Polyunsaturated fatty acids , vitamin

Pyridoxal phosphate has a clear role in lipid metabolism as the coenzyme for the decarboxylation of phosphatidylserine, leading to the formation of phosphatidylethanolamine, and then phosphatidylcholine (Section 14.2.1), and membrane lipids from vitamin Bg-deficient animals are low in phosphatidylcholine (She et al., 1995). It also has a role, less well defined, in the metabolism of polyunsaturated fatty acids vitamin Bg deficiency results in reduced activity of A desaturase and impairs the synthesis of eicosapentanoic and docosahexanoic acids (Tsuge et al., 2000). 

For these reasons alone, a vitamin E symposium will not be short of problems and material for discussion. Many more unanswered questions come to light, however, when the biochemical and physiological properties of vitamin E are considered. The program of this meeting includes papers on the metabolism of vitamin E interrelations among vitamin E, metals, and ubi( uinones vitamin E and nucleic acid metabolism interrelations between vitamin E and polyunsaturated fatty acids vitamin E requirements of human infants vitamin E in health and disease of poultry, sheep, cattle, and pigs and so on. Everywhere, alongside established facts, there are unanswered questions and unsolved problems. 

Body cells become damaged over time by attacks from molecules known as free peroxide radicals, i.e. unstable, oxygen-containing compounds which are released during metabolism of pol5mnsaturated fatty acids. Free radicals can play a role in a number of diseases by allowing harmful compounds to enter the cell through ieaky cell membranes injured by peroxidation of the membrane s polyunsaturated fatty acids. Vitamin E and other anti-oxidants trap free radicals and interrupt this chain reaction oxidative destruction. 

Com oil s flavor, color, stabiHty, retained clarity at refrigerator temperatures, polyunsaturated fatty acid composition, and vitamin E content make it a premium vegetable oil. The major uses are frying or salad appHcations (50%) and margarine formulations (35%). 

The main function of vitamin E is as a chain-breaking, free radical trapping antioxidant in cell membranes and plasma lipoproteins. It reacts with the lipid peroxide radicals formed by peroxidation of polyunsaturated fatty acids before they can establish a chain reaction. The tocopheroxyl free radical product is relatively unreactive and ultimately forms nonradical compounds. Commonly, the tocopheroxyl radical is... 

Figure 45-6. Interaction and synergism between antioxidant systems operating in the lipid phase (membranes) of the cell and the aqueous phase (cytosol). (R-,free radical PUFA-00-, peroxyl free radical of polyunsaturated fatty acid in membrane phospholipid PUFA-OOH, hydroperoxy polyunsaturated fatty acid in membrane phospholipid released as hydroperoxy free fatty acid into cytosol by the action of phospholipase Aj PUFA-OH, hydroxy polyunsaturated fatty acid TocOH, vitamin E (a-tocopherol) TocO, free radical of a-tocopherol Se, selenium GSH, reduced glutathione GS-SG, oxidized glutathione, which is returned to the reduced state after reaction with NADPH catalyzed by glutathione reductase PUFA-H, polyunsaturated fatty acid.)...

Fats are primarily important energy suppliers in the diet. Per gram, they provide more than twice as much energy as proteins and carbohydrates. Fats are essential as suppliers of fat-soluble vitamins (see p. 364) and as sources of polyunsaturated fatty acids, which are needed to biosynthesize eicosanoids (see pp. 48, 390). 

The main action of vitamin E in human tissue is to prevent oxidation of polyunsaturated fatty acids (PUFA), thereby protecting lipid and phospholipids in membranes. Vitamin E interacts syn-ergically with other nutrients, such as vitamin C, selenium, and zinc, which are also involved in the oxidation pathway. The recommended intake is strongly related to the quantity of PUFA consumption. Some studies [454-456] on animal models and epidemiological trials in human suggest... 

