Trans Fatty acids atherosclerosis

Small amounts of trans-unsamrated fatty acids are found in ruminant fat (eg, butter fat has 2-7%), where they arise from the action of microorganisms in the rumen, but the main source in the human diet is from partially hydrogenated vegetable oils (eg, margarine). Trans fatty acids compete with essential fatty acids and may exacerbate essential fatty acid deficiency. Moreover, they are strucmrally similar to samrated fatty acids (Chapter 14) and have comparable effects in the promotion of hypercholesterolemia and atherosclerosis (Chapter 26). 

Figure 22.6 How various factors increase the risk of atherosclerosis, thrombosis and myocardial infarction. The diagram provides suggestions as to how various factors increase the risk of development of the trio of cardiovascular problems. The factors include an excessive intake of total fat, which increases activity of clotting factors, especially factor VIII an excessive intake of saturated or trans fatty acids that change the structure of the plasma membrane of cells, such as endothelial cells, which increases the risk of platelet aggregation or susceptibility of the membrane to injury excessive intake of salt - which increases blood pressure, as does smoking and low physical activity a high intake of fat or cholesterol or a low intake of antioxidants, vitamin 6 2 and folic acid, which can lead either to direct chemical damage (e.g. oxidation) to the structure of LDL or an increase in the serum level of LDL, which also increases the risk of chemical damage to LDL. A low intake of folate and vitamin B12 also decreases metabolism of homocysteine, so that the plasma concentration increases, which can damage the endothelial membrane due to formation of thiolactone.

Despite the fact that trans fatty acids are unsaturated, their contributions to atherosclerosis are similar to those of saturated fats. This similarity in physiologic action can be attributed to which of the following ... 

The answer is B. Saturated fatty acids and trans fatty acids are structurally similar their hydrocarbon tails are relatively linear. This allows them to pack tightly together in semi-crystalline arrays such as the membrane bilayer. Such arrays have similar biochemical properties in terms of melting temperature (fluidity). Although some of the other properties listed are also shared by saturated and trans fats, they are not thought to account for the tendency of these fats to contribute to atherosclerosis. 

Trans-Isomers and Coronary Heart Disease An increased risk of developing heart disease has been linked to an intake of trans-fatty acids (223). The replacement of dietary saturated fatty acids by trans-fatty acids, for example, lowers serum HDL cholesterol and impairs endothelial function in healthy men and women (224). It also impairs flow-mediated vasodilation and decreases the activity of serum paraoxonase, which is an HDL-bound esterase that may protect against atherosclerosis (225). 

Kritchevsky, D. (1982). Trans fatty acid effects in experimental atherosclerosis. Journal of Federation Proceeding, 41(11), 2813-7. 

Willett, W. C. (2006). Trans fatty acids and cardiovascular disease-epidemiological data. Atherosclerosis Supplements, 7(2), 5-8. 

Recent studies have shown that consuming a significant amount of trans fatty acids can lead to serious health problems related to serum cholesterol levels. Low overall serum cholesterol and a decreased ratio of low-density lipoprotein (LDL) cholesterol to high-density lipoprotein (HDL) cholesterol are associated with good overall cardiovascular health. High semm cholesterol and an elevated ratio of LDL cholesterol to HDL cholesterol are linked to a high incidence of cardiovascular disease, especially atherosclerosis. Research has indicated that diets high in either saturated fatty adds or trans fatty adds raise the ratio of serum LDL cholesterol to HDL cholesterol and substantially increase the risk of cardiovascular disease. 

Hydrogenization may have one drawback. It converts the naturally-occurring cisfatty acids to transfatty acids. The prefixes CIS and trans refer to the orientation of the atoms around the double bond. The trans form of essential fatty acids does not function eis an essential fatty acid in the E dy. Also, some researchers have found that (1) trans fatty acids are not as effective eis their cis analogs in lowering blood cholesterol, and (2) fats rich in trans fatty acids appear to promote atherosclerosis. ... 

WiUett, W.C. 2006. Trans fatty acids and cardiovascular disease— Epidemiological data. Atherosclerosis Supp. 7 5—8. 

Despite the reported effects of trans fatty acids on blood lipoproteins, experiments with laboratory animals have not provided evidence that dietary trans fatty acids are associated with the development of experimental atherosclerosis, provided that the diet contains adequate levels of linoleic acid. Similarly, there is no evidence that trans fatty acids raise blood pressure or affect the blood coagulation system. However, there has been no thorough evaluation of the effect of trans fatty acids on the coagulation system, and this is an area worthy of investigation. 

Miwa and Yamamoto (31) described a simple and rapid method with high accuracy and reliability for the determination of C8 0-C22 6 fatty acids, which occur in esterified forms in dietary fats and oils and in living cells [the biological effects of routinely consumed fats and oils are of wide interest because of their impact on human health and nutrition (28,29), in particular, the ratio of cu-3 polyunsaturated fatty acid to w-6 polyunsaturated fatty acids (w-3/cu-6) seems to be associated with atherosclerosis and breast and colon cancers (30)]. They report improved separation of 29 saturated and mono- and polyunsaturated fatty acids (C8-C22), including cis-trans isomers and double-bond positional isomers, as hydrazides formed by direct derivatization with 2-nitrophenylhydrazine hydrochloride (2-NPH HC1) of saponified samples without extraction. The column consisted of a J sphere ODS-M 80 column (particle size 4 /xm, 250 X 4.6-mm ID), packed closely with spherical silica encapsulated to reach a carbon content of about 14% with end-capped octadecyl-bonded-spherical silica (ODS), maintained at 50°C. The solvent system was acetonitrile-water (86 14, v/v) maintained at pH 4-5 by adding 0.1 M hydrochloric acid with a flow rate of 2.0 ml/min. Separation was performed within only 22 min by a simple isocratic elution (Fig. 6). The resolution of double-bond positional isomers, such as y-linolenic ( >-6) and a-linolenic acid ( >-3) hydrazides and w-9, >-12, and >-15 eicosenoic acid hydrazides was achieved by use of this column. 

Hydrogenation of vegetable oils produces a mixture of cts and trans unsaturated fatly acids. The trans unsaturated fatty acids are thought to contribute to atherosclerosis (hardening of the arteries). 

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