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Abstracts

LE Magazine October 2004
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Natural Estrogen

Effects of genistein on cell proliferation and cell cycle arrest in nonneoplastic human mammary epithelial cells: involvement of Cdc2, p21(waf/cip1), p27(kip1), and Cdc25C expression.
Genistein, a soy isoflavone, has been reported to inhibit the multiplication of numerous neoplastic cells, including those in the breast. However, there is limited information on the effect of genistein on nonneoplastic human breast cells. In the present studies, genistein inhibited proliferation of, and DNA synthesis in, the nonneoplastic human mammary epithelial cell line MCF-10F with an IC(50) of approximately 19-22 microM, and caused a reversible G2/M block in cell cycle progression. Genistein treatment (45 microM) increased the phosphorylation of Cdc2 by 3-fold, decreased the activity of Cdc2 by 70% after 8 hr, and by 24 hr reduced the expression of Cdc2 by 70%. In addition, genistein enhanced the expression of the cell cycle inhibitor p21(waf/cip1) by 10- to 15-fold, increased p21(waf/cip1) association with Cdc2 by 2-fold, and increased the expression of the tumor suppressor p53 by 2.8-fold. Genistein did not alter the expression of p27(kip1) significantly. Furthermore, genistein inhibited the expression of the cell cycle-associated phosphatase Cdc25C by 80%. From these results, we conclude that genistein inhibits the growth of nonneoplastic MCF-10F human breast cells by preventing the G2/M phase transition, induces the expression of the cell cycle inhibitor p21(waf/cip1) as well as its interaction with Cdc2, and inhibits the activity of Cdc2 in a phosphorylation-related manner. Down-regulation of the cell cycle-associated phosphatase Cdc25C combined with up-regulation of p21(waf/cip1) expression appear to be important mechanisms by which genistein decreases Cdc2 kinase activity and causes G2 cell cycle arrest.

Biochem Pharmacol. 2001 Apr 15;61(8):979-89

Dietary phytoestrogens and vascular function in postmenopausal women: a cross-sectional study.
OBJECTIVE: To investigate the effects of low levels of intake of phytoestrogens in Western habitual diet on vascular function. DESIGN: A cross-sectional study. SETTING: A population-based study. PARTICIPANTS: A total of 301 postmenopausal women aged 60-75 years living in The Netherlands. DETERMINANT: Dietary phytoestrogen intake as assessed using a food frequency questionnaire covering the year prior to enrollment. MAIN OUTCOME MEASURES: Blood pressure, hypertension, endothelial function and ankle brachial index. RESULTS: The median isoflavone intake was 0.2 mg in the lowest tertile and 11.4 mg in the highest tertile. Median lignan intake was 0.8 and 2.2 mg, respectively. No associations were found for higher intake of isoflavones, systolic and diastolic blood pressures, ankle-arm blood pressure index, endothelial function or hypertension. For lignans no association was found for ankle-arm blood pressure index or endothelial function, but we did observe lower systolic and diastolic blood pressures and a lower prevalence of hypertension (systolic blood pressure difference T3-T1, -11.2 mmHg, 95% confidence interval = -17.8 to -4.5, P for trend = 0.001; diastolic blood pressure difference T3-T1, -3.6 mmHg, 95% confidence interval = -7.8 to 0.6, P for trend = 0,08; and prevalence of hypertension, odds ratio T3 versus T1 = 0.41, 95% confidence interval = 0.22-0.76, P for trend over tertiles = 0.004). CONCLUSION: The results of this study suggest a protective effect of dietary lignan intake on blood pressure and hypertension, even at low levels.

J Hypertens . 2004 Jul;22(7):1381-8

Phyto-oestrogen excretion and rate of bone loss in postmenopausal women.
OBJECTIVE: The hypothesis was tested that the rate of postmenopausal bone loss is inversely associated with long-term urinary excretion of phyto-oestrogens, as a marker of habitual dietary intake. DESIGN: Secondary analysis of a 10-year follow-up study (1979 1989) among postmenopausal women in the Netherlands . SUBJECTS: From the original population of 154 women, 32 women were selected with an annual rate of radial bone loss of < or = 0.5% over the first 5 years of the study and 35 women with a rate of > or = 2.5% per year. METHODS: The isoflavonoids genistein, daidzein and equol, and the lignan enterolactone were determined by gas chromatography mass spectrometry in aggregate samples from annually collected urine samples. Cortical bone density of the radius had previously been measured annually by single-photon absorptiometry. RESULTS: Excretion of isoflavonoids did not differ between both groups, although in multivariate analysis equol excretion was weakly positively associated with rate of bone loss in the 5 years after the menopause. Enterolactone excretion was significantly higher in the group with high rate of bone loss. This positive association remained in multivariate linear regression analysis after adjustment for age, years since menopause, body mass index and intake of calcium, vegetable protein and dietary fibre. CONCLUSIONS: Enterolactone excretion is likely to be an indicator of consumption of grains and legumes; it is not clear whether the observed positive association with rate of bone loss is a causal one. Our results do not support a preventive effect of low, unsupplemented dietary intake of phyto-oestrogens on postmenopausal cortical bone loss. However, no conclusions can be drawn about effects of higher doses of phyto-oestrogens.

