Looking for books on BioChemistry Check our section of free ebooks and guides on BioChemistry now This page contains list of freely available Ebooks, Online. High density lipoprotein Wikipedia. High density lipoproteins HDL are one of the five major groups of lipoproteins. Lipoproteins are complex particles composed of multiple proteins which transport all fat molecules lipids around the body within the water outside cells. They are typically composed of 8. Apo. A more as the particles enlarge picking up and carrying more fat molecules and transporting up to hundreds of fat molecules per particle. OvervieweditHDL particles have long been divided into 5 subgroups, by densitysize an inverse relationship, which also correlates with function and incidence of cardiovascular events. Unlike the larger lipoprotein particles which deliver fat molecules to cells, HDL particles remove fat molecules from cells which need to export fat molecules. The lipids carried include cholesterol, phospholipids, and triglycerides amounts of each are quite variable. Increasing concentrations of HDL particles are strongly associated with decreasing accumulation of atherosclerosis within the walls of arteries. This is important because atherosclerosis eventually results in sudden plaque ruptures, cardiovascular disease, stroke and other vascular diseases. HDL particles are sometimes referred to as good cholesterol because they can transport fat molecules out of artery walls, reduce macrophage accumulation, and thus help prevent or even regress atherosclerosis. However, studies have shown that HDL lacking mice still have the ability to transport cholesterol to bile, suggesting that there are alternative mechanisms for cholesterol removal. TestingeditBecause of the high cost of directly measuring HDL and LDL protein particles, blood tests are commonly performed for the surrogate value, HDL C, i. Apo. A 1HDL particles. In healthy individuals, about 3. HDL. 3 This is often contrasted with the amount of cholesterol estimated to be carried within low density lipoprotein particles, LDL, and called LDL C. HDL particles remove fats and cholesterol from cells, including within artery wall atheroma, and transport it back to the liver for excretion or re utilization thus the cholesterol carried within HDL particles HDL C is sometimes called good cholesterol despite being the same as cholesterol in LDL particles. Those with higher levels of HDL C tend to have fewer problems with cardiovascular diseases, while those with low HDL C cholesterol levels especially less than 4. L or about 1 mmolL have increased rates for heart disease. Higher native HDL levels are correlated with better cardiovascular health 5 however, it does not appear that further increasing ones HDL improves cardiovascular outcomes. The remainder of the serum cholesterol after subtracting the HDL is the non HDL cholesterol. The concentration of these other components, which may cause atheroma, is known as the non HDL C. This is now preferred to LDL C as a secondary marker as it has been shown to be a better predictor and it is more easily calculated. Structure and functioneditHDL is the smallest of the lipoprotein particles. It is the densest because it contains the highest proportion of protein to lipids. Its most abundant apolipoproteins are apo A I and apo A II. A rare genetic variant, Apo. A 1 Milano, has been documented to be far more effective in both protecting against and regressing arterial disease atherosclerosis. The liver synthesizes these lipoproteins as complexes of apolipoproteins and phospholipid, which resemble cholesterol free flattened spherical lipoprotein particles, whose NMR structure was recently published 9 the complexes are capable of picking up cholesterol, carried internally, from cells by interaction with the ATP binding cassette transporter A1 ABCA1. A plasma enzyme called lecithin cholesterol acyltransferase LCAT converts the free cholesterol into cholesteryl ester a more hydrophobic form of cholesterol, which is then sequestered into the core of the lipoprotein particle, eventually causing the newly synthesized HDL to assume a spherical shape. HDL particles increase in size as they circulate through the bloodstream and incorporate more cholesterol and phospholipid molecules from cells and other lipoproteins, for example by the interaction with the ABCG1 transporter and the phospholipid transport protein PLTP. Biochemistry Of Lipids Lipoproteins And Membranes Pdf ViewerHDL transports cholesterol mostly to the liver or steroidogenic organs such as adrenals, ovary, and testes by both direct and indirect pathways. HDL is removed by HDL receptors such as scavenger receptor BI SR BI, which mediate the selective uptake of cholesterol from HDL. In humans, probably the most relevant pathway is the indirect one, which is mediated by cholesteryl ester transfer protein CETP. This protein exchanges triglycerides of VLDL against cholesteryl esters of HDL. As the result, VLDLs are processed to LDL, which are removed from the circulation by the LDL receptor pathway. The triglycerides are not stable in HDL, but are degraded by hepatic lipase so that, finally, small HDL particles are left, which restart the uptake of cholesterol from cells. The cholesterol delivered to the liver is excreted into the bile and, hence, intestine either directly or indirectly after conversion into bile