Consumption of soy isoflavones does not affect plasma total homocysteine or asymmetric dimethylarginine concentrations in healthy postmenopausal women

The Effects of Medicinal Plants and Bioactive Natural Compounds on Homocysteine

BACKGROUND

Among non-communicable diseases, cardiovascular diseases (CVDs) are the leading cause of mortality and morbidity in global communities. By 2030, CVD-related deaths are projected to reach a global rise of 25 million. Obesity, smoking, alcohol, hyperlipidemia, hypertension, and hyperhomocysteinemia are several known risk factors for CVDs. Elevated homocysteine is tightly related to CVDs through multiple mechanisms, including inflammation of the vascular endothelium. The strategies for appropriate management of CVDs are constantly evolving; medicinal plants have received remarkable attention in recent researches, since these natural products have promising effects on the prevention and treatment of various chronic diseases. The effects of nutraceuticals and herbal products on CVD/dyslipidemia have been previously studied. However, to our knowledge, the association between herbal bioactive compounds and homocysteine has not been reviewed in details. Thus, the main objective of this study is to review the efficacy of bioactive natural compounds on homocysteine levels according to clinical trials and animal studies.

RESULTS

Based on animal studies, black and green tea, cinnamon, resveratrol, curcumin, garlic extract, ginger, and soy significantly reduced the homocysteine levels. According to the clinical trials, curcumin and resveratrol showed favorable effects on serum homocysteine. In conclusion, this review highlighted the beneficial effects of medicinal plants as natural, inexpensive, and accessible agents on homocysteine levels based on animal studies. Nevertheless, the results of the clinical trials were not uniform, suggesting that more well-designed trials are warranted.

Effect of soy products and isoflavones on oxidative stress parameters: A systematic review and meta-analysis of randomized controlled trials

Soy products and isoflavones intake have been shown to exert antioxidant effects. There are several randomized control trials (RCTs) that evaluated the effect of soy products intake on oxidative stress (OS) parameters. The aim of the present systematic review and meta-analysis was to summarize the results of RCTs evaluating the effect of soy products and isoflavones intake on OS parameters. Randomized trials that assessed the effect of soy products and isoflavones intake on OS parameters in adults were identified through searching in electronic databases: Cochrane clinical trial center, Embase, PubMed, Scopus, and Web of Sciences up to April 2020. Random effects model was used to calculate the effects sizes of soy intake on OS parameters. Twenty-four trials with 1,852 participants were eligible and were included in the meta-analysis which measured OS parameters. Soy intake compared to control group significantly reduced MDA levels (SMD: -0.53; 95% CI: -0.86, -0.19; I2 = 88.3%), increased GSH levels (SMD: 0.51; 95% CI: 0.13, 0.88; I2 = 72.4%), SOD activity (SMD: 0.53; 95% CI: 0.08, 0.99; I2 = 84.1%), TAC (SMD: 0.54; 95% CI: 0.27, 0.82; I2 = 49.3%) and TRAP (SMD: 1.74; 95% CI: 0.82, 2.65; I2 = 81.3%) significantly compared to control group. Soy products and isoflavones intake are effective in improving OS parameters in adults compared with controls; thus, it could be a valuable advise to control OS progress in chronic diseases.

Effect of S-equol and Soy Isoflavones on Heart and Brain

BACKGROUND

Observational studies in Asia show that dietary intake of soy isoflavones had a significant inverse association with coronary heart disease (CHD). A recent randomized controlled trial (RCT) of soy isoflavones on atherosclerosis in the US, however, failed to show their benefit. The discrepancy may be due to the much lower prevalence of S-equol producers in Westerners: Only 20-30% of Westerners produce S-equol in contrast to 50-70% in Asians. S-equol is a metabolite of dietary soy isoflavone daidzein by gut microbiome and possesses the most antiatherogenic properties among all isoflavones. Several short-duration RCTs documented that soy isoflavones improves arterial stiffness. Accumulating evidence shows that both atherosclerosis and arterial stiffness are positively associated with cognitive decline/dementia. Therefore, potentially, soy isoflavones, especially S-equol, are protective against cognitive decline/dementia.

METHODS/RESULTS

This narrative review of clinical and epidemiological studies provides an overview of the health benefits of soy isoflavones and introduces S-equol. Second, we review recent evidence on the association of soy isoflavones and S-equol with CHD, atherosclerosis, and arterial stiffness as well as the association of atherosclerosis and arterial stiffness with cognitive decline/ dementia. Third, we highlight recent studies that report the association of soy isoflavones and S-equol with cognitive decline/dementia. Lastly, we discuss the future directions of clinical and epidemiological research on the relationship of S-equol and CHD and dementia.

