Abnormal ghrelin and pancreatic polypeptide responses in gastroparesis

Early Gastrointestinal Neuropathy Assessed by Wireless Motility Capsules in Adolescents with Type 1 Diabetes

BACKGROUND

To assess the prevalence of objective signs of gastrointestinal (GI) autonomic neuropathy (AN) in adolescents with type 1 diabetes (T1D). In addition, to investigate associations between objective GI findings and self-reported symptoms or other findings of AN.

METHODS

Fifty adolescents with T1D and 20 healthy adolescents were examined with a wireless motility capsule to assess the total and regional GI transit times and motility index. GI symptoms were evaluated with the GI Symptom Rating Scale questionnaire. AN was evaluated with cardiovascular and quantitative sudomotor axon reflex tests.

RESULTS

There was no difference in GI transit times in adolescents with T1D and healthy controls. Adolescents with T1D had a higher colonic motility index and peak pressure than the controls, and GI symptoms were associated with low gastric and colonic motility index (all p < 0.05). Abnormal gastric motility was associated with the duration of T1D, while a low colonic motility index was inversely associated with "time in target range" for blood glucose (all p < 0.01). No associations were found between signs of GI neuropathy and other measures of AN.

CONCLUSIONS

Objective signs of GI neuropathy are common in adolescents with T1D and it seems to require early interventions in patients at high risk of developing GI neuropathy.

A cross-sectional study describing peripheral neuropathy in patients with symptoms of gastroparesis: associations with etiology, gastrointestinal symptoms, and gastric emptying

Background

Peripheral neuropathy (PN) is present in diabetic gastroparesis but is not described in idiopathic gastroparesis.

Aims

(1) Determine prevalence of PN in idiopathic gastroparesis; (2) assess if patients with symptoms of gastroparesis and PN differ in gastric emptying and symptoms, both gastrointestinal and psychosocial, from patients without PN (nPN); (3) compare this relationship to that in other etiological groups.

Methods

250 patients with symptoms of gastroparesis underwent gastric emptying scintigraphy and answered questionnaires including severity of gastroparesis symptoms using the Gastroparesis Cardinal Symptom Index (GCSI) and presence of peripheral neuropathy using the Neuropathy Total Symptom Score-6 (NTSS-6).

Results

PN, defined by NTSS-6 > 6, was present in 70/250 (28%) patients: 22/148 (15%) idiopathic, 33/61 (54%) diabetic, and 11/32 (34%) postsurgical (p < 0.01). Among 148 patients with symptoms of idiopathic gastroparesis, defined as non-diabetic, non-postsurgical, and not caused by a known disorder such as Parkinson’s or connective tissue disease, symptoms of gastroparesis were more severe in PN than nPN: bloating (4.05 ± 1.17 vs. 2.99 ± 1.61, p < 0.01), abdominal distension (3.86 ± 1.49 vs. 2.45 ± 1.68, p < 0.01), and upper abdominal pain (3.64 ± 1.22 vs. 2.71 ± 1.78, p = 0.03). Ninety-nine idiopathic patients underwent gastric emptying scintigraphy: 7/43 (16%) patients with delayed gastric emptying and 9/56 (16%) patients with normal gastric emptying had PN. Among patients with idiopathic gastroparesis, abdominal distension (4.43 ± 0.53 vs. 2.89 ± 1.68, p = 0.01) was more severe in PN than nPN. The association of PN and worse gastrointestinal symptoms was not as apparent in patients with symptoms of diabetic or postsurgical gastroparesis.

Conclusions

PN was present in 70/250 (28%) of patients with symptoms of gastroparesis and was present to a lesser extent in idiopathic than diabetic gastroparesis. The presence of PN in IG was associated with more severe gastroparetic symptoms than in nPN. Screening for PN may help identify a gastroparesis cohort with peripheral neuropathy who are more symptomatic.

Effects and Components of Herb Pair Huanglian-Banxia on Diabetic Gastroparesis by Network Pharmacology

Diabetic gastroparesis (DGP) is a serious and chronic complication of long-standing diabetes mellitus, which brings a heavy burden to individuals and society. Traditional Chinese medicine (TCM) is considered a complementary and alternative therapy for DGP patients. Huanglian (Coptidis Rhizoma, HL) and Banxia (Pinelliae Rhizoma, BX) combined as herb pair have been frequently used in TCM prescriptions, which can effectively treat DGP in China. In this article, a practical application of TCM network pharmacological approach was used for the research on herb pair HL-BX in the treatment of DGP. Firstly, twenty-seven potential active components of HL-BX were screened from the TCMSP database, and their potential targets were also retrieved. Then, the compound-target network and PPI network were constructed from predicted common targets, and several key targets were found based on the degree of the network. Next, GO and KEGG enrichment analyses were conducted to obtain several significantly enriched terms. Finally, the experimental verification was made. The results demonstrated that network pharmacological approach was a powerful means for identifying bioactive ingredients and mechanisms of action for TCM. Network pharmacology provided an effective strategy for TCM modern research.

