Soy Protein With Isoflavones, but not an Isoflavone-Rich Supplement, Improves Arterial Low-Density Lipoprotein Metabolism and Atherogenesis

Fetal and neonatal genistein exposure aggravates to interfere with ovarian follicle development of obese female mice induced by high-fat diet

With epidemic of obesity, it affects aspects of female reproduction. Genistein could ameliorate obesity in people and animals, but might exert adverse effects on the female reproductive system. To evaluate the effects of fetal and neonatal genistein exposure on the ovarian health of F1 obese female mice with obesity induced by high-fat diet after weaning, we simulated a diet-induced obesity model to observe and determine biological effects of genistein exposure on the ovarian follicle of overfed female mice. Results showed that F1 female mice with obesity induced by high-fat diet significantly prolonged the estrus cycle, disrupted sex hormonal balance and ovarian follicle development after they were exposed to 25 mg/kg b.w./day of genistein during the fetal and neonatal stages. Genistein significantly up-regulated the ovarian mRNA expression of estrogen receptor beta in F1 obese female mice, and high-fat diet influenced the ovarian mRNA expression of estrogen receptor alpha, luteinizing hormone receptor and follicle-stimulating hormone receptor. Hence, genistein exposure from the fetal stage might increase the risk of reproductive diseases in obese females in later life. Thus, the long-term risks of genistein to obese females should be thoroughly assessed.

Effects of isoflavone-containing soya protein on ex vivo cholesterol efflux, vascular function and blood markers of CVD risk in adults with moderately elevated blood pressure: a dose-response randomised controlled trial

Emerging CVD risk factors (e.g. HDL function and central haemodynamics) may account for residual CVD risk experienced by individuals who meet LDL-cholesterol and blood pressure (BP) targets. Recent evidence suggests that these emerging risk factors can be modified by polyphenol-rich interventions such as soya, but additional research is needed. This study was designed to investigate the effects of an isoflavone-containing soya protein isolate (delivering 25 and 50 g/d soya protein) on HDL function (i.e. ex vivo cholesterol efflux), macrovascular function and blood markers of CVD risk. Middle-aged adults (n 20; mean age=51·6 (sem 6·6) years) with moderately elevated brachial BP (mean systolic BP=129 (sem 9) mmHg; mean diastolic BP=82·5 (sem 8·4) mmHg) consumed 0 (control), 25 and 50 g/d soya protein in a randomised cross-over design. Soya and control powders were consumed for 6 weeks each with a 2-week compliance break between treatment periods. Blood samples and vascular function measures were obtained at baseline and following each supplementation period. Supplementation with 50 g/d soya protein significantly reduced brachial diastolic BP (-2·3 mmHg) compared with 25 g/d soya protein (Tukey-adjusted P=0·03) but not the control. Soya supplementation did not improve ex vivo cholesterol efflux, macrovascular function or other blood markers of CVD risk compared with the carbohydrate-matched control. Additional research is needed to clarify whether effects on these CVD risk factors depend on the relative health of participants and/or equol producing capacity.

Neonatal isoflavone exposure interferes with the reproductive system of female Wistar rats

There is increasing concern about possible adverse effects of soy based infant formulas (SBIF) due to their high amount of isoflavones (ISO). The aim of the present study was to investigate effects of neonatal exposure to ISO on reproductive system of female Wistar rats. Animals were exposed to an ISO depleted diet or a diet enriched with an ISO extract (IRD; 508mg ISO/kg) during embryogenesis and adolescence. Pups of each group were fed daily by pipette with ISO-suspension (ISO+; 32mg ISO/kg bw) or placebo from postnatal day (PND) 1 until PND23 resulting in plasma concentrations similar to levels reported in infants fed SBIF. The visceral fat mass was reduced by long-term IRD. Vaginal epithelial height was increased at PND23 and vaginal opening was precocious in ISO+ groups. Later in life, more often irregular estrus cycles were observed in rats of ISO+ groups. In addition, FSH levels and uterine epithelial heights were increased at PND80 in ISO+ groups. In summary, the results indicate that neonatal ISO intake, resulting in plasma concentrations achievable through SBIF, has an estrogenic effect on prepubertal rats and influences female reproductive tract later in life.