CONCLUSIONS

Evidence from observational studies and short-term RCTs suggests that S-equol is anti-atherogenic and improves arterial stiffness and may prevent CHD and cognitive impairment/ dementia. Well-designed long-term (≥ 2years) RCTs should be pursued.

The impact of equol-producing status in modifying the effect of soya isoflavones on risk factors for CHD: a systematic review of randomised controlled trials

Recent studies suggest that the ability to produce equol, a metabolite of the soya isoflavone daidzein, is beneficial to coronary health. Equol, generated by bacterial action on isoflavones in the human gut, is biologically more potent than dietary sources of isoflavones. Not all humans are equol producers. We investigated whether equol-producing status is favourably associated with risk factors for CHD following an intervention by dietary soya isoflavones. We systematically reviewed randomised controlled trials (RCT) that evaluated the effect of soya isoflavones on risk factors for CHD and that reported equol-producing status. We searched PubMed, EMBASE, Ovid Medline and the Cochrane Central Register for Controlled Trials published up to April 2015 and hand-searched bibliographies to identify the RCT. Characteristics of participants and outcomes measurements were extracted and qualitatively analysed. From a total of 1671 studies, we identified forty-two articles that satisfied our search criteria. The effects of equol on risk factors for CHD were mainly based on secondary analyses in these studies, thus with inadequate statistical power. Although fourteen out of the forty-two studies found that equol production after a soya isoflavone intervention significantly improved a range of risk factors including cholesterol and other lipids, inflammation and blood pressure variables, these results need further verification by sufficiently powered studies. The other twenty-eight studies primarily reported null results. RCT of equol, which has recently become available as a dietary supplement, on CHD and its risk factors are awaited.

The effect of soy or isoflavones on homocysteine levels: a meta-analysis of randomised controlled trials

BACKGROUND

The present study aimed to evaluate the effect of soy or isoflavones on blood homocysteine levels via a systematic review and meta-analysis.

METHODS

Pubmed, Embase, Web of Science and the Cochrane Library (up to 16 December 2015) were used for the literature review. Only randomised controlled trials were included. The primary outcome was the standard mean difference (SMD) of blood homocysteine levels between the experimental and control groups.

RESULTS

Nineteen randomised controlled studies were included for qualitative analysis. Eighteen studies were included in the data synthesis. Soy or isoflavones were found to have no effect on homocysteine levels, with a SMD of -0.21 (95% confidence interval = -0.43 to 0.00, I² =67.7%, random effect model). No publication bias was found among those studies (P = 0.296 for Egger's test, and P = 0.198 for Begg's test).

CONCLUSIONS

Soy or isoflavones were not found to be associated with a reduction in homocysteine levels. Further studies might still be needed in carefully selected populations.

The methylarginines NMMA, ADMA, and SDMA are ubiquitous constituents of the main vegetables of human nutrition

Endogenous methylarginines, N(G),N(G)-dimethyl-L-arginine (asymmetric dimethylarginine, ADMA), N(G)-N('G)-dimethyl-L-arginine (symmetric dimethylarginine; SDMA), and N(G)-monomethyl-L-arginine (monomethylarginine; NMMA) are supposed to be produced in human body through the methylation of protein arginine residues by protein arginine methyltransferases (PRMT) and released during proteolysis of the methylated proteins. Micromolar concentration of ADMA and NMMA can compete with arginine for nitric oxide synthase (NOS) reducing nitric oxide (NO) formation, whereas SDMA does not. Indeed, increased ADMA and SDMA plasma levels or a decreased arginine/ADMA ratio is related with risk factors for chronic kidney disease and cardiovascular disease. To the best of our knowledge the exogenous presence of methylarginines, like that in fruits and vegetables, has never been described so far. Here, we report the finding that methylarginines are ubiquitous in vegetables which represent an important part of human daily diet. Some of these vegetables contain discrete amounts of ADMA, SDMA, and NMMA. Specifically, among the vegetables examined, soybean, rye, sweet pepper, broad bean, and potato contain the highest ADMA and NMMA mean levels. Our results establish that the three methylarginines, in addition to being produced endogenously, can also be taken daily through the diet in conspicuous amounts. We propose that the contribution of the methylarginines contained in the vegetables of daily diet should be taken into account when the association between vegetable assumption and their levels is evaluated in clinical studies. Furthermore, a comprehensive understanding on the role of the digestive breakdown process and intestinal absorption grade of the methylarginines contained in vegetables is now needed.

