Peptidergic regulation of gastrointestinal motility in rodents

Enteric VIP-producing neurons maintain gut microbiota homeostasis through regulating epithelium fucosylation

Interactions between the enteric nervous system (ENS) and intestinal epithelium are thought to play a vital role in intestinal homeostasis. How the ENS monitors the frontier with commensal and pathogenic microbes while maintaining epithelial function remains unclear. Here, by combining subdiaphragmatic vagotomy with transcriptomics, chemogenetic strategy, and coculture of enteric neuron-intestinal organoid, we show that enteric neurons expressing VIP shape the α1,2-fucosylation of intestinal epithelial cells (IECs). Mechanistically, neuropeptide VIP activates fut2 expression via the Erk1/2-c-Fos pathway through the VIPR1 receptor on IECs. We further demonstrate that perturbation of enteric neurons leads to gut dysbiosis through α1,2-fucosylation in the steady state and results in increased susceptibility to alcohol-associated liver disease (ALD). This was attributed to an imbalance between beneficial Bifidobacterium and opportunistic pathogenic Enterococcus faecalis in ALD. In addition, Bifidobacterium α1,2-fucosidase may promote Bifidobacterium adhesion to the mucosal surface, which restricts Enterococcus faecalis overgrowth and prevents ALD progression.

PET Imaging of the Neuropeptide Y System: A Systematic Review

Neuropeptide Y (NPY) is a vastly studied biological peptide with numerous physiological functions that activate the NPY receptor family (Y₁, Y₂, Y₄ and Y₅). Moreover, these receptors are correlated with the pathophysiology of several diseases such as feeding disorders, anxiety, metabolic diseases, neurodegenerative diseases, some types of cancers and others. In order to deepen the knowledge of NPY receptors' functions and molecular mechanisms, neuroimaging techniques such as positron emission tomography (PET) have been used. The development of new radiotracers for the different NPY receptors and their subsequent PET studies have led to significant insights into molecular mechanisms involving NPY receptors. This article provides a systematic review of the imaging biomarkers that have been developed as PET tracers in order to study the NPY receptor family.

Effects of Pituitary Adenylate Cyclase Activating Polypeptide on Cell Death

Pituitary adenylate cyclase activating polypeptide (PACAP) was first isolated as a hypothalamic peptide based on its efficacy to increase adenylate cyclase (AC) activity. It has a widespread distribution throughout the body including the nervous system and peripheral organs, where PACAP exerts protective effects both in vivo and in vitro through its anti-apoptotic, anti-inflammatory, and antioxidant functions. The aim of the present paper was to review the currently available literature regarding the effects of PACAP on cell death in vitro in neural and non-neural cells. Among others, its effect on apoptosis can be detected in cerebellar granule cells against different toxic stimuli. Different neural cell types from the cerebral cortex are also prevented from cell death. PACAP also shows effects on cell death in cells belonging to the peripheral nervous system and protects both neural and non-neural cells of sensory organs. In addition, cell survival-promoting effect can be observed in different peripheral organ systems including cardiovascular, immune, respiratory, gastrointestinal, urinary, and reproductive systems. The studies summarized here indicate its noteworthy effect on cell death in different in vitro models, suggesting PACAP’s potential therapeutic usage in several pathological conditions.

Pancreatic Ppy-expressing γ-cells display mixed phenotypic traits and the adaptive plasticity to engage insulin production

The cellular identity of pancreatic polypeptide (Ppy)-expressing γ-cells, one of the rarest pancreatic islet cell-type, remains elusive. Within islets, glucagon and somatostatin, released respectively from α- and δ-cells, modulate the secretion of insulin by β-cells. Dysregulation of insulin production raises blood glucose levels, leading to diabetes onset. Here, we present the genetic signature of human and mouse γ-cells. Using different approaches, we identified a set of genes and pathways defining their functional identity. We found that the γ-cell population is heterogeneous, with subsets of cells producing another hormone in addition to Ppy. These bihormonal cells share identity markers typical of the other islet cell-types. In mice, Ppy gene inactivation or conditional γ-cell ablation did not alter glycemia nor body weight. Interestingly, upon β-cell injury induction, γ-cells exhibited gene expression changes and some of them engaged insulin production, like α- and δ-cells. In conclusion, we provide a comprehensive characterization of γ-cells and highlight their plasticity and therapeutic potential.

Protective Effects of PACAP in Peripheral Organs

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuropeptide widely distributed in the nervous system, where it exerts strong neuroprotective effects. PACAP is also expressed in peripheral organs but its peripheral protective effects have not been summarized so far. Therefore, the aim of the present paper is to review the existing literature regarding the cytoprotective effects of PACAP in non-neuronal cell types, peripheral tissues, and organs. Among others, PACAP has widespread expression in the digestive system, where it shows protective effects in various intestinal pathologies, such as duodenal ulcer, small bowel ischemia, and intestinal inflammation. PACAP is present in both the exocrine and endocrine pancreas as well as liver where it reduces inflammation and steatosis by interfering with hepatic pathology related to obesity. It is found in several exocrine glands and also in urinary organs, where, with its protective effects being mainly published regarding renal pathologies, PACAP is protective in numerous conditions. PACAP displays anti-inflammatory effects in upper and lower airways of the respiratory system. In the skin, it is involved in the development of inflammatory pathology such as psoriasis and also has anti-allergic effects in a model of contact dermatitis. In the non-neuronal part of the visual system, PACAP showed protective effects in pathological conditions of the cornea and retinal pigment epithelial cells. The positive role of PACAP has been demonstrated on the formation and healing processes of cartilage and bone where it also prevents osteoarthritis and rheumatoid arthritis development. The protective role of PACAP was also demonstrated in the cardiovascular system in different pathological processes including hyperglycaemia-induced endothelial dysfunction and age-related vascular changes. In the heart, PACAP protects against ischemia, oxidative stress, and cardiomyopathies. PACAP is also involved in the protection against the development of pre-senile systemic amyloidosis, which is presented in various peripheral organs in PACAP-deficient mice. The studies summarized here provide strong evidence for the cytoprotective effects of the peptide. The survival-promoting effects of PACAP depend on a number of factors which are also shortly discussed in the present review.

Plant- and Nutraceutical-based Approach for the Management of Diabetes and its Neurological Complications: A Narrative Review

Diabetes is an important metabolic disease affecting many organs and systems in the body. The nervous system is one of the body systems affected by diabetes and neuropathic complications are troublesome in diabetic patients with many consequences. As diabetes has deleterious influences almost on bodily systems, an integrative approach seems to be necessary accepting the body as a whole and integrating body systems with lifestyle and living environment. Like some traditional health systems such as Ayurveda, integrative approach includes additional modalities to overcome both diabetes and diabetic complications. In general, these modalities consist of nutraceuticals and plant products. Prebiotics and probiotics are two types of nutraceuticals having active ingredients, such as antioxidants, nutrient factors, microorganisms, etc. Many plants are indicated for the cure of diabetes. All of these may be employed in the prevention and in the non-pharmacological management of mildto- moderate diabetes. Severe diabetes should require appropriate drug selection. Being complementary, prebiotics, probiotics, plants and exercise may be additive for the drug therapy of diabetes. Similarly, there are complementary approaches to prevent and cure neurological and/or behavioral manifestations of diabetes, which may be included in therapy and prevention plans. A scheme is given for the prevention and therapy of comorbid depression, which is one of the most common behavioral complications of diabetes. Within this scheme, the main criterion for the selection of modalities is the severity of diseases, so that personalized management may be developed for diabetic patients using prebiotics and probiotics in their diets, plants and drugs avoiding possible interactions.

