Patients with the metabolic syndrome - gender adjusted HDL-cholesterol levels of less than 40 mg/dL in men and 50 mg/dL in women.Įxercise, weight loss (in overweight subjects), smoking cessation, and changes in diet (specifically substitution of monounsaturated for saturated fatty acids) all can raise HDL-cholesterol.
Patients considered high risk for cardiovascular disease based on HDL levels include: Low HDL-cholesterol is a component of the metabolic syndrome that is characterized by obesity, insulin resistance, dyslipidemia, and hypertension Risk for myocardial infarction increases by about 25 percent for every 5 mg/dL decrement in serum HDL-cholesterol below median values for men and women.
This effect may be mediated by reverse cholesterol transport, a process whereby excess cholesterol in cells and in atherosclerotic plaques is removed and transported back to the liver. HDL is thought to be anti-atherogenic and high HDL levels are cardioprotective. Incidence of coronary heart disease events in a normal population is inversely related to the serum HDL-cholesterol concentration - low levels carry an increased coronary risk HDL is a small particle composed of phospholipid and apolipoproteins and produced in hepatic and intestinal cells. LDL is also taken up by macrophages and other cells which can lead to excess accumulation and the formation of foam cells which are important in plaque formation.In non hepatic tissues, LDL is used in hormone production, cell membrane synthesis, or stored.In the liver, LDL is converted into bile acids and secreted into the intestines.LDL is internalized by hepatic and nonhepatic tissues.LDL particles contain a core of cholesterol esters and a smaller amount of triglyceride.VLDL remnants are cleared from the circulation or incorporated into LDL.These can be hydrolyzed by lipoprotein lipase to form IDL or VLDL remnants.VLDL is formed in the liver from triglycerides and cholesterol esters.Remnants are used in the formation of HDL.
In peripheral tissues, free fatty acids are released from the chylomicrons to be used as energy, converted to triglyceride or stored in adipose.Chylomicrons enter the circulation and travel to peripheral sites.Triglycerides and cholesterol combine to form chylomicrons.Triglycerides are formed in the intestinal cell from free fatty acids and glycerol and cholesterol is esterified.Dietary cholesterol and fatty acids are absorbed.High density lipoprotein - carry cholesterol esters.Low density lipoprotein - carry cholesterol esters.Intermediate density lipoprotein - carry cholesterol esters and triglycerides.Very low density lipoprotein - carry endogenous triglyceride and some cholesterol.Chylomicrons - large particles that carry dietary lipid.The proteins function as cofactors and ligands for receptors. Lipoprotein consists of esterified and unesterified cholesterol, triglycerides, phospholipids and apolipoproteins.
Lipids = cholesterol and triglyceride - are insoluble in plasma and are transported in lipoproteins.įunctions = energy utilization, steroid hormone production, bile acid production, lipid deposition. Cholesterol Metabolism Lipid and Lipoprotein Metabolism (Rosensen, 2009)