Diabetic gastroparesis: An overview of pathogenesis, clinical presentation and novel therapies, with a focus on ghrelin receptor agonists

Diabetic gastroparesis is defined as delayed gastric emptying without mechanical obstruction in the setting of diabetes. Symptoms range from mild bloating to severe vomiting episodes and can result in frequent hospitalizations and poor quality of life. It is suspected that diabetic gastroparesis is underdiagnosed due to its similar presentation to other conditions such as gastroesophageal reflux disease. The pathogenesis of diabetic gastroparesis remains unclear, but proposed mechanisms include vagal dysfunction, hyperglycemia, interstitial cells of Cajal network disturbances, loss of neural nitric oxide synthase expression in the myenteric plexus, and oxidative stress. Current management for diabetic gastroparesis focuses on dietary and lifestyle changes as well as improved glycemic control. Limited options for medical therapies are available that include prokinetic and antiemetic medications. Metoclopramide is the only FDA-approved medication for the treatment of gastroparesis. Metoclopramide improves symptoms of gastroparesis although extended treatment presents challenges such as decreased efficacy over time and increased risks for adverse events. We summarize the current knowledge of the pathophysiology of diabetic gastroparesis and review current and investigational treatments for diabetes gastroparesis.

The Role of GI Peptides in Functional Dyspepsia and Gastroparesis: A Systematic Review

Functional dyspepsia (FD) and gastroparesis (GP) are common disorders of the upper gastrointestinal tract. The pathophysiology of these conditions is likely to be heterogenous, and factors such as altered motility, sensitivity and response to nutrition have been identified as putative underlying mechanisms. Motility, sensitivity as well as responses to nutrition can be influenced or mediated by peptide hormones and serotonin released from the gastrointestinal mucosa. This review summarizes the role of GI peptides in functional dyspepsia and gastroparesis. In most studies, the levels of somatostatin, ghrelin, and motilin did not differ between healthy volunteers and FD or GP patients, but higher symptom burden was often correlated with higher peptide levels. Ghrelin and motilin receptor agonists showed promising results in improvement of the gastric emptying, but the link with improvement of symptoms is less predictable. Serotonin agonists have a potential to improve symptoms in both FD and idiopathic gastroparesis. Drugs acting on the GLP-1 and on the PYY receptors deserve further investigation. There is a need for systematic large scale studies.

Utility of the plasma pancreatic polypeptide response to modified sham feeding in diabetic gastroenteropathy and non-ulcer dyspepsia

BACKGROUND

The relationship between cardiovascular and gastrointestinal (ie, plasma pancreatic polypeptide [PP] response to modified sham feeding [MSF]) indices of vagal function is unclear. Hyperglycemia inhibits PP secretion via vagally mediated mechanisms. Our aims were to (a) compare the PP response, (b) its relationship with glycemia, and (c) the relationship between PP response to MSF, gastric emptying (GE) of solids, and symptoms during GE study in healthy controls, patients with diabetic gastroenteropathy (DM), and non-ulcer dyspepsia (NUD).

METHODS

In 24 healthy controls, 40 DM, and 40 NUD patients, we measured plasma PP concentrations during MSF, cardiovagal functions, GE, and symptoms during a GE study.

KEY RESULTS

Baseline PP concentrations were higher in DM than in controls and NUD (P = .01), and in type 2 than in type 1 DM patients (P < .01). The PP increment during MSF was normal (≥20 pg/mL) in 70% of controls, 54% of DM, and 47% of NUD patients. Overall, the PP response and cardiovagal tests were concordant (P = .01). Among patients with a reduced PP increment with MSF, 7/10 of T1DM and 1/7 of T2DM patients had moderate or severe cardiovagal dysfunctions (P < .05). The PP response to MSF was not associated with GE.

