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Session 1: Isoflavone absorption/metabolism and effects of processing |
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 TOP Session 1: Isoflavone... Session 2: Osteoporosis. In...Session 3: Cancer. In...Session 4: Hormonal effects....Session 5: Coronary heart...Session 6: Research identifying...Session 7: Plenary session....Session 8: Plenary session....Session 9: Panel discussion....REFERENCES |
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and S. H. Zeisel.Division of Cancer Prevention, National Cancer Institute,
Bethesda, MD; *Research Triangle Institute, Research Triangle Park, NC;
and University of North Carolina, Chapel Hill, NC.The National Cancer Institute has sponsored an investigational new drug application, in collaboration with Protein Technologies International, to conduct single-dose, phase 1 pharmacokinetic and safety studies of well-characterized isoflavone mixtures in men and women. Before the initiation of the trial, a sensitive analytical method was developed and validated to measure free and conjugated genistein and daidzein in plasma and urine. The proprietary mixtures were administered on the basis of genistein. Five groups of three subjects were administered the mixtures at 1, 2, 4, 8 and 16 mg/kg body weight. Blood and urine samples were collected and analyzed to determine pharmacokinetic parameters. Safety was monitored by clinical signs, clinical chemistry values, hematology and follow-up. Results from the study in men will be presented. Pharmacologic plasma levels of free genistein up to ~100 ng/mL and of conjugated genistein up to ~7500 ng/mL were achieved. The repeat-dose portion of the phase 1 studies is now being initiated.
Kinetics of Isoflavone Redistribution in Soymilk Processing. Patricia A. Murphy, Kobita Barua, Cata Flores and Tong Song. Department of Food Science and Human Nutrition, Iowa State University, Ames, IA.
Isoflavones in soy products are present as aglycons, glycosides, malonylglucosides and acetylglucosides. A detailed kinetic study of the rearrangement of the different forms during heat processing of soy milk was conducted. In raw soy milk, the predominant forms are the malonylglucosides. If the soy milk is not heat processed, <1% isoflavone glucosides are hydrolyzed by native soybean glucosidases to the aglycons. Immediate heat processing of soy milk (after extraction from soybeans), to model aseptic heat processing, results in quantitative conversion of malonylglucosides to glucosides. Few acetylglucosides are produced until soy milk is exposed for >60 min at 80°C. Optimization of isoflavone extraction conditions and times is critical to extract all isoflavone forms, and data will demonstrate acetonitrile/water as the best solvent mixture for soyfood analysis. Apparent first-order rate constants and half-lives for interconversions of isoflavone forms will be presented to design optimal processing conditions.
Database of Isoflavone Values for Foods. G. R. Beecher, S. Bhagwat, D. Haytowitz, J. M. Holden and P. A. Murphy.* Beltsville Human Nutrition Research Center, ARS, USDA, Beltsville, MD and *Iowa State University, Department of Food Science and Human Nutrition, Iowa State University, Ames, IA.
Isoflavones are well-known phytonutrients of soybeans and soy-containing foods that have several biological activities associated with health promotion. However, they were not linked with risk of chronic diseases for lack of a database of food values. Such a database was developed. About 30 scientific papers were identified that contained data on the isoflavone content of soy-based and a few other foods. Also, isoflavone data were generated from an extensive sampling of soy-containing foods in the United States. Data for daidzein, genistein, glycitein and their glucosides were critically evaluated. Total aglycone values of each isoflavone were calculated by converting glucoside forms into aglycones on the basis of molecular weight ratios and by adding them to their respective free aglycone values. Acceptable data for each isoflavone and food combination were combined to generate mean values for aglycone forms and total isoflavone content. The number of values used to calculate the mean, standard errors of the means and confidence codes (reliability indicator) also were determined. Data for 140 foods, including soy ingredients, were tabulated and assigned USDA Nutrient Database codes. The source of data for each food is shown and all references are listed. The database is available at .http://www.nal.usda.gov/fnic/foodcomp. [Partially funded by U.S. Department of the Army.]
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Session 2: Osteoporosis. In vitro, animal and human studies |
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TOPSession 1: Isoflavone...Session 2: Osteoporosis. In...Session 3: Cancer. In...Session 4: Hormonal effects....Session 5: Coronary heart...Session 6: Research identifying...Session 7: Plenary session....Session 8: Plenary session....Session 9: Panel discussion....REFERENCES |
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and ß and During Cell
Differentiation. J.J.B. Anderson, X. W. Chen and
S. C. Garner.* Department of Nutrition, University of North
Carolina, Chapel Hill, NC and *Department of Surgery, Duke Medical
Center, Durham, NC.
We examined the effects of 17ß-estradiol (E2) and
genistein, a phytoestrogen, on an osteoblast-like cell (MC3T3-E1)
during differentiation. The recent discovery of the ß isoform of the
estrogen receptor (ER) suggests that the molecular regulation of
osteoblast activity by estrogens may be more complex than previously
thought. This discovery raised a number of questions regarding the
respective physiologic roles that these two receptors, ER- and
ER-ß, may play in an estrogen-responsive tissue. MC3T3-E1 cells
were cultured for up to 12 d, and samples were collected on d 2,
4, 6, 8, 10 and 12. Reverse-transcription polymerase chain reaction
was performed with gene-specific primers, and predicted product
sizes of 431 and 355 base pairs for mER- and mER-ß, respectively,
were obtained. The ratio of mER- expression to mER-ß expression
increased ~10-fold from d 2 to 12 (P < 0.05) and
indicated that ER- increased in the postconfluent cells. This result
suggests that ER- expression in vitro may be related to specific
cellular developmental requirements and to the regulation of
estrogen-responsive genes, which modulate the number of ER. We then
incubated cells with either E2 or genistein (10 nmol/L
each) on d 0–2 or 4–6. On d 12, the production of interleukin 6
(IL-6) and alkaline phosphatase (ALP) and the mRNA expression of ER,
osteocalcin and collagen (type I) were measured. The effects of
E2 and genistein on the production of ALP and the mRNA
expression of osteocalcin and collagen (type I) did not differ
significantly. However, we found higher responses for the concurrent
expression of ER and the synthesis of IL-6 in cells stimulated by
genistein on d 4–6 than on d 0–2. In contrast, we found higher
responses for the expression of ER and the synthesis of IL-6 in cells
stimulated by E2 on d 0–2 than on d 4–6. In summary,
expression of ER- and ER-ß varies during differentiation, and the
inhibition of IL-6 synthesis by E2 or genistein may be
related to the expression of both ER- and ER-ß. We suggest that
ER- and ER-ß may play different roles in osteoblast phenotype
development during differentiation.
Soy Isoflavones May Enhance Bone Density in
Ovariectomized Rats. E. H. Jeffery, J. Walsh, A.
Rivera,* V. Jarrell, M. Black, G. Evans,R. Turner and J. Bahr.* Departments of
Food Science and Human Nutrition and *Animal Sciences, University of
Illinois, Urbana, IL and Department of Orthopedics, Mayo
Clinic, Rochester, MN.
Soy protein is proposed to delay bone loss in ovariectomized (ovx) rats and postmenopausal women. Sprague-Dawley rats (4 mo old, n =10/group) were ovariectomized or subjected to sham surgery (intact group), then fed for 3 mo the following diets that differed in their protein sources: casein, soy protein (soy) or casein with an isoflavone-rich ethanol extract of soy (iso). Intact, ovx negative control and ovx 17ß-estradiol (E2) positive control groups received a 20% casein diet (a silastic implant provided 30–40 pg E2/mL plasma for the ovx E2 group). Experimental diets were low soy (10% casein, 10% soy), high soy (20% soy), low iso (20% casein, 0.04% iso) and high iso (20% casein, 0.08% iso). Rats were fed 13–16 g/d, on the basis of the unlimited intake of the intact group. By 2 mo, bone mineral density (BMD) of distal and proximal femur and spine (L3, L4) was decreased (P < 0.05) in ovx casein compared with intact rats. The BMD of distal and proximal femur and spine (L2, L3, L4) in ovx low soy, high soy or low iso rats were not significantly different from those of the ovx casein group. Conversely, ovx high iso rats had increased BMD of distal and proximal femur and spine (L2, L3, L4) compared with the ovx casein group (P < 0.05), with BMD of proximal femur not significantly different from that of the intact or ovx E2 groups. These data support a role for soy isoflavones in prevention of bone loss in the absence of endogenous estrogen.
Effect of Soy Protein on Bone Metabolism. J. C. Gallagher, K. Rafferty, V. Haynatzka and M. Wilson. Bone Metabolism Unit, Creighton University School of Medicine, Omaha, NE.
Several beneficial effects of soy protein were claimed for the
prevention of heart disease and osteoporosis. These effects may be
mediated through the soy isoflavones, which are known to bind the
estrogen receptor. We performed a study in early postmenopausal women
of the effect of soy protein with two levels of isoflavones; 65 women,
mean age 55 y, were randomly assigned to one of three groups in a
double-blind study—Group A received soy with 96 mg, Group B
received soy with 52 mg isoflavones and Group C received soy protein
without isoflavones. Treatment was given for 9 mo. Bone mineral density
(BMD) was measured at baseline and after 9 mo. The results showed no
effect of any of the supplemented soy compounds on spine or femur BMD
(Table 1
). There were no significant differences among the three groups in
spine, femoral neck or trochanter BMD during the intervention phase.
Measurement of serum isoflavones at 3 mo showed dose-related
increases in the two supplemented groups; in the 96-mg group, the serum
isoflavones were 10 times greater than those in the nonsupplemented
group. In summary, soy supplemented with 52 and 96 mg of isoflavones
had no effect on spine or femur BMD, suggesting that this level of
isoflavones is ineffective in the prevention of early postmenopausal
bone loss.
