A cooperative interaction between soy protein and its isoflavone-enriched fraction lowers hepatic lipids in male obese Zucker rats and reduces blood platelet sensitivity in male Sprague-Dawley rats

Molecular pharmacology of the onco-TRP channel TRPV6

TRPV6, a representative of the vanilloid subfamily of TRP channels, serves as the principal calcium uptake channel in the gut. Dysregulation of TRPV6 results in disturbed calcium homeostasis leading to a variety of human diseases, including many forms of cancer. Inhibitors of this oncochannel are therefore particularly needed. In this review, we provide an overview of recent advances in structural pharmacology that uncovered the molecular mechanisms of TRPV6 inhibition by a variety of small molecules, including synthetic and natural, plant-derived compounds as well as some prospective and clinically approved drugs.

Structural mechanism of human oncochannel TRPV6 inhibition by the natural phytoestrogen genistein

Calcium-selective oncochannel TRPV6 is the major driver of cell proliferation in human cancers. While significant effort has been invested in the development of synthetic TRPV6 inhibitors, natural channel blockers have been largely neglected. Here we report the structure of human TRPV6 in complex with the plant-derived phytoestrogen genistein, extracted from Styphnolobium japonicum, that was shown to inhibit cell invasion and metastasis in cancer clinical trials. Despite the pharmacological value, the molecular mechanism of TRPV6 inhibition by genistein has remained enigmatic. We use cryo-EM combined with electrophysiology, calcium imaging, mutagenesis, and molecular dynamics simulations to show that genistein binds in the intracellular half of the TRPV6 pore and acts as an ion channel blocker and gating modifier. Genistein binding to the open channel causes pore closure and a two-fold symmetrical conformational rearrangement in the S4-S5 and S6-TRP helix regions. The unprecedented mechanism of TRPV6 inhibition by genistein uncovers new possibilities in structure-based drug design.

Dietary isoflavones intake is inversely associated with non-alcoholic fatty liver disease, hyperlipidaemia and hypertension

This study investigated associations between total isoflavones and their categories (daidzein, genistein, glycitein) intake and the risks for metabolic disorders. We used the data of 6786 Chinese adults from the Nutrition Health Atlas Project. We performed multiple logistic regression and restricted cubic spline models assessing the risks for metabolic disorders (non-alcoholic fatty liver disease (NAFLD), hyperlipidaemia, hypertension, diabetes and overweight/obesity) in each category of isoflavones. Higher total isoflavones, daidzein and genistein intake were inversely associated with NAFLD (p < .05). Higher total isoflavones, daidzein, genistein and glycitein intake were also inversely associated with hyperlipidaemia (p < .01) and hypertension (p < .01). Dose-response analyses revealed that total isoflavones, daidzein, genistein and glycitein intakes were associated with the risks of metabolic disorders in a nonlinear trend. In conclusion, total isoflavones, daidzein and genistein intake were inversely associated with NAFLD, hyperlipidaemia and hypertension. Glycitein was inversely associated with hyperlipidaemia and hypertension.

In Vitro Antibacterial Effect of the Methanolic Extract of the Korean Soybean Fermented Product Doenjang against Staphylococcus aureus

Simple Summary

The emergence of bacterial antibiotic resistance is a negative phenomenon occurring worldwide in both animals and humans. The EU banned the use of antibiotic growth promoters in animal production, as their administration to livestock is assumed to substantially contribute to the spread of bacterial resistance. Therefore, alternatives to antibiotic substances are needed to maintain the quality and quantity of animal products. Certain plant materials, such as fermented soybean products, can serve as a source of substances with potential to decrease the growth of resistant bacteria, such as Staphylococcus aureus. Fermented soybean products, including doenjang, are known to contain natural phytoestrogens called isoflavones, which are especially interesting due to their antimicrobial activity; these products can also be utilized in animal feed. Thus, the antibacterial activity of the methanolic extract of the Korean soybean fermented product doenjang was evaluated using standardized microbiological methods against nine strains of resistant and sensitive S. aureus, including those occurring in animals. The extract has been shown to be active at a concentration range of 2048–4096 µg/mL against all tested S. aureus strains and can therefore serve as a promising alternative to antibiotics in animal feed after additional testing in the laboratory and on living animals.

Abstract

Ultra-high performance liquid chromatography/mass spectrometry showed soyasaponin I and the isoflavones daidzein, genistein, and glycitein to be the main components of the methanolic extract of the Korean soybean fermented product doenjang, which is known to be a rich source of naturally occurring bioactive substances, at average contents of 515.40, 236.30, 131.23, and 29.00 ng/mg, respectively. The antimicrobial activity of the methanolic extract of doenjang against nine Staphylococcusaureus strains was determined in vitro by the broth microdilution method to investigate its potential to serve as an alternative antibacterial compound. The results suggest that the extract is an effective antistaphylococcal agent at concentrations of 2048–4096 µg/mL. Moreover, the tested extract also showed the ability to inhibit the growth of both methicillin-sensitive and methicillin-resistant animal and clinical S. aureus isolates. The growth kinetics of the chosen strains of S. aureus at the minimum inhibitory concentration of the methanolic extract of doenjang support the idea that the tested extract acts as an antibacterial compound. To the best of our knowledge, this is the first report on the antistaphylococcal action of the methanolic extract of doenjang thus, additional studies including in vivo testing are necessary to confirm this hypothesis.

Miso (Fermented Soybean Paste) Suppresses Visceral Fat Accumulation in Mice, Especially in Combination with Exercise

We investigated whether the difference in miso consumption between the Japanese diets of 1975 and 2010 has influenced the observed increase in diet-induced obesity. To recreate the 2010 and 1975 Japanese high-fat diets with the corresponding proportions of miso, freeze-dried miso was added to high-fat mouse feed at 1.6% and 2.6%, respectively. When 5-week-old male Institute of Cancer Research (ICR) mice were provided each of these diets ad libitum for 8 weeks, it was found that the white adipose tissue weight and adipocyte area were lower in mice receiving the 1975 diet than in those receiving the 2010 diet. Therefore, high miso consumption is one reason why the 1975 Japanese diet tended to not lead to obesity. Next, the combined effects of treadmill exercise and miso consumption were investigated. The mice were divided into three groups, which were provided either a high-fat diet (group C), a high-fat diet with exercise (group C + E), or a miso-supplemented high-fat diet with exercise (group M + E) for 8 weeks. In this experiment, the white adipose tissue weight and adipocyte area in group M + E were lower than in group C. When the mRNA expression of lipid metabolism-associated genes in adipose tissue was measured, we found that expression of Hsl (lipase, hormone sensitive), which is involved in lipolysis, and Pparγ (peroxisome proliferator activated receptor gamma), which regulates adipocyte differentiation upstream of Hsl, was increased in group M + E. These results clearly demonstrated that lipid accumulation in the adipose tissues is suppressed by miso consumption in combination with exercise.