CONCLUSIONS & INFERENCES

Up to 30% of healthy controls have a reduced PP increment during MSF, limiting the utility of this test to detect vagal injury. The PP response is more useful when it is normal than abnormal. A reduced PP response is more likely to be associated with cardiovagal dysfunctions in T1DM than in T2DM.

Delayed Gastric Emptying Associates With Diabetic Complications in Diabetic Patients With Symptoms of Gastroparesis

OBJECTIVES

Diabetic gastroparesis (Gp) occurs more often in type 1 diabetes mellitus (T1DM) than in type 2 diabetes mellitus (T2DM). Other diabetic end-organ complications include peripheral neuropathy, nephropathy, and retinopathy (together termed triopathy). This study determines the prevalence of diabetic complications (retinopathy, nephropathy, and peripheral neuropathy) in diabetic patients with symptoms of Gp, assessing the differences between T1DM and T2DM and delayed and normal gastric emptying (GE).

METHODS

Diabetic patients with symptoms of Gp underwent history and physical examination, GE scintigraphy, electrogastrography with water load, autonomic function testing, and questionnaires assessing symptoms and peripheral neuropathy.

RESULTS

One hundred thirty-three diabetic patients with symptoms of Gp were studied: 59 with T1DM and 74 with T2DM and 103 with delayed GE and 30 without delayed GE. The presence of retinopathy (37% vs 24%; P = 0.13), nephropathy (19% vs 11%; P = 0.22), and peripheral neuropathy (53% vs 39%; P = 0.16) was not significantly higher in T1DM than in T2DM; however, triopathies (all 3 complications together) were seen in 10% of T1DM and 3% of T2DM (P = 0.04). Diabetic patients with delayed GE had increased prevalence of retinopathy (36% vs 10%; P = 0.006) and number of diabetic complications (1.0 vs 0.5; P = 0.009); however, 39% of diabetic patients with delayed GE did not have any diabetic complications.

DISCUSSION

In diabetic patients with symptoms of Gp, delayed GE was associated with the presence of retinopathy and the total number of diabetic complications. Only 10% of patients with T1DM and 3% of those with T2DM had triopathy of complications, and 39% of diabetic patients with Gp did not have any diabetic complications. Thus, the presence of diabetic complications should raise awareness for Gp in either T1DM or T2DM; however, diabetic Gp frequently occurs without other diabetic complications.

Pathophysiology of idiopathic gastroparesis and implications for therapy

OBJECTIVES

Idiopathic gastroparesis is a gastric motility disorder characterized by chronic upper gastrointestinal symptoms and delayed gastric emptying without an identifiable underlying condition. This review summarizes recent understanding of the pathophysiology and treatment of idiopathic gastroparesis.

MATERIALS AND METHODS

Structured literature search in the PubMed, Embase and ClinicalTrials.gov databases.

RESULTS

Idiopathic gastroparesis involves several alterations in gastric motility and sensation, including delayed gastric emptying, altered myoelectrical activity, impaired fundic accommodation, visceral hypersensitivity and disturbances in antropyloroduodenal motility and coordination. Multiple cellular changes have been identified, including depletion of interstitial cells of Cajal (ICC) and enteric nerves, as well as stromal fibrosis. The underlying cause of these changes is not fully understood but may be an immune imbalance, including loss of anti-inflammatory heme-oxygenase-1 positive (HO-1) macrophages. There is currently no causal therapy for idiopathic gastroparesis. The treatment ladder consists of dietary measures, prokinetic and antiemetic medications, and varying surgical or endoscopic interventions, including promising pyloric therapies. There are ongoing trials with several novel medications, raising hopes for future treatment.

CONCLUSIONS

Patients with idiopathic gastroparesis present several pathophysiological alterations in the stomach, where depletion of ICC is of special importance. Treatment is currently focused on alleviating symptoms through dietary adjustments, medication or surgical or endoscopic interventions.

Ghrelin secretion in humans - a role for the vagus nerve?

BACKGROUND

Ghrelin, an orexigenic peptide, is secreted from endocrine cells in the gastric mucosa. Circulating levels rise in the preprandial phase, suggesting an anticipatory or cephalic phase of release, and decline in the postprandial phase, suggesting either the loss of a stimulatory factor or inhibition by factors released when nutrients enter the intestine. We hypothesized that vagal signals are not required for the (i) preprandial increase or (ii) postprandial suppression of ghrelin levels. Further, we wanted to investigate the hypothesis that (iii) glucagon-like peptide-1 might be implicated in the postprandial decline in ghrelin levels.