Epigenetic changes with dietary soy in cynomolgus monkeys

Nutritional interventions are important alternatives for reducing the prevalence of many chronic diseases. Soy is a good source of protein that contains isoflavones, including genistein and daidzein, and may alter the risk of obesity, Type 2 diabetes, osteoporosis, cardiovascular disease, and reproductive cancers. We have shown previously in nonhuman primates that soy protein containing isoflavones leads to improved body weight, insulin sensitivity, lipid profiles, and atherosclerosis compared to protein without soy isoflavones (casein), and does not increase the risk of cancer. Since genistein has been shown to alter DNA methylation, we compared the methylation profiles of cynomolgus monkeys, from multiple tissues, eating two high-fat, typical American diets (TAD) with similar macronutrient contents, with or without soy protein. DNA methylation status was successfully determined for 80.6% of the probes in at least one tissue using Illumina's HumanMethylation27 BeadChip. Overall methylation increased in liver and muscle tissue when monkeys switched from the TAD-soy to the TAD-casein diets. Genes involved in epigenetic processes, specifically homeobox genes (HOXA5, HOXA11, and HOXB1), and ABCG5 were among those that changed between diets. These data support the use of the HumanMethylation27 BeadChip in cynomolgus monkeys and identify epigenetic changes associated with dietary interventions with soy protein that may potentially affect the etiology of complex diseases.

Effect of Cheonggukjang supplementation upon hepatic acyl-CoA synthase, carnitine palmitoyltransferase I, acyl-CoA oxidase and uncoupling protein 2 mRNA levels in C57BL/6J mice fed with high fat diet

This study investigated the effect of Cheonggukjang on mRNA levels of hepatic acyl-CoA synthase (ACS), carnitine palmitoyltransferase I (CPT-I), acyl-CoA oxidase (ACO) and uncoupling protein 2 (UCP2), and on serum lipid profiles in C57BL/6J mice. Thirty male C57BL/6J mice were divided into three groups; normal diet (ND), high fat diet (HD) and high fat diet with 40% Cheonggukjang (HDC). Energy intake was significantly higher in the HDC group than in the ND and HD groups. The HDC group normalized in weight gain, epididymal and back fat (g/100 g) accumulation which are increased by high fat diet. Serum concentrations of triglyceride and total cholesterol in the HDC were significantly lower than those in the HD group. These results were confirmed by hepatic mRNA expression of enzymes and protein (ACS, CPT-1, ACO, UCP2) which is related with lipid metabolism by RT-PCR. Hepatic CPT-I, ACO and UCP2 mRNA expression was increased by Cheonggukjang supplementation. We demonstrated that Cheonggukjang supplement leads to increased mRNA expressions of enzymes and protein involved in fatty acid oxidation in liver, reduced accumulation of body fat and improvement of serum lipids in high fat diet fed mice.

Effects of Glycyrrhiza glabra polysaccharides on immune and antioxidant activities in high-fat mice

The purpose of this study was to investigate the immune and antioxidant activities of Glycyrrhiza glabra polysaccharides (GGP) in rats fed high-fat diet. The experiment was performed on four groups of growing Kunming mice. The results of the experiment showed a statistically significant decrease in serum antioxidant enzyme activities in high-fat group. Administration of GGP dose-dependently significantly enhanced immune and antioxidant enzyme activities in the GGP-treated mice compared to the high-fat model mice. It is concluded that GGP treatment can enhance immune activities, and reduce oxidative stress in high-fat mice.

Suppressive effect of an isoflavone fraction on tumor necrosis factor-alpha-induced interleukin-8 production in human intestinal epithelial Caco-2 cells

This study demonstrates the effect of soybean components on the tumor necrosis factor-alpha (TNF-alpha)-induced production of interleukin-8 (IL-8), one of the major inflammatory chemokines, in intestinal epithelial-like Caco-2 cells. Among the soybean components, an isoflavone fraction (IFF) suppressed the TNF-alpha-induced IL-8 secretion by Caco-2 cells in a dose-dependent manner, whereas a soyasaponin fraction and soypeptide fraction had no significant effect on TNF-alpha-induced IL-8 secretion. The IL-8 secretion induced by hydrogen peroxide and by IL-1beta was not suppressed by IFF, suggesting that the inhibitory effect of isoflavone was specific for the TNF-alpha-induced regulation of IL-8. The increased expression of IL-8 mRNA by TNF-alpha was almost completely suppressed by IFF. Furthermore, the transcriptional activity of the human IL-8 promoter was increased by the TNF-alpha treatment, and IFF significantly suppressed the IL-8 promoter activity. These results indicate that IFF suppressed TNF-alpha-induced IL-8 production at the transcriptional level in human intestinal Caco-2 cells, suggesting IFF of soybean as a promising food component for preventing intestinal inflammation such as inflammatory bowel disease.

