cancer-prevention

Author: S. Bettuzzi and M. Brausi and F. Rizzi and G. Castagnetti and G. Peracchia and S. Astancolle and A. Corti

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Author: Brad A. Sutherland and Rosanna M.A. Rahman and Ian Appleton

Catechins are dietary polyphenolic compounds associated with a wide variety of beneficial health effects in vitro, in vivo and clinically. These therapeutic properties have long been attributed to the catechins' antioxidant and free radical scavenging effects. Emerging evidence has shown that catechins and their metabolites have many additional mechanisms of action by affecting numerous sites, potentiating endogenous antioxidants and eliciting dual actions during oxidative stress, ischemia and inflammation. Catechins have proven to modulate apoptosis at various points in the sequence, including altering expression of anti- and proapoptotic genes. Their anti-inflammatory effects are activated through a variety of different mechanisms, including modulation of nitric oxide synthase isoforms. Catechins' actions of attenuating oxidative stress and the inflammatory response may, in part, account for their confirmed neuroprotective capabilities following cerebral ischemia. The versatility of the mechanisms of action of catechins increases their therapeutic potential as interventions for numerous clinical disorders. However, more epidemiological and clinical studies need to be undertaken for their efficacy to be fully elucidated.

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Author: Dorothy M. Morré and D. James Morré

Grapes and grape extracts were compared for inhibition of a growth-related and cancer-specific form of cell surface NADH oxidase with protein disulfide-thiol interchange activity designated tNOX from human cervical carcinoma (HeLa) cells and growth of HeLa and mouse mammary 4T1 cells in culture and transplanted tumors in mice. Grapes and grape extracts of several varieties had activity. With an extracted grape preparation provided by the California Table Grape Commission, an active fraction was eluted with methanol from a Diaion HP-20 column after removal of inactive water-soluble materials. Grape skins were a much more potent source than either grape pulp, juice or seeds. Ethanol extracts of the ground freeze-dried pomace was an excellent source. The grape extracts interacted, often synergistically, with decaffeinated green tea extracts both in the inhibition of tNOX activity and in the inhibition of cancer cell growth. Intratumoral injections of a 25:1 mixture of a green tea extract plus ground freeze-dried pomace was nearly as effective as standard synergistic green tea–Capsicum mixtures in inhibiting growth of 4T1 mammary tumors in situ in mice.

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Author: N. Kavantzas and A. Chatziioannou and A.E. Yanni and D. Tsakayannis and D. Balafoutas and G. Agrogiannis and D. Perrea

Background and Aims Since the development of the atherosclerotic plaque requires the growth of new microvessels in the plaque itself (vasa vasorum), we postulated that green tea may exert an anti-atherogenic effect. Methods and results Thirteen male New Zealand white rabbits were studied for 17 weeks. All rabbits were fed an hypecholesterolemic diet. After 2 weeks of adaptation rabbits were randomly assigned into two groups. Animals in Group A were fed the hypercholesterolemic diet and received plain tap water ad libitum. Animals in Group B were fed with the same diet and furthermore received 2.5% (g/g) green tea for 17 weeks. Conclusion According to our results the atherosclerotic lesions were more severe in Group B than in Group A specimens. Also, the number of \{VEGF\} positively stained foam cells and smooth muscle cells of Group B were significantly greater than in Group A. About 30% less plaque was found in Group A than in the control group (Group B). So, our study showed that the consumption of green tea leads to a reduction of atherosclerosis as well as a significant decrease of VEGF expression in the atherosclerotic plaque of rabbit aorta. The hypothesis that probably green tea may produce its anti-atherogenetic effect through an anti-angiogenetic mechanism needs more investigation.

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Author: Pon Velayutham Anandh Babu and Kuruvimalai Ekambaram Sabitha and Chennam Srinivasulu Shyamaladevi

Diabetes-induced hyperlipidemia, oxidative stress and protein glycation impair cellular calcium and sodium homeostasis associated with abnormal membrane-bound enzyme activities resulting in cardiac dysfunction in diabetes. To explore the cardioprotective mechanism of green tea in diabetes, we measured the changes in the levels of calcium, sodium, potassium and the activities of Na+/K+-ATPase and Ca2+-ATPase in green tea treated diabetic rat hearts. The effect of green tea on triglycerides, lipid peroxidation and protein glycation in diabetic heart were also measured to elucidate the underlying mechanisms. Diabetes was induced by streptozotocin (STZ, 60 mg/kg i.p.). Six weeks after the induction of diabetes, some of the diabetic rats were treated orally with green tea extract (GTE) (300 mg/kg/day) for 4 weeks. GTE produced reduction in blood glucose and lowered the levels of lipid peroxides, triglycerides and extent of protein glycation in the heart of diabetic rats. GTE blunted the rise in cardiac [Ca2+] and [Na+] whereas increased the activities of Ca2+-ATPase and Na+/K+-ATPase in diabetic rats. In conclusion, the data provide support to the therapeutic effect of GTE and suggest that a possible mechanism of action may be associated with the attenuation of the rise in [Ca2+] and [Na+] by ameliorating Ca2+-ATPase and Na+/K+-ATPase activities.

