Good lipoproteins

The HDL (friendly or good lipoproteins) has a higher percentage of protein and fewer lipids. HDL removes cholesterol from the bloodstream and delivers cholesterol to the liver. The other three lipoproteins are composed of cholesterol... 

Lipoproteins that transport cholesterol from the liver to tissues throughout the body (the "bad" lipoproteins) High-density lipoproteins (HDLs) Lipoproteins that transport cholesterol from body tissues to liver (the "good" lipoproteins)... 

HDL is another one of the major lipoproteins in circulation known as the good lipoprotein due to the fact that HDL transports cholesterol and fat molecules from peripheral tissues and arterial walls to the liver for excretion. Enhanced plasma HDL-cholesterol concentration lowers the risk of cardiovascular-associated diseases [41] providing healthy endothelial cell function (vasodilation) [42]. HDL enhances the activity of endothelial NOS to induce femoral arterial vasodilation in vitro [43] and enhances myocardial perfusion via NO-dependent mechanisms in vivo [44]. Altogether, these data suggest that HDL may reduce the prevalence and may serve as a novel biometric for cardiovascular disease. 

Cholesterol is removed from peripheral tissues by high density lipoproteins (HDLs) (Chapter 41) which are frequently praised as being good lipoproteins . 

HDL are the good lipoproteins that dispose of exoess cholesterol... 

Cholesterol is biosynthesized in the liver trans ported throughout the body to be used in a va riety of ways and returned to the liver where it serves as the biosynthetic precursor to other steroids But cholesterol is a lipid and isn t soluble in water How can it move through the blood if it doesn t dis solve in if The answer is that it doesn t dissolve but IS instead carried through the blood and tissues as part of a lipoprotein (lipid + protein = lipoprotein) The proteins that carry cholesterol from the liver are called low density lipoproteins or LDLs those that return it to the liver are the high-density lipoproteins or HDLs If too much cholesterol is being transported by LDL or too little by HDL the extra cholesterol builds up on the walls of the arteries caus mg atherosclerosis A thorough physical examination nowadays measures not only total cholesterol con centration but also the distribution between LDL and HDL cholesterol An elevated level of LDL cholesterol IS a risk factor for heart disease LDL cholesterol is bad cholesterol HDLs on the other hand remove excess cholesterol and are protective HDL cholesterol IS good cholesterol... 

Heterogeneous reaction (Section 6 1) A reaction involving two or more substances present in different phases Hydro genation of alkenes is a heterogeneous reaction that takes place on the surface of an insoluble metal catalyst Heterolytic cleavage (Section 4 16) Dissociation of a two electron covalent bond in such a way that both electrons are retained by one of the initially bonded atoms Hexose (Section 25 4) A carbohydrate with six carbon atoms High density lipoprotein (HDL) (Section 26 11) A protein that carries cholesterol from the tissues to the liver where it is metabolized HDL is often called good cholesterol Histones (Section 28 9) Proteins that are associated with DNA in nucleosomes... 

High-density lipoprotein (HDL) (Section 26.11) Aprotein that carries cholesterol from the tissues to the liver where it is metabolized. HDL is often called good cholesterol. ... 

Krieger, M, 1999. Charting the fate of the good cholesterol Identification and characterization of the high-density lipoprotein receptor SR-BI. Annu Rev Biochem 68, 523-558. 

Further research on serum cholesterol revealed that is exists in two forms, high and low density lipoprotein. The high density lipoprotein appears to consist of cholesterol that is being moved to the liver for metabolism while low density lipoprotein appears to be cholesterol that is likely to block arteries. This has led to the labelling of high density lipoprotein as good cholesterol and of low density lipoprotein as bad cholesterol. 

The recent years have seen the success of statins like Lipitor (atorvastatin) as hypolipidemic agents that help treating cardiovascular disease primarily by lowering low-density lipoproteins ( bad cholesterol ) levels. Another novel strategy is to tackle the same problem by elevating high-density lipoproteins (H D L or good cholesterol ) levels via inhibition of cholesteryl ester transfer protein (CETP). 

A competitive ELISA assay for Lp(a) was recently described (Y4) in which the microtiter plate was coated with Lp(a) purified from a pool of donors. The method is simple and easy to perform, with satisfactory analytical parameters. A good stability and a reproducible coating of plates with the large Lp(a) lipoprotein is, however, critical in this type of assay. Wang et al. (W6) described an indirect sandwich assay for the measurement of Lp(a) in plasma and in dried blood spots, which can be applied to screening elevated Lp(a) levels in newborns (V3, V4). 

Cholesterol is carried in the bloodstream by hpoproteins such as low density lipoprotein (LDL, or bad cholesterol ) and high density lipoprotein (HDL, good cholesterol ). LDL carries cholesterol from the liver to other parts of the body. LDL attaches to receptors (see Chapter 2) on the cell surface and is taken into the cell interior. It is then degraded and the cholesterol is used as a component for the cell membrane. When there is excessive cholesterol inside the cell, it leads to a reduction in the synthesis of LDL receptors. 

Most of the mention of cholesterol in the popular press positions this molecule as a threat to human health. Many foods are proudly labeled cholesterol-free. People are properly warned to pay attention to their plasma cholesterol level, particnlarly that carried in the low-density lipoproteins, LDLs, commonly known, with pretty good reason, as bad cholesterol. LDLs are lipoprotein particles containing a large protein known as B-100 associated with cholesterol, cholesteryl esters, phospholipids, and some triglycerides. 

HDL (high-density lipoprotein) a protein-lipid complex that carries cholesterol away from the tissues good cholesterol. ... 

Lipid metabolism in the liver is closely linked to the carbohydrate and amino acid metabolism. When there is a good supply of nutrients in the resorptive (wellfed) state (see p. 308), the liver converts glucose via acetyl CoA into fatty acids. The liver can also take up fatty acids from chylomicrons, which are supplied by the intestine, or from fatty acid-albumin complexes (see p. 162). Fatty acids from both sources are converted into fats and phospholipids. Together with apoproteins, they are packed into very-low-density lipoproteins (VLDLs see p.278) and then released into the blood by exocytosis. The VLDLs supply extrahepatic tissue, particularly adipose tissue and muscle. 

Hyperlipidemia is a condition characterized by the presence of elevated lipoprotein levels in the blood. The term hyperlipidemia encompasses a number of different conditions, but it most often refers to high levels of cholesterol in the form of low-density lipoprotein (LDL). LDL cholesterol is often called bad cholesterol. High-density lipoprotein (HDL) is the good form of cholesterol. High LDL and/or low HDL levels are widely believed to be linked to increased heart disease risk. Because of the prevalence of hyperlipidemia in developed nations, antihyperlipidemic drugs are in high demand. 

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