METHODS

We measured ghrelin levels in plasma from sham-feeding and meal studies carried out in vagotomized individuals and controls, and from a GLP-1 infusion study carried out in fasting healthy young individuals.

KEY RESULTS

We find that (i) ghrelin secretion is unchanged during indirect vagal stimulation as elicited by modified sham-feeding in vagotomized individuals and matched controls, (ii) ghrelin secretion is similarly suppressed after meal ingestion in vagotomized individuals and controls, and (iii) infusion of GLP-1 does not lower ghrelin levels.

CONCLUSIONS & INFERENCES

We conclude that for postprandial suppression of circulating ghrelin levels, a circulating factor (but not GLP-1) or short (duodeno-gastric) reflexes seem to be implicated.

Chronic nausea and vomiting: evaluation and treatment

Nausea is an uneasy feeling in the stomach while vomiting refers to the forceful expulsion of gastric contents. Chronic nausea and vomiting represent a diverse array of disorders defined by 4 weeks or more of symptoms. Chronic nausea and vomiting result from a variety of pathophysiological processes, involving gastrointestinal and non-gastrointestinal causes. The prevalence of chronic nausea and vomiting is unclear, although the epidemiology of specific conditions, such as gastroparesis and cyclic vomiting syndrome, is better understood. The economic impact of chronic nausea and vomiting and effects on quality of life are substantial. The initial diagnostic evaluation involves distinguishing gastrointestinal causes of chronic nausea and vomiting (e.g., gastroparesis, cyclic vomiting syndrome) from non-gastrointestinal causes (e.g., medications, vestibular, and neurologic disorders). After excluding anatomic, mechanical and biochemical causes of chronic nausea and vomiting, gastrointestinal causes can be grouped into two broad categories based on the finding of delayed, or normal, gastric emptying. Non-gastrointestinal disorders can also cause chronic nausea and vomiting. As a validated treatment algorithm for chronic nausea and vomiting does not exist, treatment should be based on a thoughtful discussion of benefits, side effects, and costs. The objective of this monograph is to review the evaluation and treatment of patients with chronic nausea and vomiting, emphasizing common gastrointestinal causes.

Small bowel fed response as measured by wireless motility capsule: Comparative analysis in healthy, gastroparetic, and constipated subjects

BACKGROUND

Small bowel fed response is an increased contractile activity pattern following the ingestion of a meal. Postprandial motility is traditionally evaluated using small bowel manometry. Wireless motility capsule (WMC) is an ingestible wireless capsule that measures pH, temperature, and intraluminal pressure. The primary aim of the study was to assess small bowel fed response captured with the non-invasive WMC. The secondary aim was to compare the fed response patterns between healthy subjects and patients with motility disorders of gastroparesis and constipation.

METHODS

All subjects had 250 cc Ensure^® meal 6 hours after WMC ingestion. Frequency of contractions (Ct), area under the curve (AUC), and motility index (MI) were analyzed during 30 minutes of pre-prandial baseline and 60 minutes postprandially in 20-minute windows.

KEY RESULTS

One hundred and eighty-eight subjects (107 healthy, 23 gastroparetics, 58 constipated) were analyzed. Healthy: Ct, AUC, and MI all increased significantly immediately after meal ingestion (P < .01). Motility parameters peak at 20-40 minutes postmeal. The motor activity decreased at the end of postprandial hour, but was still significantly higher than the fasting baseline (P < .01). Gastroparetics: All motility parameters failed to increase significantly compared to the baseline throughout the entire postprandial hour. Constipated: The fed response was similar to healthy subjects.

CONCLUSIONS AND INFERENCES

The small bowel fed response was readily observed in healthy and chronic constipation subjects with WMC but is blunted in gastroparetics. A blunted small bowel fed response suggests neuropathic changes outside the stomach and may contribute to postprandial symptoms.

Relating gastric scintigraphy and symptoms to motility capsule transit and pressure findings in suspected gastroparesis

BACKGROUND

Wireless motility capsule (WMC) findings are incompletely defined in suspected gastroparesis. We aimed to characterize regional WMC transit and contractility in relation to scintigraphy, etiology, and symptoms in patients undergoing gastric emptying testing.

METHODS

A total of 209 patients with gastroparesis symptoms at NIDDK Gastroparesis Consortium centers underwent gastric scintigraphy and WMCs on separate days to measure regional transit and contractility. Validated questionnaires quantified symptoms.

