Lipids and Lipoproteins

Triglyceride

It serves as the main storage form of energy, insulator, shock absorber, and integrral part of the cell membrane.

Cholesterol

Serves as the parent chain for cholesterol-based hormones such as aldosterone, cortisol, and the sex hormones

70%

Cholesterol esters make up approximately ____ of total cholesterol

30%

Free cholesterol makes up approximately ____ of total cholesterol

Apolipoproteins

They maintain the structural integrity of lipoproteins

Lipid content

The size of a lipoprotein particle correlates with:

VLDL

A plasma sample that remains turbid after standing overnight contains excessive amounts of:

Chylomicron

A plasma sample remained turbid after standing overnight. It also had a floating “cream” layer. The “cream” layer suggests the presence of which lipoprotein?

Beta-VLDL

Floating Beta-lipoprotein that is increased in familial dysbetalipoproteinema

Lp(a)

• Sinking pre-beta lipoprotein

• Increased risk of premature coronary heart disease and stroke

• “LDL-like” particle

Lp(x)

Abnormal lipoprotein seen in patients with biliary cirrhosis or cholestasis and in patients with mutations in cholesterol acyltransferase (LCAT)

• Total cholesterol (TC)

• HDL-C

Which analytes can be measured non-fasting?

Plasma

Type of sample preferred in electrophoresis and ultracentrifugation

4.6 mmol/L (400 mg/dL)

Lipemic samples are seen when triglyceride levels exceed:

Abell-Kendall method

It is a method of cholesterol measurement which involves the initial extraction of zeolite to remove sterols.

GC-MS method

• It is the new reference method for triglyceride measurements.

• It involves the hydrolysis of fatty acids on triglycerides and the measurement of glycerol

Tangier Disease

It is an extreme form of hypoalphalipoproteinemia that is associated with increased risk of premature CHD

HDL

Apo A-1 is found on:

LDL, VLDL

Apo B-100 is found on:

Chylos

Apo B-48 is found on:

HDL, VLDL

Apo E is found on:

Transports exogenous or dietary triglycerides to peripheral tissues

What is the function of chylomicrons?

Transports endogenous / hepatic triglycerides

What is the function of VLDL?

Transports cholesterol to peripheral tissues

What is the function of LDL?

LDL

This lipoprotein can cross blood vessel walls and cause deposition of lipids

• It has the HIGHEST cholesterol content

Ultracentrifugation

It is the reference method for lipoproteins