Nutrient-induced changes in the phenotype and function of the enteric nervous system

Evaluation and Discrimination of Lipid Components and Iron and Zinc Levels in Chicken and Quail Eggs Available on the Polish Market

All over the world, birds' eggs are an important and valuable component of the human diet. This study aimed to compare the content of lipid components and their nutritional value as well as iron and zinc levels in chicken and quail eggs commonly available on the market. In egg lipids, unsaturated fatty acids were dominant, especially oleic acid, the content of which was about 40% of the total fatty acids (TFAs). Linoleic acid was the major polyunsaturated fatty acid. Compared to other products of animal origin, eggs were characterized by favorable values of lipid quality indices, especially the index of atherogenicity, thrombogenicity, and the hypocholesterolemic-to-hypercholesterolemic ratio. In the present study, no differences were found in the content of tested nutrients between eggs from different production methods (organic, free-range, barn, cages). Based on linear discriminant analysis, inter-breed differences were noticed. Cluster analysis showed that eggs enriched in n3 PUFAs (according to the producers' declarations) differed from other groups of chicken eggs. However, in eggs from one producer only, the amount of EPA and DHA exceeds 80 mg per 100 g, entitling the use of the nutrition claim on the package. Quail eggs differed from chicken eggs in FA profile and cholesterol and iron levels.

Fecal supernatants from dogs with idiopathic epilepsy activate enteric neurons

Introduction

Alterations in the composition and function of the gut microbiome have been reported in idiopathic epilepsy (IE), however, interactions of gut microbes with the enteric nervous system (ENS) in this context require further study. This pilot study examined how gastrointestinal microbiota (GIM), their metabolites, and nutrients contained in intestinal contents communicate with the ENS.

Methods

Fecal supernatants (FS) from healthy dogs and dogs with IE, including drug-naïve, phenobarbital (PB) responsive, and PB non-responsive dogs, were applied to cultured myenteric neurons to test their activation using voltage-sensitive dye neuroimaging. Additionally, the concentrations of short-chain fatty acids (SCFAs) in the FS were quantified.

Results

Our findings indicate that FS from all examined groups elicited neuronal activation. Notably, FS from PB non-responsive dogs with IE induced action potential discharge in a higher proportion of enteric neurons compared to healthy controls, which exhibited the lowest burst frequency overall. Furthermore, the highest burst frequency in enteric neurons was observed upon exposure to FS from drug-naïve dogs with IE. This frequency was significantly higher compared to that observed in PB non-responsive dogs with IE and showed a tendency to surpass that of healthy controls.

Discussion

Although observed disparities in SCFA concentrations across the various FS samples might be associated with the induced neuronal activity, a direct correlation remains elusive at this point. The obtained results hint at an involvement of the ENS in canine IE and set the basis for future studies.

Seasonal flexibility of the gut structure and physiology in Eremias multiocellata

Although gut seasonal plasticity has been extensively reported, studies on physiological flexibility, such as water-salt transportation and motility in reptiles, are limited. Therefore, this study investigated the intestinal histology and gene expression involved in water-salt transport (AQP1, AQP3, NCC, and NKCC2) and motility regulation (nNOS, CHRM2, and ADRB2) in desert-dwelling Eremias multiocellata during winter (hibernating period) and summer (active period). The results showed that mucosal thickness, the villus width and height, the enterocyte height of the small intestine, and the mucosal and submucosal thicknesses of the large intestine were greater in winter than in summer. However, submucosal thickness of the small intestine and muscularis thickness of the large intestine were lower in winter than in summer. Furthermore, AQP1, AQP3, NCC, nNOS, CHRM2, and ADRB2 expressions in the small intestine were higher in winter than in summer; AQP1, AQP3, and nNOS expressions in the large intestine were lower in winter than in summer, with the upregulation of NCC and CHRM2 expressions; no significant seasonal differences were found in intestinal NKCC2 expression. These results suggest that (i) intestinal water-salt transport activity is flexible during seasonal changes where AQP1, AQP3 and NCC play a vital role, (ii) the intestinal motilities are attenuated through the concerted regulation of nNOS, CHRM2, and ADRB2, and (iii) the physiological flexibility of the small and large intestine may be discrepant due to their functional differences. This study reveals the intestinal regulation and adaptation mechanisms in E. multiocellata in response to the hibernation season.

Who's talking to whom: microbiome-enteric nervous system interactions in early life

The enteric nervous system (ENS) is the intrinsic nervous system of the gastrointestinal tract (GI) and regulates important GI functions, including motility, nutrient uptake, and immune response. The development of the ENS begins during early organogenesis and continues to develop once feeding begins, with ongoing plasticity into adulthood. There has been increasing recognition that the intestinal microbiota and ENS interact during critical periods, with implications for normal development and potential disease pathogenesis. In this review, we focus on insights from mouse and zebrafish model systems to compare and contrast how each model can serve in elucidating the bidirectional communication between the ENS and the microbiome. At the end of this review, we further outline implications for human disease and highlight research innovations that can lead the field forward.

Methods to Study the Myenteric Plexus of Rat Small Intestine

The close interaction between the enteric nervous system, microbiome, and brain in vertebrates is an emerging topic of recent studies. Different species such as rat, mouse, and human are currently being used for this purpose, among others. The transferability of protocols for tissue isolation and sample collection is not always straightforward. Thus, the present work presents a new protocol for isolation and sample collection of rat myenteric plexus cells for in vivo as well as in vitro studies. With the methods and chemicals described in detail, a wide variety of investigations can be performed with regard to normal physiological as well as pathological processes in the postnatal developing enteric nervous system. The fast and efficient preparation of the intestine as the first step is particularly important. We have developed and described a LIENS chamber to obtain optimal tissue quality during intestinal freezing. Cryosections of the flat, snap-frozen intestine can then be prepared for histological examination of the various wall layers of the intestine, e.g. by immunohistochemistry. In addition, these cryosections are suitable for the preparation of defined regions, as shown here using the ganglia of the mesenteric plexus. This specific tissue was obtained by laser microdissection, making the presented methodology also suitable for subsequent analyses that require high quality (specificity) of the samples. Furthermore, we present here a fully modernized protocol for the cultivation of myenteric neurons from the rat intestine, which is suitable for a variety of in vitro studies.

Intestinal GPR119 activation by microbiota-derived metabolites impacts feeding behavior and energy metabolism

OBJECTIVE

The gastrointestinal tract affects physiological activities and behavior by secreting hormones and generating signals through the activation of nutrient sensors. GPR119, a lipid sensor, is indirectly involved in the secretion of incretins, such as glucagon-like peptide-1 and glucose-dependent insulinotropic peptide, by enteroendocrine cells, while it directly stimulates insulin secretion by pancreatic beta cells. Since GPR119 has the potential to modulate metabolic homeostasis in obesity and diabetes, it has attracted interest as a therapeutic target. However, previous studies have shown that the deletion of Gpr119 in mice does not affect glucose homeostasis and appetite in either basal or high-fat diet-fed conditions. Therefore, the present study aimed to explore the role of GPR119 signaling system in energy metabolism and feeding behavior in mice.

METHODS

Gpr119 knockout (KO) mice were generated using CRISPR-Cas9 gene-editing technology, and their feeding behavior and energy metabolism were evaluated and compared with those of wild type (WT) mice.

