Microbiota and IBD: Current knowledge and future perspectives

Zinc and Inflammatory Bowel Disease: From Clinical Study to Animal Experiment

Inflammatory bowel disease (IBD) is a chronic inflammatory disease of the gastrointestinal tract (GI) with a high incidence rate globally, and IBD patients are often accompanied by zinc deficiency. This review aims to summarize the potential therapeutic value of zinc supplementation in IBD clinical patients and animal models. Zinc supplementation can relieve the severity of IBD especially in patients with zinc deficiency. The clinical severity of IBD were mainly evaluated through some scoring methods involving clinical performance, endoscopic observation, blood biochemistry, and pathologic biopsy. Through conducting animal experiments, it has been found that zinc plays an important role in alleviating clinical symptoms and improving pathological lesions. In both clinical observation and animal experiment of IBD, the therapeutic mechanisms of zinc interventions have been found to be related to immunomodulation, intestinal epithelial repair, and gut microbiota's balance. Furthermore, the antioxidant activity of zinc was clarified in animal experiment. Appropriate zinc supplementation is beneficial for IBD therapy, and the present evidence highlights that alleviating zinc-deficient status can effectively improve the severity of clinical symptoms in IBD patients and animal models.

Creeping fat and gut microbiota in Crohn's disease

In this article, we explored the role of adipose tissue, especially mesenteric adipose tissue and creeping fat, and its association with the gut microbiota in the pathophysiology and progression of Crohn's disease (CD). CD is a form of inflammatory bowel disease characterized by chronic inflammation of the gastrointestinal tract, influenced by genetic predisposition, gut microbiota dysbiosis, and environmental factors. Gut microbiota plays a crucial role in modulating immune response and intestinal inflammation and is associated with the onset and progression of CD. Further, visceral adipose tissue, particularly creeping fat, a mesenteric adipose tissue characterized by hypertrophy and fibrosis, has been implicated in CD pathogenesis, inflammation, and fibrosis. The bacteria from the gut microbiota may translocate into mesenteric adipose tissue, contributing to the formation of creeping fat and influencing CD progression. Although creeping fat may be a protective barrier against bacterial invasion, its expansion can damage adjacent tissues, leading to complications. Modulating gut microbiota through interventions such as fecal microbiota transplantation, probiotics, and prebiotics has shown potential in managing CD. However, more research is needed to clarify the mechanisms linking gut dysbiosis, creeping fat, and CD progression and develop targeted therapies for microbiota modulation and fat-related complications in patients with CD.

Antioxidant Therapy in Inflammatory Bowel Diseases: How Far Have We Come and How Close Are We?

Inflammatory bowel diseases (IBD) pose a growing public health challenge with unclear etiology and limited efficacy of traditional pharmacological treatments. Alternative therapies, particularly antioxidants, have gained scientific interest. This systematic review analyzed studies from MEDLINE, Cochrane, Web of Science, EMBASE, and Scopus using keywords like "Inflammatory Bowel Diseases" and "Antioxidants." Initially, 925 publications were identified, and after applying inclusion/exclusion criteria-covering studies from July 2015 to June 2024 using murine models or clinical trials in humans and evaluating natural or synthetic substances affecting oxidative stress markers-368 articles were included. This comprised 344 animal studies and 24 human studies. The most investigated antioxidants were polyphenols and active compounds from medicinal plants (n = 242; 70.3%). The review found a strong link between oxidative stress and inflammation in IBD, especially in studies on nuclear factor kappa B and nuclear factor erythroid 2-related factor 2 pathways. However, it remains unclear whether inflammation or oxidative stress occurs first in IBD. Lipid peroxidation was the most studied oxidative damage, followed by DNA damage. Protein damage was rarely investigated. The relationship between antioxidants and the gut microbiota was examined in 103 animal studies. Human studies evaluating oxidative stress markers were scarce, reflecting a major research gap in IBD treatment. PROSPERO registration: CDR42022335357 and CRD42022304540.

Advancements in the Management of Pediatric and Adult Inflammatory Bowel Disease: A Systematic Review of Treatment Strategies and Long-Term Outcomes

Inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis (UC), remains a clinically complex condition in children and adults. This study is a systematic analysis of key developments in the treatment of inflammatory bowel diseases, as well as their efficacy and safety over time. Early diagnosis of pediatric IBD is very important since it affects growth and development in children. New therapeutic approaches like biological agents, small molecules, and gene or targeted drugs have given the medical fraternity new treatment protocols. There is a trend towards more selective therapies for adult IBD, especially for anti-tumor necrosis factor (anti-TNF) biologics, integrin antagonists, and interleukin-12/23 (IL-12/23) inhibitors. This review emphasizes the need for patient management where early intervention leading to mucosal healing has been identified to predict durable outcomes. Systematic analysis of existing literature comparing childhood and adult populations shows that morbidity, pathophysiology, therapeutic outcome, as well as the potential for adverse outcomes are dissimilar, which supports the need for differentiated therapy. This work also looks at long-term consequences of the intervention course, the avoidance of surgery, and an improvement in the quality and stability of life as well as reduction in further development of malignant transformation. The new developing strategy of gut microbiome modification and nutrition support for maintaining remission is also argued. Despite these progresses, issues still persist concerning the effectiveness of treatments, side effects, and patients' compliance. These recommendations give this review a prospective outlook of treatment regimens likely to define the future of IBD management for all age groups.

