Polyunsaturated fatty metabolism

Brain Coordination of the nervous system Glycolysis, amino acid metabolism Glucose, amino acid, ketone bodies (in starvation) Polyunsaturated fatty acids in neonate Lactate ... 

Kelly, F.J. (1991). The metabolic role of n-3 polyunsaturated fatty acids relationship to human disease. Comp. Biochem. Physiol. 23, 467-471. 

The brain has a number of characteristics that make it especially susceptible to free- radical-mediated injury. Brain lipids are highly enriched in polyunsaturated fatty acids and many regions of the brain, for example, the substantia nigra and the striatum, have high concentrations of iron. Both these factors increase the susceptibility of brain cell membranes to lipid peroxidation. Because the brain is critically dependent on aerobic metabolism, mitochondrial respiratory activity is higher than in many other tissues, increasing the risk of free radical Teak from mitochondria conversely, free radical damage to mitochondria in brain may be tolerated relatively poorly because of this dependence on aerobic metabolism. 

A variety of molecular indicators of the freshness (and perhaps nutritional quality) of organic matter exists. For example, certain labile phytoplankton constituents, such as polyunsaturated fatty acids, are readily degraded in the environment or in herbivore guts, and are thus depleted in more degraded particles (de Baar et ak, 1983 Wakeham and Canuel, 1988). Preferential loss of labile algal fatty acids resulting in the enrichment of more stable components in the products of heterotrophic metabolism has been observed in both field studies and laboratory feeding experiments (Prahl et ak, 1985 Wakeham and Canuel, 1988 Harvey et ak,... 

Particularly in the metabolism of the polyunsaturated fatty acids, the process of elongation occurs in sequence with desaturation to produce the specific acids required by the tissues in the body. 

Some cells require specific nutrients to maintain their function. These nutrients are included in some feeds for the patient to help fight disease and aid recovery. These are sometimes called nutraceuticals , a term which can be loosely defined as a fuel or substrate that is provided by the physician or surgeon as part of the treatment for a specific condition. They include nucleotides, arginine, cysteine, glutamine and polyunsaturated fatty acids. The metabolic bases for the beneficial effects are described in Chapter 15. A summary is given below. 

When trans-fatty acids are fed to rats with adequate amounts of essential fatty acids, they have little effect on growth, longevity, or reproduction, but when fed as the sole source of lipids they exaggerate the symptoms of essential fatty acid deficiency (111). An effect on the metabolism of long chain polyunsaturated fatty acids was noted however. 

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... 

Guengerich, F.P. (1994) Metabolism and genotoxicity of dihaloalkanes. Adv. Pharmacol., 27,211-236 Guha, S.N., Schoneich, C. Asmus, K.D. (1993) Free radical reductive degradation of vic-dibromoalkanes and reaction of bromine atoms with polyunsaturated fatty acids possible involvement of Br(.) in the 1,2-dibromoethane-induced lipid peroxidation. Arch. Biochem. 

Catalytic hydrogenation of vegetable oils is widely used to form harder fats and to decrease the content of polyunsaturated fatty acyl groups. The products have a greatly increased resistance to rancidity. However, they also contain fats with trans double bonds as well as isomers with double bonds in unusual positions.251 253 Such compounds may interfere with normal fatty acid metabolism and also appear to affect serum lipoprotein levels adversely. Trans fatty acids are present in some foods. One hundred grams of butter contain 4-8 g, but hydrogenated fats often contain much more. It has been estimated that in the United States trans fatty acids account for 6-8% of total dietary fat.253... 

Sanjuijo P., Ruiz J. I., and Montejo M. (1997). Inborn errors of metabolism with a protein-restricted diet effect on polyunsaturated fatty acids. J. Inherited Metab. Dis. 20 783-789. 

Lipids are of special concern in comparing plastic metabolism between the two groups of fish. Triacyl-glycerols, cholesterol ethers and non-esterified fatty acids, which are the direct sources of energy, have already been discussed in the previous section. We now turn to phospholipids and cholesterol, which are essential to the structure of cell membranes, and to polyunsaturated fatty acids, which determine to a large extent the functional activity of these membranes. 

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