Short-Term Soy Protein Isolate Feeding Prevents Liver Steatosis and Reduces Serum ALT and AST Levels in Obese Female Zucker Rats

Non-alcoholic fatty liver disease is a common liver disorder worldwide and is associated with obesity. We investigated effects of obesity and short-term intake of soy protein with isoflavones (SPI) on body weight change, energy intake, liver steatosis, and serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), and leptin levels. Seventeen lean and seventeen obese (fa/fa) female Zucker rats were randomly assigned to either casein or SPI diet for 8 weeks. Body weight was recorded twice weekly; feed intake was measured weekly. Livers were examined histologically, and serum AST, ALT, and leptin levels were measured. Obese soy-fed (OS) rats gained more weight but had lower liver steatosis than obese casein-fed (OC) rats. Energy intake for OS versus OC rats were only different at weeks 2 and 3. Serum AST and ALT levels were lower in OS versus OC rats. Obesity increased serum leptin levels for both diets. In summary, short-term SPI intake reduced liver steatosis, and the only time points at which the mean energy intakes of OS and OC rats differed were at weeks 2 and 3, where OS rats had a higher mean energy intake, which may have accounted for the increased body weight in OS rats.

Lifelong exposure to dietary isoflavones reduces risk of obesity in ovariectomized Wistar rats

SCOPE

Traditional Asian diet rich in soy isoflavones (ISOs) is discussed to be linked to a lower obesity prevalence. In lifelong and short-term exposure scenarios we investigated effects of an ISO-rich diet on the body composition and development of obesity in female rats.

METHODS AND RESULTS

Female Wistar rats grew up on ISO-free or ISO-rich control diet (CON ISO: 467 mg/kg diet). Starting postnatal day 83, ovariectomized and intact animals received high calorie Western diet (WD) in the absence or presence of ISO (WD ISO: 431 mg/kg diet) for 12 weeks to induce obesity or maintained on respective control diet (CON). One group starting ISO exposure after ovariectomy mimics short-term ISO exposure in postmenopausal Western women. Lifelong but not short-term ISO exposure resulted in reduced body weight, visceral fat mass, serum leptin, and smaller adipocytes. ISO decreased hepatic SREBP-1c, ACC, FAS, and PPARγ mRNA expression in nonobese animals. Moreover, ovariectomy reduced skeletal muscle weight, which was antagonized by both short-term and lifelong ISO exposure.

CONCLUSION

Our results indicate that in female rats lifelong but not short-term ISO intake reduces the risk to develop obesity. Furthermore, lifelong and short-term ISO exposure may antagonize loss of skeletal muscle mass induced by ovariectomy.

Soy Protein Suppresses Gene Expression of Acetyl-CoA Carboxylase Alpha from Promoter PI in Rat Liver

Dietary soy protein isolate (SPI) reduces hepatic lipogenesis by suppressing gene expression of lipogenic enzymes, including acetyl-CoA carboxylase (ACC). In order to elucidate the mechanism of this regulation, the effect of dietary SPI on promoter (PI and PII) specific gene expression of ACC alpha was investigated. Rats were fed experimental diets containing SPI or casein as a nitrogen source. SPI feeding decreased the hepatic contents of total ACC mRNA as well as triglyceride (TG) content, but dietary SPI affected the amount of sterol-regulatory element binding protein (SREBP)-1 mRNA and protein very little. The amount of ACC mRNA transcribed from PII promoter containing SRE was not significantly affected by dietary protein, while a significant decrease in PI-generated ACC mRNA content was observed in rats fed the SPI diet. These data suggest that SPI feeding decreased the hepatic contents of ACC alpha mRNA mainly by regulating PI promoter via a nuclear factor(s) other than SREBP-1.

Dietary modification of metabolic pathways via nuclear hormone receptors

Nuclear hormone receptors (NHRs), as ligand-dependent transcription factors, have emerged as important mediators in the control of whole body metabolism. Because of the promiscuous nature of several members of this superfamily that have been found to bind ligand with lower affinity than the classical steroid NHRs, they consequently display a broader ligand selectivity. This promiscuous nature has facilitated various bioactive dietary components being able to act as agonist ligands for certain members of the NHR superfamily. By binding to these NHRs, bioactive dietary components are able to mediate changes in various metabolic pathways, including, glucose, cholesterol and triglyceride homeostasis among others. This review will provide a general overview of the nuclear hormone receptors that have been shown to be activated by dietary components. The physiological consequences of such receptor activation by these dietary components will then be discussed in more detail.

Effect of soy protein supplementation in patients with chronic hepatitis C: a randomized clinical trial

AIM

To evaluate the effects of soy supplementation on insulin resistance, fatty liver and alanine aminotransferase (ALT) levels in non-diabetic patients with chronic hepatitis C (CHC).

METHODS

In a prospective, randomized and single-blinded clinical trial, we compared patients with CHC who had casein as a supplement (n = 80) (control group), with patients who consumed a soy supplement diet (n = 80) [intervention group (IG)]. Both groups received 32 g/d of protein for 12 wk.

RESULTS

Patients' baseline features showed that 48.1% were overweight, 43.7% had abdominal fat accumulation, 34.7% had hepatic steatosis and 36.3% had an homeostasis model assessment index of insulin resistance (HOMA-IR) ≥ 3.0. Descriptive analysis showed that protein supplementation diet reduced hepatic steatosis in both groups; however, significant reductions in ALT levels occurred in the soy group. Multiple regression modeling indicated that in the presence of severe fibrosis (F3/F4), γ glutamyl transferase elevation and high density lipoprotein (HDL) reduction, the intervention group had 75% less chance of developing hepatic steatosis (OR= 0.25; 95% CI: 0.06-0.82) and 55% less chance of presenting with an ALT level ≥ 1.5 × the upper limit of normal (ULN) (OR = 0.45, 95% CI: 0.22-0.89). Soy treatment did not have any effect on insulin resistance (OR = 1.92; 95% CI: 0.80-4.83), which might be attributed to the fact that the HOMA-IR values at baseline in most of our patients were in the normal range. Advanced hepatic fibrosis, an ALT level > 1.5 × ULN and visceral fat were predictors of an HOMA-IR ≥ 3. The IG group had a reduced risk of an ALT level > 1.5 × ULN. An HOMA-IR ≥ 3.0 and HDL < 35 mg/dL were also risk factors for increased ALT.

CONCLUSION

Soy supplementation decreased ALT levels and thus may improve liver inflammation in hepatitis C virus (HCV) patients; it also reduced hepatic steatosis in a subgroup of patients but did not change insulin resistance. It should be considered in the nutritional care of HCV patients.

Preliminary investigation of the effects of long-term dietary intake of genistein and daidzein on hepatic histopathology and biochemistry in domestic cats (Felis catus)

Dietary isoflavones have been hypothesised to play a role in hepatic veno-occlusive disease in captive exotic felids, although empirical evidence is lacking. This study aimed to investigate the effect of long-term (>1 year) dietary genistein and daidzein exposure on the hepatic biochemistry and histology of domestic cats. Individual cats were assessed for hepatic enzyme and bile acid production before and after the removal of isoflavones from their diet in the treatment group (n = 4), and at the same times in unexposed control animals (n = 7). No significant differences were detectable in hepatic biochemistry between treatment and control groups, and all serum values were within the normal reference ranges for domestic cats. Additionally, treatment animals demonstrated slightly greater areas of fibrosis surrounding hepatic venules than control animals, but this difference was not statistically significant. On the basis of the results presented, dietary isoflavones, at the current dose and duration of exposure do not appear to modulate hepatic enzyme production or histological parameters.

