L'Apoliproteina A-1 (Apo A-1) it is the main component of high density lipoproteins (or HDL), ie the so-called "good" cholesterol.
HDL removes excess cholesterol from cells and transports them to the liver for recycling or disposal.
Apolyprotein A-1 plays a specific role in lipid metabolism:
- Allows the transport of cholesterol and triglycerides into the bloodstream;
- It allows HDL to recognize specific receptors present on the membranes of some cells, in order to bind to them.
Polyprotein A-1 is usually measured together with Apo B (the main protein structural component of LDL, i.e. low density lipoproteins), to better frame the relationship between HDL and LDL cholesterol.
Apo A-1 values tend to increase and decrease along with HDL concentrations; therefore, Apo A-1 deficiency correlates with an increased risk of developing cardiovascular disease (CVD).
Apolipoprotein A-1, also known as APO1 or Apo A-1, is a human gene that codes for the homonymous protein, the main protein component of high density lipoprotein (HDL, the so-called "good" cholesterol).
Functions in the body
HDLs participate in the so-called reverse cholesterol transport, delivering excess lipid from peripheral tissues to the liver. This is an extremely important function, since only in the liver can excess cholesterol be removed from the body through the bile (which once poured into the intestine is partly reabsorbed and partly eliminated with the faeces).
Apolipoprotein A1, in particular, acts as a cofactor ofLCAT enzyme (Lecithin Cholesterol Acyl Transferase), capable, as the name implies, of esterifying cholesterol according to the following reaction:
The LCAT takes the polyunsaturated fatty acid present in position 2 of the lecithin and transfers it to the cholesterol, esterifying it. This reaction is very important, as it favors the distribution of cholesterol to various tissues and its incorporation into HDL, making it completely hydrophobic.
Polypoprotein A1 has also been isolated as a stabilizing factor la prostacyclin PGI2 (anti-inflammatory) and for that reason it might have a anticoagulant effect.
However, the most important and well-known function of apolipoprotein A1 remains that of "cleaning" the arteries of excess cholesterol.
Regular physical activity is the best way to increase the amount of good cholesterol by inducing the production of Apolipoprotein A1.
L'apolipoproteina A1 Milano it is a natural mutation of ApoA normally present in nature, discovered by studying some inhabitants of Limone del Garda. Such individuals, despite particularly low HDL levels, have a reduced vascular risk, since the mutation increases the protective effect of the lipoprotein.
The gene transfer of the gene that codes for the apoA1 Milano could therefore represent, in the near future, an excellent prophylaxis of atherosclerosis.
Because it is measured
Apolipoprotein A-1 is measured:
- To ascertain whether the patient has adequate Apo A-1 concentrations, particularly if the HDL high-density lipoprotein values are low;
- As a support in assessing the risk of developing cardiovascular disease (CVD), together with other lipid structure tests;
The Apo A-1 test can be ordered together with the Polypoprotein B (Apo B) to determine the Apo B / Apo A-1 ratio. The latter is sometimes used as an indirect index of the relationship between HDL and LDL, therefore between HDL cholesterol and LDL cholesterol in assessing the risk of developing CVD.
When is the exam prescribed?
The evaluation of the Polypoprotein A-1 is indicated:
- When the patient has high cholesterol and triglyceride concentrations (hyperlipidemia) and / or a personal or family history of heart disease, to determine the cause;
- If your doctor is trying to assess the risk of developing heart disease;
- To monitor the effectiveness of drug treatment to reduce lipid concentrations and / or lifestyle changes, such as a low-fat diet and increased, regular exercise.
- Donna: 115-220 mg/dl
- Man: 110-190 mg / dl
Apo A-1 Alta - Causes
An increase in serum Apo A-1 may be observed in association with:
- Familial hyper-alpha-lipoproteinemia;
- Taking drugs such as: carbamazepine, estrogen, lovastatin, niacin, oral contraceptives, phenobarbital, pravastatin and simvastatin;
- Weight loss
- Use of statins.
Apo A-1 Low - Causes
A reduction in serum Apo A-1 is associated with low HDL levels and decreased removal of excess cholesterol from the body. Low concentrations of Apolipoprotein A1, together with an increased concentration of Apo B, are associated with an increased risk of cardiovascular disease.
The reduction of Polypoprotein A1 may also depend on other factors, such as:
- Nephrotic syndrome;
- Chronic renal failure;
- Taking drugs such as: androgens, beta-blockers, diuretics and progestogens (synthetic progesterone);
- Hepatocellular disorders;
- Decompensated diabetes;
How it is measured
To test for apolipoprotein A-1, a blood sample must be taken from a vein in the arm or, in infants, from a puncture of the heel or finger.
Testing for apolipoprotein A-1 is usually done in conjunction with the complete lipid profile. For this reason, the patient may be required to fast for 12 hours before undergoing the test.
In the days preceding the sampling, then, it is recommended to maintain a diet as usual as possible.
Interpretation of Results
- A decrease in Apolypoprotein A1 can appear in cases of decompensated diabetes, liver disorders, nephropathies or following the intake of androgens, beta-blockers and diuretics. A reduction can also be induced by smoking and diets high in saturated fat and cholesterol.
- An increase in Polypoprotein A1 can occur after weight loss and when taking certain medications, such as estrogen, contraceptives and statins.