Gastric Ulcer

Helicobacter pylori and the Nickel Connection#

The dominant microbial cause of gastric ulceration is H. pylori, whose pathogenesis depends on nickel-containing enzymes that enable survival in the acidic gastric environment.

Nickel-dependent Urease constitutes up to 10% of the total H. pylori proteome and catalyzes urea hydrolysis to Ammonia and bicarbonate, neutralizing gastric acid in the immediate periplasmic environment.^{[1]Role of Nickel in Microbial PathogenesisRobert J. Maier, Stéphane L. Benoit · 2019Open reference 1 ↓}

Beyond acid buffering, urease has non-catalytic roles: promoting angiogenesis, disrupting tight junctions, inducing apoptosis in gastric epithelial cells, and activating blood platelets—all contributing to ulcer formation and persistence.

NiFe hydrogenase provides metabolic energy by oxidizing molecular hydrogen (H2), which is chronically available in the human stomach at approximately 80 microM. This energy powers the type IV secretion system and CagA translocation.^{[1]Role of Nickel in Microbial PathogenesisRobert J. Maier, Stéphane L. Benoit · 2019Open reference 1 ↓}

The Nickel dependency of H. pylori virulence makes this metal a selective pressure in gastric ecology: dietary and environmental nickel exposure may influence the severity of H. pylori-mediated disease.

Gastric Microbiome Beyond H. pylori#

While H. pylori dominates the gastric ulcer narrative, the broader gastric microbiome plays a role. The healthy stomach harbors a diverse community of Streptococcus, Prevotella, Veillonella, and Rothia species that is disrupted by H. pylori colonization.

Proton pump inhibitor (PPI) therapy, the standard treatment for gastric ulcers, raises gastric pH and permits colonization by oral and intestinal bacteria not normally found in the stomach.^{[2]Passing the 'Acid Test': Do Proton Pump Inhibitors Affect the Composition of the Microbiome?Dong T, Pisegna J · 2018Open reference 2 ↓}

PPI use also disrupts the gastric mycobiome, potentially promoting fungal overgrowth by Candida species.^{[3]Shi 2023 — PPI-Induced Fungal Dysbiosis in Patients with Gastroesophageal Reflux DiseaseYichao Shi, Jianfeng Li, Shuntian Cai et al. · 2023Open reference 3 ↓}

Associated Conditions#

Gastric Adenocarcinoma: Chronic H. pylori-driven gastric ulceration is a recognized precursor to gastric cancer through the Correa cascade (chronic gastritis to atrophic gastritis to intestinal metaplasia to dysplasia to carcinoma). The shared nickel-dependent virulence machinery links both conditions.

Gastroesophageal Reflux Disease (GERD): Gastric ulcers may coexist with or complicate GERD, and PPI treatment for both conditions carries similar microbiome consequences. Duodenal ulcer: Shares the H. pylori etiology but involves distinct pathophysiological mechanisms (increased acid secretion vs. decreased mucosal defense).

Environmental Factors#

Dietary nickel: Foods high in nickel (cocoa, nuts, legumes, whole grains) may modulate H. pylori virulence in colonized individuals, though direct evidence linking dietary nickel intake to ulcer risk is limited.

NSAIDs: Prostaglandin inhibition reduces mucosal defense independent of H. pylori, and the combination of NSAID use and H. pylori infection dramatically increases ulcer risk.