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Departments of Food Science and Human Nutrition and *Statistics,
Iowa State University, Ames, IA and Research and
Development Laboratory, Fujicco Co., Ltd., Kobe Hyogo, Japan.We examined the effects of isoflavone-rich (80.4 mg/d) soy protein isolate (SPI+) on lumbar spine bone mineral density (BMD), urinary N-telopeptides (N-Tx) and serum bone-specific alkaline phosphatase (BAP) in perimenopausal women randomly assigned (double blind) to the following treatments for 24 wk: isoflavone-rich soy (SPI+; n = 24), isoflavone-deficient soy (SPI-; n = 24), or whey (control; n = 21) protein. There was no change (%) in lumbar spine BMD in the SPI+ group (-0.2%, P = 0.73); the control group lost bone (-1.3%, P = 0.0041); and loss in the SPI- group approached significance (-0.7%, P = 0.097). Regression analysis indicated that isoflavones exerted a positive effect on the percentage of change in BMD (P = 0.023), the overall model accounting for 38.3% (P = 0.0002) of its variability. Baseline BMD (P < 0.0001) affected (negatively) the percentage of change in BMD, whereas baseline body weight (P = 0.0036) contributed positively. Serum BAP at post-treatment negatively affected percentage change in BMD (P = 0.0016), suggesting that with higher BAP, more bone was lost. Contrast coding using analysis of covariance indicated that isoflavones, not soy protein per se, exerted the effect. Serum BAP did not decline in SPI+ (P = 0.90) and SPI- (P = 0.76) groups, whereas the control group had some decline (P = 0.092; NS). Urinary N-Tx did not decline in SPI+ (P = 0.91) at wk 12, in contrast to the control and SPI- groups, but rose in all groups from mid- to post-treatment. Results suggest that the bone-sparing effect of soy isoflavones may be different from that of estrogen or other antiresorptive agents in that both bone resorption and formation remained elevated. Overall, soy isoflavones attenuated bone loss from the lumbar spine of estrogen-deficient perimenopausal women.
Dietary Soy Isoflavones Favorably Influence Lipids and Bone
Turnover in Healthy Postmenopausal Women. Michael D.
Scheiber, James H. Liu, M.T.R. Subbiah,* Robert W. Rebar and
Kenneth D. R. Setchell. Departments of
Obstetrics and Gynecology, *Internal Medicine, and
Pediatrics, University of Cincinnati College of Medicine,
Cincinnati, OH.
The benefits of hormone replacement therapy for reducing risk for cardiovascular disease and osteoporosis are well established in postmenopausal women. However, the perceived risks and unwanted side effects from these relatively potent estrogens have led to the search for more natural forms of estrogen replacement and for agents that will have selective actions. Phytoestrogens such as isoflavones, which are abundant in most soy foods or can be obtained as supplements, are being investigated for their potential to fill this niche. The preferential binding of the soy isoflavone genistein to estrogen receptor ß found in the vascular endothelium and in bone begs the question whether a phytoestrogen-rich diet can offer any bone or cardiovascular-protecting benefits to women in periods of estrogen deficiency. To address this issue, we conducted a single open-group longitudinal study of 43 postmenopausal women who consumed a diet of soy foods that delivered 60–70 mg total isoflavones each day for 12 consecutive weeks. Bioavailability of the isoflavones was confirmed from plasma kinetics of absorption and clearance. After 12 wk, the mean HDL cholesterol increased significantly (3.7%, P < 0.05) and the ratio of total to HDL cholesterol decreased (5.5%, P < 0.006). A significant increase (9.9%, P < 0.05) in LDL cholesterol peroxidation lag time was observed, which was consistent with a beneficial antioxidant effect on lipid peroxidation. The LDL peroxidation lag time correlated with the serum isoflavone levels. For bone markers, osteoclast activity assessed from the urinary excretion of N-telopeptides (N-Tx) decreased 13.9% (P < 0.02), whereas osteoblast activity evidenced from serum osteocalcin increased 10.2% (P < 0.03). There was a significant negative correlation between urinary N-Tx and serum isoflavone concentrations. These findings indicate reduced bone turnover, which was evident after 4 wk and significant after 12 wk of dietary intervention with an isoflavone-rich diet. In conclusion, including soy products containing 60–70 mg/d of isoflavones in the diet had a significant positive effect on LDL oxidation, HDL cholesterol and bone turnover in healthy postmenopausal women. [Supported by grants from the North American Menopause Society, the National Institutes of Health (5 R01 CA73328) and Sanitarium Health Food Company, Berkeley Vale, NSW, Australia.]
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Session 3: Cancer. In vitro, animal and human studies |
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TOPSession 1: Isoflavone...Session 2: Osteoporosis. In...Session 3: Cancer. In...Session 4: Hormonal effects....Session 5: Coronary heart...Session 6: Research identifying...Session 7: Plenary session....Session 8: Plenary session....Session 9: Panel discussion....REFERENCES |
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Dietary intake of soy has been linked with decreased cancer risk. Some of the active compounds in soy were identified and include the isoflavones genistein and daidzein. As part of a pilot study to assess the potential benefits of a soy extract, Novasoy, we examined levels of oxidative damage in blood of six women before and after supplementation with Novasoy. This supplement contains ~50 mg soy isoflavones and was consumed once daily by the women. Blood samples were obtained from the women at weekly intervals for 3 wk. Plasma levels of genistein and daidzein increased after supplementation, with maximal levels occurring after 2 wk. Maximal levels were higher in women with lower body weights. Levels of daidzein were higher than those of genistein. The same blood samples were also analyzed for markers of oxidative damage. DNA was isolated from the blood nuclei and analyzed for 5-hydroxy-methyl-2'-deoxyuridine (5-OHmdU). The mean level of 5-OHmdU decreased by 35% (relative to baseline) after 1 wk and by ~50% after 2 and 3 wk of supplementation. Mean plasma levels of 8-isoprostanes also decreased somewhat after supplementation. Because increased levels of oxidative damage are associated with increased cancer risk, these results indicate that soy supplementation could have potential use in cancer prevention.
Chemoprevention Trials of Soy Isoflavones and Other Promising Dietary Nutrients: Overview of NCI Phase II/III Cancer Prevention Trials. Ronald Lieberman. Prostate and Urologic Cancer Research Group, Division of Cancer Prevention, National Cancer Institute, Rockville, MD.
The terms alternative and complementary medicine are commonly applied
to dietary supplements recently classified by the Dietary Supplement
Health Education Act (DSHEA) as herbs or other botanicals, vitamins and
minerals, and amino acids. Many of these natural compounds derived from
plant sources (soy isoflavones and other phytochemicals) and
concentrated in fruits and vegetables (antioxidants and micronutrients)
could be developed as pharmaceutical products, depending on the
scientific evidence with respect to pharmacokinetics, pharmacodynamics,
safety and efficacy. The level of scientific and regulatory evidence
required during the clinical phases of pharmaceutical development is
specified in the Code of Federal Regulations. Cancer chemoprevention is
defined as the administration of well-defined chemicals (drugs,
biologics, nutrients) to prevent, reverse, or delay one or more stages
in the multistep process of carcinogenesis. Because of provocative
epidemiologic and clinical evidence linking phytoestrogens, carotenoids
and other micronutrient antioxidants to reduced cancer risk, including
prostate cancer, chemoprevention has gained prominence among clinical
investigators, nutritional scientists, the pharmaceutical and
nutriceutical industries and government agencies (National Institutes
of Health, Food and Drug Administration). Because of the major
implications that a positive or negative randomized controlled trial
(highest level of evidence) would have for health care professionals
and the public, the National Institutes of Health and the National
Cancer Institute have conducted or initiated a number of small- and
large-scale clinical trials to evaluate the benefits and adverse
effects of promising dietary nutrients including soy isoflavones, green
tea polyphenols, calcium, vitamin D analogs, carotenoids,
-tocopherol (vitamin E) and selenium. An overview of recently
completed chemoprevention trials as well as the rationale and the
design of new trials under development and in progress will be
presented.
Dietary Soy Is Associated with Decreased Cell Proliferation Rate and Zone in Colon Mucosa of Subjects at Risk for Colon Cancer. M. R. Bennink, D. Thiagarajan, L. D. Bourquin and J. E. Mayle. Michigan State University, East Lansing, MI.
A double-blind, prospective study was designed to determine whether consumption of 39 g/d of isolated soy protein or casein (control) would influence colonic cell proliferation patterns. Twenty-nine subjects (19 men and 10 women) consumed soy, and 13 subjects (9 men and 4 women) consumed casein supplements for 1 y. All subjects had a history of adenomatous polyps or colon cancer. Average age was 59 y (range 37–70 y). Compliance for soy consumption was excellent (>92%) as indicated by isoflavone excretion in bimonthly, random urine specimens. There were no adverse changes in blood or urine chemistry values associated with soy or casein consumption. This study used cell proliferation patterns in colonic mucosa as surrogate biomarkers to indicate cancer risk. Subjects at increased risk of developing colon cancer have altered cell proliferation patterns in the colonic mucosa. Increased frequency of cell proliferation in the upper 40% of the crypt indicates delayed or reduced differentiation and increased risk for developing colon cancer. Also, there is a tendency for an increased mitotic index throughout the crypt for individuals predisposed to colon cancer. Proliferation zones and mitotic indices were measured by immunohistochemical detection of proliferative nuclear antigen (PCNA) in colon biopsies obtained before and after supplementation. There was a significant reduction in mitotic index (P = 0.02) and proliferation zone (P = 0.06) in subjects who consumed the soy supplement. The labeling index and proliferation zone were unchanged (P > 0.95) for subjects who consumed casein. Because the presence of PCNA indicates that a cell is capable of division, lack of PCNA implies that the cell has terminally differentiated. These results suggest that it is feasible to eat enough soy to enhance cell differentiation in colon mucosa and thereby reduce risk of colon cancer in an at-risk population. [Protein Technologies International, Inc. provided the soy protein isolate (Supro) and casein supplements.]
Effects of Dietary Soy on the Uterus and Breast of Macaques. J. M. Cline, M. Anthony, S. Mathes and T. B. Clarkson. Comparative Medicine Clinical Research Center, Wake Forest University School of Medicine, Winston-Salem, NC.
