Whey, a protein complex obtained from milk, is being touted as a functional product with a number of health advantages. Hydrolysis of whey protein with enzymes is known to affect positively on its functionalities. The present study evaluated the effect of whey proteins hydrolysates (WPH) on oxidative DNA damage induced by H₂O₂ and DNA repair capacity in human leukocytes. WPHs were produced using enzymes such as alcalase, flavorzyme, neutrase, and protamex incubated for 3 hrs. Human leukocytes were incubated in medium with PBS (negative control) or with WPHs (5∼100Ռg/ml), whey protein concentrate (WPC), vitamin C, and E for 30 min at 37°C were further treated with H₂O₂ (200ՌM) as an oxidative stimulus for 5 min on ice. Oxidative damage was evaluated by Comet assay. An increased oxidative DNA damage by H₂O₂ expressed by tail intensity was significantly inhibited by pre-incubating with all tested WPHs and the inhibitory ability was over 70% even in lowest concentration (5Ռg/ml) in every WPHs treatment. The protective effect of WPHs on DNA damage was superior to that of intact WPC, vitamin C or E. The addition of WPHs to human leukocytes after 5 min of H₂O₂ (200ՌM) positively influenced the kinetics of DNA repair in 4 hrs of incubation. At longer exposition times (24 hrs), however, no positive effect of WPHs on DNA repair was observed. The DNA repair capacity was also more effective in WPHs treatment than in WPC treatment. These results indicate that whey proteins hydrolysates provides prevention against oxidative DNA damage and stimulation of DNA repair which would decrease the risk of mutagenic changes leading to cancer. (Cancer Prev Res 14, 146-152, 2009)

Keywords: Whey protein hydrolysates, Oxidative stress, DNA damage, DNA repair, Comet assay