Doenjang, a fermented soybean paste, decreased visceral fat accumulation and adipocyte size in rats fed with high fat diet more effectively than nonfermented soybeans

Soybean is known to have an anti-obesity effect. We compared the anti-obesity effect of doenjang, a fermented soybean paste, with that of nonfermented soybeans in rats. Steamed soybeans and doenjang (steamed soybeans fermented and aged for 10 months) were sampled and freeze-dried. Male Sprague-Dawley rats were fed basal (BA) (5% fat), high fat (HF) (30% fat), HF+steamed soybeans (SOY), or HF+doenjang (DJ) diet ad libitum for 8 weeks. HF significantly increased body weight gain, liver weight, hepatic triglyceride (TG) and cholesterol levels, and epididymal fat pad weight compared with BA. Compared with HF, body weight gain and hepatic TG and cholesterol levels were significantly lower in SOY and DJ groups, but they were not significantly different from each other. DJ significantly reduced visceral fat weight and epididymal adipocyte size compared with HF, whereas SOY resulted in a mild reduction without significance. This was possibly because DJ showed lowered fatty acid synthase (FAS) activity and elevated carnitine palmitoyltransferase (CPT)-1 activity in liver tissue more than SOY. SOY and DJ did not affect serum total and high-density lipoprotein-cholesterol levels compared with HF; however, DJ significantly lowered the atherogenic index and serum leptin level. In conclusion, doenjang, a fermented soybean product, was more effective than soybeans for preventing diet-induced visceral fat accumulation, possibly because of its greater effects on CPT-1 activity stimulation and FAS activity suppression. These effects may be due in part to the higher content of aglycone isoflavones in doenjang.

Tofu (soybean curd) lowers serum lipid levels and modulates hepatic gene expression involved in lipogenesis primarily through its protein, not isoflavone, component in rats

Although soy foods are recommended to prevent hyperlipidemia and related diseases, it is unclear how their active ingredients exert their effects. Here, the effects of tofu (soybean curd) and its putative active components, protein and isoflavone, on lipid metabolism in male rats were compared. Tofu and soy protein significantly lowered serum triacylglycerol and cholesterol levels compared to casein and, through microarray analyses, were found to exclusively alter transcriptomes involved in fatty acid and/or steroid synthesis in the liver, where most of the serum lipids are synthesized. In contrast, isoflavone supplementation had little effect on serum lipid levels or gene expression and exerted no synergistic effects with soy protein or tofu. The importance of the proteinaceous components was further confirmed by the lower activity of enzymes involved in lipogenesis. From these findings it was concluded that the protein, not isoflavone, fraction of soy reduces lipogenesis in liver through gene expression and that this may result in lower serum lipid levels.

Synthetic and natural iron chelators: therapeutic potential and clinical use

Iron-chelation therapy has its origins in the treatment of iron-overload syndromes. For many years, the standard for this purpose has been deferoxamine. Recently, considerable progress has been made in identifying synthetic chelators with improved pharmacologic properties relative to deferoxamine. Most notable are deferasirox (Exjade(®)) and deferiprone (Ferriprox(®)), which are now available clinically. In addition to treatment of iron overload, there is an emerging role for iron chelators in the treatment of diseases characterized by oxidative stress, including cardiovascular disease, atherosclerosis, neurodegenerative diseases and cancer. While iron is not regarded as the underlying cause of these diseases, it does play an important role in disease progression, either through promotion of cellular growth and proliferation or through participation in redox reactions that catalyze the formation of reactive oxygen species and increase oxidative stress. Thus, iron chelators may be of therapeutic benefit in many of these conditions. Phytochemicals, many of which bind iron, may also owe some of their beneficial properties to iron chelation. This review will focus on the advances in iron-chelation therapy for the treatment of iron-overload disease and cancer, as well as neurodegenerative and chronic inflammatory diseases. Established and novel iron chelators will be discussed, as well as the emerging role of dietary plant polyphenols that effectively modulate iron biochemistry.

Antihyperlipidemic effect of sesame (Sesamum indicum L.) protein isolate in rats fed a normal and high cholesterol diet

The dietary influence of sesame protein isolate (protein content 91.5%), produced from dehulled, defatted sesame meal, on blood and tissue lipid profile and lipid peroxidation has been assessed in normal and hypercholesterolemic rats. To evaluate their hypocholesterolemic and antioxidative activity in vivo, we fed 18% sesame protein isolate with or without 2% cholesterol in comparison with casein to rats for 28 d. We determined plasma total protein, total cholesterol, high-density lipoprotein (HDL)-cholesterol, low-density lipoprotein (LDL)-cholesterol, triacylglycerol as well as susceptibility of plasma and erythrocyte membrane lipid to oxidation ex vivo. Liver tissue lipid, cholesterol, phospholipids, and lipid peroxidations were also determined. The total cholesterol, LDL-cholesterol and triacylglycerol levels were significantly reduced in the sesame protein isolate and isolate containing cholesterol group than the corresponding control casein groups. HDL-cholesterol level was also increased in sesame protein isolate (41%) and protein isolate containing cholesterol group (38%) than the corresponding control casein and casein containing cholesterol groups. There was 49% and 64% lowering of plasma lipid peroxidation as well as 36% and 56% lowering of lipoprotein oxidation susceptibility (LOS) in the 2 experimental groups (sesame protein isolate and isolate containing cholesterol group) than the corresponding control (casein and casein containing cholesterol) groups. There was significant lowering of erythrocyte membrane lipid peroxidation (68% and 63% lowering in sesame protein isolate and isolate containing cholesterol groups) and liver lipid peroxidation (61% and 76% lowering in the 2 experimental groups than the corresponding control casein groups). Therefore, our results indicate that sesame protein isolate decreases cholesterol concentration in plasma, increases HDL-cholesterol, and also decreases plasma and erythrocyte membrane lipid peroxidation with or without cholesterol fed diet in rats.

Effects of soy isoflavone extract supplements on blood pressure in adult humans: systematic review and meta-analysis of randomized placebo-controlled trials

OBJECTIVE

Reported effects of different soy products on blood pressure vary. This systematic review and meta-analysis was performed to clarify the effects of soy isoflavone extract supplements on systolic and diastolic blood pressure (SBP and DBP) in adult humans.

METHODS

PubMed, CENTRAL, ICHUSHI, and CNKI were searched in June 2009 for relevant randomized placebo-controlled trials. Study data and indicators of methodological validity were independently extracted by two authors using predefined data fields. Meta-analysis was carried out in Review Manager 5.0.22.

