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

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.

Diverticular Disease Worsening Is Associated with Increased Oxidative Stress and Gut Permeability: New Insights by Circulating Biomarkers

Diverticular disease (DD) management is impaired by its pathogenesis, which is still not completely defined, with an unmet clinical need for improved therapies. Ex vivo DD human models demonstrated the presence of a transmural oxidative imbalance that supports an ischemic pathogenesis. This study aimed to assess, with the use of circulating biomarkers, insights into DD pathogenesis and possible therapeutic targets. Nox2-derived peptide, H2O2, antioxidant capacity, isoprostanes, thromboxanes, TNF-α, LPS and zonulin were evaluated by ELISA in healthy subjects (HS) and asymptomatic and symptomatic DD patients. Compared to HS, DD patients presented low antioxidant capacity and increase in sNox2-dp, H2O2 and isoprostanes paralleled to a TNFα increase, lower than that of oxidative markers. TxB2 production correlated to Nox2 and isoprostanes, suggesting platelet activation. An increase in zonulin and LPS highlighted the role of gut permeability and LPS translocation in DD pathogenesis. The increase of all the markers statistically correlated with DD severity. The present study confirmed the presence of a main oxidative imbalance in DD and provides evidence of platelet activation driven by LPS translocation. The use of circulating biomarkers could represent a new clinical tool for monitoring disease progression and validate therapeutic strategies never tested in DD as antioxidant supplementation.

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.

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.

The management of diverticulitis: a review of the guidelines

Radiological evidence of inflammation, using computed tomography (CT), is needed to diagnose the first occurrence of diverticulitis. CT is also warranted when the severity of symptoms suggests that perforation or abscesses have occurred. Diverticulitis is classified as complicated or uncomplicated based on CT scan, severity of symptoms and patient history; this classification is used to direct management. Outpatient treatment is recommended in afebrile, clinically stable patients with uncomplicated diverticulitis. For patients with uncomplicated diverticulitis, antibiotics have no proven benefit in reducing the duration of the disease or preventing recurrence, and should only be used selectively. For complicated diverticulitis, non-operative management, including bowel rest and intravenous antibiotics, is indicated for small abscesses; larger abscesses of 3-5 cm should be drained percutaneously. Patients with peritonitis and sepsis should receive fluid resuscitation, rapid antibiotic administration and urgent surgery. Surgical intervention with either Hartmann procedure or primary anastomosis, with or without diverting loop ileostomy, is indicated for peritonitis or in failure of non-operative management. Colonoscopy is recommended for all patients with complicated diverticulitis 6 weeks after CT diagnosis of inflammation, and for patients with uncomplicated diverticulitis who have suspicious features on CT scan or who otherwise meet national bowel cancer screening criteria.

Does Colonic Diverticulosis Raise the Risk of Colorectal Adenoma in Patients with Colorectal Cancer?

Background

The aim of this study was to evaluate the risk of development of colorectal adenomas in patients with colorectal cancer (CRC) with and without colonic diverticulosis.

Methods

We performed a retrospective cohort study that included patients with CRC between 2008 and 2011. All patients underwent preoperative colonoscopic and barium enema examinations. Follow-up colonoscopic examinations were performed within 1 year and between 3 and 5 years postoperatively. The incidence of colorectal adenomas was compared based on the presence or absence of diverticulosis. Additionally, multivariate logistic regression analysis was performed to identify the factors independently associated with the development of synchronous and metachronous colorectal adenomas.

Results

Of the 168 patients with CRC included in the study, 55 showed colonic diverticulosis. Synchronous colorectal adenomas were more common in CRC patients with diverticulosis than in those without diverticulosis (P > 0.001). Multivariate regression analysis showed that colonic diverticulosis (odds ratio (OR) 3.874, 95% confidence interval (CI) 1.843–8.144, P > 0.001) and obesity (body mass index > 25.0 kg/m², OR 2.395, 95% CI 1.089–5.270, P = 0.030) were associated with an increased risk of synchronous colorectal adenomas. The presence of synchronous colorectal adenomas increased the risk of metachronous colorectal adenomas (OR 4.407, 95% CI 1.855–10.473, P > 0.001).

Conclusions

Colonic diverticulosis was associated with synchronous colorectal adenomas in patients with CRC, which is eventually increasing the risk of metachronous adenomas.

