The colon: from banal to brilliant

Deloyers procedure compared to ileorectal anastomosis as restoration techniques of bowel continuity after extended left colon resection

BACKGROUND

Restoration of bowel continuity after left extended colectomy may be challenging because the remaining colon may not reach the rectal stump without tension to perform a safe anastomosis. Performing a total colectomy with ileorectal anastomosis (IRA) is an option, but the quality of life can be significantly impaired due to loose stools and an increase in bowel frequency. In contrast, the preservation of the right colon and ileocaecal valve in the Deloyers procedure (DP) might ensure a better stool consistency and bowel transit, and therefore a superior quality of life.

MATERIALS AND METHODS

A transverse study comparing patients that underwent DP versus patients with an IRA was performed. Postoperative morbidity, mortality, functional outcomes, and quality of life were analysed between groups. Quality of life after the surgical procedure was assessed with the SF-36 V2® health survey.

RESULTS

A total of 16 patients with DP and 32 with IRA were included. The groups had similar demographic characteristics concerning age, sex, body mass index, ASA classification, diagnosis and Charlson comorbidity index. The median follow-up was 55 months for DP and 99 months for IRA. Postoperative complications were similar in both groups. Patients in the DP group had fewer bowel movements (P = 0.01), tenesmus (P = 0.04) and use of loperamide (P = 0.03). DP patients achieved better scores in physical pain (P = 0.02) and general health (P < 0.01) than IRA patients.

CONCLUSIONS

DP for intestinal continuity restoration after extended left colon resection is a safe and feasible alternative, possibly achieving better functional outcomes and quality-of-life compared to IRA.

Oral Nanomedicines for siRNA Delivery to Treat Inflammatory Bowel Disease

RNA interference (RNAi) therapies have significant potential for the treatment of inflammatory bowel diseases (IBD). Although administering small interfering RNA (siRNA) via an oral route is desirable, various hurdles including physicochemical, mucus, and cellular uptake barriers of the gastrointestinal tract (GIT) impede both the delivery of siRNA to the target site and the action of siRNA drugs at the target site. In this review, we first discuss various physicochemical and biological barriers in the GI tract. Furthermore, we present recent strategies and the progress of oral siRNA delivery strategies to treat IBD. Finally, we consider the challenges faced in the use of these strategies and future directions of oral siRNA delivery strategies.

Mechanobiology of Colorectal Cancer

Simple Summary

It is well documented that colorectal cancer (CRC) is the third most common cancer type, responsible for high mortality in developed countries, resulting in a high socio-economic impact. Several biochemical and gene expression pathways explaining the manifestation of this cancer in humans have already been identified. However, explanations for some of the related biophysical mechanisms and their influence on CRC remain elusive. In CRC, biophysics and medical research have already revealed the importance of studying the effects of the stiffness and viscoelasticity of the substrate on cells, as well as the effect of the shear stress of blood and lymphatic vessels on the behavior of cells and tissues. A deeper understanding of the relationship between the biophysical cues and biochemical signals could be advantageous to develop new diagnostic techniques and therapeutic strategies. Being a disease with a high mortality rate, it becomes crucial to dedicate efforts to finding effective, alternative therapeutic strategies.

Abstract

In this review, the mechanobiology of colorectal cancer (CRC) are discussed. Mechanotransduction of CRC is addressed considering the relationship of several biophysical cues and biochemical pathways. Mechanobiology is focused on considering how it may influence epithelial cells in terms of motility, morphometric changes, intravasation, circulation, extravasation, and metastization in CRC development. The roles of the tumor microenvironment, ECM, and stroma are also discussed, taking into account the influence of alterations and surface modifications on mechanical properties and their impact on epithelial cells and CRC progression. The role of cancer-associated fibroblasts and the impact of flow shear stress is addressed in terms of how it affects CRC metastization. Finally, some insights concerning how the knowledge of biophysical mechanisms may contribute to the development of new therapeutic strategies and targeting molecules and how mechanical changes of the microenvironment play a role in CRC disease are presented.

