High Density Lipoprotein cholesterol

Cholesterol is found in all cells. It is needed for many body functions. Two types of cholesterol are HDL and LDL. HDL is a “good” cholesterol that removes LDL (bad) cholesterol from the bloodstream.

High-density lipoprotein (HDL) is one of the five major fat and protein particles (lipoproteins) whose role it is to enable blood fats (lipids), such as cholesterol and triglycerides, to be transported within the water-based bloodstream.

HDL is a class of heterogeneous lipoproteins containing approximately equal amounts of lipid and protein. HDL particles are characterized by high density (more 1.063 g/mL) and small size (Stoke’s diameter 5 to 17 nm).

The various HDL subclasses vary in quantitative and qualitative content of lipids, apolipoproteins, enzymes, and lipid transfer proteins, resulting in differences in shape, density, size, charge, and antigenicity.

In a normal healthy individual, HDL carries about a quarter of the total amount of cholesterol in the blood, whereas most of the remainder is carried in LDL (low density lipoprotein) “bad cholesterol” particles.

HDL is important for the synthesis of steroid hormones but it is better known for its protective role against cardiovascular disease. A low HDL is thought to speed up the rate at which arteries fur up.

HDL (good) cholesterol protects against heart disease, so for HDL, higher numbers are better. A level less than 40 mg/dL is low and is considered a major risk factor because it increases the risk for developing heart disease. HDL levels of 60 mg/dL or more help to lower the risk for heart disease.

A variety of things can affect cholesterol levels: Diet, Weight, Physical Activity. Low HDL among others due to: Insulin resistance, Familial Combined Hyperlipidaemia (FCH), Tangier disease, Medicines including beta blockers, thiazide diuretics, androgens, progestogens and anabolic steroids.
High Density Lipoprotein cholesterol 

High density lipoprotein

Lipoproteins are globular particles of varying size and composition, configured so that their outer surface is hydrophilic and their inner core, which contains immiscible lipids, hydrophobic.

High density lipoproteins (HDL) are the smallest and the densest of all plasma lipoproteins.

Protein forms the major building blocks of HDL. HDL carries a particular large number of proteins as compared to other lipoprotein species.

HDLs are composed of lipids (– including phospholipid, cholesterol and triglyceride) and apolipoproteins. The core consists of cholesterol ester and triglycerides.

The major structural apolipoproteins of HDL is apolipoproteins A-1 (apoA-I) and the majority of HDLs contain apoA-I.

HDL plays an important role in transporting cholesterol from peripheral tissues directly back to the liver or indirectly via intermediate density lipoprotein (IDL) and low density lipoprotein, in a process popularly referred to as reverse cholesterol transport pathway.

HDL display antithrombotic and anti-inflammatory properties and have been shown to inhibit the activation and binding of monocytes to the endothelium.
High density lipoprotein