Relationships Between Distention-, Butyrate- and Pellet-Induced Stimulation of Peristalsis in the Mouse Colon

Preparation methods, structural characteristics, and biological activity of polysaccharides from Platycodon grandiflorus

Platycodon grandiflorus (P. grandiflorus), a traditional Chinese medicinal herb used for both medicine and food, has a long history of treating respiratory infections, bronchitis, pneumonia, and other lung-related diseases. The therapeutic effects of P. grandiflorus are attributed to its chemical components, including polysaccharides. Among these components, Platycodon grandiflorus polysaccharides (PGP) are recognized as one of the most important and abundant active ingredients, exhibiting various biological activities such as prebiotic, antioxidant, antiviral, anticancer, antiangiogenic, and immune regulatory properties. Incorporating the principles of traditional Chinese medicine, carrier concepts, and modern targeted drug delivery technologies, PGP can influence the target sites and therapeutic effects of other drugs while also serving as a drug carrier for targeted and precise treatments. Therefore, it is essential to provide a comprehensive review of the extraction, separation, purification, physicochemical properties, and biological activities of PGP. In the future, by integrating new concepts, technologies, and processes, further references and guidance can be provided for the comprehensive development of PGP. This will contribute to the advancement of P. grandiflorus in various fields such as pharmaceuticals, health products, and food.

Combination of fenchone and sodium hyaluronate ameliorated constipation-predominant irritable bowel syndrome and underlying mechanisms

We sought to explore the protective effect of the combination of fenchone (FE) and sodium hyaluronate (SH) on ice water-induced IBS-C rats and the potential mechanism. The neurotransmitter levels, including substance P (SP), motilin (MTL), 5-hydroxytryptamine (5-HT), and vasoactive intestinal peptide (VIP), were determined by ELISA methods. The stem cell factors (SCF)/c-Kit signaling pathway-related protein and mRNA levels were determined by western blot and reverse transcription quantitative polymerase chain reaction (RT-qPCR) analyses, respectively. The expressions of tight ZO-1, Occludin, and Claudin-1 were also measured by western blot assay and immunofluorescence staining. The 16S rRNA gene sequence was used to measure the composition of gut microbiota. The co-administration of FE and SH improved the body weight, number of fecal pellets, fecal moisture, abdominal with drawal reflex score, and gastrointestinal transit rate in IBS-C rats. The unique efficacy of combination depended on the regulation of balance between excitatory and inhibitory neurotransmitters, enhancement of intestinal barrier function, and activation of SCF/c-Kit pathway. The gut microbiota structure was also restored. The ability of FE combined with SH to regulate SCF/c-Kit signaling pathway, enhance intestinal barrier function, and modulate gut microbiota contributes to their efficacy in managing IBS-C in rats.

Circadian rhythms in colonic function

A rhythmic expression of clock genes occurs within the cells of multiple organs and tissues throughout the body, termed "peripheral clocks." Peripheral clocks are subject to entrainment by a multitude of factors, many of which are directly or indirectly controlled by the light-entrainable clock located in the suprachiasmatic nucleus of the hypothalamus. Peripheral clocks occur in the gastrointestinal tract, notably the epithelia whose functions include regulation of absorption, permeability, and secretion of hormones; and in the myenteric plexus, which is the intrinsic neural network principally responsible for the coordination of muscular activity in the gut. This review focuses on the physiological circadian variation of major colonic functions and their entraining mechanisms, including colonic motility, absorption, hormone secretion, permeability, and pain signalling. Pathophysiological states such as irritable bowel syndrome and ulcerative colitis and their interactions with circadian rhythmicity are also described. Finally, the classic circadian hormone melatonin is discussed, which is expressed in the gut in greater quantities than the pineal gland, and whose exogenous use has been of therapeutic interest in treating colonic pathophysiological states, including those exacerbated by chronic circadian disruption.

Complementary mechanisms of modulation of spontaneous phasic contractions by the gaseous signalling molecules NO, H2S, HNO and the polysulfide Na2S3 in the rat colon

OBJECTIVES

Reactive oxygen and nitrogen species may be produced during inflammation leading to the formation of NO, H2S or HNO. Enzymes such as iNOS, CSE and CBS might also be responsible for polysulfide production. Since these signalling molecules might have an impact on colonic motility, the aim of this study was to compare their effect on rat colonic slow phasic contractions (SPC).

