Effects Of Oxidized Casein On The Redox State And Memory Capacity Of Mice

Whether the proteins in food or the body are susceptible to oxidative attack. During the food processing and storage, protein can be easily modified by ROS or other factors, resulting in physical and chemical properties and functional changes. The protein in the body can be also targeted by ROS, leading to some diseases. The casein protein is studied for the effect of intaking oxidation casein on body.Research:⑴casein was heated at 100℃(0, 30, 60, 90 min) and malondialdehyde (MDA) oxidation (MDA final concentration 0, 0.2, 20, 200mmol/L), then determined carbonyl, sulfhydryl content and surface hydrophobicity changes.⑵the normal casein, heating oxidation(30,60,90min)casein, MDA oxidation(MDA final concentrations 0.2, 20, 200mmol/L) casein were digested with pepsin-trypsin hydrolysis step. At 1,12,18h of the trypsin hydrolysis time, the hydrophobicity of hydrolysates was determined⑶the normal casein, heating oxidation (30,90 min) casein were hydrolysised by the method of⑵, and at 1,2, 4, 8,12,18h of the trypsin hydrolysis time, the DPPH ? and ? OH removal capacity of hydrolysates was measured.⑷The mice were divided into four groups: ig 0.2ml of normal saline, normal casein, heating oxidated casein, MDA oxidated casein. The production of free radical (FR) in blood of mice were detected respectively at 0,30,60,90,120,160min after administration; the plasma peptides were detected by HPLC-MS, the redox-related indicators(T-AOC,MDA,GSH)in Liver, Jejunum, Duodenum were determined.⑸Thirty of 4 weeks old ICR male mice, after pre-feeding for one week, were randomly divided into 3 groups and fed of normal casein diet, heating oxidated casein diet, MDA oxidated casein diet. 8 weeks later , behavioral experiments were carried on. Then the ROS levels in blood and tissues were measured. The redox-related indicators (CAT, T-AOC, GSH-PX, GSSH/GSH, MDA),and the protein oxidation indicators (double-tyrosine, AOPP )were also determined.Results⑴The carbonyl content of casein increased and free thiol groups content decreased with the MDA concentration or heating time. The surface hydrophobicity was lower in heated casein than that of normal casein , but higher in MDA oxidized casein.⑵For the hydrolysis of heating oxidation casein, the hydrophobic value was increasing with the hydrolysis time, and the higher the heating degree of oxidation, the higher the hydrophobicity was. MDA oxidation showed the same trend.⑶For the hydrolysates of casein heating oxidated of 30,90 min , the capacity of removeing DPPH ? and ? OH was lower than that of normal casein.⑷The FR peak of blood appeared at 160min. The FR of blood was significantly higher in mice administered oxidized casein than that of normal casein. The T-AOC,GSH content of liver, jejunum and duodenum decreased ,but MDA increased in mice ig with oxidized casein. HPLC-MS analysis showed that composition of plasma peptides were different in the plasma of mice ig MDA oxidized casein group with nomal casein, new C7H15N4O substances containing carbonyl appeared in plasma.⑸Mice fed of heating /MDA modified casein showed worse spatial memory and orientation ability in behavioral experiments compared with mice fed of normal casein. The ROS level and MDA content, GSSH/GSH in blood and tissues of mice fed of heating/MDA oxidation casein were significantly increased than that of mice fed of normal casein, however , the total antioxidant capacity(T-AOC)and antioxidant enzyme(GSH-PX,CAT)decreased significantly (P<0.05). The double tyrosine and AOPP in the tissues of mice fed of heating/MDA oxidation casein increased significantly than that of mice fed of normal casein(P<0.05). It was indicated that intaking oxidation casein can cause oxidative stress in the body and the protein oxidation products accumulation in some organs.