RESULTS

Upon inducing metabolic stress via food deprivation, Gpr119 KO mice exhibited lower blood glucose levels and a higher body weight reduction compared to WT mice. Although food intake in WT and KO mice were similar under free-feeding conditions, Gpr119 KO mice exhibited increased food intake when they were refed after 24 h of food deprivation. Further, food-deprived Gpr119 KO mice presented shorter post-meal intervals and lower satiety for second and later meals during refeeding, resulting in increased food intake. Associated with this meal pattern, levels of oleoylethanolamide (OEA), an endogenous agonist of GPR119, in the luminal contents of the distal gastrointestinal tract were elevated within 2 h after refeeding. The large-intestinal infusion of OEA prolonged post-meal intervals and increased satiety in the first meal, but not the second meal. On the other hand, infusion of oleic acid increased cecal OEA levels at 2 h from the beginning of infusion, while prolonging post-meal intervals and increasing satiety on the meals that occurred approximately 2 h after the infusion. Cecal OEA levels were low in antibiotic-treated mice, suggesting that the gut microbiota partially synthesizes OEA from oleic acid.

CONCLUSIONS

Collectively, our results indicate that the activation of gastrointestinal GPR119 by microbiota-produced OEA derived from oleic acid is associated with satiety control and energy homeostasis under energy shortage conditions.

Patchouli alcohol improved diarrhea-predominant irritable bowel syndrome by regulating excitatory neurotransmission in the myenteric plexus of rats

Background and Purpose: Irritable bowel syndrome (IBS) is usually associated with chronic gastrointestinal disorders. Its most common subtype is accompanied with diarrhea (IBS-D). The enteric nervous system (ENS) modulates major gastrointestinal motility and functions whose aberration may induce IBS-D. The enteric neurons are susceptible to long-term neurotransmitter level alterations. The patchouli alcohol (PA), extracted from Pogostemonis Herba, has been reported to regulate neurotransmitter release in the ENS, while its effectiveness against IBS-D and the underlying mechanism remain unknown. Experimental Approach: In this study, we established an IBS-D model in rats through chronic restraint stress. We administered the rats with 5, 10, and 20 mg/kg of PA for intestinal and visceral examinations. The longitudinal muscle myenteric plexus (LMMP) neurons were further immunohistochemically stained for quantitative, morphological, and neurotransmitters analyses. Key Results: We found that PA decreased visceral sensitivity, diarrhea symptoms and intestinal transit in the IBS-D rats. Meanwhile, 10 and 20 mg/kg of PA significantly reduced the proportion of excitatory LMMP neurons in the distal colon, decreased the number of acetylcholine (Ach)- and substance P (SP)-positive neurons in the distal colon and restored the levels of Ach and SP in the IBS-D rats. Conclusion and Implications: These findings indicated that PA modulated LMMP excitatory neuron activities, improved intestinal motility and alleviated IBS-induced diarrheal symptoms, suggesting the potential therapeutic efficacy of PA against IBS-D.

Crosstalk between the Gut and Brain in Ischemic Stroke: Mechanistic Insights and Therapeutic Options

There has been a significant amount of interest in the past two decades in the study of the evolution of the gut microbiota, its internal and external impacts on the gut, and risk factors for cerebrovascular disorders such as cerebral ischemic stroke. The network of bidirectional communication between gut microorganisms and their host is known as the microbiota-gut-brain axis (MGBA). There is mounting evidence that maintaining gut microbiota homeostasis can frequently enhance the effectiveness of ischemic stroke treatment by modulating immune, metabolic, and inflammatory responses through MGBA. To effectively monitor and cure ischemic stroke, restoring a healthy microbial ecology in the gut may be a critical therapeutic focus. This review highlights mechanistic insights on the MGBA in disease pathophysiology. This review summarizes the role of MGBA signaling in the development of stroke risk factors such as aging, hypertension, obesity, diabetes, and atherosclerosis, as well as changes in the microbiota in experimental or clinical populations. In addition, this review also examines dietary changes, the administration of probiotics and prebiotics, and fecal microbiota transplantation as treatment options for ischemic stroke as potential health benefits. It will become more apparent how the MGBA affects human health and disease with continuing advancements in this emerging field of biomedical sciences.

Environmental perception and control of gastrointestinal immunity by the enteric nervous system

The enteric nervous system (ENS) forms a versatile sensory system along the gastrointestinal tract that interacts with most cell types in the bowel. Herein, we portray host-environment interactions at the intestinal mucosal surface through the lens of the enteric nervous system. We describe local cellular interactions as well as long-range circuits between the enteric, central, and peripheral nervous systems. Additionally, we discuss recently discovered mechanisms by which enteric neurons and glia respond to biotic and abiotic environmental changes and how they regulate intestinal immunity and inflammation. The enteric nervous system emerges as an integrative sensory system with manifold immunoregulatory functions under both homeostatic and pathophysiological conditions.

Enteric nervous system modulation of luminal pH modifies the microbial environment to promote intestinal health

The enteric nervous system (ENS) controls many aspects of intestinal homeostasis, including parameters that shape the habitat of microbial residents. Previously we showed that zebrafish lacking an ENS, due to deficiency of the sox10 gene, develop intestinal inflammation and bacterial dysbiosis, with an expansion of proinflammatory Vibrio strains. To understand the primary defects resulting in dysbiosis in sox10 mutants, we investigated how the ENS shapes the intestinal environment in the absence of microbiota and associated inflammatory responses. We found that intestinal transit, intestinal permeability, and luminal pH regulation are all aberrant in sox10 mutants, independent of microbially induced inflammation. Treatment with the proton pump inhibitor, omeprazole, corrected the more acidic luminal pH of sox10 mutants to wild type levels. Omeprazole treatment also prevented overabundance of Vibrio and ameliorated inflammation in sox10 mutant intestines. Treatment with the carbonic anhydrase inhibitor, acetazolamide, caused wild type luminal pH to become more acidic, and increased both Vibrio abundance and intestinal inflammation. We conclude that a primary function of the ENS is to regulate luminal pH, which plays a critical role in shaping the resident microbial community and regulating intestinal inflammation.

GWAS of stool frequency provides insights into gastrointestinal motility and irritable bowel syndrome

Gut dysmotility is associated with constipation, diarrhea, and functional gastrointestinal disorders like irritable bowel syndrome (IBS), although its molecular underpinnings are poorly characterized. We studied stool frequency (defined by the number of bowel movements per day, based on questionnaire data) as a proxy for gut motility in a GWAS meta-analysis including 167,875 individuals from UK Biobank and four smaller population-based cohorts. We identify 14 loci associated with stool frequency (p ≤ 5.0 × 10^-8). Gene set and pathway analyses detected enrichment for genes involved in neurotransmitter/neuropeptide signaling and preferentially expressed in enteric motor neurons controlling peristalsis. PheWAS identified pleiotropic associations with dysmotility syndromes and the response to their pharmacological treatment. The genetic architecture of stool frequency correlates with that of IBS, and UK Biobank participants from the top 1% of stool frequency polygenic score distribution were associated with 5× higher risk of IBS with diarrhea. These findings pave the way for the identification of actionable pathological mechanisms in IBS and the dysmotility syndromes.

