28th October 2004
apolipoprotein A-1
What is being tested?
Apolipoproteins are the protein component of lipoproteins – complexes that transport lipids throughout the bloodstream. Apolipoproteins provide structural integrity to lipoproteins and shield the hydrophobic (water repellent) lipids at their center.
Most lipoproteins are cholesterol- or triglyceride-rich and carry lipids throughout the body, for uptake by cells. High-density lipoprotein (HDL – the “good” cholesterol), however, is like an empty taxi. It goes out to the tissues and picks up excess cholesterol, then transports it back to the liver. In the liver the cholesterol is either recycled for future use or excreted into bile. HDL’s reverse transport is the only way that cells can get rid of excess cholesterol. It helps protect the arteries and if there is enough HDL present, it can even reverse the build up of fatty plaques in the arteries (deposits that lead to atherosclerosis and coronary artery disease).
Apolipoprotein A is the taxi driver. It activates the enzymes that load cholesterol from the tissues into HDL and allows HDL to be recognized and bound by receptors in the liver at the end of the transport. There are two forms of apolipoprotein A, Apo A-I and Apo A-II. Apo A-I is found in greater proportion than Apo A-II (about 3 to 1). The concentration of Apo A-I can be measured directly and tends to rise and fall with HDL levels. This has led some experts to think that Apo A-I may be a better indicator of atherogenic risk than the HDL test.
Deficiencies in Apo A-I appear to correlate well with an increased risk of developing coronary artery disease (CAD) and peripheral vascular disease.
Why get tested?
To determine whether or not you have adequate levels of Apo A-I, and to help determine your risk of developing coronary artery disease (CAD)
When to get tested?
When you have hyperlipidemia and/or a family history of CAD or peripheral vascular disease; when your doctor is trying to assess your risk of developing heart disease; when you are monitoring the effectiveness of lipid treatment and/or lifestyle changes
How is it used?
Apo A-I may be ordered, along with other lipid tests, as part of a profile to help determine your risk of CAD. While it is not ordered routinely, it may be helpful in patients who have a personal or family history of heart disease and/or hyperlipidemia. Apo A-I levels may also be ordered to help diagnose conditions that cause Apo A-I deficiencies, and may be used to monitor the effectiveness of lifestyle changes and lipid treatments.
When is it ordered?
Apo A-I may be measured in patients with a personal or family history of hyperlipidemia and/or premature CAD. It may be ordered when your doctor is trying to determine the cause of your hyperlipidemia and/or suspects it may be due to a disorder that is causing a deficiency in Apo A-I.
Apo A-I may be ordered along with Apo B-100 when your doctor wants to check your Apo A/Apo B ratio (sometimes used as a CAD risk indicator, - basically showing the ratio of “good” to “bad” cholesterol.)
When you have undergone lipid lowering treatment or lifestyle changes (decreased the fat in your diet and increased your regular exercise), your doctor may order an Apo A-I, along with other tests, to monitor the effectiveness of the changes.
What does the test result mean?
An increase of Apo-I is usually not a problem, but decreased levels are associated with low levels of HDL and decreased clearance of excess cholesterol from the body. Decreased levels of Apo A-I, along with increased concentrations of Apo B-100 (Apo B), are associated with an increased risk of coronary artery disease.
There are some genetic disorders that lead to deficiencies in Apo A-I (and therefore to low levels of HDL). People with these disorders tend to have hyperlipidemia and higher levels of low-density lipoprotein (LDL – the “bad” cholesterol). Frequently, they have accelerated rates of atherosclerosis (the build up of fat plaques and hardened tissue in the arteries that can lead to heart attacks, heart disease, and strokes).
Apo A-I may be increased with:
Drugs such as: carbamazepine, estrogens, ethanol, lovastatin, niacin, oral contraceptives, phenobarbital, pravastatin, and simvastatin
Familial hyperalphalipoproteinemia (a rare genetic disorder)
Physical exercise
Pregnancy
Weight reduction
Apo A-I may be decreased with:
Chronic renal failure
Coronary artery disease
Drugs such as: androgens, beta blockers, diuretics, and progestins.
Familial hypoalphalipoproteinemia (a rare genetic disorder)
Smoking
· Uncontrolled diabetes
What can I do to raise my Apo A-I?
Regular exercise is one of the best ways to raise HDL and Apo A-I. By decreasing the fat in your diet, maintaining a healthy weight, and exercising you can help decrease your risk of developing heart disease.
Apo A1:
reference range:
male: 94-178 mg/dL
female: 101-199 mg/dL
What is being tested?
