Ghrelin and Motilin Control Systems in GI Physiology and Therapeutics. Handb Exp Pharmacol. 2017;239:379-416. [PMID: 28035532 DOI: 10.1007/164_2016_104]

Common Pathophysiological Mechanisms and Treatment of Diabetic Gastroparesis

Diabetic gastroparesis (DGP) is a common complication of diabetes mellitus, marked by gastrointestinal motility disorder, a delayed gastric emptying present in the absence of mechanical obstruction. Clinical manifestations include postprandial fullness and epigastric discomfort, bloating, nausea, and vomiting. DGP may significantly affect the quality of life and productivity of patients. Research on the relationship between gastrointestinal dynamics and DGP has received much attention because of the increasing prevalence of DGP. Gastrointestinal motility disorders are closely related to a variety of factors including the absence and destruction of interstitial cells of Cajal, abnormalities in the neuro-endocrine system and hormone levels. Therefore, this study will review recent literature on the mechanisms of DGP and gastrointestinal motility disorders as well as the development of prokinetic treatment of gastrointestinal motility disorders in order to give future research directions and identify treatment strategies for DGP.

The Use of Pre-Endoscopic Metoclopramide Does Not Prevent the Need for Repeat Endoscopy: A U.S. Based Retrospective Cohort Study

BACKGROUND

Peptic ulcer disease (PUD) can cause upper gastrointestinal bleeding (UGIB), often needing esophagogastroduodenoscopy (EGD). Second-look endoscopies verify resolution, but cost concerns prompt research on metoclopramide's efficacy compared to erythromycin.

METHODS

We analyzed the Diamond Network of TriNetX Research database, dividing UGIB patients with PUD undergoing EGD into three groups: metoclopramide, erythromycin, and no medication. Using 1:1 propensity score matching, we compared repeat EGD, post-EGD transfusion, and mortality within one month in two study arms.

RESULTS

Out of 97,040 patients, 11.5% received metoclopramide, 3.9% received erythromycin, and 84.6% received no medication. Comparing metoclopramide to no medication showed no significant difference in repeat EGD (10.1% vs. 9.7%, p = 0.34), transfusion (0.78% vs. 0.86%, p = 0.5), or mortality (1.08% vs. 1.08%, p = 0.95). However, metoclopramide had a higher repeat EGD rate compared to erythromycin (9.4% vs. 7.5%, p = 0.003), with no significant difference in transfusion or mortality.

CONCLUSIONS

The need to repeat EGD was not decreased with pre-EGD use of metoclopramide. If a prokinetic agent is to be used prior to EGD, erythromycin shows superior reduction in the need of repeat EGD as compared to metoclopramide.

Analysis of influencing factors and construction of prediction model for postoperative nausea and vomiting in patients undergoing laparoscopic sleeve gastrectomy: a single-center retrospective cohort study

BACKGROUND

With the increasing number of bariatric surgeries, the high incidence of postoperative nausea and vomiting (PONV) associated with this surgery has also gradually attracted attention. Among the common bariatric surgery methods, patients undergoing sleeve gastrectomy (SG) have the highest incidence of nausea and vomiting. The mechanism of occurrence of PONV is very complex. This study aims to explore the influencing factors of PONV in patients undergoing laparoscopic sleeve gastrectomy (LSG) and construct a nomogram prediction model based on these factors.

METHODS

With the approval of the Ethics Committee, the electronic medical records of patients who underwent LSG from July 2022 to May 2023 were collected retrospectively.

RESULTS

A total of 114 patients with complete medical records who underwent LSG from July 2022 to May 2023 were included in this study. Among them, 46 patients developed PONV, resulting in a PONV incidence rate of 40.4%. Multivariate logistic regression analysis revealed that female gender, the use of inhalation anesthesia, and operation time ≥ 120 min were risk factors for PONV in LSG. Additionally, the use of more than two kinds of antiemetic drugs was identified as a protective factor. Based on these factors, a nomogram model was constructed.

CONCLUSION

PONV in patients undergoing LSG is related to gender, type of anesthesia, duration of surgery, and combination therapy with antiemetic drugs. The nomogram prediction model constructed in this study demonstrates high accuracy and discrimination in predicting the occurrence of PONV in patients undergoing LSG.