Anxiety, Depression, and the Microbiome: A Role for Gut Peptides

The complex bidirectional communication between the gut and the brain is finely orchestrated by different systems, including the endocrine, immune, autonomic, and enteric nervous systems. Moreover, increasing evidence supports the role of the microbiome and microbiota-derived molecules in regulating such interactions; however, the mechanisms underpinning such effects are only beginning to be resolved. Microbiota-gut peptide interactions are poised to be of great significance in the regulation of gut-brain signaling. Given the emerging role of the gut-brain axis in a variety of brain disorders, such as anxiety and depression, it is important to understand the contribution of bidirectional interactions between peptide hormones released from the gut and intestinal bacteria in the context of this axis. Indeed, the gastrointestinal tract is the largest endocrine organ in mammals, secreting dozens of different signaling molecules, including peptides. Gut peptides in the systemic circulation can bind cognate receptors on immune cells and vagus nerve terminals thereby enabling indirect gut-brain communication. Gut peptide concentrations are not only modulated by enteric microbiota signals, but also vary according to the composition of the intestinal microbiota. In this review, we will discuss the gut microbiota as a regulator of anxiety and depression, and explore the role of gut-derived peptides as signaling molecules in microbiome-gut-brain communication. Here, we summarize the potential interactions of the microbiota with gut hormones and endocrine peptides, including neuropeptide Y, peptide YY, pancreatic polypeptide, cholecystokinin, glucagon-like peptide, corticotropin-releasing factor, oxytocin, and ghrelin in microbiome-to-brain signaling. Together, gut peptides are important regulators of microbiota-gut-brain signaling in health and stress-related psychiatric illnesses.

Effects of pituitary adenylate cyclase activating polypeptide on small intestinal INT 407 cells

Pituitary adenylate cyclase activating polypeptide (PACAP) is an endogenous neuropeptide having a widespread distribution both in the nervous system and peripheral organs including the gastrointestinal tract. It has been shown to exert actions on intestinal functions, mainly affecting glandular secretion and motility. PACAP has several different effects on cell survival depending on the cell type and the applied stimulus. Its influences on small intestinal epithelial cells are not yet elucidated, therefore the aim of the present study was to investigate the effects of PACAP on intestinal epithelial cells having high turnover (INT 407) against different harmful stimuli, such as oxidative stress, in vitro hypoxia and gamma radiation. We tested the effect of PACAP on proliferation and cell survival using MTT assay. Moreover, various cancer-related factors were evaluated by oncology array. PACAP did not influence the proliferation rate of INT 407 cells. Its cell survival-enhancing effect could be detected against oxidative stress, but not against in vitro hypoxia or gamma irradiation. Clonogenic survival assay was performed to analyze the effect of PACAP on clonogenic potential of cells exposed to gamma radiation. Surprisingly, PACAP enhanced the clone-forming ability decrease induced by irradiation. Western blot analysis of ERK1/2 phosphorylation was performed in order to obtain further information on the molecular background. Our data showed phospho-ERK1/2 suppression of PACAP in irradiated cells. Furthermore, the role of endogenous PACAP against oxidative stress was also investigated performing ADCYAP1 small interfering RNA transfection. We found significant difference in the cell vulnerability between cells undergoing silencing and cells without transfection suggesting the protective role of the endogenously present PACAP against oxidative stress in INT 407 cells. In summary, PACAP seems to be able to exert contradictory effects in INT 407 cells depending on the applied stressor, suggesting its regulatory role in the cellular household.

Purification and characterization of bioactive peptides RYamide and CCHamide in the kuruma shrimp Marsupenaeus japonicus

To understand the regulation systems of appetite, bioactive peptides from the kuruma shrimp Marsupenaeus japonicus (Mj) were isolated and purified by reverse pharmacological assays using CHO cells expressing the Drosophila melanogaster G-protein-coupled receptors (GPCRs) CG5811 (a RYamide receptor) or CG14593 (a CCHamide-2 receptor). Four peptides having binding activity to GPCRs were obtained and named Mj RYamide-1, Mj RYamide-2, Mj RYamide-3, and Mj CCHamide. Genes encoding the prepropeptides of these peptides were identified using kuruma shrimp transcriptome databases. The Mj prepro-RYamide gene encodes a 130-amino acid polypeptide containing Mj RYamide-1, Mj RYamide-2, and Mj RYamide-3, whereas the Mj prepro-CCHamide gene encodes a 119-amino acid polypeptide containing a single Mj CCHamide peptide. The expression of these genes was confirmed in various neuronal organs including the brain and ventral nerve cord. In addition, prepro-RYamide gene expression is significantly reduced in the brain after starvation. RYamides may thus be associated with regulation of feeding or digestion. Changes in kayak (the c-fos ortholog in invertebrates) gene expression after administration of synthetic peptides were also investigated. Mj kayak expression levels are upregulated in hepatopancreas after treatment with Mj RYamide-3 or CCHamide. Thus, the peptides isolated in this study may have some regulatory effect on cellular metabolism in aquacultured invertebrates.

Exposure to seawater increases intestinal motility in euryhaline rainbow trout (Oncorhynchus mykiss)

Upon exposure to seawater, euryhaline teleosts need to imbibe and desalinate seawater to allow for intestinal ion and water absorption, as this is essential for maintaining osmotic homeostasis. Despite the potential benefits of increased mixing and transport of imbibed water for increasing the efficiency of absorptive processes, the effect of water salinity on intestinal motility in teleosts remains unexplored. By qualitatively and quantitatively describing in vivo intestinal motility of euryhaline rainbow trout (Oncorhynchus mykiss), this study demonstrates that, in freshwater, the most common motility pattern consisted of clusters of rhythmic, posteriorly propagating contractions that lasted ∼1-2 min followed by a period of quiescence lasting ∼4-5 min. This pattern closely resembles mammalian migrating motor complexes (MMCs). Following a transition to seawater, imbibed seawater resulted in a significant distension of the intestine and the frequency of MMCs increased twofold to threefold with a concomitant reduction in the periods of quiescence. The increased frequency of MMCs was also accompanied by ripple-type contractions occurring every 12-60 s. These findings demonstrate that intestinal contractile activity of euryhaline teleosts is dramatically increased upon exposure to seawater, which is likely part of the overall response for maintaining osmotic homeostasis as increased drinking and mechanical perturbation of fluids is necessary to optimise intestinal ion and water absorption. Finally, the temporal response of intestinal motility in rainbow trout transitioning from freshwater to seawater coincides with previously documented physiological modifications associated with osmoregulation and may provide further insight into the underlying reasons shaping the migration patterns of salmonids.

