Longitudinal muscle shows abnormal relaxation responses to nitric oxide and contains altered levels of NOS1 and elastin in uncomplicated diverticular disease

From diverticulosis to complicated diverticular disease: Progression of myogenic alterations and oxidative imbalance

BACKGROUND

The natural history and pathophysiology of diverticular disease (DD) are still uncertain. An ex-vivo human complicated DD (cDD) model has recently shown a predominant transmural oxidative imbalance. The present study aims to evaluate whether the previously described alterations may precede the symptomatic form of the disease.

METHODS

Colonic surgical samples obtained from patients with asymptomatic diverticulosis (DIV), complicated DD, and controls were systematically and detailed morphologically and molecularly analyzed. Therefore, histologic, histomorphometric, immunohistochemical evaluation, and gene and protein expression analysis were performed to characterize colonic muscle changes and evaluate chronic inflammation, oxidative imbalance, and hypoxia. Functional muscle activity was tested on strips and isolated cells in response to contractile and relaxant agents.

KEY RESULTS

Compared with controls, DD showed a marketed increase in muscle layer thickness, smooth muscle cell syncytium disarray, and increased interstitial fibrosis; moreover, the observed features were more evident in the cDD group. These changes mainly affected longitudinal muscle and were associated with altered contraction-relaxation dynamics and fibrogenic switch of smooth muscle cells. Chronic lymphoplasmacytic inflammation was primarily evident in the mucosa and spared the muscle. A transmural increase in carbonylated and nitrated proteins, with loss of antioxidant molecules, characterized both stages of DD, suggesting early oxidative stress probably triggered by recurrent ischemic events, more pronounced in cDD, where HIF-1 was detected in both muscle and mucosa.

CONCLUSION & INFERENCES

The different DD clinical scenarios are part of a progressive process, with oxidative imbalance representing a new target in the management of DD.

The human colon: Evidence for degenerative changes during aging and the physiological consequences

BACKGROUND

The incidence of constipation increases among the elderly (>65 years), while abdominal pain decreases. Causes include changes in lifestyle (e.g., diet and reduced exercise), disease and medications affecting gastrointestinal functions. Degenerative changes may also occur within the colo-rectum. However, most evidence is from rodents, animals with relatively high rates of metabolism and accelerated aging, with considerable variation in time course. In humans, cellular and non-cellular changes in the aging intestine are poorly investigated.

PURPOSE

To examine all available studies which reported the effects of aging on cellular and tissue functions of human isolated colon, noting the region studied, sex and age of tissue donors and study size. The focus on human colon reflects the ability to access full-thickness tissue over a wide age range, compared with other gastrointestinal regions. Details are important because of natural human variability. We found age-related changes within the muscle, in the enteric and nociceptor innervation, and in the submucosa. Some involve all regions of colon, but the ascending colon appears more vulnerable. Changes can be cell- and sublayer-dependent. Mechanisms are unclear but may include development of "senescent-like" and associated inflammaging, perhaps associated with increased mucosal permeability to harmful luminal contents. In summary, reduced nociceptor innervation can explain diminished abdominal pain among the elderly. Degenerative changes within the colon wall may have little impact on symptoms and colonic functions, because of high "functional reserve," but are likely to facilitate the development of constipation during age-related challenges (e.g., lifestyle, disease, and medications), now operating against a reduced functional reserve.

Colonic diverticular disease: clinical presentation, diagnosis, treatment, and prevention Clinical guidelines of the Russian Scientific Medical Society of Internal Medicine, the Gastroenterological Scientific Society of Russia, and the North- West Society of Gastroenterologists and Hepatologists

   Clinical guidelines are intended for gastroenterologists, internists, and general practitioners and focus primarily on the management of patients with symptomatic uncomplicated diverticular disease, as well as on the primary and secondary prevention of acute diverticulitis and other complications of diverticular disease. Clinical guidelines were developed by the Russian Scientific Medical Society of Internal Medicine, the Gastroenterological Scientifi c Society of Russia, and the North-West Society of Gastroenterologists and Hepatologists. One of the reasons for creating new clinical guidelines is that the current guidelines on diverticular disease (2021) pay much more attention to complications of diverticular disease and surgical treatment of acute and chronic complications of the disease.

Colonic diverticular disease: clinical presentation, diagnosis, treatment, and prevention Clinical guidelines of the Russian Scientific Medical Society of Internal Medicine, the Gastroenterological Scientific Society of Russia, and the North- West Society of Gastroenterologists and Hepatologists

   Clinical guidelines are intended for gastroenterologists, internists, and general practitioners and focus primarily on the management of patients with symptomatic uncomplicated diverticular disease, as well as on the primary and secondary prevention of acute diverticulitis and other complications of diverticular disease. Clinical guidelines were developed by the Russian Scientific Medical Society of Internal Medicine, the Gastroenterological Scientifi c Society of Russia, and the North-West Society of Gastroenterologists and Hepatologists. One of the reasons for creating new clinical guidelines is that the current guidelines on diverticular disease (2021) pay much more attention to complications of diverticular disease and surgical treatment of acute and chronic complications of the disease.

Oxidative imbalance and muscular alterations in diverticular disease

BACKGROUND

It is still a matter of debate if neuromuscular alterations reflect a primary event in diverticular disease (DD).

AIMS

This study aimed to assess colonic wall layers from both stenotic and non-stenotic complicated DD, bio-phenotypic alterations, inflammatory and oxidative status.

METHODS

A systematic analysis of colonic specimens obtained from stenotic and non-stenotic DD specimens was conducted and compared with controls. Biological activity and qPCR analysis were performed on longitudinal and circular muscles. Western blot analysis was performed throughout colonic wall layers to quantify oxidative and inflammatory markers.

RESULTS

A homogenous increase in oxidative stress was observed through all the layers, which were more sharpened in the longitudinal muscle for a loss in antioxidant defenses. In both stenotic and non-stenotic colon, the longitudinal muscle presented an impaired relaxation and a cellular phenotypic switch driven by transforming growth factor-β with an increase in mRNA expression of collagen Iα and a decrease in myosin heavy chain. The circular muscle, as the mucosa, was less affected by molecular alterations. No peculiar increase in inflammatory markers was observed.

CONCLUSION

A longitudinal colonic myopathy is present in DD, independently from the disease stage associated with an oxidative imbalance that could suggest new therapeutic strategies.