KEY RESULTS

Solid scintigraphy and liquid scintigraphy were delayed in 68.8% and 34.8% of patients; WMC gastric emptying times (GET) were delayed in 40.3% and showed 52.8% agreement with scintigraphy; 15.5% and 33.5% had delayed small bowel (SBTT) and colon transit (CTT) times. Transit was delayed in ≥2 regions in 23.3%. Rapid transit was rarely observed. Diabetics had slower GET but more rapid SBTT versus idiopathics (P ≤ .02). GET delays related to greater scintigraphic retention, slower SBTT, and fewer gastric contractions (P ≤ .04). Overall gastroparesis symptoms and nausea/vomiting, early satiety/fullness, bloating/distention, and upper abdominal pain subscores showed no relation to WMC transit. Upper and lower abdominal pain scores (P ≤ .03) were greater with increased colon contractions. Constipation correlated with slower CTT and higher colon contractions (P = .03). Diarrhea scores were higher with delayed SBTT and CTT (P ≤ .04).

CONCLUSIONS & INFERENCES

Wireless motility capsules define gastric emptying delays similar but not identical to scintigraphy that are more severe in diabetics and relate to reduced gastric contractility. Extragastric transit delays occur in >40% with suspected gastroparesis. Gastroparesis symptoms show little association with WMC profiles, although lower symptoms relate to small bowel or colon abnormalities.

Endoscopic Gastric Food Retention in Relation to Scintigraphic Gastric Emptying Delays and Clinical Factors

BACKGROUND

Gastric food residue frequently is observed on endoscopy despite fasting.

AIMS

To delineate factors promoting endoscopic food retention in the stomach.

METHODS

Two series of analyses were performed. Magnitudes of retained food in 834 patients from an endoscopy database were related to obstructive versus non-obstructive etiologies and gastric emptying findings. Emptying delays in 619 patients from a scintigraphy database were associated with endoscopic food retention, gastroparesis etiologies, and medications that modify gastric transit.

RESULTS

On endoscopy, 310 (37 %) had large, 338 (41 %) showed medium, and 103 (12 %) exhibited small amounts of retained food in the stomach. Of 433 patients with definable etiologies of food retention, 106 (24 %) had obstructive causes. One hundred three of 327 (31 %) with non-obstructive conditions underwent scintigraphy showing mean 52 ± 29 % 4-h retention. From the scintigraphy database, 164/619 patients (26 %) with delayed emptying exhibited food retention on endoscopy. Four-hour scintigraphic retention was greater with versus without retained food (41 ± 25 vs. 32 ± 22 %, P < 0.001). Retained food occurred more frequently with postsurgical (28/69, 41 %) versus diabetic (33/139, 24 %) and idiopathic (65/294, 22 %) gastroparesis (P = 0.006). Opiate use was more prevalent with increasing food retention (P = 0.02), while other medications that delay or accelerate emptying did not relate to retained food.

CONCLUSIONS

Gastric food retention has obstructive and non-obstructive causes, and is found in one-quarter of gastroparesis, especially postsurgical cases. Gastric emptying delays correlate with amounts of retained food on endoscopy. Retention is influenced by opiates, but not other medications. These analyses delineate pathogenic factors promoting gastric food retention.

Therapeutic applications of ghrelin agonists in the treatment of gastroparesis

There remains an unmet need for effective pharmacologic treatments for gastroparesis. Ghrelin is the endogenous ligand for the growth hormone secretagogue receptor and has been shown to regulate energy homeostasis and exert prokinetic effects on gastrointestinal motility. In recent years, several ghrelin receptor agonists have been studied in clinical trials of patients with diabetic gastroparesis. The intravenous macrocyclic peptidomimetic, TZP-101, initially suggested improvement in gastroparesis symptoms with intravenous administration when compared to placebo. However, in subsequent studies of oral preparations, TZP-102 failed to confirm these results. Another ghrelin receptor agonist, RM-131, was recently shown to significantly accelerate gastric emptying (GE) in patients with type 1 and type 2 diabetes and delayed GE. RM-131 reduced total Gastroparesis Cardinal Symptom Index-Daily Diary (GCSI-DD) and composite scores among type 1 diabetics. Continued development of ghrelin agonists should be explored in attempts to expand therapeutic options for the treatment of gastroparesis.

Emerging drugs for the treatment of gastroparesis

INTRODUCTION

Gastroparesis presents with symptoms of gastric retention with findings of delayed gastric emptying on diagnostic testing. Manifestations of gastroparesis are disabling in severe cases and lead to significant health resource utilization. Current therapies often are ineffective, may exhibit tolerance on chronic administration or produce prominent side effects in large patient subsets.