Alpinia officinarum Hance extract ameliorates diabetic gastroparesis by regulating SCF/c-kit signaling pathway and rebalancing gut microbiota

Diabetic gastroparesis (DGP) is a common complication of type 2 diabetes mellitus (T2DM). Alpinia officinarum Hance (AOH) is one of the most commonly used both as a food and folk medicines, which is rich in diarylheptanoids and flavonoids. The gastroprotection and hypoglycemic effect make AOH has great potential in developing of anti-DGP complementary medicine. However, the molecular mechanisms of AOH that act against DGP are yet to be elucidated. In this study, we evaluated the therapeutic effects, the potential molecular mechanism, and the changes of gut microbiota of AOH in DGP. The 5 components of the AOH were analyzed, and the potential signaling pathway of AOH improving DGP was predicted by molecular docking. Subsequently, DGP rat model was constructed using high-fat-irregular-diet, AOH intervention significantly reduced blood glucose levels, increased gastrointestinal propulsion rate, and improved gastric histological morphology in DGP rats. Meanwhile, AOH has been shown to regulate the SCF/c-kit signaling pathway and rebalance the gut microbiota, which may be closely related to its role in improving DGP. Taken together, AOH may play a protective role on DGP through multiple mechanisms, which might pave the road for development and utilization of AOH.

Review article: An analysis of the pharmacological rationale for selecting drugs to inhibit vomiting or increase gastric emptying during treatment of gastroparesis

BACKGROUND

Drugs which can inhibit nausea/vomiting and/or increase gastric emptying are used to treat gastroparesis, mostly 'off-label'. Within each category, they act at different targets and modulate different physiological mechanisms.

AIMS

Address the questions: In gastroparesis, why should blocking one pathway causing vomiting, be more appropriate than another? Why might increasing gastric emptying via one mechanism be more appropriate than another?

METHODS

Drugs used clinically were identified via consensus opinions and reviews, excluding the poorly characterised. Their pharmacology was defined, mapped to mechanisms influencing vomiting and gastric emptying, and rationale developed for therapeutic use.

RESULTS

Vomiting: Rationale for 5-HT₃ , D₂ , H₁ or muscarinic antagonists, and mirtazapine, amitriptyline, nortriptyline, are poor. Arguments for inhibiting central consequences of vagal afferent transmission by NK₁ antagonism are complicated by doubts over effects on nausea. Gastric emptying: Confusion emerges because of side-effects of drugs increasing gastric emptying: Metoclopramide (5-HT₄ agonist, D₂ and 5-HT₃ antagonist; also blocks some emetic stimuli and causes tardive dyskinesia) and Erythromycin (high-efficacy motilin agonist, requiring low doses to minimise side-effects). Limited trials with selective 5-HT₄ agonists indicate variable efficacy.

CONCLUSIONS

Several drug classes inhibiting vomiting have no scientific rationale. NK₁ antagonism has rationale but complicated by limited efficacy against nausea. Studies must resolve variable efficacy of selective 5-HT₄ agonists and apparent superiority over motilin agonists. Overall, lack of robust activity indicates a need for novel approaches targeting nausea (e.g., modulating gastric pacemaker or vagal activity, use of receptor agonists or new targets such as GDF15) and objective assessments of nausea.

Peripheral administration of neuropeptide W inhibits gastric emptying in rats: The role of small diameter afferent fibers and cholecystokinin receptors

Neuropeptide W (NPW), a novel hypothalamic peptide, contributes to the central regulation of food intake and energy balance, and suppresses feeding behavior when administered centrally. The aim of our study was to investigate the role of peripherally administered NPW in the modulation of gastric emptying, and to evaluate the participation of afferent fibers, cholecystokinin (CCK) receptors and gastric smooth muscle contractility in the regulatory effects of NPW on gastric motility. In Sprague-Dawley male rats equipped with gastric fistula, gastric emptying rate of the saline and peptone solutions was measured following subcutaneous administration of NPW (0.1 or 5 μg/kg) preceded by subcutaneous injections of saline, CCK-1 or CCK-2 receptor antagonists. Another group of rats with cannulas were injected subcutaneously with capsaicin for afferent denervation before commencing emptying trials. The effect of NPW on carbachol-induced gastric contractility and the role of CCK receptors in gastric smooth muscle contractility were also assessed in gastric strips. Peripheral injection of NPW delayed gastric emptying rate of both caloric and non-caloric liquid test meals, while administration of CCK-1 or CCK-2 receptor antagonists or denervation of small diameter afferents reversed NPW-induced delay in gastric emptying. Moreover, NPW inhibited antrum contractility in the organ bath. Our results revealed that peripherally administered NPW delayed liquid emptying from the stomach via the involvement of small diameter afferent neurons and CCK receptors, and thereby this regulatory role may contribute to its central regulatory role in controlling food intake and energy balance.

