(lĭp″ō-pŏl″ē-sāk′ă-rīd) The linkage of molecules of lipids with polysaccharides.
(lip″ō-prō′tēn″, prōt′ē-ĭn) [lipo- + protein] Any of the conjugated chemicals in the bloodstream consisting of simple proteins bound to fat. Cholesterol, phospholipids, and triglycerides are all fatty components of lipoproteins. Analyzing the concentrations and proportions of lipoproteins in the blood can provide important information about patients’ risks of atherosclerosis, coronary artery disease, and death.
Lipoproteins are classified as very low-density (VLDL), low-density (LDL), intermediate-density (IDL), and high-density (HDL). Increased levels of LDL and total cholesterol directly raise one’s chances of having coronary heart disease (CHD). For this reason LDL has been referred to colloquially as “bad” cholesterol. By contrast, increased levels of HDL (“good” cholesterol) are linked with a lowered risk of CHD. The National Cholesterol Education Program has designated 70–100 mg/dl or less as a desirable level of LDL in those already affected by CHD; for people without CHD, a desirable level of LDL is 100 mg/dl or less. The National Heart, Lung and Blood Institute, relying on decades of data from the Framingham Heart Study, uses data on lipoprotein levels in its cardiovascular “risk assessment tool” to help guide patients who need it to treatment with lipid-lowering drugs. See: http://cvdrisk.nhlbi.nih.gov SEE: atherosclerosis; coronary artery disease; hyperlipoproteinemia; statin; cholesterol for table.
ETIOLOGY: Elevated levels of lipoproteins usually are the result of a diet too rich in fats, saturated fats, and cholesterols. Genetic disease also plays a part in some patients with extremely high lipoprotein levels.
SYMPTOMS: High lipoprotein levels may cause no symptoms until patients develop arterial blockages. If arteries become blocked by lipoproteins, ischemic symptoms may develop.
TREATMENT: Abnormal lipoprotein levels become normal in many patients who consume less dietary fat and increase their exercise. When lipoproteins do not reach expected levels despite diet and exercise, medications to improve lipoprotein profiles are prescribed. These medications include statins, cholesterol-absorption inhibitors, and bile-acid binding resins.
l. (a) ABBR: Lp(a). A lipid-protein complex found normally in the plasma in small amounts in all people, but in very high concentrations in some people with familial atherosclerosis. It consists of a low-density lipoprotein molecule bound to apolipoprotein A.
high-density l. ABBR: HDL. Plasma lipids bound to albumin, consisting of lipoproteins. They contain more protein than either very low-density lipoproteins or low-density lipoproteins. High-density lipoprotein cholesterol is the so-called good cholesterol; a high level is desirable. SYN: alpha l.
intermediate-density l. ABBR: IDL. Plasma lipids bound to albumin, consisting of lipoproteins with less protein than high-density, but more than low-density lipoproteins.
l. lipase ABBR: Lp(a). An enzyme produced by many cells. On the surface of cells lining the vasculature, Lp(a) hydrolyzes fat (chylomicrons) ...