AREAS COVERED

This review assessed literature on drugs with theoretical efficacy in gastroparesis including medications that accelerate gastric emptying, reduce nausea and vomiting, or act as neuromodulators to reduce gastric sensitivity. Numerous agents exhibit diverse actions to modify gastric sensorimotor function in animal models; however, few medications are in controlled testing in gastroparesis. Prokinetic drugs with promise for this condition include investigational serotonin 5-HT4 agonists, motilin agonists, dopamine D2 antagonists, ghrelin agonists and an agent with combined muscarinic antagonist and acetylcholinesterase inhibitory effects. Other antiemetics and complementary and alternative formulations may be effective for some symptoms.

EXPERT OPINION

Development of effective novel therapies of gastroparesis without the neurotoxicity and cardiac arrhythmogenic effects of current agents will mandate a better definition of the gastric and extragastric factors responsible for the pathogenesis of the varied clinical manifestations of this disorder.

Diabetic gastroparesis: functional/morphologic background, diagnosis, and treatment options

The regulation of gastrointestinal motility mainly involves the smooth muscle, neural (extrinsic and intrinsic), and hormonal elements, the glial cells, and the interstitial cells of Cajal. An orchestrated function of all these components is required for the appropriate propulsive movement of the food in the gastrointestinal tract. Gastroparesis, a pathological slowing-down of gastric emptying, is a result of the damage to the tissue elements involved in the regulation of motility. Gastroparesis is one of the well-known complications of long-standing diabetes mellitus. Although it is rarely a life-threatening complication, it has a deteriorating effect on the quality of life, leads to unpredictable oscillation of the blood glucose level, and increases the time required for the absorption of food and medicines. This review describes the clinical characteristics of diabetic gastroparesis and summarizes the organic and functional motility abnormalities caused by this complication. Finally, the currently available and potential future therapeutic approaches are summarized.

Ghrelin signaling in the gut, its physiological properties, and therapeutic potential

BACKGROUND

Ghrelin, an orexigenic hormone secreted from the stomach, was soon after its discovery hypothesized to be a prokinetic agent, due to its homology to motilin. Studies in animals and humans, using ghrelin and ghrelin receptor agonists, confirmed this hypothesis, suggesting a therapeutic potential for the ghrelin receptor in the treatment of gastrointestinal motility disorders. Precilinical studies demonstrated that ghrelin can act directly on ghrelin receptors on the enteric nervous system, but the predominant route of action under physiological circumstances is signaling via the vagus nerve in the upper gastrointestinal tract and the pelvic nerves in the colon. Different pharmaceutical companies have designed stable ghrelin mimetics that revealed promising results in trials for the treatment of diabetic gastroparesis and post-operative ileus. Nevertheless, no drug was able to reach the market so far, facing problems proving superiority over placebo treatment in larger trials.

PURPOSE

This review aims to summarize the road that led to the current knowledge concerning the prokinetic properties of ghrelin with a focus on the therapeutic potential of ghrelin receptor agonists in the treatment of hypomotility disorders. In addition, we outline some of the problems that could be at the basis of the negative outcome of the trials with ghrelin agonists and question whether the right target groups were selected. It is clear that a new approach is needed to develop marketable drugs with this class of gastroprokinetic agents.

Diabetic gastrointestinal autonomic neuropathy: current status and new achievements for everyday clinical practice

Gastrointestinal symptoms occur frequently among patients with diabetes mellitus and are associated with considerable morbidity. Diabetic gastrointestinal autonomic neuropathy represents a complex disorder with multifactorial pathogenesis, which is still not well understood. It appears to involve a spectrum of metabolic and cellular changes that affect gastrointestinal motor and sensory control. It may affect any organ in the digestive system. Clinical manifestations are often underestimated, and therefore autonomic neuropathy should be suspected in all diabetic patients with unexplained gastrointestinal symptoms. Advances in technology have now enabled assessment of gastrointestinal motor function. Moreover, novel pharmacological approaches, along with endoscopic and surgical treatment options, contribute to improved outcomes. This review summarises the progress achieved in diabetic gastrointestinal autonomic neuropathy during the last years, focusing on clinical issues of practical importance to the everyday clinician.

