Enterocytes’ tight junctions: From molecules to diseases

Tight junctions (TJs) are structures between cells where cells appear in the closest possible contact. They are responsible for sealing compartments when epithelial sheets are generated. They regulate the permeability of ions, (macro) molecules and cells via the paracellular pathway. Their structure at the electron microscopic level has been well known since the 1970s; however, only recently has their macromolecular composition been revealed. This review first examines the major macromolecular components of the TJs (occludin, claudins, junctional adhesion molecule and tricellulin) and then the associated macromolecules at the intracellular plaque [zonula occludens (ZO)-1, ZO-2, ZO-3, AF-6, cingulin, 7H6]. Emphasis is given to their interactions in order to begin to understand the mode of assembly of TJs. The functional significance of TJs is detailed and several mechanisms and factors involved are discussed briefly. Emphasis is given to the role of intestinal TJs and the alterations observed or speculated in diverse disease states. Specifically, intestinal TJs may exert a pathogenetic role in intestinal (inflammatory bowel disease, celiac disease) and extraintestinal diseases (diabetes type 1, food allergies, autoimmune diseases). Additionally, intestinal TJs may be secondarily disrupted during the course of diverse diseases, subsequently allowing the bacterial translocation phenomenon and promoting the systemic inflammatory response, which is often associated with clinical deterioration. The major questions in the field are highlighted.

Encapsulated islets transplantation: Past, present and future

Islet transplantation could become an ideal treatment for severe diabetes to prevent hypoglycemia shock and irreversible diabetic complications, once some of the major and unresolved obstacles are overcome, including limited donor supplies and side effects caused by permanent immunosuppressant use. Approximately 30 years ago, some groups succeeded in improving the blood glucose of diabetic animals by transplanting encapsulated islets with semi-permeable membranes consisting of polymer. A semi-permeable membrane protects both the inner islets from mechanical stress and the recipient's immune system (both cellular and humoral immunities), while allowing bidirectional diffusion of nutrients, oxygen, glucose, hormones and wastes, i.e., immune-isolation. This device, which enables immune-isolation, is called encapsulated islets or bio-artificial pancreas. Encapsulation with a semi-permeable membrane can provide some advantages: (1) this device protects transplanted cells from the recipient's immunity even if the xenogeneic islets (from large animals such as pig) or insulin-producing cells are derived from cells that have the potential for differentiation (some kinds of stem cells). In other words, the encapsulation technique can resolve the problem of limited donor supplies; and (2) encapsulation can reduce or prevent chronic administration of immunosuppressants and, therefore, important side effects otherwise induced by immunosuppressants. And now, many novel encapsulated islet systems have been developed and are being prepared for testing in a clinical setting.

Therapeutic potential of curcumin in gastrointestinal diseases

Curcumin, also known as diferuloylmethane, is derived from the plant Curcuma longa and is the active ingredient of the spice turmeric. The therapeutic activities of curcumin for a wide variety of diseases such as diabetes, allergies, arthritis and other chronic and inflammatory diseases have been known for a long time. More recently, curcumin’s therapeutic potential for preventing and treating various cancers is being recognized. As curcumin’s therapeutic promise is being explored more systematically in various diseases, it has become clear that, due to its increased bioavailability in the gastrointestinal tract, curcumin may be particularly suited to be developed to treat gastrointestinal diseases. This review summarizes some of the current literature of curcumin’s anti-inflammatory, anti-oxidant and anti-cancer potential in inflammatory bowel diseases, hepatic fibrosis and gastrointestinal cancers.