Pathophysiology of Diverticular Disease: From Diverticula Formation to Symptom Generation

Diverticular disease is a common clinical problem, particularly in industrialized countries. In most cases, colonic diverticula remain asymptomatic throughout life and sometimes are found incidentally during colonic imaging in colorectal cancer screening programs in otherwise healthy subjects. Nonetheless, roughly 25% of patients bearing colonic diverticula develop clinical manifestations. Abdominal symptoms associated with diverticula in the absence of inflammation or complications are termed symptomatic uncomplicated diverticular disease (SUDD). The pathophysiology of diverticular disease as well as the mechanisms involved in the shift from an asymptomatic condition to a symptomatic one is still poorly understood. It is accepted that both genetic factors and environment, as well as intestinal microenvironment alterations, have a role in diverticula development and in the different phenotypic expressions of diverticular disease. In the present review, we will summarize the up-to-date knowledge on the pathophysiology of diverticula and their different clinical setting, including diverticulosis and SUDD.

Lactobacillus paracasei CNCM I 1572: A Promising Candidate for Management of Colonic Diverticular Disease

Diverticular disease (DD) is a common gastrointestinal condition. Patients with DD experience a huge variety of chronic nonspecific symptoms, including abdominal pain, bloating, and altered bowel habits. They are also at risk of complications such as acute diverticulitis, abscess formation, hemorrhage, and perforation. Intestinal dysbiosis and chronic inflammation have recently been recognized as potential key factors contributing to disease progression. Probiotics, due to their ability to modify colonic microbiota balance and to their immunomodulatory effects, could present a promising treatment option for patients with DD. Lactobacillus paracasei CNCM I 1572 (LCDG) is a probiotic strain with the capacity to rebalance gut microbiota and to decrease intestinal inflammation. This review summarizes the available clinical data on the use of LCDG in subjects with colonic DD.

Ancestry- and sex-specific effects underlying inguinal hernia susceptibility identified in a multiethnic genome-wide association study meta-analysis

Inguinal hernias are some of the most frequently diagnosed conditions in clinical practice and inguinal hernia repair is the most common procedure performed by general surgeons. Studies of inguinal hernias in non-European populations are lacking, though it is expected that such studies could identify novel loci. Further, the cumulative lifetime incidence of inguinal hernia is nine times greater in men than women, however, it is not clear why this difference exists. We conducted a genome-wide association meta-analysis of inguinal hernia risk across 513 120 individuals (35 774 cases and 477 346 controls) of Hispanic/Latino, African, Asian and European descent, with replication in 728 418 participants (33 491 cases and 694 927 controls) from the 23andMe, Inc dataset. We identified 63 genome-wide significant loci (P < 5 × 10⁻⁸), including 41 novel. Ancestry-specific analyses identified two loci (LYPLAL1-AS1/SLC30A10 and STXBP6-NOVA1) in African ancestry individuals. Sex-stratified analyses identified two loci (MYO1D and ZBTB7C) that are specific to women, and four (EBF2, EMX2/RAB11FIP2, VCL and FAM9A/FAM9B) that are specific to men. Functional experiments demonstrated that several of the associated regions (EFEMP1 and LYPLAL1-SLC30A10) function as enhancers and show differential activity between risk and reference alleles. Our study highlights the importance of large-scale genomic studies in ancestrally diverse populations for identifying ancestry-specific inguinal hernia susceptibility loci and provides novel biological insights into inguinal hernia etiology.

Age, alcohol, sex, and metabolic factors as risk factors for colonic diverticulosis

BACKGROUND

The pathogenesis of colonic diverticulosis is not well understood. Moreover, only a few studies on colonic diverticulosis have been reported in mainland China.

AIM

To evaluate the prevalence of and risk factors for asymptomatic colorectal diverticulosis in Eastern China.

METHODS

From August 2016 to July 2020, 6180 asymptomatic individuals were enrolled in this cross-sectional study. These individuals had undergone physical examinations, laboratory testing, and colonoscopy. Data regarding the baseline characteristics and their general health status were obtained through interviews.

RESULTS

The prevalence of colonic diverticulosis was 7.3% (449/6180). Colonic diverticulosis was detected predominantly on the right side of the colon (88.4%). Logistic regression analysis revealed that an age ≥ 60 years (adjusted odds ratio [OR] 2.149, 95% confidence interval [CI] 1.511-3.057, P < 0.001), male sex (adjusted OR: 1.878, 95%CI: 1.373-2.568, P < 0.001), obesity (adjusted OR: 1.446, 95%CI: 1.100-1.902, P = 0.008), alcohol intake (adjusted OR: 1.518, 95%CI: 1.213-1.901, P < 0.001), hypertension (adjusted OR: 1.454, 95%CI: 1.181-1.789, P < 0.001), hypertriglyceridemia (adjusted OR: 1.287, 95%CI: 1.032-1.607, P = 0.025), and hyperuricemia (adjusted OR: 1.570, 95%CI: 1.257-1.961, P < 0.001) significantly increased the risk of colonic diverticulosis.

CONCLUSION

Advanced age, male sex, alcohol intake, obesity, and other metabolic-related factors, such as hypertension, hypertriglyceridemia, and hyperuricemia, were independent risk factors for colonic diverticulosis. Understanding the true prevalence of colonic diverticulosis and its associated risk factors will aid in its prevention and treatment.

Management of colonic diverticulitis

Left sided colonic diverticulitis is a common and costly gastrointestinal disease in Western countries, characterized by acute onset of often severe abdominal pain. Imaging is necessary to make an initial diagnosis and determine disease severity. Colonoscopy should be done six to eight weeks after diagnosis to rule out a missed colon malignancy. Antibiotic treatment is used selectively in immunocompetent patients with mild acute uncomplicated diverticulitis. The clinical course of diverticulitis commonly includes unpredictable recurrences and chronic gastrointestinal symptoms, which are a detriment to quality of life. A better understanding of prognosis has prompted a shift toward non-operative approaches. The decision to undergo prophylactic colon resection should be individualized to consider the severity of diverticulitis, the patient's health and immune status, and the patient's preferences and values, as well as benefits and risks. Because only a section of colon is removed, recurrent diverticulitis remains a risk. Acute diverticulitis with an abscess is treated with antibiotics that cover Gram negative and anaerobic bacteria, with or without percutaneous drainage. Acute diverticulitis with purulent or feculent contamination of the peritoneal cavity is managed with surgery; primary resection and anastomosis is the procedure of choice in stable patients.

