-7) cells were co-transfected with either ERα or ERβ, and an estrogen-response element was linked to a luciferase reporter gene. Dose-dependent responses were compared with the endogenous ligand 17β-estradiol. Purified genistein, daidzein, apigenin, and coumestrol showed differential and robust transactivation of ERα- and ERβ-induced transcription, with an up to 100-fold stronger activation of ERβ. Equol, naringenin, and kaempferol were weaker agonists. When activity was evaluated against a background of 0.5 nM 17β-estradiol, the addition of genistein, daidzein, and resveratrol superstimulated the system, while kaempferol and quercetin were antagonists at the highest doses. This transfection assay provides an excellent model to evaluate the activation of ERα and ERβ by different phytoestrogens in a breast cancer context and can be used as a screening bioassay tool to evaluate the estrogenic activity of extracts of herbs and foods.

Decrease of postprandial endothelial dysfunction by spice mix added to high-fat hamburger meat in men with Type 2 diabetes mellitus

AIMS

Consumption of a high-fat diet has been demonstrated to promote endothelial dysfunction, possibly through an increase in lipid peroxidation and decrease in serum nitric oxide. The present study was designed to investigate whether consumption of a hamburger cooked with a polyphenol-rich spice mixture will reduce postprandial lipid oxidation and endothelial dysfunction in men with Type 2 diabetes.

METHODS

Twenty-two subjects consumed burgers cooked with salt only (control burger) or with salt and spice mix (spice burger) in randomized order. The postprandial concentration of urinary malondialdehyde and nitrate/nitrite as well as the peripheral arterial tonometry score were determined.

RESULTS

Eighteen subjects completed the study. Postprandial serum glucose, insulin and triglyceride concentrations were similar in all subjects after control burger or spice burger consumption. Urine malondialdehyde excretion in mmol/g creatinine was reduced by 31% (P < 0.001) after consuming the spice burger compared with the control burger. Two hours after consumption of the burgers, the peripheral arterial tonometry score was significantly different between control burger consumption (-9.7 ± 21.5%) and spice burger consumption (+18.0 ± 42.4%) (P = 0.025). Mean urinary nitrate/nitrite concentrations in urine collected during the 6 h after consumption of the control burger was 9.09 ± 5.7 mmol/g creatinine, but 12.37 ± 7.00 mmol/g creatinine after the spice burger (P = 0.053).

CONCLUSION

Adding a spice mix to hamburger meat prior to cooking resulted in a reduction in urinary malondialdehyde, an increase in urinary nitrate/nitrite and improvement of postprandial endothelial dysfunction in men with Type 2 diabetes. Therefore, cooking a hamburger with a polyphenol-rich spice mixture may lead to potential cardiovascular benefits in patients with Type 2 diabetes mellitus.

Feasibility of a low-fat/high-fiber diet intervention with soy supplementation in prostate cancer patients after prostatectomy

OBJECTIVES

To evaluate the feasibility and long-term compliance with a low-fat diet supplemented with soy protein in men at increased risk for recurrence after radical prostatectomy.

DESIGN

Randomized, control study.

SETTING

Academic center in USA.

SUBJECT

Forty men who had undergone radical prostatectomy and were at increased risk for recurrence.

INTERVENTION

Low-fat (15% fat), high-fiber (18 g/1000 kcal) diet supplemented with 40 g soy protein isolate (n=26) was compared to USDA recommended diet (n=14).

RESULTS

Over 4 years, subjects in the intervention group but not in the control group made and sustained significant changes in their diet as measured by the dietary assessment instruments and urinary isoflavone excretion. In the intervention group, dietary fat intake was reduced from 33.46+/-1.27% energy/day to 21.04+/-1.74% (P<0.05), fiber intake increased from 14.6+/-1.06 to 21.05+/-2.29 g/day. The insulin growth factor-1 (IGF-1) level was decreased from 260.4+/-8.6 ng/ml at baseline to 220.5+/-7.9 ng/ml at 6 months (P<0.05) in the intervention group with no significant change in the control group. An ex vivo assay demonstrated inhibition of LNCaP cell growth (-20.0+/-7.7%, P<0.05) by sera from patients in the intervention group after 6 months of dietary change compared to baseline.

CONCLUSION

These data suggest that long-term low-fat dietary interventions as part of prospective randomized trials in prostate cancer survivors are feasible, and lead to reductions in circulating hormones or other growth factors stimulating prostate cancer growth ex vivo.