RESULTS

Searches identified 3740 articles, of which 14 randomized controlled trials (789 participants) were included. Daily ingestion of 25-375 mg soy isoflavones (aglycone equivalents) for 2-24 weeks significantly decreased SBP by 1.92 mmHg (95% confidence interval -3.45 to -0.39; P = 0.01) compared with placebo (heterogeneity P = 0.39, fixed effect model) in adults with normal blood pressure and prehypertension. The effect was not lost on sensitivity analysis. Subgroup analyses suggest greater effects in studies longer than 3 months, in Western populations, at lower doses, and in studies at lower risk of bias. Soy isoflavones did not affect DBP [-0.13 (95% confidence interval -1.03 to 0.78) mmHg, P = 0.78; heterogeneity P = 0.20, fixed effect model].

CONCLUSION

Soy isoflavone extracts significantly decreased SBP but not DBP in adult humans, and no dose-response relationship was observed. Further studies are needed to address factors related to the observed effects of soy isoflavones on SBP and to verify the effect in hypertensive patients.

Analytical and compositional aspects of isoflavones in food and their biological effects

This paper provides an overview of analytical techniques used to determine isoflavones (IFs) in foods and biological fluids with main emphasis on sample preparation methods. Factors influencing the content of IFs in food including processing and natural variability are summarized and an insight into IF databases is given. Comparisons of dietary intake of IFs in Asian and Western populations, in special subgroups like vegetarians, vegans, and infants are made and our knowledge on their absorption, distribution, metabolism, and excretion by the human body is presented. The influences of the gut microflora, age, gender, background diet, food matrix, and the chemical nature of the IFs on the metabolism of IFs are described. Potential mechanisms by which IFs may exert their actions are reviewed, and genetic polymorphism as determinants of biological response to soy IFs is discussed. The effects of IFs on a range of health outcomes including atherosclerosis, breast, intestinal, and prostate cancers, menopausal symptoms, bone health, and cognition are reviewed on the basis of the available in vitro, in vivo animal and human data.

Acidic peptides enhanced genistein-dependent inhibition of human platelet aggregation: potential protective effect of digestible peptides plus genistein against atherosclerosis

The leading cause of death in the United States and European countries is coronary heart disease. We hypothesized that the ingestion of soy compounds may not only have beneficial effects on atherosclerotic risk by lowering lipid compounds, but also by reducing platelet aggregability. Therefore, we analyzed in vitro the influence of defined and digestible peptides, frequently found in glycinin and beta-conglycinin as important proteins of soy bean, on platelet aggregation of 180 healthy volunteers with or without the isoflavone genistein by aggregometry and flow cytometry. (i) The predominating share of amino acids and acidic, neutral, and basic di- and tripeptides of up to 2 mmol/L did not modify platelet aggregation induced by collagen, adenosine diphosphate, epinephrine, or arachidonic acid. (ii) Genistein inhibited agonist-induced platelet aggregation dose dependently. (iii) In the presence of the acidic peptides glutamate-glutamate and aspartate-aspartate-aspartate (1 mmol/L each), genistein reduced collagen- and ADP-dependent platelet activation stronger than 250 micromol/L of this isoflavone alone. Other peptides were less effective (eg, glutamate-glutamate-glutamate) or ineffective (eg, asparagine-asparagine). (iv) Glutamate-glutamate-glutamate (1 nmol/L), glutamate-glutamate (1 micromol/L), and aspartate-aspartate-aspartate (1 micromol/L) enhanced the inhibition of genistein on platelet aggregation induced by arachidonic acid. Thus, the results of the present in vitro investigation allow the assumption that nutrition with specific compounds of soy--acidic peptides together with genistein--might protect against coronary atherosclerosis by attenuating platelet activity. In vivo studies are warranted to check this assumption.

Effects of a ferment soy product on the adipocyte area reduction and dyslipidemia control in hypercholesterolemic adult male rats

BACKGROUND

Available data on the effects of a fermented soy product enriched with Enterococcus faecium and Lactobacillus Jugurti on circulating lipids and adiposity are not completely settled. This study aimed to observe the effects of a fermented soy product enriched with Enterococcus faecium and Lactobacillus Jugurti on central obesity and dyslipidemia control in Wistar adult male rats.

METHODS

Over a period of 8 weeks, animals had "ad libitum" food intake and water consumption as well as body weight and food consumption was monitored. The animals were assigned to four different experimental groups: Control Group (C); Control + Fermented Product Group (CPF); Hypercholesterolemic diet group (H); and Hypercholesterolemic + Fermented Product Group (HPF). The HPF and CPF groups received an intragastric administration of 1 ml of fermented product daily. After the experimental period the animals were killed by decapitation, blood was collected to measure cholesterol, triglycerides and HDL-cholesterol plasma concentration. Adipocyte circumference, lipolysis and lipogenis rates were measures using epididymal and retroperitoneal white adipose tissues.

RESULTS

The results demonstrated that 1 ml/day/rat of the fermented soy product promoted important benefits such as reduced cholesterolemia in hypercholesterolemic diet group and the adipocyte circumference in both control and hypercholesterolemic diet group.

CONCLUSION

The fermented soy product enriched with Enterococcus faecium and Lactobacillus Jugurti decreased circulating lipids levels and reduced adipocyte area in rats.

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.

Soy protein and isoflavones influence adiposity and development of metabolic syndrome in the obese male ZDF rat

BACKGROUND/AIMS

Previously, we demonstrated that soy protein ameliorates the diabetic phenotype in several rodent models of obesity and metabolic syndrome (MS). This study was designed to further elucidate factors related to adiposity, glycemic control, and renal function in male Zucker Diabetic Fatty (ZDF/Lepr(fa)) rats.

METHODS

Animals were randomly assigned to one of four diets: control, casein (C); low isoflavone (LIS) soy protein; high isoflavone (HIS) soy protein, or casein + rosiglitazone (CR) for 11 weeks. At sacrifice, physiological, biochemical, and molecular parameters were determined.

RESULTS

Body weight and total adiposity were higher in LIS and CR diet groups despite lower food intake. Additionally, these animals exhibited differential regulation of adipose-specific proteins (PPAR-gamma and GLUT4) and enzyme activity (FAS and GPDH). HIS-fed animals had reduced total and liver adiposity. Glycemic control was prolonged in both soy-based and rosiglitazone (RGZ) groups. Renal dysfunction was significantly reduced in soy-fed and RGZ-treated rodents as demonstrated by lower levels of proteinuria and dilated tubules with proteinaceous casts.

CONCLUSION

Collectively, these data provide evidence that soy protein with low or high isoflavone content may have therapeutic significance in reducing severity of diabetes, MS, and renal disease as demonstrated in this preclinical model.