Effect of partial substitution of fishmeal with insect meal (Hermetia illucens) on gut neuromuscular function in Gilthead sea bream (Sparus aurata)

Alternative nutrient sources to fishmeal for fish feed, such as insect meals, represent a promising sustainable supply. However, the consequences for fish digestive function have not been exhaustively investigated. In the present study we evaluated the effect of partial fishmeal substitution with 10% Hermetia illucens (Hi10) larvae meal on the neuromuscular function of proximal and distal intestine in gilthead sea bream. In animals fed with insect meal, weight and growth parameters were similar to controls fed with conventional fishmeal. In addition, no anomalies in intestinal gross morphology and no overt signs of inflammation were observed. The gastrointestinal transit was significantly reduced in Hi10 fed animals. In the proximal and distal intestine longitudinal muscle, Hi10 feeding downregulated the excitatory cholinergic and serotoninergic transmission. Sodium nitroprusside-induced inhibitory relaxations increased in the proximal intestine and decreased in the distal intestine after Hi10 meal. Changes in the excitatory and inhibitory components of peristalsis were associated with adaptive changes in the chemical coding of both proximal and distal intestine myenteric plexus. However, these neuromuscular function alterations were not associated with considerable variations in morphometric growth parameters, suggesting that 10% Hi meal may represent a tolerable alternative protein source for gilthead sea bream diets.

The Interplay between Nutrition, Innate Immunity, and the Commensal Microbiota in Adaptive Intestinal Morphogenesis

The gastrointestinal tract is a functionally and anatomically segmented organ that is colonized by microbial communities from birth. While the genetics of mouse gut development is increasingly understood, how nutritional factors and the commensal gut microbiota act in concert to shape tissue organization and morphology of this rapidly renewing organ remains enigmatic. Here, we provide an overview of embryonic mouse gut development, with a focus on the intestinal vasculature and the enteric nervous system. We review how nutrition and the gut microbiota affect the adaptation of cellular and morphologic properties of the intestine, and how these processes are interconnected with innate immunity. Furthermore, we discuss how nutritional and microbial factors impact the renewal and differentiation of the epithelial lineage, influence the adaptation of capillary networks organized in villus structures, and shape the enteric nervous system and the intestinal smooth muscle layers. Intriguingly, the anatomy of the gut shows remarkable flexibility to nutritional and microbial challenges in the adult organism.

Crosstalk between Gut and Brain in Alzheimer's Disease: The Role of Gut Microbiota Modulation Strategies

The gut microbiota (GM) represents a diverse and dynamic population of microorganisms and about 100 trillion symbiotic microbial cells that dwell in the gastrointestinal tract. Studies suggest that the GM can influence the health of the host, and several factors can modify the GM composition, such as diet, drug intake, lifestyle, and geographical locations. Gut dysbiosis can affect brain immune homeostasis through the microbiota–gut–brain axis and can play a key role in the pathogenesis of neurodegenerative diseases, including dementia and Alzheimer’s disease (AD). The relationship between gut dysbiosis and AD is still elusive, but emerging evidence suggests that it can enhance the secretion of lipopolysaccharides and amyloids that may disturb intestinal permeability and the blood–brain barrier. In addition, it can promote the hallmarks of AD, such as oxidative stress, neuroinflammation, amyloid-beta formation, insulin resistance, and ultimately the causation of neural death. Poor dietary habits and aging, along with inflammatory responses due to dysbiosis, may contribute to the pathogenesis of AD. Thus, GM modulation through diet, probiotics, or fecal microbiota transplantation could represent potential therapeutics in AD. In this review, we discuss the role of GM dysbiosis in AD and potential therapeutic strategies to modulate GM in AD.

The metabolic impact of small intestinal nutrient sensing

The gastrointestinal tract maintains energy and glucose homeostasis, in part through nutrient-sensing and subsequent signaling to the brain and other tissues. In this review, we highlight the role of small intestinal nutrient-sensing in metabolic homeostasis, and link high-fat feeding, obesity, and diabetes with perturbations in these gut-brain signaling pathways. We identify how lipids, carbohydrates, and proteins, initiate gut peptide release from the enteroendocrine cells through small intestinal sensing pathways, and how these peptides regulate food intake, glucose tolerance, and hepatic glucose production. Lastly, we highlight how the gut microbiota impact small intestinal nutrient-sensing in normal physiology, and in disease, pharmacological and surgical settings. Emerging evidence indicates that the molecular mechanisms of small intestinal nutrient sensing in metabolic homeostasis have physiological and pathological impact as well as therapeutic potential in obesity and diabetes.

The gastrointestinal tract participates in maintaining metabolic homeostasis in part through nutrient-sensing and subsequent gut-brain signalling. Here the authors review the role of small intestinal nutrient-sensing in regulation of energy intake and systemic glucose metabolism, and link high-fat diet, obesity and diabetes with perturbations in these pathways.

Microbial Modulation of the Development and Physiology of the Enteric Nervous System

The gastrointestinal tract harbors an intrinsic neuronal network, the enteric nervous system (ENS). The ENS controls motility, fluid homeostasis, and blood flow, but also interacts with other components of the intestine such as epithelial and immune cells. Recent studies indicate that gut microbiota diversification, which occurs alongside postnatal ENS maturation, could be critical for the development and function of the ENS. Here we discuss the possibility that this functional relationship starts in utero, whereby the maternal microbiota would prime the developing ENS and shape its physiology. We review ENS/microbiota interactions and their modulation in physiological and pathophysiological contexts. While microbial modulation of the ENS physiology is now well established, further studies are required to understand the contribution of the gut microbiota to the development and pathology of the ENS and to reveal the precise mechanisms underlying microbiota-to-ENS communications.

Sensitivity to Dietary Wheat Gluten in Atlantic Salmon Indicated by Gene Expression Changes in Liver and Intestine

Feed safety is a necessity for animal health and welfare as well as prerequisite for food safety and human health. Wheat gluten (WG) is considered as a valuable protein source in fish feed due to its suitability as a feed binder, high digestibility, good amino acid profile, energy density and most importantly, due to its relatively low level of anti-nutritional factors (ANFs). The main aim of this study was to identify the impact of dietary WG on salmon health by analysing growth, feed efficiency and the hepatic and intestinal transcriptomes. The fish were fed either control diet with fishmeal (FM) as the only source of protein or diets, where 15% or 30% of the FM were replaced by WG. The fish had a mean initial weight of 223 g and approximately doubled their weight during the 9-week experiment. Salmon fed on 30% WG showed reduced feed intake compared to the 15% and FM fed groups. The liver was the less affected organ but fat content and activities of the liver health markers in plasma increased with the inclusion level of WG in the diet. Gene expression analysis showed significant changes in both, intestine and liver of fish fed with 30% WG. Especially noticeable were changes in the lipid metabolism, in particular in relation to the intestinal lipoprotein transport and sterol metabolism. Moreover, the intestinal transcriptome of WG-fed fish showed shifts in the expression of a large number of genes responsible for immunity and tissue structure and integrity. These observations implied that the fish receiving WG-containing diet were undergoing nutritional stress. Overall, the study provided evidence that a high dietary level of WG can have a negative impact on the intestinal and liver health of salmon with symptoms similar to gluten sensitivity in humans.

Duodenal mucosal secretory disturbances in functional dyspepsia

BACKGROUND

There is increased recognition of duodenal disturbances (inflammation, altered mucosal protein expression, and chemosensitivity) in functional dyspepsia (FD). Besides sensorimotor functions, enteric submucosal neurons also regulate epithelial ion transport. We hypothesized that duodenal mucosal ion transport and expression of associated genes are altered in FD.

