The gene codes for an enzyme called GRK5, which depresses the response to adrenaline and similar hormonal substances that increase how hard the heart works. Adrenaline is a hormone released from the adrenal glands that prompts the "fight-or-flight" response it increases cardiac output to give a sudden burst of energy.
In heart failure, decreased blood flow from the struggling heart ramps up the body's secretion of adrenaline to compensate for a lower blood flow. Overproduction of the hormone makes the weakened heart pump harder, but eventually worsens heart failure.
Beta blockers alleviate this problem by blocking adrenaline at its receptor in the heart and blood vessels. GRK enzymes mimic this effect by serving as "speed governors" that work like the governor in an engine to prevent adrenaline from over-revving the heart, says Dorn.
The researchers including three equally contributing co-authors: Liggett, Sharon Cresci, M.D., assistant professor of medicine in the Cardiovascular Division at Washington University and a cardiologist at Barnes-Jewish Hospital, and Reagan J. Kelly, Ph.D., at the University of Michigan found that 41 percent of African-Americans have a variant GRK5 gene that more effectively suppresses the action of adrenaline than the more common version of the gene. People with the variant gene could be said to have a natural beta blocker, Dorn says. The variant is extremely rare in Caucasians, accounting for its predominant effects in African-Americans.
The researchers showed that African-American heart failure patients with this genetic variant have about the same survival rate even if th
|Contact: Gwen Ericson|
Washington University School of Medicine