Goblet cell LRRC26 regulates BK channel activation and protects against colitis in mice

Goblet cells (GCs) are specialized cells of the intestinal epithelium contributing critically to mucosal homeostasis. One of the functions of GCs is to produce and secrete MUC2, the mucin that forms the scaffold of the intestinal mucus layer coating the epithelium and separates the luminal pathogens and commensal microbiota from the host tissues. Although a variety of ion channels and transporters are thought to impact on MUC2 secretion, the specific cellular mechanisms that regulate GC function remain incompletely understood. Previously, we demonstrated that leucine-rich repeat-containing protein 26 (LRRC26), a known regulatory subunit of the Ca²⁺-and voltage-activated K⁺ channel (BK channel), localizes specifically to secretory cells within the intestinal tract. Here, utilizing a mouse model in which MUC2 is fluorescently tagged, thereby allowing visualization of single GCs in intact colonic crypts, we show that murine colonic GCs have functional LRRC26-associated BK channels. In the absence of LRRC26, BK channels are present in GCs, but are not activated at physiological conditions. In contrast, all tested MUC2^- cells completely lacked BK channels. Moreover, LRRC26-associated BK channels underlie the BK channel contribution to the resting transepithelial current across mouse distal colonic mucosa. Genetic ablation of either LRRC26 or BK pore-forming α-subunit in mice results in a dramatically enhanced susceptibility to colitis induced by dextran sodium sulfate. These results demonstrate that normal potassium flux through LRRC26-associated BK channels in GCs has protective effects against colitis in mice.

Drug Disposition in the Lower Gastrointestinal Tract: Targeting and Monitoring

The increasing prevalence of colonic diseases calls for a better understanding of the various colonic drug absorption barriers of colon-targeted formulations, and for reliable in vitro tools that accurately predict local drug disposition. In vivo relevant incubation conditions have been shown to better capture the composition of the limited colonic fluid and have resulted in relevant degradation and dissolution kinetics of drugs and formulations. Furthermore, drug hurdles such as efflux transporters and metabolising enzymes, and the presence of mucus and microbiome are slowly integrated into drug stability- and permeation assays. Traditionally, the well characterized Caco-2 cell line and the Ussing chamber technique are used to assess the absorption characteristics of small drug molecules. Recently, various stem cell-derived intestinal systems have emerged, closely mimicking epithelial physiology. Models that can assess microbiome-mediated drug metabolism or enable coculturing of gut microbiome with epithelial cells are also increasingly explored. Here we provide a comprehensive overview of the colonic physiology in relation to drug absorption, and review colon-targeting formulation strategies and in vitro tools to characterize colonic drug disposition.

Association of oral dysbiosis with oral cancer development

Oral squamous cell carcinoma (OSCC) is the leading cause of mortality for oral cancer. Numerous risk factors mainly related to unhealthy habits and responsible for chronic inflammation and infections have been recognized as predisposing factors for oral carcinogenesis. Recently, even microbiota alterations have been associated with the development of human cancers. In particular, some specific bacterial strains have been recognized and strongly associated with oral cancer development (Capnocytophaga gingivalis, Fusobacterium spp., Streptococcus spp., Peptostreptococcus spp., Porphyromonas gingivalis and Prevotella spp.). Several hypotheses have been proposed to explain how the oral microbiota could be involved in cancer pathogenesis by mainly paying attention to chronic inflammation, microbial synthesis of cancerogenic substances, and alteration of epithelial barrier integrity. Based on knowledge of the carcinogenic effects of dysbiosis, it was recently suggested that probiotics may have anti-tumoral activity. Nevertheless, few data exist with regard to probiotic effects on oral cancer. On this basis, the association between the development of oral cancer and oral dysbiosis is discussed focusing attention on the potential benefits of probiotics administration in cancer prevention.