METHODS

Duodenal mucosal ion transport (basal and acetylcholine- and glucose-evoked changes in short-circuit current [Isc]) and expression of associated genes and regulatory miRNAs were evaluated in 40 FD patients and 24 healthy controls.

RESULTS

Basal Isc (FD: 88.2 [52.6] μA/cm² vs healthy: 20.3 [50.2] μA/cm² ; P ≤ .0001), acetylcholine-evoked Isc (FD: Emax 50.4 [35.8] μA/cm² vs healthy: 16.6 [15] μA/cm² ; P ≤ .001), and glucose-evoked Isc responses (FD: E_max 69.8 [42.1] μA/cm² vs healthy: 40.3 [24.6] μA/cm² ; P = .02) were greater in FD than in controls. The Emax for glucose was greater in FD patients on selective serotonin reuptake inhibitors. In FD, the mRNA expression of SLC4A7 and SLC4A4, which transport bicarbonate into cells at the basolateral surface, and the apical anion exchanger SLC26A3 were reduced (false discovery rate <0.05), the serotonin receptor HTR4 was increased, and the serotonin transporter SLC6A4 was decreased. Selected miRNAs (hsa-miR-590-3p, hsa-miR-32-5p) that target genes associated with ionic transport were upregulated in FD.

CONCLUSIONS

Compared to controls, FD patients had greater baseline and agonist-evoked duodenal mucosal secretory responses. These findings may be explained by reduced gene expression, which would be anticipated to reduce luminal bicarbonate secretion. The upregulated miRNAs may partly explain the downregulation of these genes in FD.

Intestinal Bacteria Maintain Adult Enteric Nervous System and Nitrergic Neurons via Toll-like Receptor 2-induced Neurogenesis in Mice

BACKGROUND & AIMS

The enteric nervous system (ENS) exists in close proximity to luminal bacteria. Intestinal microbes regulate ENS development, but little is known about their effects on adult enteric neurons. We investigated whether intestinal bacteria or their products affect the adult ENS via toll-like receptors (TLRs) in mice.

METHODS

We performed studies with conventional C57/BL6, germ-free C57/BL6, Nestin-creER^T2:tdTomato, Nestin-GFP, and ChAT-cre:tdTomato. Mice were given drinking water with ampicillin or without (controls). Germ-free mice were given drinking water with TLR2 agonist or without (controls). Some mice were given a blocking antibody against TLR2 or a TLR4 inhibitor. We performed whole gut transit, bead latency, and geometric center studies. Feces were collected and analyzed by 16S ribosomal RNA gene sequencing. Longitudinal muscle myenteric plexus (LMMP) tissues were collected, analyzed by immunohistochemistry, and levels of nitric oxide were measured. Cells were isolated from colonic LMMP of Nestin-creER^T2:tdTomato mice and incubated with agonists of TLR2 (receptor for gram-positive bacteria), TLR4 (receptor for gram-negative bacteria), or distilled water (control) and analyzed by flow cytometry.

RESULTS

Stool from mice given ampicillin had altered composition of gut microbiota with reduced abundance of gram-positive bacteria and increased abundance of gram-negative bacteria, compared with mice given only water. Mice given ampicillin had reduced colon motility compared with mice given only water, and their colonic LMMP had reduced numbers of nitrergic neurons, reduced neuronal nitric oxide synthase production, and reduced colonic neurogenesis. Numbers of colonic myenteric neurons increased after mice were switched from ampicillin to plain water, with increased markers of neurogenesis. Nestin-positive enteric neural precursor cells expressed TLR2 and TLR4. In cells isolated from the colonic LMMP, incubation with the TLR2 agonist increased the percentage of neurons originating from enteric neural precursor cells to approximately 10%, compared with approximately 0.01% in cells incubated with the TLR4 agonist or distilled water. Mice given an antibody against TLR2 had prolonged whole gut transit times; their colonic LMMP had reduced total neurons and a smaller proportion of nitrergic neurons per ganglion, and reduced markers of neurogenesis compared with mice given saline. Colonic LMMP of mice given the TLR4 inhibitor did not have reduced markers of neurogenesis. Colonic LMMP of germ-free mice given TLR2 agonist had increased neuronal numbers compared with control germ-free mice.

CONCLUSIONS

In the adult mouse colon, TLR2 promotes colonic neurogenesis, regulated by intestinal bacteria. Our findings indicate that colonic microbiota help maintain the adult ENS via a specific signaling pathway. Pharmacologic and probiotic approaches directed towards specific TLR2 signaling processes might be developed for treatment of colonic motility disorders related to use of antibiotics or other factors.

Robust, 3-Dimensional Visualization of Human Colon Enteric Nervous System Without Tissue Sectioning

BACKGROUND & AIMS

Small, 2-dimensional sections routinely used for human pathology analysis provide limited information about bowel innervation. We developed a technique to image human enteric nervous system (ENS) and other intramural cells in 3 dimensions.

METHODS

Using mouse and human colon tissues, we developed a method that combines tissue clearing, immunohistochemistry, confocal microscopy, and quantitative analysis of full-thickness bowel without sectioning to quantify ENS and other intramural cells in 3 dimensions.

RESULTS

We provided 280 adult human colon confocal Z-stacks from persons without known bowel motility disorders. Most of our images were of myenteric ganglia, captured using a 20× objective lens. Full-thickness colon images, viewed with a 10× objective lens, were as large as 4 × 5 mm². Colon from 2 pediatric patients with Hirschsprung disease was used to show distal colon without enteric ganglia, as well as a transition zone and proximal pull-through resection margin where ENS was present. After testing a panel of antibodies with our method, we identified 16 antibodies that bind to molecules in neurons, glia, interstitial cells of Cajal, and muscularis macrophages. Quantitative analyses demonstrated myenteric plexus in 24.5% ± 2.4% of flattened colon Z-stack area. Myenteric ganglia occupied 34% ± 4% of myenteric plexus. Single myenteric ganglion volume averaged 3,527,678 ± 573,832 mm³ with 38,706 ± 5763 neuron/mm³ and 129,321 ± 25,356 glia/mm³. Images of large areas provided insight into why published values of ENS density vary up to 150-fold-ENS density varies greatly, across millimeters, so analyses of small numbers of thin sections from the same bowel region can produce varying results. Neuron subtype analysis revealed that approximately 56% of myenteric neurons stained with neuronal nitric oxide synthase antibody and approximately 33% of neurons produce and store acetylcholine. Transition zone regions from colon tissues of patients with Hirschsprung disease had ganglia in multiple layers and thick nerve fiber bundles without neurons. Submucosal neuron distribution varied among imaged colon regions.

CONCLUSIONS

We developed a 3-dimensional imaging method for colon that provides more information about ENS structure than tissue sectioning. This approach could improve diagnosis for human bowel motility disorders and may be useful for other bowel diseases as well.

Food, microbes, sex and old age: on the plasticity of gastrointestinal innervation

The gastrointestinal tract is innervated by its own enteric nervous system and by extrinsic neurons that connect it with the central nervous system. Innervation allows the gastrointestinal tract to sense and respond to diverse stimuli, adjusting motility and secretion, but also affecting our physiology, behaviour and immunity. The mechanisms underlying the formation of gastrointestinal neurons are beginning to be elucidated; those that keep them plastic over an organism's lifetime remain to be explored. Here, we review the effects of microbiota, nutrients, sex and ageing on the morphology and function of gastrointestinal innervation in mammals, and discuss how this plasticity shapes gut-brain crosstalk and whole-body physiology. We also highlight insights gained by nascent studies of the enteric innervation of Drosophila melanogaster.

