Approximately 40 percent of African Americans have hypertension — the highest rate of any racial or ethnic group in the United States — but there is little data about what makes them more susceptible to this condition.

Temple University researcher Michael D. Brown, Ph.D., has turned to genes — the biologic units of heredity — for some answers.

With a recently awarded $3.5 million National Institute of Health grant, Brown will be the first to study how genes can contribute to hypertension or high blood pressure in African Americans.

He will do this by monitoring the genetic makeup of arteries as they respond to exercise, as physical activity plays a role in affecting blood pressure levels.

“The fact that hypertension tends to run in families and is more prevalent in some races than others, suggests that genes may be involved in some way,” Brown said.

The health consequences of hypertension are devastating for African Americans.

Often times they develop hypertension at an early age, which can lead to an 80 percent greater rate of fatal stroke and a 50 percent greater rate of heart disease deaths than whites, according to the American Heart Association.

The project is novel for combining research from the “science world and the real world,” said Brown, who has a background in exercise physiology. The “real world” aspect will involve enrolling up to 350 African Americans for the five-year study this fall. Study participants will incorporate an exercise routine and other lifestyle changes to improve overall health.

“We hope to identify genes that help us understand who best will respond to exercise in terms of lowering blood pressure,” Brown said. “Exercise will be our medicine. We’ll be giving it in specific doses.”

Brown, who is racially mixed, has a stake in the research as well. His father, who is African American, suffers from hypertension and heart disease. His grandmother died of stroke and had hypertension. Various aunts and uncles face similar complications. Even Brown has borderline high blood pressure despite maintaining an exercise routine and a healthy diet.

Exercise is one way to treat high blood pressure, a condition where the force pushing out against the blood vessels is too high. High blood pressure is dangerous because it makes the heart work harder to pump blood to the body and because it contributes to hardening of the arteries. Brown’s work could also give clues into how other therapies such as a reduced-salt diet and medication can help, he said.

The grant allows Brown to build on his research in this area from the past decade. In an article due to appear this fall, Brown and his colleagues present findings on how a gene called NFKB1 affects the cells that line blood vessels and how it affects how blood vessels change with exercise in the general population.

With hypertension, the cells that line the blood vessels can change for the worse. Without exercise, a gene leading to hypertension could express itself in a way that makes it more likely that blood pressure will rise. On the other hand, exercise — which gets the blood pumping — creates a stress on the cells called “shear stress” that can produce a healthy vascular system. Researchers will measure this stress through an ultrasound method.

In a lab, Brown will reproduce the same “shear stress” to the cells in order to examine the genetic changes at a deeper level. The cells, produced from a lab for research purposes, will have a similar genetic makeup of the study participants.

Ultimately, Brown hopes to identify groups of genes that behave alike in humans and in the lab. This would show which expressions of genes decrease the chances of hypertension.

“I feel strongly about this project. It’s the right thing and the right time,” Brown said. “We still don’t know why hypertension occurs. We just know that you get it.”