Soy phytoestrogens (SP) may provide a dietary alternative or
supplement to postmenopausal estrogen replacement therapy. Demographic
studies indicate a cancer-protective effect of SP on the breast and
endometrium. The cancer-preventive effect may be mediated by
estrogen antagonism, tyrosine kinase inhibition, antioxidant activity,
antiangiogenic activity, protease inhibition or alteration of steroid
metabolism. However, there is cause for concern in recent studies that
indicate promotion of cellular proliferation in normal breast
epithelium and breast cancer cells. We showed previously in a 6-mo
study of macaques that dietary SP supplementation [148
mg/(woman · d) equivalent] antagonizes the uterotrophic and
mammotrophic effects of estradiol [1 mg/(woman · d) equivalent]
(Foth and Cline 1998
). Further studies have since indicated that this
antagonistic effect on breast and endometrial proliferation is not
accompanied by antagonism of progesterone receptor (PR) induction in
the same tissues. This finding suggests that at least a part of the
antiproliferative effect is independent of the estrogen receptor
because PR induction is a marker of estrogenic activity. PR was not
induced by SP given alone. More recent work demonstrates more clearly
that SP are not mammotrophic or uterotrophic when given alone at doses
that produce beneficial effects on the cardiovascular system. Adult
surgically postmenopausal female macaques (Macaca
fascicularis) were treated continuously for 36 mo with either
conjugated estrogens (CE), isoflavone-enriched soy isolate (SP) or
neither. Doses were equivalent to 1.25 mg/(woman · d) of CE and 130
mg/(woman · d) of SP. Uterine and breast epithelial Ki67 staining
revealed marked epithelial cell proliferation induced by CE but not SP.
Inhibition of atherosclerosis was similar in both CE- and
SP-treated macaques. Within the group treated with SP alone, the
concentration of equol was inversely correlated with that of estrone,
possibly reflecting inhibition of the aromatization of adrenal
androgens. Furthermore, SP-fed macaques that required antibiotic
treatment (generally for diarrheal diseases) during the course of the
study had significantly lower total serum isoflavone concentrations,
reflecting primarily a lowering of serum equol. Therefore, SP may
function as selective estrogens, producing the benefits but not the
risks associated with traditional hormone replacement therapy. This
potential benefit may be modulated, however, by the interactive
presence of other sex steroids and may be attenuated by antibiotic
use.
Soybean Components Inhibit Orthotopic Growth of Human Prostate Cancer LNCaP Cells in SCID Mice. J.-R. Zhou, Y. Zhong and G. L. Blackburn. Nutrition/Metabolism Laboratory, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA.
The objective of this study was to apply an animal model for orthotopic growth and metastasis of prostate cancer to test the hypothesis that soybeans contain bioactive components that inhibit prostate cancer progression. Male severe combined immune deficient (SCID) mice were inoculated intraprostatically with 2 x 106 LNCaP cells and randomly distributed into four dietary groups (n = 8) as follows: AIN-76 as the control, AIN-76 with casein replaced by soy isoflavone–depleted soy protein, AIN-76 with the addition of Novasoy isoflavone concentrate at 0.5% of the diet, and AIN-76 with the addition of genistein extracted from soybeans at 0.15% of the diet providing the same amount of genistein as that in the isoflavone concentrate. Body weight and food intake were quantitated. Ten weeks after inoculation, the study was terminated, primary tumors were weighed and lymph node metastases were observed. Dietary soy products did not significantly alter the food intake or final body weight. Tumor weights from mice treated with diets containing isoflavone-depleted soy protein, 0.5% of Novasoy isoflavone concentrate and 0.15% of soy genistein were reduced significantly by 49 (P < 0.05), 59 (P < 0.05) and 64% (P < 0.01) compared with controls, respectively. Tumor weight was significantly correlated with serum prostate–specific antigen (R2 = 0.58, P < 0.0001), which was also reduced by dietary treatment. Mice treated with soybean components also had 40–50% fewer lymph node macrometastases than did controls, although the differences were not significant (P > 0.05). Dietary soybean components had no significant effects on serum insulin-like growth factor 1 or testosterone levels. Orthotopic growth and metastasis of prostate tumor in the SCID mouse provides a clinically relevant animal model for studying the effects of dietary treatment on growth and metastasis of prostate cancer. Soy products warrant further investigation in prostate cancer treatment and prevention.
Effect of Two Soy Preparations on Prostate-Specific Antigen Levels in Patients with Prostate Cancer and the Correlation of Prostate-Specific Antigen Changes with Plasma Genistein. Israel Barken, I. E. Baranov* and Jack Geller.* Prostate Cancer Research and Education Foundation, San Diego, CA and *AntiCancer Inc., San Diego, CA.
The purposes of this study were twofold: to compare the effectiveness of two soy preparations, a fermented soy drink and a soy isoflavones concentrate, against a control as a treatment for prostate cancer and to find the correlation between responses with prostate-specific antigen (PSA) slopes and levels of genistein in the serum. Clinically stable patients (n = 30) with prostate cancer, stages B, C or D1, previously treated or untreated, were entered into a 6-mo clinical trial. Ten patients received 250 mL/d of a fermented soy drink (Ecogen, EcoNeugenics, San Rafael, CA) in an open study. The other 20 patients were entered into a double-blind, randomized, placebo-controlled trial and received either 1000 mg of isoflavones or placebo in a capsule form. Blood levels of genistein were determined in all patients at baseline and at 6 mo. The prostate-specific antigen (PSA) levels of the patients were measured at the beginning of the trial and monthly. Patients were seen monthly by the investigators. The average PSA level at the end of the 6-mo trial increased by 0.32 ng/mL in the fermented soy drink group, 1.7 ng/mL in the isoflavones group, and 2.3 ng/mL in the placebo group. The smaller increase in PSA in the fermented soy group compared with the placebo group was the only significant difference noted between the groups (P = 0.032). Plasma genistein levels did not correlate with the PSA responses in the patients. Patients who were untreated during the year before the study and for whom there were three or more PSA values available were used as their own controls by comparing the slope of the PSA trend during the year before the study with the slope of PSA trend during the 6 mo of treatment. The least mean square deviation method was used to establish the PSA slopes. This analysis showed a decreasing slope for six of seven patients treated with the fermented soy. In contrast, five of six patients in the placebo group showed an increasing PSA slope during the 6 mo of the study compared with the previous year. There were inadequate numbers for analysis in the isoflavones group. The fermented soy drink appeared to slow the rise in PSA compared with placebo during a 6-mo trial. Calculations of directional changes in the slope for PSA showed downward sloping during treatment with the fermented soy drink and upward sloping during treatment with the placebo. Because of the discrepancy between the responses in PSA slopes and the level of genistein in the serum, we question the hypothesis that genistein is the effective agent in soy affecting the PSA slopes. Additional research is warranted to determine the mechanism at work in these findings.
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Session 4: Hormonal effects. Premenopausal and postmenopausal studies |
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TOPSession 1: Isoflavone...Session 2: Osteoporosis. In...Session 3: Cancer. In...Session 4: Hormonal effects....Session 5: Coronary heart...Session 6: Research identifying...Session 7: Plenary session....Session 8: Plenary session....Session 9: Panel discussion....REFERENCES |
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Our investigation explored the relationship between dietary soy and
mammographic patterns, which appear to be a marker of breast cancer
risk. In a cross-sectional design, we recruited 514 women with
Caucasian, Chinese, Filipino, Japanese and Native Hawaiian ancestry who
had a normal mammogram. Soy intake was assessed with a
food-frequency questionnaire and validated by urinary isoflavone
excretion as measured by HPLC. We used a computerized method to
determine the total and the dense area of the breast. ANOVA and
multiple linear regression were applied for statistical analysis.
Japanese and Chinese women consumed significantly more soy protein than
did Caucasian women (4.9 and 4.3 g vs. 2.3 g, respectively).
Self-reported soy protein intake was strongly related to urinary
isoflavone excretion (rS = 0.61,
P < 0.0001). The dense area of the breast was 15%
smaller in Chinese and Japanese than in Caucasian women, but, because
of the smaller breast size, the percentage of the breast occupied by
dense tissue was higher among Chinese and Japanese than among Caucasian
women. Although we did not observe a relationship between soy intake
and the size of the dense areas, we found a weak association between
soy protein intake (
5 vs. <5 g/d) and percentage of mammographic
densities after adjusting for ethnicity, body mass index, age,
menopausal status, percentage calories from fat and parity. However,
the size of the nondense areas (i.e., the fatty part of the breast) was
inversely related to soy intake after adjustment for ethnicity, body
mass index, age, caloric intake, percentage calories from fat, age at
menarche and parity. These results suggest that dietary soy consumption
may be associated with the growth of the female breast and risk of
developing breast cancer. The lack of a lifetime history of soy intake
and cross-sectional design limited our study’s ability to
establish causal relations. We are currently conducting a randomized
intervention in premenopausal women to investigate the effect of an
isoflavone supplement on endogenous estrogen levels and mammographic
densities.
Effect of Phytoestrogens from Soy Foods on Ovarian Function in Premenopausal Women. Anna H. Wu, Frank Stanczyk, Suzanne Hendrich, Patricia Murphy, Chunying Zhang, Peggy Wan and Malcolm C. Pike. University of Southern California, Department of Preventive Medicine, Los Angeles, CA.
There is suggestive epidemiologic evidence that high soy intake may protect against breast cancer. The mechanisms by which intake of soy may influence risk of breast cancer are not known. A predominant hypothesis focuses on the potential effects of soy on hormone production and metabolism. The main objective of this soy intervention study was to investigate the relationship between ovarian function in healthy cycling premenopausal women and daily intake of Asian soy foods (tofu, soy milk and soybean peas). The women’s hormone levels were compared during the soy intervention with their levels before and after intervention. Twenty women completed this 7-mo study, which consisted of 2 mo of baseline assessment, 3 mo of soyfood supplementation and 2 mo of follow-up assessment. During the entire study period, subjects provided morning urine specimens and blood specimens during specified days of their menstrual cycles. In addition, subjects completed a daily log to record information on menstrual cycle, alcohol intake, exercise pattern, and the amount and types of soy food eaten (during the intervention months only). Soy intervention was associated with a significant reduction in serum luteal estradiol level, but there were no significant changes in follicular phase estradiol, follicular or luteal phase progesterone, sex hormone–binding globulin or menstrual cycle length. Implications of these findings will be discussed.
Reproductive Endocrine Effects of a Soya Diet in Premenopausal Women. Lee-Jane W. Lu, Karl E. Anderson and Manubai Nagamani. Departments of Preventive Medicine and Community Health and Obstetrics and Gynecology, The University of Texas Medical Branch, Galveston, TX.
Soybean (soya) consumption may reduce the risk of breast cancer
by lowering, in part, the circulating levels of ovarian steroids. To
gain a better understanding of the oncoprotective effects of soya
diets, female subjects on a metabolic unit ingested, for one complete
menstrual cycle, a diet of known composition calculated to match their
usual energy intakes. This included a daily 36-oz portion of soymilk
containing one dose of 5–200 mg isoflavones. The results showed that
over the full cycle, a soya diet containing 113–207 mg/d of
total isoflavones decreased serum levels of 17ß-estradiol by 25%
(P < 0.01), estrone-sulfate by 40%
(P < 0.0001) and progesterone levels by 45%
(P < 0.0001) compared with levels when
subjects consumed their usual home diets. There were no apparent
effects on luteinizing hormone or follicle-stimulating hormones.
