Protective Effect of Glyceollins in a Mouse Model of Dextran Sulfate Sodium-Induced Colitis.

Glyceollins, which are derived from daidzein in soybean in response to various stimuli or stresses, have been reported to activate antioxidant/detoxifying enzymes in a nuclear factor (erythroid-derived 2)-like 2 (Nrf2)-dependent manner, in addition to exerting anti-inflammatory effects in murine macrophages. As the Nrf2 signaling pathway is known to antagonize nuclear factor (NF)-κB signaling, glyceollins likely have the potential to prevent or treat inflammatory bowel disease. Thus, this study was conducted to examine whether glyceollins could inhibit dextran sulfate sodium (DSS)-induced colitis in a mouse model. Ulcerative colitis (UC) was induced in male BALB/c mice by administering drinking water with 4% DSS for 5 days. Glyceollins (4 or 10 mg/kg of body weight) were orally administered 48 h before and after DSS treatment. We found that glyceollins alleviated histological colon damage and inflammation induced by DSS treatment. More specifically, glyceollins reduced plasma levels of inflammatory cytokines, such as tumor necrosis factor-α and interleukin-6, which were otherwise markedly increased by DSS treatment. Markers of tissue damage, including malondialdehyde and 8-hydroxy-2-guanosine, were significantly increased by DSS treatment; however, this effect was mitigated through concomitant treatment with glyceollins. Furthermore, nuclear accumulation of NF-κB p65 and the expression of inducible nitric oxide synthase were upregulated by glyceollins, consistent with the observed modulation of inflammatory markers. In conclusion, glyceollins have therapeutic potential for UC and merit further clinical study.

Antioxidant and Anti-inflammatory Effects of Yam (Dioscorea batatas Decne.) on Azoxymethane-induced Colonic Aberrant Crypt Foci in F344 Rats.

Yam (Dioscorea batatas Decne.) has long been used as a health food and oriental folk medicine because of its nutritional fortification, tonic, anti-diarrheal, anti-inflammatory, antitussive, and expectorant effects. Reactive oxygen species (ROS), which are known to be implicated in a range of diseases, may be important progenitors of carcinogenesis. The aim of this study was to investigate the modulatory effect of yam on antioxidant status and inflammatory conditions during azoxymethane (AOM)-induced colon carcinogenesis in male F344 rats. We measured the formation of aberrant crypt foci (ACF), hemolysate antioxidant enzyme activities, colonic mucosal antioxidant enzyme gene expression, and colonic mucosal inflammatory mediator gene expression. The feeding of yam prior to carcinogenesis significantly inhibited AOM-induced colonic ACF formation. In yam-administered rats, erythrocyte levels of glutathione, glutathione peroxidase (GPx), and catalase were increased and colonic mucosal gene expression of Cu/Zn-superoxide dismutase (SOD), Mn-SOD, and GPx were up-regulated compared to the AOM group. Colonic mucosal gene expression of inflammatory mediators (i.e., nuclear factor kappaB, inducible nitric oxide synthase, cyclooxygenase-2, tumor necrosis factor alpha, and interleukin-1beta) was suppressed by the yam-supplemented diet. These results suggest that yam could be very useful for the prevention of colon cancer, as they enhance the antioxidant defense system and modulate inflammatory mediators.

Fungicidal effect of prenylated flavonol, papyriflavonol A, isolated from Broussonetia papyrifera (L.) vent. against Candida albicans.