Genome-wide association analyses identify 39 new susceptibility loci for diverticular disease

Diverticular disease is common and has a high morbidity. Treatments are limited owing to the poor understanding of its pathophysiology. Here, to elucidate its etiology, we performed a genome-wide association study of diverticular disease (27,444 cases; 382,284 controls) from the UK Biobank and tested for replication in the Michigan Genomics Initiative (2,572 cases; 28,649 controls). We identified 42 loci associated with diverticular disease; 39 of these loci are novel. Using data-driven expression-prioritized integration for complex traits (DEPICT), we show that genes in these associated regions are significantly enriched for expression in mesenchymal stem cells and multiple connective tissue cell types and are co-expressed with genes that have a role in vascular and mesenchymal biology. Genes in these associated loci have roles in immunity, extracellular matrix biology, cell adhesion, membrane transport and intestinal motility. Phenome-wide association analysis of the 42 variants shows a common etiology of diverticular disease with obesity and hernia. These analyses shed light on the genomic landscape of diverticular disease.

Epidemiology and Pathophysiology of Diverticular Disease

Colonic diverticular disease is a common health care issue which has historically been attributed to western countries and older age population. Recent studies have shown a rise in incidence among developing countries that have adopted western diets as well as rise in prevalence among younger patients. In this article, the authors discuss the incidence, epidemiology, and pathophysiology of colonic diverticular disease.

Laparoscopically Assisted Reversal of Hartmann's Procedure for Perforated Diverticulitis

The aim of this study was to retrospectively review the clinical outcomes of laparoscopically assisted and open surgical reversal of Hartmann's procedure (HR). We reviewed all patients undergoing laparoscopic or open HR at Tri-Service General Hospital, Taipei, Taiwan, between January 2002 and January 2010. A total of 34 perforated diverticulitis patients initially treated by exploratory laparotomy with Hartmann's procedure were enrolled and divided into 2 groups: laparoscopic and open HR. Data relative to patient age at the time of HR, sex, body mass index, operative time, longest incision length, estimated blood loss, intraoperative complications, postoperative complications, time to bowel function return, duration of hospitalization, and length of follow-up were reviewed. The median colostomy closure period was significantly higher in the laparoscopic group than in the open group (P = 0.011). The median longest incision length, estimated blood loss, time to first oral intake, and hospital stay were significantly lower in the laparoscopic group compared with the open group. Laparoscopic HR may be a technically safe, feasible approach that provides better cosmesis, less blood loss, and faster recovery compared with open HR.

Role of cyclooxygenase isoforms in the altered excitatory motor pathways of human colon with diverticular disease

BACKGROUND AND PURPOSE

The COX isoforms (COX-1, COX-2) regulate human gut motility, although their role under pathological conditions remains unclear. This study examines the effects of COX inhibitors on excitatory motility in colonic tissue from patients with diverticular disease (DD).

EXPERIMENTAL APPROACH

Longitudinal muscle preparations, from patients with DD or uncomplicated cancer (controls), were set up in organ baths and connected to isotonic transducers. Indomethacin (COX-1/COX-2 inhibitor), SC-560 (COX-1 inhibitor) or DFU (COX-2 inhibitor) were assayed on electrically evoked, neurogenic, cholinergic and tachykininergic contractions, or carbachol- and substance P (SP)-induced myogenic contractions. Distribution and expression of COX isoforms in the neuromuscular compartment were assessed by RT-PCR, Western blot and immunohistochemical analysis.

KEY RESULTS

In control preparations, neurogenic cholinergic contractions were enhanced by COX inhibitors, whereas tachykininergic responses were blunted. Carbachol-evoked contractions were increased by indomethacin or SC-560, but not DFU, whereas all inhibitors reduced SP-induced motor responses. In preparations from DD patients, COX inhibitors did not affect electrically evoked cholinergic contractions. Both indomethacin and DFU, but not SC-560, decreased tachykininergic responses. COX inhibitors did not modify carbachol-evoked motor responses, whereas they counteracted SP-induced contractions. COX-1 expression was decreased in myenteric neurons, whereas COX-2 was enhanced in glial cells and smooth muscle.

