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OthersUEG Week 2024 (Autoimmune gastritis)

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2024-10-08
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UEG Week (2024) - Autoimmune atrophic gastritis 


GUT MICROBIOTA AND AUTOIMMUNE ATROPHIC GASTRITIS

Introduction: Autoimmune Atrophic Gastritis (AAG) is a chronic immune-mediated condition that mainly affects the body and fundus of the stomach. AAG is often under-diagnosed due to the slow progression of the disease and a variable spectrum of symptoms. Recent data suggests a potential role of altered gastric microbiota in the natural history of AAG, due to the potential overgrowth of bacteria linked to the development of neoplastic complications (neuroendocrine tumors- NETs and gastric cancer) (1,2). Moreover, the same data hypothesizes the use of fecal microbiota as a possible non-invasive marker to diagnose and monitor AAG. Thus, we aimed to prospectively characterize the salivary and fecal microbiota of patients with AAG to provide further insights in this field.

Aims & Methods: We collected salivary and fecal samples from consecutive patients with an established diagnosis of AAG, enrolled at the Gastroenterology Unit of Azienda Ospedale Università Padova from March to June 2023 at the time of endoscopic follow-up examination. All patients needed to be off Proton-Pump Inhibitors, antibiotics, and probiotics for at least one month before enrolment. Stool samples were collected by the patients on the day of the endoscopy, transferred in a buffer solution, and stored at -20°C. Oral samples were collected through salivary commercial kits and freezed at -20°C. Both salivary and faecal samples were analyzed by BMR Genomic (Padua, Italy) that amplified the V3-V4 hypervariable ribosomal RNA region. Sequencing of the 16S rRNA gene V3- V4 region was performed using the Illumina MiSeq. Preliminary analyses were conducted on individual fecal samples compared to an internal population of healthy subjects (provided by BMR genomics) using Qiime2 tools. Shannon–Wiener index was used to calculate α-diversity and then the microbial biodiversity index (MBI) and Dysbiosis Index (DI). Mann–Whitney tests were performed to verify statistical differences in the α-diversity across AAG patients and healthy subjects.

Results: We enrolled 15 AAG patients with a mean age of ± 63 ± 11 years (9/15 females). OLGA 2 stage was reported in 10/15 patients. Sixty percent of the patients showed a MBI between 7.11 and 12.45, indicating that each sample contained phylogenetically similar species. The remaining patients have an index greater than 12.45 compared to the healthy population. More than half of the patients had dysbiosis (>0.082). The highest indices of dysbiosis were found in patients with a history of NET (n=3), gastric cancer (n=1), and previous HP- infection and OLGA 3 stage (n=1). Firmicutes, Bacteroidetes, and Proteobacteria were more frequent phyla found in the fecal samples, whereas Enterobacteriaceae and Streptococcaceae were the most common bacterial families (13/15, 87%). In particular, Klebsiella and Campylobacter pathogens genera were found in some samples. Streptococcus and Prevotella were the most abundant genera found in the salivary samples.

Conclusion: Patients with AAG were found to have a great proportion of Firmicutes and Bacteroidetes, which aligns with the literature (3,4). Moreover, a dominant of Proteobacteria, especially Enterobacteriaceae commonly associated with proinflammatory states, was found. (5) Our preliminary data showed a possible positive association between higher degrees of dysbiosis and a previous history of NET or gastric cancer.


HELICOBACTER PYLORI SEROPREVALENCE IN PATIENTS WITH AAG HELICOBACTER PYLORI NEGATIVE AT HISTOLOGY 

Introduction: For autoimmune atrophic gastritis (AAG) two pathogenetic models are proposed: a pure autoimmune disorder or gastric autoimmunity triggered by Helicobacter pylori (Hp) infection. In AAG, the diagnosis of Hp infection with conventional methods is challenging due to oxyntic mucosa atrophy, hypochlorhydria, and gradual Hp clearance. Formerly, Hp seropositivity in AAG with negative Hp histology was shown by Western blotting. A Hp multiplex serology assay allowing simultaneous detection of antibodies to several Hp proteins and virulence factors has not been used so far in sera of AAG pts to test for Hp exposure.

