Polyunsaturated fatty acids, defined

It is now widely appreciated that polyunsaturated fatty acids (PUFAs) are highly susceptible to oxidative damage. Indeed, the process of lipid peroxidation was broadly defined as the oxidative deterioration of polyunsaturated lipids by Tappel (1979). The presence of a double... 

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. 

Figure 9.21 Polyunsaturated fatty acid (PUFA) concentrations in water volume (,ug L-1) and POC (ug mg-1 OC) in San Francisco and Chesapeake Bay (SFB) from 1992 to 1993 and 1995 to 1996, respectively. Bloom conditions are defined as Chl-a > 10 ug L-1. High and low flow conditions were only tested for SFB. (Modified from Canuel, 2001.)...

Lipid peroxidation is a free radical-mediated, chain reaction resulting in the oxidative deterioration of polyunsaturated fatty acids (PUFAs) defined for this purpose as fatty acids that contain more than two double covalent carbon-carbon bonds. Singlet oxygen can produce lipid hydroperoxides in unsaturated lipids by non-radical processes (Pryor and Castle, 1984), but the reaction usually requires a radical mechanism (Porter, 1984). Polyunsaturated fatty acids are particularly susceptible to attack by free radicals. Lipid peroxidation is a complex process, and three distinct phases are recognized (a) initiation, (b) propagation and (c) termination (see Fig. 2.10). 

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). 

Bourre J, Faivre A, Dumont O, et al. Effect of polyunsaturated fatty acids on fetal mouse brains in culture in a chemically defined medium. J Neurochem 1983 41 1234-1242. 

Polyunsaturated fatty acids and especially arachidonic acid are highly susceptible to lipid peroxidation, which leads to the generation of lipid hydroperoxides, which then undergo carbon-carbon bond cleavage giving rise to the formation of short chain, unesterified aldehydes and aldehydes still esterified to the parent lipid, termed core-aldehydes (Esterbauer et al. 1987). Considerable progress has been made in recent years in dissecting the molecular structures of OxPL, which consequently allowed for the experimental use of defined compounds rather than complex lipoproteins and lipid mixtures. 

Plants are the principal sources of the polyunsaturated fatty acids linoleic and o -linolenic acids. When we consider that all leaf tissues contain high levels of these acids, it is clear that they are the most abundant unsaturated fatty acids in the world. However, just as the synthesis of cellulose, the most abundant polysaccharide in the world, is poorly understood at present, so the synthesis of these two polyunsaturated fatty acids is not well-defined. Oleic acid biosynthesis, in sharp contrast, is quite well documented. 

The TG in nanosized emulsions may be presented structurally in long or medium chains respectively, named LCT and MCT. The mean diameter of particles in LCT emulsions is greater than that in MCT emulsions [29], LCT contains fatty acid chains with 14, 16,18, 20, and 22 carbon atoms and sometimes with double bonds. The number of double bonds present defines the fatty acids in LCT as saturated, mono-unsaturad, or polyunsaturated. If the first double bond is on carbon number 3,6, or 9 from the methyl end of the carbon chain, then the fatty acid is n-3, n-6, or n-9, respectively. Purified soybean or safflower oil contains LCT with a high proportion... 

As regards fat labeling, the nutrition panel must include total fat, calories from fat, saturated fat, and cholesterol. Declaration of polyunsaturated or monounsatu-rated fat content are mandatory only if the other is declared or if a claim about fatty acids or cholesterol is made, unless the product meets the criteria for a fat-free claim. All fat amounts are expressed to the nearest 0.5-g increment below 5 g, to the nearest gram above 5 g, and as zero if a serving contains less than 0.5 g. Saturated fat includes all fatty acids that do not contain a double bond. Polyunsaturated fat includes only cis, cri-methylene-interrupted fatty acids, and monounsaturated fat is defined as cis-monounsaturated fatty acids. Saturated, polyunsaturated, or monounsaturated fat is declared as weight of the fatty acids, while fat is expressed as the weight of triglyceride based on the total amount of lipid fatty acids. 

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