COVID-19 as a trigger of irritable bowel syndrome: A review of potential mechanisms

In December 2019 a novel coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), started spreading from Wuhan city of Chinese Hubei province and rapidly became a global pandemic. Clinical symptoms of the disease range from paucisymptomatic disease to a much more severe disease. Typical symptoms of the initial phase include fever and cough, with possible progression to acute respiratory distress syndrome. Gastrointestinal manifestations such as diarrhoea, vomiting and abdominal pain are reported in a considerable number of affected individuals and may be due to the SARS-CoV-2 tropism for the peptidase angiotensin receptor 2. The intestinal homeostasis and microenvironment appear to play a major role in the pathogenesis of COVID-19 and in the enhancement of the systemic inflammatory responses. Long-term consequences of COVID-19 include respiratory disturbances and other disabling manifestations, such as fatigue and psychological impairment. To date, there is a paucity of data on the gastrointestinal sequelae of SARS-CoV-2 infection. Since COVID-19 can directly or indirectly affect the gut physiology in different ways, it is plausible that functional bowel diseases may occur after the recovery because of potential pathophysiological alterations (dysbiosis, disruption of the intestinal barrier, mucosal microinflammation, post-infectious states, immune dysregulation and psychological stress). In this review we speculate that COVID-19 can trigger irritable bowel syndrome and we discuss the potential mechanisms.     

Aging of the mammalian gastrointestinal tract: a complex organ system

Gastrointestinal disorders are a major cause of morbidity in the elderly population. The gastrointestinal tract is the most complex organ system; its diverse cells perform a range of functions essential to life, not only secretion, digestion, absorption and excretion, but also, very importantly, defence. The gastrointestinal tract acts not only as a barrier to harmful materials and pathogens but also contains the vast number of beneficial bacterial populations that make up the microbiota. Communication between the cells of the gastrointestinal tract and the central nervous and endocrine systems modifies behaviour; the organisms of the microbiota also contribute to this brain–gut–enteric microbiota axis. Age-related physiological changes in the gut are not only common, but also variable, and likely to be influenced by external factors as well as intrinsic aging of the cells involved. The cellular and molecular changes exhibited by the aging gut cells also vary. Aging intestinal smooth muscle cells exhibit a number of changes in the signalling pathways that regulate contraction. There is some evidence for age-associated degeneration of neurons and glia of the enteric nervous system, although enteric neuronal losses are likely not to be nearly as extensive as previously believed. Aging enteric neurons have been shown to exhibit a senescence-associated phenotype. Epithelial stem cells exhibit increased mitochondrial mutation in aging that affects their progeny in the mucosal epithelium. Changes to the microbiota and intestinal immune system during aging are likely to contribute to wider aging of the organism and are increasingly important areas of analysis. How changes of the different cell types of the gut during aging affect the numerous cellular interactions that are essential for normal gut functions will be important areas for future aging research.     

Emerging roles of lactic acid bacteria in protection against colorectal cancer

Colorectal cancer(CRC)is the third leading cause of cancer deaths worldwide and the fourth most common cancer diagnosed among men and women in the United States.Considering the risk factors of CRC,dietary therapy has become one of the most effective approaches in reducing CRC morbidity and mortality.The use of probiotics is increasing in popularity for both the prevention and treatment of a variety of diseases.As the most common types of microbes used as probiotics,lactic acid bacteria(LAB)are comprised of an ecologically diverse group of microorganisms united by formation of lactic acid as the primary metabolite of sugar metabolism.LAB have been successfully used in managing diarrhea,food allergies,and inflammatory bowel disease.LAB also demonstrated a host of properties in preventing colorectal cancer development by inhibiting initiation or progression through multiple pathways.In this review,we discuss recent insights into cellular and molecular mechanisms of LAB in CRC prevention including apoptosis,antioxidant DNA damages,immune responses,and epigenetics.The emerging experimental findings from clinical trials as well as the proposed mechanisms of gut microbiota in carcinogenesis will also be briefly discussed.     