Aims & Methods: The aim was to assess seroreactivity against Hp proteins in AAG pts, Hp negative at histological evaluation of gastric biopsies and without history of Hp infection.
Single centre case-control study on 75 adults with histological AAG diagnosis, age 63 (18-88) yrs, F:M 2.4:1, parietal cell (PCA)-intrinsic factor autoantibodies (IFA) positivity in 81.3%-41.3%. AAG pts were compared with 2 control groups: 62 healthy stomach subjects (HS), age 65.5 (23-90) yrs, F:M 1.1:1, and 16 controls with Hp-positive antral non-atrophic gastritis (NAHp), age 59.5 (31-78) yrs, F:M 1.7:1. All 153 subjects had gastroscopy with biopsies, according to the updated Sydney system, for clinical suspicion of AAG (anaemia or dyspepsia) or AAG follow-up. Frozen sera (-20°C) were analysed by Hp multiplex serology assay. This assay is based on a glutathione-S-transferase (GST) capture immunosorbent assay combined with fluorescent bead technology measuring antibody responses to 13 Hp proteins (CagA, VacA, UreA, HP0875, NapA, HpaA, HyuA, HcpC, Cad, GroEl, HP0231, HP0305, HP1564). Median fluorescent intensity (MFI) values for each antigen were determined in a 1:1000 serum dilution. Seropositivity to individual antigens was defined as MFI above cut-off. Hp seropositivity was defined as being positive for >3 or more antigens.

Results: AAG pts showed a higher, but not significantly, Hp seropositivity than HS (n=16/21.3% vs n=6/9.7%, p=0.06), but a significantly lower seropositivity than NAHp (12/75%, p<0.0001). The number of participants positive to none of the Hp antigens was similar in AAG and HS (n=22/29.3% vs n=24/38.7%,p=0.25), and significantly higher than in NAHp (n=1/6.2%,p=0.05). The number of seroreactive antigens was significantly higher in AAG than in HS (mean±SEM 2.2±0.3 vs 1.4±0.2, p=0.04), and lower than in NAHp (5.4 ± 0.7, p<0.0001). Hp antigens seroreactive in >50% of the 16 Hp seropositive AAG pts included GroEL, NapA, CagA, HyuA, Catalase, HcpC, and HP1564; UreA and VacA were seropositive in 37.5%/16 seropositive AAG pts.
Severe corpus atrophy was significantly more frequent in the 22 AAG pts without any seroreactivity (0 Hp antigens) than in seropositives (p=0.019) suggesting more severe disease in pts never exposed to Hp. IFA positivity was nearly 2x in Hp seronegatives compared to seropositives (45.8% vs 25%, p=0.137) albeit not significant. An inverse relationship between anti-UreA and IFA titers was shown (Spearman’s rho -0.25 (95%CI -0.46 to -0.03), p=0.03), suggesting an opposite trend of Hp immunoreactivity and gastric autoimmunity.

Conclusion: By Hp multiplex serology, 30% of histologically Hp negative AAG pts had complete absence of seroreactivity, likely belonging to the pure AAG type. In contrast, 20% of AAG pts showed exposure to Hp, indicating that infection might have played a role in triggering gastric autoimmunity. The remaining 50% of AAG pts showed a weak seropositivity, probably belonging to a grey zone, not definitively categorizable by this approach.


HELICOBACTER PYLORI-RELATED GENES ARE DETECTABLE IN GASTRIC BIOPSIES OF A MINORITY OF PATIENTS WITH AUTOIMMUNE ATROPHIC GASTRITIS 

Introduction: Autoimmune atrophic gastritis (AAG) is an immune-mediated disorder characterized by corpus-restricted atrophy and pseudopyloric or intestinal metaplasia, associated with reduced hydrochloric acid and intrinsic factor production and heterogeneous clinical consequences. The aetiology of AAG is autoimmune, but the role of Helicobacter pylori (Hp) has been proposed, although not definitively proven. A possible antigenic crossreactivity with H+,K+-ATPase, the main autoantigen in AAG, has been reported and Hp seropositivity has been described in histologically Hp negative AAG. One study employed molecular biology techniques to characterize a cohort of AAG patients as definitively Hp naïve.