METHODS

Organ bath measurements with strips obtained from rat proximal colon were performed using the polysulfide Na2S3, sodium nitroprusside (NaNP), sodium hydrogen sulfide (NaHS), Angeli's salt as NO, H2S, and HNO donors, respectively. TTX (1 µM) was used to block neuronal activity.

RESULTS

All four molecules, concentration-dependently, inhibited the amplitude and frequency of SPC both in the circular and longitudinal muscle layer. The relative potency was NaNP>Angeli's salt>NaHS>Na2S3. The inhibitory response induced by NaNP (1 µM) and Angeli's salt (50 µM) was reversed by ODQ (10 µM) whereas the inhibitory effect of NaHS (1 mM) was reversed by apamin (1 µM) and glibenclamide (10 µM). Na2S3 (1 mM) response was partially reversed by apamin (1 µM) and glibenclamide (10 µM). High concentrations of Na2S3 caused an increase in tone. Low concentrations of NaHS or Na2S3 did not potentiate NaNP responses.

CONCLUSIONS

All signalling molecules inhibit SPC in both muscle layers. The effect is independent of neural activity and involves guanylyl cyclase (NO and HNO) and SKCa and KATP channels (NaHS or Na2S3). Other pathways might also be involved in Na2S3 responses. Accordingly, complementary mechanisms of inhibition might be attributable to these signalling molecules.

Improvement of loperamide-hydrochloride-induced intestinal motility disturbance by Platycodon grandiflorum polysaccharides through effects on gut microbes and colonic serotonin

Constipation is a common gastrointestinal symptom characterized by intestinal motility disorder. The effects of Platycodon grandiflorum polysaccharides (PGP) on intestinal motility have not been confirmed. We established a rat model of constipation induced by loperamide hydrochloride to elucidate the therapeutic effect of PGP on intestinal motility disorder and to explore the possible mechanism. After PGP treatment (400 and 800 mg/kg) for 21 d, PGP clearly relieved gastrointestinal motility, including fecal water content, gastric emptying rate, and intestinal transit rate. Moreover, the secretion of motility-related hormones, gastrin and motilin, were increased. Enzyme-linked immunosorbent assay, western blot, immunohistochemistry, and immunofluorescence results confirmed that PGP significantly increased the secretion of 5-hydroxytryptamine (5-HT) and the expression of related proteins, such as tryptophan hydroxylase 1, 5-HT4 receptor, and transient receptor potential ankyrin 1. 16S rRNA gene sequencing showed that PGP significantly increased the relative abundance of Roseburia, Butyricimonas, and Ruminiclostridium, which were positively correlated with 5-HT levels. However, the relative abundance of Clostridia_UCG-014, Lactobacillus, and Enterococcus were decreased. PGP improved intestinal transport by regulating the levels of 5-HT, which interacts with the gut microbiota and the intestinal neuro-endocrine system, further affecting constipation. Overall, PGP is a potential supplement for the treatment of constipation.

Crosstalk between the Gut Microbiome and Colonic Motility in Chronic Constipation: Potential Mechanisms and Microbiota Modulation

Chronic constipation (CC) is a highly prevalent and burdensome gastrointestinal disorder. Accumulating evidence highlights the link between imbalances in the gut microbiome and constipation. However, the mechanisms by which the microbiome and microbial metabolites affect gut movement remain poorly understood. In this review, we discuss recent studies on the alteration in the gut microbiota in patients with CC and the effectiveness of probiotics in treating gut motility disorder. We highlight the mechanisms that explain how the gut microbiome and its metabolism are linked to gut movement and how intestinal microecological interventions may counteract these changes based on the enteric nervous system, the central nervous system, the immune function, and the ability to modify intestinal secretion and the hormonal milieu. In particular, microbiota-based approaches that modulate the levels of short-chain fatty acids and tryptophan catabolites or that target the 5-hydroxytryptamine and Toll-like receptor pathways may hold therapeutic promise. Finally, we discuss the existing limitations of microecological management in treating constipation and suggest feasible directions for future research.

