Free Radical and Animal Nutrition

On Free radicals and Animal Nutrition "Life is a chemical process." This famous thesis put forward by chemist Lavasil in 1783 laid the theoretical foundation for the study of animal nutrition. Since then, in the process of animal nutrition research carried out for more than 200 years, many new theories and methods have been infiltrated into this field, so that the methods of animal nutrition research have been continuously improved and developed, and the content has become more abundant and in-depth. Free radical biology has developed rapidly for more than ten years, and its research scope and application to other life sciences have been expanded at a very rapid rate. As an aerobic organism, the production, clearance, utilization and harm of reactive oxygen species and the repair of biomolecule damage caused by reactive oxygen species, as well as the metabolism and function of nitric oxide (NO) and derived active nitrogen are not only the main contents of free radical biology research, but also must be paid attention to in animal nutrition and health care research. Some vitamins which are widely studied and used in nutrition: β-carotene, vitamin C and vitamin E, as sources of vitamin A, as well as some other antioxidants, are also indispensable components in the study of free radical biology. The research on free radicals and nutrition is increasing year by year, and its progress shows a new academic field and a new development direction at the molecular level and submolecular level. 1. The existence of free radicals in animals as early as 1931, Michalis proposed that the intermediate products of some enzymatic redox reactions are free radicals. His experimental evidence also shows that there may be free radicals in organisms. However, in the last 30 years of the rapid development of free radical biology, attention has been paid to the production and scavenging of free radicals in the body. At present, the increase in the production of endogenous free radicals and the weakening of their scavenging ability have been recognized as an important mechanism for the development and aggravation of radiation damage, and it has been recognized that free radicals are closely related to the occurrence and development of many diseases. A large number of studies show that biomolecules in animals include non-free radicals and free radicals. Reactive oxygen species are oxygen free radicals and their active derivatives. Its production, clearance, utilization and harm are the main contents of the initial research in the development of free radical biology. In 1987, the biological effect of nitric oxide was discovered [Palmerm et al., 1986]. Active nitrogen has also become the main research object of free radical biology. The biological effects of free radicals and their derivatives centered on O, N, C, S stone and other elements involve not only the reaction between free radicals, but also the reaction between free radicals and non-free radicals [Wink DA et al., 1998]. For example, NO combines with superoxide radicals to form substances with much higher activity than NO or superoxide radicals. ONOO-;ONOO- can also form highly active substances with CO2, and even split into free radicals and non-radicals [Squadrito GL et al. 1998]. (2) the relationship between nutrients and free radicals 2.1. In animals, nutrients are the material basis for the production of free radicals. Free radicals are produced by enzymatic or non-enzymatic reactions in animals, and their sources can be traced back to nutrients except O2. From the production process of nitric oxide in the body (see figure 1) [Marletta MA,1993], we can directly reflect the material basis of nutrients for the production of free radicals. This process is mainly an enzymatic reaction catalyzed by nitric ox-ide synthase synthase (NOS). The substrate is arginine and NADPH is a cofactor. Moreover, the biosynthesis of nitric oxide synthase requires amino acids, riboflavin, turquoise and other substances, as well as ATP to provide energy. The production of ATP inevitably involves nutrients: the metabolism of sugars, lipids and proteins (amino acids) as well as the participation of some vitamins. The study of free radicals must take into account the natural relationship between free radicals and nutrients. 2.2. nutrients are the source of free radicals in animals. Free radicals are constantly produced in animals and are constantly scavenged. Under normal circumstances, free radicals are always cleared and maintained at a very low level of balance. For example, reactive oxygen species can be eliminated to very low levels under the action of a variety of antioxidant enzymes, endogenous antioxidants and exogenous antioxidants. The body needs to maintain these antioxidant enzymes, endogenous antioxidants and exogenous antioxidants in a certain concentration, which inevitably involves the synthesis of protein and the metabolism of various nutrients. Superoxide dismutase (Cu,Zn-SOD;Mn-SOD), catalase (containing Fe) glutathione peroxidase (containing Fe and other antioxidant enzymes and macromolecular antioxidants such as metallothionein, ceruloplasmin and small molecular antioxidants such as glutathione) biosynthesis requires the participation of amino acids, mineral elements and ATP. Vitamins, the essential antioxidants in the body, are nutrients in themselves. Some endogenous selenium, copper and manganese are necessary trace elements for the biosynthesis of glutathione peroxidase (GSH-Px) and superoxide dismutase (Cu,Zu-SOD;Mn-SOD). When animals are deficient in selenium, myocardial GSH-Px activity decreases, even decreased antioxidants, such as uric acid, are derived from nutrients metabolite in the body. Animal malnutrition may lead to the increase of free radical production in the body, and may also affect the biosynthesis of various antioxidant enzymes and the production level of endogenous antioxidants because of malnutrition, thus further increasing the number of free radicals in the body. Some scholars have observed (Robinson et al., 1997) that the production of O2 in the liver of rats with nutritional deficiency increases, while the level of glutathione (GSH) decreases. Dabbagh et al (1994) found that excessive iron intake could decrease the level of antioxidants and increase the level of reactive oxygen species in experimental rats, and lipid peroxidation caused by reactive oxygen species. Hammrmueller et al (1984) pointed out that zinc and copper deficiency can increase the activity of NADPH-dependent cytochrome Pmur450 reductase in rat liver and lung microsomes, resulting in an increase in the production of reactive oxygen species, resulting in lipid peroxidation. Malnutrition or malnutrition may also induce inflammation or other complications, resulting in the production of NO and its derived reactive nitrogen and reactive oxygen species [Wepnir,2000]. 