Increased prevalence of irritable bowel syndrome in patients with bronchial asthma

Appendix removal affects the subsequent cancer risk in Asian adults: A territory-wide population-based cohort study

Human appendix is critical for the maintenance of intestinal homeostasis. Appendicectomy has been the optimal treatment of acute appendicitis, yet the cancer incidence after appendix removal remains unclear. In this territory-wide retrospective cohort study, adult participants who underwent appendicectomy from 2000 to 2018 were retrieved from a population database (n = 43,983), while matched reference participants were retrieved as controls (n = 85,853). After appendicectomy, the overall cancer risk was significantly increased (subdistribution hazard ratio (SHR) = 1.124) compared to the non-appendicectomy group. Appendicectomy-treated males had higher cancer risk than males without appendicectomy (SHR = 1.197), while such difference was not observed in female participants. Significant increase in cancer risk was also observed in elder participants (age >60) with appendicectomy (SHR = 1.390). Appendicectomy was positively correlated with the risk of digestive tract and respiratory cancers including colon (SHR = 1.440), pancreas (SHR = 1.930), and trachea, bronchus, and lung (SHR = 1.394). In contrast, the risk of liver cancer was markedly decreased after appendicectomy (SHR = 0.713). In conclusion, we reported the association of appendicectomy with subsequent cancer incidence. These findings highlight the potential complication after appendix removal and the necessity of post-operative management to monitor and prevent long-term adverse events.

Irritable bowel syndrome: When food is a pain in the gut

Irritable bowel syndrome (IBS) is a chronic gastrointestinal condition associated with altered bowel habits and recurrent abdominal pain, often triggered by food intake. Current treatments focus on improving stool pattern, but effective treatments for pain in IBS are still lacking due to our limited understanding of pathophysiological mechanisms. Visceral hypersensitivity (VHS), or abnormal visceral pain perception, underlies abdominal pain development in IBS, and mast cell activation has been shown to play an important role in the development of VHS. Our work recently revealed that abdominal pain in response to food intake is induced by the sensitization of colonic pain-sensing neurons by histamine produced by activated mast cells following a local IgE response to food. In this review, we summarize the current knowledge on abdominal pain and VHS pathophysiology in IBS, we outline the work leading to the discovery of the role of histamine in abdominal pain, and we introduce antihistamines as a novel treatment option to manage chronic abdominal pain in patients with IBS.

Multimorbidity of Allergic Diseases Is Associated With Functional Gastrointestinal Disorders in a Young Japanese Population

Background/Aims

Although certain allergic diseases have been reported to be associated with the prevalence of functional dyspepsia (FD) and irritable bowel syndrome (IBS), it is unclear whether the presence of multiple allergic diseases further increases the prevalence of FD and IBS. The aim of this study is to determine this issue in young people.

Methods

A cohort of 8923 Japanese university students was enrolled and diagnoses of FD and IBS were confirmed using Rome III criteria. Allergic disorders diagnosed at medical institutions were obtained by means of a self-administered questionnaire.

Results

The prevalence of FD, IBS, and their overlap was found to be 1.9%, 6.5%, and 1.1%, respectively. Pollen allergy was independently positively correlated with FD, IBS, and overlap of FD and IBS. Allergic rhinitis was positively linked to IBS. Drug allergy was positively associated with FD. The presence of multiple allergic diseases was positively correlated with FD and IBS (FD: adjusted OR for 2 allergic diseases: 1.95 [95% CI, 1.24-2.98], P for trend = 0.003; and IBS: adjusted OR for 1 allergic disease: 1.40 [95% CI, 1.15-1.69], 2 allergic diseases 1.47 [95% CI, 1.12-1.91], and 3 or more allergic diseases: 2.22 [95% CI, 1.45-3.28], P for trend = 0.001). Additionally, the concomitant existence of multiple allergic diseases was also demonstrated to have a trend that correlated with the overlap of FD and IBS (P for trend = 0.018).

Conclusion

Allergic disease multimorbidity is positively correlated with the prevalence of FD and IBS in a young population.

Promising dawn in the management of pulmonary hypertension: The mystery veil of gut microbiota

The gut microbiota is a complex community of microorganisms inhabiting the intestinal tract, which plays a vital role in human health. It is intricately involved in the metabolism, and it also affects diverse physiological processes. The gut-lung axis is a bidirectional pathway between the gastrointestinal tract and the lungs. Recent research has shown that the gut microbiome plays a crucial role in immune response regulation in the lungs and the development of lung diseases. In this review, we present the interrelated factors concerning gut microbiota and the associated metabolites in pulmonary hypertension (PH), a lethal disease characterized by elevated pulmonary vascular pressure and resistance. Our research team explored the role of gut-microbiota-derived metabolites in cardiovascular diseases and established the correlation between metabolites such as putrescine, succinate, trimethylamine N-oxide (TMAO), and N, N, N-trimethyl-5-aminovaleric acid with the diseases. Furthermore, we found that specific metabolites, such as TMAO and betaine, have significant clinical value in PH, suggesting their potential as biomarkers in disease management. In detailing the interplay between the gut microbiota, their metabolites, and PH, we underscored the potential therapeutic approaches modulating this microbiota. Ultimately, we endeavor to alleviate the substantial socioeconomic burden associated with this disease. This review presents a unique exploratory analysis of the link between gut microbiota and PH, intending to propel further investigations in the gut-lung axis.

The microbiome: an integral player in immune homeostasis and inflammation in the respiratory tract

The last decade of microbiome research has highlighted its fundamental role in systemic immune and metabolic homeostasis. The microbiome plays a prominent role during gestation and into early life, when maternal lifestyle factors shape immune development of the newborn. Breast milk further shapes gut colonization, supporting the development of tolerance to commensal bacteria and harmless antigens while preventing outgrowth of pathogens. Environmental microbial and lifestyle factors that disrupt this process can dysregulate immune homeostasis, predisposing infants to atopic disease and childhood asthma. In health, the low-biomass lung microbiome, together with inhaled environmental microbial constituents, establishes the immunological set point that is necessary to maintain pulmonary immune defense. However, in disease perturbations to immunological and physiological processes allow the upper respiratory tract to act as a reservoir of pathogenic bacteria, which can colonize the diseased lung and cause severe inflammation. Studying these host-microbe interactions in respiratory diseases holds great promise to stratify patients for suitable treatment regimens and biomarker discovery to predict disease progression. Preclinical studies show that commensal gut microbes are in a constant flux of cell division and death, releasing microbial constituents, metabolic by-products, and vesicles that shape the immune system and can protect against respiratory diseases. The next major advances may come from testing and utilizing these microbial factors for clinical benefit and exploiting the predictive power of the microbiome by employing multiomics analysis approaches.

Lung microbiome: new insights into the pathogenesis of respiratory diseases

The lungs were long thought to be sterile until technical advances uncovered the presence of the lung microbial community. The microbiome of healthy lungs is mainly derived from the upper respiratory tract (URT) microbiome but also has its own characteristic flora. The selection mechanisms in the lung, including clearance by coughing, pulmonary macrophages, the oscillation of respiratory cilia, and bacterial inhibition by alveolar surfactant, keep the microbiome transient and mobile, which is different from the microbiome in other organs. The pulmonary bacteriome has been intensively studied recently, but relatively little research has focused on the mycobiome and virome. This up-to-date review retrospectively summarizes the lung microbiome's history, composition, and function. We focus on the interaction of the lung microbiome with the oropharynx and gut microbiome and emphasize the role it plays in the innate and adaptive immune responses. More importantly, we focus on multiple respiratory diseases, including asthma, chronic obstructive pulmonary disease (COPD), fibrosis, bronchiectasis, and pneumonia. The impact of the lung microbiome on coronavirus disease 2019 (COVID-19) and lung cancer has also been comprehensively studied. Furthermore, by summarizing the therapeutic potential of the lung microbiome in lung diseases and examining the shortcomings of the field, we propose an outlook of the direction of lung microbiome research.