Eur J Clin Nutr. 1998 Nov;52(11):850-5

Soy intake and the maintenance of peak bone mass in Hong Kong Chinese women.
Our previous study on bone health among premenopausal women showed that bone mass consolidation is attained by the early 30s, and small loss of spinal bone mineral density (SBMD) occurs soon after peak bone mass attainment. Recent interest has been shown in the potential beneficial effects of phytoestrogens on bone health. However, data are lacking, particularly in Asian women. This study aims to investigate the effect of soy isoflavones intake on the maintenance of peak bone mass in a cohort of 132 women aged 30-40 years who were followed up for 3 years. Baseline measurements of SBMD (L2-L4) were obtained using dual-energy X-ray densitometry, and dietary intake of soy foods and other key nutrients, including dietary calcium, were obtained through a quantitative food frequency method. Information on body measurements; physical activity (PA), weight-bearing activity in particular; age of menarche; and number of pregnancies were obtained at baseline. Repeated measurements of SBMD were obtained yearly for a further 3 years with an average follow-up time of 38 months. Analyses were performed on 116 subjects with at least three SBMD measurements (at baseline, 3-year follow-up, and at least one measurement during follow-up). The individual SBMD regression slope was computed for each of the subjects. Soy isoflavones consumption was categorized as quartiles of intake. We observed a significant difference in the SBMD individual regression slopes between women belonging to the fourth and first soy isoflavones intake quartiles. The positive effect of soy isoflavones on SBMD remained after adjusting for age and body size (height, weight, and bone area). Multiple linear regression analysis including the other known covariates (lean body mass, PA, energy adjusted calcium, and follow-up time) showed that soy isoflavones, together with these variables, accounted for 24% of the variances of the SBMD individual regression slope. This longitudinal study shows that soy intake had a significant effect on the maintenance of SBMD in women aged 30-40 years. The effects of phytoestrogens on bone health should be explored further in a population with habitual dietary soy but low calcium intake.

J Bone Miner Res . 2001 Jul;16(7):1363-9

High dietary phytoestrogen intake is associated with higher bone mineral density in postmenopausal but not premenopausal women.
Animal studies demonstrated that phytoestrogen had a protective effect against bone loss after ovariectomy. However, data on dietary phytoestrogen intake as well as its relationship with bone mineral density (BMD) in human are not available. Six hundred fifty southern Chinese women, aged 19 to 86 yr, were recruited to determine their dietary phytoestrogen intake by a food frequency questionnaire. BMDs at the lumbar spine and hip region were measured using dual energy x-ray absorptiometry. The subjects were analyzed according to various tertiles of phytoestrogen intake. Among the postmenopausal women (n = 357), significant differences in the lumbar spine (L2-4) BMD (0.820 +/- 0.145 vs. 0.771 +/- 0.131 g/cm2, P < 0.05) and Ward's triangle BMD (0.450 +/- 0.151 vs. 0.415 +/- 0.142 g/cm2; P < 0.05) were found between the highest and lowest intake of isoflavone after adjusting for age, height, weight, years since menopause, smoking, alcohol consumption, HRT usage, and daily calcium intake. Women with the highest intake of isoflavone had significantly lower levels of serum PTH (19.38 +/- 14.61 vs. 26.56 +/- 11.19 pg/ml; P < 0.05), osteocalcin (4.95 +/- 3.61 vs. 6.69 +/- 5.05 mg/liter; P = 0.05), and urinary N-telopeptide (34.18 +/- 25.31 vs. 49.66 +/- 41.00 nmol bone collagen equivalents/mmol creatinine; P < 0.05) when compared with those with the lowest intake of isoflavone. No association between dietary phytoestrogen intake and BMDs was seen in the premenopausal women with high endogenous E (n = 293). In conclusion, postmenopausal women with habitually high intake of dietary isoflavone are associated with higher BMD values at both the spine and hip region. Customarily high isoflavone intake may help to reverse the state of secondary hyperparathyroidism associated with E withdrawal and hence lower the rate of bone turnover in postmenopausal women.

