Changes in intestinal barrier protein expression and intestinal flora in a rat model of visceral hypersensitivity

Energy metabolism and the intestinal barrier: implications for understanding and managing intestinal diseases

The interplay between energy metabolism and the gut barrier is crucial for maintaining intestinal physiological homeostasis. Energy metabolism and the intestinal barrier perform distinct yet complementary roles that uphold intestinal ecological equilibrium. Disruptions in energy metabolism can compromise the integrity of the intestinal barrier; for example, inactivation of the AMPK pathway may lead to reduced expression of proteins associated with tight junctions. Conversely, impairment of the intestinal barrier can result in metabolic dysregulation, such as alterations in the gut microbiota that impede the production of short-chain fatty acids (SCFAs), which are essential substrates for energy metabolism. This disruption can affect energy production and modify the gut's hypoxic environment. Imbalances in these systems have been associated with the onset of various intestinal diseases. Research indicates that dietary interventions, such as a low FODMAP diet, can enhance the colonization of probiotics and improve the fermentation metabolism of SCFAs. Pharmacological strategies to elevate SCFA levels can activate the AMPK pathway and rectify abnormalities in energy metabolism. This review provides a comprehensive summary of recent advancements in elucidating the interactions between energy metabolism and the intestinal barrier.

A New Strategy for Dietary Nutrition to Improve Intestinal Homeostasis in Diarrheal Irritable Bowel Syndrome: A Perspective on Intestinal Flora and Intestinal Epithelial Interaction

BACKGROUND AND OBJECTIVES

Although a reasonable diet is essential for promoting human health, precise nutritional regulation presents a challenge for different physiological conditions. Irritable Bowel Syndrome (IBS) is characterized by recurrent abdominal pain and abnormal bowel habits, and diarrheal IBS (IBS-D) is the most common, seriously affecting patients' quality of life. Therefore, the implementation of precise nutritional interventions for IBS-D has become an urgent challenge in the fields of nutrition and food science. IBS-D intestinal homeostatic imbalance involves intestinal flora disorganization and impaired intestinal epithelial barrier function. A familiar interaction is evident between intestinal flora and intestinal epithelial cells (IECs), which together maintain intestinal homeostasis and health. Dietary patterns, such as the Mediterranean diet, have been shown to regulate gut flora, which in turn improves the body's health by influencing the immune system, the hormonal system, and other metabolic pathways.

METHODS

This review summarized the relationship between intestinal flora, IECs, and IBS-D. It analyzed the mechanism behind IBS-D intestinal homeostatic imbalance by examining the interactions between intestinal flora and IECs, and proposed a precise dietary nutrient intervention strategy.

RESULTS AND CONCLUSION

This increases the understanding of the IBS-D-targeted regulation pathways and provides guidance for designing related nutritional intervention strategies.

Lactiplantibacillus plantarum Regulates Intestinal Physiology and Enteric Neurons in IBS through Microbial Tryptophan Metabolites

Irritable bowel syndrome (IBS) is a prevalent functional gastrointestinal disorder characterized by visceral pain and gut dysmotility. However, the specific mechanisms by which Lactobacillus strains relieve IBS remain unclear. Here, we screened Lactobacillus strains from traditional Chinese fermented foods with potential IBS-alleviating properties through in vitro and in vivo experiments. We demonstrated that Lactiplantibacillus plantarum D266 (Lp D266) administration effectively modulates intestinal peristalsis, enteric neurons, visceral hypersensitivity, colonic inflammation, gut barrier function, and mast cell activation. Additionally, Lp D266 shapes gut microbiota and enhances tryptophan (Trp) metabolism, thus activating the aryl hydrocarbon receptor (AhR) and subsequently enhancing IL-22 production to maintain gut homeostasis. Mechanistically, Lp D266 potentially modulates colonic physiology and enteric neurons by microbial tryptophan metabolites. Further, our study indicates that combining Lp D266 with Trp synergistically ameliorates IBS symptoms. Together, our experiments identify the therapeutic efficacy of tryptophan-catabolizing Lp D266 in regulating gut physiology and enteric neurons, providing new insights into the development of probiotic-mediated nutritional intervention for IBS management.