Glutinous rice amylopectin can adjust the plasma gut-regulated peptide levels in rhubarb-induced spleen deficiency rats

The pharmacological effects of glutinous rice (GR) and GR amylopectin (GRA) on the gastrointestine were investigated in rhubarb-induced spleen deficiency rats by determining the levels of gastrointestinal hormones such as the peptides serum gastrin, amylase motilin, and somatostatin. GR and GRA were given by gavage at various doses of GR (7.5, 15, and 30 g per kg body weight) and GRA (3.8, 7.6, and 15 g per kg body weight) every day for 4 weeks, respectively. The results indicated that the final body weight of rats in the highest-dose GR (GRH) group and all the GRA groups significantly (P < 0.05) increased (7.2-12.1%) compared with the model control (MC) group. All the GR and GRA treated groups had significantly (P < 0.05) higher gastrin contents (32.8-51.2%), motilin levels (13.8-39.2%), and amylase contents (22.5-39.4%) and the GRH and highest-dose GRA (GRAH) groups had significantly (P < 0.05) lower somatostatin contents compared with the MC group. Meanwhile, the somatostatin contents were negatively correlated with the motilin levels (r = -0.964, P < 0.01) and amylase contents (r = -0.981, P < 0.01). The GRAH treatment group had the highest final body weight, gastrin contents, motilin levels, and amylase contents and the lowest somatostatin contents, which demonstrated that GRA might play the most important role in the spleen-regulating activities of GR.

Chromogranin A and other enteroendocrine markers in inflammatory bowel disease

Changes in the distribution and products of enteroendocrine cells may play a role in immune activation and regulation of gut inflammation. This review aims at critically evaluating the main enteroendocrine markers in inflammatory bowel diseases (IBD). A narrative review was performed by searching inflammatory bowel diseases and enteroendocrine biomarkers in PubMed. Relevant modifications of some enteroendocrine markers, such as Chromogranin A, and their correlation with disease activity have been reported in patients with inflammatory bowel diseases. Even if data about neuroendocrine markers are sometimes contrasting, they may be potentially useful for the diagnosis and clinical management of these patients.

Vagal neurocircuitry and its influence on gastric motility

A large body of research has been dedicated to the effects of gastrointestinal peptides on vagal afferent fibres, yet multiple lines of evidence indicate that gastrointestinal peptides also modulate brainstem vagal neurocircuitry, and that this modulation has a fundamental role in the physiology and pathophysiology of the upper gastrointestinal tract. In fact, brainstem vagovagal neurocircuits comprise highly plastic neurons and synapses connecting afferent vagal fibres, second order neurons of the nucleus tractus solitarius (NTS), and efferent fibres originating in the dorsal motor nucleus of the vagus (DMV). Neuronal communication between the NTS and DMV is regulated by the presence of a variety of inputs, both from within the brainstem itself as well as from higher centres, which utilize an array of neurotransmitters and neuromodulators. Because of the circumventricular nature of these brainstem areas, circulating hormones can also modulate the vagal output to the upper gastrointestinal tract. This Review summarizes the organization and function of vagovagal reflex control of the upper gastrointestinal tract, presents data on the plasticity within these neurocircuits after stress, and discusses the gastrointestinal dysfunctions observed in Parkinson disease as examples of physiological adjustment and maladaptation of these reflexes.

Differential effects in CGRPergic, nitrergic, and VIPergic myenteric innervation in diabetic rats supplemented with 2% L-glutamine

ABSTRACT The objective of this study was to investigate the effects of 2% L-glutamine supplementation on myenteric innervation in the ileum of diabetic rats, grouped as follows: normoglycemic (N); normoglycemic supplemented with L-glutamine (NG); diabetic (D); and diabetic supplemented with L-glutamine (DG). The ileums were subjected to immunohistochemical techniques to localize neurons immunoreactive to HuC/D protein (HuC/D-IR) and neuronal nitric oxide synthase enzyme (nNOS-IR) and to analyze varicosities immunoreactive to vasoactive intestinal polypeptide (VIP-IR) and calcitonin gene-related peptide (CGRP-IR). L-Glutamine in the DG group (i) prevented the increase in the cell body area of nNOS-IR neurons, (ii) prevented the increase in the area of VIP-IR varicosities, (iii) did not prevent the loss of HuC/D-IR and nNOS-IR neurons per ganglion, and (iv) reduced the size of CGRP-IR varicosities. L-Glutamine in the NG group reduced (i) the number of HuC/D-IR and nNOS-IR neurons per ganglion, (ii) the cell body area of nNOS-IR neurons, and (iii) the size of VIP-IR and CGRP-IR varicosities. 2% L-glutamine supplementation exerted differential neuroprotective effects in experimental diabetes neuropathy that depended on the type of neurotransmitter analyzed. However, the effects of this dose of L-glutamine on normoglycemic animals suggests there are additional actions of this beyond its antioxidant capacity.

Neuropeptide Y in noradrenergic neurons induces obesity in transgenic mouse models

Neuropeptide Y (NPY) in noradrenergic neurons plays an important role in modulating the release and effects of catecholamines in a prolonged stress response. Among other functions, it controls energy metabolism. Transgenic expression of Npy in noradrenergic neurons in mice allowed showing that it is critical for diet- and stress-induced gain in fat mass. When overexpressed, NPY in noradrenergic neurons increases adiposity in gene-dose-dependent fashion, and leads to metabolic disorders such as impaired glucose tolerance. However, the mechanisms of obesity seem to be different in mice heterozygous and homozygous for the Npy transgene. While in heterozygous mice the adipogenic effect of NPY is important, in homozygous mice inhibition of sympathetic tone leading to decreased lipolytic activity and impaired brown fat function, as well as increased endocannabinoid levels contribute to obesity. The mouse model provides novel insight to the mechanisms of human diseases with increased NPY due to chronic stress or gain-of-function gene variants, and a tool for development of novel therapeutics.

Influence of renovascular hypertension on the distribution of vasoactive intestinal peptide in the stomach and heart of rats

Arterial hypertension is associated with serious dysfunction of the cardiovascular system and digestive system. Given the relevant role of vasoactive intestinal peptide (VIP) in the regulation of digestion process, control of blood pressure and heart rate as well as cardio- and gastro-protective character of the peptide, it appeared worthwhile to undertake the research aimed at immunohistochemical identification and evaluation of VIP-positive structures in the pylorus and heart of hypertensive rats. Up to now, this issue has not been investigated. The experimental model of hypertension in rats according to Goldblatt (two-kidney one clip model of hypertension) was used in the study. The experimental material (pylorus and heart) was collected in the sixth week of the study. VIP-containing structures were evaluated using immunohistochemical and morphometric methods. The analysis of the results showed a significant increase in the number of immunoreactive VIP structures and in the intensity of immunohistochemical staining in the stomach and in the heart of hypertensive rats. Our findings indicate that VIP is an important regulator of cardiovascular and digestive system in physiological and pathological conditions. However, to better understand the exact role of VIP in hypertension further studies need to be carried out.

Attenuation of stress-induced gastrointestinal motility disorder by gentiopicroside, from Gentiana macrophylla Pall

AIM

The current study was designed to explore the mechanism of the prokinetic activity of Gentiopicroside (Ge), from Gentiana macrophylla Pall which is widely used to strengthen gastric motility in clinic.