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Author: Alissana Ester Iakmiu Camargo and Danielle Alessandra Erdei Daguer and Decio Sabbatini Barbosa

Antioxidant defenses can be characterized as agents (enzymes and low-molecular-mass antioxidants) in biological systems that prevent the noxious action of free radicals or other reactive species. The present study examined whether the use of green tea may exert antioxidant action in vitro and improve antioxidant defenses and serum lipids in normal and dyslipidemic subjects. Forty-one hypercholesterolemic individuals, 18 women and 23 men (age [mean ± SD], 44.81 ± 14.41), were evaluated before and after the daily intake of 6 g of green tea in 500 mL of water for 1 month. Likewise, 27 normolipidemic individuals, 12 women and 15 men (age, 37.07 ± 16.08), were also evaluated. Serum lipids were measured by an automated clinical chemistry system. The total serum antioxidant potential (TRAP) and serum levels of lipid hydroperoxides were quantified using the chemiluminescence method. Total polyphenols present in green tea ingested by the patients were verified by using Folin-Ciocalteau reagent. The in vitro evaluation of green tea antioxidant activity was performed using microsomes obtained from rat liver, which was oxidized by tert-butyl hydroperoxide. From this system, thiobarbituric acid reactive substances were measured. In the in vitro test, green tea polyphenols proved to be efficient at protecting microsomes from the oxidant activity of tert-butyl hydroperoxide. There were no significant alterations in the lipid profiles of the normolipidemic or hypercholesterolemic subject groups. Although there was no decrease in lipid hydroperoxides, both groups showed increased antioxidant defenses, which was evidenced by TRAP. In conclusion, the results obtained indicate that besides achieving antioxidant action in vitro, the consumption of green tea increased the TRAP of normal and dyslipidemic subjects.

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Author: Hüseyin Bozkurt

Effect of natural (green tea extract, Thymbra spicata oil) and synthetic antioxidants (buthylatedhydroxytoluene, BHT) on the safety (biogenic amine and TBARS values) and quality (pH, colour and sensory attributes) of sucuk (Turkish dry-fermented sausage) were investigated during the ripening periods. Addition of antioxidants decreased (P < 0.05) the TBARS values. It was found that natural antioxidants decreased TBARS formation more than BHT. Antioxidants reduced (P < 0.05) putrescine formation in the following order: green tea extract > green tea extract–T. spicata oil > T. spicata oil > BHT, and their mean values were 70.45, 76.05, 83.13, and 95.97 mg/kg, respectively. The highest tyramine concentration was observed in control sucuk prepared without any antioxidants, while the lowest was in the recipe with green tea extract as their mean values were about 99.42 and 64.31 mg/kg, respectively. The pH, L, b, and overall sensory quality were not significantly different (P > 0.05) with the addition of green tea extract, T. spicata oil, green tea extract–T. spicata oil. These results indicated that the most effective antioxidant was found to be green tea extract. This study pointed out that natural antioxidants were more effective than synthetic antioxidants, so they could be easily utilized in sucuk to enhance quality and provide safer products.

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Author: Maria Kapsokefalou and Le Zhu and Dennis D. Miller

Author: Pon Velayutham Anandh Babu and Kuruvimalai Ekambaram Sabitha and Chennam Srinivasulu Shyamaladevi

Hyperglycemia induced oxidative stress has been proposed as a cause of many complications of diabetes including cardiac dysfunction. The present study depicts the therapeutic effect of green tea extract on oxidative stress in aorta as well as heart of streptozotocin diabetic rats. Six weeks after diabetes induction, green tea was administered orally for 4 weeks [300 mg (kg body weight)−1 day−1]. In aorta and heart of diabetic rats there was a significant increase in the activity of superoxide dismutase, catalase and glutathione peroxidase with an increase in lipid peroxides. Diabetic rats showed a significant decrease in the levels of serum and cardiac glutathione. Green tea administration to diabetic rats reduced lipid peroxides and activity of antioxidant enzymes whereas increased glutathione content. The results demonstrate that the induction of antioxidant enzymes in diabetic rats is not efficient and sufficient to reduce the oxidative stress. But green tea by providing a competent antioxidative mechanism ameliorates the oxidative stress in the aorta and heart of diabetic rats. The study suggests that green tea may provide a useful therapeutic option in the reversal of oxidative stress induced cardiac dysfunction in diabetes mellitus.

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Author: Alessandra Gamberucci and Laura Konta and Angela Colucci and Roberta Giunti and Judit É. Magyar and József Mandl and Gábor Bánhegyi and Angelo Benedetti and Miklós Csala

Green tea is getting into the focus of scientific interest due to its beneficial health effects, most of which are attributed to its catechin content. Polyphenolic tea catechins have antioxidant, antiproliferative, antiangiogenic and proapoptotic effects, which makes them promising anticancer compounds. Other poly-hydroxy molecules have similar antitumor potentials through the inhibition of glucosidase II, which affects the glycoprotein maturation and quality control in the endoplasmic reticulum. We investigated the effect of tea catechins on glucosidase II activity in rat liver microsomes using 4-methylumbelliferyl glucoside and 4-nitrophenyl glucoside as substrates. A concentration-dependent inhibition with non-competitive kinetics was found. The IC50 and Ki values for certain tea catechins were comparable with those of N-butyldeoxynojirimycin, the widely used glucosidase inhibitor. The possible interference of tea catechins with the glycoprotein processing in the endoplasmic reticulum should be considered as a potential mechanism of their dietary or pharmacological effects.

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