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NEW YORK (Reuters Health) - Fat cells produce factors that directly stimulate the adrenal gland to release the hormone aldosterone, new findings show. Because aldosterone regulates blood pressure, these factors may at least partly explain the link between obesity and high blood pressure.

Dr. Monika Ehrhart-Bornstein, of the German Diabetes Center in Dusseldorf, and colleagues first incubated white fat tissue in a culture medium, then removed the fat tissue and exposed adrenal cells to the remaining "fat cell-conditioned medium."

As they report in the Proceedings of the National Academy of Sciences, aldosterone secretion by the adrenal cells increased more than sevenfold over a 24 hour period.

Other hormones produced by the cells also increased: cortisol was nearly tripled, and dehydroepiandrosterone (DHEA) levels increased 1.5-fold.

The factors responsible for these effects remain something of a puzzle. The team was able to rule out five possible compounds, but figured out two new factors appeared to be responsible for more than 90 percent of the stimulatory effect.

In an interview with Reuters Health, Dr. Ehrhart-Bornstein theorized that levels of the adrenal-stimulating factors produced by fat cells would decline, along with the amount of fat stored in the cells, if someone lost weight. Thus, the cells would provoke less aldosterone production and blood pressure would go down.

Her group is now in the process of further characterizing the new factors they have identified.

SOURCE: Proceedings of the National Academy of Sciences, published online November 10th 2003