METHODS

Gastrointestinal motility disorder rats were induced by stress stimulation and the rats were treated with Ge. The functions of gastric emptying and intestinal propelling were measured after blood was obtained to assay the levels of plasmatic motilin (MTL), vasoactive intestinal peptide (VIP), somatostatin (SST), gastrin (GAS), neurotensin (NT) and substance of P (SP). The expressions of MTL receptor (MTLR), VIP receptor 2 (VIPR2) and SST receptor 2 (SSTR2) were measured also. In addition, an isolated guinea pig ileum was applied to evaluate the influences of Ge on M-R, H1-R, 5-HT4-R and D-R in vitro.

RESULTS

Ge increased gastric emptying and intestinal propelling obviously. It also decreased the level of SST and increased GAS in plasma significantly. Moreover, it promoted the expressions of MTLR in gastric antrum, duodenum, jejunum and ileum, and restrained the expression of VIPR2 in duodenum. Piboserod and loratadine had no obvious restrain to Ge' exciting ileum effect and Ge also didn't affect dopamine paralyzing ileum. However, Ge failed to improve the hypofunction of guinea pigs ileums pre-treated with atropine sulfate.

CONCLUSION

The mechanisms of Ge' prokinetic effect were associated with modulating the levels of SST and GAS in plasma, raising the expressions of MTLR in gastric antrum, duodenum, ileum and jejunum, reducing the expression of VIPR2 in duodenum and activating M-R.

Neuropeptide Y in the noradrenergic neurones induces obesity and inhibits sympathetic tone in mice

AIM

Neuropeptide Y (NPY) co-localized with noradrenaline in central and sympathetic nervous systems seems to play a role in the control of energy metabolism. In this study, the aim was to elucidate the effects and pathophysiological mechanisms of increased NPY in catecholaminergic neurones on accumulation of body adiposity.

METHODS

Transgenic mice overexpressing NPY under the dopamine-beta-hydroxylase promoter (OE-NPY(DβH) ) and wild-type control mice were followed for body weight gain and body fat content. Food intake, energy expenditure, physical activity, body temperature, serum lipid content and markers of glucose homoeostasis were monitored. Thermogenic and lipolytic responses in adipose tissues, and urine catecholamine and tissue catecholamine synthesizing enzyme levels were analysed as indices of sympathetic tone.

RESULTS

Homozygous OE-NPY(DβH) mice showed significant obesity accompanied with impaired glucose tolerance and insulin resistance. Increased adiposity was explained by neither increased food intake or fat absorption nor by decreased total energy expenditure or physical activity. Adipocyte hypertrophy and decreased circulating lipid levels suggested decreased lipolysis and increased lipid uptake. Brown adipose tissue thermogenic capacity was decreased and brown adipocytes filled with lipids. Enhanced response to adrenergic stimuli, downregulation of catecholamine synthesizing enzyme expressions in the brainstem and lower adrenaline excretion supported the notion of low basal catecholaminergic activity.

CONCLUSION

Increased NPY in catecholaminergic neurones induces obesity that seems to be a result of preferential fat storage. These results support the role of NPY as a direct effector in peripheral tissues and an inhibitor of sympathetic activity in the pathogenesis of obesity.

The homeostatic role of neuropeptide Y in immune function and its impact on mood and behaviour

Neuropeptide Y (NPY), one of the most abundant peptides in the nervous system, exerts its effects via five receptor types, termed Y1, Y2, Y4, Y5 and Y6. NPY's pleiotropic functions comprise the regulation of brain activity, mood, stress coping, ingestion, digestion, metabolism, vascular and immune function. Nerve-derived NPY directly affects immune cells while NPY also acts as a paracrine and autocrine immune mediator, because immune cells themselves are capable of producing and releasing NPY. NPY is able to induce immune activation or suppression, depending on a myriad of factors such as the Y receptors activated and cell types involved. There is an intricate relationship between psychological stress, mood disorders and the immune system. While stress represents a risk factor for the development of mood disorders, it exhibits diverse actions on the immune system as well. Conversely, inflammation is regarded as an internal stressor and is increasingly recognized to contribute to the pathogenesis of mood and metabolic disorders. Intriguingly, the cerebral NPY system has been found to protect against distinct disturbances in response to immune challenge, attenuating the sickness response and preventing the development of depression. Thus, NPY plays an important homeostatic role in balancing disturbances of physiological systems caused by peripheral immune challenge. This implication is particularly evident in the brain in which NPY counteracts the negative impact of immune challenge on mood, emotional processing and stress resilience. NPY thus acts as a unique signalling molecule in the interaction of the immune system with the brain in health and disease.

Effects of feeding on in vivo motility patterns in the proximal intestine of shorthorn sculpin (Myoxocephalus scorpius)

This is the first study to catalogue the diverse array of in vivo motility patterns in a teleost fish and how they are affected by feeding. Video recordings of exteriorised proximal intestine from fasted and fed shorthorn sculpin (Myoxocephalus scorpius) were used to generate spatio-temporal maps to portray and quantify motility patterns. Propagating and non-propagating contractions were observed to occur at different frequencies and durations. The most apparent difference between the feeding states was that bands of relatively high amplitude contractions propagating slowly in the anal direction were observed in all fasted fish (N=10) but in only 35% of fed fish (N=11). Additionally, fed fish displayed a reduced frequency (0.21±0.03 versus 0.32±0.06 contractions min(-1)) and rhythmicity of these contractions compared with fasted fish. Although the underlying mechanisms of these slow anally propagating contractions differ from those of mammalian migrating motor complexes, we believe that they may play a similar role in shorthorn sculpin during the interdigestive period, to potentially remove food remnants and prevent the establishment of pathogens. 'Ripples' were the most prevalent contraction type in shorthorn sculpin and may be important during mixing and absorption. The persistence of shallow ripples and pendular movements of longitudinal muscle after tetrodotoxin (1 μmol l(-1)) treatment suggests these contractions were myogenic in origin. The present study highlights both similarities and differences in motility patterns between shorthorn sculpin and other vertebrates, as well as providing a platform to examine other aspects of gastrointestinal functions in fish, including the impact of environmental changes.

Plasticity in the brainstem vagal circuits controlling gastric motor function triggered by corticotropin releasing factor

Stress impairs gastric emptying, reduces stomach compliance and induces early satiety via vagal actions. We have shown recently that the ability of the anti-stress neuropeptide oxytocin (OXT) to modulate vagal brainstem circuits undergoes short-term plasticity via alterations in cAMP levels subsequent to vagal afferent fibre-dependent activation of metabotropic glutamate receptors. The aim of the present study was to test the hypothesis that the OXT-induced gastric response undergoes plastic changes in the presence of the prototypical stress hormone, corticotropin releasing factor (CRF). Whole cell patch clamp recordings showed that CRF increased inhibitory GABAergic synaptic transmission to identified corpus-projecting dorsal motor nucleus of the vagus (DMV) neurones. In naive brainstem slices, OXT perfusion had no effect on inhibitory synaptic transmission; following exposure to CRF (and recovery from its actions), however, re-application of OXT inhibited GABAergic transmission in the majority of neurones tested. This uncovering of the OXT response was antagonized by pretreatment with protein kinase A or adenylate cyclase inhibitors, H89 and di-deoxyadenosine, respectively, indicating a cAMP-mediated mechanism. In naive animals, OXT microinjection in the dorsal vagal complex induced a NO-mediated corpus relaxation. Following CRF pretreatment, however, microinjection of OXT attenuated or, at times reversed, the gastric relaxation which was insensitive to l-NAME but was antagonized by pretreatment with a VIP antagonist. Immunohistochemical analyses of vagal motoneurones showed an increased number of oxytocin receptors present on GABAergic terminals of CRF-treated or stressed vs. naive rats. These results indicate that CRF alters vagal inhibitory circuits that uncover the ability of OXT to modulate GABAergic currents and modifies the gastric corpus motility response to OXT.