Assessing the accuracy of a food frequency questionnaire for estimating usual intake of phytoestrogens

The primary objective of this study was to assess the accuracy of a modified Block food frequency questionnaire (FFQ) with respect to its ability to assess usual dietary intakes of daidzein and genistein. Participants were a convenience sample of 51 Japanese and 18 Caucasian women. All interviews were conducted between February 1997 and October 1997. At each of the four study visits, participants provided a 24-hour urine specimen and a 48-hour dietary recall. At the first visit, participants also completed an interviewer-administered modified Block FFQ. The daidzein and genistein intakes estimated using the FFQ were moderately correlated with the mean estimates of daidzein and genistein intake calculated from four 48-hour dietary recalls (correlation for daidzein = 0.49-0.58 and correlation for genistein = 0.45-0.54) and estimates of urinary concentrations of these compounds calculated from four collections (correlations for daidzein and genistein = 0.49 and 0.30, respectively). The accuracy of the modified Block FFQ for assessment of usual daidzein and genistein intakes is supported by this study. These results support the use of this instrument in epidemiological studies as an easy and low-cost method to assess the usual dietary daidzein or genistein intake.

Moderate folate depletion increases plasma homocysteine and decreases lymphocyte DNA methylation in postmenopausal women

To determine the human folate requirement on the basis of changes in biochemical pathways, we studied the effect of controlled folate intakes on plasma homocysteine and lymphocyte DNA methylation and deoxynucleotide content in healthy postmenopausal women. Eight women (49-63 y of age) were housed in a metabolic unit and fed a low folate diet containing 56 microg/d of folate for 91 d. Folate intake was varied by supplementing 55-460 microg/d of folic acid (pteroylglutamic acid) to the diet to provide total folate intake periods of 5 wk at 56 microg/d, 4 wk at 111 microg/d and 3 wk at 286-516 microg/d. A subclinical folate deficiency with decreased plasma folate was created during the first two periods. This resulted in significantly elevated plasma homocysteine and urinary malondialdehyde, and lymphocyte DNA hypomethylation. The folate depletion also resulted in an increased ratio of dUTP/dTTP in mitogen-stimulated lymphocyte DNA and decreased lymphocyte NAD, changes suggesting misincorporation of uracil into DNA and increased DNA repair activity. The DNA hypomethylation was reversed with 286-516 microg/d of folate repletion, whereas the elevated homocysteine decreased with 516 but not 286 microg/d of folate. The results indicate that marginal folate deficiency may alter DNA composition and that the current RDA of 180 microg/d may not be sufficient to maintain low plasma homocysteine concentrations of some postmenopausal women.

NADPH-cytochrome P-450 reductase, cytochrome P-450 2C11 and P-450 1A1, and the aryl hydrocarbon receptor in livers of rats fed methyl-folate-deficient diets

We investigated three hepatic cytochrome P-450 isozymes and the aryl hydrocarbon (Ah) receptor in rats fed one of the following three diets for 15 months: a diet containing the AIN vitamin mixture (control), the control diet devoid of choline and folate (CFD), or the CFD diet devoid of niacin (CFND). Hepatic tumors developed in all CFD- and CFND-fed rats. Western blot analyses of nontumor hepatic tissue showed that NADPH-cytochrome P-450 reductase (P-450 reductase) increased significantly in the CFD and CFND groups compared with the control group. Hepatic cytochrome P-450 2C11 (CYP2C11) was not detectable in the CFD and CFND groups compared with the control group. Ah receptor and cytochrome P-450 1A1 (CYP1A1) were detected in higher amounts in livers of both deficient groups. CYP1A1 is an enzyme associated with bioactivation of exogenous genotoxins. To our knowledge, this is the first time it has been shown that CYP1A1 and the Ah receptor are induced by dietary deficiencies.

Plasma carotenoids and the prevalence of adenomatous polyps of the distal colon and rectum

In a case-control study, the authors investigated relations between plasma carotenoid concentrations and the prevalence of colorectal adenomatous polyps (precursors to colorectal cancer) in residents of Los Angeles County and Orange County, California, from 1991 through 1993. Plasma concentrations of six carotenoids were compared in 472 asymptomatic cases with a first-time diagnosis of at least one adenomatous polyp of the distal colon or rectum and 502 matched controls. Odds ratios adjusted for age, sex, smoking, alcohol intake, and energy, saturated fat, and fruit and vegetable intake revealed no associations between any of the individual carotenoids and polyp prevalence or between total carotenoids and polyp prevalence.