Microbiota,infecciones gastrointestinales,inflamación de bajo grado y antibioticoterapia en el síndrome de intestino irritable. Una revisión basada en evidencias

BackgroundPost-infectious irritable bowel syndrome (PI-IBS) prevalence, small intestinal bacterial overgrowth (SIBO), altered microbiota, low-grade inflammation, and antibiotic therapy in IBS are all controversial issues.AimsTo conduct an evidence-based review of these factors.MethodsA review of the literature was carried out up to July 2012, with the inclusion of additional articles as far as August 2013, all of which were analyzed through the Oxford Centre for Evidence-Based Medicine (OCEBM) system.Results1. There is greater SIBO probability in IBS when breath tests are performed, but prevalence varies widely (2-84%). 2. The gut microbiota in individuals with IBS is different from that in healthy subjects, but a common characteristic present in all the patients has not been established. 3. The incidence and prevalence of PI-IBS varies from 9-10% and 3-17%, respectively, and the latter decreases over time. Bacterial etiology is the most frequent but post-viral and parasitic cases have been reported. 4. A sub-group of patients has increased enterochromaffin cells, intraepithelial lymphocytes, and mast cells in the intestinal mucosa, but no differences between PI-IBS and non-PI-IBS have been determined. 5. Methanogenic microbiota has been associated with IBS with constipation. 6. Rifaximin at doses of 400 mg TID/10 days or 550 mg TID/14 days is effective treatment for the majority of overall symptoms and abdominal bloating in IBS. Retreatment effectiveness appears to be similar to that of the first cycle.ConclusionsFurther studies are required to determine the nature of the gut microbiota in IBS and the differences in low-grade inflammation between PI-IBS and non-PI-IBS. Rifaximin has shown itself to be effective treatment for IBS, regardless of prior factors.     

The role of the gut and microbes in the pathogenesis of spondyloarthritis

The intestinal microbiota is firmly implicated not only in the pathogenesis of inflammatory bowel disease (IBD) but increasingly also in the development of inflammation at extraintestinal tissue sites. Significant clinical, genetic, immunological, and microbiological overlap exists between IBD and spondyloarthritis (SpA), which indicates that pathophysiological mechanisms are shared between these diseases and may center on the intestinal microbiota. Recently, culture-independent techniques have enabled the microbiota in health and disease to be described in increasing detail. Moreover, functional studies have identified myriad host effector and regulatory pathways that shape or are shaped by this microbial community. We consider the complex relationship between SpA pathogenesis and gut microbes, with a discussion of how manipulation of the gut microbiota itself may be a promising future target for SpA therapy.     

肠道菌群与脑-肠轴功能相互影响的研究进展

人体肠道内的菌群参与了许多生理功能的维持和疾病的发生。作为大脑和胃肠道功能相互调节的重要桥梁,脑-肠轴功能的正常发挥是肠道菌群维持稳定的条件。脑-肠轴紊乱可激活肠黏膜免疫,对肠道菌群产生影响,使菌群结构发生改变。反之,肠道菌群结构改变亦会影响神经系统发育,导致脑-肠轴功能紊乱,其中迷走神经和血清代谢物质在脑-肠轴功能的调节中发挥重要作用。本文就肠道菌群与脑-肠轴功能相互影响的研究进展作一综述。     

Germ-free housing conditions do not affect aortic root and aortic arch lesion size of late atherosclerotic low-density lipoprotein receptor-deficient mice