Inflammatory Bowel Disease: A Comprehensive Analysis of Molecular Bases, Predictive Biomarkers, Diagnostic Methods, and Therapeutic Options

In inflammatory bowel diseases (IBDs), such as Crohn's disease (CD) and ulcerative colitis (UC), the immune system relentlessly attacks intestinal cells, causing recurrent tissue damage over the lifetime of patients. The etiology of IBD is complex and multifactorial, involving environmental, microbiota, genetic, and immunological factors that alter the molecular basis of the organism. Among these, the microbiota and immune cells play pivotal roles; the microbiota generates antigens recognized by immune cells and antibodies, while autoantibodies target and attack the intestinal membrane, exacerbating inflammation and tissue damage. Given the altered molecular framework, the analysis of multiple molecular biomarkers in patients proves exceedingly valuable for diagnosing and prognosing IBD, including markers like C reactive protein and fecal calprotectin. Upon detection and classification of patients, specific treatments are administered, ranging from conventional drugs to new biological therapies, such as antibodies to neutralize inflammatory molecules like tumor necrosis factor (TNF) and integrin. This review delves into the molecular basis and targets, biomarkers, treatment options, monitoring techniques, and, ultimately, current challenges in IBD management.

Probiotics: Shaping the gut immunological responses

Probiotics are live microorganisms exerting beneficial effects on the host's health when administered in adequate amounts. Among the most popular and adequately studied probiotics are bacteria from the families Lactobacillaceae, Bifidobacteriaceae and yeasts. Most of them have been shown, both in vitro and in vivo studies of intestinal inflammation models, to provide favorable results by means of improving the gut microbiota composition, promoting the wound healing process and shaping the immunological responses. Chronic intestinal conditions, such as inflammatory bowel diseases (IBD), are characterized by an imbalance in microbiota composition, with decreased diversity, and by relapsing and persisting inflammation, which may lead to mucosal damage. Although the results of the clinical studies investigating the effect of probiotics on patients with IBD are still controversial, it is without doubt that these microorganisms and their metabolites, now named postbiotics, have a positive influence on both the host's microbiota and the immune system, and ultimately alter the topical tissue microenvironment. This influence is achieved through three axes: (1) By displacement of potential pathogens via competitive exclusion; (2) by offering protection to the host through the secretion of various defensive mediators; and (3) by supplying the host with essential nutrients. We will analyze and discuss almost all the in vitro and in vivo studies of the past 2 years dealing with the possible favorable effects of certain probiotic genus on gut immunological responses, highlighting which species are the most beneficial against intestinal inflammation.

Alterations in Gut Microbiota as Early Biomarkers for Predicting Inflammatory Bowel Disease Onset and Progression: A Systematic Review

Inflammatory bowel disease (IBD) is a chronic ailment impacting the digestive system, triggered by an unusual reaction of the immune system. It includes two types of diseases: ulcerative colitis and Crohn's disease. Nonetheless, the diagnosis and evaluation of disease progression in IBD are difficult due to the absence of distinct indicators. While conventional biomarkers from blood plasma and feces, such as C-reactive protein, fecal calprotectin, and S100A12, can be employed to gauge inflammation, they are not exclusive to IBD. There is a broad consensus that intestinal microorganisms significantly contribute to the onset of intestinal imbalance, a condition intimately linked with the cause and development of IBD. Numerous studies have indicated that the makeup of intestinal microorganisms varies between individuals with IBD and those who are healthy, particularly concerning the diversity of microbes and the proportional prevalence of certain bacteria. A total of 1475 records underwent examination. Following the eligibility assessment, 17 reports were considered. The final review encompassed 12 studies, as five articles were excluded due to insufficient details regarding cases, controls, and comparability. This article suggests that gut microbiota has potential biomarkers for the noninvasive evaluation of IBD activity. Recognizing the microbiome linked with disease activity paves the way for the development of a group of microbiota-derived indicators to evaluate the initiation and advancement of IBD. This article discusses whether changes in gut microbial composition can serve as early indicators of IBD onset and progression.