Papyriflavonol A (PapA), a prenylated flavonoid (5,7,3',4'-tetrahydroxy-6,5'-di-(r,r-dimethylallyl)-flavonol), was isolated from the root barks of Broussonetia papyriferra. Our previous study showed that PapA has a broad-spectrum antimicrobial activity against pathogenic bacteria and fungi. In this study, the mode of action of PapA against Candida albicans was investigated to evaluate PapA as antifungal agent. The minimal inhibitory concentration (MIC) values were 10~25 microgram/ml for C. albicans and Saccharomyces cerevisiae, gram-negative bacteria (Escherichia coli and Salmonella typhimurium) and gram-positive bacteria (Staphylococcus epidermidis and Staphylococcus aureus). The kinetics of cell growth inhibition, scanning electron microscopy, and measurement of plasma membrane florescence anisotrophy revealed that the antifungal activity of PapA against C. albicans and S. cerevisiae is mediated by its ability to disrupt the cell membrane integrity. Compared with amphotericin B, a cell membrane disrupting polyene antibiotic, the hemolytic toxicity of PapA was negligible. At 10~25 microgram/ml of MIC levels for the tested strains, the hemolysis ratio of human erythrocytes was less than 5%. Our results suggest that PapA could be a therapeutic fungicidal agent having a broad spectrum antimicrobial agent.

Antioxidative and hypolipidemic effects of diosgenin, a steroidal saponin of yam (Dioscorea spp.), on high-cholesterol fed rats.

Diosgenin (a steroidal saponin of yam) has long been used as a raw material for the industrial production of steroid drugs, and reported to have a hypocholesterolemic effect by suppressing cholesterol absorption and increasing cholesterol secretion. Oxidative stress has been suggested as a main risk factor in the development of atherosclerosis. The aim of this study is to investigate the possible hypolipidemic and antioxidative effect of diosgenin on rats fed with a high-cholesterol diet supplemented with either 0.1% or 0.5% diosgenin for 6 weeks. We measured the lipid profile in the plasma and liver, lipid peroxidation and antioxidative enzyme activities in the plasma, erythrocyte and gene expression of antioxidative enzymes in the liver, and the oxidative DNA damage in lymphocytes. Diosgenin showed a decrease in the plasma and hepatic total cholesterol levels, but increased the plasma high-density lipoprotein (HDL) cholesterol level. Erythrocyte TBARS and lymphocyte DNA damage measured by the comet assay were decreased in the diosgenin supplemented group. Furthermore, diosgenin feeding enhanced the resistance to lymphocyte DNA damage caused by an oxidant challenge with H(2)O(2). The antioxidative enzyme activities were also affected by diosgenin supplementation. Total superoxide dismutase (SOD) in the plasma and liver, glutathione peroxidase (GSH-Px) in erythrocytes, and catalase (CAT) in erythrocytes and liver were significantly increased in the 0.5% diosgenin group. The expression of antioxidative enzymes was up-regulated by diosgenin, the expression of GSH-Px being the highest in the 0.5% diosgenin group. These results suggest that diosgenin could be a very useful compound to control hypercholesterolemia by both improving the lipid profile and modulating oxidative stress.

Mononuclear cell metallothionein mRNA levels in human subjects with poor zinc nutrition.

Human zinc deficiency is thought to be prevalent worldwide, particularly in populations with diets low in zinc and animal protein and high in inhibitors of zinc absorption, such as phytic acid. Confirmation of zinc deficiency is, however, difficult in the absence of a reliable and sensitive marker of zinc status. Under controlled conditions, T-lymphocyte metallothionein-2A (MT-2A) mRNA levels change in relation to zinc status and the objective of the present study was to investigate whether these transcript levels could be related to dietary zinc intake, plasma zinc or other biochemical parameters influenced by, or influencing, zinc metabolism in human subjects likely to be zinc deficient. Rural Koreans (n 110, age 50-80 years) with a range of zinc and phytic acid dietary intake were recruited for the study and blood samples were analysed for plasma zinc, HDL, LDL, alpha-tocopherol and thiobarbituric acid reactive substances, mononuclear cell (MNC) MT-2A mRNA, serum protein and albumin, and blood haematocrit, Hb and glucose. Multiple correlation and principal component analysis showed a significant negative correlation between plasma zinc and MNC MT-2A mRNA levels. Female subjects had higher MT-2A transcript levels than males and MT-2A mRNA levels tended to increase with age. There was no significant association between dietary zinc intake or any index of zinc intake relating to dietary inhibitors of zinc absorption. It is concluded that MNC MT-2A mRNA levels cannot be used to predict poor zinc nutrition.