Development of an experimental model for liver abscess induction in Holstein steers using an acidotic diet challenge and bacterial inoculation

Holstein steers (n = 40; initial BW = 84.9 ± 7.1 kg) were used to study the genesis of liver abscesses (LA) using an acidotic diet challenge with or without intraruminal bacterial inoculation. Steers were housed in individual pens inside a barn and randomly assigned to one of three treatments: (1) low-starch control diet comprised primarily of dry-rolled corn and wet corn gluten feed (CON); (2) high-starch acidotic diet with steam-flaked corn (AD); or (3) acidotic diet plus intraruminal inoculation with Fusobacterium necrophorum subsp. necrophorum (9.8 × 108 colony forming units [CFU]/mL), Trueperella pyogenes (3.91 × 109 CFU/mL), and Salmonella enterica serovar Lubbock (3.07 × 108 CFU/mL), previously isolated from LA (ADB). Steers in AD and ADB were fed the acidotic diet for 3 d followed by 2 d of the CON diet, and this cycle was repeated four times. On day 23, ADB steers were intraruminally inoculated with the bacteria. At necropsy, gross pathology of livers, lungs, rumens, and colons was noted. Continuous data were analyzed via mixed models as repeated measures over time with individual steer as the experimental unit. Mixed models were also used to determine the difference in prevalence of necropsy scores among treatments. Ruminal pH decreased in AD and ADB steers during each acidotic diet cycle (P ≤ 0.05). LA prevalence was 42.9% (6 of 14) in ADB vs. 0% in AD or CON treatments (P < 0.01). Ruminal damage was 51.1% greater in ADB than in AD (P ≤ 0.04). Culture of LA determined that 100% of the abscesses contained F. necrophorum subsp. necrophorum, 0% contained T. pyogenes, 50% contained Salmonella, and 50% contained a combination of F. necrophorum subsp. necrophorum and Salmonella. The F. necrophorum subsp. necrophorum was clonally identical to the strain used for the bacterial inoculation based on phylogenetic analysis of the whole genome. This experimental model successfully induced rumenitis and LA in Holstein steers and confirms the central dogma of LA pathogenesis that acidosis and rumenitis lead to the entry of F. necrophorum into the liver to cause abscesses. Our findings suggest that an acidotic diet, in conjunction with intraruminal bacterial inoculation, is a viable model to induce LA. Further research is needed to determine the repeatability of this model, and a major application of the model will be in evaluations of novel interventions to prevent LA.

Gut microbial dysbiosis occurring during pulmonary fungal infection in rats is linked to inflammation and depends on healthy microbiota composition

While the effect of gut microbiota and/or inflammation on a distant body site, including the lungs (gut-lung axis), has been well characterized, data about the influence of lung microbiota and lung inflammation on gut homeostasis (lung-gut axis) are scarce. Using a well-characterized model of pulmonary infection with the fungus Aspergillus fumigatus, we investigated alterations in the lung and gut microbiota by next-generation sequencing of the V3-V4 regions of total bacterial DNA. Pulmonary inflammation due to the fungus A. fumigatus caused bacterial dysbiosis in both lungs and gut, but with different characteristics. While increased alpha diversity and unchanged bacterial composition were noted in the lungs, dysbiosis in the gut was characterized by decreased alpha diversity indices and modified bacterial composition. The altered homeostasis in the lungs allows the immigration of new bacterial species of which 41.8% were found in the feces, indicating that some degree of bacterial migration from the gut to the lungs occurs. On the contrary, the dysbiosis occurring in the gut during pulmonary infection was a consequence of the local activity of the immune system. In addition, the alteration of gut microbiota in response to pulmonary infection depends on the bacterial composition before infection, as no changes in gut bacterial microbiota were detected in a rat strain with diverse gut bacteria. The data presented support the existence of the lung-gut axis and provide additional insight into this mechanism. IMPORTANCE Data regarding the impact of lung inflammation and lung microbiota on GIT are scarce, and the mechanisms of this interaction are still unknown. Using a well-characterized model of pulmonary infection caused by the opportunistic fungus Aspergillus fumigatus, we observed bacterial dysbiosis in both the lungs and gut that supports the existence of the lung-gut axis.

Disorders of gut-brain interaction in post-acute COVID-19 syndrome

The novel coronavirus SARS-CoV-2 is responsible for the devastating pandemic which has caused more than 5 million deaths across the world until today. Apart from causing acute respiratory illness and multiorgan dysfunction, there can be long-term multiorgan sequalae after recovery, which is termed 'long COVID-19' or 'post-acute COVID-19 syndrome'. Little is known about long-term gastrointestinal (GI) consequences, occurrence of post-infection functional gastrointestinal disorders and impact the virus may have on overall intestinal health. In this review, we put forth the various mechanisms which may lead to this entity and possible ways to diagnose and manage this disorder. Hence, making physicians aware of this spectrum of disease is of utmost importance in the present pandemic and this review will help clinicians understand and suspect the occurrence of functional GI disease post recovery from COVID-19 and manage it accordingly, avoiding unnecessary misconceptions and delay in treatment.

Pectin alleviates the pulmonary inflammatory response induced by PM2.5 from a pig house by modulating intestinal microbiota

This study aimed to investigate whether dietary fiber pectin can alleviate PM_2.5-induced pulmonary inflammation and the potential mechanism. PM_2.5 samples were collected from a nursery pig house. The mice were divided into three groups: the control group, PM_2.5 group and PM_2.5 + pectin group. The mice in the PM_2.5 group were intratracheally instilled with PM_2.5 suspension twice a week for four consecutive weeks, and those in the PM_2.5 + pectin group were subject to the same PM_2.5 exposure, but fed with a basal diet supplemented with 5% pectin. The results showed that body weight and feed intake were not different among the treatments (p > 0.05). However, supplementation with pectin relieved PM_2.5-induced pulmonary inflammation, presenting as slightly restored lung morphology, decreased mRNA expression levels of IL-1β, IL-6 and IL-17 in the lung, decreased MPO content in bronchoalveolar lavage fluid (BLAF), and even decreased protein levels of IL-1β and IL-6 in the serum (p < 0.05). Dietary pectin altered the composition of the intestinal microbiota, increasing the relative abundance of Bacteroidetes and decreasing the ratio of Firmicutes/Bacteroidetes. At the genus level, short-chain fatty acid (SCFA)-producing bacteria, such as Bacteroides, Anaerotruncus, Prevotella 2, Parabacteroides, Ruminococcus 2 and Butyricimonas, were enriched in the PM_2.5 +pectin group. Accordingly, dietary pectin increased the concentrations of SCFAs, including acetate, propionate, butyrate and valerate, in mice. In conclusion, dietary fermentable fiber pectin can relieve PM_2.5-induced pulmonary inflammation via alteration of intestinal microbiota composition and SCFA production. This study provides a new insight into reducing the health risk associated with PM_2.5 exposure.

The gut-lung axis: Mendelian randomization identifies a causal association between inflammatory bowel disease and interstitial lung disease

BACKGROUND

Previous studies have suggested the association between interstitial lung disease (ILD) and inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC).

OBJECTIVES

To examine the potential bidirectional causal relationship between IBD and ILD using the Mendelian randomization (MR) method.

METHODS

We obtained the data from the genome-wide association studies (GWASs) in European individuals for IBD (25,042 cases and 34,915 controls) and ILD (21,806 cases and 196,986 controls) from the IEU GWAS database. We screened for instrumental variables based on the three assumptions of MR. The two-sample bidirectional MR analysis was performed using the inverse-variance weighted method and multiple sensitivity analyses.

RESULTS

Genetic liability to IBD was significantly associated with an increased ILD risk (odds ratio (OR) = 1.20, 95% confidence interval (CI) = 1.17-1.24, p = 3.67E-33). When considering the IBD subtypes, ILD risk was associated with genetic liability to both CD (OR = 1.14, 95% CI = 1.10-1.17, p = 1.91E-17) and UC (OR = 1.16, 95% CI = 1.12-1.21, p = 3.51E-13). There was weak evidence for the effect of genetic liability to ILD on IBD (OR = 1.32, 95% CI = 0.99-1.76, p = 0.062), CD (OR = 1.25, 95% CI = 1.00-1.55, p = 0.046), and UC (OR = 1.47, 95%CI = 1.01-2.14, p = 0.046).