Genetic Risk Factors for Diverticular Disease-Emerging Evidence

Diverticular disease is traditionally understood as an environmental disease caused by diet and constipation. However, genes are increasing understood to play a role in pathogenesis. Twin studies suggest a substantial component of individual risk is due to heritable factors. Association of diverticular disease with other traits suggests an underlying biological mechanism and recently genome-wide association studies have described the genetic architecture underlying this complex phenotype. These studies suggest a new paradigm for understanding this common surgical disease.

Etiopathogenetic Mechanisms in Diverticular Disease of the Colon

This article reviews epidemiological evidence of heritability and putative mechanisms in diverticular disease, with greatest attention to 3 recent studies of genetic associations with diverticular disease based on genome-wide or whole-genome sequencing studies in large patient cohorts. We provide an analysis of the biological plausibility of the significant associations with gene variants reported and highlight the relevance of ANO1, CPI-17 (aka PPP1R14A), COLQ6, COL6A1, CALCB or CALCA, COL6A1, ARHGAP15, and S100A10 to colonic neuromuscular function and tissue properties that may result in altered compliance and predispose to the development of diverticular disease. Such studies also identify candidate genes for future studies.

Alterations in enteric calcitonin gene-related peptide in patients with colonic diverticular disease: CGRP in diverticular disease

Diverticular disease (DD) is one of the most prevalent diseases of the large bowel. Lately, imbalance of neuro-muscular transmission has been recognized as a major etiological factor for DD. Neuronal calcitonin gene-related peptide (CGRP) is a potent gastrointestinal smooth muscle relaxant shown to have a widespread effect within the alimentary tract. Nevertheless, CGRPergic innervation of the enteric ganglia has never been considered in the context of motility impairment observed in DD patients. Changes in CGRP and calcitonin receptor-like receptor (CRLR) abundance within enteric ganglia were investigated in sigmoid samples from symptomatic and asymptomatic DD patients using quantitative fluorescence microscopy. CGRP effect on gastrointestinal smooth muscle was investigated using organ bath technique. We found CGRP levels within the enteric ganglia to be declined by up to 52% in symptomatic DD patients. Conversely, CRLR within the enteric ganglia was upregulated by 41% in symptomatic DD. Longitudinal smooth muscle displayed an elevated (+10.5%) relaxant effect to the exogenous application of CGRP in colonic strips from symptomatic DD patients. Samples from asymptomatic DD patients consistently showed intermediate values across different experiments. In conclusion, the present study demonstrates that CGRPergic signaling is subject to alteration in DD. Our results suggest that a hypersensitization mechanism to gradually decreasing levels of CGRP-IR nerve fibers takes place during DD progression. Alterations to CGRPergic signaling in DD disease may have implications for physiological abnormalities associated with colonic DD.

Pathophysiology of diverticular disease

Inflammation of diverticula, or outpouchings of the colonic mucosa and submucosa through the muscularis layer, leads to diverticulitis. The development of diverticular disease, encompassing both diverticulosis and diverticulitis, is a result of genetic predisposition, lifestyle, and environmental factors, including the microbiome. Areas covered: Previous reports implicated genetic predisposition, environmental factors, and colonic dysmotility in diverticular disease. Recent studies have associated specific host immune responses and the microbiome as contributors to diverticulitis. To review pertinent literature describing pathophysiological factors associated with diverticulosis or diverticulitis, we searched the PubMed database (March 2018) for articles considering the role of colonic architecture, genetic predisposition, environment, colonic motility, immune response, and the microbiome. Expert commentary: In the recent years, research into the molecular underpinnings of diverticular disease has enhanced our understanding of diverticular disease pathogenesis. Although acute uncomplicated diverticulitis is treated with broad spectrum antibiotics, evaluation of the microbiome has been limited and requires further comprehensive studies. Evidence suggests that a deregulation of the host immune response is associated with both diverticulosis and diverticulitis. Further examining these pathways may reveal proteins that can be therapeutic targets or aid in identifying biological determinants of clinical or surgical decision making.

Elastin-driven genetic diseases

Elastic fibers provide recoil to tissues that undergo repeated deformation, such as blood vessels, lungs and skin. Composed of elastin and its accessory proteins, the fibers are produced within a restricted developmental window and are stable for decades. Their eventual breakdown is associated with a loss of tissue resiliency and aging. Rare alteration of the elastin (ELN) gene produces disease by impacting protein dosage (supravalvar aortic stenosis, Williams Beuren syndrome and Williams Beuren region duplication syndrome) and protein function (autosomal dominant cutis laxa). This review highlights aspects of the elastin molecule and its assembly process that contribute to human disease and also discusses potential therapies aimed at treating diseases of elastin insufficiency.

Recent advances in understanding and managing diverticulitis

In the past few decades, the increasing socioeconomic burden of acute diverticulitis (AD) has become evident, and with the growth of the population age, this significant economic impact will likely continue to rise. Furthermore, recent evidence showed an increased rate of hospital admissions especially evident among women and younger individuals. The natural history and pathophysiology of this clinical condition is still to be fully defined, and efforts continue to be made in the identification of risk factors and the establishment of relative preventive strategies. The actual therapeutic strategies aimed to modulate gut microbiota, such as rifaximin or probiotics, or to reduce mucosal inflammation, such as mesalazine, present a relatively poor efficacy for both the prevention of the first AD episode (primary prevention) and its recurrence (secondary prevention). In the last few years, the main goal achieved has been in the management of AD in that uncomplicated AD can, to a larger extent, be managed in an outpatient setting with no or little supportive therapy, a strategy that will certainly impact on the health costs of this disease. The problem of AD recurrence remains a topic of debate. The aim of this review is to present updated evidence on AD epidemiology and relative open clinical questions and to analyze in detail predisposing and protective factors with an attempt to integrate their possible modes of action into the several pathogenic mechanisms that have been suggested to contribute to this multifactorial disease. A unifying hypothesis dealing with the colonic luminal and extra-luminal microenvironments separately is provided. Finally, evidence-based changes in therapeutic management will be summarized. Because of an ascertained multifactorial pathogenesis of uncomplicated and complicated AD, it is probable that a single 'causa prima' will not be identifiable, and a better stratification of patients could allow one to pursue tailored therapeutic algorithm strategies.