Gastric electrical stimulation for the treatment of diabetic gastroparesis

Diabetic gastroparesis is a component of autonomic neuropathy, and is the most common manifestation of gastrointestinal neuropathy. Diabetes is responsible for about one quarter of gastroparesis. The upper gastrointestinal symptoms are often non-specific and dominated by nausea, vomiting, early satiety, fullness, bloating. We also have to look for diabetic gastroparesis in case of metabolic instability, such as postprandial hypoglycaemia. The pathophysiology of diabetic gastroparesis is complex, partly due to a vagus nerve damage, but also to changes in secretion of hormones such as motilin and ghrelin. A decrease in the stem cell factor (SCF), growth factor for cells of Cajal (gastric pacemaker), was found in subjects with diabetic gastroparesis. These abnormalities lead to an excessive relaxation in the corpus, a hypomotility of antrum, a desynchronization antrum-duodenum-pylorus, and finally an abnormal duodenal motility. The treatment of diabetic gastroparesis is based on diabetes control, and split meals by reducing the fiber content and fat from the diet. The antiemetic and prokinetic agents should be tested primarily in people with nausea and vomiting. Finally, after failure of conventional measures, the use of gastric neuromodulation is an effective alternative, with well-defined indications. Introduced in the 1970s, this technology works by applying electrical stimulation continues at the gastric antrum, particularly in patients whose gastric symptoms are refractory to other therapies. Its efficacy has been recently reported in different causes of gastroparesis, especially in diabetes. Gastric emptying based on gastric scintigraphy, gastrointestinal symptoms, biological markers of glycaemic control and quality of life are partly improved, but not normalized. Finally, a heavy nutritional care is sometimes necessary in the most severe forms. The enteral route should be preferred (nasojejunal and jejunostomy if possible efficiency). However, in case of failure especially in patients with small bowel neuropathy, the long-term parenteral nutrition is sometimes required.

Gastroparesis: concepts, controversies, and challenges

Patients with gastroparesis often present a challenge to the treating physician. Postprandial symptoms with nausea and vomiting may not only lead to nutritional and metabolic consequences, but also cause significant disruptions to social activities that often center around food. While the definition of gastroparesis focuses on impaired gastric emptying, treatment options that affect gastric function are limited and often disappointing. The female predominance, the mostly idiopathic nature of the illness with a common history of abuse, and coexisting anxiety or depression show parallels with other functional disorders of the gastrointestinal tract. These parallels provided the rationale for some initial studies investigating alternative therapies that target the brain rather than the stomach. This emerging shift in medical therapy comes at a time when clinical studies suggest that gastric electrical stimulation may exert its effects by modulating visceral sensory processing rather than altering gastric motility. Physiologic and detailed anatomic investigations also support a more complex picture with different disease mechanisms, ranging from impaired accommodation to apparent visceral hypersensitivity or decreased interstitial cells of Cajal to inflammatory infiltration of myenteric ganglia. Delayed gastric emptying remains the endophenotype defining gastroparesis. However, our treatment options go beyond prokinetics and may allow us to improve the quality of life of affected individuals.

Glucose sensing by gut endocrine cells and activation of the vagal afferent pathway is impaired in a rodent model of type 2 diabetes mellitus

Glucose in the gut lumen activates gut endocrine cells to release 5-HT, glucagon-like peptide 1/2 (GLP-1/2), and glucose-dependent insulinotropic polypeptide (GIP), which act to change gastrointestinal function and regulate postprandial plasma glucose. There is evidence that both release and action of incretin hormones is reduced in type 2 diabetes (T2D). We measured cellular activation of enteroendocrine and enterochromaffin cells, enteric neurons, and vagal afferent neurons in response to intestinal glucose in a model of type 2 diabetes mellitus, the UCD-T2DM rat. Prediabetic (PD), recent-diabetic (RD, 2 wk postonset), and 3-mo diabetic (3MD) fasted UCD-T2DM rats were given an orogastric gavage of vehicle (water, 0.5 ml /100 g body wt) or glucose (330 μmol/100 g body wt); after 6 min tissue was removed and cellular activation was determined by immunohistochemistry for phosphorylated calcium calmodulin-dependent kinase II (pCaMKII). In PD rats, pCaMKII immunoreactivity was increased in duodenal 5-HT (P < 0.001), K (P < 0.01) and L (P < 0.01) cells in response to glucose; glucose-induced activation of all three cell types was significantly reduced in RD and 3MD compared with PD rats. Immunoreactivity for GLP-1, but not GIP, was significantly reduced in RD and 3MD compared with PD rats (P < 0.01). Administration of glucose significantly increased pCaMKII in enteric and vagal afferent neurons in PD rats; glucose-induced pCaMKII immunoreactivity was attenuated in enteric and vagal afferent neurons (P < 0.01, P < 0.001, respectively) in RD and 3MD. These data suggest that glucose sensing in enteroendocrine and enterochromaffin cells and activation of neural pathways is markedly impaired in UCD-T2DM rats.

