Apolipoprotein B
| See Also | Lab Tests |
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Apolipoproteins are a protein component of lipoprotein complexes. Apolipoprotein A-1 is the major component of HDL, while Apolipoprotein B-100 is the major component of LDL. This test is often done when there is a family history of cardiovascular disease and/or hyperlipidemia.[1],[2]
Discussion
There are two forms of apolipoprotein B: apo B-100 and apo B-48. Apo B-100 is made by the liver, while apo B-48 is produced in the intestines. Apo B-48 is responsible for the initial transport of dietary lipids (fats) from the intestines to the liver. In the liver these lipids are combined with apo B-100 to form triglyceride-rich very low density lipoproteins (VLDL). In the blood these VLDL are transformed into low density lipoproteins (LDL) which when elevated are associated with an increased risk of atherosclerotic coronary artery disease.
- The cholesterol the LDL and apo B-100 transport is vital for cell membrane integrity, sex hormone production and steroid production. In excess, LDL can lead to fatty deposits (plaques) in the artery walls and leads to hardening and scarring of the blood vessels and atherosclerosis.
Patient Preparation
- Patient must fast for 12- 14 hours before testing. Water is permitted.
- Smoking is prohibited.
- Factors which can cause increased levels include:
- Diets high in saturated fats and cholesterol
- Drugs: androgens, beta blockers, diuretics, ethanol, and progestins
- Factors which can cause decreased levels:
- Diets high in polyunsaturated fats
- Drugs: cholestyramine, estrogen (postmenopausal women), lovastatin, simvastatin, neomycin, niacin, and thyroxine
Clinical Implications
- High levels indicate:
- increased incidence or premature coronary artery disease and atherosclerosis. It can also be associated with Type II Diabetes, hypothyroidism, nephrotic syndrome, renal failure, porphyria and cushing's syndrome.
- Low levels indicate:
- lowered incidence of cardiovascular disease. It can also indicate hypothyroidism, malnutrition, malabsorption, chronic anemias, Reye's syndrome, acute stress and inflammatory joint disease.
Associated Tests
Apolipoprotein A-1, Triglycerides, cholesterol, LDL, HDL, VLDL, Uric acid, Lipid electrophoresis, RBC, HCT, and HGB
References
- ↑ Pagana Kathleen D, Pagana Timothy J (1998) Mosby's Manual of Diagnostic and Laboratory Tests, Mosby, Inc
- ↑ Weatherby Dicken, Ferguson Scott (2002) Blood Chemistry and CBC Analysis: Clinical Laboratory Testing from a Functional Perspective, Bear Mountain
