Lipoprotein:- Part 3 – Very Low-Density Lipoprotein (VLDL)
Very Low-Density Lipoprotein (VLDL)
Sample for Very Low-Density Lipoprotein (VLDL)
- The best sample is serum after 10 to 12 hours of fasting.
- Plasma can also be used.
- The preservative is stable for one week at 4 °C.
Purpose of the test (Indications) for Very Low-Density Lipoprotein (VLDL)
- These are estimated to predict heart disease.
- Lipoprotein may be part of the lipid profile.
- These are done regularly to monitor the disease.
Precautions for Very Low-Density Lipoprotein (VLDL)
- 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 depending.
- 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 lipoproteins:
- Lipoproteins consist of the following:
- High-density lipoprotein (HDL).
- Low-density lipoprotein (LDL).
- Very low-density lipoprotein (VLDL).
- The outer covering lipoproteins are called Apoproteins, and these are classified into:
- Apo- B.
- Apolipoproteins are a hydrophilic component of 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.
Very low-density lipoprotein (VLDL)
- It originates from the liver and carries triglycerides from the liver to other tissues.
- VLDL carries a very small amount of cholesterol.
- It is the product of endogenous lipoprotein synthesis in the liver and is delivered to the tissue.
- VLDL proteins are the main carrier of triglycerides which are 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 the following:
- Triglycerides = 40% to 60%
- Cholesterol = 5% to 8%
- Cholesterol ester = 11% to 14%
- Phospholipids = 20% to 23%
- Protein = 4% to 11%
- Another source:
- Triglycerides = 60%
- Cholesterol = 15%
- Phospholipids = 15%
- Protein 10%
Composition of the Very Low-Density Lipoprotein (VLDL):
- It is a pre-β-lipoprotein derived from the liver.
|Type of lipid||Source||Diameter (nm)||Ultracentrifuge||% Protein||% Total lipids||Free cholesterol|
|Very low-density lipoprotein (VLDL)||
Difference between VLDL and LDL:
- LDL has lower contents of triglycerides and higher cholesterol contents.
- LDL carries 70% of the total cholesterol and very little amount of triglycerides.
- LDL has no apoproteins C or E.
- Inside the cells, the LDL molecule is metabolized into its component parts.
- It shows that LDL has a major role in providing cholesterol to the body cells and leads to atherosclerosis.
- VLDL has the majority of triglycerides and less cholesterol content.
Draw-backs of Very Low-Density Lipoprotein (VLDL):
- VLDL is associated with an increased risk of coronary heart disease.
- VLDL can convert to LDL.
- More than 25% to 50% of Very Low-Density Lipoprotein (VLDL) is associated with increased coronary heart disease.
Functions of Very Low-Density Lipoprotein (VLDL):
- Very Low-Density Lipoprotein (VLDL) has the main role of transporting endogenously synthesized triglycerides by the liver to:
- Adipose tissue.
- Very Low-Density Lipoprotein (VLDL) carries triglycerides from the intestinal mucosa to the periphery.
- Very Low-Density Lipoprotein (VLDL) is mainly synthesized in the liver and, to a lesser extent, the intestinal tissues.
- Very Low-Density Lipoprotein (VLDL) passes through a transient intermediate lipoprotein form called intermediate-density lipoprotein (IDL).
- Intermediate-density lipoprotein (IDL) changes to Low-density lipoprotein (LDL).
Normal Very Low-Density Lipoprotein (VLDL)
- 7 to 32 mg/dL.
- 25% to 50%
|Borderline to high risk||140 to 159|
|Children and adolescents|
|Borderline – high risk||110 to 129|
Increased Very Low-Density Lipoprotein (VLDL) is seen in:
- Nephrotic syndrome.
- Glycogen storage diseases.
- Familial LDL lipoproteinemia.
- Chronic liver disease.
- Liver cell carcinoma.
- Cushing syndrome.
- Familial hypercholesterolemia.
Decreased Very Low-Density Lipoprotein (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 the liver to adipose tissue|
Note: Lipoproteins are described in detail in LDL and HDL.
Questions and answers:
Question 1: What is the complication of Very Low-Density Lipoprotein (VLDL)?
The main drawback is that it is atherogenic.
Question 2: Is Very Low-Density Lipoprotein (VLDL) increased in renal diseases?
Yes, Very Low-Density Lipoprotein (VLDL) is increased in renal diseases (Nephrotic syndrome).