CONCLUSION

The results indicate a strong causal effect of IBD (including CD and UC) on ILD.

Gastrointestinal Manifestations of SARS-CoV-2: Transmission, Pathogenesis, Immunomodulation, Microflora Dysbiosis, and Clinical Implications

The clinical manifestation of COVID-19, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), in the respiratory system of humans is widely recognized. There is increasing evidence suggesting that SARS-CoV-2 possesses the capability to invade the gastrointestinal (GI) system, leading to the manifestation of symptoms such as vomiting, diarrhea, abdominal pain, and GI lesions. These symptoms subsequently contribute to the development of gastroenteritis and inflammatory bowel disease (IBD). Nevertheless, the pathophysiological mechanisms linking these GI symptoms to SARS-CoV-2 infection remain unelucidated. During infection, SARS-CoV-2 binds to angiotensin-converting enzyme 2 and other host proteases in the GI tract during the infection, possibly causing GI symptoms by damaging the intestinal barrier and stimulating inflammatory factor production, respectively. The symptoms of COVID-19-induced GI infection and IBD include intestinal inflammation, mucosal hyperpermeability, bacterial overgrowth, dysbiosis, and changes in blood and fecal metabolomics. Deciphering the pathogenesis of COVID-19 and understanding its exacerbation may provide insights into disease prognosis and pave the way for the discovery of potential novel targets for disease prevention or treatment. Besides the usual transmission routes, SARS-CoV-2 can also be transmitted via the feces of an infected person. Hence, it is crucial to implement preventive and control measures in order to mitigate the fecal-to-oral transmission of SARS-CoV-2. Within this context, the identification and diagnosis of GI tract symptoms during these infections assume significance as they facilitate early detection of the disease and the development of targeted therapeutics. The present review discusses the receptors, pathogenesis, and transmission of SARS-CoV-2, with a particular focus on the induction of gut immune responses, the influence of gut microbes, and potential therapeutic targets against COVID-19-induced GI infection and IBD.

Dietary intervention with functional foods modulating gut microbiota for improving the efficacy of COVID-19 vaccines

Dysbiosis of the gut microbiota with aging contributes to a reduction in important cross-feeding bacterial reactions in the gut and immunosenescence, which could contribute to a decrease in vaccine efficacy. Fever, cough, and fatigue are the main signs of coronavirus disease 2019 (COVID-19); however, some patients with COVID-19 present with gastrointestinal symptoms. COVID-19 vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is one of the best measures to reduce SARS-CoV-2 infection rates and the severity of COVID-19. The immunogenicity of COVID-19 vaccines is influenced by the composition of the gut microbiota, and the immune response to COVID-19 vaccines decreases with age. In this review, we discuss gut microbiota dysbiosis and immunosenescence in the older adults, the role of gut microbiota in improving the efficacy of COVID-19 vaccines, and dietary interventions to improve the efficacy of COVID-19 vaccines in the older adults.

Gastrointestinal consequences of lipopolysaccharide-induced lung inflammation

BACKGROUND

Respiratory inflammation is the body's response to lung infection, trauma or hypersensitivity and is often accompanied by comorbidities, including gastrointestinal (GI) symptoms. Why respiratory inflammation is accompanied by GI dysfunction remains unclear. Here, we investigate the effect of lipopolysaccharide (LPS)-induced lung inflammation on intestinal barrier integrity, tight-junctions, enteric neurons and inflammatory marker expression.

METHODS

Female C57bl/6 mice (6-8 weeks) were intratracheally administered LPS (5 µg) or sterile saline, and assessed after either 24 or 72 h. Total and differential cell counts in bronchoalveolar lavage fluid (BALF) were used to evaluate lung inflammation. Intestinal barrier integrity was assessed via cross sectional immunohistochemistry of tight junction markers claudin-1, claudin-4 and EpCAM. Changes in the enteric nervous system (ENS) and inflammation in the intestine were quantified immunohistochemically using neuronal markers Hu + and nNOS, glial markers GFAP and S100β and pan leukocyte marker CD45.

RESULTS

Intratracheal LPS significantly increased the number of neutrophils in BALF at 24 and 72 h. These changes were associated with an increase in CD45 + cells in the ileal mucosa at 24 and 72 h, increased goblet cell expression at 24 h, and increased expression of EpCAM at 72 h. LPS had no effect on the expression of GFAP, S100β, nor the number of Hu + neurons or proportion of nNOS neurons in the myenteric plexus.

CONCLUSIONS

Intratracheal LPS administration induces inflammation in the ileum that is associated with enhanced expression of EpCAM, decreased claudin-4 expression and increased goblet cell density, these changes may contribute to systemic inflammation that is known to accompany many inflammatory diseases of the lung.

Gastrointestinal microbiota: A predictor of COVID-19 severity?

Coronavirus disease 2019 (COVID-19), caused by a severe acute respiratory syndrome coronavirus 2 infection, has raised serious concerns worldwide over the past 3 years. The severity and clinical course of COVID-19 depends on many factors (e.g., associated comorbidities, age, etc) and may have various clinical and imaging findings, which raises management concerns. Gut microbiota composition is known to influence respiratory disease, and respiratory viral infection can also influence gut microbiota. Gut and lung microbiota and their relationship (gut-lung axis) can act as modulators of inflammation. Modulating the intestinal microbiota, by improving its composition and diversity through nutraceutical agents, can have a positive impact in the prophylaxis/treatment of COVID-19.

Upregulation of claudin‑4 by Chinese traditional medicine Shenfu attenuates lung tissue damage by acute lung injury aggravated by acute gastrointestinal injury

CONTEXT

Many studies have explored new methods to cure acute lung injury (ALI); however, none of those methods could significantly change the high mortality rate of ALI. Shenfu is a Chinese traditional medicine that might be effective against ALI.

OBJECTIVE

Our study explores the therapeutic potential of Shenfu in ALI.

MATERIALS AND METHODS

Male C57BL/6 mice were assigned to control, lipopolysaccharide (LPS) (500 µg/100 μL per mouse), and LPS + Shenfu (30 mL/kg) groups. Shenfu (10 µL/mL) was added to LPS (10 µg/mL) treated MLE-12 cells for 48 h in vitro. Male C57BL/6 mice were divided into four groups: LPS, LPS + 3% dextran sulphate sodium (DSS), 3% DSS + Shenfu, and LPS + 3% DSS + Shenfu.

RESULTS

Compared with the ALI group, Shenfu reduced wet/dry weight ratio (19.8%, 36.2%), and reduced the IL-2 (40.9%, 61.6%), IFN-γ (43.5%, 53.3%) TNF-α (54.1%, 42.1%), IL-6 (54.8%,70%), and IL-1β (39.9%, 65.1%), reduced serum uric acid (18.8%, 48.7%) and creatinine (17.4%, 41.1%). Moreover, Shenfu enhanced cell viability (17.2%, 59.9%) and inhibited cell apoptosis (63.0%) and p38/ERK phosphorylation in in vitro cultured epithelial cells with LPS stimulation. Mechanistically, Shenfu mediated the protective effect by upregulating claudin-4 expression. In addition, Shenfu could protect against both lung and intestinal epithelial damage in acute gastrointestinal injury-exacerbated ALI.

DISCUSSION AND CONCLUSIONS

Taken together, the results revealed the therapeutic effect and the underlying mechanism of Shenfu injection in an ALI in mouse model, indicating its clinical potential to treat patients with ALI.