Urinary levels of 2-hydroxyestrone were decreased 40% by a soya diet
containing >100 mg/d of isoflavones compared with a soya diet
containing 5 mg/d of isoflavones (P = 0.01), but no
effect on 16-hydroxyestrone was detected. Isoflavones were excreted
in urine and detected in sera of all subjects while they were consuming
isoflavone-containing diets but with substantial variation. These
data suggest that a soya diet can reduce circulating levels of ovarian
steroid hormones and that the inhibition of ovarian steroid synthesis
does not appear to be mediated by gonadotropins because soya feeding in
this study did not reduce the levels of gonadotropins. The decrease in
ovarian steroids may result in part from an increased oxidative
metabolism of 17ß-estradiol to 2-hydroxyestrone. Because ovarian
steroids (17ß-estradiol, progesterone and estrone sulfate) regulate
breast cell proliferation, these reductions may lead to lower risk for
breast cancer. 17ß-Estradiol is metabolized to 2-hydroxy-,
4-hydroxy-, and 16-hydroxy-estrone or estradiol. 2-Hydroxyestrone
inhibits cell proliferation, tubulin formation and angiogenesis and is
postulated to be an anticarcinogenic metabolite of 17ß-estradiol. In
contrast, 4-hydroxy- and 16-hydroxy-estrone are genotoxic and
carcinogenic. Thus, increased excretion of 2-hydroxyestrone after soya
isoflavone ingestion may be an additional mechanism by which soya
consumption reduces breast cancer risk. The decreases observed in
ovarian steroid levels after soya consumption are consistent with
epidemiologic data suggesting that Asians consuming a diet rich in soya
have lower levels of ovarian steroids and a lower incidence of breast
cancer than do populations consuming diets that contain less soya.
[Supported by USPHS CA65628, CA56273, CA45181, NIH NCRR GCRC MO1
RR00073, and AICR 95B119.]
Dietary Soy Supplement and Menopausal Hormones and Hot Flashes. Margo Woods, Donna Speigelman, Ellen Hertzmark, Ann LaBrode, and Christopher Longcope. Tufts University, Boston, MA.
A 7-mo, double-blind, crossover study was designed to determine whether a soy supplement containing 45 mg/d of phytoestrogen would decrease the number and intensity of hot flashes and night sweats in menopausal women (ages 45–58 y) reporting more than five hot flashes daily. An alternative to hormone replacement therapy (HRT) for the alleviation of hot flashes would be welcomed by the medical community and by many patients who do not choose to use HRT. Eighty-five women completed the protocol that started with 2 wk of baseline data, recording menopausal symptoms and collecting blood for the determination of baseline hormones and gonadotrophins. Women were randomly assigned to receive a soy or placebo supplement for 12 wk. A daily record of symptoms was kept and a blood sample was obtained at the end of wk 12. One month of washout was followed by the alternative treatment for a second 12 wk and repeated data collection. Serum levels of phytoestrogens were determined in a subsample of the women (n = 7) to determine the serum levels achieved with consumption of the soy supplement to compare with levels reported in Asian women. A control group of women (n = 45) who reported fewer than one hot flash daily was recruited for a baseline period of 2 wk to obtain data on hot flashes, hormone levels and gonadotrophins in women in the same age category and stage of menopause who were experiencing a low level of hot-flash symptoms. A 22 and 26% reduction in the frequency of hot flashes was reported during both the soy- and placebo-supplemented phases of the study, respectively, compared with baseline, but no difference was observed in the reported number or intensity of the hot flashes when the soy and placebo phases were compared. Endogenous hormones, however, were altered, with a significant decrease in serum estradiol in the soy phase compared with baseline (P = 0.003) and placebo (P = 0.03). Decreases in sex hormone–binding globulin (P = 0.0001) and increases in follicle-stimulating hormone and luteinizing hormone (P = 0.03 for both) compared with baseline were also seen. Levels of serum phytoestrogen achieved in the women receiving the soy supplement were comparable and probably higher than levels seen in the Asian population. A significant inverse association was observed between levels of estrone sulfate and the number of hot flashes reported (P = 0.02). [Supported by U.S. Army Medical Research & Development DAMD-1794C4120.]
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Session 5: Coronary heart disease |
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TOPSession 1: Isoflavone...Session 2: Osteoporosis. In...Session 3: Cancer. In...Session 4: Hormonal effects....Session 5: Coronary heart...Session 6: Research identifying...Session 7: Plenary session....Session 8: Plenary session....Session 9: Panel discussion....REFERENCES |
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Previous studies established that soy protein has a cholesterol-lowering effect, but many questions remain. For example, does soy protein affect the lipid profile of men and women in a similar matter and are the isoflavones responsible for this lipid effect? Numerous concerns about soy protein have also been raised. We performed three studies to examine these questions in some detail. Study 1 involved 54 postmenopausal women with a total cholesterol level (TC) >5.5 mmol/L after a 4-wk cholesterol-lowering diet. Subjects were randomly assigned to receive normal soy protein (ISP+) containing 65 mg isoflavone or soy protein with isoflavones alcohol-extracted (ISP-) for 12 wk. Subjects were reassessed 4 wk after (off phase) the end of the 12-wk treatment phase. The following were measured at intervals: TC, triglyceride (TG), HDL, LDL, luteinizing hormone (LH), follicle-stimulating hormone (FSH), sex hormone–binding globulin (SHBG), thyroid-stimulating hormone (TSH), bone markers (bALP, osteocalcin, and urinary deoxypyridinoline), as well as glucose and insulin response to a glucose load. The mean age of subjects was 57 y; mean baseline cholesterol was 7.3 mmol/L. There was no weight change over the study period. There were five dropouts, leaving 49 for analysis. The mean lipid reductions were 4.3% for TC and 6.1% for LDL. No difference was seen between ISP+ and ISP-, implying that some component other than isoflavones was responsible for the lipid-lowering effect. No effect was seen on glucose metabolism, TSH, bone markers (apart from a mild effect on urinary deoxypyridinoline), FSH or Greene menopause scores. A mild but significant effect was seen for ISP+ on serum levels of LH, and a significant reduction was seen for SHBG in the ISP+ group. Interestingly the levels of SHBG returned to normal during the off phase. Study 2 was an uncontrolled study of 27 men with a TC level >5.5 mmol/L after a 4-wk cholesterol-lowering diet. During the 12-wk study period, all subjects were given 28 g soy protein containing 65 mg isoflavone. Subjects were reassessed 4 wk after (off phase) the end of the 12-wk treatment phase. The following were measured: lipid profile, LH, FSH, SHBG, TSH and androgen profile. The mean age of subjects was 52 y; mean baseline TC was 6.8 mmol/L. The average increase in HDL cholesterol was 9.5%; this value returned to baseline during the off phase. There was no effect on TSH, testosterone, androstenedione, LH or FSH. As was seen in the study with women, there was a >10% decrease in SHBG and a nonsignificant increase in DHEA (P = 0.06). Study 3 involved women using estrogen patches for a total of 12 wk, but during the middle 4 wk they were also given soy protein to see whether this interfered with their estrogen levels. The average estradiol level before soy was 200 pmol/L and during soy was 212 pmol/L. Thus no effect was seen. In conclusion, these three studies demonstrated that men and women appear to have a different response to soy protein in terms of their lipid profile. In the studies both with men and women, a significant reduction in SHBG was demonstrated. This is a novel finding because previous studies using soy and cereal typically showed an elevation in SHBG.
Effect of Soy Protein and Phytoestrogen Intake on Plasma Lipids in Hypercholesterolemic Postmenopausal Women. Christopher D. Gardner, Kathryn A. Newell and William L. Haskell. Stanford University, Palo Alto, CA.
Phytoestrogens derived from soybeans may have a hypocholesterolemic
effect. However, evidence to substantiate this claim is limited. We
conducted a randomized, double-blind, placebo-controlled, clinical
trial, with a parallel design. Ninety-four postmenopausal,
hypercholesterolemic (LDL cholesterol 152 ± 23 mg/dL, mean
± SD, range 130–190 mg/dL) women were randomly
assigned to receive daily a powdered protein supplement with 40 g
protein composed of milk protein (MILK), soy protein with trace
phytoestrogen (SOY-trace) or soy protein with 145 mg phytoestrogen
(isoflavone) (SOY-Iso145). A 1-mo run-in with milk protein period
was followed by a 3-mo treatment period. The outcomes measured were
plasma lipoprotein cholesterol and triglycerides. There were no
significant differences between MILK and either SOY-trace or
SOY-Iso145 (Table 1). LDL cholesterol decreased significantly more for the SOY-Iso145
group than for the SOY-trace group. These findings do not support a
cholesterol-lowering effect of soy protein, with or without
phytoestrogen, relative to milk in postmenopausal, hypercholesterolemic
women. Phytoestrogen intake may be warranted for other health outcomes.
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and
ER- ß in Modulating Reactivity of Arteries in
Response to Mammalian and Soy Phytoestrogens. J. Koudy Williams,
Jeffrey Hodgin,* Oliver Smithies* and Kenneth
Korach. Department of Pathology, Wake Forest
University School of Medicine, Winston-Salem, NC; *The University
of North Carolina, Chapel Hill, NC; and National
Institute of Environmental Health Sciences, Research Triangle Park, NC.
Both mammalian and soy phytoestrogens modulate vascular reactivity.
Arteries contain both estrogen receptor- (ER-) and ER-ß;
however, their role in mediating the effects of estrogens on vascular
function is unknown. Mice with targeted gene disruption of ER- or
ER-ß [and their wild-type (WT) counterparts] were used in this
experiment. The aorta of the mice was removed immediately after death,
cut into aortic rings and incubated in nutrient solution (Dulbecco’s +
5% fetal calf serum) in an oxygenated, warmed bath for 24 h. The
nutrient solution contained the vehicle dimethyl sulfoxide, 10 nm
17ß-estradiol (E2) or 10 nm genistein. The rings were
then suspended in a vessel bath for measurement of isometric tension in
response to the addition of log doses of phenylephrine or 10
µmol L-NAME/L. At the end of the studies, the aortic
rings were analyzed by Western analysis for expression of eNOS protein.