Vagal afferent fibres determine the oxytocin-induced modulation of gastric tone

Oxytocin (OXT) inputs to the dorsal vagal complex (DVC; nucleus of the tractus solitarius (NTS) dorsal motor nucleus of the vagus (DMV) and area postrema) decrease gastric tone and motility. Our first aim was to investigate the mechanism(s) of OXT-induced gastric relaxation. We demonstrated recently that vagal afferent inputs modulate NTS-DMV synapses involved in gastric and pancreatic reflexes via group II metabotropic glutamate receptors (mGluRs). Our second aim was to investigate whether group II mGluRs similarly influence the response of vagal motoneurons to OXT. Microinjection of OXT in the DVC decreased gastric tone in a dose-dependent manner. The OXT-induced gastric relaxation was enhanced following bethanechol and reduced by l-NAME administration, suggesting a nitrergic mechanism of gastroinhibition. DVC application of the group II mGluR antagonist EGLU induced a gastroinhibition that was not dose dependent and shifted the gastric effects of OXT to a cholinergic-mediated mechanism. Evoked and miniature GABAergic synaptic currents between NTS and identified gastric-projecting DMV neurones were not affected by OXT in any neurones tested, unless the brainstem slice was (a) pretreated with EGLU or (b) derived from rats that had earlier received a surgical vagal deafferentation. Conversely, OXT inhibited glutamatergic currents even in naive slices, but their responses were unaffected by EGLU pretreatment. These results suggest that the OXT-induced gastroinhibition is mediated by activation of the NANC pathway. Inhibition of brainstem group II mGluRs, however, uncovers the ability of OXT to modulate GABAergic transmission between the NTS and DMV, resulting in the engagement of an otherwise silent cholinergic vagal neurocircuit.

Orexin system expression in the gastrointestinal tract of pigs

The aim of the present study was to characterize the expression of both proteins and gene transcripts for orexins (OXA and OXB) and their cognate receptors (OX1R and OX2R) in the different gastrointestinal sections of pigs. Using immunohistochemistry, OXA and OXB were found to be co-expressed in the same endocrine cells localized in the basal third of the glands of the body portion of the stomach. Using double immunostaining technique, these orexin-immunoreactive (IR) cells co-stored ghrelin and gastrin. Apparently, OX1R was also expressed within the same cells, forming the tubular gastric gland which displayed positive immunostaining for orexins and the other peptides. Neurons of the enteric nervous system of the stomach were not immunolabeled. We did not find any definite OXA- or OXB-IR cells as well as any immunosignal for orexin receptors in sections of the duodenum, ileum, cecum and rectum. PPOX, OX1R, OX2R mRNA were similarly expressed in all the gastrointestinal tracts. Gastrin and ghrelin showed the highest levels of expression in the gastric mucosa, but their abundance decreased along the subsequent tracts. Thus, in pigs, orexins do not play any role in the local control of intestinal motility and secretion but may rather be involved as endocrine modulators for the regulation of feeding and metabolic homeostasis. However, the co-localization of ghrelin and gastrin with both orexins in the same endocrine cells of the gastric glands suggests that these gut peptides may collaborate in the regulation of gastric secretion, energy homeostasis, body weight and food intake.

Neuropeptide Y, peptide YY and pancreatic polypeptide in the gut-brain axis

The gut-brain axis refers to the bidirectional communication between the gut and the brain. Four information carriers (vagal and spinal afferent neurons, immune mediators such as cytokines, gut hormones and gut microbiota-derived signalling molecules) transmit information from the gut to the brain, while autonomic neurons and neuroendocrine factors carry outputs from the brain to the gut. The members of the neuropeptide Y (NPY) family of biologically active peptides, NPY, peptide YY (PYY) and pancreatic polypeptide (PP), are expressed by cell systems at distinct levels of the gut-brain axis. PYY and PP are exclusively expressed by endocrine cells of the digestive system, whereas NPY is found at all levels of the gut-brain and brain-gut axis. The major systems expressing NPY comprise enteric neurons, primary afferent neurons, several neuronal pathways throughout the brain and sympathetic neurons. In the digestive tract, NPY and PYY inhibit gastrointestinal motility and electrolyte secretion and in this way modify the input to the brain. PYY is also influenced by the intestinal microbiota, and NPY exerts, via stimulation of Y1 receptors, a proinflammatory action. Furthermore, the NPY system protects against distinct behavioural disturbances caused by peripheral immune challenge, ameliorating the acute sickness response and preventing long-term depression. At the level of the afferent system, NPY inhibits nociceptive input from the periphery to the spinal cord and brainstem. In the brain, NPY and its receptors (Y1, Y2, Y4, Y5) play important roles in regulating food intake, energy homeostasis, anxiety, mood and stress resilience. In addition, PP and PYY signal to the brain to attenuate food intake, anxiety and depression-related behaviour. These findings underscore the important role of the NPY-Y receptor system at several levels of the gut-brain axis in which NPY, PYY and PP operate both as neural and endocrine messengers.

Oxytocin-immunoreactive innervation of identified neurons in the rat dorsal vagal complex

BACKGROUND

Oxytocin (OXT) has been implicated in reproduction and social interactions and in the control of digestion and blood pressure. OXT-immunoreactive axons occur in the dorsal vagal complex (DVC; nucleus tractus solitarius, NTS, dorsal motor nucleus of the vagus, DMV, and area postrema, AP), which contains neurons that regulate autonomic homeostasis. The aim of the present work is to provide a systematic investigation of the OXT-immunoreactive innervation of dorsal motor nucleus of the vagus (DMV) neurons involved in the control of gastrointestinal (GI) function.

METHODS

We studied DMV neurons identified by (i) prior injection of retrograde tracers in the stomach, ileum, or cervical vagus or (ii) induction of c-fos expression by glucoprivation with 2-deoxyglucose. Another subgroup of DMV neurons was identified electrophysiologically by stimulation of the cervical vagus and then juxtacellularly labeled with biotinamide. We used two- or three-color immunoperoxidase labeling for studies at the light microscopic level.

KEY RESULTS

Close appositions from OXT-immunoreactive varicosities were found on the cell bodies, dendrites, and axons of DMV neurons that projected to the GI tract and that responded to 2-deoxyglucose and juxtacellularly labeled DMV neurons. Double staining for OXT and choline acetyltransferase revealed that OXT innervation was heavier in the caudal and lateral DMV than in other regions. OXT-immunoreactive varicosities also closely apposed a small subset of tyrosine hydroxylase-immunoreactive NTS and DMV neurons.