Campylobacter jejuni Surface-Bound Protease HtrA, but Not the Secreted Protease nor Protease in Shed Membrane Vesicles, Disrupts Epithelial Cell-to-Cell Junctions

Fundamental functions of the intestinal epithelium include the digestion of food, absorption of nutrients, and its ability to act as the first barrier against intruding microbes. Campylobacter jejuni is a major zoonotic pathogen accounting for a substantial portion of bacterial foodborne illnesses. The germ colonizes the intestines of birds and is mainly transmitted to humans through the consumption of contaminated poultry meat. In the human gastrointestinal tract, the bacterium triggers campylobacteriosis that can progress to serious secondary disorders, including reactive arthritis, inflammatory bowel disease and Guillain-Barré syndrome. We recently discovered that C. jejuni serine protease HtrA disrupts intestinal epithelial barrier functions via cleavage of the tight and adherens junction components occludin, claudin-8 and E-cadherin. However, it is unknown whether epithelial damage is mediated by the secreted soluble enzyme, by HtrA contained in shed outer-membrane vesicles (OMVs) or by another mechanism that has yet to be identified. In the present study, we investigated whether soluble recombinant HtrA and/or purified OMVs induce junctional damage to polarized intestinal epithelial cells compared to live C. jejuni bacteria. By using electron and confocal immunofluorescence microscopy, we show that HtrA-expressing C. jejuni bacteria trigger efficient junctional cell damage, but not soluble purified HtrA or HtrA-containing OMVs, not even at high concentrations far exceeding physiological levels. Instead, we found that only bacteria with active protein biosynthesis effectively cleave junctional proteins, which is followed by paracellular transmigration of C. jejuni through the epithelial cell layer. These findings shed new light on the pathogenic activities of HtrA and virulence strategies of C. jejuni.

Gut microbiota CLA and IL-35 induction in macrophages through Gαq/11-mediated STAT1/4 pathway: an animal-based study

Gut microbiota/metabolites not only participate in the food and energy metabolism but also contribute to the host immune response and homeostasis. The alternation of gut microbiota/metabolites has been widely related to intestinal and extra-intestinal disorders such as intestinal bowel diseases (IBDs). Bactericidal substances from gut epithelial cells can regulate the composition of gut microbiota. However, the effects of regenerating protein 4 (REG4) (human)/(Reg4) (mice), a potentially bactericidal substance from gut epithelial cells, on the gut immune homeostasis maintain elusive. Here, we found that REG4/Reg4 is essential in maintaining gut immune homeostasis through REG4/Reg4 associated gut microbiota. Reg4 knockout (KO) mice were highly sensitive to DSS-mediated colitis, whereas human REG4 intestine epithelial cell transgenic (huREG4IECtg) mice exhibited more resistance to DSS-mediated colitis. Mechanistically, sequencing of gut microbiota and liquid chromatography-mass spectrometry showed that REG4/Reg4 could affect the composition of gut microbiota. REG4/Reg4 associated gut microbiota such as Lactobacillus could metabolize linoleic acid (LA) into conjugated linoleic acid (CLA). Immunoprecipitation and immunoblot showed that CLA could effectively promote the expression of IL-35 in macrophages through Gαq/11 mediated activation STAT1/4. Thus, our results demonstrate that REG4/Reg4 plays a critical role in maintaining gut immune homeostasis through CLA-mediated IL-35+ macrophages.

Postprandial Dysmetabolism and Its Medical Implications

An unbalanced diet increases the risk of developing a variety of chronic diseases and cancers, leading to higher morbidity and mortality rates worldwide. Low-grade systemic chronic inflammation mediated by the activation of the innate immune system is common to all these pathologies. Inflammation is a biological response of the body and a normal part of host defense to combat the effects of bacteria, viruses, toxins and macronutrients. However, when the innate immune system is constantly activated, it can promote the development of low-grade systemic chronic inflammation, which could play an important role in the development of chronic diseases and cancer. Since most chronic inflammatory diseases are associated with diet, a balanced healthy diet high in anti-inflammatory food components could prevent chronic diseases and cancer. The cells of the body's immune system produce chemokines and cytokines which can have pro-inflammatory and tumor-promoting as well as anti-inflammatory and tumor-fighting functions. A challenge in the future will be to assess whether polymorphisms in immune-related genes may play a role in promoting pro-inflammatory activity. Thanks to this duality, future research on immune regulation could focus on how innate immune cells can be modified to convert a pro-inflammatory and tumor-friendly microenvironment into an anti-inflammatory and anti-tumor one. This review describes inflammatory responses mediated by the innate immune system in various diseases such as hyperglycemia and/or hyperlipemia, obesity, type II diabetes, cardiovascular disease and cancer.