Aims & Methods: The aim was to assess the presence of Hp-related genes in corpus mucosa biopsies of pts with AAG and Hp-positive and negative ctr by using real-time PCR. Single-centre, experimental molecular biology study on 55 pts with histologically diagnosed AAG, of whom at histology 52 were Hp negative (age 61.5, range 28-88 yrs, 75% F, 96.2% parietal cell (PCA) and 44.2% intrinsic factor antibodies (IFA) positive), while 3 were Hp positive (age 74,69,33 yrs; 1 F; all 3 PCA and 1 IFA positive). Ctr were 4 pts who underwent gastroscopy for non-ulcer dyspepsia, 2 with Hp-positive superficial antral gastritis (positive ctr), and 2 with a healthy stomach (negative ctr). Hp serology (ELISA or multiplex) was available from all pts. DNA was extracted from formalin-fixed, paraffin-embedded (FFPE) tissue sections of corpus mucosa biopsies and real-time PCR was performed using specific probes for UreA, UreC, and CagA Hp related genes; 16sRNA and Beta2 microglobulin (B2M) specific probes were used as amplification ctr of bacterial and human DNA (real-time PCR cycle threshold (CT) >28<38).

Results: In 4(7.7%) of the 52 histologically Hp negative AAG pts, Hp-related genes were detected, in 4(7.7%) UreC, in 3(5.8%) UreA, and in 1(1.9%) CagA. All of them (3 F, aged 88,85,58,56 yrs) had positive Hp serology and PCA, only one was IFA-positive. The detectability of B2M and bacterial 16sRNA genes did not differ in UreC-positive or UreC-negative pts (B2M CT mean 29.6±1.2 for Ure-C positives vs 29.7±1.4 for Ure-C negatives, p=0.99; 16SrRNA gene CT mean 29.9±1.2 vs 29.4±1.2, p=0.27) indicating that the not-detectability of Hp-related genes was unrelated to reduced amounts of gastric bacterial or human DNA. Hp serology was positive in all 4 histologically Hp-negative AAG pts positive for UreC compared to 5/48(10.4%) UreC negative pts (p<0.0001) indicating previous exposure. PCA were present in all 4 UreC positive AAG pts compared to 46/48(95.8%) of UreC negatives (p=0.68). IFA positivity in UreC negatives was nearly 2x higher than that of UreC positives (45.8% vs 25%, p=0.42) without reaching significance. In 2/3 pts with histologically Hp-positive AAG, Hp-related genes could be detected; in the remaining patient, nor UreA, UreC neither CagA gene could be found (M, 69 yrs, no anemia, PCA-IFA-Hp serology positive).

Conclusion: In >90% of histologically Hp-negative and PCA or IFA positive AAG pts, Hp-related genes cannot be retrieved in the gastric mucosa. In 10% of these Hp-genes negative AAG pts, previous exposure to Hp can be testified by positive serology.
Hp-related genes can be detected in gastric biopsies in <10% of histologically Hp-negative AAG patients and positive Hp serology further confirms the role of Hp in this group. These findings show that primary, Hp naive AAG is the more common type, but in a subset of pts, AAG seems to be secondary to Hp infection.



HELICOBACTER PYLORI-RELATED GENES ARE NOT DETECTABLE IN GASTRIC MUCOSA OF PATIENTS WITH HISTOLOGICALLY HP NEGATIVE AUTOIMMUNE ATROPHIC GASTRITIS COMPLICATED WITH GASTRIC CANCER

Introduction: Chronic atrophic gastritis (CAG) is primarily caused by Helicobacter pylori (Hp) infection but also by autoimmune phenomena giving rise to autoimmune atrophic gastritis (AAG), whose hallmark is corpus-restricted atrophy sparing the antrum (unlike Hp infection causing extensive CAG). AAG triggered by Hp has been proposed, but diagnosis of Hp in this condition is difficult. Hp infection is one of the main risk factors for gastric cancer (GC), while the role of AAG in the onset of GC is still debated. Assessing the association of GC with AAG is thus challenging, as it requires the exclusion of Hp infection. Hence, investigating the presence of Hp-related genes in the gastric mucosa of histologically Hp negative AAG patients complicated by GC could be useful for accurately assessing the role of Hp in GC associated with AAG.