Systematic evaluation of the gut microbiome of swamp eel (Monopterus albus) by 16S rRNA gene sequencing

Background

The swamp eel (Monopterus albus) is a commercially important farmed species in China. The dysbiosis and homeostasis of gut microbiota has been suggested to be associated with the swamp eel’s disease pathogenesis and food digestion. Although the contributions of gut microbiome in fish growth and health has been increasingly recognized, little is known about the microbial community in the intestine of the swamp eel (Monopterus albus).

Methods

The intestinal microbiomes of the five distinct gut sections (midgut content and mucosa, hindgut content and mucosa, and stools) of swamp eel were compared using Illumina MiSeq sequencing of the bacterial 16S rRNA gene sequence and statistical analysis.

Results

The results showed that the number of observed OTUs in the intestine decreased proximally to distally. Principal coordinate analysis revealed significant separations among samples from different gut sections. There were 54 core OTUs shared by all gut sections and 36 of these core OTUs varied significantly in their abundances. Additionally, we discovered 66 section-specific enriched KEGG pathways. These section-specific enriched microbial taxa (e.g., Bacillus, Lactobacillus) and potential function capacities (e.g., amino acid metabolism, carbohydrate metabolism) might play vital roles in nutrient metabolism, immune modulation and host-microbe interactions of the swamp eel.

Conclusions

Our results showed that microbial diversity, composition and function capacity varied substantially across different gut sections. The gut section-specific enriched core microbial taxa and function capacities may perform important roles in swamp eel’s nutrient metabolism, immune modulation, and host-microbe interactions. This study should provide insights into the gut microbiome of the swamp eel.

Intestinal Permeability and Drug Absorption: Predictive Experimental, Computational and In Vivo Approaches

The main objective of this review is to discuss recent advancements in the overall investigation and in vivo prediction of drug absorption. The intestinal permeability of an orally administered drug (given the value P_eff) has been widely used to determine the rate and extent of the drug’s intestinal absorption (F_abs) in humans. Preclinical gastrointestinal (GI) absorption models are currently in demand for the pharmaceutical development of novel dosage forms and new drug products. However, there is a strong need to improve our understanding of the interplay between pharmaceutical, biopharmaceutical, biochemical, and physiological factors when predicting F_abs and bioavailability. Currently, our knowledge of GI secretion, GI motility, and regional intestinal permeability, in both healthy subjects and patients with GI diseases, is limited by the relative inaccessibility of some intestinal segments of the human GI tract. In particular, our understanding of the complex and highly dynamic physiology of the region from the mid-jejunum to the sigmoid colon could be significantly improved. One approach to the assessment of intestinal permeability is to use animal models that allow these intestinal regions to be investigated in detail and then to compare the results with those from simple human permeability models such as cell cultures. Investigation of intestinal drug permeation processes is a crucial biopharmaceutical step in the development of oral pharmaceutical products. The determination of the intestinal P_eff for a specific drug is dependent on the technique, model, and conditions applied, and is influenced by multiple interactions between the drug molecule and the biological membranes.

MRI of the Colon in the Pharmaceutical Field: The Future before us

Oral solid drug formulation is the most common route for administration and it is vital to increase knowledge of the gastrointestinal physiological environment to understand dissolution and absorption processes and to develop reliable biorelevant in vitro tools. In particular, colon targeted drug formulations have raised the attention of pharmaceutical scientists because of the great potential of colonic drug delivery. However, the distal bowel is still a relatively understudied part of the gastrointestinal tract. Recently, magnetic resonance imaging (MRI) has been gaining an emerging role in studying the colon. This article provides a comprehensive; contemporary review of the literature on luminal MRI of the colonic environment of the last 15 years with specific focus on colon physiological dimensions; motility; chyme and fluids; transit and luminal flow. The work reviewed provides novel physiological insight that will have a profound impact on our understanding of the colonic environment for drug delivery and absorption and will ultimately help to raise the in vitro/in vivo relevance of computer simulations and bench models.