Are all dietary fibers equal for patients with inflammatory bowel disease? A systematic review of randomized controlled trials

CONTEXT

Conflicting practice-based dietary recommendations are sometimes given to patients with inflammatory bowel disease (IBD); whereas intake of fiber should increase during remission, it should be avoided during relapse. Moreover, European countries set daily requirements of total fiber and do not specify any types.

OBJECTIVE

This systematic review appraised data from randomized clinical trials (RCTs) of the types of fibers beneficial for patients in the treatment of IBD to guide dietary fiber advice.

DATA SOURCES

The PubMED database was searched following PRISMA guidelines.

DATA EXTRACTION

RCTs evaluating the effects of any type of fiber on clinical and physiological outcomes in patients with IBD were assessed. Quality assessment of the selected full-text articles was conducted using the Cochrane Risk of Bias Tool.

DATA ANALYSIS

Eight studies were included reporting on 5 types of fibers. In 2 RCTs, germinated barley foodstuff (GBF) was shown to lower pro-inflammatory cytokines and clinical disease activity scores. Fructo-oligosaccharides (FOS) were demonstrated to lower IBD Questionnaire scores (lower well-being), in contrast to inulin, which decreased disease activity scores. An RCT could not find lower remission rates in the psyllium treatment group, while another RCT reported that administration led to less symptoms in patients. In RCTs, no concrete evidence was found that wheat bran improves disease course.

CONCLUSIONS

Although the evidence is sparse, GBF and inulin seem propitious and merit further exploration. Evidence on wheat bran and psyllium is still too limited. Adequately powered long-term human RCTs with objective outcomes are needed to improve dietary advice on types of fiber in IBD.

Long range synchronization within the enteric nervous system underlies propulsion along the large intestine in mice

How the Enteric Nervous System (ENS) coordinates propulsion of content along the gastrointestinal (GI)-tract has been a major unresolved issue. We reveal a mechanism that explains how ENS activity underlies propulsion of content along the colon. We used a recently developed high-resolution video imaging approach with concurrent electrophysiological recordings from smooth muscle, during fluid propulsion. Recordings showed pulsatile firing of excitatory and inhibitory neuromuscular inputs not only in proximal colon, but also distal colon, long before the propagating contraction invades the distal region. During propulsion, wavelet analysis revealed increased coherence at ~2 Hz over large distances between the proximal and distal regions. Therefore, during propulsion, synchronous firing of descending inhibitory nerve pathways over long ranges aborally acts to suppress smooth muscle from contracting, counteracting the excitatory nerve pathways over this same region of colon. This delays muscle contraction downstream, ahead of the advancing contraction. The mechanism identified is more complex than expected and vastly different from fluid propulsion along other hollow smooth muscle organs; like lymphatic vessels, portal vein, or ureters, that evolved without intrinsic neurons.

Motor patterns in the proximal and distal mouse colon which underlie formation and propulsion of feces

BACKGROUND

In herbivores, the proximal and distal colonic regions feature distinct motor patterns underlying formation and propulsion of fecal pellets, respectively. Omnivores, such as mice and humans, lack a similar clear anatomical transition between colonic regions. We investigated whether distinct processes form and propel content along the large intestine of a mouse (an omnivore).

METHODS

We recorded propulsive and non-propulsive neurogenic motor activity in mouse large intestine under six different stimulus conditions of varying viscosities. Gut wall movements were recorded by video and smooth muscle electrical behavior recorded with extracellular suction electrodes.

KEY RESULTS

Three major neurally mediated motor patterns contributed to pellet formation and propulsion. (1) Pellet-shaped boluses are pinched off near the ceco-colonic junction and slowly propelled distally to a transition located at 40% length along the colon. (2) At this functional colonic flexure, propulsion speed is significantly increased by self-sustaining neural peristalsis. Speed transition at this location also occurs with artificial pellets and with spontaneously formed boluses in the empty colon. (3) Periodic colonic motor complexes (CMCs) were present in all conditions reaching a maximal frequency of about 0.4 cpm and extending across the proximal and distal colon with faster speed of propagation.

CONCLUSIONS AND INFERENCES

The three motor patterns share a unique underlying fundamental property of the enteric circuits, which involve extended ensembles of enteric neurons firing at close to 2 Hz. The demonstration of distinct functional differences between proximal and distal colon in rabbit, guinea pig, and now mouse raises the possibility that this may be an organizational principle in other mammalian species, including humans.