Bacterial stimuli activate nitric oxide colonic mucosal production in diverticular disease. Protective effects of L. casei DG® (Lactobacillus paracasei CNCM I-1572)

BACKGROUND

Micro-inflammation and changes in gut microbiota may play a role in the pathogenesis of diverticular disease (DD).

OBJECTIVE

The objective of this article is to evaluate the expression of nitric oxide (NO)-related mediators and S100B in colonic mucosa of patients with DD in an ex vivo model of bacterial infection.

METHODS

Intestinal biopsies obtained from patients with diverticulosis, symptomatic uncomplicated diverticular disease (SUDD) and SUDD with previous acute diverticulitis (SUDD+AD) were stimulated with the probiotic L. casei DG® (LCDG) and/or the pathogen enteroinvasive Escherichia coli (EIEC). S100B, NO release and iNOS expression were then evaluated.

RESULTS

Basal iNOS expression was significantly increased in SUDD and SUDD+AD patients. Basal NO expression was significantly increased in SUDD+AD. No differences in S100B release were found. In all groups, iNOS expression was significantly increased by EIEC and reduced by LCDG. In all groups, except for SUDD+AD, EIEC significantly increased NO release, whereas no increase was observed when LCDG was added to biopsies. EIEC did not induce significant changes in S100B release.

CONCLUSIONS

Colonic mucosa of patients with DD is characterized by a different reactivity toward pathogenic stimuli. LCDG plays a role in counteracting the pro-inflammatory effects exerted by EIEC, suggesting a beneficial role of this probiotic in DD.

Management of sigmoid diverticulitis: an update

The role, indications and modalities of elective resection for sigmoid diverticulitis remain the cause of fierce debate. During the past two decades clinicians have increasingly recognized that: (1) young patients (<50) are no more at risk to develop more aggressive course of the disease; and (2) patients who present initially with a first uncomplicated attack are no more at risk for developing subsequent complicated diverticulitis requiring emergency surgery. Hence, the previously well-recognized indications (based upon age of the patients or the number of attacks) are no longer valid. Yet, the number of sigmoid resections performed for diverticulitis in industrialized countries is increasing, which seems to indicate that in many cases, uncomplicated sigmoid diverticulitis progressively evolves towards a chronic symptomatic condition, which significantly impacts upon the patients' quality of life. The aims of this review are twofold: (1) to identify which disease presentation still represents good indications for elective laparoscopic sigmoid resection; and (2) to summarize the technical aspects of surgery for a benign condition, such as diverticular disease.

Diverticular disease: guidelines of the german society for gastroenterology, digestive and metabolic diseases and the german society for general and visceral surgery

BACKGROUND

Diverticular disease is one of the most common disorders of the gastrointestinal tract. 28-45% of the population develop colonic diverticula, while about 25% suffer symptoms and about 5% complications.

AIM

To create formal guidelines for diagnosis and management.

METHODS

Six working groups with 44 participants analyzed key questions in subject areas assigned to them. Following a systematic literature search, 451 publications were included. Consensus was obtained by agreement within the working groups, two Delphi processes and a guideline conference.

RESULTS

Targeted management of diverticular disease requires a classificatory diagnosis. A new classification was created. In addition to the clinical examination, intestinal ultrasound or computed tomography is the determining factor. Interval colonoscopy is recommended to exclude comorbidities. A low-fiber diet, obesity, lack of exercise, smoking and immunosuppression have an adverse impact on diverticulosis. This can lead to diverticulitis. Antibiotics are no longer recommended in uncomplicated diverticulitis if no risk factors such as immunosuppression are present. If close monitoring is ensured, uncomplicated diverticulitis can be treated on an outpatient basis. Complicated diverticulitis should be treated in hospital, involving broad-spectrum antibiotic therapy, where necessary abscess drainage, and surgery, if possible laparoscopically. In the case of chronic relapsing diverticulitis, the risk of perforation decreases with each episode, so that surgery is no longer recommended after the second episode but only following individual assessment.

CONCLUSIONS

New findings on diverticular disease call into question the overuse of antibiotics and excessive indications for surgery. Targeted treatment requires a precise diagnosis and intensive interdisciplinary cooperation.

Utilization of High-frequency Mini Probe Ultrasound in the Assessment of Colonic Wall Thickness in Patients With Diverticular Disease: A Feasibility Study

BACKGROUND

Assessment of diverticular disease (DD) is routinely undertaken by colonoscopy and computed tomography (CT) scan. Improvements in high-frequency ultrasound have enabled evaluation of the colon wall structure in detail. Our objective was to assess ultrasound in measuring colonic wall thickness in DD.

METHODS

High-frequency 20-MHz ultrasound was undertaken to measure individual layer and total colonic wall thickness. Case patients had symptomatic DD. Control patients underwent colonoscopy for other reasons. Select patients also underwent abdominal CT scan.

RESULTS

Thirty-three patients underwent colonoscopic ultrasound, 18 with sigmoid diverticula and 15 control patients.Total wall thickness was greater in patients with DD, 5.69 mm (1.68) versus 2.61 mm (1.29, P<0.0001). Patients with DD had significant thickening in each individual layer of the colonic wall measured (each P<0.0001).Greatest differences were in the muscularis propria, which was an average of 3.5 times thicker in patients with DD. In patients with DD, the segment of colonic wall measured was also thicker, with average mid-sigmoid thickness of 23.0 mm (SD 9.6 mm).

CONCLUSIONS

Patients with DD have increased sigmoid thickness when compared with controls, especially the muscularis propria. Unlike CT, ultrasound was also able to identify thickening in the mucosa and submucosa.