Mesenteric ischemia: Pathogenesis and challenging diagnostic and therapeutic modalities

Mesenteric ischemia (MI) is an uncommon medical condition with high mortality rates. ΜΙ includes inadequate blood supply, inflammatory injury and eventually necrosis of the bowel wall. The disease can be divided into acute and chronic MI (CMI), with the first being subdivided into four categories. Therefore, acute MI (AMI) can occur as a result of arterial embolism, arterial thrombosis, mesenteric venous thrombosis and non-occlusive causes. Bowel damage is in proportion to the mesenteric blood flow decrease and may vary from minimum lesions, due to reversible ischemia, to transmural injury, with subsequent necrosis and perforation. CMI is associated to diffuse atherosclerotic disease in more than 95% of cases, with all major mesenteric arteries presenting stenosis or occlusion. Because of a lack of specific signs or due to its sometime quiet presentation, this condition is frequently diagnosed only at an advanced stage. Computed tomography (CT) imaging and CT angiography contribute to differential diagnosis and management of AMI. Angiography is also the criterion standard for CMI, with mesenteric duplex ultrasonography and magnetic resonance angiography also being of great importance. Therapeutic approach of MI includes both medical and surgical treatment. Surgical procedures include restoration of the blood flow with arteriotomy, endarterectomy or anterograde bypass, while resection of necrotic bowel is always implemented. The aim of this review was to evaluate the results of surgical treatment for MI and to present the recent literature in order to provide an update on the current concepts of surgical management of the disease. Mesh words selected include MI, diagnostic approach and therapeutic management.

Role of gamma-delta T cells in liver inflammation and fibrosis

Conventional adaptive T cell responses contribute to liver inflammation and fibrogenesis, especially in chronic viral infections and autoimmune hepatitis. However, the role of unconventional gamma-delta (γδ) T cells in liver diseases is less clear. In the past two decades, accumulating evidence revealed that γδ T cell numbers remarkably increase in the liver upon various inflammatory conditions in mice and humans. More recent studies demonstrated that the functional effect of γδ T cells on liver disease progression depends on the subsets involved, which can be identified by the expression of distinct T cell receptor chains and of specific cytokines. Fascinatingly, γδ T cells may have protective as well as pathogenic functions in liver diseases. Interferon γ-producing γδ T cells, for example, induce apoptosis in hepatocytes but also in hepatic tumor cells; while interleukin-17-expressing γδ T cells can downregulate pathogenic effector functions of other immune cells and can promote apoptosis of fibrogenic stellate cells. However, the results obtained in human liver disease as well as murine models are not fully conclusive at present, and the effects of γδ T cells on the outcome of liver disease might vary dependent on etiology and stage of disease. Further definitions of the γδ T cell subsets involved in acute and chronic liver inflammation, as well as their effector cytokines might uncover whether interference with γδ T cells could be a useful target for the treatment of liver disease.

Pancreatic cancer diagnosis by free and exosomal miRNA

Patients with pancreatic adenocarcinoma (PaCa) have a dismal prognosis. This is in part due to late diagnosis prohibiting surgical intervention, which provides the only curative option as PaCa are mostly chemo- and radiation resistance. Hope is raised on a reliable non-invasive/minimally invasive diagnosis that is still missing. Recently two diagnostic options are discussed, serum MicroRNA (miRNA) and serum exosomes. Serum miRNA can be free or vesicle-, particularly, exosomes-enclosed. This review will provide an overview on the current state of the diagnostic trials on free serum miRNA and proceed with an introduction of exosomes that use as a diagnostic tool in serum and other body fluids has not received sufficient attention, although serum exosome miRNA in combination with protein marker expression likely will increase the diagnostic and prognostic power. By their crosstalk with host cells, which includes binding-initiated signal transduction, as well as reprogramming target cells via the transfer of proteins, mRNA and miRNA exosomes are suggested to become a most powerful therapeutics. I will discuss which hurdles have still to be taken as well as the different modalities, which can be envisaged to make therapeutic use of exosomes. PaCa are known to most intensely crosstalk with the host as apparent by desmoplasia and frequent paraneoplastic syndromes. Thus, there is hope that the therapeutic application of exosomes brings about a major breakthrough.