Electroceuticals for Neurogastroenterology and Motility Disorders

PURPOSE OF REVIEW

To provide an updated overview on use of electrostimulation in gastrointestinal motility disorders and obesity, with a focus on gastric electrical stimulation, vagal nerve stimulation and sacral nerve stimulation.

RECENT FINDINGS

Recent studies on gastric electrical stimulation for chronic vomiting showed a decrease in frequency of vomiting, but without significant improvement in quality of life. Percutaneous vagal nerve stimulation shows some promise for both symptoms of gastroparesis and IBS. Sacral nerve stimulation does not appear effective for constipation. Studies of electroceuticals for treatment of obesity have quite varied results with less clinical penetrance of the technology. Results of studies on the efficacy of electroceuticals have been variable depending on pathology but this area remains promising. Improved mechanistic understanding, technology and more controlled trials will be helpful to establish a clearer role for electrostimulation in treatment of various GI disorders.

Effect of omentopexy/gastropexy on gastrointestinal symptoms after laparoscopic sleeve gastrectomy: A meta-analysis of randomized controlled trials and systematic review

INTRODUCTION

The increased prevalence of obesity worldwide and low incidence of postoperative complications make the laparoscopic sleeve gastrectomy (LSG) a clear public choice for obese-related individuals. Pre-existing studies reported contentious outcomes regarding the association with gastrointestinal symptoms after adding omentopexy (Ome) or gastropexy (Gas) to LSG. The present meta-analysis attempted to evaluate the pros and cons of operating Ome/Gas after LSG concerning gastrointestinal symptoms.

METHODS

The data extraction and study quality assessment were independently performed by two individuals. The PubMed, EMBASE, Scopus, and Cochrane Library databases were systematically searched up to October 1, 2022, using the keywords LSG, omentopexy, and gastropexy to identify randomized controlled trial studies.

RESULTS

Of the original 157 records, 13 studies with 3515 patients were included. LSG with Ome/Gas excels the LSG group in nausea (odds ratio [OR] = 0.57; 95% CI[0.46, 0.70]; P < .00001), reflux (OR = 0.57; 95% CI [0.46, 0.70]; P < .00001), vomiting (OR = 0.41; 95% CI [0.25, 0.67]; P = .0004) on gastrointestinal symptoms and bleeding (OR = 0.36; 95% CI [0.22, 0.59]; P < .0001), leakage (OR = 0.19; 95% CI [0.09, 0.43]; P < .0001), gastric torsion (OR = 0.23; 95% CI [0.07, 0.75]; P = .01) on post-LSG complications. Further, LSG with Ome/Gas was superior to LSG regarding the result of excess body mass index loss in 1 year after surgery (mean difference = 1.83; 95% CI [0.59, 3.07]; P = .004). However, no significant associations were shown between groups in wound infection and the resulting weight or body mass index 1 year after surgery. Of note, subgroup analysis indicated that gastroesophageal reflux disease can be alleviated by adding Ome/Gas post-LSG in those who used small bougies from 32 to 36 Fr (OR = 0.24; 95% CI [0.17, 0.34]; P < .00001) in contrast with large bougies over 36 Fr.

CONCLUSION

Most results elucidated the impact of adding Ome/Gas after LSG in reducing the incidence of gastrointestinal symptoms. Additionally, more studies should be conducted to find the relations between other indicators in the present analysis due to the poor cases.

