Researchers study why people who are obese become hypertensive

Apr 22 2009

When Francois Abboud began his work at the University of Iowa in 1960, little was known about the constant physiological chatter between the brain and the blood vessels.

His research since has helped unravel how this chatter adjusts blood pressure and blood flow to meet the body's constantly changing demands.

The work has already led to clinical advances, and more may be on the way: Dr. Abboud defined the identity of a sensor in the nerve endings in the carotid artery in the neck that rapidly lowers blood pressure when stimulated. A clinical trial is now underway to see if people who are hypertensive can lower their blood pressure by using a pacemaker-like device that stimulates the nerve endings in the blood vessels.

Ann M. Schreihofer focuses on the role the brain plays in increasing sympathetic nervous activity, which contributes to many forms of hypertension (high blood pressure). Her Medical College of Georgia laboratory studies the links between conditions such as obesity and the chronic intermittent hypoxia that happens in sleep apnea and chronic activation of the sympathetic nervous system.

"We're studying why people who are obese become hypertensive," Dr. Schreihofer said of one aspect of her work. "We believe this is due to something about the obese state: We don't know what that is, but we're starting to rule things out." Indeed, the Schreihofer laboratory has already answered one question: Does hypertension occur because the brain loses its ability to sense that the blood vessels are stretching under high pressure? In a study with obese rats, they found the rats' brains could sense the stretch but still became hypertensive, eliminating that mechanism as a possibility.

APS recognizes important research

The American Physiological Society (APS) presented its highest award, the Walter B. Cannon Award, to Dr. Abboud. He is the 27th recipient of the Cannon Award, which goes to an outstanding scientist, and delivered the Walter B. Cannon Physiology in Perspective lecture on April 18. The lecture is part of the 122nd annual meeting of the APS, which is part of Experimental Biology 2009.

The Society has awarded Dr. Schreihofer the Henry Pickering Bowditch Memorial Award for early-career achievement. She is the 53rd recipient of the award, which goes to a scientist younger than 42 years whose accomplishments are both original and outstanding. It is the Society's second-highest award. Dr. Schreihofer presented the Bowditch lecture on April 19, at the APS session of Experimental Biology 2009.

Distinguished careers

Dr. Abboud is the Edith King Pearson Chair in Cardiovascular Research and director of the Cardiovascular Research Center at the Carver College of Medicine at the University of Iowa. He is a past-president of the American Heart Association, a former editor of Physiology in Medicine (Annals of Internal Medicine) and past president of the Association of American Physicians. He is a member of the National Academies of Science and the American Academy of Arts and Sciences.

Dr. Schreihofer has won three previous awards from The American Physiological Society. She established her own laboratory at the Medical College of Georgia in 2001. Still at the beginning of her career, she has already co-authored more than 35 studies in peer-reviewed journals, including the Journal of Physiology, Journal of Neuroscience and the American Journal of Physiology.

Dr. Abboud has helped discover how the brain uses hormones to orchestrate blood flow to different parts of the body. This helped explain how the brain sends blood to the gastrointestinal tract after eating, but redirects it to the heart and muscles if we start running, for example.

Recently, his team has been looking at which genes regulate ion channels, microscopic gates that move chemicals in and out of cells, and that play a role in the signaling between the brain and the blood vessels. In experiments with animals, Dr. Abboud and his colleagues deleted one specific ion channel and found that the animals developed high blood pressure. Work is now planned to develop a blood test to identify patients who suffer high blood pressure or heart failure because of a problem with the gene that regulates the channel, Dr. Abboud said.

New work underway

Dr. Schreihofer's laboratory has identified neurotransmitters that are at work in the brain stem that regulate sympathetic nervous activity. Neurotransmitters relay signals from one nerve cell to another, allowing nerve cells to 'talk' to each other. The Schreihofer laboratory will:

• Test the hypothesis that neurons that inhibit sympathetic activity lose their ability to do so. This may allow the neurons that stimulate sympathetic activity to get the upper hand, which leads to hypertension.

• Study how the brain stem neurons that regulate breathing impact neurons that control blood pressure. The neurons that integrate these systems are in very close proximity in the ventral lateral medulla and play a role in affecting both breathing and blood pressure. This connection is intriguing because it raises the possibility that improving respiratory function could be a way to reduce the sympathetic activity that leads to obesity and hypertension.

Editor's Notes: To arrange an interview with Dr. Abboud or Dr. Schreihofer, please contact Christine Guilfoy 301 634-7253 or at [email protected] .

Physiology is the study of how molecules, cells, tissues and organs function to create health or disease. The American Physiological Society (APS) has been an integral part of this scientific discovery process since it was established in 1887.

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