Risk factors for osteoporosis in inflammatory bowel disease patients

Inflammatory bowel disease (IBD) patients exhibit higher risk for bone loss than the general population. The chronic inflammation causes a reduction in bone mineral density (BMD), which leads to osteopenia and osteoporosis. This article reviewed each risk factor for osteoporosis in IBD patients. Inflammation is one of the factors that contribute to osteoporosis in IBD patients, and the main system that is involved in bone loss is likely RANK/RANKL/osteoprotegerin. Smoking is a risk factor for bone loss and fractures, and many mechanisms have been proposed to explain this loss. Body composition also interferes in bone metabolism and increasing muscle mass may positively affect BMD. IBD patients frequently use corticosteroids, which stimulates osteoclastogenesis. IBD patients are also associated with vitamin D deficiency, which contributes to bone loss. However, infliximab therapy is associated with improvements in bone metabolism, but it is not clear whether the effects are because of inflammation improvement or infliximab use. Ulcerative colitis patients with proctocolectomy and ileal pouches and Crohn’s disease patients with ostomy are also at risk for bone loss, and these patients should be closely monitored.

Patterns of airway involvement in inflammatory bowel diseases

Extraintestinal manifestations occur commonly in inflammatory bowel diseases (IBD). Pulmonary manifestations (PM) of IBD may be divided in airway disorders, interstitial lung disorders, serositis, pulmonary vasculitis, necrobiotic nodules, drug-induced lung disease, thromboembolic lung disease and enteropulmonary fistulas. Pulmonary involvement may often be asymptomatic and detected solely on the basis of abnormal screening tests. The common embryonic origin of the intestine and the lungs from the primitive foregut, the co-existence of mucosa associated lymphoid tissue in both organs, autoimmunity, smoking and bacterial translocation from the colon to the lungs may all be involved in the pathogenesis of PM in IBD. PM are mainly detected by pulmonary function tests and high-resolution computed tomography. This review will focus on the involvement of the airways in the context of IBD, especially stenoses of the large airways, tracheobronchitis, bronchiectasis, bronchitis, mucoid impaction, bronchial granulomas, bronchiolitis, bronchiolitis obliterans syndrome and the co-existence of IBD with asthma, chronic obstructive pulmonary disease, sarcoidosis and a1-antitrypsin deficiency.

Acute pancreatitis in children and adolescents

In this Topic Highlight, the causes, diagnosis, and treatment of acute pancreatitis in children are discussed. Acute pancreatitis should be considered during the differential diagnosis of abdominal pain in children and requires prompt treatment because it may become life-threatening. The etiology, clinical manifestations, and course of acute pancreatitis in children are often different than in adults. Therefore, the specific features of acute pancreatitis in children must be considered. The etiology of acute pancreatitis in children is often drugs, infections, trauma, or anatomic abnormalities. Diagnosis is based on clinical symptoms (such as abdominal pain and vomiting), serum pancreatic enzyme levels, and imaging studies. Several scoring systems have been proposed for the assessment of severity, which is useful for selecting treatments and predicting prognosis. The basic pathogenesis of acute pancreatitis does not greatly differ between adults and children, and the treatments for adults and children are similar. In large part, our understanding of the pathology, optimal treatment, assessment of severity, and outcome of acute pancreatitis in children is taken from the adult literature. However, we often find that the common management of adult pancreatitis is difficult to apply to children. With advances in diagnostic techniques and treatment methods, severe acute pancreatitis in children is becoming better understood and more controllable.