Dietary proteins with high isoflavone content or low methionine–glycine and lysine–arginine ratios are hypocholesterolaemic and lower the plasma homocysteine level in male Zucker fa/fa rats

It has previously been demonstrated that soya protein, which contains isoflavones and low methionine–glycine and lysine–arginine ratios, has a hypocholesterolaemic effect. In the present study, the hypocholesterolaemic effects of an isoflavone-enriched casein diet (HDI) and a single-cell protein-based diet (SCP) devoid of isoflavones but with low methionine–glycine and lysine–arginine ratios were investigated in obese Zucker rats after 6 weeks of feeding. The control diet contained casein, which has high ratios of methionine–glycine and lysine–arginine. HDI and SCP feeding reduced the concentrations of total cholesterol and cholesteryl esters in plasma and liver, and changed the fatty acid composition of the hepatic cholesteryl esters. Faecal cholesterol and bile acid levels were markedly higher in SCP-fed rats than in controls, whereas HDI feeding had only minor effects. However, both HDI and SCP feeding increased the hepatic gene expression of cholesterol 7α hydroxylase. In contrast, the hepatic acyl-CoA synthetase and acyl-CoA:cholesterol acyltransferase activities and the gene expression of the LDL receptor were increased by HDI, but not by SCP feeding. The present results suggested that the cholesterol-lowering effect of SCP was related to the enterohepatic circulation, whereas HDI seemed to lower the plasma cholesterol via the circulation. Plasma homocysteine level was reduced in rats fed HDI and SCP compared to rats fed casein. In summary, diets enriched in isoflavones or containing proteins with low methionine–glycine and lysine–arginine ratios lowered the plasma cholesterol and homocysteine levels, changing the plasma profile from atherogenic to cardioprotective.

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.

Dietary soya protein concentrate enriched with isoflavones reduced fatty liver, increased hepatic fatty acid oxidation and decreased the hepatic mRNA level of VLDL receptor in obese Zucker rats

Casein-based diets containing a low (LDI) or high (HDI) dose of soya protein concentrate enriched with isoflavones were fed to obese Zucker rats for 6 weeks. HDI feeding, but not LDI feeding, reduced the fatty liver and decreased the plasma levels of alanine transaminase and aspartate transaminase. This was accompanied by increased activities of mitochondrial and peroxisomal beta-oxidation, acetyl-CoA carboxylase, fatty acid synthase and glycerol-3-phosphate acyltransferase in liver and increased triacylglycerol level in plasma. The decreased fatty liver and the increased plasma triacylglycerol level appeared not to be caused by an increased secretion of VLDL, as HDI decreased the hepatic mRNA levels of apo B and arylacetamide deacetylase. However, the gene expression of VLDL receptor was markedly decreased in liver, but unchanged in epididymal white adipose tissue and skeletal muscle of rats fed HDI, indicating that the liver may be the key organ for the reduced clearance of triacylglycerol-rich lipoproteins from plasma after HDI feeding. The n-3/n-6, 20:4n-6/18:2n-6 and (20:5n-3+22:6n-3)/18:3n-3 ratios were increased in liver triacylglycerol by HDI. The phospholipids in liver of rats fed HDI contained a low level of 20:4n-6 and a high level of 20:5n-3, favouring the production of anti-inflammatory eicosanoids. When obese Zucker rats were fed soya protein, this also resulted in reduced fatty liver, possibly through reduced clearance of VLDL by the liver. We conclude that the isoflavone-enriched soya concentrate as well as soya protein may be promising dietary supplements for treatment of non-alcoholic fatty liver.

Effect of proteins from beef, pork, and turkey meat on plasma and liver lipids of rats compared with casein and soy protein

OBJECTIVE

We assessed the effect of dietary proteins isolated from beef, pork, and turkey meat on concentrations of cholesterol and triacylglycerols in plasma, lipoproteins, and liver and the composition of the microsomal membrane (fatty acids, phosphatidylcholine/phosphatidylethanolamine ratio) compared with that of casein and soy protein in rats.

METHODS

Five groups of 12 rats each were fed semisynthetic diets for 20 d that contained 200 g/kg of proteins isolated from beef, pork, or turkey meat or, as controls, casein or soy protein.

RESULTS

Rats fed beef, pork, or turkey proteins did not differ in cholesterol concentrations of plasma, lipoproteins, and liver and in composition of microsomal membrane from rats fed the casein diet. All groups fed a protein from an animal source had higher very low-density lipoprotein (VLDL) and liver cholesterol concentrations than did rats fed soy protein. However, rats fed pork protein had lower concentrations of triacylglycerols in liver, plasma, and VLDL and lower mRNA concentrations of sterol regulatory element binding protein-1 and glucose-6-phosphate dehydrogenase than did rats fed casein. However, concentrations of plasma and VLDL triacylglycerols in rats fed pork protein were not as low as those observed in rats fed soy protein.

CONCLUSION

Proteins isolated from beef, pork, or turkey meat do not differ from casein in their effects on cholesterol metabolism. Pork protein decreases plasma triacylglycerol concentrations compared with casein but not compared with soy protein. The triacylglycerol-lowering effect of pork protein compared with casein is suggested to be caused by decreased hepatic fatty acid synthesis.

Lowering effect of an isoflavone-rich fermented soybean extract on the serum cholesterol concentrations in female rats, with or without ovariectomy, but not in male rats

We examined the effect of administering an isoflavone-rich fermented soybean extract (FSBE) on the serum cholesterol concentrations in male rats and in intact and ovariectomized (OVX) female rats. Dietary FSBE decreased the serum cholesterol concentrations in intact female and OVX rats, but did not affect the concentrations in male rats. Dietary FSBE increased the hepatic total and esterified cholesterol contents in the intact female rats, but decreased them in the OVX rats. This hypocholesterolemic effect was not a simple estrogenic effect because it has appeared in some reports that estrogen administration decreased serum cholesterol both male and female rats. Dietary FSBE increased the hepatic low-density lipoprotein receptor (LDLR) gene expression in the intact female rats as has previously been reported from many studies, but did not affect that of the OVX rats. Further investigation is needed into the hypocholesterolemic mechanism of FSBE.

A multi-analytical platform approach to the metabonomic analysis of plasma from normal and zucker (fa/fa) obese rats

Plasma obtained from 20 week old normal Wistar-derived and Zucker (fa/fa) rats was analysed using a number of different analytical methodologies to obtain global metabolite profiles as part of metabonomic investigations of animal models of diabetes. Samples were analysed without sample pre-treatment using 1H NMR spectroscopy, after acetonitrile solvent protein precipitation by ultra-performance liquid chromatography-MS (UPLC-MS) and after acetonitrile protein precipitation and derivatisation for capillary gas chromatography-MS (GC-MS). Subsequent data analysis using principal components analysis revealed that all three analytical platforms readily detected differences between the plasma metabolite profiles of the two strains of rat. There was only limited overlap between the metabolites detected by the different methodologies and the combination of all three methods of metabolite profiling therefore provided a much more comprehensive profile than would have been provided by their use individually.