Pluripotent stem cell derived intestinal organoids with an enteric nervous system

The use of human pluripotent stem cells (hPSCs) and differentiation techniques offer new ways to generate specific tissue. It is now possible to differentiate hPSC into human intestinal organoids that include an enteric nervous system. Using step-wise differentiation processes, we generate innervated intestinal organoids that form three-dimensional structures bearing an epithelium, neurons and glial cells embedded in a supporting mesenchyme. Innervated organoids further develop to a complex structure with similar organization and cellular differentiation as the developing intestine. These tools open up new fields of application in the study of the development and pathophysiology of enteric neuropathies. Herein, we describe the generation of both human intestinal organoids and vagal neural crest cells from hPSC and their combination into an innervated organoid. We also discuss technical considerations for these experiments, and highlight advantages and limitations of the system.

Dietary Proteins Regulate Serotonin Biosynthesis and Catabolism by Specific Gut Microbes

More than 90% of serotonin is produced in the intestine. Previous studies have shown that different protein diets significantly affect serum serotonin levels. Here, the colonic microbiota and intestinal serotonin were measured to elaborate how protein diets affect serotonin production in a mouse model. The emulsion-type sausage protein and cooked pork protein diets increased the mRNA levels of tryptophan hydroxylase 1 (Tph1) and monoamine oxidase A (Maoa) and serotonin level as well but reduced the number of enterochromaffin cells. However, the soy protein diet increased the number of enterochromaffin cells and Tph1 mRNA level but decreased the Maoa mRNA level and the serotonin content. Specific gut microbes that responded to dietary changes and affected the content of short-chain fatty acids were significantly related to serotonin-associated biomarkers. These results suggest that dietary proteins may regulate serotonin biosynthesis and catabolism by altering specific gut microbes.

Dietary inclusion of plant ingredients induces epigenetic changes in the intestine of zebrafish

Epigenetic modifications, such as DNA methylation, can be regulated by nutrition and dietary factors. There has been a large increase in the use of sustainable plant-based protein sources in fish feed due to limitations of fishmeal resources, which are needed to sustain a rapidly growing aquaculture industry. With this major transition from marine ingredients to plant-based diets, fish are abruptly introduced to changes in dietary composition and exposed to a variety of phytochemicals, some of which known to cause epigenetic changes in mammals. However, the effect of plant ingredients on the epigenome of fish is barely understood. In the present study, the nutriepigenomic effects of the addition of pea, soy, and wheat gluten protein concentrate to aquafeeds were investigated using zebrafish as a model. A genome-wide analysis of DNA methylation patterns was performed by reduced representation bisulphite sequencing to examine global epigenetic alterations in the mid intestine after a 42-day feeding trial. We found that inclusion of 30% of wheat gluten, pea and soy protein concentrate in the diet induced epigenetic changes in the mid intestine of zebrafish. A large number of genes and intergenic regions were differentially methylated with plant-based diets. The genes concerned were related to immunity, NF-κB system, ubiquitin-proteasome pathway, MAPK pathway, and the antioxidant defence system. Epigenetic regulation of several biological processes, including neurogenesis, cell adhesion, response to stress and immunity was also observed. Ultimately, the observed epigenetic changes may enable zebrafish to rapidly regulate inflammation and maintain intestinal homoeostasis when fed plant protein-based diets.

Gut–Brain Axis: Focus on Neurodegeneration and Mast Cells

Many studies highlighted that a bidirectional communication between the gut and the central nervous system (CNS) exists. A vigorous immune response to antigens must be avoided, and pathogenic organisms crossing the gut barrier must be detected and killed. For this reason, the immune system developed fine mechanisms able to maintain this delicate balance. The microbiota is beneficial to its host, providing protection against pathogenic bacteria. It is intimately involved in numerous aspects of host physiology, from nutritional status to behavior and stress response. In the last few years, the implication of the gut microbiota and its bioactive microbiota-derived molecules in the progression of multiple diseases, as well as in the development of neurodegenerative disorders, gained increasing attention. The purpose of this review is to provide an overview of the gut microbiota with particular attention toward neurological disorders and mast cells. Relevant roles are played by the mast cells in neuroimmune communication, such as sensors and effectors of cytokines and neurotransmitters. In this context, the intake of beneficial bacterial strains as probiotics could represent a valuable therapeutic approach to adopt in combination with classical therapies. Further studies need to be performed to understand if the gut bacteria are responsible for neurological disorders or if neurological disorders influence the bacterial profile.

Colonic neuronal loss and delayed motility induced by high-fat diet occur independently of changes in the major groups of microbiota in Swiss mice

BACKGROUND

Obesity has been linked to gastrointestinal disorders, and the loss of myenteric neurons in the intestine caused by high-fat diets (HFD) has been attributed to changes in microbiota and lipotoxicity. We investigated whether the prebiotic inulin modulates bacterial populations and alleviates neuronal loss in mice fed HFD.

METHODS

Swiss mice were fed purified rodent diet or HFD (59% kcal fat), or both diets supplemented with inulin for 17 weeks. Intestinal motility was assessed and a metagenome analysis of the colonic microbiota was performed. The gene expression of inflammatory markers was evaluated, and immunofluorescence was performed for different types of myenteric neurons and glial cells in the distal colon.

KEY RESULTS

The HFD caused obesity and delayed colonic motility. The loss of myenteric neurons and glial cells in obese mice affected all of the studied neuronal populations, including neurons positive for myosin-V, neuronal nitric oxide synthase, vasoactive intestinal peptide, and calretinin. Although obese mice supplemented with inulin exhibited improvements in colonic motility, neuronal, and glial cell loss persisted. The HFD did not altered the expression levels of inflammatory cytokines in the intestine or the prevalence of the major groups in microbiota, but inulin increased the proportion of the genus Akkermansia in the obese mice.

CONCLUSIONS AND INFERENCES

In Swiss mice, the HFD-induced neuronal loss but did not change the major groups in microbiota. This suggests that, despite the increase in the beneficial bacteria, other factors that are directly linked to excess dietary lipid intake affect the enteric nervous system.

To learn, to remember, to forget-How smart is the gut?

The enteric nervous system (ENS) resides within the gut wall and autonomously controls gut functions through coordinated activation of sensory, inter and motor neurons. Its activity is modulated by the enteric immune and endocrine system as well as by afferent and efferent nerves of the parasympathetic and sympathetic nervous system. The ENS is often referred to as the second brain and hence is able to perform sophisticated tasks. We review the evidence that the "smartness" of the ENS may even extend to its ability to learn and to memorize. Examples for habituation, sensitization, conditioned behaviour and long-term facilitation are evidence for various forms of implicit learning. Moreover, we discuss how this may change not only basic Neurogastroenterology but also our understanding of development of gut diseases and chronic disorders in gut functions. At the same time, we identify open questions and future challenges to confirm learning, memory and memory deficits in the gut. Despite some remaining experimental challenges, we are convinced that the gut is able to learn and are tempted to answer the question with: Yes, the gut is smart.