Use of probiotics in the fight against Helicobacter pylori

After the discovery of Helicobacter pylori (H. pylori), and the evidence of its relationship with gastric diseases, antibiotic-based therapies were developed, which efficacy was however limited by antibiotic resistance and lack of patient compliance. A vaccine would overcome these drawbacks, but currently there is not any H. pylori vaccine licensed. In the frame of the studies aimed at finding alternative therapies or at increasing the efficacy of the current ones and/or reducing their side effects, the investigation on the use of probiotics plays an interesting role. In vitro and preclinical studies have shown the feasibility of this approach. Several clinical trials indicated that administration of probiotics can reduce the side effects of H. pylori eradication treatment, increasing tolerability, and often increases the overall efficacy. The results of these trials vary, likely reflecting the variety of probiotics assessed and that of the eradication treatment, as well as the differences in the geographic area that imply different H. pylori strains distribution, host susceptibility, and therapy efficacy. In conclusion, the use of probiotics appears promising as an adjuvant for the current H. pylori eradication treatment, though it still requires optimization.

Pathophysiological mechanisms linking obesity and esophageal adenocarcinoma

In recent decades there has been a dramatic rise in the incidence of esophageal adenocarcinoma (EAC) in the developed world. Over approximately the same period there has also been an increase in the prevalence of obesity. Obesity, especially visceral obesity, is an important independent risk factor for the development of gastro-esophageal reflux disease, Barrett's esophagus and EAC. Although the simplest explanation is that this mediated by the mechanical effects of abdominal obesity promoting gastro-esophageal reflux, the epidemiological data suggest that the EAC-promoting effects are independent of reflux. Several, not mutually exclusive, mechanisms have been implicated, which may have different effects at various points along the reflux-Barrett's-cancer pathway. These mechanisms include a reduction in the prevalence of Helicobacter pylori infection enhancing gastric acidity and possibly appetite by increasing gastric ghrelin secretion, induction of both low-grade systemic inflammation by factors secreted by adipose tissue and the metabolic syndrome with insulin-resistance. Obesity is associated with enhanced secretion of leptin and decreased secretion of adiponectin from adipose tissue and both increased leptin and decreased adiponectin have been shown to be independent risk factors for progression to EAC. Leptin and adiponectin have a set of mutually antagonistic actions on Barrett's cells which appear to influence the progression of malignant behaviour. At present no drugs are of proven benefit to prevent obesity associated EAC. Roux-en-Y reconstruction is the preferred bariatric surgical option for weight loss in patients with reflux. Statins and aspirin may have chemopreventative effects and are indicated for their circulatory benefits.

Treatment of Helicobacter pylori infection: Past, present and future

Helicobacter pylori (H. pylori) is a major human pathogen associated with significant morbidity and mortality. However, after decades of efforts, treatment of H. pylori remains a challenge for physicians, as there is no universally effective regimen. Due to the rising prevalence of antimicrobial resistance, mainly to clarithromycin, efficacy of standard triple therapies has declined to unacceptably low levels in most parts of the world. Novel regimens, specifically experimented to improve the therapeutic outcome against antibiotic-resistant H. pylori strains, are now recommended as first-line empirical treatment options providing high efficacy (reportedly > 90% in intention to treat analysis) even in high clarithromycin resistance settings. These include the bismuth quadruple, concomitant, sequential and hybrid therapies. Due to the rapid development of quinolone resistance, levofloxacin-based regimens should be reserved as second-line/rescue options. Adjunct use of probiotics has been proposed in order to boost eradication rates and decrease occurrence of treatment-related side effects. Molecular testing methods are currently available for the characterization of H. pylori therapeutic susceptibility, including genotypic detection of macrolide resistance and evaluation of the cytochrome P450 2C19 status known to affect the metabolism of proton pump inhibitors. In the future, use of these techniques may allow for culture-free, non-invasive tailoring of therapy for H. pylori infection.

Intestinal microbiota: The explosive mixture at the origin of inflammatory bowel disease?