Effect of dietary soy protein on tumor necrosis factor productivity in macrophages from nephritic and hepatoma-bearing rats

The present study investigated the effect of dietary soy protein isolate (SPI) on tumor necrosis factor-alpha (TNF) productivity in peritoneal macrophages from nephritic and hepatoma-bearing rats. Dietary SPI significantly inhibited the elevated production of TNF by lipopolysaccharide-stimulated macrophages in nephritic and hepatoma-bearing rats compared with dietary casein, while it exerted no influence on the TNF productivity in normal rats. Removal of the minor components contained in SPI by ethanol extraction could significantly or partially restore the reduced TNF production caused by SPI in nephritic and hepatoma-bearing rats, respectively. These results suggest that dietary SPI could suppress the enhanced productivity of TNF associated with the progression of nephritis and hepatoma, and some factors existing in the ethanol extract of SPI are suggested to be involved in suppressing TNF productivity by macrophages.

The effects of soy isoflavones on obesity

Over the last decades, the prevalence of obesity and related diseases has increased rapidly in the Western world. Obesity is a disorder of energy balance and is associated with hyper-insulinemia, insulin resistance, and abnormalities in lipid metabolism, and it is one of the most important risk factors in the development of Type II diabetes, cardiovascular disease, atherosclerosis, and certain cancers. Because of the lower frequency of these diseases in Asian countries, attention has been turned toward the Asian diet, which consists highly of soy and soy-based products. The health benefits associated with soy consumption have been linked to the content of isoflavones, the main class of the phytoestrogens. As a result of their structural similarities to endogenous estrogens, isoflavones elicit weak estrogenic effects by competing with 17beta-estradiol (E2) for binding to the intranuclear estrogen receptors (ERs) and exert estrogenic or antiestrogenic effects in various tissues. The estrogenic activities of soy isoflavones are thought to play an important role in their health-enhancing properties. Additionally, the isoflavones have been proved to exert non-ER-mediated effects through numerous other pathways. Genistein, daidzein, and glycitein are the principal isoflavones in soy. Genistein is the most thoroughly examined of these, because it is the most prevalent isoflavone in soy and the most active of these compounds, because of its higher binding affinity for the ER. Genistein and daidzein can be obtained in high levels in humans under certain nutritional conditions, and epidemiologic and laboratory data suggest that these compounds could have health benefits in human obesity. This review will focus on the latest results of research on isoflavones and their effect on obesity in cell cultures, rodents, and humans.

Antioxidative and hypocholesterolemic activities of water-soluble puerarin glycosides in HepG2 cells and in C57 BL/6J mice

Puerarin is an isoflavone derived from Kudzu roots and has antioxidant and hypocholesterolemic effects; however, its insolubility often limits its biological availability in vivo. Using a novel transglycosylation process, the solubility of puerarin glycosides was increased >100-fold, but it was not known whether these modified puerarin glycosides maintained biological activities. We found that water-soluble puerarin glycosides fully maintained antioxidant activities compared with puerarin assessed by radical scavenging activity, reducing power assay, superoxide dismutase activity, and non-site-specific hydroxyl radical scavenging activity. Both puerarin and its glycosides also significantly reduced low-density lipoprotein (LDL) oxidation. Mice fed with puerarin glycosides (0.1% w/w) showed significantly reduced plasma total cholesterol levels, thus, we further investigated their hypocholesterolemic mechanisms by assessing several key gene expressions both in vitro and in vivo. Puerarin and its glycosides induced multiple changes in hepatic cholesterol metabolism. The LDL receptor promoter activity was increased dose-dependently in puerarin glycosides-treated HepG2 cells. Accordingly, the expression of LDL receptor mRNA and protein were also significantly increased in HepG2 cells and mouse livers. The transcription and translation of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase were down-regulated both in vitro and in vivo. The cholesterol 7alpha-hydroxylase (CYP7A1) mRNA levels were not affected in vitro but significantly up-regulated in the mouse livers. Collectively, our results show that puerarin and its glycosides are biologically fully active isoflavone and have antioxidant and hypocholesterolemic effects in HepG2 cells and in C57BL/6J mice. In the livers, hypocholesterolemic effects of puerarin glycoside may be achieved by multiple mechanisms including increasing LDL uptake, reducing cholesterol biosynthesis, and possibly enhancing cholesterol degradation.

Soybean Protein Hydrolysate Improves Plasma and Liver Lipid Profiles in Rats Fed High-Cholesterol Diet

OBJECTIVE

This investigation attempted to clarify the hypolipidemic effects of non-dialyzed soybean protein hydrolysate (NSPH), which is hydrolyzed by pepsin from soybean acid-precipitated protein (APP), in rats fed a cholesterol-rich diet.

METHODS

Forty Sprague-Dawley rats were divided into four groups as the control group (19.7% casein), the APP group (14.7% casein + 5% APP), the NSPH group (14.7% casein + 5% NSPH), and the ISO group (19.7% casein + 0.0013% soy isoflavone).