Global research states and trends of micro RNA in irritable bowel syndrome: a bibliometric analysis

Irritable bowel syndrome (IBS) is a common chronic gastrointestinal disorder, but its diagnosis and treatment remain obscure. Non-coding RNAs (ncRNAs), as potential biomarkers, have attracted increasing attention in digestive diseases. Here, we present a comprehensive research status, development trends, and valuable insights in this subject area. The literature search was performed using Web of Science Core Collection. VOSviewer 1.6.20, Citespace 6.2.R4, and Microsoft Excel 2021 were used for bibliometric analysis. A total of 124 articles were included in the analysis. Overall, publication patterns fluctuated. Globally, People's Republic of China, the USA, and Germany were the top three contributors of publications. Guangzhou University of Chinese Medicine, University of California, Mayo Clinic, and University of California, Los Angeles contributed the highest number of publications. The pathways and specific mechanisms by which ncRNAs regulate transcription and translation and thus regulate the pathophysiological processes of IBS are the main research hotspots in this field. We found that microRNA (miRNAs) are intricately involved in the regulation of key pathologies such as viscera sensitivity, intestinal permeability, intestinal mucosal barrier, immunoinflammatory response, and brain-gut axis in the IBS, and these topics have garnered significant attention in research community. Notably, microecological disorders are also associated with IBS pathogenesis, and ncRNA may play an important role in the interactions between host and intestinal flora. This is the first bibliometric study to comprehensively summarize the research hotspots and trends related to IBS and ncRNAs (especially miRNAs). Our findings will help understand the role of ncRNAs in IBS and provide guidance to future studies.

Activation of ASIC3/ERK pathway by paeoniflorin improves intestinal fluid metabolism and visceral sensitivity in slow transit constipated rats

Slow transit constipation (STC) is one of the most common gastrointestinal disorders in children and adults worldwide. Paeoniflorin (PF), a monoterpene glycoside compound extracted from the dried root of Paeonia lactiflora, has been found to alleviate STC, but the mechanisms of its effect remain unclear. The present study aimed to investigate the effects and mechanisms of PF on intestinal fluid metabolism and visceral sensitization in rats with compound diphenoxylate-induced STC. Based on the evaluation of the laxative effect, the abdominal withdrawal reflex test, enzyme-linked immunosorbent assay, quantitative real-time polymerase chain reaction, western blot, and immunohistochemistry were used to detect the visceral sensitivity, fluid metabolism-related proteins, and acid-sensitive ion channel 3/extracellular signal-regulated kinase (ASIC3/ERK) pathway-related molecules. PF treatment not only attenuated compound diphenoxylate-induced constipation symptoms and colonic pathological damage in rats but also ameliorated colonic fluid metabolic disorders and visceral sensitization abnormalities, as manifested by increased colonic goblet cell counts and mucin2 protein expression, decreased aquaporin3 protein expression, improved abdominal withdrawal reflex scores, reduced visceral pain threshold, upregulated serum 5-hydroxytryptamine, and downregulated vasoactive intestinal peptide levels. Furthermore, PF activated the colonic ASIC3/ERK pathway in STC rats, and ASIC3 inhibition partially counteracted PF's modulatory effects on intestinal fluid and visceral sensation. In conclusion, PF alleviated impaired intestinal fluid metabolism and abnormal visceral sensitization in STC rats and thus relieved their symptoms through activation of the ASIC3/ERK pathway.