Inflammatory bowel diseases (IBDs), namely Crohn’s disease and ulcerative colitis, are lifelong chronic disorders arising from interactions among genetic, immunological and environmental factors. Although the origin of IBDs is closely linked to immune response alterations, which governs most medical decision-making, recent findings suggest that gut microbiota may be involved in IBD pathogenesis. Epidemiologic evidence and several studies have shown that a dysregulation of gut microbiota (i.e., dysbiosis) may trigger the onset of intestinal disorders such as IBDs. Animal and human investigations focusing on the microbiota-IBD relationship have suggested an altered balance of the intestinal microbial population in the active phase of IBD. Rigorous microbiota typing could, therefore, soon become part of a complete phenotypic analysis of IBD patients. Moreover, individual susceptibility and environmental triggers such as nutrition, medications, age or smoking could modify bacterial strains in the bowel habitat. Pharmacological manipulation of bowel microbiota is somewhat controversial. The employment of antibiotics, probiotics, prebiotics and synbiotics has been widely addressed in the literature worldwide, with the aim of obtaining positive results in a number of IBD patient settings, and determining the appropriate timing and modality of this intervention. Recently, novel treatments for IBDs, such as fecal microbiota transplantation, when accepted by patients, have shown promising results. Controlled studies are being designed. In the near future, new therapeutic strategies can be expected, with non-pathogenic or modified food organisms that can be genetically modified to exert anti-inflammatory properties.

Alterations of the gut microbiome and metabolome in alcoholic liver disease

Alcohol consumption is one of the leading causes of liver diseases and liver-related death worldwide. The gut is a habitat for billions of microorganisms which promotes metabolism and digestion in their symbiotic relationship with the host. Alterations of gut microbiome by alcohol consumption are referred to bacterial overgrowth, release of bacteria-derived products, and/or changed microbiota equilibrium. Alcohol consumption also perturbs the function of gastrointestinal mucosa and elicits a pathophysiological condition. These adverse effects caused by alcohol may ultimately result in a broad change of gastrointestinal luminal metabolites such as bile acids, short chain fatty acids, and branched chain amino acids. Gut microbiota alterations, metabolic changes produced in a dysbiotic intestinal environment, and the host factors are all critical contributors to the development and progression of alcoholic liver disease. This review summarizes recent findings of how alcohol-induced alterations of gut microbiota and metabolome, and discusses the mechanistic link between gastrointestinal dyshomeostasis and alcoholic liver injury.

Role of Helicobacter pylori infection in pathogenesis of gastric carcinoma

Gastric cancer (GC) is one of the most common carcinoma and the second leading cause of cancer-related deaths worldwide. Helicobacter pylori (H. pylori) infection causes a series of precancerous lesions like gastritis, atrophy, intestinal metaplasia and dysplasia, and is the strongest known risk factor for GC, as supported by epidemiological, preclinical and clinical studies. However, the mechanism of H. pylori developing gastric carcinoma has not been well defined. Among infected individuals, approximately 10% develop severe gastric lesions such as peptic ulcer disease, 1%-3% progresses to GC. The outcomes of H. pylori infection are determined by bacterial virulence, genetic polymorphism of hosts as well as environmental factors. It is important to gain further understanding of the pathogenesis of H. pylori infection for developing more effective treatments for this common but deadly malignancy. The recent findings on the bacterial virulence factors, effects of H. pylori on epithelial cells, genetic polymorphism of both the bacterium and its host, and the environmental factors for GC are discussed with focus on the role of H. pylori in gastric carcinogenesis in this review.

Intestinal barrier: Molecular pathways and modifiers

The gastrointestinal tract is frequently challenged by pathogens/antigens contained in food and water and the intestinal epithelium must be capable of rapid regeneration in the event of tissue damage. Disruption of the intestinal barrier leads to a number of immune-mediated diseases, including inflammatory bowel disease, food allergy, and celiac disease. The intestinal mucosa is composed of different types of epithelial cells in specific barrier functions. Epithelial cells control surface-associated bacterial populations without disrupting the intestinal microflora that is crucial for host health. They are also capable of modulating mucosal immune system, and are thus essential in maintaining homeostasis in the gut. Thus, the regulation of intestinal epithelial homeostasis is crucial for the maintenance of the structure of the mucosa and the defensive barrier functions. Recent studies have demonstrated that multiple molecular pathways are involved in the regulation of intestinal epithelial cell polarity. These include the Wnt, Notch, Hippo, transforming growth factor-β (TGF-β)/bone morphogenetic protein (BMP) and Hedgehog pathways, most of which were identified in lower organisms where they play important roles during embryogenesis. These pathways are also used in adult organisms to regulate multiple self-renewing organs. Understanding the interactions between these molecular mechanisms and intestinal barrier function will therefore provide important insight into the pathogenesis of intestinal-based immune-mediated diseases.