Morphologic Basis for Developing Diverticular Disease, Diverticulitis, and Diverticular Bleeding

Diverticula of the colon are pseudodiverticula defined by multiple outpouchings of the mucosal and submucosal layers penetrating through weak spots of the muscle coat along intramural blood vessels. A complete prolapse consists of a diverticular opening, a narrowed neck, and a thinned diverticular dome underneath the serosal covering. The susceptibility of diverticula to inflammation is explained by local ischemia, translocation of pathogens due to retained stool, stercoral trauma by fecaliths, and microperforations. Local inflammation may lead to phlegmonous diverticulitis, paracolic/mesocolic abscess, bowel perforation, peritonitis, fistula formation, and stenotic strictures. Diverticular bleeding is due to an asymmetric rupture of distended vasa recta at the diverticular dome and not primarily linked to inflammation. Structural and functional changes of the bowel wall in diverticular disease comprise: i) Altered amount, composition, and metabolism of connective tissue; ii) Enteric myopathy with muscular thickening, deranged architecture, and altered myofilament composition; iii) Enteric neuropathy with hypoganglionosis, neurotransmitter imbalance, deficiency of neurotrophic factors and nerve fiber remodeling; and iv) Disturbed intestinal motility both in vivo (increased intraluminal pressure, motility index, high-amplitude propagated contractions) and in vitro (altered spontaneous and pharmacologically triggered contractility). Besides established etiologic factors, recent studies suggest that novel pathophysiologic concepts should be considered in the pathogenesis of diverticular disease.

Changing views on diverticular disease: impact of aging, obesity, diet, and microbiota

The development of colonic diverticulosis is a common aging change in industrialized nations. While most patients have asymptomatic diverticulosis, around one in five develops symptomatic diverticular disease. This is characterized by recurrent abdominal pain and disturbed bowel habit. Some of the pain episodes are prolonged and are due to acute diverticulitis, which itself may be complicated by abscess, perforation, fistulation, or stricture formation. Risk factors favouring the development of symptomatic diverticular disease include obesity, smoking and diets low in fiber but high in red meat and animal fat. What determines the transition from asymptomatic diverticulosis to symptomatic diverticular disease is unclear but neuromuscular changes following acute diverticulitis may be responsible in some cases. The severity of symptoms generated depends on cerebral pain processing which is influenced by psychosocial factors. These are important considerations in deciding optimal patient management. Prior theories of the cause of diverticulosis suggested that constipation was an important cause, but new data challenge this and has provoked new ideas. Underlying mechanisms causing diverticulosis include weakening of the colonic wall and/or degenerative changes in the enteric nerves. Dietary induced changes in microbiota and the host inflammatory response may underlie the subsequent development of acute/chronic diverticulitis and its sequela.

[Anatomy and pathogenesis of diverticular disease]

BACKGROUND

Although diverticular disease is one of the most frequent gastrointestinal disorders the pathogenesis is not yet sufficiently clarified.

OBJECTIVES

The aim is to define the anatomy and pathogenesis of diverticular disease considering the risk factors and description of structural and functional alterations of the bowel wall.

METHODS

This article gives an appraisal of the literature, presentation and evaluation of classical etiological factors, analysis and discussion of novel pathogenetic concepts.

RESULTS

Colonic diverticulosis is defined as an acquired out-pouching of multiple and initially asymptomatic pseudodiverticula through muscular gaps in the colon wall. Diverticular disease is characterized by diverticular bleeding and/or inflammatory processes (diverticulitis) with corresponding complications (e.g. abscess formation, fistula, covered and open perforation, peritonitis and stenosis). Risk factors for diverticular disease include increasing age, genetic predisposition, congenital connective tissue diseases, low fiber diet, high meat consumption and pronounced overweight. Alterations of connective tissue cause a weakening of preformed exit sites of diverticula and rigidity of the bowel wall with reduced flexibility. It is assumed that intestinal innervation disorders and structural alterations of the musculature induce abnormal contractile patterns with increased intraluminal pressure, thereby promoting the development of diverticula. Moreover, an increased release of pain-mediating neurotransmitters is considered to be responsible for persistent pain in chronic diverticular disease.

CONCLUSIONS

According to the present data the pathogenesis of diverticular disease cannot be attributed to a single factor but should be considered as a multifactorial event.

Left colon acute diverticulitis: an update on diagnosis, treatment and prevention

Diverticulosis of the colon is a common disease with an increasing incidence in Western Countries. It represents a significant burden for National Health Systems in terms of costs. Most people with diverticulosis remain asymptomatic, about one quarter of them will develop an episode of symptomatic diverticular disease and up to 5% an episode of acute diverticulitis (AD). AD shows an increasing prevalence. Recently, progresses have been reached about the etiology, pathogenesis, natural course of diverticular disease and its complications; improvements about the diagnosis and treatment of AD have been achieved. However, the treatment options are not well defined because of a lack of solid evidence: there are few systematic reviews and well conducted trials to guide decision-making in the treatment of AD and in the prevention of its recurrences. This review describes the recent evidence about diagnosis, treatment and prevention of AD.

Nitrergic neuro-muscular transmission is up-regulated in patients with diverticulosis

BACKGROUND

Neuro-transmission impairment could be associated to motility changes observed in patients with diverticular disease. Therefore, the objective was to characterize the inhibitory neuro-muscular transmission and gene expression changes of the enteric inhibitory pathways in patients with diverticulosis (DS).

METHODS

Circular muscle strips from sigmoid colon of patients with DS and controls were studied using the organ bath technique to evaluate spontaneous contractility and enteric motor neurons stimulated by electrical field and qRT-PCR to assess the expression of nNOS, iNOS, P2Y1 R and PGP9.5.

KEY RESULTS

Patients with DS presented decreased spontaneous rhythmic contractions (SRC) that were significantly enhanced after incubation with L-NNA (1 mM) and TTX (1 μM), and unaffected by the P2Y1 antagonist MRS2500 (1 μM). Stimulation on enteric motor neurons caused an increased duration of the latency of OFF-contractions in DS group (p < 0.001), antagonized by L-NNA and slightly affected by MRS2500 (1 μM). No differences in the IC50 between controls and DS patients were observed on inhibition of SRC for the NO-donor sodium nitroprusside (SNP) and the preferential P2Y agonist ADPβS. Moreover, nNOS relative expression was also up-regulated 2.3-fold in the DS group (p < 0.05) whereas there was no significant difference in relative expression of iNOS, P2Y1 R and the neuronal marker PGP9.5 between groups.

CONCLUSIONS & INFERENCES

Patients with DS presented an over-expression of nNOS with increased endogenously NO-mediated responses suggesting enhanced NO-release. Up-regulation in the nitrergic pathway in early stages of the disease might play a role in colonic motor disorders associated to diverticular disease.