Animal studies reveal that the ghrelin pathway regulates alcohol-mediated responses

Alcohol use disorder (AUD) is often described as repeated phases of binge drinking, compulsive alcohol-taking, craving for alcohol during withdrawal, and drinking with an aim to a reduce the negative consequences. Although multifaceted, alcohol-induced reward is one aspect influencing the former three of these. The neurobiological mechanisms regulating AUD processes are complex and one of these systems is the gut-brain peptide ghrelin. The vast physiological properties of ghrelin are mediated via growth hormone secretagogue receptor (GHSR, ghrelin receptor). Ghrelin is well known for its ability to control feeding, hunger, and metabolism. Moreover, ghrelin signaling appears central for alcohol-mediated responses; findings reviewed herein. In male rodents GHSR antagonism reduces alcohol consumption, prevents relapse drinking, and attenuates the motivation to consume alcohol. On the other hand, ghrelin increases the consumption of alcohol. This ghrelin-alcohol interaction is also verified to some extent in humans with high alcohol consumption. In addition, either pharmacological or genetic suppression of GHSR decreases several alcohol-related effects (behavioral or neurochemical). Indeed, this suppression blocks the alcohol-induced hyperlocomotion and dopamine release in nucleus accumbens as well as ablates the alcohol reward in the conditioned place preference model. Although not fully elucidated, this interaction appears to involve areas central for reward, such as the ventral tegmental area (VTA) and brain nodes targeted by VTA projections. As reviewed briefly, the ghrelin pathway does not only modulate alcohol-mediated effects, it regulates reward-related behaviors induced by addictive drugs. Although personality traits like impulsivity and risk-taking behaviors are common in patients with AUD, the role of the ghrelin pathway thereof is unknown and remains to be studied. In summary, the ghrelin pathway regulates addiction processes like AUD and therefore the possibility that GHSR antagonism reduces alcohol or drug-taking should be explored in randomized clinical trials.

Role of the Ghrelin System in Colorectal Cancer

The ghrelin system contains several components (e.g., ghrelin with growing number of alternative peptides, growth hormone secretagogue receptors (GHS-Rs), and ghrelin-O-acyl-transferase (GOAT) and participates in regulation of a number of key processes of gastrointestinal (GI) tract cancer progression, including cell proliferation, migration, invasion, apoptosis, inflammation, and angiogenesis. However, its exact role in promoting or inhibiting cancer progression is still unclear. Colorectal cancer (CRC) is one of the most common human malignancies worldwide. Molecular studies suggest an autocrine/paracrine mechanism for the secretion of ghrelin in colorectal carcinogenesis and its contribution to its initial stages. However, the signalling pathways of CRC development involving the ghrelin system are poorly understood. Potential mechanisms of colon carcinogenesis involving components of the ghrelin system were previously described in an animal model and in in vitro studies. However, the diagnostic–prognostic role of serum ghrelin concentrations, tissue expression, or genetic changes of this system in various stages of CRC progression remains an open case. Thus, the aim of this study is to discuss the role of the ghrelin system in colon carcinogenesis, diagnostics and CRC prognostics, as well as the results of studies on the use of ghrelin and its analogues in the therapy of CRC-related syndromes (e.g., cachexia and sarcopenia).

The controversial role of the vagus nerve in mediating ghrelin´s actions: gut feelings and beyond

Ghrelin is a stomach-derived peptide hormone that acts via the growth hormone secretagogue receptor (GHSR) and displays a plethora of neuroendocrine, metabolic, autonomic and behavioral actions. It has been proposed that some actions of ghrelin are exerted via the vagus nerve, which provides a bidirectional communication between the central nervous system and peripheral systems. The vagus nerve comprises sensory fibers, which originate from neurons of the nodose and jugular ganglia, and motor fibers, which originate from neurons of the medulla. Many anatomical studies have mapped GHSR expression in vagal sensory or motor neurons. Also, numerous functional studies investigated the role of the vagus nerve mediating specific actions of ghrelin. Here, we critically review the topic and discuss the available evidence supporting, or not, a role for the vagus nerve mediating some specific actions of ghrelin. We conclude that studies using rats have provided the most congruent evidence indicating that the vagus nerve mediates some actions of ghrelin on the digestive and cardiovascular systems, whereas studies in mice resulted in conflicting observations. Even considering exclusively studies performed in rats, the putative role of the vagus nerve in mediating the orexigenic and growth hormone (GH) secretagogue properties of ghrelin remains debated. In humans, studies are still insufficient to draw definitive conclusions regarding the role of the vagus nerve mediating most of the actions of ghrelin. Thus, the extent to which the vagus nerve mediates ghrelin actions, particularly in humans, is still uncertain and likely one of the most intriguing unsolved aspects of the field.