Crosstalk between Body Microbiota and the Regulation of Immunity

The microbiome corresponds to the genetic component of microorganisms (archaea, bacteria, phages, viruses, fungi, and protozoa) that coexist with an individual. During the last two decades, research on this topic has become massive demonstrating that in both homeostasis and disease, the microbiome plays an important role, and in some cases, a decisive one. To date, microbiota have been identified at different body locations, such as the eyes, lung, gastrointestinal and genitourinary tracts, and skin, and technological advances have permitted the taxonomic characterization of resident species and their metabolites, in addition to the cellular and molecular components of the host that maintain a crosstalk with local microorganisms. Here, we summarize recent studies regarding microbiota residing in different zones of the body and their relationship with the immune system. We emphasize the immune components underlying pathological conditions and how they interact with local (and distant) microbiota.

Irritable bowel syndrome is strongly associated with the primary and idiopathic mast cell disorders

BACKGROUND

Mounting evidence supports a mechanistic association between irritable bowel syndrome (IBS) symptoms and mast cell hyperactivity. Yet, association between IBS and mast cell disorders (MCDs) has not been studied. We examined this association using two large databases and verified with manual chart review.

METHODS

The IBM Watson Health Explorys database (Somers, NY), an aggregate of electronic health record (EHR) data from over two dozen US healthcare systems, and Epic's SlicerDicer tool, a self-service tool containing de-identified data from the Epic EHR, were used to identify patients with IBS and MCDs. Patients with organic gastrointestinal disease or diseases associated with secondary mast cell hyperproliferation were excluded. Results were verified with manual chart review from two academic centers.

KEY RESULTS

Up to 4% of IBS patients had a comorbid MCD. IBS was strongly associated with all MCDs. The strongest association was between IBS and mast cell activation syndrome (OR 16.3; 95% CI 13.1-20.3). Odds ratios for IBS+urticaria, IBS+idiopathic urticaria, IBS+non-malignant mastocytosis, and IBS+mast cell malignancy ranged from 4.5 to 9.9. Patients from each of these overlap cohorts were predominantly female, and the overlap occurred with all IBS subtypes. Thorough endoscopic evaluation and comorbid mood disorders and migraines are more common in the overlap cohorts than in IBS alone.

CONCLUSIONS/INFERENCES

In a large US database encompassing >53 million patients over >20 years, patients with IBS are at least 4 times more likely to have a MCD than the general population. Further study of mast cell involvement in the pathogenesis of IBS is warranted.

Microbiota in health and diseases

The role of microbiota in health and diseases is being highlighted by numerous studies since its discovery. Depending on the localized regions, microbiota can be classified into gut, oral, respiratory, and skin microbiota. The microbial communities are in symbiosis with the host, contributing to homeostasis and regulating immune function. However, microbiota dysbiosis can lead to dysregulation of bodily functions and diseases including cardiovascular diseases (CVDs), cancers, respiratory diseases, etc. In this review, we discuss the current knowledge of how microbiota links to host health or pathogenesis. We first summarize the research of microbiota in healthy conditions, including the gut-brain axis, colonization resistance and immune modulation. Then, we highlight the pathogenesis of microbiota dysbiosis in disease development and progression, primarily associated with dysregulation of community composition, modulation of host immune response, and induction of chronic inflammation. Finally, we introduce the clinical approaches that utilize microbiota for disease treatment, such as microbiota modulation and fecal microbial transplantation.

Emerging trends and hotspot in gut-lung axis research from 2011 to 2021: a bibliometrics analysis

Background

Increasing attention has been paid to the potential relationship between gut and lung. The bacterial dysbiosis in respiratory tract and intestinal tract is related to inflammatory response and the progress of lung diseases, and the pulmonary diseases could be improved by regulating the intestinal microbiome. This study aims to generate the knowledge map to identify major the research hotspots and frontier areas in the field of gut–lung axis.

Materials and methods

Publications related to the gut–lung axis from 2011 to 2021 were identified from the Web of Science Core Collection. CiteSpace 5.7.R2 software was used to analyze the publication years, journals, countries, institutions, and authors. Reference co-citation network has been plotted, and the keywords were used to analyze the research hotspots and trends.

Results

A total of 3315 publications were retrieved and the number of publications per year increased over time. Our results showed that Plos One (91 articles) was the most active journal and The United States (1035 articles) published the most articles. We also observed the leading institution was the University of Michigan (48 articles) and Huffnagle Gary B, Dickson Robert P and Hansbro Philip M, who have made outstanding contributions in this field.

Conclusion

The Inflammation, Infection and Disease were the hotspots, and the regulation of intestinal flora to improve the efficacy of immunotherapy in lung cancer was the research frontier. The research has implications for researchers engaged in gut–lung axis and its associated fields.

Smoking has disruptive effects on the small bowel luminal microbiome

Tobacco use is the leading preventable cause of cancer, and affects the respiratory, oral, fecal, and duodenal mucosa-associated microbiota. However, the effects of smoking on the duodenal luminal microbiome have not been studied directly. We aimed to compare the duodenal luminal microbiome in never-smokers, current smokers, and ex-smokers who quit ≥ 10 years ago. In a cross-sectional study, current smokers (CS, n = 24) were identified and matched to never-smokers (NS, n = 27) and ex-smokers (XS, n = 27) by age (± 5 years), body mass index (BMI, ± 3 kg/m²), and sex. Current antibiotic users were excluded. The duodenal luminal microbiome was analysed in 1 aspirate sample per subject by 16S rRNA gene sequencing. Relative abundances (RA) of families associated with increased duodenal microbial diversity, Prevotellaceae, Neisseriaceae, and Porphyromonadaceae, were significantly lower in CS vs. NS. This was driven by lower RA of unknown Prevotella and Porphyromonas species, and Neisseria subflava and N. cinerea, in CS. In contrast, RA of Enterobacteriaceae and Lactobacillaceae (associated with decreased diversity), were significantly higher in CS, due to higher RA of Escherichia-Shigella, Klebsiella and Lactobacillus species. Many of these changes were absent or less pronounced in XS, who exhibited a duodenal luminal microbiome more similar to NS. RA of taxa previously found to be increased in the oral and respiratory microbiota of smokers were also higher in the duodenal luminal microbiome, including Bulledia extructa and an unknown Filifactor species. In conclusion, smoking is associated with an altered duodenal luminal microbiome. However, ex-smokers have a duodenal luminal microbiome that is similar to never-smokers.

Asthma and the risk of gastrointestinal disorders: a Mendelian randomization study

BACKGROUND

The question of whether asthma is causally related to gastrointestinal disorders remained unanswered so far. Thus, this study investigated whether there is such a relation and whether the time of onset of asthma plays a role in the occurrence of the following gastrointestinal disorders: peptic ulcer disease (PUD), gastroesophageal reflux disease (GORD), irritable bowel syndrome (IBS), and inflammatory bowel disease (IBD) including the distinction between Crohn's disease (CD) and ulcerative colitis (UC).

METHODS

Using summary data of genome-wide association studies (GWASs), we ran Mendelian randomization analyses based on up to 456,327 European participants. Outlier assessment, a series of sensitivity analyses and validation of IBD results in a second GWAS were performed to confirm the results.

RESULTS

Presented ORs represent the average change in the outcome per 2.72-fold increase in the prevalence of the exposure. Genetically predicted childhood-onset asthma was positively associated with PUD, GORD, and IBS with similar odds ratios near 1.003 and adjusted P-values from 0.007 (GORD) to 0.047 (PUD). Furthermore, it was inversely related to IBD (OR = 0.992, 95% CI: 0.986, 0.998, adjusted P = 0.023) and suggestively associated with its UC subtype (OR = 0.990, 95% CI: 0.982, 0.998, adjusted P = 0.059). There were no associations between genetically predicted adult-onset asthma and the mentioned gastrointestinal disorders.

CONCLUSIONS

This study provides evidence that the presence of asthma onset in childhood increases the risk for GORD, PUD, and IBS but decreases the risk for IBD in adults. The lower risk for IBD may be attributed to a lower risk primarily for UC.