Mechanism of Mulberry Leaves and Black Sesame in Alleviating Slow Transit Constipation Revealed by Multi-Omics Analysis

Traditional Chinese medicine (TCM) possesses the potential of providing good curative effects with no side effects for the effective management of slow transit constipation (STC), an intestinal disease characterized by colonic dyskinesia. Mulberry leaves (Morus alba L.) and black sesame (Sesamum indicum L.), referred to as SH, are processed and conditioned as per standardized protocols. SH has applications as food and medicine. Accordingly, we investigated the therapeutic potential of SH in alleviating STC. The analysis of SH composition identified a total of 504 compounds. The intervention with SH significantly improved intestinal motility, reduced the time for the first black stool, increased antioxidant activity, and enhanced water content, thereby effectively alleviating colon damage caused by STC. Transcriptome analysis revealed the SH in the treatment of STC related to SOD1, MUC2, and AQP1. The analysis of 16S rRNA gene sequences indicated notable differences in the abundance of 10 bacteria between the SH and model. Metabolomic analysis further revealed that SH supplementation increased the levels of nine metabolites associated with STC. Integrative analysis revealed that SH modulated amino acid metabolism, balanced intestinal flora, and targeted key genes (i.e., SOD1, MUC2, AQP1) to exert its effects. SH also inhibited the AQP1 expression and promoted SOD1 and MUC2 expression.

Delineation of the healthy rabbit duodenum by immunohistochemistry - A short communication

The duodenum acts as a vital organ that performs fundamental physiological functions like digestion and nutrient absorption. Situated in the lower abdomen, the duodenum is located between the stomach and the jejunum. Usually, the duodenum is divided into four anatomical portions. We here compare paraffin embedded and cryosections of the healthy rabbit duodenum for research purposes. This analysis evaluates the differential outcomes resulting from the application of these fixation methodologies in conjunction with immunohistochemical assays targeting extracellular matrix markers collagen I, collagen III, fibronectin, α-smooth muscle actin (α-SMA), and proliferation marker ki67 as well as inflammatory marker PAR-2. Subsequent recommendations are provided based on our findings. Furthermore, the advantage of an antigen retrieval step in immunohistochemical labelling of paraffin sections was demonstrated and confirmed with an isotype negative control. Basic classical histological stainings as HE, GT and elastin were also performed. Comparison of different stainings and labellings was performed in serial sections, showing that adjacent to the circular muscle of the duodenum, the connective tissue was composed of collagen I and fibronectin, while the artery and vein walls were predominantly α-SMA positive. Moreover, PAR-2 immunohistochemical staining was performed, where particularly a type of gland adjacent to Brunner's glands showed prominent PAR-2 positive areas, while the Brunner's glands themselves were PAR-2 negative. Proliferating ki67 positive cells facing the lumen were highly abundant in all kinds of glands except for the Brunner's glands. This effort serves to furnish the research community with reference imagery pertinent to scientists opting for the rabbit duodenum model. The diversity of staining techniques employed herein establishes a foundational repository of images, primed for comparative analysis against pathological conditions. Furthermore, these images hold the potential to illustrate inter-species variations. For instance, they can be juxtaposed against murine or rat intestinal tracts, or even offer insights into the human context.

Gut toxicity of polystyrene microplastics and polychlorinated biphenyls to Eisenia fetida: Single and co-exposure effects with a focus on links between gut bacteria and bacterial translocation stemming from gut barrier damage