Insight into the role of the gut-brain axis in alcohol-related responses: Emphasis on GLP-1, amylin, and ghrelin

Alcohol use disorder (AUD) contributes substantially to global morbidity and mortality. Given the heterogenicity of this brain disease, available pharmacological treatments only display efficacy in sub-set of individuals. The need for additional treatment options is thus substantial and is the goal of preclinical studies unraveling neurobiological mechanisms underlying AUD. Although these neurobiological processes are complex and numerous, one system gaining recent attention is the gut-brain axis. Peptides of the gut-brain axis include anorexigenic peptide like glucagon-like peptide-1 (GLP-1) and amylin as well as the orexigenic peptide ghrelin. In animal models, agonists of the GLP-1 or amylin receptor and ghrelin receptor (GHSR) antagonists reduce alcohol drinking, relapse drinking, and alcohol-seeking. Moreover, these three gut-brain peptides modulate alcohol-related responses (behavioral and neurochemical) in rodents, suggesting that the alcohol reduction may involve a suppression of alcohol's rewarding properties. Brain areas participating in the ability of these gut-brain peptides to reduce alcohol-mediated behaviors/neurochemistry involve those important for reward. Human studies support these preclinical studies as polymorphisms of the genes encoding for GLP-1 receptor or the ghrelin pathway are associated with AUD. Moreover, a GLP-1 receptor agonist decreases alcohol drinking in overweight patients with AUD and an inverse GHSR agonist reduces alcohol craving. Although preclinical and clinical studies reveal an interaction between the gut-brain axis and AUD, additional studies should explore this in more detail.

Diabetic Gastroenteropathy: Soothe the Symptoms or Unravel a Cure?

Autonomic neuropathy in patients with diabetes mellitus, and especially complications related to gastrointestinal neuropathy, are often overlooked in the clinic. Diabetic gastroenteropathy affects every segment of the gastrointestinal tract and generates symptoms that may include nausea, early satiety, vomiting, abdominal pain, constipation, and diarrhea. Severe cases can be complicated by weight loss, dehydration, and electrolyte disturbances. The pathophysiology is complex, the diagnostics and treatment options are multidisciplinary, and there is generally a lack of evidence for the treatment options. The aims for this review are first to summarize the pathophysiology and describe possible and expected symptoms and complications.Further, we will try to supply the clinician with a straightforward tool for diagnostics, and then, we shall summarize established treatment options, including diet recommendations, pharmacological and non-pharmacological options. Finally, we will explore the multiple possibilities of novel treatment, looking at medications related to the pathophysiology of neuropathy, other manifestations of autonomic neuropathies, and symptomatic treatment for other gastrointestinal disorders, also including new knowledge of endosurgical and neuromodulatory treatment. The overall goal is to increase awareness and knowledge on this frequent diabetic complication and to provide better tools for diagnosis and treatment. Ultimately, we hope to encourage further research in this field, as there are clear shortcomings in terms of biomarkers, pathophysiology, as well as treatment possibilities. In conclusion, diagnosis and management of diabetic gastroenteropathy are challenging and often require multidisciplinary teams and multimodal therapies. Treatment options are sparse, but new pharmacological, endoscopic, and neuromodulatory techniques have shown promising results in initial studies.

The brain-penetrating, orally bioavailable, ghrelin receptor agonist HM01 ameliorates motion-induced emesis in Suncus murinus (house musk shrew)

BACKGROUND AND PURPOSE

HM01, a novel, orally bioavailable, brain-penetrating agonist of ghrelin receptors, ameliorates emesis in Suncus murinus. This study compared HM01's activity against motion sickness with that of the less brain-penetrating ghrelin receptor agonist, HM02.

EXPERIMENTAL APPROACH

The potential of HM01 and HM02 to relax isolated mesenteric arteries and to increase feeding was investigated. Radio telemetry was used to record gastric slow waves and body temperature. Plethysmography was used to measure respiratory function. HM01 and HM02 were administered p.o. 1 hr prior to provocative motion, and c-Fos expression in brain sections was assessed.