Alterations of the enteric smooth musculature in diverticular disease

BACKGROUND

The pathogenesis of diverticular disease (DD) is considered to be multifactorial and involves intestinal motor disturbances and an underlying enteric neuromuscular pathology. While an enteric neuropathy has been well documented, actual studies on concomitant alterations of the enteric musculature are limited. This study is aimed at reassessing the smooth muscle tissue by histological, ultrastructural and molecular-biological approaches.

METHODS

Full-thickness sigmoid specimens were obtained from patients with DD (n = 20) and controls (n = 19). Morphometric analysis was performed to evaluate the thickness and connective tissue index of the circular and longitudinal muscle layers as well as the myenteric plexus. Structural alterations were determined by light and transmission electron microscopy. mRNA profiles of components of the contractile smooth muscle apparatus including smooth muscle α-actin, smoothelin, histone deacetylase 8, and smooth muscle myosin heavy chain (SMMHC) were assessed by qPCR. Altered gene expression levels were confirmed at protein level by immunohistochemistry.

RESULTS

Compared to controls, patients with DD showed (1) increased thickness of the circular and longitudinal muscle layers, (2) architectural alterations of smooth muscle cells, (3) increased connective tissue index of the longitudinal muscle layer, (4) focally reduced density of myofilaments at ultrastructural level, (5) specific down-regulation of SMMHC mRNA levels, (6) decreased immunoreactivity of SMMHC, (7) oligo-neuronal hypoganglionosis.

CONCLUSIONS

DD is associated with distinct structural and functional alterations of the enteric musculature. The enteric myopathy is characterized by disturbed muscular architecture, connective tissue replacement and loss of specific myofilaments and thus may contribute to the pathogenesis and progression of DD.

Are there any functional differences of the enteric nervous system between the right-sided diverticular colon and the left-sided diverticular colon? An in vitro study

PURPOSE

To evaluate functional differences of the enteric nervous system (ENS) in patients between right-side colonic diverticula (RCD) and left-sided colonic diverticula (LCD), the author compared the ENS responses between RCD and LCD.

METHODS

Ten specimens were obtained from 10 patients with RCD, and 16 specimens were taken from 16 LCD. As a control, twenty-two specimens of right-sided normal colon (RNC) were obtained from 22 colonic cancers. Twenty-four specimens of left sided normal colon (LNC) were obtained from 24 colonic cancers. A mechanography was used to evaluate in vitro muscle responses to electrical field stimulation (EFS) before and after treatment with various autonomic nerve blockers.

RESULTS

Before blockade of the adrenergic and cholinergic nerves, the incidences of contraction via cholinergic nerve in the colons with diverticula were significantly greater than those in the normal colons (right-sided colon; p = 0.0022, left-sided colon; p < 0.0001). There were no significant differences between RNC and LNC (p = 0.3606), and between RCD and LCD (p = 0.7684). After the blockade of adrenergic and cholinergic nerves, the incidence of relaxation via non-adrenergic non-cholinergic inhibitory (NANC) nerve in the normal colons was significantly greater than that in the diverticular colons (right-sided colon; p = 0.0435, left-sided colon; p = 0.0034). There were no significant differences between RNC and LNC (p = 0.2909) and between RCD and LCD (p = 0.9464).

CONCLUSION

Cholinergic nerves were dominant in bilateral diverticular colon compared with bilateral normal colon. NANC inhibitory nerves were dominant in bilateral normal colon compared with bilateral diverticular colon. There were also no functional differences of the ENS between RCD and LCD.

In vitro motor patterns and electrophysiological changes in patients with colonic diverticular disease

PURPOSE

The underlying mechanism responsible for motility changes in colonic diverticular disease (DD) is still unknown. In the present study, our aim was to investigate the structural and in vitro motor changes in the sigmoid colon of patients with DD.

METHODS

Muscle bath, microelectrodes and immunohistochemical techniques were performed with samples obtained from the left and sigmoid colon of patients with DD and compared with those of patients without DD.

RESULTS

The amplitude and area under the curve of the spontaneous rhythmic phasic contractions were greatly reduced in patients with DD whereas their frequency and tone remained unaltered. Electrical field stimulation induced a neurally mediated, enhanced ON-contraction (amplitude) in patients with DD and increased the duration of latency of OFF-contractions. The resting membrane potential of smooth muscle cells was hyperpolarized and the amplitude of the inhibitory junction potential was increased in patients with DD. In contrast, no significant histological differences were observed in patients with DD as smooth muscle (circular and longitudinal layers), interstitial cells of Cajal, glial cells and myenteric neurons densities remained unaltered.

CONCLUSIONS

Sigmoid strips from patients with asymptomatic DD showed an altered motor pattern with reduced spontaneous motility and enhanced neurally mediated colonic responses involving both excitatory and inhibitory motor pathways. No major neural and muscular structural elements were detected at this stage of the disease. These findings could be valuable in understanding the pathophysiology of this prevalent digestive disease.

A clinicopathological study of serotonin of sigmoid colon mucosa in association with chronic symptoms in uncomplicated diverticulosis

INTRODUCTION

Neurotransmitter imbalance is hypothesised as a pathogenetic mechanism in several bowel conditions. We previously reported increased 5-HT in the sigmoid mucosa of colon resected for complicated diverticular disease (DD). We aimed to identify if abnormal 5-HT expression is associated with symptoms of uncomplicated DD.

METHODS

This was a prospective, comparative study and follow-up survey of symptoms. We examined the differences in 5-HT between DD patients and controls, as well as the presence of bowel symptoms at time of endoscopy and also 2 years later. Sigmoid biopsies were collected at colonoscopy. Immunohistochemical staining for 5-HT cells was performed.

RESULTS

Eighty-seven patients were recruited, 37 (42.5 %) DD and 50 (57.5 %) controls. No patients underwent surgery. There was no significant difference in total mean number of 5-HT-positive cells in DD compared to controls or between patients and controls with abdominal symptoms. Forty-one patients (47.1 %) responded to questionnaires at median 57.8 months from biopsy. Eighteen (43.9 %) were DD and 23(56.1 %) controls. 5-HT counts showed no significant association to symptom persistence.

DISCUSSION

Although 5-HT expression has previously been found to be increased in complicated DD in whole bowel-resected specimens, the same is not confirmed on colonic mucosal biopsies. This raises the suggestion that 5-HT may be involved in the development of acute complications but may not be involved in the pathogenesis of chronic symptoms.

