WEDNESDAY, Dec. 31, 2003 (HealthDayNews) -- California researchers have discovered a gene that can increase the risk of heart attack and stroke by launching an inflammatory attack against blood vessels.
For people who carry the gene, the finding reinforces a standard dietary recommendation for keeping arteries healthy: Eat more oily fish, such as salmon.
That advice is aimed at reducing blood levels of one sort of fatty molecule, low-density cholesterol. This time, the idea is to avoid foods containing n-6 polyunsaturated fatty acids, a class of fats that set off the inflammatory reaction. However, a different class of polyunsaturated fatty acids -- designated n-3, which are found in fish -- suppress the inflammatory response.
Inflammation has been big news in cardiovascular research recently. Study after study has shown that high blood levels of C-reactive protein, a marker of inflammation, are associated with increased risk of artery damage. But until now, no one has known why the inflammatory attack occurs.
"This is the first example of how a gene that causes inflammation is involved in artery blockage," says Hooman Allayee, a fellow in the human genetics department of the University of California at Los Angeles and leader of the team reporting the finding in the Jan. 1 issue of the New England Journal of Medicine.
Allayee and his colleagues have found a fairly common form of the gene for 5-lipoxygenase, a molecule involved in the body's defense against injury, can be activated by fatty acids in the diet to attack the arteries.
Inflammation is a basic defense mechanism, but it can often go wrong, causing diseases such as rheumatoid arthritis and asthma, explains study co-author James H. Dwyer, a professor of preventive medicine at the University of Southern California. In this case, the gene causes the attack to be aimed at the arteries, he says.
A study of 470 healthy Los Angeles residents found that about 6 percent of them carry the potentially dangerous form of the gene, Dwyer says. Detailed studies shown abnormal thickening of artery walls, a warning sign of cardiovascular disease, in the people with that form of the gene.
People who carry the dangerous version of the gene should avoid foods containing two n-6 polyunsaturated fats, arachidonic acid and linoleic acid, all of which stimulate the inflammatory activity, Dwyer says. Organ meats -- liver, heart, giblets -- should be avoided because they have high levels of arachidonic acid. Vegetable oils from corn and soybeans should be avoided because they are rich in linoleic acid, he says. Olive oil is preferable because it has a lot of n-3 polyunsaturated fatty acids, which prevent inflammation.
The gene "is more prevalent in people of non-European ancestry, such as blacks and Asians," Dwyer says. "About 10 to 20 percent of them have this form of the gene. Specific dietary and pharmaceutical intervention should be effective in this group."
The variant form of the gene seems to make a normal process of repairing injury to an artery become dangerous, Dwyer says. "If our findings are confirmed to show that people carrying this genotype are at increased risk, it won't be long until we have a routine clinical test to detect it," he says.
But these are "early days," Dwyer adds. "We need a lot more practical experience."
More information
You can learn what is known about the role of inflammation in heart disease from the American Heart Association. Meanwhile, read about heart-healthy foods from the Mayo Clinic.