acids. Biochemistry Of Lipids Lipoproteins And Membranes Pdf Creator' title='Biochemistry Of Lipids Lipoproteins And Membranes Pdf Creator' />Delivery of HDL cholesterol to adrenals, ovaries, and testes is important for the synthesis of steroid hormones. Several steps in the metabolism of HDL can participate in the transport of cholesterol from lipid laden macrophages of atheroscleroticarteries, termed foam cells, to the liver for secretion into the bile. This pathway has been termed reverse cholesterol transport and is considered as the classical protective function of HDL toward atherosclerosis. However, HDL carries many lipid and protein species, several of which have very low concentrations but are biologically very active. For example, HDL and its protein and lipid constituents help to inhibit oxidation, inflammation, activation of the endothelium, coagulation, and platelet aggregation. All these properties may contribute to the ability of HDL to protect from atherosclerosis, and it is not yet known which are the most important. The Medical Biochemistry Page is a portal for the understanding of biochemical, metabolic, and physiological processes with an emphasis on medical relevance. Issuu is a digital publishing platform that makes it simple to publish magazines, catalogs, newspapers, books, and more online. Easily share your publications and get. In addition, a small subfraction of HDL lends protection against the protozoan parasite Trypanosoma brucei brucei. This HDL subfraction, termed trypanosome lytic factor TLF, contains specialized proteins that, while very active, are unique to the TLF molecule. In the stress response, serum amyloid A, which is one of the acute phase proteins and an apolipoprotein, is under the stimulation of cytokines interleukin 1, interleukin 6, and cortisol produced in the adrenal cortex and carried to the damaged tissue incorporated into HDL particles. At the inflammation site, it attracts and activates leukocytes. In chronic inflammations, its deposition in the tissues manifests itself as amyloidosis. Biochemistry Of Lipids Lipoproteins And Membranes Pdf Free' title='Biochemistry Of Lipids Lipoproteins And Membranes Pdf Free' />Lipid decomposition studies in frozen fish have led to the development of a simple and rapid method for the extraction and purification of lipids from biological. Chronic infections appear to be common features of various diseases, including neurodegenerative, psychiatric and neurobehavioral diseases, autoimmune diseases. Amino acids are molecules containing an amine groupNH 2, a carboxylic acid groupRCOOH and a sidechain usually denoted as R that varies between different. Categories of Lipids Fatty acids. Fatty acids, or fatty acid residues when they are part of a lipid, are a diverse group of molecules synthesized by chainelongation. It has been postulated that the concentration of large HDL particles more accurately reflects protective action, as opposed to the concentration of total HDL particles. This ratio of large HDL to total HDL particles varies widely and is measured only by more sophisticated lipoprotein assays using either electrophoresis the original method developed in the 1. NMR spectroscopy methods See also nuclear magnetic resonance and spectroscopy, developed in the 1. SubfractionseditFive subfractions of HDL have been identified. Biochemistry Of Lipids Lipoproteins And Membranes Pdf EditorIndustrial Trans Fatty Acid and Serum Cholesterol The Allowable Dietary Level. Department of Food and Nutrition, Toyama College, 4. Mizuguchi, Gankai ji, Toyama 9. Japan. 2Kyushu University, 5 3. Najima, Higashi ku, Fukuoka 8. Phospholipid.jpg' alt='Biochemistry Of Lipids Lipoproteins And Membranes Pdf' title='Biochemistry Of Lipids Lipoproteins And Membranes Pdf' />Japan. Received 7 April 2. Revised 1. 2 June 2. Accepted 2. 5 July 2. Published 3. 0 August 2. Academic Editor Kamal A. Disk Drill Pro Activation Code. Amin. Copyright 2. Hiroyuki Takeuchi and Michihiro Sugano. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Trans fatty acid TFA from partially hydrogenated oil is regarded as the worst dietary fatty acid per gram due to its role in coronary heart disease. TFA consumption is decreasing worldwide, but some but not all observational studies indicate that TFA intake has little relevance to serum cholesterol levels in populations with low TFA intake lt 1 E percentage of total energy intake, lt approximately 2 gday. Few intervention trials examined the effect of TFAs on blood cholesterol at relatively low levels lt 2 E no definite evidence is available on the tolerable upper level of the intake. A series of our intervention studies in Japanese suggested that an industrial TFA intake at lt 1 E does not influence the serum cholesterol level. To establish allowable level, we must consider not only the dietary level of TFAs, but also the composition of dietary fats simultaneously consumed, that is, saturated and unsaturated fatty acids. These fatty acids strengthen or counteract the adverse effect of TFAs on serum cholesterol levels. In this review we describe the complex situation of the cardiovascular effects of industrial TFAs. The relationship between dietary industrial TFAs and concentration of plasma cholesterol should be evaluated from the viewpoint of dietary patterns rather than TFAs alone. Trans Fatty Acid in Foods. Trans fatty acid TFA is defined