A UT Arlington researcher’s
recent work may hold clues as to why hypertension is more severe and strikes
earlier in the African-American population.
David Keller, an assistant
professor of kinesiology and associate director of UT Arlington’s Center for Health
Living and Longevity, has found differences in the way that African Americans
and Caucasians respond to simulated hypertension. When tested, African-American men in his
study showed a blunted ability to reflexively adjust their heart rates in
response to short-term hypertension
Keller is studying arterial baroreflex
function in African Americans at rest and during exercise as part of a project
funded by the National Institutes of Health National Heart, Lung and Blood
Institute. Results of the first phase of
his work were recently published in the American
Journal of Physiology: Heart and Circulatory Physiology, in an article called
“Carotid baroreflex responsiveness is impaired in normotensive African American
More than 40 percent of
non-Hispanic blacks have high blood pressure, also known as hypertension,
according to the American Heart Association. The rate of hypertension in the general
population is one in three. The condition can lead to heart disease or stroke. Additionally, African Americans
are at nearly double the risk of fatal stroke related to hypertension and
are more than four times more likely to develop end-stage renal disease
associated with hypertension than Caucasians.
“While some lifestyle factors are known
predictors, there remains much that we must understand about the way in which
the disease develops and factors that contribute to its development,” said
Carolyn Cason, interim vice president for research at UT Arlington. “Research
like that being done by Dr. Keller is key to establishing the scientific
foundation upon which new, successful treatments can be built."
Co-authors on the
study were former UT Arlington graduate students Seth Holwerda and Diana
Fulton, as well as Wendy Eubank-Holden, currently a postdoctoral research
associate at UT Health Science Center in Fort Worth.
for Healthy Living and Longevity is very focused on addressing serious health
issues that affect the community here in North Texas and across the U.S.,"
said Lou Fincher, chairwoman of the kinesiology department at UT Arlington.
"David Keller's research allows students to participate in work that could
one day help everyone know more about their risks for developing
The arterial baroreflex is the primary short-term
regulator of arterial blood pressure. The baroreflex receptors, or “sensors”
are located in the large blood vessels in the neck and the aorta. The
reflex works with the brain to monitor blood pressure levels and increase or
decrease blood supply based on the needs of the body.
Keller and his co-authors selected
30 men, ages 18 to 33, for their study, half of who were Caucasian and half of who
were African American. None of the study participants had a history of either
hypertension (high blood pressure) or hypotension (low blood pressure). During
the experiments, researchers simulated both conditions with pressure or suction
applied to the participants’ necks for short periods of time.
The team monitored the
participants’ heart rates and mean arterial pressure, which is the pressure
across the walls of their arteries.
“At rest ability to control
blood pressure was not markedly different, but the ability to reflexively
control the heart rate was different, especially in simulated hypertension,”
Keller said. “This seems to reflect something inherently different about short
term blood pressure regulation. We believe those differences may persist and
could be involved in the long term regulation and could help to explain the
increased incidence of hypertension in African Americans.”
Keller would like to explore
what role the vagus nerve, which regulates heart rate, plays in these racial
differences. Next, he plans to study participants’ responses to the same
experiments while they are exercising.
Keller was recently asked to
participate in an American Journal of Physiology podcast about his work. It is
available here: http://ajpheart.podbean.com/2011/11/03/carotid-baroreflex-responsiveness-is-impaired-in-normotensive-african-american-men/.
Keller’s work is an
example of the cutting-edge research taking place at The University of Texas at
Arlington, a comprehensive research institution of 33,439 students in the heart
of North Texas. Visit www.uta.edu
to learn more.