Gut microbes and metabolites as modulators of blood-brain barrier integrity and brain health

The human gastrointestinal (gut) microbiota comprises diverse and dynamic populations of bacteria, archaea, viruses, fungi, and protozoa, coexisting in a mutualistic relationship with the host. When intestinal homeostasis is perturbed, the function of the gastrointestinal tract and other organ systems, including the brain, can be compromised. The gut microbiota is proposed to contribute to blood-brain barrier disruption and the pathogenesis of neurodegenerative diseases. While progress is being made, a better understanding of interactions between gut microbes and host cells, and the impact these have on signaling from gut to brain is now required. In this review, we summarise current evidence of the impact gut microbes and their metabolites have on blood-brain barrier integrity and brain function, and the communication networks between the gastrointestinal tract and brain, which they may modulate. We also discuss the potential of microbiota modulation strategies as therapeutic tools for promoting and restoring brain health.

The multiple faces of inflammatory enteric glial cells: is Crohn's disease a gliopathy?

Gone are the days when enteric glial cells (EGC) were considered merely satellites of enteric neurons. Like their brain counterpart astrocytes, EGC express an impressive number of receptors for neurotransmitters and intercellular messengers, thereby contributing to neuroprotection and to the regulation of neuronal activity. EGC also produce different soluble factors that regulate neighboring cells, among which are intestinal epithelial cells. A better understanding of EGC response to an inflammatory environment, often referred to as enteric glial reactivity, could help define the physiological role of EGC and the importance of this reactivity in maintaining gut functions. In chronic inflammatory disorders of the gut such as Crohn's disease (CD) and ulcerative colitis, EGC exhibit abnormal phenotypes, and their neighboring cells are dysfunctional; however, it remains unclear whether EGC are only passive bystanders or active players in the pathophysiology of both disorders. The aim of the present study is to review the physiological roles and properties of EGC, their response to inflammation, and their role in the regulation of the intestinal epithelial barrier and to discuss the emerging concept of CD as an enteric gliopathy.

Serotonin in the gut: Blessing or a curse

Serotonin (5-hydroxytryptamine or 5-HT) once most extensively studied as a neurotransmitter of the central nervous system, is seen to be predominantly secreted in the gut. About 95% of 5-HT is estimated to be found in gut mainly within the enterochromaffin cells whereas about 5% is found in the brain. 5-HT is an important enteric signaling molecule and is well known for playing a key role in sensory-motor and secretory functions in the gut. In recent times, studies uncovering various new functions of gut-derived 5-HT indicate that many more are yet to be discovered in coming days. Recent studies revealed that 5-HT plays a pivotal role in immune cell activation and generation/perpetuation of inflammation in the gut. In addition to its various roles in the gut, there are now emerging evidences that suggest an important role of gut-derived 5-HT in other biological processes beyond the gut, such as bone remodeling and metabolic homeostasis. This review focuses to briefly summarize the accumulated and newly updated role of 5-HT in the maintenance of normal gut physiology and in the pathogenesis of inflammation in the gut. The collected information about this multifaceted signaling molecule may aid in distinguishing its good and bad effects which may lead to the development of novel strategies to overcome the unwanted effect, such as in inflammatory bowel disease.

Undernutrition in childhood resulted in bad dietary behaviors and the increased risk of hypertension in a middle-aged Chinese population

This study was designed to explore the association between undernutrition in the growth period and cardiovascular risk factors in a middle-aged Chinese population. A total of 1756 subjects, aged 45-60 years, were invited to participate in the Hefei Nutrition and Health Study and divided into three groups according to their self-reported animal food intake in the growth period. Group 1, Group 2 and Group 3 were defined as undernutrition, nutritional improvement and the good nutrition group, respectively. In the three groups, the subjects in Groups 1 and 2 had more oil and salt intake (P<0.001), and less eggs and milk intake (P<0.001), when compared with the subjects in Group 3. After adjusting for age, education, smoking status and other confounding factors, it was found that male participants who experienced nutritional improvement before age 18 had higher risk of hypertension [odds ratio (OR)=1.68; 95% confidence intervals (CI): 1.05, 2.69] than those with good nutrition, and female participants with undernutrition (OR=1.52; 95% CI: 1.01, 2.29) and nutritional improvement (OR=1.68; 95% CI: 1.04, 2.69) before age 18 had a higher risk of hypertension than those with good nutrition. For diabetes, obesity, hypercholesterolemia and hypertriglyceridemia, our results did not found difference among the three groups both in male and female. Our findings indicated that nutritional deficiency in childhood was associated with bad dietary behaviors and a significantly increased risk of hypertension in middle age. Therefore, early adequate nutrition is very important for the prevention of non-communicable diseases later.

Acceleration of small bowel motility after oral administration of dai-kenchu-to (TJ-100) assessed by cine magnetic resonance imaging

Dai-kenchu-to (TJ-100) is an herbal medicine used to shorten the duration of intestinal transit by accelerating intestinal movement. However, intestinal movement in itself has not been evaluated in healthy volunteers using radiography, fluoroscopy, and radioisotopes because of exposure to ionizing radiation. The purpose of this study was to evaluate the effect of TJ-100 on intestinal motility using cinematic magnetic resonance imaging (cine MRI) with a steady-state free precession sequence. Ten healthy male volunteers received 5 g of either TJ-100 or lactose without disclosure of the identity of the substance. Each volunteer underwent two MRI examinations after taking the substances (TJ-100 and lactose) on separate days. They drank 1200 mL of tap water and underwent cine MRI after 10 min. A steady-state free precession sequence was used for imaging, which was performed thrice at 0, 10, 20, 30, 40, and 50 min. The bowel contraction frequency and distention score were assessed. Wilcoxon signed-rank test was used, and differences were considered significant at a P-value <0.05. The bowel contraction frequency tended to be greater in the TJ-100 group and was significantly different in the ileum at 20 (TJ-100, 8.95 ± 2.88; lactose, 4.80 ± 2.92; P < 0.05) and 50 min (TJ-100, 9.45 ± 4.49; lactose, 4.45 ± 2.65; P < 0.05) between the groups. No significant differences were observed in the bowel distention scores. Cine MRI demonstrated that TJ-100 activated intestinal motility without dependence on ileum distention.

Impact of Intestinal Peptides on the Enteric Nervous System: Novel Approaches to Control Glucose Metabolism and Food Intake

The gut is one of the most important sources of bioactive peptides in the body. In addition to their direct actions in the brain and/or peripheral tissues, the intestinal peptides can also have an impact on enteric nervous neurons. By modifying the endogenousproduction of these peptides, one may expect modify the "local" physiology such as glucose absorption, but also could have a "global" action via the gut-brain axis. Due to the various origins of gut peptides (i.e., nutrients, intestinal wall, gut microbiota) and the heterogeneity of enteric neurons population, the potential physiological parameters control by the interaction between the two partners are multiple. In this review, we will exclusively focus on the role of enteric nervous system as a potential target of gut peptides to control glucose metabolism and food intake. Potential therapeutic strategies based on per os administration of gut peptides to treat type 2 diabetes will be described.

