Lipoprotein – Part 3 – Very Low Density Lipoprotein (VLDL)
- The best sample is serum after 10 to 12 hours of fast.
- Plasma can also be used.
- The preservative is stable for one week at 4 °C.
Purpose of the test (Indications)
- These are estimated to predict heart disease.
- Lipoprotein may be part of the lipid profile.
- These are done regularly to monitor the disease.
- Keep in mind that smoking and alcohol decrease HDL values.
- After myocardial infarction, the cholesterol level may be decreased.
- HDL values are age and sex depends.
- Drugs that may affect (increase) the lipoproteins are Aspirin, Phenothiazines, Sulfonamides, oral contraceptives, and steroids.
- HDL is raised in Hypothyroidism and decreased in Hypothyroidism.
What are the lipoproteins:
- Lipoproteins consist of :
- High-density lipoprotein (HDL).
- Low-density lipoprotein (LDL).
- Very low-density lipoprotein (VLDL).
Very low-density lipoprotein (VLDL)
- VLDL carries a very small amount of cholesterol.
- The outer covering lipoproteins are called Apoprotein and these are classified into:
- Apo- B.
- Apolipoproteins are a hydrophilic component of the lipoproteins.
- While lipids like cholesterol and triglycerides are hydrophobic and need to be placed in water-soluble micellar structures (Apolipoproteins) in order to be transported in the plasma.
- Apo-C, B-100, and E become the main components.
- VLDL is the product of endogenous lipoprotein synthesis in the liver and delivered to the tissue.
- VLDL proteins are the main carrier of triglycerides which is synthesized in the liver.
- Triglycerides are derived from dietary precursors, such as free fatty acids, glycerol, and carbohydrates.
- Triglycerides are a predominant component.
- VLDL contains about 10% cholesterol and functionally important apolipoproteins.
- VLDL may be expressed as the percentage of cholesterol.
- The Apo – C activates the release of lipoprotein lipase enzyme, which hydrolyzes triglyceride into glycerol, monoglycerol, and free fatty acids.
- This reaction may give rise to intermediate lipoproteins (IDL).
- VLDL consists of :
- Triglycerides 40 to 60%
- Cholesterol 5 to 8%
- Cholesterol ester 11 to 14%
- Phospholipids 20 to 23%
- Protein 4 to 11%
- VLDL is associated with the risk of coronary heart disease.
- VLDL can convert to LDL.
- VLDL more than 25 to 50 % are associated with increased coronary heart disease.
- 7 to 32 mg/dL.
|Borderline to high risk||140 to 159|
|Children and adolescents|
|Borderline – high risk||110 to 129|
Increased VLDL is seen in:
- Nephrotic syndrome.
- Glycogen storage diseases.
- Familial LDL lipoproteinemia.
- Chronic liver disease.
- Liver cell carcinoma.
- Cushing syndrome.
- Familial hypercholesterolemia.
Decreased VLDL is seen in:
- Familial hypolipoproteinemia.
Table showing the summary of characteristics of the lipoproteins
|PLasma appearance||Creamy layer, slightly turbid||Clear||Clear, or yellow-orange tint||Turbid to opaque|
|Size (diameter nm)||>70.0||4 to 10||19.6 to 22.7||25 to 70|
|Electrophoretic mobility||Origin||α – region||β – region||Pre – β region|
|Molecular weight||0.4 to 30 x 109||3.6 x 109||2.75 x 109||5 to 10 x 109|
|Synthesized in (Tissue of origin)||Intestine||Intestine and liver||Intravascular||Liver and intestine|
|Composition by weight in %|
|Cholesterol esterified||5||38||49||11 to 14|
|Cholesterol unesterified||2||10||13||5 to 8|
|Triglycerides||84||9||11||44 to 60|
|Phospholipids||7||22||27||20 to 23|
|Proteins||2||21||23||4 to 11|
|Triglycerides||Markedly raised||Normal||Normal/ Raised||Moderately to Markedly raised|
|Clinical significance of||Pancreatitis and acute abdomen||Decreased risk of CAD||Increased risk of CAD||Increased risk of CAD|
|Functions||Transport dietary lipids to tissue||Carry cholesterol from tissue to liver||Carries cholesterol to tissue||Transport endogenous TG from liver to adipose tissue|
Note: Lipoproteins are described in detail in LDL, HDL.