MEDICAL HYPOTHESIS Oxidative stress in the animal model: the possible protective role of milk serum protein Nicola Traverso • Emanuela Balbis • Samir G. Sukkar • Annalisa Furfaro • Anna Massa Sacchi-Nemours • Claudia Ferrari • Stefania Patriarca • Damiano Cottalasso Received: 8 February 2010 / Accepted: 1 March 2010 / Published online: 27 May 2010 Ó Springer-Verlag 2010 Abstract In the field of biology, free radicals which are derived from the incomplete reduction of oxygen take on great importance; they belong to the so called reactive oxygen species, whose production in the organism is an inevitable consequence of various external or internal factors to which it is exposed. Once free radicals are generated they are often capable of giving rise to chain reactions. A lot of biological molecules are susceptible to the attack by free radicals including lipids, proteins, car- bohydrates and nucleic acids. Molecular alterations caused by the radical reactions have been frequently studied and are considered as pathogenetically main passages in the development of many diseases and ageing. In order to face a radical attack, living organisms have developed several biological defensive systems against it: the main ones are represented by anti oxidizing molecules and by enzymatic anti oxidizing systems. Among the various defence sys- tems, glutathione stands out as the principal guarantor of homoeostatic intra-cellular oxidation–reduction. One of glutathione’s most important functions is to act as cysteine ‘‘tank’’; this amino acid is extremely unstable in the extra- cellular environment and it rapidly auto-oxidates. Whey proteins (WP) are particularly rich in cysteine (cys) and in glutamine (glu) and therefore potentially capable of increasing the organism’s antioxidant defences. It is thought that the principal mechanism which allows WPs to exert their properties is through the contribution of cys and glu, which is rich in these proteins and is used intra- cellularly for the synthesis of glutathione. A diet based on milk serum proteins which supplies a superior quantity of cys, allows for a greater synthesis of hepatic glutathione in oxidative stress conditions. The use of ultra-filtrated WP could represent a useful tool in the control of oxidative stress in numerous pathological situations. Keywords Whey proteins (WP)  Glutathione  Antioxidant defences  Oxidative stress  ROS (reactive oxygen species)  Free radicals Free radicals Free radicals are by definition molecules or fragments of molecules that contain an odd electron on their outer orbit. In many instances their extreme reactivity is characteristic as they often pair up the odd electron with another one belonging to another molecule [1, 2]. They can behave like acceptors of electrons (oxidants) or as donors (reductors). Free radicals’ stability is extremely variable. There are free radicals which only live for nanoseconds (CH 3 • ), others milliseconds (O 2 -• ) and others which are stable for a long time as they are capable of de-localizing the odd electron by creating resonant structures, the free radicals reactivity depends upon these characteristics. In the field of biology those free radicals which are derived from the incomplete reduction of oxygen take on great importance. They belong to the so called ROS (reactive oxygen species), which are represented by radical hydroxyl (OH • ), super oxide anion (O 2 -• ) as well as the oxygen singlet ( 1 O 2 ) and hydrogen peroxide (H 2 O 2 ); despite the fact that the N. Traverso  E. Balbis  A. Furfaro  S. Patriarca  D. Cottalasso Pathology Institute, Genoa University, Genoa, Italy S. G. Sukkar (&)  A. M. Sacchi-Nemours  C. Ferrari Dietetics and Nutritional Unit, San Martino University Hospital, Largo R. Benzi 2, 16132 Genoa, Italy e-mail: samir.sukkar@hsanmartino.it 123 Mediterr J Nutr Metab (2010) 3:173–178 DOI 10.1007/s12349-010-0011-1