Say that you slip with the knife while cutting up an apple for lunch. Ouch. It may bleed a bit, but you know that pretty soon it will stop.
A whole cascade of events takes place to form a blood clot. The ITGB3 gene codes for the fibrinogen receptor that is a part of how platelets form clots. This clotting action vitally important when you cut yourself — but clotting too much or too quickly can also be a problem for heart attacks and strokes.
There are hundreds of studies on the ITGB3 genetic variant known as PIA1/A2. Here is an overview of some of the findings:
- A study of 80 men, aged 20-25 years, found that those who carry the A2 variant had faster blood clotting times. The study also found that many (but not all) of the variant carriers were also resistant to the blood-thinning effects of aspirin.[ref]
- Women carrying the variant were at an increased risk for having recurrent miscarriages. [ref]
- A study of men who died of sudden cardiac death found that the A2 variant more than doubled the risk of sudden cardiac death under the age of 50. [ref]
- A study that included both men and women found that only women who carried of the A2 variant were at a higher risk of deep venous thrombosis. [ref]
- An overall meta-analysis that combined the data from 14 studies concluded that there is a statistical increase in the risk of heart attacks. This wasn’t a big increase in risk for the overall population (8%), but it had a slightly bigger impact on people younger than age 45 (a 20% increase in risk). Keep in mind, though, that the risk of heart attack is low in people younger than 45. [ref]
- Researchers looked at 1202 Caucasian patient in an atherosclerosis study and found that the A2 variant carriers may be predisposed to “increased risk of atherosclerotic plaque rupture.”[ref]
- A study of Pakistani patients found that the variant has no impact on aspirin resistance. [ref]
- A study of male physicians found that carrying the A2 variant did not increase the risk of stroke, heart attack, or DVT.[ref]
While this genetic variant does seem to increase the risk for various cardiovascular events, keep in mind that it is probably acting together with other genes, gender, and environmental factors.
Most genetic variants that have a ‘down’ side also have an ‘up’ side. There is a reason that they are still prevalent in the population. The downside of the A2 variant here is obvious – increased early heart attack deaths without modern medical care. If people carrying this ITGB3 gene variant died from early heart attacks, at some point the variant should have dwindled out in the human population. Instead, there is a positive reason that it is still in the population – and this is due to protection from dying from contagions that cause excessive bleeding.
A new study shows that carriers of the A2 variant are protected from getting the hantavirus. The hantavirus is spread in mouse and rat feces, and, in Chile, it has a mortality rate of 30-35%. The virus causes cardiopulmonary responses due to increased vascular permeability. The study found that those people carrying the A2 variant were less likely to get the hantavirus. The study looked at both people who got the virus and people exposed to the virus who didn’t get it. None of the hantavirus patients (n=74) carried two copies of the variant; in the group that was exposed through close household contact to the virus (n=105), 11% of the group carried two copies of the variant. [ref]
- C/C: two copies of the A2 variant, increased risk of heart disease, may not benefit from aspirin for heart attack prevention, protection against Hantavirus [ref][ref][ref]
- C/T: somewhat increased risk of heart disease, may not benefit as much from aspirin for heart attack prevention, protection against Hantavirus [ref][ref][ref]
- T/T: normal