A metabonomic analysis of plasma from Zucker rat strains using gas chromatography/mass spectrometry and pattern recognition

Plasma obtained from three strains of Zucker rats was analysed using capillary gas chromatography/mass spectrometry (GC/MS) to obtain global metabolite profiles as part of a series of metabonomic investigations of animal models of diabetes. Samples were obtained from 20-week-old male wild-type Zucker lean, (fa/fa) obese and lean/(fa) animals and were analysed following protein precipitation, using acetonitrile, and derivatisation. Subsequent data analysis using principal components analysis (PCA) and orthogonal projection to latent structures (OPLS) revealed differences between the plasma metabolite profiles of the three strains, with those of the Zucker lean and the lean/(fa) crosses being similar to each other whilst differing from the (fa/fa) obese strain.

Gene expression and adiposity are modified by soy protein in male Zucker diabetic fatty rats

It has earlier been demonstrated that soy protein diets ameliorate the diabetic phenotype in obese Zucker rats. In this study, we further investigated physiological changes related to adiposity in male Zucker diabetic fatty rats consuming soy-based diets and compared these diets with the insulin-sensitizing drug, rosiglitazone. Transcript abundance of known genes was assessed in the livers to identify potential molecular connections between soy diets and adiposity. Male Zucker diabetic fatty rats were assigned to casein (C) protein, low-isoflavone soy (LIS) protein, high-isoflavone soy (HIS) protein, or C + rosiglitazone (CR) diets. Compared with the C diet, the LIS diet decreased plasma lipids and increased body weight, but did not change liver weight or carcass adiposity. HIS decreased plasma lipids, liver weight, and body weight. CR decreased plasma lipids and increased carcass adiposity and body weight with no effect on liver weight. In LIS livers, 15 genes involved in signaling and lipid metabolism were up-regulated 2-fold or higher. In HIS livers, seven genes had a 2-fold or higher change in abundance. However, in CR livers, none of the genes was significantly changed compared with the C diet. There appears to be a distinct change in gene expression associated with soy diets as compared with C-based diets and rosiglitazone treatment.

Subdiaphragmatic vagal deafferentation affects body weight gain and glucose metabolism in obese male Zucker (fa/fa) rats

We investigated the effect of subdiaphragmatic vagal deafferentation (SDA) on food intake, body weight gain, and metabolism in obese (fa/fa) and lean (Fa/?) Zucker rats. Before and after recovery from surgery, food intake and body weight gain were recorded, and plasma glucose and insulin were measured in tail-prick blood samples. After implantation of a jugular vein catheter, an intravenous glucose tolerance test (IVGTT) was performed, followed by minimal modeling to estimate the insulin sensitivity index. Food intake relative to metabolic body weight (g/kg(0.75)) and daily body weight gain after surgery were lower (P < 0.05) in SDA than in sham obese but not lean rats. Before surgery, plasma glucose and insulin concentrations were lower (P < 0.05) in lean than in obese rats but did not differ between surgical groups within both genotypes. Four weeks after surgery, plasma glucose and insulin were still similar in SDA and sham lean rats but lower (P < 0.05) in SDA than in sham obese rats. IVGTT revealed a downward shift of the plasma insulin profile by SDA in obese but not lean rats, whereas the plasma glucose profile was unaffected. SDA decreased (P < 0.05) area under the curve for insulin but not glucose in obese rats. The insulin sensitivity index was higher in lean than in obese rats but was not affected by SDA in both genotypes. These results suggest that elimination of vagal afferent signals from the upper gut reduces food intake and body weight gain without affecting the insulin sensitivity index measured by minimal modeling in obese Zucker rats.

Effects of soy isoflavones on endothelial function in healthy postmenopausal women

OBJECTIVE

To evaluate the effects of soy isoflavone administration on endothelial function in healthy postmenopausal women.

DESIGN

Sixty naturally postmenopausal women were randomly assigned to receive isoflavone or placebo tablets for 6 months. Endothelium-dependent vasodilatation was measured by brachial reactivity technique along with levels of plasma soluble intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), E-selectin, P-selectin and soluble thrombomodulin, von Willebrand factor, and tissue plasminogen activator. Differences between endothelium-dependent and endothelium-independent vasodilatation were assessed by evaluating brachial reactivity parameters after reactive hyperemia and after sublingual administration of nitroglycerin; furthermore, in the active group, the effect of isoflavones was also evaluated during the intra-arterial infusion of N-monomethyl-L-arginine. Serum levels of lipids [high-density lipoprotein and low-density lipoprotein cholesterol, triglycerides and lipoprotein(a)] and hemostatic factors (prothrombin, fibrinogen, plasminogen activator inhibitor-1, and fibrin D-dimer) were also measured. To confirm the absorption of isoflavones, their blood concentrations were determined.

RESULTS

Isoflavone treatment versus placebo was associated with a significant improvement in endothelium-dependent vasodilatation but had no impact on endothelial-independent arterial diameter and flow. Intra-arterial infusion of N-monomethyl-L-arginine inhibited the significant effect of isoflavones on endothelium-mediated vasodilatation. Furthermore, isoflavone group experienced statistically significant reductions in plasma concentrations of ICAM-1, VCAM-1, and E-selectin. Levels of soluble thrombomodulin, von Willebrand factor, tissue plasminogen activator, lipids, and hemostatic factors did not change significantly throughout the study in both groups.

CONCLUSIONS

Our findings suggest a positive influence of soy isoflavones on endothelial function in healthy postmenopausal women as evidenced by an improvement in endothelium-dependent vasodilatation and a reduction in plasma adhesion molecule levels.

Comparison of regulative functions between dietary soy isoflavones aglycone and glucoside on lipid metabolism in rats fed cholesterol

The effects of dietary soy isoflavones aglycone and glucoside on lipid metabolism were compared in male Sprague-Dawley rats (4 weeks old) given purified diets containing 0.3% cholesterol. The rats were fed a diet supplemented with either isoflavone aglycone-rich powder (IF-A group) or isoflavone glucoside-rich powder (IF-G group) or isoflavone-free diet (control group) for 40 days. The additional level of isoflavone aglycone moiety in the diet was prepared to the same level (approximately 0.096 g/100 g: approximately 0.1% in diet). The activity of hepatic cholesterol 7alpha-hydroxylase tended to be slightly higher in the rats fed isoflavones than in those fed the isoflavone-free diet. On the other hand, the activity of hepatic Delta6 desaturase in the IF-A group was lower than that of the control group. Reflecting this effect, the Delta6 desaturation indices [(20:3n-6+20:4n-6)/18:2n-6] in liver phospholipids of the IF-A group were lower than those in the control group. Liver and serum total cholesterol levels and liver TG level were also reduced by consumption of isoflavone aglycone. Moreover, serum TG level was lowered by consumption of both isoflavones aglycone and glucoside. The level of serum total isoflavones in the IF-A group was significantly higher than that in the IF-G group. Therefore, we speculate that the absorption speed of isoflavone aglycones might be faster than that of isoflavone glucosides in rats. This study suggests that dietary soy isoflavones, particularly their aglycone form, may exert a beneficial effect on lipid metabolism in rats fed cholesterol.

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.