Vitamins C, E and A and heme oxygenase in rats fed methyl/folate-deficient diets

There is evidence that the development of hepatocarcinoma in rats fed a methyl-deficient diet is associated with oxidative stress. We investigated, therefore, whether the tissue concentrations of the antioxidant vitamins ascorbic acid (AA) and alpha- and gamma-tocopherol (T) are altered in methyl/folate deficiency. We also measured retinol concentrations in tissues and hepatic mRNA expression of heme oxygenase (HO1). A 6% gelatin, 6% casein diet, devoid of choline and folate (CFD) was selected based on the high rate of tumor development in rats fed this diet. Spectrophotometric measurement of AA and HPLC determination of tissue T and retinol showed decreased concentrations of AA in blood; alpha- and gamma-T in lung, heart and plasma, alpha-T and retinol in liver; retinol in lung; and increased expression of hepatic HO1 mRNA. Similar alterations in tissue vitamin concentrations were found when the CFD diet devoid of niacin (CFND) was fed. Reducing alpha-T in the CFND diet (CFNED) further decreased hepatic alpha-T concentrations. These results show that chronic methyl/folate deficiency is associated with a compromised antioxidant defense system.

Male rats fed methyl- and folate-deficient diets with or without niacin develop hepatic carcinomas associated with decreased tissue NAD concentrations and altered poly(ADP-ribose) polymerase activity

Folate is an essential cofactor in the generation of endogenous methionine, and there is evidence that folate deficiency exacerbates the effects of a diet low in choline and methionine, including alterations in poly(ADP-ribose) polymerase (PARP) activity, an enzyme associated with DNA replication and repair. Because PARP requires NAD as its substrate, we postulated that a deficiency of both folate and niacin would enhance the development of liver cancer in rats fed a diet deficient in methionine and choline. In two experiments, rats were fed choline- and folate-deficient, low methionine diets containing either 12 or 8% casein (12% MCFD, 8% MCFD) or 6% casein and 6% gelatin with niacin (MCFD) or without niacin (MCFND) and were compared with folate-supplemented controls. Liver NAD concentrations were lower in all methyl-deficient rats after 2-17 mo. At 17 mo, NAD concentrations in other tissues of rats fed these diets were also lower than in controls. Compared with control values, liver PARP activity was enhanced in rats fed the 12% MCFD diet but was lower in MCFND-fed rats following a further reduction in liver NAD concentration. These changes in PARP activity associated with lower NAD concentrations may slow DNA repair and enhance DNA damage. Only rats fed the MCFD and MCFND diets developed hepatocarcinomas after 12-17 mo. In Experiment 2, hepatocarcinomas were found in 100% of rats fed the MCFD and MCFND diets. These preliminary results indicate that folic acid deficiency enhances tumor development. Because tumors developed in 100% of the MCFD-fed rats and because tissue concentrations of NAD in these animals were also low, further studies are needed to clearly define the role of niacin in methyl-deficient rats.

Blood antioxidants changes in young women following beta-carotene depletion and repletion

OBJECTIVE

This study was undertaken to investigate the relationship between beta-carotene intake and biochemical indices of antioxidant status in the blood of nine premenopausal women ages 18 to 42.

METHODS

Nine healthy adult women were fed a low beta-carotene diet for 68 days. They were repleted with the same diet supplemented with beta-carotene (15 mg beta-carotene) for 28 days. During the last week of the study, they received an additional mixed carotenoid supplement. Indices of blood antioxidant status were measured on days 1, 29, 36, 43, 50, 64, 71, 92, and 99.

RESULTS

We found significant increases of erythrocyte conjugated dienes between the 71st and 99th day of the study; increases of glutathione (GSH) peroxidase (GP) on day 43 and day 92 compared to a decrease on day 29; and decreases of GSH reductase throughout the treatment period. Erythrocyte catalase activities seemed to parallel GP activities. Erythrocyte oxidized glutathione (GSSG) levels were depressed both after beta-carotene depletion and repletion. beta-Carotene depletion/repletion had no effect on plasma vitamin E or GSH levels. Platelet GSH levels were depressed after beta-carotene depletion followed by elevated GSH levels after beta-carotene repletion.

CONCLUSION

A diet low in beta-carotene and adequate in all other nutrients, including vitamin A, resulted in altered erythrocyte and platelet antioxidant indices; however, it had little impact on plasma GSH or vitamin E levels in young healthy women. Our results are consistent with the suggestion that carotenes may be important in the prevention of oxidative damage.

