A team led by a Heart and Stroke Foundation researcher has uncovered a series of genes linking mental stress, high blood pressure, alcoholism and tobacco addiction.
Discovering and mapping these genetic pathways leading to major heart disease and stroke risk factors is the latest breakthrough from ongoing studies in the Saguenay-Lac St. Jean region of Quebec.
"Our results remind us that we are lucky that biology is not entirely destiny," team director Dr. Pavel Hamet told the Canadian Cardiovascular Congress 2007, co-hosted by the Heart and Stroke Foundation and the Canadian Cardiovascular Society.
"Fortunately, one's genetic inheritance consequences can be modified to a significant extent by living a heart-healthy lifestyle," says Dr. Hamet.
The most recent studies from the Saguenay focus on sexual differences and alcoholism. "The genes we discovered that govern alcohol intake appear on chromosome X," says Dr. Hamet.
Male cells have only one chromosome X. So males are more at risk than women (who have two). "This may explain why males are more prone to alcohol abuse," he says. "Our research indicates that when the father is affected, half of the siblings will be affected, but when the mother is affected three quarters of the siblings will be affected," he noted.
"On the other hand, when parents are not affected, one quarter of the siblings still can be, depending on the environment."
According to Dr. Hamet, there is no reason to believe that people from the Saguenay have higher rates of stress, high blood pressure, alcoholism, or tobacco addiction, but the genes that cause these conditions are easier to find because family histories are so well documented.
"The Saguenay studies are allowing us to take the first steps in individualized, predictive genomics," said Dr. Hamet. That means better targeted treatments for all Canadians.
"For example, knowing that there is a gene that produces the symptoms we associate with mental stress means we can bypass the expression of that gene by avoiding stress-provoking situations," he says. And for some people, there is a definite behavioural component to high blood pressure. "These are the patients who respond well to exercise and lifestyle changes," says Dr. Hamet.
The inhabitants of Saguenay Lac St. Jean have been making a unique contribution to medical genetics for over a decade.
The area has been relatively isolated from the rest of Quebec and Canada. The region was occupied in three waves in the 17th century by settlers from France. Many families live on their original farms or work at the same trades as their ancestors.
Large families were the norm and until the early 1960s it was not unusual for families to have up to 12 children - a remarkable expansion of the original genome. In addition, their genealogies (family trees) have been computerized, including cause of death whenever present.