Hyperlipidemia (High Cholesterol)
Hyperlipidemia, also known as hyperlipoproteinemia or high cholesterol, is a disorder characterized by abnormally high concentrations of lipids (fats) in the blood that are correlated with the development of atherosclerosis, the underlying cause of coronary heart disease (CHD) and stroke. Hyperlipidemia is caused by abnormal lipid and lipoprotein metabolism.
Lipids are a group of naturally occurring fatty substances that are present in the blood and tissues of the body. They include cholesterol, cholesterol esters, triglycerides, and phospholipids. Lipids are essential dietary constituents because of their important functions.
?Provide energy required by the body
?Serve as the major structural components of cell membranes
?Aid in the efficient absorption of fat-soluble vitamins
?Serve as insulating material beneath the skin and around certain organs (e.g. kidneys)
?Serve as biosynthetic precursors (e.g., Cholesterol is a precursor for adrenal and gonadal steroid hormones and hepatic bile acids.)
Since lipids are insoluble in blood (plasma), they must be transported to and from the cells by special carriers called lipoproteins. Lipoproteins are spherical particles of high molecular weight. Each lipoprotein particle contains a non-polar core and a hydrophilic surface. The hydrophilic surface makes the lipoprotein soluble in plasma and acts as an interface between the plasma and lipid core. The core consists of hydrophobic lipids, triglycerides and cholesterol esters, surrounded by a hydrophilic surface coat of phospholipids, unesterified cholesterol, and specific proteins termed apolipoproteins or apoproteins. The apolipoproteins provide structural integrity to the lipoproteins and determine the lipoproteins’ metabolic fate by serving as binding sites for receptors and activating enzymes involved in lipid metabolism.
The six major classes of plasma lipoproteins are:
?Chylomicrons: Particles of the lowest density that appear in the blood shortly after fat has been digested and absorbed from the small intestine. They transport dietary cholesterol and triglycerides to muscles (for energy), to fat tissue (for storage), and to breasts (for milk production).