Pancreatitis-imaging approach

Pancreatitis is defined as the inflammation of the pancreas and considered the most common pancreatic disease in children and adults. Imaging plays a significant role in the diagnosis, severity assessment, recognition of complications and guiding therapeutic interventions. In the setting of pancreatitis, wider availability and good image quality make multi-detector contrast-enhanced computed tomography (MD-CECT) the most used imaging technique. However, magnetic resonance imaging (MRI) offers diagnostic capabilities similar to those of CT, with additional intrinsic advantages including lack of ionizing radiation and exquisite soft tissue characterization. This article reviews the proposed definitions of revised Atlanta classification for acute pancreatitis, illustrates a wide range of morphologic pancreatic parenchymal and associated peripancreatic changes for different types of acute pancreatitis. It also describes the spectrum of early and late chronic pancreatitis imaging findings and illustrates some of the less common types of chronic pancreatitis, with special emphasis on the role of CT and MRI.

Retroperitoneal cystic lymphangioma in an adult: A case report and review of the literature

Lymphangiomas are rare benign cystic tumors of the lymphatic system. Retroperitoneal lymphangiomas account for 1% of all lymphangiomas, and approximately 186 cases have been reported. They may clinically present as a palpable abdominal mass and can cause diagnostic dilemmas with other retroperitoneal cystic tumors, including those arising from the liver, kidney and pancreas. This report describes the rare case of a cystic retroperitoneal lymphangioma in a 54-year-old male patient. The lymphangioma had progressed to the point of inducing clinical symptoms of abdominal distention, abdominal pain, anorexia, fever, nausea and diarrhea. Radiological imaging revealed a large multiloculated cystic abdominal mass with enhancing septations involving the upper retroperitoneum and extending into the pelvis. Surgical removal of the cyst was accomplished without incident. A benign cystic retroperitoneal lymphangioma was diagnosed on histology and confirmed with immunohistochemical stains.

Upper gastrointestinal bleeding risk scores: Who, when and why?

Upper gastrointestinal bleeding (UGIB) remains a significant cause of hospital admission. In order to stratify patients according to the risk of the complications, such as rebleeding or death, and to predict the need of clinical intervention, several risk scores have been proposed and their use consistently recommended by international guidelines. The use of risk scoring systems in early assessment of patients suffering from UGIB may be useful to distinguish high-risks patients, who may need clinical intervention and hospitalization, from low risk patients with a lower chance of developing complications, in which management as outpatients can be considered. Although several scores have been published and validated for predicting different outcomes, the most frequently cited ones are the Rockall score and the Glasgow Blatchford score (GBS). While Rockall score, which incorporates clinical and endoscopic variables, has been validated to predict mortality, the GBS, which is based on clinical and laboratorial parameters, has been studied to predict the need of clinical intervention. Despite the advantages previously reported, their use in clinical decisions is still limited. This review describes the different risk scores used in the UGIB setting, highlights the most important research, explains why and when their use may be helpful, reflects on the problems that remain unresolved and guides future research with practical impact.

