Effects Of Oxidized Soybean Protein On The Redox State And Liver Gene Expression In Mice

During the process and storage, food protein is prone to be oxidized influenced by unsaturated fatty acids,metal ions,flavor,oxidative enzymes and other promoting oxidation components. Protein oxidation causes changes in protein structure and physical and chemical properties, but there was no report whether the dietary oxidized protein would cause changes in physiological activity of the body. In this paper, effects of soy protein modified by the heating and lipid peroxidation product MDA on the redox state and liver gene expression in mice were investigated.The soybean protein was heated at 100℃for different time(30,60,90min) or oxidized by different MDA doses(0.1,10,50,100 mmol/L).Then the carbonyl content, antioxidant capacity and digestibility of oxidized protein were measured in vitro. To investigated the impact of free radicals in the blood, mice were consumed an ordinary diet filled the stomach heating 90 min protein. The mice were divided into 4 groups, consumed an ordinary diet with fresh protein, a MDA oxidized protein diet, a heating protein diet, or a heating protein plus 0.08% LA diet. The digestibility experiment was carried out at the third week. Then the level of ROS and redox-related indicators(T-AOC,MDA,SOD,GSH-Px and CAT)were determined one week later. The liver gene chip was used to examine the effects of oxidation on the gene expression profile and figure out the genes and pathway activated by oxidation. Finally, the gene expressions in liver and jejunum were examined by RT-PCR.The results were as follows: (1) The increase of MDA concentration or heating time can lead an increase of soy protein carbonyl content as well as a decrease of DPPH·scavenging ability. (2) The protein digestibility of oxidative soy protein was decreased and MDA oxidation decreased significantly. (3) The level of free radicals in blood of mice filled with the stomach heating 90min protein was higher than the control. (4) Oxidation caused a decrease of protein and an increase of fat digestibility, while adding LA increased protein digestibility significantly and the fat digestibility non-significant increased. (5) The lever of ROS in blood and tissues were increased by oxidized protein diet. Compared with the control group, the anti-oxidation of heating or MDA oxidized protein group was significantly decreased. LA could increase the anti-oxidation index of mice and eliminate reactive oxygen species actively. (6) The gene chip showed that oxidation can change lipid metabolism,immune system,endocrine system,environmental information processing,disease and other pathways in the liver. LA addition can cause change gene pathway restore or partially restore to normal levels. (7) The oxidized protein induced a decrease in metabolism of fat synthesis-related genes such as SREBP-1c,ACC,while ACOX1 and PPARαgene expression was up-regulate which prompt fatty acidβ-oxidation and adding 0.08% LA can restore or in part restore the level of gene expression to normal level. In addition to ACOX1 of heating oxidation group, PPARαand SREBP-1c gene expression in jejunum showed the similar trend as in liver.