Results indicate that coincubation of arterial rings with
E2 or genistein in WT mice resulted in a 35% reduction in
constriction to phenylephrine (10-6 mol/L)
(P < 0.05 vs. vehicle). This effect was diminished
(P > 0.05 vs. control) by removal of the endothelium or
coincubation of the vessels with the transcription blocker
cyclohexamide. These effects were observed in ER- knockout mice but
not in ER-ß knockout mice. Constriction to L-NAME (a measure of
endogenous production of nitric oxide) was 64% greater in WT and
ER- knockout mice in response to E2 (P <
0.05) but not genistein. The effect of E2 on constriction
to L-NAME was completely inhibited in the ER-ß knockout mice.
Treatment of rings with E2, but not genistein, increased
arterial eNOS protein levels. It is concluded that ER-ß—and to a
lesser extent ER-—mediates vascular reactivity of arteries in
response to estrogens but that the mechanisms by which E2
(upregulation of eNOS) and gensitein (unknown at this time) affect
these responses may differ.
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Session 6: Research identifying the hypocholesterolemic components of soy |
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TOPSession 1: Isoflavone...Session 2: Osteoporosis. In...Session 3: Cancer. In...Session 4: Hormonal effects....Session 5: Coronary heart...Session 6: Research identifying...Session 7: Plenary session....Session 8: Plenary session....Session 9: Panel discussion....REFERENCES |
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Some evidence that isoflavones are the hypocholesterolemic
components of soy protein comes from our studies of cynomolgus monkeys
fed diets containing moderate amounts of cholesterol (~0.3 mg/kcal)
with the source of dietary protein being either alcohol-extracted
(Soy–) or nonextracted soy protein isolate (Soy+). Each group included
56 surgically postmenopausal monkeys. The monkkeys fed Soy+ had lower
plasma concentrations of LDL and VLDL cholesterol (251 vs. 316 mg/dL,
P = 0.0003) and higher concentrations of HDL
cholesterol (72 vs. 62 mg/dL, P = 0.004)(Anthony et al. 1998
). Researchers at our center (Crouse et al. 1999
) have even
stronger evidence with human patients that shows no significant effect
of Soy- and increasing degrees of reduction in LDL cholesterol with
increasing concentrations of isoflavones in Soy+ treatments. Other
evidence arising from the two observations has led some to conclude
that the isoflavones are not the hypocholesterolemic components.
Greaves et al. (1999)
in our group found no effect on either LDL or HDL
cholesterol of adding purified soy isoflavones to a casein and
lactalbumin diet. Similarly, Nestel et al. (1997)
found no effect on
either LDL or HDL cholesterol of giving postmenopausal women purified
soy isoflavone pills. Our current working hypothesis is that some
amount of soy protein (or a nonisoflavone component of the peptide) is
necessary for the isoflavones to be hypocholesterolemic. The
isoflavones up-regulate the LDL receptor, increasing bile acid
excretion, and without some component of the soy to bind the bile
acids, they are reabsorbed and there is no negative sterol balance. The
high-molecular-weight component of the soy protein may be the key
modulator because it is more than twice as effective as the whole
peptide in binding both bile acids and neutral steroids (Sugano et al. 1990
).
Are Proteins the Hypocholesterolemic Components of Soy Protein? Cesare R. Sirtori. Center E. Grossi Paoletti, Institute of Pharmacological Sciences, University of Milano, Italy.
Clinical studies in the past 25 years as well as a meta-analysis
(Anderson et al. 1995
) established beyond doubt that changing from
dietary animal to vegetable proteins (generally soy) lowers cholesterol
in humans. Cholesterol reduction is maximal in patients with elevated
cholesterol and minimal in normolipidemic individuals, suggesting that
only individuals with altered cholesterol and LDL handling should be
intensely sensitive. Whether proteins or additional components (e.g.,
isoflavones) may be the responsible moiety can be answered by clinical
studies. Since 1979, all major Italian studies, that is, most
investigations in hyperlipidemic patients quoted in the Anderson
meta-analysis, have used products such as Cholsoy, Croksoy, and
others (Descovich et al. 1980), all characterized by no or negligible
isoflavone content (Murphy et al. 1997). Recently, we compared the
effects of the dietary addition of a protein-rich soy milk (added
with soy isolate to give a protein content of 7%) that contained
significant amounts of isoflavones with the effects of cow’s milk in a
double-blind study in patients with either poor response or side
effects to statins. The addition of soy led to a modest but significant
LDL reduction (Sirtori et al. 1999
). The isoflavone-rich product
was less effective than isoflavone-free products used in earlier
studies. In a more recent study on type II hyperlipoproteinemic
patients, the addition of a similar isoflavone-rich product that
had a protein content <5% proved ineffective. In vitro studies in our
laboratory attempted to duplicate the clinical findings with soy. In
HepG2 cells, soy protein, particularly the 7S globulin and maximally
the + ' components, increases LDL receptor activity
significantly. A soy mutant that is free of ' (Keburi) does not
increase LDL receptor activity (Lovati et al. 1998) nor does the
addition of isoflavones to this same system, thus suggesting a modest
role, if any, of isoflavones in plasma cholesterol reduction.
Influence of Specific Amino Acids on Experimental Atherosclerosis in Rabbits. David Kritchevsky and Susanne K. Czarnecki.* Wistar Institute, Philadelphia, PA and *Department of Chemistry, Chestnut Hill College, Philadelphia, PA.
Rabbits fed casein or soy protein as the sole source of protein show distinct differences in atherogenic response. Casein is significantly more cholesterolemic and atherogenic. We have hypothesized that the differences in observed effects could be due to the ratio of lysine to arginine (L:A) in the specific protein. In general, proteins of animal origin have a higher L:A than do those of plant origin. The L:A of casein is about twice that of soy protein. Rabbits fed a semipurified diet containing 25% casein exhibit higher cholesterol levels and much more severe atherosclerosis than do those fed diets containing 25% soy protein. When rabbits were fed a diet in which the ratio of animal protein (casein or beef) to soy protein was 1:1, their serum cholesterol and severity of atherosclerosis were similar to those of rabbits fed soy protein. The 1:1 animal:soy diet had reduced the L:A. A diet containing casein plus enough arginine to give an L:A resembling that of soy protein leads to an incidence of atherosclerosis resembling that seen in soy-fed rabbits. Addition of lysine to soy protein raises serum cholesterol levels and increases severity of atherosclerosis. The single amino acid additions also alter lipoprotein patterns as well as patterns of cholesterol turnover. The data indicate the outcome possibilities that can be realized by simple changes in amino acid ratios of proteins. They also suggest that L:A may be an important indicator of dietary protein effects on lipid metabolism.
Are Saponins and/or Other Soybean Components Responsible for Hypocholesterolemic Effects of Soybean Foods? Suzanne Hendrich, Tong T. Song, Sun-Ok Lee and Patricia A. Murphy. Department of Food Science and Human Nutrition, Iowa State University, Ames, IA.
Results from studies in the hypercholesterolemic hamster model as well as a brief review of the literature with respect to saponins as hypocholesterolemic agents will be presented. Sixty male and 60 female Golden Syrian hamsters were randomly assigned to six different groups (n = 10) and fed for 10 wk. The experimental diets contained 0.1% cholesterol and 10% coconut oil to produce hypercholesterolemia. The six treatments were casein control, isolated soy protein (ISP), ISP-, daidzein, soy germ (SoyLife) and soy-germ extract. Diets provided a total isoflavone content of 1.3 mmol/kg diet (except for casein and ISP- groups). The ISP- diet contained 0.013 mmol isoflavone/kg diet. All hamsters fed ISP, ISP-, daidzein, soy germ and soy-germ extract had significantly lower plasma total cholesterol (16–28% lower), LDL cholesterol (15–50% lower) and ratios of LDL to HDL cholesterol than did the control group (P < 0.01). For male hamsters, there were no differences among treatments in plasma HDL concentrations. For females, the ISP and ISP- groups had significantly higher HDL levels (20–30% higher) (P < 0.01) than did the casein groups. There were no differences in triglyceride levels among treatments for both sexes. These data support the cholesterol-lowering effects in hamsters of soy protein with or without isoflavones, the soy isoflavone daidzein and soy germ and suggest that a plateau of maximal hypocholesterolemia was achieved by all of these treatments. A hamster study of similar design is planned to compare effects of the following five treatments vs. a casein control: ISP, ISP-, ISP extract containing both isoflavones and saponins, purified daidzein and genistein, and purified saponins in amounts comparable to their amounts in intact ISP.
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Session 7: Plenary session. Hypertension, renal disease and LDL oxidation |
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TOPSession 1: Isoflavone...Session 2: Osteoporosis. In...Session 3: Cancer. In...Session 4: Hormonal effects....Session 5: Coronary heart...Session 6: Research identifying...Session 7: Plenary session....Session 8: Plenary session....Session 9: Panel discussion....REFERENCES |
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Recent evidence indicates that a diet containing soy isoflavones can
have beneficial effects on the cardiovascular system, including
improving the plasma lipid profile. Effects on blood pressure and
vascular reactivity, however, are controversial. We examined the
effects of a soy diet on blood pressure and skin blood flow reactivity
in men and postmenopausal women with moderate levels of hypertension.
Subjects were admitted to the study when they exhibited an average
diastolic blood pressure of at least 90 mm Hg over a 12-h period after
they had stopped taking antihypertensive medications for at least 2 wk.
The protocol was a randomized, double-blind, crossover design with
a 2- to 4-wk run-in period, a 4-wk treatment period in which
subjects ate soy food either with (Soy+) or without (Soy-)
isoflavones, a 2-wk washout period and a second 4-wk treatment period
with the other soy treatment. Women ate soy muffins daily that
contained 38 g soy protein (73 mg total isoflavone, 43 mg aglycone
isoflavone). Men consumed soy muffins and drinks daily with 35 g
soy protein (162 mg total isoflavone, 95 mg aglycone isoflavone). Blood
pressure measurements were made weekly for 12 h/d. In addition, skin
blood flow responses to a 3-min occlusion of the arm were routinely
measured with a laser Doppler flow monitor. Systolic, diastolic and
mean arterial blood pressures, heart rate and pulse pressure are
presented in Table 1 (means ± SEM). After occlusion of the arm for 3
min, skin blood flow increased transiently and returned to
near-normal levels within 3 min but rose initially to a higher
level during Soy+ treatment. Although Soy+ treatment may alter some
vascular responses, our findings indicate that a short-term diet
containing soy isoflavones has no overall effect on blood pressure in
moderately hypertensive subjects during a 1-mo diet period. [Supported
by a grant from the South Dakota Soybean Research and Promotion
Council.]
