Isoflavone supplementation reduces DNA oxidative damage and increases O-β-N-acetyl-d-glucosaminidase activity in healthy women

Phenolic compounds are believed to boost the human antioxidant defense system and health; therefore, the aim of this research was to investigate the hypothesis that soy isoflavones (IFs) provide antioxidant protection in healthy women by evaluating DNA resistance to oxidative damage and O-β-N-acetyl-d-glucosaminidase (OGA) activity. An IF supplement (80 mg/d) was given to 9 postmenopausal women and 13 young women for 6 months and then stopped up to the 14th month. The women were allowed to consume their normal diet. Blood samples were collected at the beginning of the study after 2, 4, and 6 months and then at the 8th and 14th months. Plasma concentrations of genistein and daidzein, total antioxidant capacity, plasma vitamin status, markers of oxidative stress (red blood cell membrane fluidity, activity of the red blood cell cytosolic enzyme OGA and lymphocyte DNA susceptibility to oxidative stress), and serum lipid profile were analyzed. Analysis of variance for repeated measures was used for statistical analysis. Plasma concentrations of IFs rose significantly during the supplementation period, and plasma total antioxidant capacity increased in young women; membrane fluidity and OGA activity increased, and DNA oxidative damage decreased (P < .05) at 4 months, then returned to the basal level. There was a significant inverse correlation between DNA damage and plasma IF concentrations (P < .01). The results indicated a positive effect of IF supplementation on oxidative stress in women, thus suggesting that the healthful action ascribed to soy consumption may be partially related to the antioxidant potential of IFs.     

染料木黄酮对脂多糖诱导的RAW264.7细胞炎症因子、腺苷酸激活蛋白激酶磷酸化的影响

目的研究染料木黄酮(genistein,Gen)对脂多糖(LPS)诱导的巨噬细胞炎症因子产生和腺苷酸激活蛋白激酶(AMPK)磷酸化的影响。方法体外培养RAW 264.7小鼠单核巨噬细胞,加入1、5、10、50、100 mol/L的Gen共同培养,MTT法检测其对细胞活性的影响。将RAW264.7细胞随机分为4组:空白对照组不加任何药物,模型组加入终浓度为1 g/ml的LPS进行刺激,Gen高、低剂量组分别加入终浓度为10、5 mol/L的Gen预处理1h后,再加入终浓度为1 g/ml的LPS刺激,24h后收取细胞上清用酶联免疫(ELISA)方法检测TNF-α、IL-6含量,Westernblot检测AMPKα蛋白及其磷酸化的表达水平。结果 100 mol/L的Gen对体外培养RAW264.7细胞的增殖有影响,而其他浓度则无。LPS处理的RAW 264.7细胞与对照组比较,TNF-α、IL-6生成显著增多(P<0.01)、AMPKα磷酸化水平显著降低(P<0.01),而AMPKα总蛋白表达水平无差异(P>0.05)。Gen干预可减少LPS诱导的TNF-α、IL-6生成,上调AMPKα磷酸化水平的表达,与LPS组相比,差异均有统计学意义(P<0.01)。结论 Gen能抑制LPS诱导巨噬细胞的炎症反应,减少TNF-α、IL-6生成,这可能与Gen促进AMPKα磷酸化,从而激活AMPKα有关。     

Flavonoids inhibit platelet function through binding to the thromboxane A2 receptor.