In vivo methylation capacity is not impaired in healthy men during short-term dietary folate and methyl group restriction

Ten healthy adult men were fed a diet low in folate and exogenous methyl groups to study the effects on in vivo methylation capability. The men were housed in a metabolic unit for the entire 108 d of the study. After a 9-d baseline period (Period 1), the men were fed a soy-product-amino acid defined diet for 45 d, which provided 25 micrograms/d of folate for 30 d (Period 2) and, with a folate supplement, 99 micrograms/d for 15 d (Period 3). During Period 2 and Period 3, the low methionine and choline diet was supplemented with methionine for half the subjects to vary the dietary methyl group intake. The periods were then repeated over the next 54 d (Periods 4-6), with a crossover of methionine intakes in Period 5 and Period 6. A 1-g oral dose of nicotinamide was given at the end of each period and methylated urine metabolites determined. Other measures related to in vivo methylation capability included urine creatinine, and plasma and urine carnitine. Even with moderate folate depletion, none of these measures was decreased by low methionine and choline intakes. Plasma methionine concentrations were unchanged throughout. Limiting exogenous methyl group intake by restricting dietary methionine and choline did not impair in vivo methylation capabilities for the variables tested, even at low folate intake.

Homocysteine increases as folate decreases in plasma of healthy men during short-term dietary folate and methyl group restriction

Ten healthy adult men were fed a diet low in folate and exogenous methyl groups to study the effects on folate requirement and status. The men were housed in a metabolic unit for the entire 108-d study. After a 9-d base-line period (P1), the men were fed an amino acid-defined soybean product diet for 45 d, which provided 25 micrograms/d of folate for 30 d (P2) and (with a folate supplement) 99 micrograms/d for 15 d (P3). During P2 and P3, the low methionine and choline diet was supplemented with methionine for half the subjects to vary the dietary methyl group intake. The periods were then repeated over the next 54 d (P4-P6), with a cross-over of methionine intakes in P5 and P6. Restricting dietary methyl group intake did not increase the dietary folate requirement. Plasma total homocysteine rose during folate depletion and correlated inversely with plasma folate; however, the response of homocysteine to changes in folate intake varied among individuals from very strong to absent. The results support previous suggestions that increased plasma homocysteine concentrations provide a marker of functional folate deficiency, and further indicate that individuals may differ greatly in their susceptibility to hyperhomocysteinemia due to low folate intakes. Judged by the lack of normalization of high homocysteine concentrations during folate repletion, the current folate RDA for adult men may not provide the expected margin of protection.

Poly(ADP-ribose) polymerase activity and DNA strand breaks are affected in tissues of niacin-deficient rats

The niacin cofactor, NAD, is the substrate for poly(ADP-ribose) polymerase, an enzyme associated with DNA repair. We investigated, therefore, whether hepatic poly(ADP-ribose) polymerase activity was altered and DNA strand breaks in lymphocytes and liver were greater in niacin-deficient rats. A niacin deficiency was established in weanling rats with diets containing 1.5 mg/kg of niacin. Based on lower growth rates and NAD concentrations in blood, liver and skeletal muscle, this diet maintained rats in a deficient state for 1 mo, and, when the dietary niacin was reduced to 0.5 mg/kg, rats remained deficient for an additional month. The hepatic poly(ADP-ribose) polymerase activity was decreased in one experiment when mean hepatic NAD concentrations were 0.60 and 0.51 mumol/g at d 34 and d 60, respectively, compared with 0.77 and 0.80 mumol/g in pair-fed controls. Enzyme activity, however, was greater than in controls when hepatic NAD concentrations were < 0.30 mumol/g. Strand breaks in DNA did not accumulate except after tissues were exposed to hypoxanthine-xanthine oxidase, a free radical-generating system. Exposure to this system caused more DNA strand breaks in lymphocytes and hepatic nuclei from niacin-deficient rats compared with the same tissues from controls. The results suggest that, in rats, although hepatic poly(ADP-ribose) polymerase activity can be elevated, a severe niacin deficiency may increase the susceptibility of DNA to oxidative damage, likely due to a lower availability of NAD.