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and B. P.
McGrath. Cardiovascular Research Group, Department of Medicine,
Monash Medical Centre, Monash University, Clayton, VIC, Australia;
*International Health and Development Unit, Monash University, The
Alfred Hospital, Prahran, VIC, Australia; and The Jean
Hailes Foundation, Clayton, VIC, Australia.The aim of this study was to examine the effects of dietary supplementation with soy protein (containing 118 mg of isoflavones, i.e., daidzein, genistein, glycitein, their respective glycosides and glycoside esters) on lipids, blood pressure and cardiovascular function in humans. In this double-blind, randomized study, 110 men and 110 women received soy protein or matching casein placebo for 3 mo. Variables assessed included blood pressure (BP), lipid profiles [triglycerides (TG), LDL, HDL, and total cholesterol] and measures of vascular function [systemic arterial compliance (SAC) and pulse wave velocity (PWV)]. Combined data corrected for baseline values were analyzed by MANOVA and reported as change ± SEM. Baseline measurements were similar in the two groups. After the intervention, LDL, HDL, total cholesterol and PWV decreased, whereas SAC increased significantly in both groups; however, no advantage of soy protein therapy was noted. A significant improvement was noted in the soy protein group compared with the placebo group in both TG (-0.29 ± 0.05 vs. -0.01 ± 0.05 mmol/L, P = 0.003) and the LDL-HDL ratio (-0.33 ± 0.1 vs. 0.04 ± 0.1mmol/L, P = 0.03). Mean BP (-5.5 ± 1 vs. -0.9 ± 1 mm Hg, P = 0.004), systolic BP (-7.5 ± 1.2 vs. -3.6 ± 1.1 mm Hg, P = 0.02) and diastolic BP (-4.3 ± 0.8 vs. -1.9 ± 0.7 mm Hg, P = 0.03) all fell to a greater extent in the soy protein group than in the placebo group. These findings persisted after correction for age and sex. Dietary supplementation with soy-derived phytoestrogens improves lipid profile and blood pressure but not measures of vascular function in both men and women. This may offer a therapeutic dietary intervention with minimal side effects to reduce cardiovascular disease, especially in men for whom estrogen therapy is inappropriate. Further research is required in high risk hypertensive and hyperlipidemic populations.
Soy Protein and Protection from Diabetic Kidney Disease. James W. Anderson, Tammy J. Hanna and Paolo Fanti. University of Kentucky, VA Medical Center, Lexington, KY.
Eighteen million Americans have diabetes mellitus. Nearly one third of those with diabetes develop renal disease. Diabetic nephropathy is a major contributor to death in persons with diabetes, primarily from end-stage renal disease and cardiovascular disease. Since 1836, dietary protein restriction has been recommended as a therapeutic intervention to prevent diabetic nephropathy. Recently, both animal and human trials found that in addition to protein restriction, modifications in the type of protein consumed have a favorable effect on renal health. Two short-term and two long-term clinical trials examined the effects of soy protein compared with animal protein intake on proteinuria and the progression of renal disease in diabetic subjects. These preliminary trials found that soy protein should have beneficial effects on diabetes patients with nephropathy characterized by proteinuria. In addition, the size of postprandial changes in renal blood flow and glomerular filtration rate induced by various protein sources were found to be greatest for beef, followed by poultry, fish and plant proteins. Indeed, research to date supports the notion that not all proteins are created equal. The mechanisms by which soy protein may exert renal-protective benefits have yet to be elucidated. However, from preliminary in vitro and in vivo evidence, we postulate that the effects are related to the following: 1) the unique amino acid composition of soy affecting renal blood vessel physiology by inducing much less glucagon- and prostaglandin E2–mediated vasodilation of the afferent circulation and renin-angiotensin–mediated constriction of the efferent circulation; 2) the isoflavone component of soy having favorable effects on renal glomerular biology and hemodynamic function, primarily via genistein inhibition of tyrosine kinase activities; and 3) the lipid-lowering and antioxidant properties of soy, which may counteract the abnormal lipid profiles and the increased propensity to high levels of oxidized LDL cholesterol often seen in persons with diabetes. In conclusion, it appears from in vitro studies, animal studies and a limited number of small clinical trials that soy protein may be an effective therapy for early diabetic nephropathy. The mechanisms by which soy modulates renal function require further study, but preliminary potential mechanisms are hypothesized.
Effects of Soy, as Tofu, vs. Meat on Coronary Heart Disease Risk Factors. E. L. Ashton, J. E. Foster, F. S. Dalais* and M. J. Ball. School of Health Sciences, Deakin University, Malvern, VIC, Australia and *International Health and Development Unit, Monash University, Alfred Hospital, Prahran, VIC, Australia.
Oxidative modification of LDL cholesterol (LDL-C) may play an important role in the pathogenesis of atherosclerosis; therefore, reducing the susceptibility of LDL to oxidation may reduce the risk of coronary heart disease (CHD). Asian populations have a lower incidence of CHD than do populations in Western countries. The Asian diet differs from a typical Western diet in many ways, but one aspect is the high consumption of soy products. This study investigated the effect of replacing lean meat with soy (as tofu) on several CHD risk factors, including the in vitro susceptibility of LDL to oxidation, measured as the lag phase of copper-induced oxidation. Male subjects (n = 42) aged 35–62 y completed a randomized crossover dietary study consisting of two 4-wk isocaloric dietary periods with a 2-wk washout period in between. The tofu diet required subjects to consume 290 g tofu daily (containing 35.7 g of soy protein). The meat diet provided an equal amount of protein from lean red meat. Butter, olive oil and lard were added to the tofu diet, and polyunsaturated fatty acid margarine was added to the meat diet so that the fatty acid contents were similar. The lag phase for LDL oxidation was significantly longer for those consuming the tofu diet than for the meat diet (P = 0.006). Total cholesterol and triglycerides were also significantly lower for those consuming the tofu diet. Fibrinogen, factor VII, apolipoprotein (a), LDL-C, and HDL2 and HDL3 were not significantly affected by tofu. Our findings indicate that soy may have an effect in reducing LDL susceptibility to oxidation and, therefore, perhaps atherosclerosis.
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Session 8: Plenary session. Cognitive function |
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TOPSession 1: Isoflavone...Session 2: Osteoporosis. In...Session 3: Cancer. In...Session 4: Hormonal effects....Session 5: Coronary heart...Session 6: Research identifying...Session 7: Plenary session....Session 8: Plenary session....Session 9: Panel discussion....REFERENCES |
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This investigation used the resources of the Honolulu Heart Program, a longitudinal study of Japanese-American men established in 1965 for research on heart disease and stroke. Questions regarding frequency of consumption of tofu and 26 other foods were asked at interviews in 1965–1967 and again in 1971–1974. Cognitive testing was done (n = 3734) and cases of dementia identified (n = 225) at the 1991–1993 examination, when participants were aged 71–93 y. Atrophy was assessed by neuroimaging (n = 574) or autopsy (n = 290). Cognitive test data were also analyzed for wives of a sample of study participants (n = 502) who had been living with the participants when their dietary interviews were done. Poor cognitive test performance in late life was associated with higher midlife tofu consumption. An independent association of similar size and direction was apparent in wives of cohort members, with the husband’s answers used as proxy for the wife’s consumption. Midlife tofu consumption was independently associated with low brain weight and with ventricular enlargement. Independent associations of more frequent midlife tofu consumption with clinically diagnosed Alzheimer’s disease and with poor cognitive functioning among nondemented subjects were demonstrated. Associations generally followed a dose-response pattern, were significant after all relevant and potentially confounding factors were controlled for and remained apparent after stratifying by age or obesity. These data suggest that regular consumption of tofu over many years in middle life may have an adverse influence on brain aging manifest as accelerated atrophy, cognitive decline and a lowering of the threshold for the clinical manifestations of Alzheimer’s disease. We speculate that these may reflect chronic suboptimal neuronal plasticity caused by isoflavone inhibition of tyrosine kinase activity, interference with estrogen-related mechanisms or both.
Tofu Consumption and Cognition in Older Japanese American
Men and Women. M. M. Rice,*
A. B. Graves,
S. M. McCurry,** L. Gibbons,J. Bowen, W. McCormickand E. B. Larson. Departments of
*Epidemiology, Medicine, **Psychosocial and Community
Health, Environmental Health, and
Neurology, University of Washington, Seattle, WA and
Department of Epidemiology and Biostatistics,
University of South Florida, Tampa, FL.
Several epidemiologic and basic neurobiological studies suggest that estrogen may have a beneficial influence on brain function. We previously found a modest beneficial association between current unopposed estrogen use (ERT) and cognitive change in female participants of the Kame Project. The purpose of this study was to determine whether the consumption of tofu, an isoflavone-rich food, influenced cognition in men and women. A secondary aim was to determine whether tofu consumption modified the association between ERT and cognition in women. Subjects were 767 women and 634 men participating in the Kame Project. The Kame Project is a longitudinal cohort study of Japanese Americans aged >65 y of age living in King County, WA. The 100-point Cognitive Abilities Screening Instrument (CASI) was measured at the baseline and 2-y follow-up examinations. Tofu consumption was categorized as low (<1/wk), moderate (1–2/wk), and high (3+/wk). All analyses were adjusted for age, education, and language spoken at the interview. In addition, baseline CASI score was adjusted for the time at which the 2-y change in CASI score was examined, and surgical menopause was adjusted for the time at which the tofu-ERT interaction was examined. Among cross-sectional results, high tofu consumers had significantly lower CASI scores than did low and moderate consumers in the cohort as a whole (P for trend = 0.03). This trend was not significant in men or in women who had never used ERT. Among women who were current ERT users, a significant negative association was observed between tofu consumption and CASI score (P for trend = 0.04). CASI scores were higher in current ERT users than women who had never used ERT for the low and moderate tofu consumers but not the high tofu consumers. Among longitudinal results, overall, most men and women showed slight improvements in their CASI score over the 2-y period. No associations were observed between tofu consumption and 2-y change in CASI score, although men and women who were modest tofu consumers showed the greatest improvements in their CASI scores. An important limitation to this study was that total isoflavone exposure was not measured in this cohort. Data from a sample of female Kame participants suggested that tofu accounted for only about half of the soy-derived isoflavones consumed by this population. The cross-sectional data suggested that high tofu consumption was associated with lower cognitive scores and opposed the beneficial association between ERT and cognitive scores in women. On the other hand, the longitudinal data suggested that tofu consumption was not associated with the rate of cognitive change in older Japanese American men and women and that tofu consumption did not appear to oppose the beneficial association between ERT and cognitive change in women.