Microplastics' (MPs) ability to sorb and transport polychlorinated biphenyls (PCBs) in soil ecosystems warrants significant attention. Although organisms mainly encounter pollutants through the gut, the combined pollution impact of MPs and PCBs on soil fauna gut toxicity remains incompletely understood. Consequently, this study examined the gut toxicity of polystyrene MPs (PS-MPs) and PCB126 on Eisenia fetida, emphasizing the links between gut bacteria and bacterial translocation instigated by gut barrier impairment. Our findings underscored that E. fetida could ingest PS-MPs, which mitigated the PCB126 accumulation in E. fetida by 9.43 %. Exposure to PCB126 inhibited the expression of gut tight junction (TJ) protein genes. Although the presence of PS-MPs attenuated this suppression, it didn't alleviate gut barrier damage and bacterial translocation in the co-exposure group. This group demonstrated a significantly increased level of gut bacterial load (BLT, ANOVA, p = 0.005 vs control group) and lipopolysaccharide-binding protein (LBP, ANOVA, all p < 0.001 vs control, PCB, and PS groups), both of which displayed significant positive correlations with antibacterial defense. Furthermore, exposure to PS-MPs and PCB126, particularly within the co-exposure group, results in a marked decline in the dispersal ability of gut bacteria. This leads to dysbiosis (Adonis, R2 = 0.294, p = 0.001), with remarkable signature taxa such as Janthinobacterium, Microbacterium and Pseudomonas, being implicated in gut barrier dysfunction. This research illuminates the mechanism of gut toxicity induced by PS-MPs and PCB126 combined pollution in earthworms, providing novel insights for the ecological risk assessment of soil.

Paracellular permeability and tight junction regulation in gut health and disease

Epithelial tight junctions define the paracellular permeability of the intestinal barrier. Molecules can cross the tight junctions via two distinct size-selective and charge-selective paracellular pathways: the pore pathway and the leak pathway. These can be distinguished by their selectivities and differential regulation by immune cells. However, permeability increases measured in most studies are secondary to epithelial damage, which allows non-selective flux via the unrestricted pathway. Restoration of increased unrestricted pathway permeability requires mucosal healing. By contrast, tight junction barrier loss can be reversed by targeted interventions. Specific approaches are needed to restore pore pathway or leak pathway permeability increases. Recent studies have used preclinical disease models to demonstrate the potential of pore pathway or leak pathway barrier restoration in disease. In this Review, we focus on the two paracellular flux pathways that are dependent on the tight junction. We discuss the latest evidence that highlights tight junction components, structures and regulatory mechanisms, their impact on gut health and disease, and opportunities for therapeutic intervention.

Seasonal differences in intestinal flora are related to rats' intestinal water metabolism

Many studies have reported obvious seasonal differences in the intestinal flora of rats, and this stable distribution of the seasonal flora helps in maintaining the normal physiological function of the host. However, the mechanism underlying these seasonal differences in intestinal flora remains unclear. To explore the correlation among seasonal factors and intestinal water metabolism and intestinal flora, 20 Sprague Dawley (SD) rats were divided into spring, summer, autumn, and winter groups. The environment for the four seasons was simulated using the Balanced Temperature and Humidity Control system. The intestinal water metabolism was evaluated by determining the intestinal transmission function, fecal water content, water content of colonic tissue, and the colonic expression levels of AQP3, AQP4, and AQP8. The composition and relative abundance of intestinal microflora in rats in each season were assessed through 16S rDNA amplifier sequencing, and the relationship between the dominant flora and intestinal water metabolism in each season was analyzed using Spearman correlation analysis. The high temperature and humidity season could lead to an increase in intestinal water metabolism and intestinal water content in rats, whereas the low temperature and humidity season could lead to a decrease, which was closely related to the change in microflora. To explore the molecular mechanism of seasonal changes in intestinal water metabolism, the concentration of colonic 5-HT, VIP, cAMP, and PKA associated with intestinal water metabolism in rats were also examined. Seasonal changes could affect the concentration of colonic 5-HT and VIP in rats, and then regulate AQPs through cAMP/PKA pathway to affect the intestinal water metabolism. These results suggest that seasonal factors affect the level of intestinal water metabolism in rats and result in seasonal differences in intestinal flora.

A Novel Strategy for Alzheimer's Disease Based on the Regulatory Effect of Amyloid-β on Gut Flora

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases worldwide. The accumulation of amyloid-β (Aβ) protein and plaque formation in the brain are two major causes of AD. Interestingly, growing evidence demonstrates that the gut flora can alleviate AD by affecting amyloid production and metabolism. However, the underlying mechanism remains largely unknown. This review will discuss the possible association between the gut flora and Aβ in an attempt to provide novel therapeutic directions for AD treatment based on the regulatory effect of Aβ on the gut flora.

