"You have obesity and you have hypertension. Where is the link?" says Dr. Gregory A. Harshfield, principal investigator on the $1.4 million grant from the NIH's National Heart, Lung and Blood Institute that will study 160 adolescents, half lean and half overweight or obese, in pursuit of that link. Dr. Paule Barbeau, exercise physiologist, is a co-investigator

Obesity is a risk factor for high blood pressure, which is a major risk factor for cardiovascular disease.

The Augusta researchers and others leaders in the field of hypertension say that obesity may increase pressure by increasing volume rather than constriction.

"We think it's increased volume because of sodium handling," Dr. Harshfield says. "When we put people under stress, the normal response is to increase your blood pressure through vasoconstriction." The kidneys also hold onto sodium to help increase blood volume throughout the body. As the stress ends, so should these normal physiological responses.

But Dr. Harshfield's studies at MCG's Georgia Prevention Institute have shown that some people keep holding onto sodium long after the stress has gone, delaying a process called natriuresis, the body's way of eliminating sodium. His studies have shown this mechanism is impaired in about 30 percent of adolescent blacks and 15 percent of adolescent whites; the prolonged, elevated pressures may contribute to the development of hypertension.

Fat, or adipose tissue, was once considered storage material only, says Dr. Barbeau. "Now we realize that it secretes all kinds of substances, such as angiotensinogen (which constricts blood vessels) and leptin. The more fat you have, the more of these substances you make."

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Contact: Toni Baker
tbaker@mail.mcg.edu
706-721-4421
Medical College of Georgia
9-Sep-2003