Aims & Methods: The aim was to assess the presence of Hp-related genes in corpus mucosa biopsies using Real-time and Digital PCR in AAG patients with GC and negative Hp at histology, along with Hp-positive and -negative controls.
Single-centre, experimental molecular biology study derived from 713 pts with histological diagnosis of CAG (2009-2022). Pts without corpus-restricted CAG (n=118) and with histological positivity for Hp (n=57) were excluded, resulting a source population of 538 AAG pts with negative Hp at histology. Out of these, 10 pts (80%F, age 69.5 (range 50-83) yrs) were diagnosed with gastric neoplastic lesions (GNL), including gastric cancer (GC) and high-grade intraepithelial neoplasia (HG-IEN). Real-time and Digital PCR were used to assess the presence of Hp-related genes in corpus mucosa biopsies of the 10 GNL-AAG pts and 2 Hp-positive non-atrophic gastritis pts (positive controls: 1 F,1 M, age 39, 68 yrs) and 2 subjects with a healthy stomach (negative controls: 1 F,1 M, age 22, 34 yrs). DNA was extracted from formalin-fixed, paraffin-embedded (FFPE) tissue sections of corpus mucosa biopsies and Real-time and Digital PCR were performed using specific probes for UreA, UreC, and CagA Hp-related genes. 16sRNA and Beta2 microglobulin specific probes were used as amplification ctr of bacterial and human DNA. Real-Time PCR gives a semiquantitative analysis, whereas Digital PCR measures the accurate copy numbers of Hp DNA.

Results: GNL were diagnosed in 3/10 pts at AAG diagnosis, while in 7 at follow-up (median 96, range 12-156 mos). GNL were frequently in the corpus (50%), less commonly at incisura angularis (30%) or antrum (20%), and consisted of 8 GC and 2 HG-IEN. None had family history of GC, all pts were parietal cell autoantibodies positive. ELISA Hp serology was negative in all 5/10 available sera. Hp-related genes were not detected in any of the GNL-AAG pts nor in negative controls, but UreA and UreC were found in both positive controls and CagA in one. 16sRNA gene was detected in GNL-AAG by Real-time(CT mean 26.0, SD 0.3) and Digital PCR (copies μl mean 1397,SD 348) in similar amounts as in positive controls (mean CT 25.7, SD 0.9, mean copies/μl 4977.5, SD 2185.7), indicating the detectability of bacterial genes in the extracted DNA.  

Conclusion: In FFPE corpus mucosa biopsies of pts with histologically Hp negative AAG and GC, specific Hp-related genes are detectable by nor Real-time neither Digital PCR. This result supports the idea that GC development cannot be excluded a priori in primary, Hp negative AAG, suggesting that Hp-unrelated cancerogenetic mechanisms may be involved and regular surveillance should be considered in primary AAG.


OCCURRENCE AND CHARACTERISTICS OF ENDOSCOPIC GASTRIC POLYPS IN PATIENTS WITH AUTOIMMUNE ATROPHIC GASTRITIS: A MULTICENTRIC CROSS-SECTIONAL STUDY (Sara Massironi (Italy), et al. ARIOSO) 

Introduction: Autoimmune atrophic gastritis (AAG) leads to significant changes in the gastric mucosa, including hypo-achlorhydria and increased gastrin (G) levels, providing proliferative stimuli on the gastric mucosa (1-5).

Aims & Methods: The aim of our study is to evaluate the occurrence and characteristics of gastric polyps in AAG patients across six tertiary centers in Italy. We conducted a multicentric, cross-sectional study from January to June 2023, prospectively enrolling consecutive patients diagnosed with AAG, from January 2000 to June 2023, who underwent at least one endoscopy. Data on demographics, clinical history, biochemical profiles, serological data, and endoscopic and histopathological findings were collected.