Modulation of Neurodegeneration Markers by Dietary Soy in a Primate Model of Menopause. Helen Kim, Hongli Xia, Lin Li and John Gewin. Department of Pharmacology and Toxicology, University of Alabama at Birmingham, Birmingham, AL.
Epidemiologic studies linked postmenopausal estrogen use with a significantly lowered risk for Alzheimer’s disease in elderly women, and experiments with rats showed that estrogen replacement prevents the cognitive decline that results from ovariectomy. Experiments were carried out to determine whether soy isoflavones, which have beneficial and estrogenic actions in models of human chronic disease, have similar effects in the postmenopausal primate brain. Specifically, the capacity of either estrogen or the soy isoflavones to modulate Alzheimer’s disease–relevant phosphorylations of tau, the brain microtubule-associated protein, was assessed. Aged cynomolgus monkeys (Macaca fascicularis) were ovariectomized and segregated into groups that received diets containing whole soy protein, soy protein from which the isoflavones had been extracted, or extracted soy protein supplemented with conjugated equine estrogens (Premarin). After 36 mo, the animals were necropsied and the brains were removed and stored at –80°C. Homogenates of brain samples were analyzed by SDS-PAGE and immunoblot analysis with antibodies specific for two epitopes on tau, PHF-1 and tau-1; these are hyperphosphorylated in the tau and comprise the neurofibrillary tangles found in Alzheimer’s brain but not in normal aged human brain. Initial results indicate that these two tau phosphorylations are quantitatively suppressed in the brains of the ovariectomized animals that received unextracted soy protein but, surprisingly, not in the brains of the animals that received Premarin. These results indicate that soy protein containing the isoflavones, ingested at dietary levels, have biological effects in postmenopausal brain that may be distinct from those of the estrogens.
Soy, Estradiol and Cognitive Function: Effects on Biomarkers and Learning/Memory Performance of Estrogen-Deficient Rats. Yuanlong Pan, Mary S. Anthony and Thomas B. Clarkson. Comparative Medicine Clinical Research Center, Wake Forest University School of Medicine, Winston-Salem, NC.
Important among estrogen’s benefits for postmenopausal women is the maintenance of cognitive function (brain agonist effects). As a part of our efforts to determine the optimal role of soy phytoestrogens in postmenopausal hormone therapy, we used rat models to determine the effectiveness of soy phytoestrogens relative to 17ß-estradiol (E2) in regulating biomarkers important to cognitive function and to address whether soy phytoestrogens attenuate the beneficial effects of E2 on working memory. We examined the effects of oral E2 and soy phytoestrogen extract on the mRNA levels of choline acetyltransferase (ChAT), nerve growth factor and brain-derived neurotrophic factor (BDNF) in ovariectomized young and retired breeder rats. Within each age category, 15 bilaterally ovariectomized rats were randomly divided into three groups, i.e., untreated control, E2 and soy phytoestrogen groups, and were treated for 8 wk. Both E2 and soy phytoestrogens up-regulated ChAT and BDNF mRNA in the frontal cortex of ovariectomized retired breeder rats. In addition, E2 significantly up-regulated nerve growth factor mRNA in the hippocampus of young rats. The nerve growth factor mRNA level in the hippocampus of the soy phytoestrogen group was intermediate between the other two groups. In a separate study, we examined whether soy phytoestrogens could improve working memory and whether they would attenuate the beneficial effects of E2 in ovariectomized retired breeder rats; we used a radial-arm maze test. Bilaterally ovariectomized retired breeder rats (n = 84) were randomly divided into 12 groups (in a 3 x 4 factorial design) and were treated for 10 mo. There were four levels of E2 (0, 0.5, 1.0 and 2.0 mg/1800 kcal; women’s equivalent doses), three levels of soy with phytoestrogens (0, 72 and 144 mg/1800 kcal), and all combinations of these doses of E2 and soy phytoestrogens. Rats in groups given only E2 or soy phytoestrogens showed a dose-dependent improvement in test performance. In addition, there was no attenuation of the beneficial effects of E2 by soy phytoestrogens.
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Session 9: Panel discussion. Isoflavones: Potential toxicity? |
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TOPSession 1: Isoflavone...Session 2: Osteoporosis. In...Session 3: Cancer. In...Session 4: Hormonal effects....Session 5: Coronary heart...Session 6: Research identifying...Session 7: Plenary session....Session 8: Plenary session....Session 9: Panel discussion....REFERENCES |
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and J. C. Mirsalis.** Division of
Cancer Prevention, National Cancer Institute, Bethesda, MD; *Department
of Pharmacology, University of Illinois-Chicago, IL;
Southern Research Institute, Birmingham, A;
and **SRI International, Menlo Park, CA.The National Cancer Institute has contracted preclinical mutagenicity, teratology and subchronic toxicity studies of well-characterized isoflavone mixtures in collaboration with Protein Technologies International to support clinical investigations. The battery of mutagenicity studies included bacterial mutagenesis, the mouse micronucleus test and the mouse lymphoma test. The bacterial mutagenesis and mouse micronucleus tests were negative. The mouse lymphoma test was positive; thus, additional tests are being undertaken to characterize the dose-response relationship for topoisomerase inhibition and other effects. Range-finding and segment II teratology tests have been completed in rats and rabbits. In rats, decreased fetal weights occurred at doses of 1 g/kg body weight and increased numbers of fetuses with bent ribs (a skeletal variation) occurred at 300 mg and 1 g/kg body weight. Range-finding and subchronic 13-week oral toxicity tests have also been completed in rats and dogs. In rats, clinical chemistry changes in both sexes and adrenal cortical hyperplasia in female rats occurred at doses of 500 mg/kg body weight. The no-observed adverse effect level in the rats (the more sensitive species) was ~100 mg/kg body weight in both the teratology and subchronic studies. The proprietary mixtures were administered in these tests on the basis of genistein, and correlations across studies have been made between in vitro concentrations and plasma concentrations of free and conjugated isoflavones. Pharmacologic plasma levels in hundreds of nanograms per milliliter of free genistein and tens of micrograms per milliliter of conjugated genistein were achieved. Additional preclinical studies will be conducted as clinical studies progress.
Genistin, the Glycoside Form of Genistein, Stimulates Growth of Estrogen-Dependent Human Breast Cancer Cells In Vivo. Clinton D. Allred, Kimberly F. Allred, and William G. Helferich. Division of Nutritional Science and Department of Food Science and Human Nutrition, University of Illinois, Urbana, IL.
The phytoestrogen genistein stimulates the growth of estrogen-dependent human breast cancer (MCF-7) cells in vivo. Genistin is the glycoside form of genistein and the predominant form found in plants. It is generally believed that genistin is metabolized to genistein in the gut. However, it is unclear whether the rate of this metabolism is sufficient to produce a level of genistein capable of stimulating estrogen-dependent breast cancer cell growth. We hypothesized that dietary genistin stimulates tumor growth similar to that observed with genistein in athymic mice. To test this hypothesis, genistin or genistein was fed to athymic mice containing xenografted MCF-7 tumors. Mice were fed either genistein at 750 ppm or genistin at 1200 ppm, which provided equimolar concentrations of genistein in both diets. Tumor size was measured weekly. At completion of the study, half of the animals were killed and tumors were collected for cell proliferation analysis. Incorporation of BrdU into cellular DNA was used as an indicator of cell proliferation. Dietary genistin resulted in increased tumor growth rate and cell proliferation similar to that observed with genistein. The remaining mice were switched to diets free of genistin and genistein. Removal of the isoflavones from the diet resulted in tumor regression. In summary, genistin, like genistein, can act as an estrogen agonist to increase proliferation of estrogen-dependent breast cancer cells and, on its removal, tumors regress. [Supported by NIH grant CA77355 to WGH.]
Midgestation Intrauterine Exposure of the Human Fetus to
Dietary Isoflavones In North America: How Does This Exposure Compare
with Animal Studies in Late Gestation and Lactation That Alter
Developmental Endpoints? Claude Hughes,* **
Warren Foster,* Lawrence Platt,* Siu
Chan, Stephanie Thompson,** Slade
Hubbard,** Alison DuBose** and Lee Tyrey.**
*Center for Women’s Health and Department of Obstetrics and
Gynecology, Cedars-Sinai Medical Center, Los Angeles, CA;
Centre for Toxicology, University of
Calgary, Calgary, AB, Canada; **Department of Obstetrics and
Gynecology, Duke University Medical Center, Durham, NC.