Characterization of alternating neurogenic motor patterns in mouse colon

BACKGROUND

Colonic motor complexes (CMCs) have been widely recorded in the large intestine of vertebrates. We have investigated whether in the smooth muscle, a single unified pattern of electrical activity, or different patterns of electrical activity give rise to the different neurogenic patterns of motility underlying CMCs in vitro.

METHODS

To study differences of the CMCs between proximal and distal colon, we used a novel combination of techniques to simultaneously record muscle diameter and force at multiple sites along the whole mouse colon ex vivo. In addition, electrical activity of smooth muscle was recorded by suction electrodes.

KEY RESULTS

Two distinct types of CMCs were distinguished; CMCs that propagated along the entire colon (complete CMC) and CMCs which were restricted to the proximal colon (incomplete CMC). The two types of CMC often occurred in the same preparations. Incomplete CMCs had longer bursts of smooth muscle action potentials than complete CMCs and propagated more slowly. Interestingly, both types of CMC were associated with similar frequency bursts of smooth muscle action potentials at ~2.4 Hz. In the most proximal colon, an additional firing frequency was detected close to ~7 Hz generating multiple peaks within each CMC.

CONCLUSIONS & INFERENCES

We report distinct characteristics underlying complete and incomplete CMCs in isolated mouse colon. Recognizing these distinct patterns of motility will be important for future interpretation of analysis of murine colonic motility recordings. The identification of alternating patterns of motor activity in proximal colon, but not distal colon may reflect specific neural mechanisms for fecal pellet formation.

Control of colonic motility using electrical stimulation to modulate enteric neural activity

Electrical stimulation of the enteric nervous system (ENS) is an attractive approach to modify gastrointestinal transit. Colonic motor complexes (CMCs) occur with a periodic rhythm, but the ability to elicit a premature CMC depends, at least in part, upon the intrinsic refractory properties of the ENS, which are presently unknown. The objectives of this study were to record myoelectric complexes (MCs, the electrical correlates of CMCs) in the smooth muscle and 1) determine the refractory periods of MCs, 2) inform and evaluate closed-loop stimulation to repetitively evoke MCs, and 3) identify stimulation methods to suppress MC propagation. We dissected the colon from male and female C57BL/6 mice, preserving the integrity of intrinsic circuitry while removing the extrinsic nerves, and measured properties of spontaneous and evoked MCs in vitro. Hexamethonium abolished spontaneous and evoked MCs, confirming the necessary involvement of the ENS for electrically evoked MCs. Electrical stimulation reduced the mean interval between evoked and spontaneous CMCs (24.6 ± 3.5 vs. 70.6 ± 15.7 s, P = 0.0002, n = 7). The absolute refractory period was 4.3 s (95% confidence interval (CI) = 2.8-5.7 s, R2 = 0.7315, n = 8). Electrical stimulation applied during fluid distention-evoked MCs led to an arrest of MC propagation, and following stimulation, MC propagation resumed at an increased velocity (n = 9). The timing parameters of electrical stimulation increased the rate of evoked MCs and the duration of entrainment of MCs, and the refractory period provides insight into timing considerations for designing neuromodulation strategies to treat colonic dysmotility.NEW & NOTEWORTHY Maintained physiological distension of the isolated mouse colon induces rhythmic cyclic myoelectric complexes (MCs). MCs evoked repeatedly by closed-loop electrical stimulation entrain MCs more frequently than spontaneously occurring MCs. Electrical stimulation delivered at the onset of a contraction temporarily suppresses the propagation of MC contractions. Controlled electrical stimulation can either evoke MCs or temporarily delay MCs in the isolated mouse colon, depending on timing relative to ongoing activity.

Short chain fatty acids and colon motility in a mouse model of irritable bowel syndrome

Background

Irritable bowel syndrome (IBS) is defined as a multifactorial disorder associated with visceral hypersensitivity, altered gut motility and dysfunction of the brain-gut axis. Gut microbiota and its metabolites are proposed as possible etiological factors of IBS. Short chain fatty acids (SCFAs) induce both inhibitory and stimulatory action on colon motility, however, their effects on the IBS model were not investigated. The aim of our study was to investigate the level of SFCAs in feces and their effects on colon motility in a mouse model of IBS.