95%, resulting in peroxidation damage and mitochondrial dysfunction. If selenium is added, the decrease of GSH-Px activity can be reduced, and the deficiency of selenium can be improved. Chow et al. (1973) observed that there was a parallel relationship between the activity of GSH-Px in animal tissue and the supply of selenium in diet. The results showed that the activity of Cu,Zn-SOD in copper deficiency animals decreased, and manganese deficiency led to the decrease of Mn-SOD activity in animal tissues. Dietary vitamin deficiency also affects the biosynthesis of antioxidant enzymes. For example, Housewirsh et al. (1975) found that catalase activity decreased in the liver of experimental rats with dietary vitamin E deficiency. The level of non-enzymatic antioxidants in animals mainly depends on their production and decomposition in the body. The levels of metallothionein, ceruloplasmin, selenoprotein and redox protein are determined by their biosynthesis and their metabolic decomposition rate, while the amount of uric acid varies with metabolism. Glutamate hepatopeptide (GSH) is an important antioxidant in vivo and its oxidation product is GSSH. The ratio of GSH/GSSH can reflect the antioxidant defense ability of the body. The decrease of GSH level and GSH/GSSH ratio during malnutrition may be due to the weakening of GSH synthesis ability due to protein deficiency, the decrease of glutathione reductase activity and the weakening of catalytic ability to reduce GSSH to GSH during malnutrition. The ratio of NADPH/NADP in the body decreased due to nutritional status, which decreased the activity of glutathione reductase. Diet can provide a considerable amount of GSH for the body, and insufficient food supply can aggravate the decrease of GSH level in the body. In addition, it has been proved that vitamin B2 deficiency in animals can cause the decrease of glutathione reductase activity (Beutler,1969). 2.3 nutrients are the material basis for the repair of biomolecule damage caused by free radicals usually the free radicals produced in animals are not cleared to the range of physiological needs, but can only be maintained at a very low steady state level of normal balance, so they can still damage and important biomolecules, such as DNA. Protein from (enzyme) and biofilm. However, the body can repair or replace damaged biomolecules. The damaged protein can be degraded and its metabolites can enter the human amino acid pool to participate in protein synthesis. The substances needed in the process of repair or replacement of damaged biomolecules, such as nucleotides, amino acids, fatty acids, enzyme systems and cofactors as well as energy sources, are based on nutrients. Some natural antioxidants and some active components of non-nutrients in feed or food may also play a material role in the repair or replacement of biomolecules directly or indirectly. 2.4. Some nutrients can help animals adapt to oxidative stress and prevent and cure some animal diseases. Exogenous or endogenous stimulation can make the redox state tend to oxidation. Oxidative stress often leads to a decline in livestock and poultry production performance (for example, heat stress reduces the laying rate of laying hens), a decline in the quality of animal products (for example, PSE pork produced by slaughtering stress), and even animal diseases (such as ascites in broilers caused by environmental stress and nutritional stress). In production practice, in order to reduce the harm caused by oxidative stress, the amount of antioxidants (such as vitamin C, vitamin E) is often greatly increased in diet or drinking water. The appropriate nutrition level can also reduce and prevent the damage caused by physiological oxidative stress. Oxidative stress is often accompanied by the increase of reactive oxygen species, the increase of lipid peroxides, protein oxidative modification products and DNA damage products, and the consumption of antioxidant vitamins (such as vitamin E) and GSH, so the supply of antioxidant vitamins (such as vitamin E, C) and GSH should be increased accordingly. Experiments and production practice have proved that adding a large amount of vitamin E, ascorbic acid and other antioxidants to animals under stress conditions can help animals to resist oxidative damage, thus reducing the harm caused by oxidative stress. Bray (1993) suggested that attention should be paid to the level of GSH, nutritional status and oxidative stress in tissues. He believes that appropriate nutrition can not only increase the supply of exogenous GSH, but also regulate the level of tissue GSH, increase antioxidant capacity and prevent damage caused by reactive oxygen species. (3) pay attention to the harm of oxidative stress to animal production and strengthen the study of animal nutrition and free radicals. As an applied science, animal nutrition mainly focuses on the problems that need to be solved in production practice. however, forward-looking research and basic research often have more important and extensive guiding significance. The harm of oxidative stress has existed in a large number of livestock production, but people have studied it very superficial, have not fully realized the relationship between phenomenon and essence, and failed to find the key to solve the problem. On the other hand, we can also get inspiration from a large number of studies on determining animal vitamin requirements, and the development of animal nutrition must be further combined with more new disciplines and new technologies. the research on animal nutrition and free radicals should become an important part of animal nutrition research. -- Oh, new things about animal nutrition-- this is very good information and should be topped. I've been paying attention to the information about free radicals. Thank you very much. It is of practical value.