Occult blood in faeces is associated with all-cause and non-colorectal cancer mortality

OBJECTIVE

An association between detectable faecal haemoglobin (f-Hb) and both the risk of death from colorectal cancer (CRC) and all-cause mortality has been reported. We set out to confirm or refute this observation in a UK population and to explore the association between f-Hb, as indicated by a positive guaiac faecal occult blood test (gFOBT) result, and different causes of death.

DESIGN

All individuals (134 192) who participated in gFOBT screening in Tayside, Scotland between 29/03/2000 and 29/03/2016 were studied by linking their test result (positive or negative) with mortality data from the National Records of Scotland database and following to 30/03/2016.

RESULTS

Those with a positive test result (n=2714) had a higher risk of dying than those with a negative result, from CRC: HR 7.79 (95% CI 6.13 to 9.89), p<0.0001, (adjusted for, gender, age, deprivation quintile and medication that can cause bleeding) and all non-CRC causes: HR 1.58 (95% CI 1.45 to 1.73), p<0·0001.· In addition, f-Hb detectable by gFOBT was significantly associated with increased risk of dying from circulatory disease, respiratory disease, digestive diseases (excluding CRC), neuropsychological disease, blood and endocrine disease and non-CRC.

CONCLUSION

The presence of detectable f-Hb is associated with increased risk of death from a wide range of causes.

The relation of fetal colon and rectum diameters with labor in healthy late-third trimester pregnancies

OBJECTIVE

To investigate the associations of fetal colon-rectum diameters with labor and fetal distress or meconium passage in healthy pregnancies in the late 3rd trimester.

STUDY DESIGN

A total of 162 healthy, singleton pregnant women at ≥36^0/7 weeks who were in the latent-phase of labor (n = 69) or those not in labor (n = 93, controls) at the time of ultrasound examination were enrolled. Fetal colon (ascending, transverse, descending, sigmoid) and rectum diameters, Doppler indices of materno-fetal vessels were measured. Data were analyzed according to the mode of delivery.

RESULTS

Fetal colon-rectum diameters were smaller in women in labor compared to controls (p = 0.001). Positive correlations were observed between fetal colon-rectum diameters and interval between ultrasound and labor onset in the control group except for those who had scheduled cesarean sections (C/S) (p = 0.001). Similar colon-rectum measurements were obtained in fetuses delivered via cesarean section due to fetal distress or to other indications (p > 0.05). In women who had uterine contractions during ultrasound examination; later delivered by vaginal route, no association was observed between Apgar scores and colon-rectum diameters during latent-phase (p > 0.05), and also there were significant positive correlations between different segments of colon-rectum diameters and duration of neonatal meconium passage (p < 0.05).

CONCLUSION

Fetal colon and rectum diameters are smaller during labor and the measurements tend to diminish as the labor approaches, but do not indicate fetal distress.

Microbiota, Epithelium, Inflammation, and TGF-β Signaling: An Intricate Interaction in Oncogenesis

Microbiota has been widely considered to play a critical role in human carcinogenesis. Recent evidence demonstrated that microbiota, epithelial barrier and inflammation has made up a tightly interdependent triangle during the process of carcinogenesis. Hence, we discussed the triangle relationship of microbiota dysbiosis, epithelial barrier dysfunction and dysregulated immune responses to elucidate the mechanisms by which microbiota induces carcinogenesis, especially highlighting the reciprocal crosstalk between transforming growth factor-β signaling and every side of the tumorigenic triangle. This sophisticated interaction will provide insight into the basic mechanisms of carcinogenesis and may bring new hope to cancer prevention and therapeutic intervention.