J Clin Endocrinol Metab. 2001 Nov;86(11):5217-21

Effects of genistein and hormone-replacement therapy on bone loss in early postmenopausal women: a randomized double-blind placebo-controlled study.
The natural isoflavone phytoestrogen genistein has been shown to stimulate osteoblastic bone formation, inhibit osteoclastic bone resorption, and prevent bone loss in ovariectomized rats. However, no controlled clinical trial has been performed so far to evaluate the effects of the phytoestrogen on bone loss in postmenopausal women. We performed a randomized double-blind placebo-controlled study to evaluate and compare with hormone-replacement therapy (HRT) the effect of the phytoestrogen genistein on bone metabolism and bone mineral density (BMD) in postmenopausal women. Participants were 90 healthy ambulatory women who were 47-57 years of age, with a BMD at the femoral neck of <0.795 g/cm2. After a 4-week stabilization on a standard fat-reduced diet, participants of the study were randomly assigned to receive continuous HRT for 1 year (n = 30; 1 mg of 17beta-estradiol [E2] combined with 0.5 mg of norethisterone acetate), the phytoestrogen genistein (n = 30; 54 mg/day), or placebo (n = 30). Urinary excretion of pyridinoline (PYR) and deoxypyridinoline (DPYR) was not significantly modified by placebo administration either at 6 months or at 12 months. Genistein treatment significantly reduced the excretion of pyridinium cross-links at 6 months (PYR = -54 +/- 10%; DPYR = -55 +/- 13%; p < 0.001) and 12 months (PYR = -42 +/- 12%; DPYR = -44 +/- 16%; p < 0.001). A similar and not statistically different decrease in excretion of pyridinium cross-links was also observed in the postmenopausal women randomized to receive HRT. Placebo administration did not change the serum levels of the bone-specific ALP (B-ALP) and osteocalcin (bone Gla protein [BGP]). In contrast, administration of genistein markedly increased serum B-ALP and BGP either at 6 months (B-ALP = 23 +/- 4%; BGP = 29 +/- 11%; p < 0.005) or at 12 months (B-ALP = 25 +/- 7%; BGP = 37 +/- 16%; p < 0.05). Postmenopausal women treated with HRT had, in contrast, decreased serum B-ALP and BGP levels either at 6 months (B-ALP = -17 +/- 6%; BGP = -20 +/- 9%; p < 0.001) or 12 months (B-ALP = -20 +/- 5%; BGP = -22 +/- 10%; p < 0.001). Furthermore, at the end of the experimental period, genistein and HRT significantly increased BMD in the femur (femoral neck: genistein = 3.6 +/- 3%, HRT = 2.4 +/- 2%, placebo = -0.65 +/- 0.1%, and p < 0.001) and lumbar spine (genistein = 3 +/- 2%, HRT = 3.8 +/- 2.7%, placebo = -1.6 +/- 0.3%, and p < 0.001). This study confirms the genistein-positive effects on bone loss already observed in the experimental models of osteoporosis and indicates that the phytoestrogen reduces bone resorption and increases bone formation in postmenopausal women.

J Bone Miner Res. 2002 Oct;17(10):1904-12

Relationships of urinary phyto-oestrogen excretion to BMD in postmenopausal women.
OBJECTIVE: Phyto-oestrogens are plant compounds with both oestrogenic and anti-oestrogenic properties. However, it is not known whether natural phyto-oestrogens are beneficial or harmful in human osteoporosis. This study was performed to investigate the relationships between urinary phyto-oestrogens and bone mineral density (BMD) in Korean postmenopausal women. DESIGN: The subjects were classified into osteoporotic, osteopenic and normal groups according to their BMD as defined by WHO criteria. We compared the urinary phyto-oestrogens of each group and studied whether urinary phyto-oestrogens correlate with BMD. PATIENTS: The subjects were 75 Korean postmenopausal women with ages ranging from 52 to 65 years (mean 58 +/- 1.1 years). Mean number of years after menopause was 7.3 +/- 1.3. MEASUREMENTS: Twenty-four-hour urinary phyto-oestrogens were measured by gas chromatography-mass spectrometry (GCMS) and BMD by dual-energy X-ray absorptiometry (DXA, Lunar Expert-XL, Lunar Co., WI, USA ). RESULTS: In Korean postmenopausal women, urinary enterolactone (1.46 +/- 1.11 micromol/day) was lower and daidzein (2.59 +/- 3.25 micromol/day) was higher than in western women, and both levels were comparable to those in Japanese women. Daily urinary excretion of genistein and apigenin were 1.09 +/- 0.912 and 0.48 +/- 0.40 micromol/day, respectively. In subjects with osteoporosis, urinary enterolactone was lower (P < 0.05) but apigenin was significantly higher (P < 0.05) than in the controls. BMD of L2-L4 correlated positively with urinary enterolactone (r = 0.388, P < 0.01), and BMD of the femoral neck and Ward's triangle correlated positively with urinary enterolactone (r = 0.271, P < 0.05 and r = 0.322, P < 0.05) but negatively with apigenin (r = -0.412, P < 0.01 and r = -0.395, P < 0.01). By multiple stepwise regression, the variables associated with spinal BMD were age, the amount of urinary apigenin and body mass index (BMI). The variables associated with femoral neck BMD were age and urinary apigenin. CONCLUSIONS: From these results, we conclude that urinary phyto-oestrogens, especially enterolactone and apigenin, are related to BMD in Korean postmenopausal women. Our results also suggest the possibility that phyto-oestrogens have differential effects on bone density. Further studies are needed to clarify the exact biological roles of phyto-oestrogenic components on bone metabolism.

Clin Endocrinol (Oxf). 2002 Mar;56(3):321-8