Promising biological therapies for ulcerative colitis: A review of the literature

Ulcerative colitis (UC) is a chronic lifelong condition characterized by alternating flare-ups and remission. There is no single known unifying cause, and the pathogenesis is multifactorial, with genetics, environmental factors, microbiota, and the immune system all playing roles. Current treatment modalities for UC include 5-aminosalicylates, corticosteroids, immunosuppressants (including purine antimetabolites, cyclosporine, and tacrolimus), and surgery. Therapeutic goals for UC are evolving. Medical treatment aims to induce remission and prevent relapse of disease activity. Infliximab, an anti-tumor necrosis factor (TNF)-α monoclonal antibody, is the first biological agent for the treatment of UC. Over the last decade, infliximab and adalimumab (anti-TNF-α agents) have been used for moderate to severe UC, and have been shown to be effective in inducing and maintaining remission. Recent studies have indicated that golimumab (another anti-TNF-α agent), tofacitinib (a Janus kinase inhibitor), and vedolizumab and etrolizumab (integrin antagonists), achieved good clinical remission and response rates in UC. Recently, golimumab and vedolizumab have been approved for UC by the United States Food and Drug Administration. Vedolizumab may be used as a first-line alternative to anti-TNF-α therapy in patients with an inadequate response to corticosteroids and/or immunosuppressants. Here, we provide updated information on various biological agents in the treatment of UC.

Management of acute severe ulcerative colitis

The management strategy of acute severe ulcerative colitis has evolved over the past decade from being entirely restricted to twin choices of intravenous steroids or colectomy to include colon rescue therapies like cyclosporin as well as infliximab. However it still remains a medical emergency requiring hospitalization and requires care from a multidisciplinary team comprising of a gastroenterologist and a colorectal surgeon. The frame shift in management has been the emphasis on time bound decision making with an attempt to curtail the mortality rate to below 1%. Intravenous corticosteroids are the mainstay of therapy. Response to steroids should be assessed at day 3 of admission and partial/non-responders should be considered for alternative medical therapy/surgery. Medical rescue therapies include intravenous cyclosporin and infliximab. Cyclosporin is administered in a dose of 2 mg/kg per day and infliximab is administered as a single dose intravenous infusion of 5 mg/kg. Approximately 75% patients have short term and 50% patients have long term response to cyclosporin. Long term response to cyclosporin is improved in patients who are thiopurine naïve and are started on thiopurines on day 7. Infliximab also has a response rate of approximately 70% in short term and 50% in long term. Both cyclosporin and infliximab are equally efficacious medical rescue therapies as demonstrated in a recent randomized control trial. Patients not responding to infliximab or cyclosporin should be considered for colectomy.

Starring role of toll-like receptor-4 activation in the gut-liver axis

Since the introduction of the term “gut-liver axis”, many studies have focused on the functional links of intestinal microbiota, barrier function and immune responses to liver physiology. Intestinal and extra-intestinal diseases alter microbiota composition and lead to dysbiosis, which aggravates impaired intestinal barrier function via increased lipopolysaccharide translocation. The subsequent increased passage of gut-derived product from the intestinal lumen to the organ wall and bloodstream affects gut motility and liver biology. The activation of the toll-like receptor 4 (TLR-4) likely plays a key role in both cases. This review analyzed the most recent literature on the gut-liver axis, with a particular focus on the role of TLR-4 activation. Findings that linked liver disease with dysbiosis are evaluated, and links between dysbiosis and alterations of intestinal permeability and motility are discussed. We also examine the mechanisms of translocated gut bacteria and/or the bacterial product activation of liver inflammation and fibrogenesis via activity on different hepatic cell types.

Effects of occupational stress on the gastrointestinal tract

The aim of this review is to provide a general overview of the relationship between occupational stress and gastrointestinal alterations. The International Labour Organization suggests occupational health includes psychological aspects to achieve mental well-being. However, the definition of health risks for an occupation includes biological, chemical, physical and ergonomic factors but does not address psychological stress or other affective disorders. Nevertheless, multiple investigations have studied occupational stress and its physiological consequences, focusing on specific risk groups and occupations considered stressful. Among the physiological effects of stress, gastrointestinal tract (GIT) alterations are highly prevalent. The relationship between occupational stress and GIT diseases is evident in everyday clinical practice; however, the usual strategy is to attack the effects but not the root of the problem. That is, in clinics, occupational stress is recognized as a source of GIT problems, but employers do not ascribe it enough importance as a risk factor, in general, and for gastrointestinal health, in particular. The identification, stratification, measurement and evaluation of stress and its associated corrective strategies, particularly for occupational stress, are important topics to address in the near future to establish the basis for considering stress as an important risk factor in occupational health.