Importance of the enteric nervous system in the control of the migrating motility complex

The migrating motility complex (MMC), a cyclical phenomenon, represents rudimentary motility pattern in the gastrointestinal tract. The MMC is observed mostly in the stomach and gut of man and numerous animal species. It contains three or four phases, while its phase III is the most characteristic. The mechanisms controlling the pattern are unclear in part, although the neural control of the MMC seems crucial. The main goal of this article was to discuss the importance of intrinsic innervation of the gastrointestinal tract in MMC initiation, migration, and cessation to emphasize that various MMC-controlling mechanisms act through the enteric nervous system. Two main neural regions, central and peripheral, are able to initiate the MMC. However, central regulation of the MMC may require cooperation with the enteric nervous system. When central mechanisms are not active, the MMC can be initiated peripherally in any region of the small bowel. The enteric nervous system affects the MMC in response to the luminal stimuli which can contribute to the initiation and cessation of the cycle, and it may evoke irregular phasic contractions within the pattern. The hormonal regulators released from the endocrine cells may exert a modulatory effect upon the MMC mostly through the enteric nervous system. Their central action could also be considered. It can be concluded that the enteric nervous system is involved in the great majority of the MMC-controlling mechanisms.

Gut Microbial Influences on the Mammalian Intestinal Stem Cell Niche

The mammalian intestinal epithelial stem cell (IESC) niche is comprised of diverse epithelial, immune, and stromal cells, which together respond to environmental changes within the lumen and exert coordinated regulation of IESC behavior. There is growing appreciation for the role of the gut microbiota in modulating intestinal proliferation and differentiation, as well as other aspects of intestinal physiology. In this review, we evaluate the diverse roles of known niche cells in responding to gut microbiota and supporting IESCs. Furthermore, we discuss the potential mechanisms by which microbiota may exert their influence on niche cells and possibly on IESCs directly. Finally, we present an overview of the benefits and limitations of available tools to study niche-microbe interactions and provide our recommendations regarding their use and standardization. The study of host-microbe interactions in the gut is a rapidly growing field, and the IESC niche is at the forefront of host-microbe activity to control nutrient absorption, endocrine signaling, energy homeostasis, immune response, and systemic health.

Non-conventional features of peripheral serotonin signalling - the gut and beyond

Serotonin was first discovered in the gut, and its conventional actions as an intercellular signalling molecule in the intrinsic and extrinsic enteric reflexes are well recognized, as are a number of serotonin signalling pharmacotherapeutic targets for treatment of nausea, diarrhoea or constipation. The latest discoveries have greatly broadened our understanding of non-conventional actions of peripheral serotonin within the gastrointestinal tract and in a number of other tissues. For example, it is now clear that bacteria within the lumen of the bowel influence serotonin synthesis and release by enterochromaffin cells. Also, serotonin can act both as a pro-inflammatory and anti-inflammatory signalling molecule in the intestinal mucosa via activation of serotonin receptors (5-HT₇ or 5-HT₄ receptors, respectively). For decades, serotonin receptors have been known to exist in a variety of tissues other than the gut, but studies have now provided strong evidence for physiological roles of serotonin in several important processes, including haematopoiesis, metabolic homeostasis and bone metabolism. Furthermore, evidence for serotonin synthesis in peripheral tissues outside of the gut is emerging. In this Review, we expand the discussion beyond gastrointestinal functions to highlight the roles of peripheral serotonin in colitis, haematopoiesis, energy and bone metabolism, and how serotonin is influenced by the gut microbiota.

Excitability and Synaptic Transmission in the Enteric Nervous System: Does Diet Play a Role?

Changes in diet are a challenge to the gastrointestinal tract which needs to alter its processing mechanisms to continue to process nutrients and maintain health. In particular, the enteric nervous system (ENS) needs to adapt its motor and secretory programs to deal with changes in nutrient type and load in order to optimise nutrient absorption.The nerve circuits in the gut are complex, and the numbers and types of neurons make recordings of specific cell types difficult, time-consuming, and prone to sampling errors. Nonetheless, traditional research methods like intracellular electrophysiological approaches have provided the basis for our understanding of the ENS circuitry. In particular, animal models of intestinal inflammation have shown us that we can document changes to neuronal excitability and synaptic transmission.Recent studies examining diet-induced changes to ENS programming have opted to use fast imaging techniques to reveal changes in neuron function. Advances in imaging techniques using voltage- or calcium-sensitive dyes to record neuronal activity promise to overcome many limitations inherent to electrophysiological approaches. Imaging techniques allow access to a wide range of ENS phenotypes and to the changes they undergo during dietary challenges. These sorts of studies have shown that dietary variation or obesity can change how the ENS processes information-in effect reprogramming the ENS. In this review, the data gathered from intracellular recordings will be compared with measurements made using imaging techniques in an effort to determine if the lessons learnt from inflammatory changes are relevant to the understanding of diet-induced reprogramming.

Diverse Effects of Gut-Derived Serotonin in Intestinal Inflammation

The gut is the largest producer of serotonin or 5-hydroxytryptamine (5-HT) in the human body, and 5-HT has been recognized as an important signaling molecule in the gut for decades. There are two distinct sources of enteric 5-HT. Mucosal 5-HT is predominantly produced by enterochromaffin (EC) cells of the gastrointestinal (GI) tract, and neuronal 5-HT in the gut is produced by serotonergic neurons of the enteric nervous system (ENS). The quantity of mucosal 5-HT produced vastly eclipses the amount of neuronal 5-HT in the gut. Though it is difficult to separate the functions of neuronal and mucosal 5-HT, in the normal gut both types of enteric 5-HT work synergistically playing a prominent role in the maintenance of GI functions. In inflammatory conditions of the gut, like inflammatory bowel disease (IBD) recent studies have revealed new diverse functions of enteric 5-HT. Mucosal 5-HT plays an important role in the production of pro-inflammatory mediators from immune cells, and neuronal 5-HT provides neuroprotection in the ENS. Based on searches for terms such as "5-HT", "EC cell", "ENS", and "inflammation" in pubmed.gov as well as by utilizing pertinent reviews, the current review aims to provide an update on the role of enteric 5-HT and its immune mediators in the context of intestinal inflammation.

Short communication: Tryptic β-casein hydrolysate modulates enteric nervous system development in primary culture

The intestinal tract of the newborn is particularly sensitive to gastrointestinal disorders, such as infantile diarrhea or necrotizing colitis. Perinatal development of the gut also encompasses the maturation of the enteric nervous system (ENS), a main regulator of intestinal motility and barrier functions. It was recently shown that ENS maturation can be enhanced by nutritional factors to improve intestinal maturation. Bioactivity of milk proteins is often latent, requiring the release of bioactive peptides from inactive native proteins. Several casein-derived hydrolysates presenting immunomodulatory properties have been described recently. Furthermore, accumulating data indicate that milk-derived hydrolysate can enhance gut maturation and enrichment of milk formula with such hydrolysates has recently been proposed. However, the capability of milk-derived bioactive hydrolysate to target ENS maturation has not been analyzed so far. We, therefore, investigated the potential of a recently described tryptic β-casein hydrolysate to modulate ENS growth parameters in an in vitro model of rat primary culture of ENS. Rat primary cultures of ENS were incubated with a bioactive tryptic β-casein hydrolysate and compared with untreated controls or to cultures treated with native β-casein or a Prolyve β-casein hydrolysate (Lyven, Colombelles, France). Differentiation of enteric neurons and enteric glial cells, and establishment of enteric neural network were analyzed using immunohistochemistry and quantitative PCR. Effect of tryptic β-casein hydrolysate on bone morphogenetic proteins (BMP)/Smad pathway, an essential regulator of ENS development, was further assessed using quantitative PCR and immunochemistry. Tryptic β-casein hydrolysate stimulated neurite outgrowth and simultaneously modulated the formation of enteric ganglia-like structures, whereas native β-casein or Prolyve β-casein hydrolysate did not. Additionally, treatment with tryptic bioactive β-casein hydrolysate increased the expression of the glial marker glial fibrillary acidic protein and induced profound modifications of enteric glial cells morphology. Finally, expression of BMP2 and BMP4 and activation of Smad1/5 was altered after treatment with tryptic bioactive β-casein hydrolysate. Our data suggests that this milk-derived bioactive hydrolysate modulates ENS maturation through the regulation of BMP/Smad-signaling pathway. This study supports the need for further investigation on the influence of milk-derived bioactive peptides on ENS and intestinal maturation in vivo.

