MONDAY, Nov. 10, 2003 (HealthDayNews) -- A team of scientists working with human fat cells called adipocytes has discovered a direct link between these cells and hormones known to increase blood pressure.
"Fat cells secrete products that directly stimulate the release of aldosterone, which is responsible for high blood pressure," says lead researcher Monika Ehrhart-Bornstein, from the German Diabetes Center at Heinrich Heine University in Dusseldorf.
"It is known that high blood pressure is present with obesity, but the connection between the two has remained unknown," she adds.
It once was thought that fat tissue only stored lipids. However, new research has found fat tissue also secretes hormones. And it is also known a malfunction in the adrenal gland is linked to obesity. This malfunction leads to an excessive release of aldosterone, a blood pressure-elevating steroid that causes the kidneys to hold on to salt.
While this relationship was known, how fat itself contributed to high blood pressure was not. Ehrhart-Bornstein and her colleagues studied whether hormones secreted by fat cells affected the production of aldosterone from the adrenal gland.
In experiments with human cells, her team found that when products secreted by fat cells were combined with cells from the adrenal gland, these fat cell products caused a sevenfold increase in aldosterone secretion.
These findings indicate that "fat cells are directly responsible for this increase in blood pressure," Ehrhart-Bornstein says. However, which specific factors in fat cells causes this release of aldosterone is still not known, she adds.
The new study appears in this week's issue of the Proceedings of the National Academy of Sciences.
Ehrhart-Bornstein and her team are busy at work trying to identify which of these previously unidentified fat cell secretions might be responsible.
Until these factors have been identified, there are no direct clinical implications to the findings, she cautions. However, in the future it could lead to new approaches for treating high blood pressure.
Dr. Theodore Goodfriend, a professor of medicine at the University of Wisconsin, has a different theory on the relationship between fat tissue and high blood pressure.
He says "people with visceral obesity -- that is abdominal obesity -- are more likely than lean people and more likely than people with lower-body obesity to have high blood pressure."
He adds the link between abdominal fat and high blood pressure is mysterious. "But I think it is the result of a 'factor' or chemical released from abdominal fat that is further transformed by the liver."
The factor stimulates the adrenal gland to make aldosterone, Goodfriend says. "We have found an association of visceral obesity with elevated aldosterone in some patients," he adds.
"This factor is more often found in people with visceral fat, because that fat drains to the liver directly, whereas other fat stores drain into the general circulation," Goodfriend notes.
He also points out that the authors of the new study "apparently feel they have found a factor released by fat cells that does not have to be further transformed by the liver. But they haven't identified their factor."
Goodfriend advises that "clinicians could benefit from their and my research by thinking of using aldosterone antagonists, such as spironolactone or eplerenone, in hypertensive patients with upper body obesity. We have found those drugs very useful in stubborn cases."