Multiple lines of evidence show that high-density lipoproteins (HDL) protect against coronary heart disease (CHD), and that low blood levels of HDL cholesterol (HDLc) indicate high risk of a coronary event. Major epidemiological studies show that a low HDLc is a strong predictor of CHD, and this relationship occurs at any level of low-density lipoprotein cholesterol (LDLc) or triglycerides, demonstrating independence. When the HDLc level is raised by drug therapy, coronary atherosclerosis is decreased and CHD events are lessened. Increases in HDLc are in fact independently correlated with coronary angiographic and clinical benefit. HDL stimulates the removal of cholesterol from cells in the vascular wall. The cholesterol is taken up by HDL and shuttled in part to the liver for excretion in the bile.
Experiments in transgenic mice provide proof that increased HDL secretion protects against atherosclerosis caused by an atherogenic diet or genetic hyperlipidaemia. In humans, HDL has direct beneficial effects on coronary arterial vasodilation. This compelling scientific evidence thus justifies HDLc as a target to reduce risk of CHD. An international group of experts in epidemiology, clinical and basic science formed a consensus that an HDLc concentration of 1.0 mmol/L (40 mg/dL) is a realistic clinical guideline for patients at high risk of a coronary event. Specific diet and drug therapies were recommended.
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