Hepatic responses to dietary stress in zinc- and metallothionein-deficient mice.

Metallothionein (MT) and zinc are both reported to be protective against oxidative and inflammatory stress and may also influence energy metabolism. The role of MT in regulating intracellular labile zinc, thus influencing zinc (Zn)-modulated protein activity, may be a key factor in the response to stress and other metabolic challenges. The objective of this study was to investigate the influence of dietary zinc intake and MT on hepatic responses to a pro-oxidant stress and energy challenge in the form of a high dietary intake of linoleic acid, an omega-6 polyunsaturated fatty acid. Male MT-null (KO) and wild-type (WT) mice, aged 16 weeks, were given semisynthetic diets containing 16% fat and either 5 (marginally zinc-deficient [ZD]) or 35 (zinc-adequate [ZA]) mg Zn/kg. For comparison, separate groups of KO and WT mice were given a rodent chow diet containing 3.36% fat and 86.6 mg Zn/kg. After 4 months on these diets, the body weights of all mice were equal, but liver size, weight, and lipid content were much greater in the animals that consumed semisynthetic diets compared to the chow diet. The increase in liver size was significantly lower in ZA but not ZD KO mice, compared with WT mice. Principally, MT appears to affect the diet-induced increase in liver tissue but it also influences the concentration of hepatic lipid. Plasma levels of C-reactive protein (CRP), a marker of inflammation, were increased by zinc deficiency in WT mice, suggesting that marginal zinc deficiency is proinflammatory. CRP was unaffected by zinc deficiency in KO mice, indicating a role for MT in modulating the influence of zinc. Neither zinc nor MT deficiency affects the level of soluble liver proteins, as determined using two-dimensional (2D) gel proteomics. This study highlights the close association between zinc and MT in the manifestation of stress responses.

Lower antioxidant vitamins (A, C and E) and trace minerals (Zn, Cu, Mn, Fe And Se) status in patients with cerebrovascular disease.

The management of antioxidant micronutrient status in patients with chronic diseases may be an important step in controlling disease progression and preventing deterioration in patient quality of life. The objective of this study was to investigate the antioxidant micronutrient status and lipid profiles of cerebrovascular disease (CbVD) patients and to compare this information with an evaluation of normal healthy subjects. A total of 57 male subjects (26 patients with CbVD and 31 healthy subjects) and 65 female subjects (32 patients with CbVD and 33 healthy subjects) were included in this cross-sectional study. Plasma lipid profiles, thiobarbituric acid-reactive substances (TBARS), fasting plasma concentration of antioxidant vitamins (A, C, E) and trace minerals (Cu, Zn, Mn, Fe and Se) were measured. Compared to healthy subjects, male but not female CbVD patients showed a lower energy intake (p < 0.01) which was largely due to a lower intake of dietary carbohydrate. They also consumed a diet containing a higher level of vitamins A and C. Plasma vitamin C (p < 0.01, in women) and vitamin E (p < 0.05, both in men and women) concentrations were prominently lower in the patients compared to healthy subjects. Plasma levels of the two antioxidant minerals Zn and Se were found to be markedly lower in the patients with CbVD, both in men and women (p < 0.05). Despite consuming less energy and food with a higher vitamin A and C level than healthy subjects, antioxidant micronutrient status, lipid peroxidation levels and the atherogenic index of male CbVD patients suggested that their antioxidant micronutrient intake was in some respects nutritionally inadequate. A similar conclusion could be made regarding the nutritional inadequacy of female CbVD patient diets. Expert dietary advice and intervention should be given to CbVD patients in order to optimize micronutrient intake and status.

Induction of oxidative stress by endosulfan and protective effect of lipid-soluble antioxidants against endosulfan-induced oxidative damage.