RESULTS

After 12-week experimental period, the APP and NSPH groups had a significant lower plasma total cholesterol, triglycerides, and LDL-cholesterol concentrations compared with the control group. Additionally, the atherosclerosis index in APP and NSPH group had also markedly decreased. Liver cholesterol and triglyceride contents of the APP and NSPH group were significantly lower than those of the control group. There were no different in plasma LDL-C, liver cholesterol and triglycerides between the ISO group and control group. Fecal excretion of neutral steroids and nitrogen compounds was significantly higher in the APP and NSPH groups than that in the control group. An in vitro study also showed that NSPH, compared with casein, obviously decreased cholesterol micellar solubility.

CONCLUSION

These results suggested that NSPH may decrease lipid accumulation in the liver and have a hypolipidemic effect by enhancing excretion and inhibiting absorption of lipids.

Isoflavones--safe food additives or dangerous drugs?

The sales volume of products containing isoflavone has increased since the publication of the Women's Health Initiative. The many apparently contradictory results published on the effects of isoflavones on a variety of estrogen-regulated organs point to both beneficial as well as adverse effects on human health. It is of particular importance that psychovegetative climacteric complaints such as hot flushes are, if at all, only slightly influenced by isoflavones. The substances appear to have weak anti-osteoporotic effect. Their anti-atherosclerotic action is debatable, as not all authors find any beneficial effect on lipids. Most importantly, there is dispute as to whether isoflavones derived from soy or red clover have negative, positive or any effect at all on the mammary gland or endometrium. It is beyond any doubt that soy products may have cancer preventing properties in a variety of organs including the mammary gland. However, these properties may only be exerted if the developing organ was under the influence of isoflavones during childhood and puberty. This may also explain the often quoted "Japanese Phenomenon", the fact that breast cancer occurs to a lesser extent in Japanese women. When administered to isoflavone "inexperienced" women at the time of menopause, the phytoestrogens appear to share the same effects as estrogen used in classical preparations for hormone replacement therapy, i.e. they may stimulate the proliferation of endometrial and mammary gland tissue with at present unknown and unpredictable risk to these organs. Therefore, the following question arises for the clinician: Why should soy or red clover products containing isoflavone be recommended, if the positive effects are only negligible but the adverse effects serious?

Effects of dietary soy protein on iliac and carotid artery atherosclerosis and gene expression in male monkeys

Male cynomolgus macaques (n=91) consumed an isoflavone (IF)-free, atherogenic control diet containing casein/lactalbumin for 5 months, then were randomized to three groups: control (n=30) continued on the control diet; low IF (n=30) received a mixture of unmodified and IF-depleted soy protein isolate (SPI) (0.94 mg IF/g protein, approximating a human intake of 75 mg/day); high IF (n=31) received unmodified SPI (1.88 mg IF/g protein, approximating a human intake of 150 mg/day) for 31 months. Iliac and carotid artery atherosclerosis, and arterial and hepatic mRNA transcripts related to inflammation and estrogen receptors (ER) were measured. Trend analysis identified a significant inverse relationship between dietary IF content and plaque area in the iliac (p<0.05) but not carotid arteries (p>0.13). No significant effect of diet on inflammatory gene or estrogen receptor expression was observed. Plaque area was positively correlated with the mRNA transcript levels for arterial MCP-1, ICAM-1, and the macrophage marker CD68 (all r>0.25, p<0.03), and negatively correlated with ER alpha and ER beta (all r<-0.23, p<0.03). Coronary artery plaque area appeared to be more closely associated with gene expression patterns of the iliac arteries than the carotid arteries. The data suggests benefits of dietary soy on atherosclerotic plaque development in males may be mediated through inflammation-independent pathways. The negative associations of arterial ER alpha expression with atherosclerosis lend support to a mechanistic role for estrogen receptors in atherosclerosis susceptibility which merits further study.

Replacement of dietary soy protein isolate with concentrates of soy 7S or 11S globulin has minimal or no effects on plasma lipoprotein profiles and biomarkers of coronary risk in monkeys

Effects of soy peptide fractions on risk factors for coronary heart disease are unknown. We compared the effects of a soy protein isolate, a soy 7S fraction concentrate and a soy 11S fraction concentrate on total plasma cholesterol, HDL cholesterol, LDL+VLDL cholesterol and triacylglycerol in adult male cynomolgus monkeys. Effects on biomarkers of coronary risk [soluble E-selectin, vascular cell-adhesion molecule-1 (VCAM-1), monocyte chemoattractant protein-1 (MCP-1), transforming growth factor beta-1 (TGF-beta-1) and plasminogen activator inhibitor-1 (PAI-1)] were also determined. Relative to a soy- and isoflavone-free diet (casein and lactalbumin as the source of protein), soy protein isolate had the predicted favorable effects on plasma lipoproteins, i.e., reductions in total and VLDL+LDL cholesterol (8 and 14%, respectively) (P's<0.05) and a 41% increase in HDL (P<0.05). Effects of 7S and 11S on these variables were less favorable. In fact, there was a 7% increase in total plasma cholesterol concentration (P<0.05) in monkeys fed 7S that was accounted for primarily by an increase in VLDL+LDL cholesterol. There was no effect of any protein source on cardiovascular biomarkers. Replacement of dietary soy protein isolate with concentrated 7S or 11S does not result in improvement of plasma lipoprotein profiles or cardiovascular biomarkers in monkeys.

