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      Garlic supplementation prevents oxidative DNA damage in essential hypertension

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      Molecular and Cellular Biochemistry

      Springer Science and Business Media LLC

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          Abstract

          Oxygen-free radicals and other oxygen/nitrogen species are constantly generated in the human body. Most are intercepted by antioxidant defences and perform useful metabolic roles, whereas others escape to damage biomolecules like DNA, lipids and proteins. Garlic has been shown to contain antioxidant phytochemicals that prevent oxidative damage. These include unique water-soluble organosulphur compounds, lipid-soluble organosulphur compounds and flavonoids. Therefore, in the present study, we have tried to explore the antioxidant effect of garlic supplementation on oxidative stress-induced DNA damage, nitric oxide (NO) and superoxide generation and on the total antioxidant status (TAS) in patients of essential hypertension (EH). Twenty patients of EH as diagnosed by JNC VI criteria (Group I) and 20 age and sex-matched normotensive controls (Group II) were enrolled in the study. Both groups were given garlic pearls (GP) in a dose of 250 mg per day for 2 months. Baseline samples were taken at the start of the study, i.e. 0 day, and thereafter 2 months follow-up. 8-Hydroxy-2'-deoxyguanosine (8-OHdG), lipids, lipid peroxidation (MDA), NO and antioxidant vitamins A, E and C were determined. A moderate decline in blood pressure (BP) and a significant reduction in 8-OHdG, NO levels and lipid peroxidation were observed in Group I subjects with GP supplementation. Further, a significant increase in vitamin levels and TAS was also observed in this group as compared to the control subjects. These findings point out the beneficial effects of garlic supplementation in reducing blood pressure and counteracting oxidative stress, and thereby, offering cardioprotection in essential hypertensives.

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          Most cited references 42

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          Superoxide anion is involved in the breakdown of endothelium-derived vascular relaxing factor.

          Endothelium-derived vascular relaxing factor (EDRF) is a humoral agent that is released by vascular endothelium and mediates vasodilator responses induced by various substances including acetylcholine and bradykinin. EDRF is very unstable, with a half-life of between 6 and 50 s, and is clearly distinguishable from prostacyclin. The chemical structure of EDRF is unknown but it has been suggested that it is either a hydroperoxy- or free radical-derivative of arachidonic acid or an unstable aldehyde, ketone or lactone. We have examined the role of superoxide anion (O-2) in the inactivation of EDRF released from vascular endothelial cells cultured on microcarrier beads and bioassayed using a cascade of superfused aortic smooth muscle strips. With this system, we have now demonstrated that EDRF is protected from breakdown by superoxide dismutase (SOD) and Cu2+, but not by catalase, and is inactivated by Fe2+. These findings indicate that O-2 contributes significantly to the instability of EDRF.
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            Repair of oxidative damage to DNA: enzymology and biology.

             C Harrison,  B Demple (1993)
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              Oxidative DNA damage estimated by 8-hydroxydeoxyguanosine excretion in humans: influence of smoking, gender and body mass index.

               S Loft,  M Ewertz,  K. Overvad (1992)
              Oxidative DNA damage may be implicated in ageing, carcinogenesis and other degenerative diseases. Oxidative DNA damage can be assessed in humans in vivo from the urinary excretion of the DNA-repair product 8-hydroxydeoxyguanosine (8OHdG). We investigated factors influencing the excretion of 8OHdG in 24 h urine from 83 randomly selected healthy subjects (52 women) aged 40-64 years. For 2 weeks prior to urine collection the subjects kept a weighed diet record. 8OHdG was quantified by an automatic three-dimensional HPLC analysis with electrochemical detection. The 8OHdG excretion was 252 +/- 103 (mean +/- SD) pmol kg body weight/24 h with a range from 78 to 527. Multiple regression analysis identified three factors, smoking, body mass index (BMI) and gender, as significant predictors of the 8OHdG excretion. In 30 smokers the 8OHdG excretion was 320 +/- 99 pmol/kg/24 h opposed to 213 +/- 84 pmol/kg/24 h in 53 non-smokers. According to multiple regression analysis smokers excreted 50% (31-69%; 95% confidence interval) more 8OHdG than non-smokers. In 52 women the 8OHdG excretion was 240 +/- 106 pmol/kg/24 h opposed to 271 +/- 96 pmol/kg/24 h in 31 men. According to the multiple regression analysis men excreted 29% (10-48%) more 8OHdG than women. According to multiple regression analysis the 8OHdG excretion decreased with 4% (2-6%) per increment in BMI measured in kg/m2. The dietary distribution of energy demonstrated no important predictive value with respect to 8OHdG excretion. The intake of the antioxidant vitamins C and E and of vitamin A equivalents, including beta-carotene, was not associated with 8OHdG excretion. The results suggest that smoking increases oxidative DNA damage by approximately 50%. This effect implies potential serious health effects adding to the other well-known health hazards of smoking. The higher 8OHdG excretion in men and lean subjects may be related to a higher rate of metabolism with increased availability of reactive oxygen species. The apparent 7-fold individual variation in oxidative DNA damage carries implications regarding the rate of ageing and the risk of cancer and other degenerative diseases. The excretion of 8OHdG into urine offers a valuable tool for testing such hypotheses in humans.
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                Author and article information

                Journal
                Molecular and Cellular Biochemistry
                Mol Cell Biochem
                Springer Science and Business Media LLC
                0300-8177
                1573-4919
                July 2005
                July 2005
                : 275
                : 1-2
                : 85-94
                Article
                10.1007/s11010-005-0824-2
                16335787
                © 2005

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