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Protective Effect of Grape Seed Polyphenols against High Glucose-Induced Oxidative Stress.

The incidence of diabetes is increasing rapidly in developed countries, mainly because of wrong diet and lack of exercise. Diabetes is not only an inconvenient disease involving complicated medication but also it can cause damage to different organs. Previous studies have shown that resveratrol, a main phytochemicals in the seeds and skin of grapes and some medicinal plants, has chemoprotective effects on human cancer cell lines and has antioxidant and anti-inflammatory activities. One study showed that resveratrol reduced glucose by myelocytic cells. The aim of this study was to determine if grape seed polyphenols could be used to treat diabetes mellitus and to determine the optimal degree of polymerization (monomer, polymer, oligomers and oligonol). Epithelial kidney cells were cultured and subjected to high concentrations of glucose and to oxidative stress from oxidants, such as reactive oxygen species and nitric oxide. When endothelial cells grow in a medium with high glucose levels they will die because of apoptosis.

The researchers found that the addition of grape seed polyphenols improved the viability of cells exposed to high glucose level. The oligomers proanthocyanidins were more effective than the types of proanthocyanidins. The optimal dose of grape seed polyphenols was 10 ppm. The grape seed polyphenols also reduced the production of damaging reactive oxygen species and nitric oxide. The production of proteins involved in apoptosis, such as cyclooxygenase, nitric oxide synthases and BAX were modulated by the grape seed polyphenols. All types of proanthocyanidins inhibited the production of cyclooxygenases and nitric oxide synthases. All types of proanthocyanidins, except the monomer, showed slight inhibition of BAX production.

The researchers concluded that high glucose treatment induced oxidative stress and cytotoxicity in cultured kidney cells and that the proanthocyanidin oligomers of grape seed showed the strongest protective effect against this high glucose-induced oxidative stress.

Source: Fujii H, Yokozawa T, Kim YA, Tohda C and Nonaka GI. Protective Effect of Grape Seed Polyphenols against High Glucose-Induced Oxidative Stress. . Bioscience, Biotechnology and Biochemistry. 2006 September 7

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