Vitamin E may be indicated in some rare forms of anemia such as macrocytic, megaloblastic anemia observed in children with severe malnutrition and the hemolytic anemia seen in premature infants on a diet rich in polyunsaturated fatty acids. Also anemia s in malabsorption syndromes have shown to be responsive to vitamin E treatment. Finally, hemolysis in patients with the acanthocytosis syndrome, a rare genetic disorder where there is a lack of plasma jS-lipoprotein and consequently no circulating alpha tocopherol, responds to vitamin E treatment. In neonates requiring oxygen therapy vitamin E has been used for its antioxidant properties to prevent the development retrolental fibroplasia. It should be noted that high dose vitamin E supplements are associated with an increased risk in allcause mortality. 

Marine fishes are rich sources of structurally diverse bioactive compounds including polyunsaturated fatty acids, polysaccharides, minerals, vitamins, antioxidants, enzymes, and bioactive peptides (Kim et ah, 2008). Marine fish-derived ACE inhibitory peptides have been purified from enzymatic digestion of various fish materials from Alaska pollack (Nakajima et ah, 2009), bonito (Fujita et ah, 2000 Hideaki et ah, 1993 Yokoyama et ah,... 

Sea animals are rich in soluble dietary fibers, proteins, minerals, vitamins, antioxidants, phytochemicals, and polyunsaturated fatty acids, with low caloric value. Polysaccharides from marine animals have been reported to possess biological activities with potential medicinal values in addition to their current status as a source of dietary fibers and prebiotics. Moreover, they have a lot of dietary fiber, which lowers blood cholesterol, and iodine, which improves metabolism, vascular and cardiac action, body temperature, and perspiration regulation, and are effective in... 

Regarding the compositional differences shown for animal products, whether they are important for health depends, as for the plants, on the overall composition of the diet of the people who eat them. The vitamin E content in milk is far too small for relevant differences to affect health (Nielsen ef al. 2004), and too little is known about the dose-response relations of the impact of conjugated linoleic acids on health. However, the increased vitamin E level may still be important to prevent oxidation of the fat, a problem that can be exacerbated by increased levels of polyunsaturated fatty acids (Dhiman ef al. 1999, Nielsen ef al. 2004). However, while oxidised milk is clearly not good for health, its rancid taste and smell allows detection and rejection before consumption and thus prevents harm to health, similar to plant toxicants. Also in line with the plants, while the use of roughage is clearly more extensive in organic farming, some conventional farmers use almost identical feed compositions and are therefore likely to produce the same quality of products in this respect. 

The E vitamins consist of eight naturally occurring tocopherols, of which a-tocopherol is the most active (Figure 28.28). The primary function of vitamin E is as an antioxidant in prevention of the nonenzymic oxidation of cell components (for example, polyunsaturated fatty acids) by molec ular oxygen and free radicals. 

Vegetable oils are rich sources of vitamin E, whereas liver and eggs contain moderate amounts. The RDA for a-tocopherol is 10 mg for men and 8 mg for women. Vitamin E requirement increases as the intake of polyunsaturated fatty acid increases. 

In terms of composition, Table 7.5 shows that milk fat consists primarily of triglycerides with small amounts of di- and monoglycerides, phospholipids, sterols such as cholesterol, carotenoids, fat-soluble vitamins A, D, E, and K, and some traces of free fatty acids (Renner 1983 Christie 1983). The fatty acid composition of bovine milk fat is characterized by a high proportion of saturated fatty acids (60 to 70%), appreciable amounts of monounsaturated fatty acids (25 to 35%), and small amounts of polyunsaturated fatty acids (4%) (Lampert 1975). Milk fat... 

Vitamin E (a-tocopherol) (fig. 10.26) was recognized in 1926 as an organic-soluble compound that prevented sterility in rats. The function of this vitamin still has not been clearly established. A favorite theory is that it is an antioxidant that prevents peroxidation of polyunsaturated fatty acids. Tocopherol certainly prevents peroxidation in vitro, and it can be replaced by other antioxidants. However, other antioxidants do not relieve all the symptoms of vitamin E deficiency. 

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