We are conducting two studies to determine whether dietary endocrine active chemicals affect human development. In Experiment 1, our animal model experiment, we fed rat dams daily from gestation d 14 through weaning on postnatal d 21 by gavage with corn oil (controls), diethylstilbestrol (DES; low DES, 0.1 µg per dam; high DES, 1.0 µg per dam), genistein (15 mg/kg body weight), or genistein + DES (genistein at 15 mg/kg body weight and DES at 0.1 µg per dam). Groups contained 29–47 pups each. At birth, high DES, genistein or genistein + DES decreased birth body weight in both sexes. No treatment affected duration of gestation, litter size or birth anogenital distance divided by birth body weight in either sex. At weaning, only high DES reduced weaning body weight, and this affected both sexes. Compared with controls, all estrogenic treatments increased weaning anogenital distance divided by weaning body weight. At puberty, males exposed to genistein or high DES showed early puberty, whereas only females exposed to low DES showed early puberty. We concluded that maternal exposure to genistein affects birth body weight, weaning anogenital distance and pubertal onset in pups. The masculinizing effects of genistein on weaning anogenital distance in both sexes suggests that the critical interval of exposure is from postnatal d 1 to 21. In Experiment 2, our human exposure study, we measured endocrine-active compounds in amniotic fluid samples from women in Los Angeles between gestation wk 16 and 20 by using mass spectrometric methods with limits of quantitation for the pesticide metabolite 2,2-bis(p-chlorophenyl)-1,1-dichloroethane (p,p’-DDE) (0.1 ng/mL) or the isoflavones, daidzein, genistein and formononetin (0.5 ng/mL). Of 41 samples assayed for p,p’-DDE, 13 had detectable concentrations that ranged from 0.1 to 0.63 ng/mL. In 54 samples, isoflavones were measured after hydrolysis. No formononetin was detected. For total genistein plus daidzein, 11 samples were 0.5 ng/mL, 7 samples were 4.00 ng/mL (highest value was 17.38 ng/mL); the median value for all 54 samples was 1.63 ng/mL. For comparison, published mean concentrations of sex steroids in human amniotic fluid at 16–20 wk are estradiol (male 0.064 ng/mL and female 0.096 ng/mL) and testosterone (male 0.224 ng/mL and female 0.039 ng/mL). We concluded that ~30% of human fetuses are exposed to the antiandrogen p,p’-DDE at concentrations from one half to three times those of endogenous testosterone in males. About 80% of human fetuses are exposed to estrogenic isoflavones at concentrations from 20 to 180 times the concentration of endogenous estradiol in females. The human fetus is exposed to physiologically relevant levels of endocrine active chemicals during this critical period of in utero development. The effect of these exposures, if any, is unknown at this time. [Supported by USEPA #R825299-01-0.]
Genistein Toxicity from Dietary Exposure from Early Pregnancy through Puberty. D. M. Sheehan, K. B. Delclos, D. R. Doerge, W. S. Branham and R. R. Newbold.* National Center for Toxicological Research, Jefferson, AR and *National Institute for Environmental Health Sciences, Research Triangle Park, NC.
A dose range finding study was conducted by feeding genistein to Sprague-Dawley rats at 0, 5, 25, 100, 250, 625 and 1250 ppm in a soy-free diet, from gestation d 7 to postnatal d 50. Plasma levels ranged from ~10 nmol/L to 10 µmol/L. Adverse effects included hypertrophy and hyperplasia of the mammary ducts and acini in males at 25 ppm and in females at 625 ppm. Hypospermia at the head of the epididymis, inflammation of the dorsal prostate and asynchronous cycles of the uterus and vagina were observed at 625 ppm. Degeneration of the ovaries and seminiferous tubules was seen at 1250 ppm. There was a dose-dependent decrease in thyroid peroxidase activity at 25–1250 ppm. Thyroid peroxidase activity is known to be inhibited in vitro by genistein, and the prevalence of autoimmune thyroiditis was reported to be increased in children fed soy infant formula. In a separate study, genistein (1–100 µg) was injected into neonatal mice daily on postnatal d 1–5 and the mice were killed at 18 mo. Polyovular multioocyte) follicles, uterine epithelial hyperplasia, hypoplastic uteri and uterine adenocarcinoma were observed. These were similar to the lesions reported earlier to be induced by diethylstilbestrol in mice by the use of the same treatment protocol. In addition to genistein, 45 other phyto- or mycoestrogens were assayed in a uterine estrogen receptor competitive binding assay. Twenty-nine of these competed and had a wide range of relative binding affinities. The number of naturally occurring chemicals that can bind to the estrogen receptor suggests that more intense or additional effects may be expected from exposures to multiple estrogenic chemicals from plants. These findings show a significant number of adverse effects from genistein in estrogen target organs, including malignancies. Some of these effects occur at low doses, consistent with findings from other estrogens. Additionally, genistein inhibition of thyroid peroxidase suggests the possibility that this mechanism may be responsible for goiter and autoimmune thyroiditis. The results of these studies have been used to design an ongoing multigeneration study with genistein that will examine reproductive fitness, among other endpoints. [Supported by USEPA #R825299-01-0.]
Long-Term Use of Dietary Soy Protein Isolates: Lack of Apparent Toxic Effects? Thomas M. Badger, Reza Hakkak, Susan R. Shelnutt, Martin J. J. Ronis and J. Craig Rowlands. Arkansas Children’s Nutrition Center, Little Rock, AR.
Soybeans are considered a valuable source of protein and a
health-promoting food source that has been consumed throughout the
world for centuries. Soy protein isolate (SPI), first developed more
than 50 years ago, is used in formulas for infants allergic to the milk
products found in traditional milk-based formulas. Isoflavones are
one class of several so-called phytochemicals that are bound to soy
proteins in relatively high abundance. These estrogenic compounds are
absorbed as aglycones and circulate mainly as glucuronide or sulfate
conjugates within mammals. All three of these molecular forms have been
reported to possess bioactivity. The circulating and tissue isoflavone
concentrations of total isoflavones of infants fed soy-based
formulas are high (1–10 µmol/L), actually exceeding
those typically reported for adult Asian soy consumers. These
concentrations are sufficient to have both estrogen- and
nonestrogen-mediated effects inasmuch as nanomolar concentrations
are reported to transactivate estrogen-dependent reporter genes,
and many signal transduction effects occur at low micromolar
concentrations. Because soy infant formulas result in high circulating
concentrations of bioactive phytochemicals not found in breast milk or
milk-based infant formula, we are interested in potential health
consequences of soy-based formulas. We studied the SPI used in
infant formula in cell culture, multigenerational rat studies, pigs and
humans (infants and adults). In these studies, we observed no evidence
of toxicity. Our data from chronic animal studies demonstrated that
SPI-containing diets prevent incidence, multiplicity and growth of
chemically induced mammary and colon tumors, increase activities of
phase I and II detoxification systems, and support normal breeding,
gestation, lactation, maternal behavior, and growth and development.
However, too few studies have been conducted to enable us to determine
the long-term consequences of exposure to high concentrations of
estrogenic compounds during infancy, a period in which
non-soy–consuming infants would not be exposed to such endocrine
factors. Thus, even though we have not observed any toxic effects of
diets containing high levels of isoflavones, subtle effects might not
be readily obvious, or more serious effects might take years to become
apparent. In addition, because these diets have been commercially
available only since 1965, insufficient time has elapsed to determine
the effects on such disorders as breast cancer. Several important facts
are required, including target tissue isoflavone concentrations,
identification of specific bioactive isoflavones molecules, estrogen
receptor or ß levels and functionality in infants, an
understanding of target tissue isoflavone metabolism and mechanisms of
isoflavone actions. Further basic and clinical studies are required.
[Supported by the USDA-ARS Human Nutrition Research Program.]
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REFERENCES |
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TOPSession 1: Isoflavone...Session 2: Osteoporosis. In...Session 3: Cancer. In...Session 4: Hormonal effects....Session 5: Coronary heart...Session 6: Research identifying...Session 7: Plenary session....Session 8: Plenary session....Session 9: Panel discussion....REFERENCES |
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1. Strom S. S., Yamamura Y., Duphorne C. M., et al Phytoestrogen intake and prostate cancer: a case-control study using a new database. Nutr. Cancer 1999;33:20-25[Medline]
2. Heinonen O. P., Albanes D., Virtamo J., et al Prostate cancer and supplementation with alpha-tocopherol and beta-carotene: incidence and mortality in a controlled trial. J. Natl. Cancer Inst. 1998;90:444-446
3. Clark L. C., Dalkin B., Krongrad A., et al Decreased incidence of prostate cancer with selenium supplementation: results of a double-blind cancer prevention trial. Br. J. Urol. 1998;81:730-734[Medline]
4. Foth D., Cline J. M. Effects of mammalian and plant estrogens on mammary glands and uteri of macaques. Am. J. Clin. Nutr. 1998;68(suppl.):1413S-1417S[Abstract]
5. Anthony M. S., Clarkson T. B. Comparison of soy phytoestrogens and conjugated equine estrogens on atherosclerosis progression of postmenopausal monkeys. Circulation 1998;97:829(abs.)
6.
Crouse J. R., Morgan T., Terry J. G., Ellis J., Vitolins M., Burke G. L. A randomized trial comparing the effect of casein with that of soy protein containing varying amounts of isoflavones in plasma concentrations of lipids and lipoproteins. Arch. Intern. Med. 1999;159:2070-2076
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Greaves K. A., Parks J. S., Williams J. K., Wagner J. D. Intact dietary soy protein, but not adding an isoflavone-rich soy extract to casein, improves plasma lipids in ovariectomized cynomolgus monkeys. J. Nutr. 1999;129:1585-1592
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Nestel P. J., Yamashita T., Sasahara T., Pomeroy S., Dart A., Komesaroff P., Owen A., Abbey M. Soy isoflavones improve systemic arterial compliance but not plasma lipids in menopausal and perimenopausal women. Arterioscler. Thromb. Vasc. Biol. 1997;17:3392-3398
9. Sugano M., Goto S., Yamada Y., Yoshida K., Hashimoto Y., Matsuo T., Kimoto M. Cholesterol-lowering activity of various undigested fractions of soybean proteins in rats. J. Nutr. 1990;120:977-985
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Anderson J. W., Johnstone B. J., Cook-Newell M. E. Meta-analysis of the effects of soy protein intake on serum lipids. N. Engl. J. Med. 1995;333:276-282
11. Descovich, G. C., Ceredi, C., Gaddi, A., Benassi, M. S.,Mannino G., Colombo L., Cattin L., Fontana G., Senin U., Mannarino E., Caruzzo C., Bertelli E., Fragiacomo C., Noseda G., Lovati M. R., Manzoni C., Gianazza E., Sirtori C. R. Soybean protein products as regulators of liver low-density lipoprotein receptors. I. Identification of active ß-counglycinin subunits. J. Agric. Food Chem. 1998;46:2474-2480, 2481
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Sirtori C. R., Gianazza E., Manzoni C., Lovati M. R., Murphy P. A. Role of isoflavones in the cholesterol reduction by soy proteins in the clinic. Am. J. Clin. Nutr. 1997;65:166-167
13. Sirtori C. R., Pazzucconi F., Colombo L., Battistin P., Bondioli A., Descheemaeker K. Double-blind study of the addition of high-protein soya milk v. cows’ milk to the diet of patients with severe hypercholesterolaemia and resistance to or intolerance of statins. Br. J. Nutr. 1999;82:91-96[Medline]
14. Sirtori M., Sirtori C. R. Multicenter study of soybean protein diet for outpatient hypercholesterolaemic patients. Lancet 1980;ii:709-712
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