Effect of isolated isoflavone supplementation on ABCA1-dependent cholesterol efflux potential in postmenopausal women

OBJECTIVE

Isoflavones may display beneficial health effects in postmenopausal women. We studied in a clinical trial whether isolated isoflavone treatment in postmenopausal women could affect reverse cholesterol transport as evaluated by adenosine triphosphate-binding cassette A1- (ABCA1), dependent cholesterol efflux from macrophages. In addition, various serum lipid and lipoprotein parameters were investigated. Furthermore, we separately assessed equol-producing and non-equol-producing women.

DESIGN

Postmenopausal women (n=56) were treated with either isoflavone or placebo tablets for 3 months in a crossover design, separated by a 2-month washout period. Fifteen women were classified as equol producers, and 15 women were classified as non-equol producers. Serum samples were collected before and after each treatment period. [H]-Cholesterol-labeled J774 macrophage cells, with and without ABCA1 up-regulation, were incubated with the samples, and ABCA1-dependent cholesterol efflux and serum lipid and lipoprotein levels were assessed.

RESULTS

Serum promoted 3.1%+/-1.1% and 3.2%+/-1.1% cholesterol efflux from macrophages after isoflavone and placebo treatment, respectively. Thus, isoflavone supplementation did not affect ABCA1-dependent cholesterol efflux to serum. However, as a novel finding, isoflavone treatment increased a subclass of high-density lipoprotein, the pre-beta high-density lipoprotein levels by 18% without affecting any other serum lipid concentrations. ABCA1-facilitated cholesterol efflux and lipid parameters did not differ between equol-producing and non-equol-producing women.

CONCLUSION

In postmenopausal women, isolated isoflavone treatment does not affect ABCA1-dependent cholesterol efflux potential from macrophages but increases circulating pre-beta high-density lipoprotein level, which could provide beneficial vascular effects.

Methods for nutrigenomics and longevity studies in Drosophila: effects of diets high in sucrose, palmitic acid, soy, or beef

Nutrigenomics is the study of gene-nutrient interactions and how they affect the health and metabolism of an organism. Combining nutrigenomics with longevity studies is a natural extension and promises to help identify mechanisms whereby nutrients affect the aging process, life span, and, with the incorporation of age-dependent functional measures, health span. The topics we discuss in this chapter are genetic techniques, dietary manipulations, metabolic studies, and microarray analysis methods to investigate how nutrition affects gene expression, life span, triglyceride levels, total protein levels, and live weight in Drosophila. To better illustrate nutrigenomic techniques, we analyzed Drosophila larvae or adults fed control diets (high sucrose) and compared these with larvae or adults fed diets high in the saturated fat palmitic acid, soy, or 95% lean ground beef. The main results of these studies are, surprisingly, that triglyceride and total protein levels are significantly decreased by the beef diet in all adults, and total protein levels are significantly increased in male flies fed the soy diet. Furthermore, and less surprisingly, we found that all three experimental diets significantly decreased longevity and increased the length of time to develop from egg to adult. We also describe preliminary microarray results with adult flies fed the different diets, which suggest that only about 2-3% of the approx 18,000 genes have significantly altered mRNA expression levels compared with flies fed a control sucrose diet. The significance of these results and other types of nutrigenomics and longevity analyses is discussed.

Flavonoids attenuate cardiovascular disease, inhibit phosphodiesterase, and modulate lipid homeostasis in adipose tissue and liver

Plant flavonoids are widely distributed polyphenolic compounds of the human diet. They consist of six major classes based on specific structural differences: flavonols, flavones, flavanones, catechins, anthocyanidins, and isoflavones. All of the major classes of flavonoids are comprised of three six-membered rings: an aromatic A-ring fused to a heterocyclic C-ring that is attached through a single carbon-carbon bond to an aromatic Bring. Population studies have shown that flavonoid intake is inversely correlated with mortality from cardiovascular disease, and numerous flavonoids of dietary significance have been shown to beneficially impact parameters associated with atherosclerosis, including lipoprotein oxidation, blood platelet aggregation, and vascular reactivity. Therapeutic effects of flavonoids on platelet aggregability and blood pressure have been attributed to competitive inhibition of cyclic nucleotide phosphodiesterase (PDE), an elevation in cAMP level, and subsequent activation of protein kinase A (cAMP-dependent protein kinase). In addition, flavonoids may induce neutral lipid hydrolysis from lipid stores through PDE inhibition in adipose tissue and liver. Indeed, the three-dimensional structure of many flavonoids is sterically and electrostatically compatible with the catalytic site of cAMP PDE3 and PDE4. Flavonoids have also been reported to suppress pathways of lipid biosynthesis and of very low-density lipoprotein production in cultured hepatocytes. Continued studies of the biochemical mechanisms underlying the biological effects of plant flavonoids may uncover new strategies for the treatment of cardiovascular disease, as well as associated conditions such as obesity, hepatic steatosis, and Type 2 diabetes.