Apolipoproteins are the protein component of lipoproteins – complexes that transport lipids throughout the bloodstream. Apolipoproteins provide structural integrity to lipoproteins and shield the hydrophobic (water repellent) lipids at their center.
Most lipoproteins are cholesterol- or triglyceride-rich and carry lipids throughout the body, for uptake by cells. High-density lipoprotein (HDL – the “good” cholesterol), however, is like an empty taxi. It goes out to the tissues and picks up excess cholesterol, then transports it back to the liver. In the liver the cholesterol is either recycled for future use or excreted into bile. HDL’s reverse transport is the only way that cells can get rid of excess cholesterol. It helps protect the arteries and if there is enough HDL present, it can even reverse the build up of fatty plaques in the arteries (deposits that lead to atherosclerosis and coronary artery disease).
Apolipoprotein A is the taxi driver. It activates the enzymes that load cholesterol from the tissues into HDL and allows HDL to be recognized and bound by receptors in the liver at the end of the transport. There are two forms of apolipoprotein A, Apo A-I and Apo A-II. Apo A-I is found in greater proportion than Apo A-II (about 3 to 1). The concentration of Apo A-I can be measured directly and tends to rise and fall with HDL levels. This has led some experts to think that Apo A-I may be a better indicator of atherogenic risk than the HDL test.
Deficiencies in Apo A-I appear to correlate well with an increased risk of developing coronary artery disease (CAD) and peripheral vascular disease.
Why get tested?
To determine whether or not you have adequate levels of Apo A-I, and to help determine your risk of developing coronary artery disease (CAD)
When to get tested?
When you have hyperlipidemia and/or a family history of CAD or peripheral vascular disease; when your doctor is trying to assess your risk of developing heart disease; when you are monitoring the effectiveness of lipid treatment and/or lifestyle changes
How is it used?
Apo A-I may be ordered, along with other lipid tests, as part of a profile to help determine your risk of CAD. While it is not ordered routinely, it may be helpful in patients who have a personal or family history of heart disease and/or hyperlipidemia. Apo A-I levels may also be ordered to help diagnose conditions that cause Apo A-I deficiencies, and may be used to monitor the effectiveness of lifestyle changes and lipid treatments.
When is it ordered?
Apo A-I may be measured in patients with a personal or family history of hyperlipidemia and/or premature CAD. It may be ordered when your doctor is trying to determine the cause of your hyperlipidemia and/or suspects it may be due to a disorder that is causing a deficiency in Apo A-I.
Apo A-I may be ordered along with Apo B-100 when your doctor wants to check your Apo A/Apo B ratio (sometimes used as a CAD risk indicator, - basically showing the ratio of “good” to “bad” cholesterol.)
When you have undergone lipid lowering treatment or lifestyle changes (decreased the fat in your diet and increased your regular exercise), your doctor may order an Apo A-I, along with other tests, to monitor the effectiveness of the changes.
What does the test result mean?
An increase of Apo-I is usually not a problem, but decreased levels are associated with low levels of HDL and decreased clearance of excess cholesterol from the body. Decreased levels of Apo A-I, along with increased concentrations of Apo B-100 (Apo B), are associated with an increased risk of coronary artery disease.
There are some genetic disorders that lead to deficiencies in Apo A-I (and therefore to low levels of HDL). People with these disorders tend to have hyperlipidemia and higher levels of low-density lipoprotein (LDL – the “bad” cholesterol). Frequently, they have accelerated rates of atherosclerosis (the build up of fat plaques and hardened tissue in the arteries that can lead to heart attacks, heart disease, and strokes).
Apo A-I may be increased with:
Drugs such as: carbamazepine, estrogens, ethanol, lovastatin, niacin, oral contraceptives, phenobarbital, pravastatin, and simvastatin
Familial hyperalphalipoproteinemia (a rare genetic disorder)
Physical exercise
Pregnancy
Weight reduction
Apo A-I may be decreased with:
Chronic renal failure
Coronary artery disease
Drugs such as: androgens, beta blockers, diuretics, and progestins.
Familial hypoalphalipoproteinemia (a rare genetic disorder)
Smoking
· Uncontrolled diabetes
What can I do to raise my Apo A-I?
Regular exercise is one of the best ways to raise HDL and Apo A-I. By decreasing the fat in your diet, maintaining a healthy weight, and exercising you can help decrease your risk of developing heart disease.
Apo A1:
reference range:
male: 94-178 mg/dL
female: 101-199 mg/dL