Global research progress of visceral hypersensitivity and irritable bowel syndrome: bibliometrics and visualized analysis

Background: Irritable bowel syndrome (IBS) is a group of functional intestinal disorders characterized by abdominal pain, bloating, and changes in bowel habits, and/or stool characteristics. Recent studies have shown that there has been a significant advancement in the study of visceral hypersensitivity in IBS. Through the use of bibliometrics, this study aims to provide a comprehensive overview of the knowledge structure and research hotpots of visceral hypersensitivity in IBS. Methods: Publications related to visceral hypersensitivity in IBS from 2012 to 2022 were searched on the web of science core collection (WoSCC) database. CiteSpace.6.1. R2 and Vosviewer 1.6.17 were used to perform bibliometric analysis. Results: A total of 974 articles led by China and the United States from 52 countries were included. Over the past decade, the number of articles on visceral hypersensitivity and IBS has steadily increased year by year. China, the United States, and Belgium are the main countries in this field. Univ Oklahoma, Univ Gothenburg, and Zhejiang University are the main research institutions. Simren, Magnus, Greenwood-van meerveld, Beverley, and Tack, Jan are the most published authors in this research field. The research on the causes, genes, and pathways involved in visceral hypersensitivity in IBS and the mechanism of IBS are the main topics and hotspots in this field. This study also found that gut microbiota may be related to the occurrence of visceral hypersensitivity, and probiotics may be a new method for the treatment of visceral hypersensitivity and pain, which may become a new direction for research in this field. Conclusion: This is the first bibliometric study to comprehensively summarize the research trends and developments of visceral hypersensitivity in IBS. This information provides the research frontier and hot topics in this field in recent years, which will provide a reference for scholars studying this field.

Seabuckthorn polysaccharide combined with astragalus polysaccharide ameliorate alcoholic fatty liver by regulating intestinal flora

Background

At present, the incidence of alcoholic fatty liver disease (AFLD) is increasing year by year, and numerous studies have confirmed that liver diseases are closely related to intestinal flora. Seabuckthorn and Astragalus membranaceus, as traditional Chinese medicine (TCM) with the homology of medicine and food, have good liver protection, and their polysaccharides can regulate the intestinal flora. Here, we studied the effects of HRP, APS and the combination of the two polysaccharides on the intestinal flora of AFLD mice, which provided scientific basis for the treatment of AFLD with the two polysaccharides.

Materials and methods

Thirty Kunming (KM) mice were randomly divided into the control group (Con), the model group (Mod), the HRP treatment group (HRP), the APS treatment group (APS), and HRP+APS treatment group (HRP+APS), with six mice in each group. The AFLD model was constructed by continuous intragastric administration of 42% vol Niulanshan ethanol solution for 28 days, and the mice in each polysaccharide group were given corresponding drugs. The levels of AST, ALT, TC and TG in serum of mice were measured. 16S rRNA amplicon sequencing technique was used to determine the diversity and richness of intestinal flora, and the relative abundance of intestinal flora at phylum level and genus level of the mice in each group.

Results

HRP, APS and HRP+APS could reduce the serum levels of AST, ALT, TC and TG in mice. In addition, HRP, APS and HRP + APS restored the diversity, relative abundance and community structure of intestinal mucosa bacteria in AFLD mice to a certain extent. Specifically, HRP, APS and HRP+APS remarkably decreased the ratio of Firmicutes to Bacteroidetes, and ultimately increased the abundance of beneficial bacteria and reduced the abundance of pathogenic bacteria.

Conclusion

HRP, APS, and HRP+APS can improve the intestinal microecology of AFLD model mice, alleviate liver injury, and maintain normal intestinal function in different degrees.