Impaired tryptophan metabolism in the gastrointestinal tract of patients with critical coronavirus disease 2019.

Introduction: Coronavirus disease 2019 (COVID-19) is still causing a global pandemic. But the mechanism of COVID-19 severity is not well elucidated. Materials and methods: We conducted two single-center observational studies of patients with COVID-19. In the first study, the enrolled patients were distinguished based on critical vs. non-critical COVID-19. We collected blood samples from the patients at admission to measure markers related to inflammation and thrombosis and stool samples to analyze the fecal microbiome, metabolome, and calprotectin level. In the second study, we collected ileum and colon tissue samples from patients with critical COVID-19 who required colonoscopy due to severe gastrointestinal symptoms and analyzed mucosal gene expression. Results: A total of 19 blood samples and 10 stool samples were collected. Interleukin (IL)-6 was the only serum inflammatory marker with significantly higher levels in the critical group than in the non-critical group. The fecal calprotectin level in the critical group was significantly higher than that in the non-critical group (P = 0.03), regardless of the presence of gastrointestinal symptoms. Stool metabolomic analysis showed that the level of indole-3-propionic acid, a ligand for aryl hydrocarbon receptor (AhR), was markedly decreased in the critical group compared to that in the non-critical group (P = 0.01). The expression of genes involved in tryptophan metabolism, including ACE2, AHR, CARD9, and IL22, was downregulated in the ileum of critical COVID-19 patients who required a colonoscopy. Discussion: Critical COVID-19 patients have gastrointestinal inflammation potentially caused by impaired tryptophan metabolism in the small intestine due to decreased expression of genes involved in tryptophan metabolism.

Extensive mucosal sloughing of the small intestine and colon in a patient with severe COVID-19.

Patients with coronavirus disease 2019 (COVID-19) primarily cause respiratory symptoms. However, gastrointestinal (GI) symptoms can also occur. The endoscopic characteristics of the GI tract in COVID-19 patients remain unclear. We herein report a 62-year-old male with severe COVID-19 who needed multidisciplinary treatment, including extracorporeal membrane oxygenation (ECMO). Despite the improvement in his respiratory status, GI bleeding developed. Capsule endoscopy and colonoscopy revealed extensive mucosal sloughing in the lower intestinal tract. Additionally, we performed a comprehensive analysis of the mRNA expression levels of various proinflammatory cytokines in the intestinal mucosal tissues. The results suggested a significant elevation of IL-6, which could be involved in the pathophysiology of the GI involvement in COVID-19. Further investigation with more clinical data, including endoscopic findings and molecular analyses, will contribute to a comprehensive understanding of COVID-19-associated GI injury.

The characteristics of gastrointestinal symptoms in patients with severe COVID-19: a systematic review and meta-analysis.

Although primarily a respiratory illness, several studies have shown that COVID-19 causes elevation of liver enzymes and various gastrointestinal (GI) symptoms. The aim of this study was to undertake a systematic review and meta-analysis to determine whether the presence of gastrointestinal (GI) symptoms contributed toward COVID-19 severity, and identify the GI symptoms characteristic of severe COVID-19. We conducted a literature search of PubMed from December 1, 2019, to June 30, 2020, and identified all reports with GI symptoms reported. A meta-analysis comparing the severity of COVID-19 with the presence of liver enzyme elevation and GI symptoms was performed using RevMan version 5.4. Pooled data from 15,305 unique reverse transcriptase-polymerase chain reaction positive COVID-19 patients from 44 studies were analyzed. We found that the severe COVID-19 patients significantly had abdominal pain compared to the non-severe COVID-19 patients (OR = 2.70, 95% CI 1.17-6.27, Z = 2.32, p = 0.02, I2 = 0%) by analyzed 609 patients of 4 studies who reported both abdominal pain and COVID-19 severity. However, there was no significant difference in the incidence of diarrhea, nausea, or vomiting between the two groups. Thus, this systematic review and meta-analysis demonstrated that abdominal pain could be characteristic of severe COVID-19 infections. Compared with other viral infections that primarily infect the respiratory system, patients with COVID-19 have a slightly lower frequency of diarrheal symptoms with abdominal pain. However, to confirm this, further studies with COVID-19 patients across various countries and ethnicities are required.

Expert Opinions on the Current Therapeutic Management of Inflammatory Bowel Disease during the COVID-19 Pandemic: Japan IBD COVID-19 Taskforce, Intractable Diseases, the Health and Labor Sciences Research.

BACKGROUND: The COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has emerged as a dramatic challenge for all healthcare systems worldwide. This outbreak immediately affected gastroenterologists as well as global physicians worldwide because COVID-19 can be associated with not only triggering respiratory inflammation but also gastrointestinal (GI) inflammation based on the mechanism by which SARS-CoV-2 enters cells via its receptor the angiotensin-converting enzyme 2, which is expressed on GI cells. However, the comorbidity spectrum of digestive system in patients with COVID-19 remains unknown. Because the inflammatory bowel disease (IBD) management involves treating uncontrolled inflammation with immune-based therapies, physicians, and patients have great concern about whether IBD patients are more susceptible to SARS-CoV-2 infection and have worsened disease courses. SUMMARY: It is necessary to precisely ascertain the risk of SARS-CoV-2 infection and the COVID-19 severity in IBD patients and to acknowledge the IBD management during the COVID-19 pandemic with clinically reliable information from COVID-19 cohorts and IBD experts' opinions. In this review, we highlight clinical questions regarding IBD management during the COVID-19 pandemic and make comments corresponding to each question based on recent publications. Key Messages: We propose that there is (1) no evidence that IBD itself increases the risk of SARS-CoV-2 infection, (2) to basically prioritize the control of disease activity of IBD, (3) no need for physicians to suddenly discontinue immunomodulatory or biologic therapy in patients with quiescent IBD, and (4) a need for careful observation of elderly (>60 years old) and IBD patients receiving corticosteroid treatment during the COVID-19 pandemic.