CONCLUSIONS & INFERENCES

Our results provide the first anatomical evidence for direct OXT-immunoreactive innervation of GI-related neurons in the DMV.

Postoperative ileus: Impact of pharmacological treatment, laparoscopic surgery and enhanced recovery pathways

Almost all patients develop postoperative ileus (POI) after abdominal surgery. POI represents the single largest factor influencing length of stay (LOS) after bowel resection, and has great implications for patients and resource utilization in health care. New methods to treat and decrease the length of POI are therefore of great importance. During the past decade, a substantial amount of research has been performed evaluating POI, and great progress has been made in our understanding and treatment of POI. Laparoscopic procedures, enhanced recovery pathways and pharmacologic treatment have been introduced. Each factor has substantially contributed to decreasing the length of POI and thus LOS after bowel resection. This editorial outlines resource utilization of POI, normal physiology of gut motility and pathogenesis of POI. Pharmacological treatment, fast track protocols and laparoscopic surgery can each have significant impact on pathways causing POI. The optimal integration of these treatment options continues to be assessed in prospective studies.

Influence of Weitongxiaopi Decoction on gastrointestinal motility and plasma motilin levels in rats with functional dyspepsia caused by spleen-stomach deficiency-cold

AIM: To observe the impact of Weitongxiaopi (WTXP) Decoction on gastrointestinal motility and plasma motilin levels in rats with functional dyspepsia (FD) due to spleen-stomach deficiency-cold.

METHODS: FD was induced in 66 rats by giving vinegar. The rats were then randomly divided into six groups: normal control group, model control group, low-dose WTXP Decoction group, medium-dose WTXP Decoction group, high-dose WTXP Decoction group and domperidone group. The latter five groups were given normal saline, different concentrations of WTXP Decoction and domperidone by gastrogavage twice a day for 14 days. Plasma motilin (MOT) level, gastric emptying rate and small intestinal propulsion rate were measured.

RESULTS: WTXP Decoction at all concentrations could significantly increase plasma MOT levels and small intestinal propulsion rates in FD model rats (MOT: 104.57 pmol/L ± 14.05 pmol/L, 124.90 pmol/L ± 15.21 pmol/L, and 125.84 pmol/L ± 27.67 pmol/Lvs 81.95 pmol/L ± 12.02 pmol/L, all P < 0.01; small intestinal propulsion rate: 55.62% ± 2.92%, 56.91% ± 4.65%, and 59.04% ± 3.24% vs 51.80% ± 3.57%; all P < 0.01). No significant differences were noted in small intestinal propulsion rates among the normal control group, medium- and high-dose WTXP Decoction groups (all P > 0.05). However, the small intestinal propulsion rates in these three groups were better than that in the domperidone group (all P < 0.01). Although WTXP Decoction at all concentrations could improve gastric emptying rate, there were no significant differences in gastric emptying rates between the WTXP Decoction groups and the domperidone group (all P > 0.05).

CONCLUSION: WTXP Decoction can promote gastrointestinal motility in rats with FD due to spleen-stomach deficiency-cold by increasing plasma MOT levels.

Modulation of inhibitory neurotransmission in brainstem vagal circuits by NPY and PYY is controlled by cAMP levels

Pancreatic polypeptides such as neuropeptide Y (NPY) and peptide YY (PYY) exert profound, vagally mediated effects on gastrointestinal (GI) motility. Vagal efferent outflow to the GI tract is determined principally by tonic GABAergic synaptic inputs onto dorsal motor nucleus of the vagus (DMV) neurons, yet neither peptide modulates GABAergic transmission. We showed recently that opioid peptides appear similarly ineffective because of the low resting cAMP levels. Using whole cell recordings from identified DMV neurons, we aimed to correlate the influence of brainstem cAMP levels with the ability of pancreatic polypeptides to modulate GABAergic synaptic transmission. Neither NPY, PYY, nor the Y1 or Y2 receptor selective agonists [Leu,Pro]NPY or NPY(3-36) respectively, inhibited evoked inhibitory postsynaptic current (eIPSC) amplitude unless cAMP levels were elevated by forskolin or 8-bromo-cAMP, by exposure to adenylate cyclase-coupled modulators such as cholecystokinin octapeptide (sulfated) (CCK-8s) or thyrotropin releasing hormone (TRH), or by vagal deafferentation. The inhibition of eIPSC amplitude by [Leu,Pro]NPY or NPY(3-36) was stable for approximately 30 min following the initial increase in cAMP levels. Thereafter, the inhibition declined gradually until the agonists were again ineffective after 60 min. Analysis of spontaneous and miniature currents revealed that such inhibitory effects were due to actions at presynaptic Y1 and Y2 receptors. These results suggest that, similar to opioid peptides, the effects of pancreatic polypeptides on GABAergic transmission depend upon the levels of cAMP within gastric inhibitory vagal circuits.

Involvement of apolipoprotein A-IV and cholecystokinin1 receptors in exogenous peptide YY3 36-induced stimulation of intestinal feedback

Peptide YY (PYY)(3-36), released by intestinal lipid elicits functional effects that comprise the intestinal feedback response to luminal nutrients, but the pathway of action is not fully characterized. The aim of the present study was to determine the role of the apolipoprotein (apo) A-IV-cholecystokinin (CCK)(1) receptor (CCK(1)R) pathway in exogenous PYY(3-36)-induced activation of the gut-brain axis and inhibition of gastric emptying and food intake. PYY(3-36) (5 microg/100 g ip) significantly inhibited gastric emptying of a chow meal in wild-type but not A-IV(-/-) mice andCCK(1)R receptor blockade with devazepide (10 microg/100 g), abolished PYY(3-36)-induced inhibition of gastric emptying. PYY(3-36)-induced inhibition of food intake in both ad libitum-fed and 16-h fasted mice was unaltered in A-IV(-/-) mice, compared with wild-type controls, or by CCK(1)R receptor blockade with devazepide. PYY(3-36) activated neurons in the midregion of the nucleus of the solitary tract (bregma -7.32 to -7.76 mm) in A-IV(+/+) mice; this was measured by immunohistochemical localization of Fos protein. PYY(3-36)-induced Fos expression was significantly reduced by 65% in A-IV(+/+) mice pretreated systemically with the sensory neurotoxin capsaicin (5 mg/100 g), 78% by the CCK(1)R antagonist, devazepide (10 microg/100 g), and 39% by the Y2R antagonist, BIIE0246 (200 and 600 microg/100 g) and decreased by 67% in apo A-IV(-/-) mice, compared with A-IV(+/+) controls. The data suggest a role for apo A-IV and the CCK(1)R in PYY(3-36)-induced activation of the vagal afferent pathway and inhibition of gastric emptying, but this is likely not the pathway mediating the effects of PYY(3-36) on food intake.