Cigarette Smoking and Human Gut Microbiota in Healthy Adults: A Systematic Review

The intestinal microbiota is a crucial regulator of human health and disease because of its interactions with the immune system. Tobacco smoke also influences the human ecosystem with implications for disease development. This systematic review aims to analyze the available evidence, until June 2021, on the relationship between traditional and/or electronic cigarette smoking and intestinal microbiota in healthy human adults. Of the 2645 articles published in PubMed, Scopus, and Web of Science, 13 were included in the review. Despite differences in design, quality, and participants’ characteristics, most of the studies reported a reduction in bacterial species diversity, and decreased variability indices in smokers’ fecal samples. At the phylum or genus level, the results are very mixed on bacterial abundance both in smokers and non-smokers with two exceptions. Prevotella spp. appears significantly increased in smokers and former smokers but not in electronic cigarette users, while Proteobacteria showed a progressive increase in Desulfovibrio with the number of pack-years of cigarette (p = 0.001) and an increase in Alphaproteobacteria (p = 0.04) in current versus never smokers. This attempt to systematically characterize the effects of tobacco smoking on the composition of gut microbiota gives new perspectives on future research in smoking cessation and on a new possible use of probiotics to contrast smoke-related dysbiosis.

Interstitial Fluid Behavior and Diseases

Living things comprise a typical hierarchical and porous medium, and their most fundamental logical architectures are interstitial structures encapsulating parenchymal structures. The recent discovery of the efficient transport mechanisms of interstitial streams has provided a new understanding of these complex activities. The substance transport of interstitial streams follows mesoscopic fluid behavior dynamics, which is intimately associated with material transfer in nanoconfined spaces and a unique signal transmission. Accordingly, the evaluation of interstitial stream transport behavior at the mesoscopic scale is essential. In this review, recent advances in physical and chemical properties, the substance transport model, and the characterization methods of interstitial streams at the mesoscopic scale, as well as the relationships between interstitial streams and disease are summarized. Interstitial stream transport can be used as a basis to fully mine hierarchal behavior in images to expand imaging behavior into an omics field. By starting from the perspective of soft matter, a new understanding can be gained of health and disease and quantitative physical markers for research, clinical diagnosis, and treatment can be provided, as well as prognosis evaluation in complex diseases such as cancer and Alzheimer's disease. This will provide a foundation for the development of medicine of soft matter.

Gastric motility and pulmonary function in children with functional abdominal pain disorders and asthma: A pathophysiological study

Background

An association has been shown between functional abdominal pain disorders (FAPDs) and asthma. However, the exact reason for this association is obscured. The main objective of this study is to identify the possible underlying pathophysiological mechanisms for the association between FAPDs and asthma using gastric motility and lung function tests.

Methods

This was a cross-sectional comparative study that consisted of four study groups. Twenty-four children (age 7–12 years) each were recruited for four study groups; asthma only, FAPDs only, both asthma and FAPDs, and healthy controls. Asthma was diagnosed using the history and bronchodilator reversibility test. The diagnosis of FAPDs was made using Rome IV criteria. All subjects underwent ultrasound assessment of gastric motility and pulmonary function assessment by spirometry, using validated techniques.

Results

All gastric motility parameters, gastric emptying rate, amplitude of antral contraction, and antral motility index, were significantly impaired in children with FAPDs only, children with asthma only, and children with both asthma & FAPDs, compared to controls (p<0.05). Pulmonary function parameters indicating airway obstruction (FEV₁/FVC ratio, peak expiratory flow rate, FEF25-75%) were not impaired in children with FAPDs only compared to controls (p>0.05), but significantly impaired in children with asthma and children with both disorders. Antral motility index correlated with the FEV₁/FVC ratio (r = 0.60, p = 0.002) and FEF25%-75% (r = 0.49, p = 0.01) in children with both asthma and FAPDs.

Conclusions

Gastric motor functions were significantly impaired in children with asthma, children with FAPDs, and children with both disorders. Motility index, measuring overall gastric motor activity, showed a significant positive correlation with lung function parameters that measure airflow limitation. Therefore, these diseases might arise as a result of primary disturbance of smooth muscle activity in the airways and gastrointestinal wall, which could be a possible pathophysiological mechanism for this association between asthma and FAPDs.

The role of gut microbiota in infectious diseases

The intestine, the largest immune organ in the human body, harbors approximately 10¹³ microorganisms, including bacteria, fungi, viruses, and other unknown microbes. The intestine is a most important crosstalk anatomic structure between the first (the host) and second (the microorganisms) genomes. The imbalance of the intestinal microecology, especially dysbiosis of the composition, structure, and function of gut microbiota, is linked to human diseases. In this review, we investigated the roles and underlying mechanisms of gut microecology in the development, progression, and prognosis of infectious diseases. Furthermore, we discussed potential new strategies of prevention and treatment for infectious diseases based on manipulating the composition, structure, and function of intestinal microorganisms in the future. This article is categorized under: Infectious Diseases > Molecular and Cellular Physiology.

Gut-lung cross talk in COVID-19 pathology and fatality rate

Coronavirus disease 2019 (COVID-19) is the leading pandemic facing the world in 2019/2020; it is caused by a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, which necessitates clear understanding of the infectious agent. The virus manifests aggressive behavior with severe clinical presentation and high mortality rate, especially among the elderly and patients living with chronic diseases. In the recent years, the role of gut microbiota, in health and disease, has been progressively studied and highlighted. It is through gut microbiota-organ bidirectional pathways, such as gut-brain axis, gut-liver axis, and gut-lung axis, that the role of gut microbiota in prompting lung disease, among other diseases, has been proposed and accepted. It is also known that respiratory viral infections, such as COVID-19, induce alterations in the gut microbiota, which can influence immunity. Based on the fact that gut microbiota diversity is decreased in old age and in patients with certain chronic diseases, which constitute two of the primary fatality groups in COVID-19 infections, it can be assumed that the gut microbiota may play a role in COVID-19 pathology and fatality rate. Improving gut microbiota diversity through personalized nutrition and supplementation with prebiotics/probiotics will mend the immunity of the body and hence could be one of the prophylactic strategies by which the impact of COVID-19 can be minimized in the elderly and immunocompromised patients. In this chapter, the role of dysbiosis in COVID-19 will be clarified and the possibility of using co-supplementation of personalized prebiotics/probiotics with current therapies will be discussed.

Gut Microbiota Dysbiosis and COVID-19: Possible Links

Microbiota in the gastrointestinal system is a major determinant in health and disease status with its influence on immunity. Bidirectional relationship between gut microbiota and host immune system is well balanced in healthy individuals and a disruption (dysbiosis) can lead to gastrointestinal inflammations and metabolic disorders. Growing evidence support the cross-talk between gastrointestinal microbiota and lung that maintains host homeostasis and reduces the risk of disease development. The Gut-lung axis is possibly involved in the severity of COVID-19 with the association of dysbiosis. Targeted alterations in the gut microbiota could be considered to alleviate the disease severity.

Preliminary development of a questionnaire to measure the extra-pulmonary symptoms of severe asthma

Background

Research into the effects of asthma treatments on the extra-pulmonary symptoms of severe asthma is limited by the absence of a suitable questionnaire. The aim was to create a questionnaire suitable for intervention studies by selecting symptoms that are statistically associated with asthma pathology and therefore may improve when pathology is reduced.

Methods

Patients attending a specialist asthma clinic completed the 65-item General Symptom Questionnaire (GSQ-65), a questionnaire validated for assessing symptoms of people with multiple medically unexplained symptoms. Lung function (FEV1%) and cumulative oral corticosteroids (OCS) calculated from maintenance dose plus exacerbations were obtained from clinic records. Pathology was represented by the two components of a principal component analysis (PCA) of FEV1% and OCS. LASSO regression was used to select symptoms that had high coefficients with these two principal components and occurred frequently in severe asthma.

Results

100 patients provided data. PCA revealed two components, one where FEV1% and OCS were inversely related and another where they were directly related. LASSO regression revealed 39 symptoms with non-zero coefficients on one or more of the two principal components from which 16 symptoms were selected for the GSQ-A on the basis of magnitude of coefficient and frequency. Asthma symptoms measured by asthma control questionnaires were excluded. The GSQ-A correlated 0.33 and − 0.34 (p = 0.001) with the two principal components.