Soy Isoflavones Modify Liver Free Radical Scavenger Systems and Liver Parameters in Sprague–Dawley Rats

Soyfoods contain estrogenic isoflavones--namely, genistein (G) and daidzein (D)--that, like estrogens, display physiological effects in humans and animals. Previously we and others have demonstrated antioxidant and cardioprotective effects of orally ingested soy diets and soy isoflavones. The overall objective of this study was to test the effects of injected soy isoflavones, G and D, on liver lipids, liver free radical scavenger systems, and parameters of cardiovascular risk. Forty male rats were injected with G, D, estradiol (E), or a vehicle control (V) for 6 weeks. At the end of the study, body weight, food intake, feed efficiency ratio (FER), plasma glucose and cholesterol, abdominal fat pad weight, reproductive organ weight, liver weight, liver lipids, and liver free radical scavenger systems were compared. Food intake was significantly (P < .04) higher in the D-, G-, and E-treated animals compared with V-treated animals. FER was lower (P < .001) in D-, G-, and E-treated animals compared with the V- and the E-treated animals. Body weight, testis weight, and prostate weight were markedly (P < .001) lower in the E-treated animals compared with D-, G-, and V-treated animals. Intraabdominal fat pad weights were also significantly (P < .001) lower in the E group, although this effect was lost when corrected for body weight. Liver weights were considerably lower in the D-, G-, and E-treated animals versus the V group (P < .001). Total plasma cholesterol was reduced (P < .05) in D- and E-treated animals versus the V group. Liver lipids appeared to be unchanged by the isoflavones and slightly elevated by E treatment (P < .02). Liver catalase levels were numerically higher in the D- and E-treated animals compared with the V group (P < .1). Similarly, Cu/Zn superoxide dismutase (SOD) activity was significantly elevated in the D and E groups (P < .01), while G treatment (P < .03) elevated SOD to a lesser degree, versus the V group. These results suggest that subcutaneous injections of the naturally occurring soy isoflavone D and, to a lesser extent, G exert cardioprotective effects and stimulate antioxidant systems, while minimizing the undesirable effects elicited by E treatment.

Soyabean protein hydrolysate prevents the development of hypertension in spontaneously hypertensive rats

The aim of the present study was to investigate the anti-hypertensive and angiotensin-converting enzyme (ACE) inhibition effects of soyabean protein hydrolysate in spontaneously hypertensive rats (SHR). Soyabean protein hydrolysate was prepared by peptic hydrolysis and was added into the feed of SHR (0% for the S0 group, 0.5% for the S1 group, and 1% for the S2 group) for 12 weeks. Systolic blood pressure and mean blood pressure of the S1 (164.3 (sem 4.7); 128.0 (sem 5.0) mmHg) and S2 (156.8 (sem 1.6); 120.8 (sem 3.4) mmHg) groups were significantly lower than those of the S0 group (199.4 (sem 5.2); 158.3 (sem 7.0) mmHg) at the end of the study. In the analysis of ACE activity, plasma and heart ACE activities of the S1 and S2 groups were significantly lower than those of the S0 group, and there were no significant differences in aorta, kidney, and lung ACE activities among all SHR. Soyabean protein hydrolysate had no significant effect on plasma lipids, electrolytes, or on left ventricular wall or aorta wall thickness. The results suggest that the long-term administration of soyabean protein hydrolysate might retard the development of hypertension in SHR by its inhibitory effect on ACE in vivo.

Genistein enhances expression of genes involved in fatty acid catabolism through activation of PPARalpha

Although evidences are emerging that dietary isoflavones have beneficial effects in treatment of hyperlipidemia and cardiovascular diseases, the underlying molecular mechanism has not yet been extensively characterized. In this report, we showed that genistein, one of the major isoflavones, increased expression of genes involved in lipid catabolism such as carnitine palmitoyltransferase 1, liver form (CPT1L) in HepG2 cells, when assayed by real-time reverse-transcriptase polymerase chain reactions as well as Western blotting analysis. The increase in mRNA-level of CPT1L after genistein treatment was not changed in the presence of ICI182780, a potent inhibitor of estrogen receptor, suggesting that this effect of genistein was estrogen receptor-independent. Since these genes involved in fatty acid catabolism are considered putative downstream target genes of peroxisome proliferators-activated receptor alpha (PPARalpha), we examined whether expression of PPARalpha was modulated by genistein treatment. Interestingly, genistein induced expression of PPARalpha at both mRNA- and protein-level. Further, genistein activated transcriptional activity of PPARalpha, when determined by reporter gene analysis, suggesting genistein as a potential ligand for PPARalpha. Taken together, this study provides a picture of the regulatory action of genistein, as an activator of PPARalpha in fatty acid catabolism and potential use of genistein as lipid-lowering agent.

Soy protein reduces triglyceride levels and triglyceride fatty acid fractional synthesis rate in hypercholesterolemic subjects

To examine the effects of protein source and isoflavones on triglyceride (TG) fatty acid (TGFA) and cholesterol biosynthesis, subjects (>50 years, LDL cholesterol >130 mg/dl) underwent a four-phase randomized cross-over feeding trial. Diets contained either isolated soy protein or common sources of animal protein (25 g/1000 kcal), without or with isoflavones (49 mg/1000 kcal) and were each fed for 6 weeks. Blood samples from 20 hyperlipidemic subjects (6M, 14F, 62 +/- 9 years, BMI 26 +/- 3 kg/m(2), LDL cholesterol >160 mg/dl after feeding animal protein without isoflavones) were selected to measure TGFA fractional synthetic rate (TGFA-FSR) and free cholesterol fractional synthetic rate (FC-FSR) over 24h as deuterium oxide uptake into TGFA and free cholesterol. Soy protein reduced TG by 12.4% (P < 0.0001), total cholesterol by 4.4% (P < 0.001), and LDL cholesterol by 5.7% (P = 0.003) compared to animal protein. The TGFA-FSR was reduced by 13.3% (P = 0.018) and FC-FSR was increased by 7.6% (P = 0.017) after the soy protein relative to the animal protein. Isoflavones had no significant effect on TG and TGFA-FSR. Isoflavones reduced total cholesterol levels by 3.1% (P = 0.009) but had no significant effect on LDL, HDL cholesterol levels, or FC-FSR. These data demonstrate that dietary protein type modulates circulating TG and cholesterol levels in hypercholesterolemic individuals by distinct mechanisms.

Phytoestrogens

Collectively, plants contain several different families of natural products among which are compounds with weak estrogenic or antiestrogenic activity toward mammals. These compounds, termed phytoestrogens, include certain isoflavonoids, flavonoids, stilbenes, and lignans. The best-studied dietary phytoestrogens are the soy isoflavones and the flaxseed lignans. Their perceived health beneficial properties extend beyond hormone-dependent breast and prostate cancers and osteoporosis to include cognitive function, cardiovascular disease, immunity and inflammation, and reproduction and fertility. In the future, metabolic engineering of plants could generate novel and exquisitely controlled dietary sources with which to better assess the potential health beneficial effects of phytoestrogens.