Effects of dietary genistein on hepatic lipid metabolism and mitochondrial function in mice fed high-fat diets

OBJECTIVE

Genistein has been suggested to prevent insulin resistance and its related diseases. We investigated the effects of dietary genistein at different levels on hepatic lipid levels and mitochondrial functions in mice fed high-fat diets.

METHODS

C57BL/6J mice were randomly divided into four groups and fed a high-fat diet containing genistein at levels of 0%, 0.1%, 0.2%, and 0.4% (HF, HF + 0.1G, HF + 0.2G, and HF + 0.4G) for 12 wk. We measured lipid levels in the blood and liver. We also observed messenger RNA (mRNA) expression of genes encoding proteins related to lipid and energy metabolism and antioxidant defense system and mitochondrial enzyme activities in the liver.

RESULTS

The induction of fatty liver by HF was substantially decreased in the HF + 0.2G and HF + 0.4G groups. Peroxisome proliferator-activated receptorgamma coactivator mRNA was increased by HF + 0.4G. Although genistein did not affect peroxisomal acyl-CoA oxidase mRNA expression, it increased medium-chain acyl-CoA dehydrogenase mRNA expression in a dose-dependent manner and HF + 0.2G increased uncoupling protein-2 mRNA expression two-fold relative to HF mice. Genistein decreased malondialdehyde levels and increased glutathione levels in liver homogenates, regardless of dose. The HF + 0.1G diet increased mitochondrial glutathione peroxidase activity and mitochondrial succinate dehydrogenase activity.

CONCLUSIONS

Although genistein at higher levels decreased hepatic fat accumulation possibly by increasing fatty acid oxidation and uncoupling protein, low-dose genistein increased mitochondrial enzyme activities in mice with fatty liver and obesity induced by high-fat diets.

Soy protein containing isoflavones favorably influences macrophage lipoprotein metabolism but not the development of atherosclerosis in CETP transgenic mice

The possibility that soy protein containing isoflavones influences the development of experimental atherosclerosis has been investigated in ovariectomized mice heterozygous for the human CETP transgene and for the LDL-receptor null allele (LDLr(+/-) CETP(+/-)). After ovariectomy at 8 wk of age they were fed a fat/cholesterol-rich diet for 19 wk and divided into three experimental groups: dietary unmodified soy protein containing isoflavones (mg/g of diet), either at low-dose (Iso Low, 0.272, n = 25), or at high-dose (Iso High, 0.535, n = 28); and the atherogenic diet containing an isoflavone-depleted alcohol-washed soy protein as a control group (n = 28). Aortic root lipid-stained lesion area (mean microm2 x 10(3) +/- SD) did not differ among Iso Low (12.3 +/- 9.9), Iso High (7.4 +/- 6.4), and controls (10.7 +/- 12.8). Autoantibody titers against plasma oxidized LDL did not differ among the experimental groups. Using the control mice as the reference value (100%), in vitro mouse peritoneal macrophage uptake of labeled acetylated LDL-cholesterol was lower in the Iso High (68%) than in the Iso Low (85%) group. The in vitro percent removal by exogenous HDL of labeled unesterified cholesterol from macrophages previously enriched with human [4- 14C]-cholesteryl oleate acetylated LDL was enhanced in the Iso High group (50%). In spite of these in vitro potentially antiatherogenic actions, soy protein containing isoflavones did not modify the average size of lipid-stained area in the aortic root.