BACKGROUND: Dietary flavonoids are known for their antiplatelet activity resulting in cardiovascular protection, although the specific mechanisms by which this inhibition occurs has not been fully established. OBJECTIVE: The aim of this study was to investigate the interaction of nine flavonoids representative of various chemical classes, with platelet responses dependent on thromboxane A(2) (TxA(2)) generation and on receptor antagonism, and to analyze the structural requirements for such effects. METHODS: The effect of several types of flavonoids on platelet aggregation, serotonin release, and TxA(2) generation was investigated. Competitive radioligand binding assays were used to screen for affinity of these compounds to TxA(2) receptors. RESULTS: Flavones (apigenin and luteolin) and isoflavones (genistein) abrogated arachidonic acid and collagen-induced platelet responses, such as aggregation and secretion, with a less substantial effect on TxA(2) synthesis. These compounds were identified as specific ligands of the TxA(2) receptor in the micromol L(-1) range, this effect accounting for antiplatelet effects related to stimulation with those agonists. Tight binding of flavonoids to the human TxA(2) receptor relies on structural features such as the presence of the double bond in C2-C3, and a keto group in C4. CONCLUSIONS: The inhibition by specific flavonoids of in vitro platelet responses induced by collagen or arachidonic acid seems to be related, to a great extent, to their ability to compete for binding to the TxA(2) receptor. Therefore, antagonism of this TxA(2) receptor may represent an additional mechanism for the inhibitory effect of these compounds in platelet function.     

Regulation of transient outward current in human atrial myocytes by protein tyrosine kinase pathway

INTRODUCTION: Regulation of transient outward current (I(to)) in human myocytes is unclear. The present study investigated the effect of protein tyrosine kinase (PTK) inhibitors on I(to) in human atrial myocytes. METHODS AND RESULTS: Atrial myocytes were isolated enzymatically from biopsies of human right atrial appendage obtained from patients undergoing coronary artery bypass surgery. I(to) was recorded by the whole-cell patch-clamp technique in voltage-clamp configuration. Two groups of PTK inhibitors, the ATP binding site PTK inhibitors genistein and AG957 and the protein substrate PTK inhibitors ST638 and PP2, significantly inhibited I(to) in a concentration-dependent manner, with a potency order of genistein>AG957>ST638>PP2. At test pulse potential of +60 mV, I(to) was inhibited by 28% +/- 3%, 59% +/- 3%, and 89% +/- 3% by 15, 50, and 100 microM genistein, respectively. Daidzein and PP3, inactive analogues of genistein and PP2, respectively, did not produce any inhibitory effects on I(to). In addition to the inhibition of I(to) amplitude, the protein substrate PTK inhibitors ST638 and PP2 significantly accelerated I(to) inactivation (current decay) and delayed recovery from inactivation. Inhibition of protein tyrosine phosphatase partially reversed the effect of genistein. Stimulation or inhibition of serine/ threonine kinases (PKA, PKC, and PKG) did not change I(to) or alter the inhibitory response of PTK inhibitors on I(to). CONCLUSION: In human atrial cells, the PTK pathway plays an important role in the regulation of basal I(to), independent of serine/threonine kinases.     

Genistein Treatment Confers Protection against Gliopathy and Vasculopathy of the Diabetic Retina in Rats

Retinopathy remains an important complication of diabetes. This work was carried out to evaluate the protective effects of genistein from diabetic retinopathy in rat. Fifteen adult male albino rats were divided into two groups; Group I: control (n?=?5) and Group II: streptozotocin induced diabetic group (n?=?10), which is equally divided into two subgroups; IIa (diabetic vehicle control) and IIb (diabetic genistein-treated). Specimens were taken from the retina 12 weeks post induction, processed and examined using light, immunohistochemical, ultrastructural techniques. Blood samples were assayed for the levels of glucose. In comparison with the diabetic non-treated group, the histological changes in macro and microglial glial cells reactivity and retinal blood capillaries were improved in genistein-treated groups. In addition, GFAP and iNOS expressions in the retina and the blood glucose level were reduced. Genistein ameliorates the histological changes of diabetic retinopathy reaching healing features, which resemble that of a normal retina.     

