Studies On GPx4 Gene Expression And Antioxidative Properties Of Skeletal Muscle In Pigs

Pork quality is an important economic characteristic, and has become a primary focus for producers, researchers and consumers in recent years. Meat is sensitive to lipid oxidation, and pork skeletal muscle with higher activities of antioxidative enzymes would be less susceptible to lipid oxidation. Laiwu pig is one of Chinese native pig breeds, which has excellent germplasm properties such as high prolificacy and good meat quality.Living cells against oxidative processes by several mechanisms of protection, including antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx). The fact that GPx4 is amonomer may allow it to bind with the wider range of substrates than the tetrameric GPXs.The thesis is incloude two sections. In the first part, the main contents were that changes in major antioxidant enzymes activities and malonaldehyde contents of porcine M. longissimus during storage. And contents of the second part were effects of phospholipid hydroperoxide glutathione peroxidase mRNA expression on meat quality of M. longissimus dorsi in pigs and tissue expression profiles of GPx4 gene in Laiwu pigs. So, the aims of this thesis were to determine the changes of main antioxidative enzymes activities and MDA contents of porcine skeletal muscle during storage, and to determine the effects of phospholipid hydroperoxide glutathione peroxidase mRNA expression on meat quality of M. longissimus dorsi in pigs. The results were as follows:(1) The effects of storage temperatures on the major antioxidant enzymes activity and the lipid oxidation in porcine M. longissimus of Chinese native pigs (Laiwu pig) and Large White were investigated at 4 oC and 20 oC, for a period of 6 days. Measurements of the antioxidant enzymes included superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), and lipid oxidation was measured by determining the malonaldehyde (MDA) contents. Total 12 pigs (Laiwu pig: n=6; Large White: n=6) were used to measure the activities of SOD, CAT and GPx and to measure the MDA contents during storage. The results showed that the activities of the antioxidative enzymes decrease slightly during storage, regardless of temperature. But, the MDA contents of skeletal muscles were increasing during storage; the MDA contents of Laiwu pigs were significantly lower than Large White's. Furthermore, the activities of main antioxidative enzymes of Laiwu pigs were significantly higher than Large White's; the MDA contents of Laiwu pigs were significantly lower than Large White's, however. Correlations analysis showed antioxidant enzymes activity was negatively related to the MDA content. These results indicated that the skeletal muscle samples with the higher antioxidative enzymes activity would have the lower lipid oxidation.(2) Antioxidative enzymes protect muscle tissues against oxidation from reactive oxygen species, and increase the stability of the muscle. Phospholipid hydroperoxide glutathione peroxidase (GPx4) is an important antioxidant enzyme in muscle tissue. So the aim of this study was to identify the effects of mRNA expression level of GPx4 gene on meat quality properties in Longissimus dorsi of three pig breeds. Total 36 pigs (12 pigs for each breed) were used to measure the meat quality properties and to analysis the expression levels of GPx4 gene by quantitative real-time PCR.â‘ The results showed that meat quality, GPx4 activity and GPx4 mRNA levels were affected by pig breeds. There were the lowest expressible moisture, drip loss and cooking loss in Laiwu Pig among the three breeds, and also there were the highest GPx4 activity and the expression levels of GPx4 gene in Laiwu Pig compared with the other two pig breeds.â‘¡Analysis of meat samples divergent for water holding capacity identified highly negative associations between expressions levels of GPx4 gene and expressible moisture, drip loss and cooking loss. These results suggest that the higher mRNA expression level of GPx4 gene up-regulate the water holding capacity and the activity of GPx4, and the expression of GPx4 gene plays an important role in physiological changes related to the meat quality properties and the mechanisms of the antioxidantion of meat.â‘¢Five Laiwu pigs were used as experimental animal to determine the tissue expression files and total RNA was isolated from 10 tissues of Laiwu pig. The mRNA expression levels of GPx4 gene of different tissues were measured using quantitative real-time PCR, and the results showed that the rank order of the GPx4 mRNA expression was brain, heart, liver and spleen > muscle > spinal cord, large intestine, backfat and small intestine > lung. It was implied that GPx4 gene expressed ubiquitously in 10 tissues of Laiwu pigs, and played an important biological function.