Helicobacter pylori has received much attention as the cause of stomach ulcers, but new research by scientists at the Howard Hughes Medical Institute (HHMI) at the University of Michigan shows that many other types of bacteria can cause the gastritis and ulcers that can ultimately lead to cancer. The new research suggests that gastritis and ulcers are triggered by bacterial overgrowth, rather than by stomach acidity.

The researchers say their work suggests that long-term treatment of patients with potent acid blockers, called proton pump inhibitors, which produce a more alkaline environment that is unfriendly to acid-tolerant Helicobacter pylori, may actually allow the overgrowth of other types of bacteria, including Lactobacillus, Enterobacter, Staphylococcus and Probionibacterium. Overgrowth is excessive proliferation of bacteria. Proton pump inhibitors dissipate stomach acid, which serves an important anti-microbial function and protects the body from ingested microorganisms.

The findings were published in articles in the January 2002 issues of Gastroenterology and the American Journal of Physiology -- Gastrointestinal and Liver Physiology by HHMI investigator Juanita L. Merchant and colleagues at the University of Michigan.

The researchers were studying the action of the hormone gastrin, which is produced by specific cells in the stomach called G-cells. Gastrin stimulates growth and acid secretion in parietal cells, another set of cells found in the stomach.

The textbook understanding of how acid secretion is regulated is that an alkaline pH in the stomach triggers gastrin release, said Merchant. Once gastrin has restored an acid pH by stimulating parietal cells, acid production is supposed to shut down by way of a feedback control mechanism in which the suppressing hormone somatostatin is secreted from D-cell
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Contact: Jim Keeley
keeleyj@hhmi.org
301-215-8858
Howard Hughes Medical Institute
15-Jan-2002