CONCLUSIONS AND IMPLICATIONS

In control colon, COX-1 and COX-2 down-regulate cholinergic motility, whereas both isoforms enhance tachykininergic motor activity. In the presence of DD, there is a loss of modulation by both COX isoforms on the cholinergic system, whereas COX-2 displays an enhanced facilitatory control on tachykininergic contractile activity.

Changes in the response to excitatory antagonists, agonists, and spasmolytic agents in circular colonic smooth muscle strips from patients with diverticulosis

BACKGROUND

Colonic samples from asymptomatic diverticulosis (DS) patients presented enhanced electrical field stimulation (EFS)-contractions, in an earlier study of ours, suggesting increased endogenous responses. The aim of this study was to explore changes in excitatory neuromuscular transmission and to assess the pharmacodynamics of spasmolytic agents in DS.

METHODS

Circular muscle strips from sigmoid colon of DS patients (n = 30; 69.5 ± 14.8 years) and controls (n = 32; 64.7 ± 16.2 years) were studied using organ baths to evaluate the direct effect of excitatory agonists (carbachol, neurokinin A [NKA] and substance P [SP]), and the effect of antagonists (atropine and NK2 antagonist GR94800) and spasmolytic drugs (otilonium bromide [OB] and N-butyl-hyoscine) on the contractions induced by EFS-stimulation of excitatory motorneurons. qRT-PCR was also performed to compare mRNA expression of M2 , M3 , NK2 receptors and L-type calcium channels.

KEY RESULTS

Contractions to carbachol (Emax : 663.7 ± 305.6% control vs 2698.0 ± 439.5% DS; p < 0.0005) and NKA (Emax : 387.8 ± 35.6% vs 1102.0 ± 190.1%; p < 0.0005) were higher in DS group, without differences for SP. Higher potency for DS patients was observed in the concentration-response curves for atropine (pIC50  = 8.56 ± 0.15 control vs pIC50  = 9.95 ± 0.18 DS group; p < 0.005) and slightly higher for GR94800 (pIC50  = 7.21 ± 0.18 control vs pIC50  = 7.97 ± 0.32 group; p < 0.0001). Lower efficacy (Emax ) and potency (pIC50 ) was observed for spasmolytic drugs in DS, whereas no differences were found regarding the relative expression of the receptors evaluated between groups.

CONCLUSIONS & INFERENCES

The greater response to cholinergic and tachykinergic agonists and greater potency for muscarinic and NK2 antagonists observed in DS might play a role in the spasticity found in diverticular disease.

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.

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.

Plasma serotonin level in left-sided colonic diverticulosis: A pilot study

Neurotransmitters might participate in the development of diverticular disease. We measured fasting and postprandial serotonin levels in colonic diverticulosis patients and healthy volunteers. We demonstrated significantly lower maximal concentrations of serotonin in patients than the controls (respectively 109.8±61.4 and 251.3±44.1 ng/ml, p<0.001) as well as lower serotonin minimal values (respectively 38.4±21.8 and 124.6±41.4 ng/ml, p<0.001) and areas under time-course curves (respectively 288.8±139.8 and 739±167.4 ng/ml, p<0.001); significant difference between alternating pattern and normal bowel habit concerning fasting serotonin level, the hormone response to test meal (p=0.041) as well as minimal serotonin level (p=0.044). Bowel habit was also related to peak serotonin values following a test meal with 38.5 ng/ml in constipation, 139.5 ng/ml in diarrhea, 122.4 ng/ml in alternating pattern and 249 ng/ml in subjects with normal bowel habit (p=0.040) as well as AUC with 120.8 ng/ml in constipation, 416 ng/ml in diarrhea, 298 ng/ml in alternating pattern and 684 ng/ml in subjects with normal bowel habit (p=0.043). We demonstrated substantial differences in fasting serum serotonin levels as well as the hormone response to a test meal between colonic diverticulosis patients and healthy individuals, which seemed to be associated with abnormal bowel habits rather than presence of diverticula.

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.

Perception and the origin of symptoms in diverticular disease

Colonic diverticulosis is a common condition and although the majority of patients are asymptomatic up to 20% experience altered bowel habit and abdominal pain. The mechanisms underlying these symptoms are unclear but several theories now exist. This article briefly outlines a model of GI perception and then highlights past and current theories that may explain the development of symptoms in patients with diverticulosis.