Intermediate density lipoprotein

Intermediate Density Lipoprotein
Synonyms	N/A
Pronounce	N/A
Specialty	N/A
Symptoms
Complications	Atherosclerosis, Cardiovascular disease
Onset
Duration
Types	N/A
Causes
Risks	Hyperlipidemia, Genetic predisposition
Diagnosis	Lipid profile
Differential diagnosis	N/A
Prevention	N/A
Treatment	Lifestyle modification, Statins, Fibrates
Medication	N/A
Prognosis
Frequency
Deaths	N/A

Intermediate Density Lipoprotein (IDL) is a class of lipoprotein that is formed during the metabolism of very low-density lipoproteins (VLDL) and is a precursor to low-density lipoproteins (LDL). IDLs are part of the body's mechanism for transporting lipids, such as cholesterol and triglycerides, through the bloodstream.

Structure and Composition

IDLs are composed of a core of triglycerides and cholesteryl esters, surrounded by a shell of phospholipids, free cholesterol, and apolipoproteins. The primary apolipoproteins associated with IDL are Apolipoprotein B-100 and Apolipoprotein E.

Apolipoproteins

• Apolipoprotein B-100 (ApoB-100) is essential for the structural integrity of IDL and serves as a ligand for LDL receptors.
• Apolipoprotein E (ApoE) plays a crucial role in the hepatic uptake of IDL by binding to specific receptors on hepatocytes.

Metabolism

IDLs are formed from the catabolism of VLDLs. As VLDLs circulate in the bloodstream, they lose triglycerides through the action of lipoprotein lipase, becoming IDLs. IDLs can be further metabolized into LDLs or taken up by the liver through receptor-mediated endocytosis.

Conversion to LDL

The conversion of IDL to LDL involves the further removal of triglycerides, primarily through the action of hepatic lipase. This process results in a denser particle with a higher proportion of cholesterol, characteristic of LDL.

Hepatic Uptake

IDLs can be cleared from the circulation by the liver. This process is mediated by the binding of ApoE to hepatic receptors, such as the LDL receptor and the LDL receptor-related protein (LRP).

Clinical Significance

Elevated levels of IDL are associated with an increased risk of atherosclerosis and cardiovascular disease. IDL particles can penetrate the endothelium of blood vessels and contribute to the formation of atherosclerotic plaques.

Risk Factors

• Hyperlipidemia
• Diabetes mellitus
• Obesity
• Genetic disorders such as familial dysbetalipoproteinemia

Diagnosis

IDL levels are typically assessed as part of a lipid profile, which measures total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides. Advanced lipid testing may directly measure IDL levels.

Management

Management of elevated IDL levels involves lifestyle modifications and pharmacological interventions.

Lifestyle Modifications

• Dietary changes: Reducing intake of saturated fats and cholesterol
• Physical activity: Regular exercise to improve lipid metabolism
• Weight management: Achieving and maintaining a healthy weight

Pharmacological Treatment

• Statins: Lower cholesterol levels by inhibiting HMG-CoA reductase
• Fibrates: Primarily reduce triglyceride levels
• Niacin: Can lower LDL and raise HDL levels

See Also

• Lipoprotein
• Cholesterol
• Atherosclerosis
• Cardiovascular disease

External Links

• MedlinePlus: Lipoprotein
• American Heart Association: About Cholesterol