Autoimmune Gastritis

Autoimmune atrophic gastritis (AAG) is an organ-specific autoimmune disease that primarily affects the gastric body and fundus while sparing the antrum. Its characteristics include destruction of gastric wall cells, loss of intrinsic factors, and atrophy of the gastric mucosa. Endoscopic examination reveals features of reverse atrophy, with significant atrophy in the gastric body and fundus, appearing as a mosaic of red and white patches. Currently, AAG is believed to result from a pathological CD4+ T-cell-mediated autoimmune response against the gastric H+/K+-ATPase. CD4+ T lymphocytes target the parietal cells' H+/K+-ATPase, stimulating plasma cells to secrete autoantibodies, including parietal cell antibodies (PCA) and intrinsic factor antibodies (IFA). The former plays a key role in parietal cell destruction and glandular atrophy. AAG is considered a premalignant condition, with the potential development of gastric dysplasia, cancer, and type 1 gastric neuroendocrine tumours (type 1 g-NET). Gastric neuroendocrine tumors (g-NETs), also known as gastric carcinoids, account for approximately 23% of gastrointestinal and pancreatic neuroendocrine tumors. Clinically, g-NETs are mainly classified into three types. Type III is typically sporadic tumors associated with normal gastrin levels and poor prognosis. Although type 1 g-NETs caused by AAG are usually well-differentiated, studies have reported that 8%-23% of type 1 g-NETs extending into the deep submucosal layer may metastasize to regional lymph nodes or even to the liver. Furthermore, 3% of patients may develop neuroendocrine carcinoma, highlighting the need for appropriate attention. Due to the destruction of gastric glands (including parietal and chief cells) in AAG patients, there is a deficiency in intrinsic factor, gastric acid, and a decrease in pepsinogen I (PG-I) levels. Insufficient gastric acid secretion leads to a compensatory increase in gastrin secretion by G cells in the gastric antrum, which acts on receptors present in enterochromaffin-like cells (ECL) in the gastric body and fundus, promoting ECL cell proliferation. Prolonged stimulation by hypergastrinemia can result in the development of ECL cell tumors, namely type 1 g-NETs. Considering the close association between type 1 g-NETs and AAG, primarily related to hypergastrinemia resulting from reduced gastric acid secretion, it is hypothesized that supplementation with gastric acid could provide negative feedback regulation of gastrin, reducing the risk of type 1 g-NET development in AAG patients. This study aims to investigate the impact of Betaine hydrochloride(BHCL) on gastrin levels in AAG patients, thus exploring a simple and cost-effective method to reduce the risk of type 1 g-NETs in AAG patients.

Evaluate the prevalence of small intestinal bacterial overgrowth in patients with autoimmune gastritis (AIG) through hydrogen and methane breath testing, and determine whether there are differences in the positive rates of hydrogen and methane breath testing among the AIG group, the acid suppression group, and the control group.

Autoimmune gastritis (AIG) is a chronic autoimmune disorder characterized by parietal cell destruction and oxyntic mucosal atrophy, leading to achlorhydria and intrinsic factor deficiency. These pathological changes impair iron and vitamin B12 absorption, resulting in iron-deficiency anemia, pernicious anemia, and neuropsychiatric manifestations. Notably, 4-12% of AIG patients develop type 1 gastric neuroendocrine tumors, while facing a 3-7 fold increased risk of gastric adenocarcinoma with an incidence of 0.9-9%. Current management of AIG is limited to iron and vitamin B12 replacement, as no disease-modifying therapies exist. The progressive hypochlorhydria reduces pepsin activity, impairs gastric motility, and promotes small intestinal bacterial overgrowth (SIBO), causing dyspeptic symptoms and micronutrient malabsorption. Furthermore, gastric hypoacidity increases N-nitroso compound formation and triggers hypergastrinemia, elevating risks for both gastric cancer and neuroendocrine tumors. This clinical trial investigates whether betaine hydrochloride (with pepsin) supplementation can restore gastric acidity and improve clinical outcomes in AIG. We will evaluate its effects on gastrin levels, gastrointestinal symptoms, exhaled gas markers (NO, H₂S, H₂, CH₄), anemia parameters, endoscopic atrophy scores, and incidence of gastric complications (hyperplastic polyps, neuroendocrine tumors, and adenocarcinoma). The study aims to provide evidence for a potential therapeutic strategy addressing both symptoms and long-term complications of AIG.

Autoimmune gastritis is currently relatively rare in China due to its insidious onset, diverse clinical manifestations involving multiple systems such as digestive, hematological, and nervous systems, and its association with other autoimmune diseases. It can also be complicated by hyperplastic gastric polyps, gastric neuroendocrine tumors, gastric adenocarcinoma, and other diseases, making it prone to clinical misdiagnosis. As a form of gastritis in the post-Helicobacter pylori era, its detection rate has been gradually increasing with the continuous improvement of endoscopic technology in China. Applying the PDCA cycle management in disease diagnosis can significantly improve the detection rate of the disease, benefiting patients. Through the PDCA management model, this study further enhanced gastroenterologists' understanding of this disease from various aspects, aiming to improve the clinical diagnosis of autoimmune gastritis.