ABSTRACT

The microbiota has been linked to the development of atherosclerosis, but the functional impact of these resident bacteria on the lesion size and cellular composition of atherosclerotic plaques in the aorta has never been experimentally addressed with the germ-free low-density lipoprotein receptor-deficient (Ldlr^?/- ) mouse atherosclerosis model. Here, we report that 16 weeks of high-fat diet (HFD) feeding of hypercholesterolemic Ldlr^?/- mice at germ-free (GF) housing conditions did not impact relative aortic root plaque size, macrophage content, and necrotic core area. Likewise, we did not find changes in the relative aortic arch lesion size. However, late atherosclerotic GF Ldlr^?/- mice had altered inflammatory plasma protein markers and reduced smooth muscle cell content in their atherosclerotic root plaques relative to CONV-R Ldlr^?/- mice. Neither absolute nor relative aortic root or aortic arch plaque size correlated with age. Our analyses on GF Ldlr^?/- mice did not reveal a significant contribution of the microbiota in late aortic atherosclerosis.     

Gut microbiota of children with atopic dermatitis: Controlled study in the metropolitan region of São Paulo,Brazil

BackgroundIt is possible that imbalances in the composition of the gut microbiota or the relationship of the microbiota with the host may be implicated in the origin of allergy. Therefore, we studied the intestinal microbiota of children with atopic dermatitis (AD).MethodsCross-sectional study with 81 children aged 5–11; 23 with AD and 58 controls. Surveys were conducted to obtain demographic, socioeconomic and neonatal data. Diagnosis of AD was made based on the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire. Eubacteria, Bacteroidetes, Firmicutes, B. fragilis, E. coli, Lactobacillus spp., S. aureus, E. faecalis, Salmonella spp., M. smithii, Bifidobacterium spp., C. difficile and C. perfringens were quantified using real-time PCR.ResultsThe analysis showed an association between presence of C. difficile (OR: 5.88; 95 % CI: 1.24; 27.98), greater abundance of bifidobacteria (OR: 11.09; 95 % CI: 2.14; 57.39) and a lower abundance of lactobacilli (OR: 0.07; 95 % CI: 0.01; 0.51) in the gut microbiota of children with AD. Counts of Eubacteria (0,05 × 10³ and 8.49 × 10³), B. fragilis (0.72 × 10⁹ and 4.5 × 10⁹), Lactobacillus spp. (0.02 × 10⁸ and 0.38 × 10⁸), E. coli (0.13 × 10⁹ and 1.52 × 10⁹) and M. smithii (0.02 × 10⁸ and 0.31 × 10⁸) were lower in children with AD (P < 0.05).ConclusionsThis study confirmed that children living in the metropolitan area of São Paulo (Brazil) with AD have a different microbiota pattern with higher prevalence of C. difficile, lower abundance of Lactobacillus and greater abundance of bifidobacteria, regardless of socioeconomic status.     

Profiling of the microbiota in the remaining sports drink and orange juice in plastic bottles after direct drinking

ObjectivesThe survival of bacteria in the sports drink and orange juice remaining in and at the mouth of bottles after direct drinking was examined after immediately drinking and incubation at 37 °C for 24 h.MethodsNine healthy participants were asked to drink approximately 100 mL of a plastic bottled sports drink or orange juice. The samples were cultured anaerobically at 37 °C for 7 days. Genomic DNA was extracted from the resulting individual colonies, and bacterial species were identified using 16 S rRNA gene sequencing.ResultsThe mean amount of bacteria in the remaining sports drink and orange juice, immediately after drinking, were (1.6 ± 2.3) × 10³ colony-forming units (CFU)/mL and (2.9 ± 3.3) × 10³ CFU/mL, respectively. Additionally, bacteria recovered from the mouths of the sports drink and orange juice bottles were (2.5 ± 5.5) × 10⁴ CFU/mL and (5.8 ± 2.4) × 10³ CFU/mL, respectively. Oral bacteria, such as Streptococcus, Actinomyces, Neisseria, and Rothia were found to be transferred in the sports drink and orange juice, and the bacteria were scarcely detected after incubation at 37 °C for 24 h.ConclusionsThe bacterial levels differed significantly from the previously reported levels in bottled tea 24 h after drinking, suggesting that remaining drinks with low pH levels can be preserved for a longer period.