Food contact materials and gut health: Implications for toxicity assessment and relevance of high molecular weight migrants

Gut health is determined by an intact epithelial barrier and balanced gut microbiota, both involved in the regulation of immune responses in the gut. Disruption of this system contributes to the etiology of various non-communicable diseases, including intestinal, metabolic, and autoimmune disorders. Studies suggest that some direct food additives, but also some food contaminants, such as pesticide residues and substances migrating from food contact materials (FCMs), may adversely affect the gut barrier or gut microbiota. Here, we focus on gut-related effects of FCM-relevant substances (e.g. surfactants, N-ring containing substances, nanoparticles, and antimicrobials) and show that gut health is an underappreciated target in the toxicity assessment of FCMs. Understanding FCMs' impact on gut health requires more attention to ensure safety and prevent gut-related chronic diseases. Our review further points to the existence of large population subgroups with an increased intestinal permeability; this may lead to higher uptake of compounds of not only low (<1000 Da) but also high (>1000 Da) molecular weight. We discuss the potential toxicological relevance of high molecular weight compounds in the gut and suggest that the scientific justification for the application of a molecular weight-based cut-off in risk assessment of FCMs should be reevaluated.

Reelin protects from colon pathology by maintaining the intestinal barrier integrity and repressing tumorigenic genes

We previously reported that reelin, an extracellular matrix protein first known for its key role in neuronal migration, reduces the susceptibility to dextran sulphate sodium (DSS)-colitis. The aim of the current study was to determine whether reelin protects from colorectal cancer and how reelin defends from colon pathology. In the colon of wild-type and of mice lacking reelin (reeler mice) we have analysed the: i) epithelium cell renewal processes, ii) morphology, iii) Sox9, Cdx2, Smad5, Cyclin D1, IL-6 and IFNγ mRNA abundance in DSS-treated and untreated mice, and iv) development of azoxymethane/DSS-induced colorectal cancer, using histological and real time-PCR methodologies. The reeler mutation increases colitis-associated tumorigenesis, with increased tumours number and size. It also impairs the intestinal barrier because it reduces cell proliferation, migration, differentiation and apoptosis; decreases the number and maturation of goblet cells, and expands the intercellular space of the desmosomes. The intestinal barrier impairment might explain the increased susceptibility to colon pathology exhibited by the reeler mice and is at least mediated by the down-regulation of Sox9 and Cdx2. In response to DSS-colitis, the reeler colon increases the mRNA abundance of IL-6, Smad5 and Cyclin D1 and decreases that of IFNγ, conditions that might result in the increased colitis-associated tumorigenesis found in the reeler mice. In conclusion, the results highlight a role for reelin in maintaining intestinal epithelial cell homeostasis and providing resistance against colon pathology.

Microbiota and pathogen 'pas de deux': setting up and breaking down barriers to intestinal infection

The gut microbiota plays essential roles in human health and disease. In this review, we focus on the role of the intestinal microbiota in promoting resistance to infection by bacterial pathogens as well as how pathogens overcome this barrier. We discuss how the resident microbiota restricts growth and colonization of invading pathogens by limiting availability of nutrients and through generation of a hostile environment. Additionally, we examine how microbiota-derived signaling molecules interfere with bacterial virulence. In turn, we discuss how pathogens exploit non-competitive metabolites to replicate in vivo as well as to precisely control virulence and cause disease. This bacterial two step of creating and overcoming challenges important in preventing and establishing infection highlights the complexities of elucidating interactions between the commensal bacteria and pathogens. Better understanding of microbiota-pathogen interplay will have significant implications for developing novel therapeutics to treat infectious diseases.

Commensal 'trail of bread crumbs' provide pathogens with a map to the intestinal landscape

Growth of a microorganism in a host is essential for infection, and bacterial pathogens have evolved to utilize specific metabolites to enhance replication in vivo. Now, emerging data demonstrate that pathogens rely on microbiota-derived metabolites as a form of bacterial-bacterial communication to gain information about location within a host and modify virulence gene expression accordingly. Thus, metabolite-sensing is critical for pathogens to establish infection. Here, we highlight recent examples of how the foodborne pathogen enterohemorrhagic Escherichia coli O157:H7 (EHEC) exploits microbiota-derived metabolites to recognize the host intestinal environment and control gene expression that results in controlled expression of virulence traits.