KEY RESULTS

HM01 and HM02 both relaxed precontracted arteries, yielding EC₅₀ values of 2.5 ± 0.5 and 3.5 ± 0.4 nM respectively. HM01 increased feeding, but HM02 did not. Both compounds caused hypothermia and bradygastria. Motion induced 123 ± 24 emetic events. HM01, but not HM02, reduced motion-induced emesis by 67.6%. Motion increased c-Fos expression in the nucleus tractus solitarius (NTS), dorsal motor nucleus of the vagus (DMNV), medial vestibular nucleus (MVe), central nucleus of the amygdala, and paraventricular hypothalamic nucleus (PVH). HM01 alone increased c-Fos expression in the area postrema, NTS, DMNV, PVH, and arcuate hypothalamic nucleus; HM02 had a similar pattern except it did not increase c-Fos in the PVH. Both compounds antagonized the motion-induced increases in c-Fos expression in the MVe.

CONCLUSIONS AND IMPLICATIONS

HM01 is more effective than HM02 in preventing motion-induced emesis. The difference in potency may relate to activation of ghrelin receptors in the PVH.

Advances in the physiology of gastric emptying

There have been many recent advances in the understanding of various aspects of the physiology of gastric motility and gastric emptying. Earlier studies had discovered the remarkable ability of the stomach to regulate the timing and rate of emptying of ingested food constituents and the underlying motor activity. Recent studies have shown that two parallel neural circuits, the gastric inhibitory vagal motor circuit (GIVMC) and the gastric excitatory vagal motor circuit (GEVMC), mediate gastric inhibition and excitation and therefore the rate of gastric emptying. The GIVMC includes preganglionic cholinergic neurons in the DMV and the postganglionic inhibitory neurons in the myenteric plexus that act by releasing nitric oxide, ATP, and peptide VIP. The GEVMC includes distinct gastric excitatory preganglionic cholinergic neurons in the DMV and postganglionic excitatory cholinergic neurons in the myenteric plexus. Smooth muscle is the final target of these circuits. The role of the intramuscular interstitial cells of Cajal in neuromuscular transmission remains debatable. The two motor circuits are differentially regulated by different sets of neurons in the NTS and vagal afferents. In the digestive period, many hormones including cholecystokinin and GLP-1 inhibit gastric emptying via the GIVMC, and in the inter-digestive period, hormones ghrelin and motilin hasten gastric emptying by stimulating the GEVMC. The GIVMC and GEVMC are also connected to anorexigenic and orexigenic neural pathways, respectively. Identification of the control circuits of gastric emptying may provide better delineation of the pathophysiology of abnormal gastric emptying and its relationship to satiety signals and food intake.

Motilin: from gastric motility stimulation to hunger signalling

After the discovery of motilin in 1972, motilin and the motilin receptor were studied intensely for their role in the control of gastrointestinal motility and as targets for treating hypomotility disorders. The genetic revolution - with the use of knockout models - sparked novel insights into the role of multiple peptides but contributed to a decline in interest in motilin, as this peptide and its receptor exist only as pseudogenes in rodents. The past 5 years have seen a major surge in interest in motilin, as a series of studies have shown its relevance in the control of hunger and regulation of food intake in humans in both health and disease. Luminal stimuli, such as bitter tastants, have been identified as modulators of motilin release, with effects on hunger and food intake. The current state of knowledge and potential implications for therapy are summarized in this Review.

Contribution of ghrelin to functional gastrointestinal disorders’ pathogenesis

Functional gastrointestinal disorders (FGID) are heterogeneous disorders with a variety of clinical manifestations, primarily defined by signs and symptoms rather than a definite underlying cause. Their pathophysiology remains obscure and, although it is expected to differ according to the specific FGID, disruptions in the brain-gut axis are now thought to be a common denominator in their pathogenesis. The hormone ghrelin is an important component of this axis, exerting a wide repertoire of physiological actions, including regulation of gastrointestinal motility and protection of mucosal tissue. Ghrelin’s gene shows genetic polymorphism, while its protein product undergoes complex regulation and metabolism in the human body. Numerous studies have studied ghrelin’s relation to the emergence of FGIDs, its potential value as an index of disease severity and as a predictive marker for symptom relief during attempted treatment. Despite the mixed results currently available in scientific literature, the plethora of statistically significant findings shows that disruptions in ghrelin genetics and expression are plausibly related to FGID pathogenesis. The aim of this paper is to review current literature studying these associations, in an effort to uncover certain patterns of alterations in both genetics and expression, which could delineate its true contribution to FGID emergence, either as a causative agent or as a pathogenetic intermediate.