Conclusion

The GSQ-A assesses the frequency of 16 heterogenous non-respiratory symptoms that are associated with asthma severity using the statistical combination of FEV1% and OCS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-021-01730-0.

Coronavirus disease-19 and the gut-lung axis

Gastrointestinal and respiratory tract diseases often occur together. There are many overlapping pathologies, leading to the concept of the ‘gut–lung axis’ in which stimulation on one side triggers a response on the other side. This axis appears to be implicated in infections involving severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), which has triggered the global coronavirus disease 2019 (COVID-19) pandemic, in which respiratory symptoms of fever, cough and dyspnoea often occur together with gastrointestinal symptoms such as nausea, vomiting, abdominal pain and diarrhoea. Besides the gut–lung axis, it should be noted that the gut participates in numerous axes which may affect lung function, and consequently the severity of COVID-19, through several pathways. This article focuses on the latest evidence and the mechanisms that drive the operation of the gut–lung axis, and discusses the interaction between the gut–lung axis and its possible involvement in COVID-19 from the perspective of microbiota, microbiota metabolites, microbial dysbiosis, common mucosal immunity and angiotensin-converting enzyme II, raising hypotheses and providing methods to guide future research on this new disease and its treatments.

Effect of Cigarette Smoke on Gut Microbiota: State of Knowledge

Cigarette smoke is a representative source of toxic chemical exposures to humans, and the adverse consequences of cigarette smoking are mediated by its effect on both neuronal and immune-inflammatory systems. Cigarette smoking also is a major risk factor for intestinal disorders, such as Crohn's disease and peptic ulcer. On the other hand, cigarette smoking is protective against developing ulcerative colitis. The effects of cigarette smoking on intestinal disorders include changes in intestinal irrigation and microbiome, increases in permeability of the mucosa, and impaired mucosal immune responses. However, the underlying mechanism linking cigarette smoking with intestinal microbiota dysbiosis is largely unknown. In this communication, we first review the current knowledge about the mechanistic interaction between cigarette smoke and intestinal microbiota dysbiosis, which include the likely actions of nicotine, aldehydes, polycyclic aromatic hydrocarbons, heavy metals, volatile organic compounds and toxic gases, and then reveal the potential mechanisms of the lung-gut cross talk and skin-gut cross talk in regulating the balance of intestinal microbiota and the interrelation of intestinal microbiota dysbiosis and systemic disorders.

Gut-Lung Dysbiosis Accompanied by Diabetes Mellitus Leads to Pulmonary Fibrotic Change through the NF-κB Signaling Pathway

Growing evidence shows that the lungs are an unavoidable target organ of diabetic complications. However, the pathologic mechanisms of diabetic lung injury are still controversial. This study demonstrated the dysbiosis of the gut and lung microbiome, pulmonary alveolar wall thickening, and fibrotic change in streptozotocin-induced diabetic mice and antibiotic-induced gut dysbiosis mice compared with controls. In both animal models, the NF-κB signaling pathway was activated in the lungs. Enhanced pulmonary alveolar well thickening and fibrotic change appeared in the lungs of transgenic mice expressing a constitutively active NF-κB mutant compared with wild type. When lincomycin hydrochloride-induced gut dysbiosis was ameliorated by fecal microbiota transplant, enhanced inflammatory response in the intestine and pulmonary fibrotic change in the lungs were significantly decreased compared with lincomycin hydrochloride-treated mice. Furthermore, the application of fecal microbiota transplant and baicalin could also redress the microbial dysbiosis of the gut and lungs in streptozotocin-induced diabetic mice. Taken together, these data suggest that multiple as yet undefined factors related to microbial dysbiosis of gut and lungs cause pulmonary fibrogenesis associated with diabetes mellitus through an NF-κB signaling pathway.

Effect of Enteral Vitamin A on Fecal Calprotectin in Extremely Preterm Infants: A Nested Prospective Observational Study

BACKGROUND

Vitamin A has anti-inflammatory and immune-modulating properties. We aimed to assess whether enteral water-soluble vitamin A supplementation in extremely preterm infants decreases fecal calprotectin, a marker of intestinal inflammation.

METHODS

This was a prospective observational study nested in a randomized, double-blind, placebo-controlled clinical trial investigating enteral vitamin A (5,000 IU/day) for reducing the severity of bronchopulmonary dysplasia (BPD) in extremely preterm infants. Fecal calprotectin levels were measured using enzyme-linked immunosorbent assay after 28 days of Vitamin A or placebo supplementation.

RESULTS

Fecal calprotectin was measured in 66 infants (Vitamin A: 33, Placebo: 33). The mean (standard deviation) gestational age (25.5 [1.55] vs. 25.8 [1.48]; p = 0.341) (week), birth weight (810 [200] vs. 877 [251]; p = 0.240) (gram), and factors influencing fecal calprotectin levels were comparable between the vitamin A versus placebo group infants. All infants were exclusively fed with mother's or donor's human breast milk if mother's milk was unavailable using a standardized feeding regimen and received prophylactic probiotic supplementation. Fecal calprotectin levels (median; 25th-75th centiles) (micrograms/gram of feces) were not significantly different between vitamin A (152; 97-212) and placebo groups (179; 91-313) (p = 0.195). Two infants in the vitamin A group developed definite necrotizing enterocolitis compared to none in the placebo group. Incidence of BPD at 36 weeks postmenstrual age was similar between the groups (vitamin A: 18/33, placebo: 13/33, p = 0.218).

CONCLUSION

Enteral supplementation with water-soluble vitamin A did not affect fecal calprotectin levels in extremely preterm infants. Studies with a larger sample size are required to confirm the findings.

Crosstalk Between Lung and Extrapulmonary Organs in Infection and Inflammation

Acute and chronic lung inflammation is a risk factor for various diseases involving lungs and extrapulmonary organs. Intercellular and interorgan networks, including crosstalk between lung and brain, intestine, heart, liver, and kidney, coordinate host immunity against infection, protect tissue, and maintain homeostasis. However, this interaction may be counterproductive and cause acute or chronic comorbidities due to dysregulated inflammation in the lung. In this chapter, we review the relationship of the lung with other key organs during normal cell processes and disease development. We focus on how pneumonia may lead to a systemic pathophysiological response to acute lung injury and chronic lung disease through organ interactions, which can facilitate the development of undesirable and even deleterious extrapulmonary sequelae.

Functional abdominal pain disorders and asthma: two disorders, but similar pathophysiology?

INTRODUCTION

Functional abdominal pain disorders (FAPDs) and asthma are common ailments affecting both children and adults worldwide. Multiple studies have demonstrated an association between these two disorders. However, the exact reason for this observed association is not apparent.

AREAS COVERED

The current review has explored available literature and outlined multiple underlying pathophysiological mechanisms, common to both asthma and FAPDs, as possible reasons for this association.

EXPERT OPINION

Smooth muscle dysfunction, hypersensitivity and hyper-responsiveness, mucosal inflammation, and barrier dysfunction involving gastrointestinal and respiratory tracts are the main underlying pathophysiological mechanisms described for the generation of symptoms in FAPDs and asthma. In addition, alterations in neuroendocrine regulatory functions, immunological dysfunction, and microbial dysbiosis have been described in both disorders. We believe that the pathophysiological processes that were explored in this article would be able to expand the mechanisms of the association. The in-depth knowledge is needed to be converted to therapeutic and preventive strategies to improve the quality of care of children suffering from FAPDs and asthma.

Effect of probiotics, prebiotics and synbiotics for chronic bronchitis or chronic obstructive pulmonary disease: A protocol for systematic review and meta-analysis

BACKGROUND

Probiotics, prebiotics and synbiotics have been widely used in the treatment of respiratory diseases, but their clinical efficacy for treating chronic bronchitis (CB) or chronic obstructive pulmonary disease (COPD) has not been well studied.