High tea and vegetable consumption is associated with low ADMA generation in older healthy subjects

Asymmetric dimethylarginine (ADMA) has been recognized as a marker of cardiovascular risk. We sought to investigate whether consumption of tea, coffee, fruit or vegetables is associated with ADMA. In 148 consecutive apparently healthy subjects (104 men and 44 women aged 40 to 70), daily tea, coffee, fruit and vegetable consumption was ascertained by questionnaire. Plasma ADMA, symmetric dimethylarginine (SDMA), and l-arginine levels were measured by high-performance liquid chromatography. Median tea and coffee consumption was 2 cups/d, while vegetable and fruit intake was 152 (120-179)g/d and 120 (108-134)g/d, respectively. Median plasma ADMA, SDMA and arginine were 0.47 (0.43-0.53)μmol/L, 0.59 (0.54-0.66)μmol/L and 86 (68-101)μmol/L, respectively. ADMA correlated inversely with tea (r = -0.70, P < .0001) and vegetable consumption (r = -0.50, P < .0001) even after adjustment for age, sex, body mass index, smoking status, and potential dietary and biochemical parameters. No association between ADMA and fruit consumption was found. ADMA correlated positively with coffee intake (r = 0.37, P < .0001), although these associations were less potent after adjustment for dietary factors. Higher tea and vegetable intake is associated with lower plasma ADMA levels in healthy middle-aged subjects.

Immunoregulatory effects of the flavonol quercetin in vitro and in vivo

PURPOSE

Atherosclerosis is known to be an inflammatory disease. Dendritic cells (DCs) are essential for the regulation of the immune system. Up to 10% of the cells in atherosclerotic plaques are DCs. The cardiovascular protective effects of flavonoids (tea, wine) may be mediated by anti-inflammatory mechanisms that affect DC regulation. We aimed to characterize the impact of the flavonol quercetin on DC activity and differentiation in vitro and in vivo.

METHODS

For the in vitro experiments, we used murine DCs and endothelial cells to study adhesion properties. For all other experiments (DC phagocytosis capacity, DC maturation, DC differentiation (BDCA-1/-2) and NF-kB-activation), human monocyte-derived DCs were used. The cells were incubated with quercetin (10 μmol/L) ± oxLDL (10 μg/mL) between 24 and 48 h. For in vivo experiments, eight healthy male volunteers took 500 mg of quercetin twice daily over 4 weeks, five healthy male volunteers served as control. Before and after intake, blood samples were collected. Peripheral blood leukocytes were isolated (analyses of DC differentiation), and plasma was immediately frozen.

RESULTS

Quercetin reduced DC adhesion (-42%; p < 0.05) and expression of CD11a (-21%; p < 0.05). OxLDL-induced DC differentiation was partially inhibited by quercetin (BDCA-1-29%; BDCA-2-33%; p < 0.05). These effects were achieved by compensation of oxLDL-induced up-regulation of NF-kB by quercetin. The 4-week treatment with quercetin resulted in relevant plasma levels (2.47 μmol/L) and reduced BDCA-2 + DCs in the peripheral blood by 42% (p < 0.05) as well as systemic levels of the NO-synthase inhibitor asymmetric dimethylarginine (-31%, p < 0.05).

CONCLUSION

In vitro, quercetin reduced DC adhesion and oxLDL-induced DC differentiation. In vivo, quercetin reduced circulating plasmacytoid DCs and systemic ADMA-levels. The immunoregulatory effects of quercetin may contribute to the anti-atherosclerotic potential of flavonols.

Side effects of phytoestrogens: a meta-analysis of randomized trials

BACKGROUND

Phytoestrogens are widely used by postmenopausal women for the treatment of the climacteric syndrome. The risk of adverse effects of this treatment, however, is unknown.

METHODS

Using a fixed-effects model, we performed a meta-analysis of side effects comparing phytoestrogen treatment with placebo or no treatment in randomized controlled trials.