Results: Among 612 AAG patients (73.9% female, median age 66) followed up for a median of 4 (IQR 2-7.5) years, 222 (36.3%) had at least one gastric polyp. Non-endocrine polyps (214) were found in 162 patients, including 151 (70.5%) inflammatory, 29 (13.6%) adenomatous, 18 (8.4%) fundic gland polyps, 13 (6.1%) adenocarcinomas, and one MALT lymphoma. Additionally, 108 patients (48.6% of the population with polyps and 17.6% of the overall AAG patients) presented with gastric neuroendocrine neoplasms (gNENs), 48 of whom also had non-endocrine polyps. The median polyp size was 4 (IQR 2-7) mm. Older age, smoking prevalence, and higher levels of G and chromogranin A (CgA) were associated with polyp presence. No significant differences in OLGA/OLGIM stages or H. pylori status were noted between patients with and without polyps.

Conclusion: This study represents the largest multicentric cohort of AAG patients, highlighting the significant presence of gastric polyps, including gNENs and various non-endocrine types including a not negligible proportion of patients who showed gastric adenocarcinoma. These results emphasize the importance of proactive endoscopic monitoring and comprehensive histopathological evaluation in patients with AAG, to effectively identify and manage these different gastric lesions.


ASSESSING THE FREQUENCY OF TYPE I GASTRIC NEUROENDOCRINE NEOPLASMS IN AUTOIMMUNE ATROPHIC GASTRITIS: A MULTI-CENTER STUDY IN ITALY (Sara Massironi (Italy), et al. ARIOSO)

Introduction: In autoimmune atrophic gastritis (AAG), immune-mediated morpho-functional changes in gastric mucosa lead to hypo-achlorhydria and subsequent hypergastrinemia. This stimulates gastric enterochromaffin-like (ECL) cell proliferation, escalating the risk of type I gastric neuroendocrine neoplasms (gNENs). Yet, longitudinal studies on the AAG-type I gNENs association are still scanty.

Aims & Methods: Our study aims to assess in a multicentric cohort of AAG patients, the frequency and the characteristics of type I gNENs. We conducted a multicentric, cross-sectional study from January to June 2023, prospectively enrolling consecutive patients diagnosed with AAG, from January 2000 to June 2023, who underwent at least one endoscopy. Data on demographics, clinical history, biochemical profiles, serological data, and endoscopic and histopathological findings were collected.

Results: The study included 612 patients with AAG [444 (75.2%) female, median age 66 (IQR 54-73) years]. At enrollment, 355 (58.1%) patients had ECL cell hyperplasia. Over a median follow-up of 4 (IQR 2-7) years, and after a median number of two upper GI endoscopies per patient, and a median disease duration of 7 (IQR 3-8) years, 108 patients showed 125 gNENs, corresponding to an incidence rate of 0.051 person-years. All the gNENs were well-differentiated. In 22 (18%) cases Ki 67 was not available; of the remaining 103, 86 (68.8%) cases were G1, 17 (13.6%) were G2, all of which with a Ki-67 < 10%; no G3 lesions were observed. 119 (95.2%) gNENs were located in the body/fundus. The median size was 5 (IQR 3-10) mm. 79 (73.1%) patients underwent endoscopic removal, 10 (9.2%) gastrectomy, 12 (11.1%) somatostatin analog therapy due to multifocal/recurrent disease, and 7 (6.5%) were only monitored. Patients with AAG and gNENs had significantly higher gastrin levels compared to patients without gNENs [median 874 pg/mL (IQR 362.5-1335) vs 581.5 pg/mL (IQR 281.8-1071.5), p=0.014]. However, there were no significant differences in proton-pump inhibitor use, OLGA and OLGIM stages, H. pylori status, and notably, circulating chromogranin A levels. Conclusion: Type I gNENs are a relevant complication in patients with AAG. Elevated circulating gastrin levels are linked to their occurrence, with hypergastrinemia acting as a driver for abnormal proliferation of gastric ECL cells. Regular endoscopic surveillance and thorough histopathological examination are crucial in patients with AAG, serving as a key strategy for early diagnosis and treatment of gNENs.

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대한자가면역성위염연구회

주소 : 경기도 용인시 기흥구 중부대로 579, 508-23호 (구갈동, 강남대프라자)

대표전화 : 070-8080-0453  이메일 : autogastritis@gmail.com 


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