METHODS

The following electronic databases will be searched for eligible randomized controlled trials: the Cochrane Library, EMBASE, MEDLINE, PubMed, Scopus, the Web of Science, the China National Knowledge Infrastructure, the Wanfang database, and the China Science and Technology Journal database (VIP Information Network). We will search these electronic databases weekly and extract relevant data from their inception dates until September 30, 2020. Risk of publication bias will be evaluated by the Cochrane Handbook for Systematic Reviews of Interventions. Data synthesis will be conducted using Review Manager (RevMan) version 5.3 software. Sensitivity and quality of evidence analyses will be conducted.

RESULTS

This systematic review and meta-analysis will provide a high-quality synthesis from existing evidence for estimating the efficacy and safety of probiotics, prebiotics and synbiotics in the treatment of CB or COPD.

CONCLUSION

This systematic review and meta-analysis will provide reliable and accurate evidence to guide the use of probiotics, prebiotics and synbiotics in the treatment of CB or COPD.

REGISTRATION OSF REGISTRATION NUMBER

DOI 10.17605/OSF.IO/SP35M.

Human Respiratory and Gut Microbiomes-Do They Really Contribute to Respiratory Health?

Human gastrointestinal and respiratory tracts are colonized by diverse polymicrobial communities shortly after birth, which are continuously molded by environmental exposure. The development of the resident microbiota in early life is a critical factor in the maturation of a healthy immune system. Disturbances to the intricate relationship between environmental exposure and maturation of the infant microbiome have been increasingly identified as a potential contributor to a range of childhood diseases. This review details recent evidence that implicates the contribution of gut and airway microbiome to pediatric respiratory health.

Gut-lung axis and dysbiosis in COVID-19

COVID-19, a novel infectious disease, caused by SARS-CoV-2, affected millions of people around the world with a high mortality rate. Although SARS-CoV-2 mainly causes lung infection, gastrointestinal symptoms described in COVID-19 patients and detection of the viral RNA in feces of infected patients drove attentions to a possible fecal-oral transmission route of SARS-CoV-2. However, not only the viral RNA but also the infectious viral particles are required for the viral infection and no proof has been demonstrated the transmission of the infectious virus particles via the fecal-oral route yet. Growing evidence indicates the crosstalk between gut microbiota and lung, that maintains host homeostasis and disease development with the association of immune system. This gut-lung interaction may influence the COVID-19 severity in patients with extrapulmonary conditions. Severity of COVID-19 has mostly associated with old ages and underlying medical conditions. Since the diversity in the gut microbiota decreases during aging, dysbiosis could be the reason for older adults being at high risk for severe illness from COVID-19. We believe that gut microbiota contributes to the course of COVID-19 due to its bidirectional relationship with immune system and lung. Dysbiosis in gut microbiota results in gut permeability leading to secondary infection and multiple organ failure. Conversely, disruption of the gut barrier integrity due to dysbiosis may lead to translocation of SARS-CoV-2 from the lung into the intestinal lumen via circulatory and lymphatic system. This review points out the role of dysbiosis of the gut microbiota involving in sepsis, on the severity of SARS-CoV-2 infection. Additionally, this review aims to clarify the ambiguity in fecal-oral transmission of SARS- CoV-2.

Altered gut microbiota in infants is associated with respiratory syncytial virus disease severity

Background

Respiratory syncytial virus (RSV) is the number one cause of lower respiratory tract infections in infants. There are still no vaccines or specific antiviral therapies against RSV, mainly due to the inadequate understanding of RSV pathogenesis. Recent data suggest a role for gut microbiota community structure in determining RSV disease severity. Our objective was to determine the gut microbial profile associated with severe RSV patients, which could be used to help identify at-risk patients and develop therapeutically protective microbial assemblages that may stimulate immuno-protection.

Results

We enrolled 95 infants from Le Bonheur during the 2014 to 2016 RSV season. Of these, 37 were well-babies and 58 were hospitalized with RSV. Of the RSV infected babies, 53 remained in the pediatric ward (moderate) and 5 were moved to the pediatric intensive care unit at a later date (severe). Stool samples were collected within 72 h of admission; and the composition of gut microbiota was evaluated via 16S sequencing of fecal DNA. There was a significant enrichment in S24_7, Clostridiales, Odoribacteraceae, Lactobacillaceae, and Actinomyces in RSV (moderate and severe) vs. controls. Patients with severe RSV disease had slightly lower alpha diversity (richness and evenness of the bacterial community) of the gut microbiota compared to patients with moderate RSV and healthy controls. Beta diversity (overall microbial composition) was significantly different between all RSV patients (moderate and severe) compared to controls and had significant microbial composition separating all three groups (control, moderate RSV, and severe RSV).

Conclusions

Collectively, these data demonstrate that a unique gut microbial profile is associated with RSV disease and with severe RSV disease with admission to the pediatric intensive care unit. More mechanistic experiments are needed to determine whether the differences observed in gut microbiota are the cause or consequences of severe RSV disease.

The distribution characteristics of intestinal microbiota in children with community-acquired pneumonia under five Years of age

Pneumonia is the leading cause of morbidity and mortality in children under five years of age worldwide. Over the past decades, studies have shown that the upper respiratory pathogens are closely related to the occurrence of pneumonia. However, the co-occurrence of gut microbiome dysbiosis may have clinical manifestation in the prognosis of childhood pneumonia. The aim of the present study is to investigate the differences in gut microbial communities between children's diagnosed community-acquired pneumonia (CAP) under five compared to healthy controls in Inner Mongolia. Fecal samples were collected from children with CAP and healthy controls (<5 years old) and the genomic microbiome 16S rRNA was amplified using the hypervariable V4 region and subjected to MiSeq Illumina sequencing, and then analyzed for microbiota composition and phenotype. Finally functional profiling was performed by KEGG pathways analyses. Our results revealed a gut microbiota dysbiosis in children with CAP. Distinct gut microbiome composition and structure were associated with childhood CAP between two age categories compared to healthy controls. In addition, the phylogenic phenotype's prediction was found to be significantly different between the groups. The prominent genera in age group of 0-3 were Bifidobacterium and Enterococcus. On the contrary, Escherichia-Shigella, Prevotella, Faecalibacterium and Enterobacter were remarkably decreased in most of the fecal samples from CAP patients in age group of 0-3 compared to the control. At the genus level, the CAP children in the age group of 4-5 showed an increase in the abundance of Escherichia/Shigella, Bifidobacterium, Streptococcus and Psychrobacter and, a decrease in the abundance of Faecalibacterium, Bacteroides, Lachnospiraceae and Ruminococcus compared with the matched healthy controls. Moreover, CAP children in both age groups exhibited distinct profiles in the KEGG functional analysis. Our data revealed that the gut microbiota differ between CAP patients and health children and certain gut microbial species are associated with CAP. Further research to identify specific microbial species which may contribute to the development CAP are merited. In addition, rectification of microbiota dysbiosis may provide supplemental benefits for treatment of the childhood CAP.

Microbial interactions in the atopic march

The human body is populated by a large number of microorganisms and exist in symbiosis with these immensely diverse communities, which are suggested to influence health and disease. The microbiota plays an essential role in the maturation and function of the immune system. The prevalence of atopic diseases has increased drastically over the past decades, and the co-occurrence of multiple allergic diseases and allergic sensitization starting in early life has gained a great deal of attention. Immune responses in different organs affected by allergic diseases (e.g. skin, intestine and lung) may be linked to microbial changes in peripheral tissues. In the current review, we provide an overview of the current understanding of microbial interactions in allergic diseases and their potential role in the atopic march.

Association between Irritable Bowel Syndrome and Allergic Diseases: To Make a Case for Aeroallergen

Irritable bowel syndrome (IBS) is a functional gastrointestinal disease and the most common cause of prolonged abdominal pain and bowel disturbances in the developed world. While initially thought to be functional or psychosomatic in nature, IBS is now recognized as a heterogeneous group of conditions. A subset of IBS patients and patients with allergic diseases share some characteristic inflammatory features. In fact, atopic children show an increased likelihood of developing IBS as adults. Given these findings, a subset of IBS may be suffering from allergy-related gut diseases. In this review, we present the allergy-related comorbidities of IBS, including genetic, environmental, and immunologic factors. We discuss studies demonstrating an increased sensitization of IBS patients to aeroallergens compared to food allergens. We then postulate potential pathophysiological mechanisms underlying both IBS and aeroallergens in the gut, followed by potential implications in the screening and treatment of allergies in IBS patients.