Soy extract has different effects compared with the isolated isoflavones on the proteome of homocysteine-stressed endothelial cells

Epidemiological studies suggest that soy consumption may provide a protection in the development and progression of atherosclerosis. It is under debate, however, whether the soy isoflavones or other compounds are the "active principle". As apoptosis is a driving force in the process of atherosclerosis, we tested whether a soy extract or a combination of the two predominant isoflavones genistein and daidzein, in concentrations as found in the extract, exert similar or different effects on apoptosis in EA.hy 926 endothelial cells after exposure to the endothelial stressor homocysteine. Plasma membrane disintegration and nuclear fragmentation served as relevant apoptosis markers. To assess whether the extract and the genistein/daidzein mixture differently affect cellular target proteins changed in amount by homocysteine treatment, proteome analysis was performed by two-dimensional gel-electrophoresis and peptide mass fingerprinting of regulated protein spots. Homocysteine induced apoptosis in the cells, and both extract and genistein/daidzein inhibited apoptosis to a comparable extent. Whereas the extract prevented for 10 proteins the changes in expression levels as caused by homocysteine, the genistein/daidzein mixture reversed the homocysteine effects on the proteome for 13 proteins. The cytoskeletal protein matrin 3 and a U5 snRNP-specific 40-kDa protein were the only protein entities where both extract and genistein/daidzein reversed the homocysteine-induced changes in a common way. In conclusion, our studies provide evidence that an isoflavone containing soy extract and isolated isoflavones, despite similar effects on inhibition of homocysteine-induced apoptosis in endothelial cells, affect a quite different spectrum of cellular target proteins.

Serum cholesterol efflux potential in postmenopausal women treated with isolated isoflavones

OBJECTIVE

Based on the low cardiovascular risk in Asian populations, phytoestrogens are believed to provide vascular benefits. To elucidate the mechanisms behind the possible cardiovascular effects of phytoestrogens, we evaluated reverse cholesterol transport by assessing the capacity of serum to promote cholesterol efflux in postmenopausal women treated with isolated isoflavones.

DESIGN

Thirty postmenopausal women were treated in a randomized, placebo-controlled, crossover trial with isoflavones or placebo for 3 months interrupted by a 2-month washout period. Serum samples were collected before and after each treatment period, and the cholesterol efflux potential was investigated by using H-cholesterol--labeled Fu5AH cells in culture.

RESULTS

Serum promoted 20.2% +/- 3.0% and 19.9% +/- 3.4% (mean +/- SD) cholesterol efflux after isoflavonoid treatment and after placebo treatment, respectively. Thus, the isoflavone treatment did not affect serum cholesterol efflux. We also studied separately women who produced high concentrations of the isoflavone metabolite equol into serum because some studies suggest that equol could exert favorable vascular effects. However, there was no difference in serum cholesterol efflux capacity between the equol producers (n = 15) and non-equol producers (n = 15).

CONCLUSIONS

In conclusion, isoflavone treatment did not affect serum cholesterol efflux potential in postmenopausal women. Based on our findings, isolated isoflavones do not provide vascular benefits by improving cholesterol efflux.

Soy protein containing isoflavones reduces the size of atherosclerotic plaques without affecting coronary artery reactivity in adult male monkeys

The cardiovascular effects of dietary soy on men or adult male experimental animals have received little attention. We determined the effects of long-term (31 mo) consumption of a commercially available soy protein concentrate containing experimentally varied concentrations of isoflavones on the development of atherosclerosis and vascular reactivity in adult male monkeys. The monkeys were fed atherogenic diets that differed only in the source of protein: Control (n = 30), casein and lactalbumin; low-isoflavone soy (n = 30), a mixture of unmodified soy protein isolate and isoflavone-depleted soy protein isolate containing 0.94 mg of isoflavones/g protein; and high-isoflavone soy (n = 31), unmodified soy protein isolate containing 1.88 mg of isoflavone/g protein. Plasma LDL cholesterol was reduced, whereas HDL cholesterol and apolipoprotein A-1 (P < 0.05) were increased in both groups that consumed soy protein. Atherosclerosis (mean plaque size in the coronary arteries) was reduced by approximately 34% (P < 0.05) in both groups fed soy protein. There were no effects of dietary soy on endothelium-dependent or -independent reactivity of coronary arteries. The results indicate that long-term consumption of soy protein containing a modest amount of isoflavones inhibits the early progression of coronary artery atherosclerosis without affecting endothelium-dependent or -independent arterial function.

The soy isoflavone genistein induces a late but sustained activation of the endothelial nitric oxide-synthase system in vitro

Cardiovascular diseases are known as the major causes of death or disability in western countries. Decreased bioavailability of endothelial derived nitric oxide (NO) is recognized as an important promoter in cardiovascular disease. In vivo studies suggest that phytoestrogens, especially isoflavones from soy, enhance endothelium-dependent vasoreactivity. We hypothesized that isoflavones may affect the expression of endothelial-type nitric oxide synthase (eNOS) and thereby NO formation in vitro. Human EA.hy926 endothelial cells were treated with the soybean isoflavones biochanin A and formononetin and with their metabolites genistein and daidzein. eNOS promoter activity was examined by a luciferase reporter gene assay (20 h). Active eNOS was detected by quantifying conversion of L-arginine to L-citrulline and by measuring NO released from endothelial cells using the fluorescent probe DAF-2 (20-96 h).eNOS promoter activity increased in response to isoflavone treatment (20 h). NO and L-citrulline production by EA.hy926 cells rose up to 1.7-fold of control levels after stimulation with genistein for 48-96 h. From these results, we conclude that the suggested positive effects of soy isoflavones on vascular reactivity may be indeed mediated via a long-term effect on the eNOS system.

