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Whey protein isolate increases glutathione levels in human prostate epithelial cells |
K. D. KENT, J. A. Bomser, and W. J. Harper. Dept. of Food Science & Technology, Ohio State Univ., 2015 Fyffe Ct., Columbus, OH 43210-1007 Prostate cancer is the second leading cause of cancer death among American men. Studies suggest that dietary whey proteins may reduce the risk for cancer by increasing cellular levels of the antioxidant glutathione. Whey proteins are rich in cysteine, the hypothesized rate-limiting amino acid for glutathione synthesis. Supplementation with whey protein isolate may represent a means to increase glutathione synthesis within the prostate. The objective of this study was to determine the effect of whey protein isolate supplementation on glutathione levels in human prostate epithelial cells (RWPE-1). A hydrolysate of whey protein isolate (New Zealand Milk Products) was prepared by digesting the protein with trypsin, chymotrypsin, and peptidase (37°C, 60 min) and then heat inactivating the proteolytic enzymes (85°C, 10 min). RWPE-1 cells were treated with the hydrolyzed whey protein isolate (0-500 µg/ml) for 48 hrs, and glutathione levels were quantified using the Calbiochem glutathione assay kit. A time-course study was performed by treating cells with hydrolyzed whey protein isolate (500 µg/mL) and quantifying the glutathione levels at 0, 12, 24, and 48 hrs. As a positive control, RWPE-1 cells were treated with N-acetylcysteine (500 µM), a cysteine-rich compound known to increase glutathione levels. Treatment of RWPE-1 cells with hydrolyzed whey protein increased glutathione levels by 50% compared to controls (p<0.05). The increase in cellular glutathione was concentration dependent and was greatest at 12 hours post-treatment. Treatment with N-acetylcysteine also led to a 50% increase in glutathione levels compared to controls (p<0.05), suggesting that an increase in available cysteine is responsible for the elevation of glutathione within the prostate epithelial cells. The results of the study demonstrate that hydrolyzed whey protein isolate can significantly increase glutathione levels within the prostate epithelium. This represents a potential mechanism by which whey protein isolate can provide protection against the development of prostate cancer.
Session 73, Dairy Foods: Probiotics and bioactive components in milk
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