Association between irritable bowel syndrome and asthma: a meta-analysis and systematic review

Background:

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder often seen in outpatient clinics. Diagnosing IBS is often challenging, as it frequently presents with other complicated rheumatological and psychiatric conditions. Asthma has often been associated with gastrointestinal conditions such as gastroesophageal reflux disease and eosinophilic esophagitis. This review and meta-analysis aimed at a better understanding of the association between the conditions.

Methods:

A comprehensive literature review was completed using MEDLINE and EMBASE databases through January 2019. Case-control, cross-sectional and cohort studies that evaluated the association between asthma and IBS were divided into 2 groups: the first included studies that identified patients with asthma first and then looked for the presence of IBS. The second group included studies that identified IBS patients first and then looked for the presence of asthma. Random effects meta-analysis was conducted using STATA 15.

Results:

The search strategy generated a total of 634 studies and 10 eligible studies (8 case-control and 2 cross-sectional) were selected for meta-analysis. Analysis showed that asthmatics have twice the risk of having IBS (pooled odds ratio [OR] 2.0, 95% confidence interval [CI] 1.5-2.8), and patients with IBS have twice the risk of having asthma (pooled OR 2.2, 95%CI 1.3-3.9).

Conclusions:

This study highlights that the risk of asthma is considerably higher in IBS patients and vice versa. Physicians should look out for pulmonary symptoms in IBS patients and consider evaluation with spirometry when necessary. Likewise, asthmatics presenting with gastrointestinal symptoms may need consultation and evaluation for IBS.

Evidence for similarity in symptoms and mechanism: The extra-pulmonary symptoms of severe asthma and the polysymptomatic presentation of fibromyalgia

BACKGROUND

Asthma is a disease of the lung and a systemic disease. Functional disorders are associated with multiple systemic abnormalities that have been explained by complexity models. The aim was to test the similarity in type and aetiology between the extra-pulmonary symptoms of severe asthma and the symptoms of fibromyalgia.

METHODS

One Hundred patients recruited from a specialist severe asthma clinic and 1751 people reporting different functional disorder diagnoses recruited via the internet completed the same 60-item questionnaire. Symptom patterns were compared between groups using a new measure, the symptom pattern similarity index where 0 = no relationship, 1 = identical patterns between groups.

RESULTS

Severe asthma patients report numerous extra-pulmonary symptoms. The similarity index between the symptom pattern of the asthma patients with other groups was irritable bowel syndrome = 0.54, chronic fatigue syndrome = 0.69, and fibromyalgia = 0.75. The index between fibromyalgia and asthma patients with the most and least frequent extra-pulmonary symptoms was 0.81 and 0.55 respectively.

CONCLUSIONS

Patients with severe asthma have numerous extra-pulmonary symptoms similar in type and pattern to the symptoms of fibromyalgia. The similarity of the symptom pattern between asthma and fibromyalgia increases as the number of extra-pulmonary symptoms increases as predicted by network theory and previously shown to be the case with other functional disorders. These findings support the hypothesis that functional disorders and extra-pulmonary asthma symptoms have a common complexity or network aetiology. Evidence based behavioural interventions for fibromyalgia may be helpful for patients with severe asthma reporting extra-pulmonary symptoms.

Microbes, metabolites, and the gut-lung axis

The microbiota plays an essential role in the education, development, and function of the immune system, both locally and systemically. Emerging experimental and epidemiological evidence highlights a crucial cross-talk between the intestinal microbiota and the lungs, termed the 'gut-lung axis'. Changes in the constituents of the gut microbiome, through either diet, disease or medical interventions (such as antibiotics) is linked with altered immune responses and homeostasis in the airways. The importance of the gut-lung axis has become more evident following the identification of several gut microbe-derived components and metabolites, such as short-chain fatty acids (SCFAs), as key mediators for setting the tone of the immune system. Recent studies have supported a role for SCFAs in influencing hematopoietic precursors in the bone marrow-a major site of innate and adaptive immune cell development. Here, we review the current understanding of host-microbe cross-talk along the gut-lung axis. We highlight the importance of SCFAs in shaping and promoting bone marrow hematopoiesis to resolve airway inflammation and to support a healthy homeostasis.

Bacterial secretion of histamine within the gut influences immune responses within the lung

BACKGROUND

Histamine is an important immunomodulator influencing both the innate and adaptive immune system. Certain host cells express the histidine decarboxylase enzyme (HDC), which is responsible for catalysing the decarboxylation of histidine to histamine. We and others have shown that bacterial strains can also express HDC and secrete histamine; however, the influence of bacterial-derived histamine on the host immune responses distant to the gut is unclear.

METHODS

The Escherichia coli BL21 (E coli BL21) strain was genetically modified to express the Morganella morganii (M morganii)-derived HDC gene (E coli BL21_HTW). E coli BL21 and E coli BL21_HTW were gavaged to ovalbumin (OVA) sensitized and challenged mice to investigate the effect of bacterial-derived histamine on lung inflammatory responses.

RESULTS

Oral administration of E coli BL21_HTW, which is able to secrete histamine, to wild-type mice reduced lung eosinophilia and suppressed ex vivo OVA-stimulated cytokine secretion from lung cells in the OVA respiratory inflammation mouse model. In histamine receptor 2 (H2R)-deficient mice, administration of histamine-secreting bacteria also reduced inflammatory cell numbers in bronchoalveolar lavage (BAL). However, the suppressive effect of bacterial-derived histamine on BAL inflammation was lost in HDC-deficient mice. This loss of activity was associated with increased expression of histamine degrading enzymes and reduced histamine receptor expression.

CONCLUSION

Histamine secretion from bacteria within the gut can have immunological consequences at distant mucosal sites, such as within the lung. These effects are influenced by host histamine receptor expression and the expression of histamine degrading enzymes.

Population based study: atopy and autoimmune diseases are associated with functional dyspepsia and irritable bowel syndrome, independent of psychological distress

BACKGROUND

The pathogenesis of functional GI disorders (FGIDs) is uncertain. However, underlying immune activation and psychological distress has been documented in irritable bowel syndrome (IBS) and functional dyspepsia (FD). Epidemiological data from the UK suggest that FGIDs are linked to atopy and certain autoimmune diseases but this has not been confirmed.

AIM

To test if allergic or autoimmune diseases are independently associated with FGIDs, irrespective of psychological distress in a large population based study.

METHODS

A total of 3542 people (mean age 57.9 years and 52.7% females) randomly selected from the Australian population, returned a mail survey (response rate = 43%). The survey asked about a physician diagnosis of autoimmune disease (scleroderma, psoriasis, rheumatoid arthritis and diabetes mellitus) or allergic conditions (asthma, food, pollen and/or animal allergy). The questionnaire assessed psychological distress and Rome III criteria for FD and IBS.

RESULTS

Asthma, food, pollen and animal allergies, psoriasis and rheumatoid arthritis were univariately significantly associated with IBS and FD. Food allergy (OR = 1.66; 95% CI = 1.15-2.40, P = 0.007), psoriasis (OR = 1.81; 95% CI = 1.19-2.74, P = 0.006) and rheumatoid arthritis (OR = 1.68; 95% CI = 1.15-2.4, P = 0.007) were independent risk factors for IBS, controlling for age, gender and psychological distress. In FD, asthma (OR = 1.32; 95% CI = 1.04-1.68, P = 0.025) and food allergy (OR = 1.78; 95% CI = 1.28-2.49, P = 0.001) were independent predictors, controlling for age, sex and psychological distress.

CONCLUSIONS

There is evidence that both atopic and autoimmune diseases are risk factors for FGIDs, independent of psychological distress, differing in IBS and FD. This provides evidence that different peripheral pathways may be involved in the pathogenesis of certain FGIDs.