Regulation of colon cancer recurrence and development of therapeutic strategies

Recurrence of colon cancer still remains a major issue which affects nearly 50% of patients treated by conventional therapeutics. Although the underlying causative factor(s) is not fully understood, development of drug-resistance has been associated with induction of cancer stem or stem-like cells (CSCs) which constitute a small sub-population of tumor cells known to be highly resistant to chemotherapy. In fact, the discovery of CSCs in a variety of tumors (including colon cancer) has changed the view of carcinogenesis and therapeutic strategies. Emerging reports have indicated that to improve patient outcomes, conventional anticancer therapies should be replaced with specific approaches targeting CSCs. Thus, therapeutic strategies that specifically target CSCs are being sought to reduce the risk of relapse and metastasis. In order to specifically target colon CSCs (while sparing somatic intestinal stem cells), it is critical to identify unique deregulated pathways responsible for self-renewal of CSCs and colon cancer recurrence. Colon CSCs present a unique opportunity to better understand the biology of solid tumors. Thus, a better understanding of the clinical signs and symptoms of colon cancer patients (undergoing surgery or chemotherapy) during perioperative periods, along with the underlying regulatory events affecting the stem/progenitor cell self-renewal and differentiation of colon epithelial cells, is of immense importance. In this review we discuss the implication of clinical factors and the emerging role of CSCs during recurrence of colon cancer along with the development of new therapeutic strategies involving the use of natural agents.

Gut microbiome profiling and colorectal cancer in African Americans and Caucasian Americans

AIM

To determine whether and to what extent the gut microbiome is involved in regulating racial disparity in colorectal cancer (CRC).

METHODS

All patients were recruited and experiments were performed in accordance with the relevant guidelines and regulations by the Institutional Review Boards (IRB), committees of the John D. Dingell VAMC and Wayne State University guidelines. African American (AA) and Caucasian American (CA) patients were scheduled for an outpatient screening for colonoscopy, and no active malignancy volunteer patients were doubly consented, initially by the gastroenterologist and later by the study coordinator, for participation in the study. The gut microbial communities in colonic effluents from AAs and CAs were examined using 16sRNA profiling, and bacterial identifications were validated by performing SYBR-based Real Time PCR. For metagenomic analysis to characterize the microbial communities, multiple software/tools were used, including Metastats and R statistical software.

RESULTS

It is generally accepted that the incidence and mortality of CRC is higher in AAs than in CAs. However, the reason for this disparity is not well understood. We hypothesize that the gut microbiome plays a role in regulating this disparity. Indeed, we found significant differences in species richness and diversity between AAs and CAs. Bacteroidetes was more abundant in AAs than in CAs. In particular, the pro-inflammatory bacteria Fusobacterium nucleatum and Enterobacter species were significantly higher in AAs, whereas probiotic Akkermansia muciniphila and Bifidobacterium were higher in CAs. The polyphyletic Clostridia class showed a divergent pattern, with Clostridium XI elevated in AAs, and Clostridium IV, known for its beneficial function, higher in CAs. Lastly, the AA group had decreased microbial diversity overall in comparison to the CA group. In summary, there were significant differences in pro-inflammatory bacteria and microbial diversity between AA and CA, which may help explain the CRC disparity between groups.

CONCLUSION

Our current investigation, for the first time, demonstrates microbial dysbiosis between AAs and CAs, which could contribute to the racial disparity of CRC.