Can We Selectively Reduce Appetite for Energy-Dense Foods? An Overview of Pharmacological Strategies for Modification of Food Preference Behavior

Excessive intake of food, especially palatable and energy-dense carbohydrates and fats, is largely responsible for the growing incidence of obesity worldwide. Although there are a number of candidate antiobesity drugs, only a few of them have been proven able to inhibit appetite for palatable foods without the concurrent reduction in regular food consumption. In this review, we discuss the interrelationships between homeostatic and hedonic food intake control mechanisms in promoting overeating with palatable foods and assess the potential usefulness of systemically administered pharmaceuticals that impinge on the endogenous cannabinoid, opioid, aminergic, cholinergic, and peptidergic systems in the modification of food preference behavior. Also, certain dietary supplements with the potency to reduce specifically palatable food intake are presented. Based on human and animal studies, we indicate the most promising therapies and agents that influence the effectiveness of appetite-modifying drugs. It should be stressed, however, that most of the data included in our review come from preclinical studies; therefore, further investigations aimed at confirming the effectiveness and safety of the aforementioned medications in the treatment of obese humans are necessary.

The Neuro-endocrinological Role of Microbial Glutamate and GABA Signaling

Gut microbiota provides the host with multiple functions (e.g., by contributing to food digestion, vitamin supplementation, and defense against pathogenic strains) and interacts with the host organism through both direct contact (e.g., through surface antigens) and soluble molecules, which are produced by the microbial metabolism. The existence of the so-called gut–brain axis of bi-directional communication between the gastrointestinal tract and the central nervous system (CNS) also supports a communication pathway between the gut microbiota and neural circuits of the host, including the CNS. An increasing body of evidence has shown that gut microbiota is able to modulate gut and brain functions, including the mood, cognitive functions, and behavior of humans. Nonetheless, given the extreme complexity of this communication network, its comprehension is still at its early stage. The present contribution will attempt to provide a state-of-the art description of the mechanisms by which gut microbiota can affect the gut–brain axis and the multiple cellular and molecular communication circuits (i.e., neural, immune, and humoral). In this context, special attention will be paid to the microbial strains that produce bioactive compounds and display ascertained or potential probiotic activity. Several neuroactive molecules (e.g., catecholamines, histamine, serotonin, and trace amines) will be considered, with special focus on Glu and GABA circuits, receptors, and signaling. From the basic science viewpoint, “microbial endocrinology” deals with those theories in which neurochemicals, produced by both multicellular organisms and prokaryotes (e.g., serotonin, GABA, glutamate), are considered as a common shared language that enables interkingdom communication. With regards to its application, research in this area opens the way toward the possibility of the future use of neuroactive molecule-producing probiotics as therapeutic agents for the treatment of neurogastroenteric and/or psychiatric disorders.

Gene-environment interactions and the enteric nervous system: Neural plasticity and Hirschsprung disease prevention

Intestinal function is primarily controlled by an intrinsic nervous system of the bowel called the enteric nervous system (ENS). The cells of the ENS are neural crest derivatives that migrate into and through the bowel during early stages of organogenesis before differentiating into a wide variety of neurons and glia. Although genetic factors critically underlie ENS development, it is now clear that many non-genetic factors may influence the number of enteric neurons, types of enteric neurons, and ratio of neurons to glia. These non-genetic influences include dietary nutrients and medicines that may impact ENS structure and function before or after birth. This review summarizes current data about gene-environment interactions that affect ENS development and suggests that these factors may contribute to human intestinal motility disorders like Hirschsprung disease or irritable bowel syndrome.

Malnutrition increases NO production and induces changes in inflammatory and oxidative status in the distal colon of lactating rats

BACKGROUND

Epidemiological studies have indicated the lack of breast feeding as a risk factor associated with later development of inflammatory bowel disease. Nevertheless, the repercussion of little feeding during suckling on large intestine inflammatory response and anti-oxidant resources has not yet been completely understood. This study hypothesized that unfavorable lactation is able to induce oxidative stress and release of inflammatory mediators modifying the integrity of the colon epithelium in weanling rats.

METHODS

Wistar rats were reared under different early nutritional conditions according to litter size in two groups: N6 (6 pups/dam) and N15 (15 pups/dam) until the 25th postnatal day. The distal colon was removed and processed for biochemical, morphometric, and immunohistochemical analyzes. Lipoperoxidation, nitric oxide (NO), reduced (GSH) and oxidized (GSSG) glutathione, tumor necrosis factor-alpha (TNF-α), interleukins-1β, 4 and 10 (IL-1β; IL-4; IL-10) levels, and total superoxide dismutase (tSOD), and catalase (CAT) activities were assessed. Morphometric analysis was carried out using paraffin sections and wholemount myenteric plexus preparations.

KEY RESULTS

Increased lipoperoxidation, NO, TNF-α and IL-1b levels, reduced tSOD and increased CAT activities were found in the N15 compared to N6 group. No intergroup difference was detected for IL-10, while lower levels of IL-4, GSH and GSSG and lower neuronal size and density were induced by undernutrition.

CONCLUSIONS & INFERENCES

Reduced feeding during suckling changed the inflammatory response and oxidative status in the colon of weanling rats. These data suggest potential mechanisms by which malnutrition early in life may increase the vulnerability of the large intestine to insults.

Stem Cells in the Intestine: Possible Roles in Pathogenesis of Irritable Bowel Syndrome

Irritable bowel syndrome is one of the most common functional gastrointestinal (GI) disorders that significantly impair quality of life in patients. Current available treatments are still not effective and the pathophysiology of this condition remains unclearly defined. Recently, research on intestinal stem cells has greatly advanced our understanding of various GI disorders. Alterations in conserved stem cell regulatory pathways such as Notch, Wnt, and bone morphogenic protein/TGF-β have been well documented in diseases such as inflammatory bowel diseases and cancer. Interaction between intestinal stem cells and various signals from their environment is important for the control of stem cell self-renewal, regulation of number and function of specific intestinal cell types, and maintenance of the mucosal barrier. Besides their roles in stem cell regulation, these signals are also known to have potent effects on immune cells, enteric nervous system and secretory cells in the gut, and may be responsible for various aspects of pathogenesis of functional GI disorders, including visceral hypersensitivity, altered gut motility and low grade gut inflammation. In this article, we briefly summarize the components of these signaling pathways, how they can be modified by extrinsic factors and novel treatments, and provide evidenced support of their roles in the inflammation processes. Furthermore, we propose how changes in these signals may contribute to the symptom development and pathogenesis of irritable bowel syndrome.