Myogenic regional responsiveness to cholinergic and vipergic stimulation in human colon

BACKGROUND

Differences in the actions of enteric neurotransmitters on colonic circular and longitudinal muscle layers have not been clearly determined, nor the possible existence of intrinsic myogenic phenotypes that might contribute to regional differences in human colon motor activity. The aim of this study was to analyze the direct pharmaco-mechanical coupling of carbachol (CCh) and vasoactive intestinal polypeptide (VIP) on human colonic smooth muscle strips and cells.

METHODS

Circular and longitudinal muscle strips and cells were obtained from 15 human specimens of ascending and sigmoid colon. Both isometric tension on muscle strips and contraction and relaxation on cells were measured in response to increasing CCh and VIP concentrations.

KEY RESULTS

Circular muscle strips of ascending colon were more sensitive to the effect of CCh than that of sigmoid colon, EC(50) values being, respectively, 4.15μmolL(-1) and 8.47μmolL(-1) (P<0.05), although there were no differences in maximal responses. No regional differences were observed in longitudinal muscle strips or in smooth muscle cells. Maximal responses to CCh were higher on circular than longitudinal muscle strips and cells throughout the colon. A greater sensitivity to VIP was observed in ascending colon compared with sigmoid colon, both in circular (EC(50:) 0.041 and 0.15μmolL(-1) , respectively, P<0.01) and longitudinal (EC(50:) 0.043 and 0.09μmolL(-1) , respectively, P<0.05) strips, and similar differences were observed in longitudinal smooth muscle cells (EC(50:) 44.85 and 75.24nmolL(-1) , respectively, P<0.05).

CONCLUSIONS & INFERENCES

Regional myogenic differences in pharmaco-mechanical coupling between the enteric neurotransmitters and smooth muscle contribute to the complex regional motor patterns of human colon.

Colonic diverticular disease: abnormalities of neuromuscular function

Although diverticular disease of the colon (diverticulosis) is a frequent finding in Western countries, its pathophysiologic grounds are still only partially understood. Traditionally considered as an age-related condition, colonic diverticulosis is probably the final result of several factors concurring together to determine the anatomo-functional abnormalities eventually causing outpouching of the viscus' mucosa. Among these factors, a relevant role seems to be played by an abnormal neuromuscular function of the large bowel, as shown by abnormal myoelectrical and motor function repeatedly described in these patients, as well as by altered visceral perception. These anomalies might be related to the recent demonstration of derangement of enteric innervation (especially involving interstitial cells of Cajal and enteric glial cells), mucosal neuropeptides, and mucosal inflammation. The latter may have a role of paramount importance in the development of visceral hypersensitivity, responsible for abdominal pain in a subset of patients.

Abnormalities of neuromuscular anatomy in diverticular disease

The pathogenesis of diverticular disease is still poorly understood and considered to be multifactorial. Whereas classical pathogenetic concepts have focused on risk factors including increasing age, low-fiber diet and connective tissue disorders, novel concepts take into account that patients with diverticular disease exhibit disturbed intestinal motility patterns (that may result in functional obstruction and painful sensations) therefore postulating an underlying enteric neuro-/myopathy. Recent studies including quantitative evaluations of the enteric nervous system (ENS) in diverticular disease yielded hypoganglionic conditions of both myenteric and submucosal plexus as well as a nerve tissue remodeling in chronic diverticular disease. The disturbed neuromuscular communication was proven by demonstrating alterations in several enteric neurotransmitter systems, exemplified for the cholinergic, serotonergic, nitrergic system as well as for vasointestinal peptide, galanin and tachykinins. Novel lines of evidence have added the involvement of neurotrophic factors such as glial cell line-derived neurotrophic factor which is supposed to regulate ENS development and maintenance and which is downregulated in patients with diverticular disease. Consistent with the hypothesis of an enteric myopathy, deficits in smooth muscle integrity and composition such as hypertrophy, fibrotic transformation and gene expression deficits could be delineated. Taken together, the structural and functional findings on alterations of the ENS and the enteric musculature in diverticular disease provide evidence to strengthen the hypothesis that an enteric neuro-/myopathy may contribute to the development of colonic diverticula and the generation of symptoms in the course of the disease.

Review article: the pathogenesis of diverticular disease--current perspectives on motility and neurotransmitters

BACKGROUND

Low-fibre diet, structural abnormalities and ageing are traditional aetiological factors implicated in the development of diverticular disease. More recently, motility disorders are implicated in its causation leading to speculation that neurotransmitters play a role in mediating these disturbances.

AIMS

To draw together studies on the role of neurotransmitters in the development of diverticular disease and its symptoms.

METHODS

Medline, GoogleScholar and Pubmed were searched for evidence on this subject using the terms neurotransmitters, motility, diverticular disease and pathogenesis. Articles relevant to the subject were cited and linked references were also reviewed.

RESULTS

Serotonin, which has been found to be an excitatory colonic neurotransmitter, has been found in early studies to be increased in colonic enterochromaffin cells. Acetylcholine, which is thought to be an excitatory neurotransmitter and cholinergic activity, has also seen to be increased in diverticular disease. These findings may suggest that an increase in excitatory neurotransmitters may result in the hypersegmentation thought to cause pulsion diverticula. Similarly, a decrease in nitric oxide which is inhibitory is found.

CONCLUSIONS

There is some evidence that neurotransmitters may play a role in the motility disturbances seen in diverticular disease; however, a clear role is yet to be ascertained.

Demographic determinants of risk, colon distribution and density scores of diverticular disease

AIM: To investigate associations between ethnicity, age and sex and the risk, colon distribution and density scores of diverticular disease (DD).

METHODS: Barium enemas were examined in 1000 patients: 410 male, 590 female; 760 whites, 62 Asians, 44 black africans (BAs), and 134 other blacks (OBs). Risks and diverticula density of left-sided DD (LSDD) and right-sided-component DD (RSCDD = right-sided DD + right and left DD + Pan-DD) were compared using logistic regression.

