Effect of whey protein hydrolysates produced by various enzymes on H2O2 induced DNA damage in human leukocytes

Whey, a protein complex obtained from milk, is being touted as a functional product with a number of health advantages [1–3]. Whey proteins are defined as proteins in milk that remain soluble after acid or rennet casein precipitation. In this study, we evaluated the effect of whey proteins hydrolysates (WPH) on oxidative DNA damage induced by H₂O₂ in human leukocytes. WPHs were produced using protease such as neutrase, alcalase, flavorzyme, and protamex incubated for 4 hrs. Human leukocytes incubated in medium with PBS (negative control) or with WPHs (5, 10, 50, and 100µg/ml) for 30min at 37°C were further treated with H₂O₂ (200µM) as an oxidative stimulus for 5min on ice. Oxidative damage was evaluated by Comet assay (single-cell gel electrophoresis). An increased oxidative DNA damage by H₂O₂ expressed by % tail DNA was significantly inhibited by pre-incubating with all tested WPHs at concentration of 5–100µg/ml. The concentrations that would produce a 50% reduction in DNA damage as estimated from the regression equations were, in increasing order of efficacy, WPH-protamex (14.1µg/ml), WPH-alcalase (10.8µg/ml), WPH-flavozyme (10.6µg/ml), WPH-neutrase (8.4µg/ml). The protective effect of WPH was more than that of vitamin E, vitamin C, and non-hydrolyzed WP. These results indicate that whey proteins hydrolysates to human leukocytes followed by H₂O₂ treatment inhibited damage to cellular DNA, supporting a protective effect of whey proteins hydrolysates against oxidative damage.

References: 1. Sindayikengeras, S., Xia, W.S. (2006). J. Zhejiang University Sci B 7: 90–98.

2. Ewan, Ha. and Michael, B.Z. (2003)J. Nutr. Biochem. 14: 251–258.

3. Tong, L.M., et al. (2000)J. Agric. Food Chem. 48: 1473–1478