High- density lipoprotein - Wikipedia. High- density lipoproteins (HDL), density relative to extracellular water, 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. Her work has been. Good Cholesterol Foods to Raise HDL Levels and Lowering LDL Naturally. 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. HDL particles have long been divided into 5 subgroups, by density/size (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 fats 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 . 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. In healthy individuals, about 3. HDL. 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 . 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 mmol/L) have increased rates for heart disease. 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. 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. 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. 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). HDL 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. 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. 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. At the inflammation site, it attracts and activates leukocytes. In chronic inflammations, its deposition in the tissues manifests itself as amyloidosis. 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. From largest (and most effective in cholesterol removal) to smallest (and least effective), the types are 2a, 2b, 3a, 3b, and 3c. Triglycerides (TGs), cholesterol, and phospholipids are the major lipids in the body. They are transported as complexes of lipid and proteins known as lipoproteins. TGs (triglycerides): TGs are formed by combining glycerol with three molecules of fatty acid. TGs, as major components of VLDL and chylomicrons, play an important role in metabolism. When the body requires fatty acids as an energy source, the hormone glucagon signals the breakdown of the TGs by lipase to release free fatty acids (FFA). TGs are water- insoluble, non- polar neutral fats. These are not the structural components of biological membranes. TGs synthesis and storage mostly occurs in liver and adipose tissue. FFA and glycerol must be activated prior to the synthesis of TGs into Acyl- Co. A and glycerol- 3- phosphate respectively. Cholesterol: The name cholesterol originates from the Greek chole- (bile) and stereos (solid), and the chemical suffix- ol for an alcohol. It is an essential structural component of cell membrane, where it is required to establish proper membrane permeability and fluidity. In addition, cholesterol is an important component for the manufacture of bile acids, steroid hormones, and vitamin D. Although cholesterol is an important and necessary molecule, a high level of serum cholesterol is an indicator for diseases such as heart disease. About 2. 0- 2. 5% of total daily cholesterol production occurs in the liver. Phospholipids: Phospholipids are TGs that are covalently bonded to a phosphate group by an ester linkage. Phospholipids perform important functions including regulating membrane permeability and in maintaining electron transport chain in mitochondria. They participate in the reverse cholesterol transport and thus help in the removal of cholesterol from the body. They are involved in signal transmission across membranes and they act as detergents and help in solubilization of cholesterol. Lipoprotein: These consist of a central core of a hydrophobic lipid (including TGs and cholesteryl esters) encased in a hydrophilic coat of polar phospholipid, free cholesterol and apolipoprotein. There are six main classes of lipoprotein, differing in the relative proportion of the core lipids and in the type of apoprotein. Chylomicrons. VLDL- C particiles. IDL- C particles. LDL- C particles. HDL- C particle. Lipoprotein (a) . Men also have an increased incidence of atherosclerotic heart disease. Alcohol consumption tends to raise HDL levels. Recent studies confirm the fact that HDL has a buffering role in balancing the effects of the hypercoagulable state in type 2 diabetics and decreases the high risk of cardiovascular complications in these patients. Also, the results obtained in this study revealed that there was a significant negative correlation between HDL and activated partial thromboplastin time (APTT). Low concentrations of HDL (below 4. L for men, below 5. L for women) increase the risk for atherosclerotic diseases. Data from the landmark Framingham Heart Study showed that, for a given level of LDL, the risk of heart disease increases 1. HDL varies from high to low. On the converse, however, for a fixed level of HDL, the risk increases 3- fold as LDL varies from low to high. The reference method still uses a combination of these techniques. Larger HDL particles are carrying more cholesterol. NMR measurements. Multiple additional measures, including LDL particle concentrations, small LDL particle concentrations, VLDL concentrations, estimations of insulin resistance and standard cholesterol lipid measurements (for comparison of the plasma data with the estimation methods discussed above) are routinely provided in clinical testing. Fasting serum lipids have been associated with short term verbal memory. In a large sample of middle aged adults, low HDL cholesterol was associated with poor memory and decreasing levels over a five- year follow- up period were associated with decline in memory. Fibrates have not been proven to have an effect on overall deaths from all causes, despite their effects on lipids. A 2. 01. 1 niacin study was halted early because patients adding niacin to their statin treatment showed no increase in heart health, but did experience an increase in the risk of stroke. As statins are associated with side effects like myopathy which causes sore muscles, patients who experience these side effects may need to be given a lower dose of statin to control cholesterol. American Heart Association. July 2. 00. 9. Retrieved 8 October 2. Circulation. 1. 11 (5): e. PMID 1. 56. 99. 26. European Heart Journal Supplements. National Institute of Health. National Heart, Lung, and Blood Institute (NHLBI). Retrieved 2 June 2. High- Sugar Diet Linked to Cholesterol. April 2. 0, 2. 01. The average American eats the equivalent of about 2. Excess sugar is known to contribute to obesity, diabetes, and other conditions linked to heart disease, and now new research links it to unhealthy cholesterol and triglyceride levels. People in the study who ate the most added sugar had the lowest HDL, or good cholesterol, and the highest bloodtriglyceride levels. People who ate the least sugar had the highest HDL and the lowest triglyceride levels. Eating large amounts of added sugar more than tripled the risk of having low HDL, which is a major risk factor for heart disease. The study appears in this week’s issue of the Journal of the American Medical Association. Added Sugar, Empty Calories. Added sugar is defined as any caloric sweetener used in processed or prepared foods. Beyond increasing calories, added sugars have no nutritional value. In guidelines released late last summer, the American Heart Association recommended limiting added sugar in the diet to no more than 1. That’s about 6 teaspoons of sugar a day for women and 9 teaspoons for men. To put this in perspective, the average 1. A breakfast cereal with 1. In the newly published study, daily consumption of added sugars averaged about 3. That is an increase of about 6% in just over three decades, researcher Miriam Vos, MD, of Atlanta’s Emory University tells Web. MD.“This is a dramatic increase, but it is not too surprising given the proliferation of processed foods with large amounts of added sugar,” she says. Vos and colleagues analyzed data on 6,1. National Health and Nutrition Examination Survey (NHANES) from 1. Continued. The lowest consumption group got less than 5% of their daily calories from added sugars, while the highest consumers got 2. Sugar consumption appeared to be directly related to HDL and triglyceride levels. The more sugar the participants ate, the lower their HDL and higher their triglycerides. Compared to people who ate the least sugar, people who ate the most sugar were three times more likely to have low HDL levels.“Our findings strongly support the AHA recommendations to limit added sugar,” Vos says. Sugar Hiding in Drinks, Processed Foods. University of Vermont nutrition professor Rachel K. Johnson, Ph. D, the author of the AHA sugar guidelines, says only a small minority of Americans meet the goal of eating no more than 1. Reading food labels can help, but because labels don’t distinguish between added sugars and those that occur naturally in foods like fruits, vegetables, and dairy products, they can be misleading, she says.“When a label has the word . Another ingredient that represents added sugar is “evaporated cane juice.”Johnson says anyone who wants to limit the sugar in their diet should start by examining what they drink.“We know that beverages are the No. Journal of the American Medical Association, April 2. Miriam B. Vos, MD, MSPH, assistant professor of pediatrics, Emory. University, Atlanta. Rachel K. Johnson, Ph. D, MPH, RD, associate professor of nutrition. University of Vermont at Burlington; spokeswoman, American Heart. Association. News release, Journal of the American Medical Association. All rights reserved.
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