RESULTS: Four hundred and forty-seven patients had DD (322 LSDD and 125 RSCDD). Adjusted risks: (1) LSDD: each year increase in age increased the odds by 6% (95% CI: 5-8, SE: 0.8%, P < 0.001); Asians: odds ratio (OR): 0.23 (95% CI: 0.10-0.53, SE: 0.1, P≤ 0.001) and OBs: OR: 0.25 (95% CI: 0.14-0.43, SE: 0.07, P≤ 0.001) appeared protected vs Whites; (2) RSCDD: each year increase in age increased the odds by 4% (95% CI: 2-6, SE: 1%, P < 0.001); females were 0.60 times (95% CI: 0.40-0.90, SE: 0.12, P = 0.01) less likely than males to have RSCDD; BAs were 3.51 times (95% CI: 1.70-7.24, SE: 1.30, P < 0.001) more likely than Whites to have RSCDD; and (3) DD density scores: each year increase in age increased the odds of high-density scores by 4% (95% CI: 1-6, SE: 1%, P < 0.001); RSCDD was 2.77 times (95% CI: 1.39-3.32, SE: 0.67, P < 0.001) more likely to be of high density than LSDD. No further significant differences were found in the adjusted models.

CONCLUSION: Right colonic DD might be more common and has higher diverticula density in the west than previously reported. BAs appear predisposed to DD, whereas other ethnic differences appear conserved following migration.

Abnormal colonic cholinergic and nitrergic activities in relation to elastosis in uncomplicated diverticular disease

I read with interest the review on the pathogenesis of diverticular disease by Commane et al in World J Gastroenterol 2009; 15(20): 2479-2488. However, I would like to discuss several important errors that the authors made whilst citing information from previously published work on the neuromuscular dysfunction in the disease.

Diverticular disease is associated with an enteric neuropathy as revealed by morphometric analysis

BACKGROUND

The pathogenesis of diverticular disease (DD) is attributed to several aetiological factors (e.g. age, diet, connective tissue disorders) but also includes distinct intestinal motor abnormalities. Although the enteric nervous system (ENS) is the key-regulator of intestinal motility, data on neuropathological alterations are limited. The study aimed to investigate the ENS by a systematic morphometric analysis.

METHODS

Full-thickness sigmoid specimens obtained from patients with symptomatic DD (n = 27) and controls (n = 27) were processed for conventional histology and immunohistochemistry using anti-HuC/D as pan-neuronal marker. Enteric ganglia, nerve and glial cells were quantified separately in the myenteric, external and internal submucosal plexus compartments.

KEY RESULTS

Compared to controls, patients with DD showed significantly (P < 0.05) (i) reduced neuronal density in all enteric nerve plexus, (ii) decrease of ganglionic nerve cell content in the myenteric plexus, (iii) decreased ganglionic density in the internal submucosal plexus, (iv) reduced glial cell density in the myenteric plexus, (v) decrease of ganglionic glial cell content in the myenteric plexus and increase in submucosal plexus compartments, (vi) increased glia index in all enteric nerve plexus. About 44.4% of patients with DD exhibited myenteric ganglia displaying enteric gliosis.

CONCLUSIONS & INFERENCES

Patients with DD show substantial structural alterations of the ENS mainly characterized by myenteric and submucosal oligo-neuronal hypoganglionosis which may account for intestinal motor abnormalities reported in DD. The morphometric data give evidence that DD is associated with structural alterations of the ENS which may complement established pathogenetic concepts.

Diverticular disease: A therapeutic overview

Formation of colonic diverticula, via herniation of the colonic wall, is responsible for the development of diverticulosis. When diverticulosis becomes symptomatic, it becomes diverticular disease. Diverticular disease is common in Western and industrialized countries, and it is associated with numerous abdominal symptoms (including pain, bloating, nausea, diarrhea, and constipation). Standard medical therapies with antibiotics are currently recommended for patients affected by diverticular disease. However, changing concepts on the pathophysiology of the disease suggest that diverticular disease may share many of the hallmarks of inflammatory bowel diseases. On this basis, the addition of therapies using mesalazine and probiotics may enhance treatment efficacy by shortening the course of the disease and preventing recurrences.

Review article: the current and evolving treatment of colonic diverticular disease

BACKGROUND

Formation of colonic diverticula, via herniation of the colonic wall, is responsible for the development of diverticulosis and consequently diverticular disease. Diverticular disease can be associated with numerous debilitating abdominal and gastrointestinal symptoms (including pain, bloating, nausea, constipation and diarrhoea).

AIMS

To review the state of treatment for diverticular disease and its complications, and briefly discuss potential future therapies.

METHODS

PubMed and recent conference abstracts were searched for articles describing the treatment of diverticular disease.

RESULTS

Many physicians will recommend alterations to lifestyle and increasing fibre consumption. Empirical antibiotics remain the mainstay of therapy for patients with diverticular disease and rifaximin seems to be the best choice. In severe or relapsing disease, surgical intervention is often the only remaining treatment option. Although novel treatment options are yet to become available, the addition of therapies based on mesalazine (mesalamine) and probiotics may enhance treatment efficacy.

CONCLUSIONS

Data suggest that diverticular disease may share many of the hallmarks of other, better-characterized inflammatory bowel diseases; however, treatment options for patients with diverticular disease are scarce, revolving around antibiotic treatment and surgery. There is a need for a better understanding of the fundamental mechanisms of diverticular disease to design treatment regimens accordingly.

Diet, ageing and genetic factors in the pathogenesis of diverticular disease

Diverticular disease (DD) is an age-related disorder of the large bowel which may affect half of the population over the age of 65 in the UK. This high prevalence ranks it as one of the most common bowel disorders in western nations. The majority of patients remain asymptomatic but there are associated life-threatening co-morbidities, which, given the large numbers of people with DD, translates into a considerable number of deaths per annum. Despite this public health burden, relatively little seems to be known about either the mechanisms of development or causality. In the 1970s, a model of DD formulated the concept that diverticula occur as a consequence of pressure-induced damage to the colon wall amongst those with a low intake of dietary fiber. In this review, we have examined the evidence regarding the influence of ageing, diet, inflammation and genetics on DD development. We argue that the evidence supporting the barotrauma hypothesis is largely anecdotal. We have also identified several gaps in the knowledge base which need to be filled before we can complete a model for the etiology of diverticular disease.

Lower gastrointestinal functions

The human colon serves to absorb water and electrolytes, store intraluminal contents until elimination is socially convenient, and salvage nutrients by bacterial metabolism of carbohydrates that have not been absorbed in the small intestine. The anorectum is responsible for fecal continence and defecation. This article is a broad perspective of the current status and a personal perspective of future challenges in understanding lower gastrointestinal functions in health and disease in humans.