Gastrointestinal dysfunction in mice with a targeted mutation in the gene encoding vasoactive intestinal polypeptide: a model for the study of intestinal ileus and Hirschsprung's disease

In 1970, Drs. Said and Mutt isolated a novel peptide from porcine intestinal extracts with powerful vasoactive properties, and named it vasoactive intestinal peptide (VIP). Since then, the biological actions of VIP in the gut as well as its signal transduction pathways have been extensively studied. A variety of in vitro and in vivo studies have indicated that VIP, expressed in intrinsic non-adrenergic non-cholinergic (NANC) neurons, is a potent regulator of gastrointestinal (GI) motility, water absorption and ion flux, mucus secretion and immune homeostasis. These VIP actions are believed to be mediated mainly by interactions with highly expressed VPAC(1) receptors and the production of nitric oxide (NO). Furthermore, VIP has been implicated in numerous physiopathological conditions affecting the human gut, including pancreatic endocrine tumors secreting VIP (VIPomas), insulin-dependent diabetes, Hirschsprung's disease, and inflammatory bowel syndromes such as Crohn's disease and ulcerative colitis. To further understand the physiological roles of VIP on the GI tract, we have begun to analyze the anatomical and physiological phenotype of C57BL/6 mice lacking the VIP gene. Herein, we demonstrate that the overall intestinal morphology and light microscopic structure is significantly altered in VIP(-/-) mice. Macroscopically there is an overall increase in weight, and decrease in length of the bowel compared to wild type (WT) controls. Microscopically, the phenotype was characterized by thickening of smooth muscle layers, increased villi length, and higher abundance of goblet cells. Alcian blue staining indicated that the latter cells were deficient in mucus secretion in VIP(-/-) mice. The differences became more pronounced from the duodenum to the distal jejunum or ileum of the small bowel but, became much less apparent or absent in the colon with the exception of mucus secretion defects. Further examination of the small intestine revealed larger axonal trunks and unusual unstained patches in myenteric plexus. Physiologically, the VIP(-/-) mice showed an impairment in intestinal transit. Moreover, unlike WT C57BL/6 mice, a significant percentage of VIP(-/-) mice died in the first postnatal year with overt stenosis of the gut.

Survival and neurotransmitter plasticity in cultured rat colonic myenteric neurons

The enteric nervous system is of great importance for maintenance and proper function of the gastrointestinal tract. The aim of this study was to quantify myenteric neuronal subpopulations expressing calcitonin gene-related peptide (CGRP), galanin, neuropeptide Y (NPY), somatostatin, vasoactive intestinal peptide (VIP) and nitric oxide synthase (NOS) in rat colon in vivo and after culturing. Further we investigated if culturing in the presence of CGRP, galanin, VIP, S-nitroso-N-acetyl-D,L-penicillamine (SNAP, a NO donor) or N-nitro-L-arginine methyl ester (L-NAME, a NOS inhibitor) affect neuronal survival. After 4 days of culturing the proportions of neurons expressing CGRP, NPY, somatostatin or VIP increased as compared to in vivo, while the proportions of neurons expressing galanin or NOS did not change. Neuronal survival was unaffected after culturing in media enriched with CGRP, galanin, VIP, SNAP or L-NAME. Neither did addition of CGRP, galanin nor VIP to the cultures affect the relative numbers of neurons expressing CGRP, galanin or VIP respectively. Addition of SNAP or L-NAME did not change the percentage of neurons expressing NOS. In conclusion, cultured rat colonic myenteric neurons increase their expression of CGRP, NPY, somatostatin and VIP, suggesting that these neuropeptides are of importance for neuronal survival.

Anorexia in cancer: role of feeding-regulatory peptides

Anorexia is one of the most common symptoms in advanced cancer and is a frequent cause of discomfort for cancer patients and their families. The pathogenesis of cancer anorexia is multi-factorial and involves most of the hypothalamic neuronal signalling pathways modulating energy homeostasis. It is considered to be the result of a failure of usual appetite and satiety signals. Loss of appetite can arise from decreased taste and smell of food, as well as from dysfunctional hypothalamic signalling pathways and cytokine production. Cytokines in particular, appear to play a key role in energy balance through persistent activation of the melanocortin system and inhibition of the neuropeptide Y pathway. The imbalance between anorexigenic and orexigenic peptides leads to suppression of appetite, and increased satiety and satiation associated with marked weight loss and decline in physical performance. High levels of serotonin also appear to contribute to these effects and recent findings implicate corticotropin-releasing factor in the pathogenesis of cancer anorexia as well. Despite significant advances in our understanding of the regulation of food intake and energy expenditure, few effective therapies are available. A better appreciation of the molecular and neuronal mechanisms that control body weight homeostasis may lead to the development of new therapies for improving the survival and quality of life of these patients.

Insights on zinc regulation of food intake and macronutrient selection

Zinc (Zn) is an essential trace element required for human beings and animals. This divalent cation is involved in many physiological functions, including immune and antioxidant function, growth, and reproduction. Deficiency of Zn produces several pathological disorders and abnormalities in its metabolism, such as anorexia, weight loss, poor efficiency, and growth retardation. Although it has been known for more than 50 yr that Zn deficiency regularly and consistently causes anorexia in many animal species, the mechanism that causes this phenomenon still remains an enigma. The present review describes recent research investigating the relationship between Zn deficiency and the regulation of food intake, as well as macronutrient selection.

Effect on components of the intestinal microflora and plasma neuropeptide levels of feeding Lactobacillus delbrueckii, Bifidobacterium lactis, and inulin to adult and elderly rats

The aim of this study was to compare the effects of the mixture of Lactobacillus delbrueckii subsp. rhamnosus strain GG, Bifidobacterium lactis Bb12, and inulin on intestinal populations of lactobacilli, bifidobacteria, and enterobacteria in adult and elderly rats fed the same (in quality and quantity) diet. The portal plasma levels of two neuropeptides, neuropeptide Y (NPY) and peptide YY (PYY), were also evaluated to assess the physiological consequences of the synbiotic treatment for the gastrointestinal (GI) tracts of rats of different ages. Adult (n = 24) and elderly (n = 24) male rats were fed the AIN-93 M maintenance diet. After 2 weeks of adaptation, the diet of 12 rats of each age group was supplemented with 8% inulin and with strains GG and Bb12 to provide 2.2 x 10(9) CFU of each strain g(-1) of the diet. Blood and different regions of the GI tract were sampled from all rats after 21 days of the treatment. Treatment with the mixture of strain GG, strain BB12, and inulin induced significantly different changes in the numbers of lactobacilli, bifidobacteria, and enterobacteria of the stomach, small intestine, cecum, and colon microflora. Moreover, the GG, BB12, and inulin mixture increased the concentrations of NPY and PYY for adult rats. For the elderly animals, the PYY concentration was not changed, while the NPY concentration was decreased by treatment with the GG, BB12, and inulin mixture. The results of the present study indicate that the physiological status of the GI tract, and not just diet, has a major role in the regulation of important groups of the GI bacteria community, since even the outcome of the dietary modification with synbiotics depends on the ages of the animals.

Cachexia: lessons from melanocortin antagonism

It is well established that disruptions in melanocortin signaling in the CNS result in morbid obesity, but only recently has evidence linked the activation of this system with the production of cachexia, also known as disease-associated wasting. Pro-opiomelanocortin-producing neurons, which express cytokine receptors, show increased activation in the presence of several cytokines that are increased in diseases that are associated with cachexia. Recent experiments show that blockade of melanocortin signaling using antagonists to the melanocortin MC(4) receptor attenuates disease-associated anorexia and wasting in rodent models of cancer and renal failure. This successful inhibition of cachexia is important because loss of appetite and lean body mass worsen the prognosis of many the diseases with which cachexia is associated.