RESULTS

We identified 174 randomized controlled trials. Side effects were reported in 92/174 randomized controlled trials with 9629 participants. The overall incidence of side effects in the phytoestrogen and control groups was 2019/5502 (36.7%) and 1824/4806 (38.0%), respectively (P=.2; incidence rate ratio [IRR] 1.01; 95% confidence interval [CI], 0.95-1.08). Comparing various side effect categories, we found significantly higher rates of gastrointestinal side effects among phytoestrogen users (P=.003; IRR 1.28; 95% CI, 1.08-1.50). Gynecological (IRR 0.94; 95% CI, 0.74-1.20), musculoskeletal (IRR 1.20; 95% CI, 0.94-1.53), neurological (IRR 0.91; 95% CI, 0.70-1.19), and unspecific side effects (IRR 0.95; 95% CI, 0.88-1.03) were not significantly different between groups. Within side effect categories, we found no significantly higher rates of side effects in women using phytoestrogens. Specifically, the rates of hormone-related side effects such as endometrial hyperplasia, endometrial cancer, and breast cancer were not significantly different between groups.

CONCLUSIONS

Based on the available evidence, phytoestrogen supplements have a safe side-effect profile with moderately elevated rates of gastrointestinal side effects. Rates of vaginal bleeding, endometrial hyperplasia, endometrial cancer, and breast cancer were not significantly increased among phytoestrogen users in the investigated studies.

Effects of soy consumption on oxidative stress, blood homocysteine, coagulation factors, and phosphorus in peritoneal dialysis patients

OBJECTIVE

We studied the effects of soy consumption on oxidative stress, blood homocysteine, coagulation factors, and phosphorus in peritoneal dialysis patients.

DESIGN

This was an unblinded, randomized clinical trial.

SETTING

This study involved peritoneal dialysis centers in Tehran, Iran.

PATIENTS

We included 40 peritoneal dialysis patients (20 males and 20 females).

INTERVENTION

Peritoneal dialysis patients were randomly assigned to either a soy or control group. Patients in the soy group received 28 g/day textured soy flour (containing 14 g of soy protein) for 8 weeks, whereas patients in the control group received their usual diet, without any soy.

MAIN OUTCOME MEASURES

Blood oxidized low-density lipoprotein (ox-LDL), homocysteine, phosphorus, fibrinogen concentrations, and the activities of coagulation factors VII, IX, and X were measured at baseline and at the end of week 8 of the study.

RESULTS

The percentage of plasma coagulation factor IX activity decreased significantly by 17% in the soy group at the end of week 8 compared with baseline (P < .01), and the reduction was significant compared with the control group (P < .05). There were no significant differences between the two groups in mean changes of blood ox-LDL, homocysteine, phosphorus, fibrinogen concentrations, and the activities of coagulation factors VII and X.

CONCLUSION

Soy consumption reduces plasma coagulation factor IX activity, which is a risk factor for thrombosis in peritoneal dialysis patients.

Proteomic biomarkers of peripheral blood mononuclear cells obtained from postmenopausal women undergoing an intervention with soy isoflavones

BACKGROUND

The incidence of cardiovascular diseases increases after menopause, and soy consumption is suggested to inhibit disease development.

OBJECTIVE

The objective was to identify biomarkers of response to a dietary supplementation with an isoflavone extract in postmenopausal women by proteome analysis of peripheral blood mononuclear cells.

DESIGN

The study with healthy postmenopausal woman was performed in a placebo-controlled sequential design. Peripheral mononuclear blood cells were collected from 10 volunteers after 8 wk of receiving daily 2 placebo cereal bars and after a subsequent 8 wk of intervention with 2 cereal bars each providing 25 mg of isoflavones. The proteome of the cells was visualized after 2-dimensional gel electrophoresis, and peptide mass fingerprinting served to identify proteins that by the intervention displayed altered protein concentrations.

RESULTS

Twenty-nine proteins were identified that showed significantly altered expression in the mononuclear blood cells under the soy-isoflavone intervention, including a variety of proteins involved in an antiinflammatory response. Heat shock protein 70 or a lymphocyte-specific protein phosphatase and proteins that promote increased fibrinolysis, such as alpha-enolase, were found at increased intensities, whereas those that mediate adhesion, migration, and proliferation of vascular smooth muscle cells, such as galectin-1, were found at reduced intensities after soy extract consumption.

CONCLUSION

Proteome analysis identified in vivo markers that respond to a dietary intervention with isoflavone-enriched soy extract in postmenopausal women. The nature of the proteins identified suggests that soy isoflavones may increase the antiinflammatory response in blood mononuclear cells that might contribute to the atherosclerosis-preventive activities of a soy-rich diet.