Soy protein with or without isoflavones, soy germ and soy germ extract, and daidzein lessen plasma cholesterol levels in golden Syrian hamsters

Dietary isolated soy protein (ISP, containing approximately equal amounts of daidzein and genistein), ethanol-extracted ISP (ISP (-)), soygerm or soygerm extract (containing large amounts of daidzein and glycitein and little genistein) and the isoflavone, daidzein, were hypothesized to lessen plasma cholesterol in comparison with casein. Sixty male and 60 female golden Syrian hamsters (6-8 weeks of age) were randomly assigned to six treatments fed for 10 weeks. Four of the experimental diets (ISP, daidzein, soygerm, and soygerm extract) contained 1.3 mmol total isoflavones/kg. The ISP (-) diet contained 0.013 mmol isoflavone/kg, whereas the casein diet contained no isoflavones. Hamsters fed ISP, ISP (-), daidzein, soygerm, and soygerm extract had significantly less plasma total cholesterol (by 16%-28%), less non-HDL cholesterol (by 15%-50%) and less non-HDL/HDL cholesterol ratios compared with hamsters fed casein (P < 0.01). For male hamsters, there were no differences among treatments in plasma HDL concentrations. Female hamsters fed ISP (-) had significantly greater HDL levels (P < 0.01) than females fed casein or daidzein. Triglyceride concentration was significantly less in hamsters fed ISP (-) compared with the casein-fed females. Because soy protein with or without isoflavones, soygerm and soygerm extract, and daidzein lessened plasma cholesterol to an approximately equal extent, soy protein alone, varying mixtures of isoflavones, and other extractable components of soy are responsible for cholesterol-lessening effects of soy foods, mainly due to their effects to lessen LDL cholesterol.

Effect of genistein and daidzein on platelet aggregation and monocyte and endothelial function

There has been much recent interest in the cardiovascular benefits of dietary isoflavones. The aim of the present in vitro studies was to investigate potential anti-thrombogenic and anti-atherogenic effects of the isoflavones genistein and daidzein in platelets, macrophages and endothelial cells. Pre-treatment with either isoflavone inhibited collagen-induced platelet aggregation in a dose-dependent manner. In a macrophage cell line (RAW 264.7) activated with interferon gamma plus lipopolysaccharide, both isoflavones were found to inhibit NO production and tumour necrosis factor alpha (TNF-alpha) secretion dose-dependently, but they did not affect mRNA levels for inducible nitric oxide synthase and cyclo-oxygenase-2. Both isoflavones also dose-dependently decreased monocyte chemoattractant protein-1 secretion induced by TNF-alpha in human umbilical vein endothelial cells. Compared with daidzein, genistein exerted greater inhibitory effects for all parameters studied. The present data contributes to our knowledge on the molecular mechanisms by which isoflavones may protect against coronary artery disease. Further studies are required to determine whether the effects of isoflavones observed in the current in vitro studies are relevant to the aetiology of coronary artery disease in vivo.

Soy isoflavones exert antidiabetic and hypolipidemic effects through the PPAR pathways in obese Zucker rats and murine RAW 264.7 cells

The hypocholesterolemic and anti-atherosclerotic mechanism by which soy may exert a beneficial effect remains unclear. Peroxisome-proliferator activated receptors (PPAR) are promiscuous nuclear receptors that regulate the transcription of genes involved in lipid and glucose homeostasis and lipid metabolism within the cell. We hypothesize that the isoflavones improve lipid and glucose metabolism by acting as an antidiabetic PPAR agonist. Male and female obese Zucker rats (OZR) were used as a model of Type 2 diabetes, and OZR fed a high isoflavone soy protein diet displayed improvements in lipid metabolism consistent with results in humans treated with antidiabetic PPAR agonists such as the fibrates or glitazones. Liver triglyceride and cholesterol concentrations were lower in all OZR fed high-isoflavone soy protein diets than in rats fed low-isoflavone and casein diets (P < 0.05). Concurrently, PPAR-directed gene expression was evaluated in a cell culture model. An isoflavone-containing soy extract doubled PPAR-directed gene expression (P < 0.05) in RAW 264.7 cells containing either a PPARalpha or PPARgamma expression plasmid. A similar induction was observed when the soy isoflavones genistein or daidzein were used to treat cells. Both isoflavones doubled PPARalpha-directed gene expression (P < 0.05), whereas they increased PPARgamma-directed gene expression 200-400% (P < 0.05). This study suggests that soy isoflavones improve lipid metabolism, produce an antidiabetic effect, and activate PPAR receptors.

Differentially abundant mRNAs in rat liver in response to diets containing soy protein isolate

Soy diets influence cell growth, regulate lipid metabolism to lower blood cholesterol, and prevent bone losses. These biological effects are most likely due to effects of soy phytochemicals on the expression of genes. In this study, we fed 12 female obese Zucker rats (fa/fa) with a low- or a high-isoflavone soy protein diet and compared the gene expression with animals on a casein diet. Rat livers were compared by differential display of mRNA, and 62 unique sequences were identified. The change in mRNA abundance of these sequences was quantified by cDNA macroarray analysis. Thirty-three mRNAs showed more than twofold increase in abundance on soy diets compared with the control. The corresponding genes include carnitine palmitoyltransferase I, stromal cell-derived factor 1, a protein associated with MYC mRNA, basic transcription element binding protein, and expressed sequence tags (ESTs) of unknown function. Twenty-nine mRNAs showed a less than twofold change in abundance in the two diet treatments. For majority of the genes identified, there was not significant difference between the low- and high-isoflavone diet treatments. Therefore, the contrast between soy protein and casein caused the changes observed in mRNA abundance.

Risks and benefits of soy phytoestrogens in cardiovascular diseases, cancer, climacteric symptoms and osteoporosis

Phytoestrogens, plant chemicals classified as isoflavones, coumestans and lignans, display estrogen-like activity because of their structural similarity to human estrogens and exhibit high affinity binding for the estrogen receptor beta. They are common components of food items such as grains, beans, fruits and nuts. Isoflavones are primarily found in soybeans and foods made from soy. In particular, significant therapeutic properties have been generally attributed to soy isoflavones, but most of the claims have been poorly, or not at all, confirmed by well designed clinical trials. Such is the case of the purported role of soy isoflavones in reducing plasma cholesterol levels. This link is now not supported by many authors or by appropriately designed clinical studies. The role of isoflavones in cancer prevention, particularly of tumours under endocrine control (breast, prostate and others) is again only supported by weak to nonexisting clinical evidence. A similarcase is that of the prevention/treatment of postmenopausal symptoms and osteoporosis. Disturbing data have been reported on potential negative effects of soy isoflavones on cognitive function in the aged, particularly relating to tofu intake. Recent studies have finally indicated a potential role for soy isoflavones in inducing chromosomal changes in cells exposed in vitro and potentiating chemical carcinogens. These findings may not, however, be extrapolated to clinical conditions. Available data do not appear to unequivocally support beneficial effects of soy isoflavones, and warn against their wide use, in the absence of satisfactory clinical findings.