Bioelectric neuromodulation for gastrointestinal disorders: effectiveness and mechanisms

The gastrointestinal tract has extensive, surgically accessible nerve connections with the central nervous system. This provides the opportunity to exploit rapidly advancing methods of nerve stimulation to treat gastrointestinal disorders. Bioelectric neuromodulation technology has considerably advanced in the past decade, but sacral nerve stimulation for faecal incontinence currently remains the only neuromodulation protocol in general use for a gastrointestinal disorder. Treatment of other conditions, such as IBD, obesity, nausea and gastroparesis, has had variable success. That nerves modulate inflammation in the intestine is well established, but the anti-inflammatory effects of vagal nerve stimulation have only recently been discovered, and positive effects of this approach were seen in only some patients with Crohn's disease in a single trial. Pulses of high-frequency current applied to the vagus nerve have been used to block signalling from the stomach to the brain to reduce appetite with variable outcomes. Bioelectric neuromodulation has also been investigated for postoperative ileus, gastroparesis symptoms and constipation in animal models and some clinical trials. The clinical success of this bioelectric neuromodulation therapy might be enhanced through better knowledge of the targeted nerve pathways and their physiological and pathophysiological roles, optimizing stimulation protocols and determining which patients benefit most from this therapy.

GASTROINTESTINAL MOTILITY DISORDERS IN OBESITY

The gastrointestinal (GI) motility, which is important for the digestion and absorption, may be altered in obesity. The aim of this review is to present the GI motility changes occurring in obesity, as well as their underlying mechanisms. We have conducted a systematic review of the published literature concerning GI motility and obesity and have described recent published data on the changes throughout the entire GI tract. Most recent discoveries include evidence supporting the increase of gastroesophageal reflux disease in obesity and inhibition of gastric motility. Intestinal transit of the distal small bowel generally slows down, ensuring enough time for digestion and absorption. Constipation is more frequent in obese patients than in those with a normal weight. The gut-brain axis plays an important role in the pathophysiology of GI motility disorders in obesity. This bidirectional communication is achieved by way of neurons, hormones, metabolites derived from intestinal microbiota and cytokines. The molecular mechanisms of GI motility changes in obesity are complex. Current data offer a starting point for further research needed to clarify the association of obesity with GI motility disorders.

Gastric Emptying Impacts the Timing of Meal Glucose Peak in Subjects With Uncomplicated Type 1 Diabetes

CONTEXT

Diabetes mellitus is associated with gastrointestinal (GI) motility dysfunction, ranging from delayed to accelerated gastric emptying (GE).

OBJECTIVE

To evaluate GE in patients with type 1 diabetes mellitus (T1DM) without chronic complications and to investigate its relation with postprandial glucose and GI hormone responses.

DESIGN

Cross-sectional study.

SETTING/PARTICIPANTS

Forty-two patients with T1DM free of chronic complications referred to Federico II University and 31 healthy controls similar for age, sex, and body mass index.

INTERVENTIONS/MAIN OUTCOME MEASURES

GE was assessed by using the 13C-octanoate breath test with a standardized solid meal. During the meal, plasma glucose, ghrelin, and glucagon-like peptide 1 (GLP-1) responses were assessed, and GI symptoms were evaluated by a specific questionnaire.

RESULTS

Patients with T1DM showed a significantly slower GE half-emptying time (GE t1/2) (113 ± 34 minutes) than did controls (89 ± 17 minutes; P < 0.001). Thirty-six percent of T1DM showed a delayed GE (t1/2 > 120 minutes), whereas all controls showed a normal GE. When patients with T1DM were stratified according to GE t1/2, postmeal glucose response was significantly different between those with delayed and those with normal GE (P = 0.013). In particular, patients with T1DM and delayed GE showed a significantly longer mean time to peak glucose than did patients with normal GE (P = 0.004). In addition, GE t1/2 was an independent predictor of the time to peak glucose (β = 0.329; P = 0.025). GLP-1 and ghrelin responses to the test meal, as well as the prevalence of GI symptoms, were similar between patients with T1DM and controls and between patients with T1DM with normal GE and those with delayed GE.

CONCLUSIONS

Delayed GE time is associated with a longer time to peak glucose. GE evaluation could be useful for individualizing the timing of preprandial insulin bolus in patients with T1DM.