Polyphenols and prevention of cardiovascular diseases

PURPOSE OF REVIEW

Polyphenols are the most abundant dietary antioxidants and research on their role in the prevention of degenerative diseases has developed quickly over these last few years. This paper reviews the recent studies on the prevention of cardiovascular diseases by polyphenols, focusing on human studies.

RECENT FINDINGS

A large number of recent intervention studies have shown that several biomarkers of cardiovascular risk are influenced by the consumption of polyphenol-rich foods. Effects on biomarkers of oxidative stress, lipemia and inflammation appear so far inconclusive. More consistent effects have been observed on endothelial function and haemostasis and support a reduction of risk by polyphenols in agreement with the few epidemiological studies already published. All clinical studies have used foods or beverages containing a mixture of different polyphenols and the exact nature of the most active compounds remains largely unknown. Absorption, metabolism and elimination vary widely between polyphenols. These data on bioavailability should be taken into account to improve the experimental design and the interpretation of the observed effects.

SUMMARY

Future intervention studies should include a detailed assessment of the bioavailability of polyphenols. Beyond clinical trials carried out with polyphenol-rich foods, more studies with pure polyphenols will also be needed to establish their role in the prevention of cardiovascular diseases.

Soy, isoflavones and atherosclerosis

Consumption of soy protein is associated with a lower risk of cardiovascular disease in man, and reduced atherosclerosis in a variety of experimental animals. Although a portion of the cardiovascular protective effects appears to be due to reductions in plasma lipoprotein concentration, in most people the magnitude of this effect is relatively small. In many, but not all studies using animal models, the reduction in atherosclerosis is in part independent of changes in plasma lipids and lipoproteins. This implies that there may be a direct effect on the arterial wall of one or more of the components in soyprotein that reduces susceptibility to atherosclerosis. The most actively studied components of soy protein that may be responsible for these anti-atherogenic effects are the isoflavones and various protein factions. Extraction of isoflavones and other alcohol-soluble components from soy protein lowers, but does not eliminate its ability to reduce atherosclerosis. Surprisingly, in most studies, adding back the isoflavone-rich alcohol extract to the previously extracted soy protein, or to another protein, does not restore its lipoprotein lowering or anti-atherogenic properties. This implies that alcohol extraction either destroys an active component of soy, alters the structural integrity of the soy proteins, or disassociates a required isoflavone-soy protein complex. Understanding the mechanism of this effect is an important goal for future research. Likewise, the sites of action on the arterial wall, and the mechanisms by which various soy components act to reduce atherosclerosis are just now being studied. The recent demonstration that expression of estrogen receptor alpha is required for atheroprotection by soy protein provides important new mechanistic insight. Other properties of soy, including antioxidant, anti-inflammatory and potentially antithrombogenic properties need to be explored more mechanistically before the full potential of dietary soy protein for the protection from cardiovascular disease will be known.

Activation of nitric oxide synthesis in human endothelial cells by red clover extracts

OBJECTIVE

The unexpected findings of the Women's Health Initiative trial, where surrogate cardiovascular risk markers have failed to predict the cardiovascular performance of hormone therapy, showing no reduction of cardiovascular disease in postmenopausal women receiving hormonal preparations inducing a favorable lipid profile, raise the interest on how molecules with hormone-like activity used for the treatment of menopausal symptoms act on vascular cells. This is particularly important for estrogen-like compounds such as phytoestrogens, whose mechanisms of action may significantly differ from those of other estrogenic compounds.

DESIGN

Because endothelial-derived nitric oxide (NO) is a key regulator of vascular tone and atherogenesis as well as a well-characterized estrogen-regulated molecule, we studied the regulation of NO synthesis in cultured human endothelial cells by phytoestrogens contained in red clover extracts.

RESULTS

We show that red clover extracts activate NO synthesis in endothelial cells by recruiting transcriptional pathways but are not capable of inducing rapid NO synthesis through nongenomic mechanisms. During prolonged exposures, red clover extracts enhance the expression as well as the activity of endothelial nitric oxide synthase. These effects are mediated by a recruitment of estrogen receptor-beta. Moreover, we show that red clover-derived isoflavones synergize with 17beta-estradiol in increasing endothelial nitric oxide synthase activity and expression, therefore being devoid of antiestrogenic effects in human endothelial cells.

CONCLUSIONS

These results help to understand the mechanisms of action of phytoestrogens on the cardiovascular system and have relevant clinical implications.