Immunocompetence and oxidant defense during ascorbate depletion of healthy men

To determine nonscorbutic effects of moderate vitamin C deficiency we measured immune function and oxidative damage in eight healthy men (25-43 y) who consumed 5-250 mg/d of ascorbic acid over 92 d on a metabolic unit. During ascorbic acid intakes of 5, 10, or 20 mg/d, subjects attained a state of moderate ascorbic acid deficiency as ascorbic acid concentrations in plasma, leucocytes, semen, and buccal cells dropped to less than 50% of baseline with no scorbutic symptoms observed. No changes in cell proliferation, erythrocyte antioxidant enzymes, and DNA strand breaks were observed; however, blood levels of glutathione and NAD(P) decreased during ascorbic acid deficiency, as did delayed hypersensitivity responsiveness. Concentrations of the oxidatively modified DNA base, 8-hydroxydeoxyguanosine in sperm DNA and fecapentaenes, ubiquitous fecal mutagens, were increased during ascorbic acid depletion. Moderate vitamin C deficiency, in the absence of scurvy, results in alteration of antioxidant chemistries and may permit increased oxidative damage.

Glutathione blood levels and other oxidant defense indices in men fed diets low in vitamin C

Because ascorbic acid is an important contributor to the oxidant defense system in body tissues, we studied the effects of a low dietary intake of ascorbic acid on various indicators of oxidant defense and oxidant damage. During a 13-wk study eight healthy men (25-43 y), residing in a live-in metabolic unit, were fed controlled diets containing different amounts of ascorbic acid for four consecutive periods: period 1 = 250 mg/d for 4 d; period 2 = 5 mg/d for 32 d; period 3 = 10 or 20 mg/d for 28 d and period 4 = 60 or 250 mg/d for 28 d. Measurements were made at several time intervals of the activities of glutathione peroxidase and superoxide dismutase in RBC, DNA strand breaks in mononuclear leucocytes, glutathione concentrations in plasma and RBC and NAD and NADP in RBC. After 60 d of low ascorbic acid intakes and associated with plasma ascorbic acid levels less than 6 mumol/L, the total glutathione concentration and the reduced glutathione:oxidized glutathione ratio were decreased in plasma. At the same time NAD and NADP levels in RBC were elevated. It seems that chronic marginal vitamin C deficiency states may be associated with selected biochemical changes in oxidant defense indices.

Hepatic poly(ADP ribose) polymerase activity in methyl donor-deficient rats

Hepatic poly(ADP ribose) polymerase (EC 2.4.2.30) activity as an indicator of DNA damage was measured in rats fed a low methionine, choline-devoid diet (MCD) for a 3-wk period. Additional groups of rats were either injected intraperitoneally (i.p.) with large doses of nicotinamide (NAM) or saline or fed the MCD diet without folic acid (MCFD). As a positive control, some rats were fed the MCD diet supplemented with methionine and choline (MCD + Met). In all groups of methyl donor-deficient rats and associated with increases in hepatic lipid levels, hepatic malondialdehyde concentrations were found to be increased. This observation is evidence for the occurrence of lipid peroxidation in methyl donor deficiency. Methyl donor deficiency was also associated with a significantly elevated hepatic poly(ADP ribose) polymerase activity in all groups of rats as compared to the positive control, suggesting a stimulation of DNA repair processes. The highest enzyme activity was observed in the MCD-NAM i.p. group.

Hepatic content of S-adenosylmethionine, S-adenosylhomocysteine and glutathione in rats receiving treatments modulating methyl donor availability

Because of evidence linking methyl group deficiency and increased tumor formation in experimental animals, we explored other possible methods of producing a methyl group deficiency. Rats fed a low methionine diet lacking choline (MCD) were injected intraperitoneally daily for 3 wk with large doses of nicotinamide. Hepatic levels of lipids were elevated, S-adenosylmethionine (SAM) levels and the SAM:S-adenosylhomocysteine (SAH) ratio were decreased, and SAH level was not consistently changed. In livers of rats fed the MCD diet without folate (MCFD), lipids were also elevated and SAM reduced as compared to MCD-fed rats. In rats fed the MCD diet plus a methionine (Met) supplement (MCD + Met), hepatic SAM levels and the SAM:SAH ratio were higher and lipid levels lower than in MCD-fed rats, indicating that the MCD diet is marginally deficient in methyl donor groups. The injection of nicotinamide or the removal of folate from the MCD diet increased the severity of methyl donor deficiency, as shown by lower hepatic SAM levels and higher hepatic lipid levels. Hepatic glutathione levels were similar in MCD- and MCFD-fed rats and were lower than in rats fed the methionine-supplemented MCD diet or injected with nicotinamide.