The toxic mechanism of endosulfan, a widely used organochlorine pesticide, was investigated in Saccharomyces cerevisiae and human cell lines. A concentration-dependent inhibition of cell growth was observed when S. cerevisiae was exposed to endosulfan, and its cytotoxicity (IC(50)) was found to be 49 microM and 86 microM in HepG2 and HeLa human cell lines, respectively. The treatment of S. cerevisiae with endosulfan resulted in oxidative damage, as demonstrated by thiobarbituric acid-reactive substance (TBARS) production, in a dose-dependent manner, and the growth inhibition was recovered by treatment with lipid-soluble antioxidants, such as alpha-tocopherol or beta-carotene, suggesting that endosulfan toxicity may be closely associated with endosulfan-induced reactive oxygen species (ROS) generation. The inhibition of cellular respiration by endosulfan treatment and the recovery of respiration activity by antioxidant treatment confirmed that endosulfan induces oxidative stress and inhibits respiration via ROS generation. These results suggest that unicellular yeast might provide a useful system for elucidating the toxicity of endosulfan.

Polyozellin isolated from Polyozellus multiplex induces phase 2 enzymes in mouse hepatoma cells and differentiation in human myeloid leukaemic cell lines.

Induction of cellular phase 2 detoxifying enzymes is associated with cancer preventive potential. Quinone reductase (QR) has been used as a prototype for anticarcinogenic phase 2 enzymes because of its widespread distribution in mammalian systems, large amplitude of inducer response, and ease of measurement in murine hepatoma cells. Methanol extract of Polyozellus multiplex, which shows a strong QR induction potential, was subjected to bioassay-guided fractionation, and polyozellin (PM1) appeared to be a major active component. In in vitro cultured cells (hepa1c1c7 and BPRc1 cells), polyozellin enhanced QR, glutathione S-transferase (GST) activities, and glutathione (GSH) content in a dose-dependent manner. The compound also significantly promoted differentiation of HL-60 human promyelocytic emia cells. In conclusion, polyozellin deserves further in vivo study to evaluate its potential as a cancer preventive agent.

Anti-obesity effect of Dioscorea nipponica Makino with lipase-inhibitory activity in rodents.

In the process of screening for pancreatic lipase inhibitors, which could be used as an anti-obesity measure, the methanol extract of Dioscorea nipponica Makino powder (DP) appeared to have potent inhibitory activity against porcine pancreatic lipase with an IC50 value of 5-10 microg/ml, where the enzyme activity was assayed by using 4-methylumbelliferyl oleate as a substrate. Further purification of active components present in the herb generated dioscin that belongs to the saponin family. Dioscin and its aglycone, diosgenin, both suppressed the time-dependent increase of blood triacylglycerol level when orally injected with corn oil to mice, suggesting their inhibitory potential against fat absorption. Sprague-Dawley rats fed on a high-fat diet containing 5% Dioscorea nipponica Makino and 40% beef tallow gained significantly less body weight and adipose tissue than control animals fed on a high-fat diet alone during an 8-week experimental period (P<0.05).

Regulation of male sex hormone levels by soy isoflavones in rats.

Several studies have suggested that soybean intake is associated with a lower risk of prostate cancer. However, the mechanism of prostate cancer prevention by soybeans remains unclear. Because prostate cancer is reported to have an association with an increased level of dihydrotestosterone (DHT) and soybean isoflavones are known to inhibit 5 alpha-reductase, which is involved in the conversion of testosterone to DHT, the effects of soybean extract and isoflavones on the plasma levels of male sex hormones were investigated using male rats. In Experiment I, Sprague-Dawley rats were fed diets with and without soy flour; in Experiment II, rats were fed diets containing 2% soy methanol extract or 0.2% semipurified isoflavones or a control diet. The study showed a reduction of plasma DHT along with an increase in total plasma androgen in rats fed soy flour or semipurified isoflavones for 1 wk. These results suggest that soy isoflavone intake may reduce plasma DHT level.