Methods

IBS model was induced in mice by intracolonic infusion of 1% acetic acid during the early postnatal period. Mice colon hypersensitivity was assessed by the threshold of the abdominal withdrawal reflex in response to colorectal distention. Colon contractility was studied using proximal colon specimens in isometric conditions. Transit rates were assessed by the pellet propulsion in the isolated colon. Concentrations of SCFAs in feces were measured using gas–liquid chromatography.

Results

The concentration of SCFAs in feces of IBS model mice was higher compared to the control group. Visceral sensitivity to colorectal distension and colonic transit rate were increased indicating IBS with predominant diarrhea. The frequency and amplitude of spontaneous contractions of proximal colon segments from IBS mice were higher, but carbachol induced contractions were lower compared to control. During acute application of SCFAs (sodium propionate, sodium acetate or butyric acid) dose-dependently (0.5–30 mM) decreased tonic tension, frequency and amplitude of spontaneous and carbachol-evoked contractions. In the mouse IBS group the inhibitory effects SCFAs on spontaneous and carbachol-evoked contractions were less pronounced. At the same time intraluminal administration of butyrate (5 mM) increased the transit rate in the colon of both groups, but its stimulatory effect was more pronounced in mouse IBS model group.

Conclusion

Our data indicate that the increased transit rate in the mouse IBS model group is associated with a disbalance of activating and inhibiting action of SCFAs due to chronically elevated SCFA levels, which may impact the pathogenesis of IBS with predominant diarrhea syndrome.

Advances in colonic motor complexes in mice

The primary functions of the gastrointestinal (GI) tract are to absorb nutrients, water, and electrolytes that are essential for life. This is accompanied by the capability of the GI tract to mix ingested content to maximize absorption and effectively excrete waste material. There have been major advances in understanding intrinsic neural mechanisms involved in GI motility. This review highlights major advances over the past few decades in our understanding of colonic motor complexes (CMCs), the major intrinsic neural patterns that control GI motility. CMCs are generated by rhythmic coordinated firing of large populations of myenteric neurons. Initially, it was thought that serotonin release from the mucosa was required for CMC generation. However, careful experiments have now shown that neither the mucosa nor endogenous serotonin are required, although, evidence suggests enteroendocrine (EC) cells modulate CMCs. The frequency and extent of propagation of CMCs are highly dependent on mechanical stimuli (circumferential stretch). In summary, the isolated mouse colon emerges as a good model to investigate intrinsic mechanisms underlying colonic motility and provides an excellent preparation to explore potential therapeutic agents on colonic motility, in a highly controlled in vitro environment. In addition, during CMCs, the mouse colon facilitates investigations into the emergence of dynamic assemblies of extensive neural networks, applicable to the nervous system of different organisms.

Mucuna pruriens Administration Minimizes Neuroinflammation and Shows Anxiolytic, Antidepressant and Slimming Effects in Obese Rats

This study evaluated the effect of Mucuna pruriens (MP) administration on neuroinflammation and behavioral and murinometric parameters in obese rats. Proximate composition, oligosaccharide and phenolic compound profile of MP were determined. Wistar adult male rats were randomized into healthy (HG) and obese group (OG). The HG consumed a control chow diet while OG consumed a cafeteria diet for eight weeks. Then, they were subdivided into: Healthy (HG); Healthy with MP administration (HGMP); Obese (OG); Obese with MP administration (OGMP), with the consumption of the respective diets remaining for another eight weeks, in addition to gavage with MP extract to supplemented groups (750 mg/kg weight). MP presented a composition rich in proteins and phenolic compounds, especially catechin, in addition to 1-kestose and levodopa. Supplementation reduced food intake, body weight, and thoracic and abdominal circumferences in obese rats. MP showed anxiolytic and antidepressant effects and reduced morphological damage and expression of interleukin 6 in the hippocampus of obese rats. MP treatment showed satietogenic, slimming, anxiolytic and antidepressant effects, besides to minimizing hippocampal neuroinflammation in obese rats. Our results demonstrated the potential anti-obesity of MP which are probably related to the high content of bioactive compounds present in this plant extract.