Fatty acids, dietary structures

Saturated fatty acids chemical structure, 639 dietary, 320,362-363 LDL cholesterol and, 364 Scavenger receptor A, 360,635 S cells, 65... 

The fatty acid composition of the structural lipids of the animal tissues used as food is remarkably uniform irrespective of the animal s diet or whether it is simple stomached or a ruminant (Table 5.2), although there are clearly some species differences and diet can influence membrane composition in subtle ways (sections 5.2.2 and 8.9). A predominant fatty acid is arachidonic acid, a member of the n-6 family, and meat provides most of our dietary supply of this fatty acid. Plant structural fats are similarly dominated by polyunsaturated acids and supply mainly a-linolenic acid, a member of the n-3 family. 

Coleoptera comprise the largest order of insects and accordingly pheromone structures and biochemical pathways are diverse [98, 99]. Beetle pheromone biosynthesis involves fatty acid, amino acid, or isoprenoid types of pathways. In some cases dietary host compounds can be converted to pheromones, but it is becoming apparent that most beetle pheromones are synthesized de novo. 

Dietary polyunsaturated fatty acids (PUFAs), especially the n-3 series that are found in marine fish oils, modulate a variety of normal and disease processes, and consequently affect human health. PUFAs are classified based on the position of double bonds in their lipid structure and include the n-3 and n-6 series. Dietary n-3 PUFAs include a-linolenic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) whereas the most common n-6 PUFAs are linoleic acid, y-linolenic acid, and arachidonic acid (AA). AA is the primary precursor of eicosanoids, which includes the prostaglandins, leukotrienes, and thromboxanes. Collectively, these AA-derived mediators can exert profound effects on immune and inflammatory processes. Mammals can neither synthesize n-3 and n-6 PUFAs nor convert one variety to the other as they do not possess the appropriate enzymes. PUFAs are required for membrane formation and function... 

Factors negatively affecting absorption of dietary fat may also be expected to negatively affect absorption of calcium. In the normal, healthy adult, dietary fat absorption is very efficient. However, such factors as level of dietary fat, fatty acid chain length, degree of fatty acid saturatedness, or triglyceride structure may have a measurable effect on calcium absorption under some circumstances. 

Approximately 60% of the dry weight of the brain is fat, a considerable proportion of which is polyunsaturated fatty acids that are present in plasma membranes. It would not be surprising if replacement of the unsaturated acids by the saturated fatly acids in membrane structure due to a dietary deficiency of polyunsaturated fatty acids played some part in development of mental illness. Indeed, it has been found that supplementation of a normal diet with polyunsaturated fatly acids can improve some mental disorder (see chapter 11). 

The provision of an appropriate fatty acid pool for use in synthesis of phospholipids involves a complex mixture of dietary and biosynthetic effects. To at least some extent, one is what one eats applies in the context of adaptation of lipid-containing structures, a point... 

The fatty acids of bovine milk fat arise from two sources synthesis de novo in the mammary glands and the plasma lipids originating from the feed. The fatty acids from these two sources differ in their structure. The fatty acids that are synthesised de novo are short-chain and medium-chain length acids, from 4 0 to 14 0 and also some 16 0, while the Cis fatty acids and some 16 0 arise from the plasma lipids. De novo fatty acid synthesis accounts for approximately 45% (w/w) of the total fatty acids in milk fat, while lipids of dietary origin account for the rest (Moore and Christie, 1979). 

CLA refers to a mixture of positional and geometric isomers of linoleic acid (cis-9, cis-12 octadecadienoic acid) with a conjugated double bond system. The structure of two CLA isomers is contrasted with linoleic and vaccenic acids in Figure 3.1. The presence of CLA isomers in ruminant fat is related to the biohydrogenation of polyunsaturated fatty acids (PUFAs) in the rumen. Ruminant fats are relatively more saturated than most plant oils and this is also a consequence of biohydrogenation of dietary PUFAs by rumen bacteria. Increases in saturated fatty acids are considered undesirable, but consumption of CLA has been shown to be associated with many health benefits, and food products derived from ruminants are the major dietary source of CLA for humans. The interest in health benefits of CLA has its genesis in the research by Pariza and associates who first demonstrated that... 

Absorption of dietary calcium is linked not only to the amount but also to the kind fatty acids in the diet of infants. In a controlled study, the fatty acid composition in one experimental formula was adjusted to simulate human milk, but the structure was dissimilar because the Ci6 o in the formula was mostly at the sn-3 rather than the sn-2 position. The greatest loss of calcium in the feces occurred when formulae with the wrong proportions of Ci6 0 and Ci8 o were fed. Fat absorption and calcium retention were highest in infants fed human milk, followed by infants fed formulae containing a high level of Ci2 o (Nelson et al., 1996, 1998). 

Provide needed molecular structures through dietary essential fatty acids (EFAs) and phospholipids. 

The effects of Caprenin, another structured lipid, on chylomicron fatty acid composition and postprandial semm lipid concentrations have also been studied (178). It was found that there is a very low uptake of C8 0, C10 0, and C22 0 into chylomicrons. Moreover, a postprandial lipemia after caprenin is comparable with that produced by other dietary fats as opposed to a fat-free meal. There is considerable... 

Oleic safflower oU displays most of the same characteristics as the linoleic type, except for its fatty acid structure (see Table 2). It has been noted that a blend of linoleic and oleic edible oUs would improve the dietary value of commercial safflower oil (83). Blends of this type began to be marketed in Japan in 1990 and appear to be achieving good acceptance by the public. 

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