Consumption of isoflavone-rich soy protein does not alter homocysteine or markers of inflammation in postmenopausal women

BACKGROUND/OBJECTIVE

To investigate the effect of soy protein containing isoflavones on homocysteine (Hcy), C-reactive protein (CRP), soluble E-selectin (sE-selectin), soluble vascular adhesion molecule-1 (sVCAM-1) and soluble intercellular adhesion molecule-1 (sICAM-1).

SUBJECT/METHODS

In a randomized crossover design, 34 postmenopausal women consumed soy protein isolate (26+/-5 g protein containing 44+/-8 mg isoflavones per day) or milk protein isolate (26+/-5 g protein per day) for 6 weeks each. Fasting blood samples were collected at the end of each diet period and end points analyzed by enzyme-linked immunosorbent assay.

RESULTS

Concentrations of Hcy, CRP, sE-selectin, sVCAM-1 and sICAM-1 were not different between soy and milk diet treatments. Results did not differ by equol production status or by baseline lipid concentration. Adjustment for intake of folate and methionine did not alter the Hcy results.

CONCLUSIONS

These data suggest that decreasing vascular inflammation and Hcy concentration are not likely mechanisms by which soy consumption reduces coronary heart disease risk.

Effects of a supplement containing isoflavones and Actaea racemosa L. on asymmetric dimethylarginine, lipids, and C-reactive protein in menopausal women

OBJECTIVE

To investigate the effects of a supplement containing soy isoflavones and Actaea racemosa L. on several coronary heart disease (CHD) risk markers in menopausal women.

DESIGN

Randomized, placebo-controlled, double-blind study.

SETTING

Nine hospitals in The Netherlands.

PATIENT(S)

One hundred twenty-four menopausal women.

INTERVENTION(S)

Daily placebo (n = 64) or supplement containing soy isoflavones and Actaea racemosa L. (n = 60) for 12 weeks.

MAIN OUTCOME MEASURE(S)

Fasting blood concentrations of asymmetric dimethylarginine (ADMA), lipids, and C-reactive protein (CRP) at baseline and week 12.

RESULT(S)

In the supplement group, total cholesterol and low-density lipoprotein cholesterol showed a small absolute reduction at week 12 (-0.2, 95% confidence interval [CI] -0.3 to -0.0; and -0.2, 95% CI -0.3 to -0.0; respectively). Concentrations of ADMA, triglycerides, lipoprotein(a), and CRP did not change significantly. Analysis of covariance over the 12-week study period revealed no significant between-group differences for all parameters. No significant correlations were found between the concentrations of isoflavones and the CHD risk markers investigated.

CONCLUSION(S)

Twelve-week administration of a supplement containing soy isoflavones and Actaea racemosa L. had little or no influence on the CHD risk markers studied. This supplement probably has neither protective nor adverse effects on the cardiovascular system; however, large long-term studies are needed to test this.

Effects of soy isoflavones and phytate on homocysteine, C-reactive protein, and iron status in postmenopausal women

BACKGROUND

Soy protein or its components may protect against the atherosclerotic cardiovascular disease (CVD) risk factors total homocysteine (tHcy), C-reactive protein (CRP), and excess body iron, which generally increase with menopause.

OBJECTIVE

The primary objective of this study was to determine the independent effect of the soy protein components isoflavones and phytate on CVD risk factors in postmenopausal women. The secondary objective was to identify factors [blood lipids, oxidative stress indexes, serum ferritin, plasma folate, plasma vitamin B-12, and body mass index (BMI)] contributing to tHcy and CRP concentrations.

DESIGN

In a double-blind, 6-wk study, 55 postmenopausal women aged 47-72 y were randomly assigned to 1 of 4 soy protein (40 g/d) isolate treatments: native phytate and native isoflavone (n = 14), native phytate and low isoflavone (n = 13), low phytate and native isoflavone (n = 14), or low phytate and low isoflavone (n = 14). We measured iron indexes, tHcy, CRP, and BMI.

RESULTS

Soy protein with native phytate significantly reduced tHcy (P = 0.017), transferrin saturation (P = 0.027), and ferritin (P = 0.029), whereas soy protein with native isoflavones had no effect on any variables. At baseline, BMI was highly correlated with tHcy (r = 0.39, P = 0.003) and CRP (r = 0.55, P < 0.0001), whereas HDL cholesterol was correlated with CRP (r = -0.30, P = 0.02). Multiple regression analysis showed that LDL cholesterol and BMI contributed significantly (R2= 19.9%, P = 0.003) to the overall variance in tHcy.

CONCLUSION

Consuming phytate-rich foods and maintaining a healthy weight may reduce atherosclerotic CVD risk factors in postmenopausal women.