Peripheral and centrally mediated effects of insulin on small intestinal transit in healthy mice

1. Insulin is the drug of choice in the management of type 1 diabetes mellitus. Approximately 76% of diabetic patients suffer from gastrointestinal disorders. An important area of investigating the inherent effect of insulin on small intestinal transit (SIT) remains unexplored. Hence, the present study was planned to investigate the effects of insulin (2 x 10(-6), 2 x 10(-3) and 2 U/kg) on small intestinal transit following two different routes of administration in healthy animals. 2. Insulin or vehicle was administered subcutaneously or intracerebroventricularly in eight groups of healthy, overnight-fasted mice. Blood glucose (BG) levels were measured 2 min before insulin administration and at the time coinciding with SIT determination. Small intestinal transit was determined 50 min after insulin administration using the charcoal meal method. 3. Following subcutaneous administration, the lowest dose of insulin (2 x 10(-6) U/kg) produced a significant acceleration in SIT without altering BG levels. However, the highest dose of insulin (2 U/kg) produced an acceleration of SIT that was associated with a significant fall in BG levels. 4. Following intracerebroventricular administration, the lowest dose of insulin (2 x 10(-6) U/kg) attenuated SIT, without producing any alteration in BG levels, but the highest dose (2 U/kg) mimicked the effects seen following subcutaneous administration. Peripherally administered insulin produced significant acceleration of SIT at lower doses (2 x 10(-6) or 2 x 10(-3) mU/kg) compared with centrally administered insulin at similar doses. However, at the highest dose of insulin (2 U/kg), both routes (s.c. and i.c.v.) produced acceleration of SIT. 5. In the present study, peripherally and centrally administered insulin at 2 x 10(-6) U/kg produced contrasting effects on SIT, without any hypoglycaemia. However, 2 U/kg insulin accelerated SIT similarly following both s.c. and i.c.v. administration that was associated with hypoglycaemia in healthy animals.

Ghrelin does not influence gastric emptying in obese subjects

OBJECTIVE

To evaluate the relationship between fasting plasma concentrations of ghrelin and gastric emptying in obese individuals compared with lean subjects.

RESEARCH METHODS AND PROCEDURES

We included 20 obese patients (9 men and 11 women, BMI > 30 kg/m2) and 16 nonobese control subjects (7 men and 9 women, BMI < or = 25 kg/m2). Gastric emptying of solids (egg sandwich labeled with radionuclide) was measured at 120 minutes with (99m)Tc-single photon emission computed tomography imaging. Ghrelin and leptin were analyzed by radioimmunoassay and ELISA methods, respectively.

RESULTS

The gastric half-emptying time was similar in obese men and women (67.8 +/- 14.79 vs. 66.6 +/- 13.56 minutes) but significantly shorter (p < 0.001) than in the control population (men: 88.09 +/- 11.72 minutes; women: 97.25 +/- 10.31 minutes). Ghrelin levels were significantly lower in obese subjects (131.37 +/- 47.67 vs. 306.3 +/- 45.52 pg/mL; p < 0.0001 in men and 162.13 +/- 32.95 vs. 272.8 +/- 47.77 pg/mL; p < 0.0001 in women). A negative correlation between gastric emptying and fasting ghrelin levels was observed only in lean subjects (y = -0.2391x + 157.9; R2 = 0.95). Also, in the lean group, ghrelin was the only significant independent determinant of gastric emptying, explaining 98% of the variance (adjusted R2) in a multiple regression analysis.

DISCUSSION

This report shows that, in humans, gastric emptying is faster in obese subjects than in lean controls and that, whereas ghrelin is the best determinant of gastric kinetics in healthy controls, this action is lost in obesity.

Changes in GI hormones and their effect on gastric emptying and transit times after Roux-en-Y gastric bypass in rat model

BACKGROUND

We determined whether Roux-en-Y gastric bypass (RYGB)-induced protracted weight loss is associated with an increase in anorectic peptide YY (PYY) and decreased gastrointestinal (GI) motility.

METHODS

RYGB and control sham-operated GI intact obese (SO Obese) and sham-operated GI intact pair-fed (PF) rats were studied. Postoperatively, body weight (BW) and food intake were measured for 90 days. Rats were killed to measure PYY, ghrelin, cholecystokinin (CCK), and glucagonlike peptide-1 (GLP-1). Ninety-day food intake trends were examined by quadratic trend analysis. On the basis of a 28-day weight loss rate, PYY also was measured at 14 and 28 days. Peak 28-day PYY results corresponded with peak BW loss rate; thus, gastric emptying (GE) and intestinal transit time were measured. Data were analyzed by analysis of variance and Tukey's pairwise multiple comparison.

RESULTS

At 90 days, BW in SO Obese versus PF versus RYGB rats was 801 +/- 15 g versus 661 +/- 24 g versus 538 +/- 32 g respectively (P < .05). Concentrations of plasma PYY were increased, while plasma ghrelin was decreased in RYGB versus SO Obese and PF (P < .05). CCK and GLP-1 were unchanged. In RYGB versus controls, PYY was increased at 14 and 28 days but was most elevated at 28 days. In RYGB versus controls, GE was delayed (P < .05) and intestinal transit time was longer (P < .05).

CONCLUSIONS

After RYGB, an increase in PYY and a decrease in ghrelin occurred, probably explaining the decrease in food intake, the slower GE and transit time, which contributed to weight loss. Longitudinal studies can be performed with the use of our RYGB model, providing insight into weight loss mechanisms by generating long-term follow-up data currently not available in human studies.

Peripheral mechanisms involved in gastric mucosal protection by intracerebroventricular and intraperitoneal nociceptin in rats

Nociceptin (N/OFQ) exerts multiple effects in the gastrointestinal tract after central or peripheral administration. In the present study, we examined the possible peripheral mechanisms mediating gastric protection by N/OFQ in rats. Gastric mucosal lesions were induced by 50% ethanol (1 ml/rat intragastrically). N/OFQ, administered either intracerebroventricularly (3 microg/rat) or ip (10 microg/kg), significantly reduced macroscopic and histological damage. The protective effect of intracerebroventricular N/OFQ was blocked by atropine, subdiaphragmatic vagotomy, and bretylium. The effect of both central and peripheral N/OFQ was blocked by functional ablation of afferent nerves produced by capsaicin, by the antagonist of calcitonin gene-related peptide, CGRP(8-37), and by the nitric oxide synthase inhibitor, N(G)-nitro-L-arginine methyl ester. These results indicate that N/OFQ increases gastric mucosal resistance to ethanol by operating both in the central nervous system and in the periphery. Vagal cholinergic and sympathetic pathways mediate the central activity of N/OFQ, whereas vagal nonmuscarinic pathways mediate the peripheral activity of the peptide. The neuronal circuit involving extrinsic sensory neurons, calcitonin gene-related peptide, and nitric oxide is activated by central as well as peripheral N/OFQ. The study provides evidence that N/OFQ contributes to neurally mediated gastric mucosal protection.