Enhanced Expression of Sodium Hydrogen Exchanger (NHE)-1, 2 and 4 in the Cervix of Ovariectomised Rats by Phytoestrogen Genistein

Restoring the pH of cervicovaginal fluid is important for the cervicovaginal health after menopause. Genistein, which is a widely consumed dietary health supplement to overcome the post-menopausal complications could help to restore the cervicovaginal fluid pH. We hypothesized that genistien effect involves changes in expression of NHE-1, 2 and 4 proteins and mRNAs in the cervix. This study investigated effect of genistein on NHE-1, 2 and 4 protein and mRNA expression in the cervix in order to elucidate the mechanisms underlying possible effect of this compound on cervicovaginal fluid pH after menopause. Methods: Ovariectomised adult female rats received 25, 50 and 100 mg/kg/day genistein for seven consecutive days. At the end of the treatment, animals were sacrificed and cervix was harvested. Expression of Nhe-1, 2 and 4 mRNA were analyzed by Real-time PCR while distribution of NHE-1, 2 and 4 protein were observed by immunohistochemistry. Results: Treatment with 50 and 100 mg/kg/day genistein caused marked increase in the levels of expression and distribution of NHE-1, 2 and 4 proteins in the endocervical epithelia. Levels of Nhe-1, 2 and 4 mRNA in the cervix were also increased. Coadministration of ICI 182 780 and genistein reduced the expression levels of NHE-1, 2 and 4 proteins and mRNAs in the cervix. Conclusions: Enhanced expression of NHE-1, 2 and 4 proteins and mRNAs expression in cervix under genistein influence could help to restore the cervicovaginal fluid pH that might help to prevent cervicovaginal complications related to menopause.     

Genistein attenuates glucocorticoid-induced bone deleterious effects through regulation Eph/ephrin expression in aged mice

Objective: This study was performed to investigate bone deteriorations and the involvement of skeletal Eph/ephrin signaling pathway of GIOP aged mice in response to the treatment of genistein. Methods: The biomarkers in serum and urine were measured, tibias were taken for the measurement on gene and protein expression and histomorphology analysis, and femurs were taken for the measurement on bone Ca and three-dimensional architecture of trabecular bone. Results: Genistein showed a greater increase in bone Ca, BMD and significantly increased FGF-23 and OCN, reduced TRACP-5b, PTH and CTX in GIOP mice. Genistein reversed DXM-induced trabecular deleterious effects and stimulated bone remodeling. The treatment of DXM group with genistein significantly elevated the ratio of OPG/RANKL. Moreover, genistein administration down-regulated the mRNA and protein expression of Eph A2 and ephrin A2 in tibia of the GIOP mice. In contrast, the mRNA and protein expression of Eph B4 and ephrin B2 were increased in mice treated by DXM with genistein as compared to the DXM single treatment. Conclusions: DXM-induced trabecular bone micro-structure deterioration in aged mice was involved in the regulation of the Eph receptors and ephrin ligands. Genistein might represent a therapy with bone-forming as well as an anti-resorptive activity in GIOP mice. The underlying mechanism was mediated, at least partially, through regulation Eph/ephrin signaling.     

Effect of Genistein,a Soy Isof lavone,on Whole Body Insulin Sensitivity and Renal Damage Induced by a High-Fructose Diet

The study evaluates the effect of genistein, a soy isoflavone, on insulin sensitivity and renal functional and structural injury in rats rendered insulin-resistant by feeding on a high-fructose diet for 60 days. Fructose-fed animals (60 g /100 g) displayed insulin resistance as indicated by the measures of insulin sensitivity [insulin sensitivity index (ISI_0,120), quantitative insulin check index (QUICKI), and homeostatic model assessment (HOMA)]. Alterations in body weight, kidney weight, urine volume, plasma, and urine electrolytes accompanied by significant increases in plasma and urinary levels of urea, uric acid, creatinine, total protein, and albumin were observed in fructose-fed rats. Oxidative stress in kidney was noted by an elevation in lipid peroxides and a decline in glutathione (GSH). Insulin sensitivity and renal function were improved in fructose-fed rats administered genistein. Histological changes such as fatty infiltration and thickening of glomeruli observed in fructose-fed rats were also ameliorated when genistein was co-administered. The study shows that genistein improves insulin sensitivity and kidney function in a dietary model of insulin resistance. We suggest that genistein may have benefits for patients suffering from kidney disease associated with insulin resistance.