as unsaturated fatty acid with at least one nonconjugated double bond in the trans configuration. There are several food sources of TFAs. TFA from partially hydrogenated vegetable oil is the major source of dietary industrial TFAs 1, and this type of TFA is regarded as contributing to cardiovascular events. There is a trend toward decreasing consumption of this type of TFA. The second major source of TFA is from ruminant fat, and in some cases ruminant fat is a major contributor of TFAs due to the reduction of the intake of industrial TFAs. The impact of ruminant fat TFAs on human health has not been conclusive, regarding both health benefits 2 and harmful effects 3 depending on the reports. A small amount of industrial TFA is also present in edible oils formed during the deodorization process at high temperature 4. The physiological effects of TFA contained in edible oils are not well established 5, 6. Since the TFA in partially hydrogenated oils PHOs is composed mainly of a number of positional isomers of the octadecenoic acids, it is important to clarify which TFA isomers is responsible for health hazards. Chatgilialoglu et al. Ferreri et al. 8 also summarized the significant role of isomerism of fatty acids in membrane functions. In most of the in vitro studies available, elaidic acid 9t 1. TFA in PHO 9. Elaidic acid is the major component of TFA in PHO, but in many cases it is not always the largest part, usually lt 3. TFAs. It is plausible that different isomers exert different biological functions, if any. When the principal TFAs is revealed, more effective ways to lower the TFA contents of foods can be expected, contributing to human health. TFA in humans is attributed not only to dietary origin but also to that endogenously formed through the production of free radicals during metabolism 7. However, it is likely that most of the TFAs in humans are attributable to dietary origin, although the biological activities may differ between these two sources of TFAs. Endogenously formed TFAs were detected in breast cancer tissue specimens 1. There are several reports concerning the industrial and ruminant TFA content of the foods consumed in various countries 1. Craig Schmidt and Rong summarized the worldwide consumption of TFAs 1. In general, the TFA contents of Japanese foods are comparable to those of the corresponding foods in the countries. The amounts of TFA consumed differ among countries, and Japan is probably one of the countries that consumes the least TFA. An example of the industrial and ruminant TFA contents of foods marketed in Japan is shown in Table 1 1. The contents of TFA in currently available foods containing partially hydrogenated oils may be somewhat lower than the values shown in this Table, reflecting manufacturers efforts to reduce TFA contents after the information in the Table was published. However, it should be noted that the industrial TFA content differs widely even in the same foods. Nevertheless, TFA intakes from various foods among Japanese are relatively lower than those in the US and EU, as shown in Table 2 1. In the national data, the average intakes of industrial TFA and ruminant TFA in Japanese were estimated to be 0. E and 0. 2. 62 gday 0. E, and the 9. 9th percentiles of these values were 1. E and 1. 4. 65 gday 0. E 2. 0. Table 1 The trans fatty acid contents of major foods distributed in Japan. Table 2 The trans fatty acid TFA intake from various foods in Japanese. The measurement of the TFA contents in erythrocytes or plasma should be useful to understand the dietary intake of TFA for estimating the allowable dietary level of TFA as a biomarker 2. Although the industrial TFA content of vegetable cooking oils without partial hydrogenation is relatively low, vegetable oils are the highest source of dietary TFA among other foods, followed by milk. It is therefore important to determine how much TFAs people in Japan are consuming from each type of food, rather than only the TFA content of the food. The US Food and Drug Administration FDA issued a ban in 2. June 2. 01. 8 regarding the use of partially hydrogenated oils 2. TFA intake in the US. However, it is impossible to construct healthy diets that are completely free from TFAs, as milk and meat contain TFAs. In light of this situation, it is important to precisely identify the effects of low levels of TFA intake on serum cholesterol levels. Trans Fatty Acid and Serum Cholesterol. In 1. 99. 0, Mensink and Katan 2. TFAs equivalent to 1. E percentage of total energy intake increased the serum LDL cholesterol and decreased HDL cholesterol concentrations in healthy subjects. Thereafter, a number of intervention studies have been conducted, and they revealed that a TFA intake above 46 E resulted in elevated serum LDL cholesterol concentrations 2. Several epidemiological studies provided evidence that the consumption of excess TFAs from industrial sources increases the risk of cardiovascular disease CVD 2. Though the influence of excessive industrial TFA intake on both blood lipid levels and the risk of cardiovascular disease has been well established 2. TFA intake does not exist 2. In the human body, TFAs are metabolized in the same way that cis fatty acids are metabolized 3. TFAs appear to affect serum cholesterol levels through multiple mechanisms including the hepatic production, secretion, and catabolism of circulating lipoproteins 3.