Similarities and differences between diabetic and idiopathic gastroparesis

BACKGROUND & AIMS

Gastroparesis can be diabetic or idiopathic, yet little is known about differences in their presentation. We compared clinical characteristics, symptoms, and gastric emptying in patients with type 1 or type 2 diabetic (DG) or idiopathic (IG) gastroparesis.

METHODS

We analyzed data from 416 patients with gastroparesis who were enrolled in the National Institute of Diabetes and Digestive and Kidney Diseases Gastroparesis Registry; 254 had IG (most were female and white), and 137 had DG (78 had type 1 and 59 had type 2). Registry data included detailed histories, physical examinations, results from gastric emptying scintigraphy, and responses to validated symptom questionnaires.

RESULTS

Patients with type 2 diabetes mellitus (DM) were an average of 13 years older at the onset of symptoms of gastroparesis and heavier than patients with IG. Patients with type 1 DM had more hospitalizations in the past year than patients with IG. Symptoms that prompted evaluation more often included vomiting for DG and abdominal pain for IG. Patients with DG had more severe retching and vomiting than those with IG, whereas patients with IG had more severe early satiety and postprandial fullness subscores. Compared with IG, gastric retention was greater in patients with type 1 DM. More than 50% of patients with type 1 DM had severe retention (>35% at 4 hours); they took prokinetic agents more frequently and were more likely to receive gastric electric stimulation.

CONCLUSIONS

There are similarities and differences in clinical characteristics of DG and IG. Gastroparesis is a heterogeneous disorder; its etiology affects symptoms and severity. Long-term studies are needed to determine whether the differences in symptoms and gastric emptying affect progression and treatment responses.

Ghrelin as a target for gastrointestinal motility disorders

The therapeutic potential of ghrelin and synthetic ghrelin receptor (GRLN-R) agonists for the treatment of gastrointestinal (GI) motility disorders is based on their ability to stimulate coordinated patterns of propulsive GI motility. This review focuses on the latest findings that support the therapeutic potential of GRLN-R agonists for the treatment of GI motility disorders. The review highlights the preclinical and clinical prokinetic effects of ghrelin and a series of novel ghrelin mimetics to exert prokinetic effects on the GI tract. We build upon a series of excellent reviews to critically discuss the evidence that supports the potential of GRLN-R agonists to normalize GI motility in patients with GI hypomotility disorders such as gastroparesis, post-operative ileus (POI), idiopathic chronic constipation and functional bowel disorders.

Ghrelin, appetite and gastric electrical stimulation

Ghrelin is a peptide hormone produced mainly by the stomach and has widespread physiological functions including increase in appetite. The stimulation of the ghrelin system represents a potential therapeutic approach in various disorders characterized by deficient ghrelin signaling or by low appetite. This stimulation may be achieved via pharmacological targeting of the ghrelin receptor with synthetic ghrelin or ghrelin mimetics or via increased endogenous ghrelin production. Recently, it was demonstrated that gastric electrical stimulation (GES) with Enterra parameters results in increased ghrelin production in rats. Furthermore, recent data revealed putative role of ghrelin-reactive immunoglobulins in the modulation of the ghrelin signaling which can be also stimulated by GES. Here, we review the links between GES and ghrelin in existing GES experimental and clinical applications for treatment of gastroparesis, functional dyspepsia or obesity and discuss if GES can be proposed as a non-pharmacological approach to improve ghrelin secretion in several pathological conditions characterized by low appetite, such as anorexia nervosa or anorexia-cachexia syndrome.

Bloating in gastroparesis: severity, impact, and associated factors

OBJECTIVES

Bloating is commonly reported in gastroparesis, but its prevalence, impact, and associated factors are uninvestigated. We aimed to quantify the prevalence of bloating in gastroparesis and relate its severity to clinical factors and quality of life.

METHODS

Survey, examination, and scintigraphy data were compared in 335 gastroparesis patients from 6 centers of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) Gastroparesis Clinical Research Consortium. Bloating severity was stratified using Gastroparesis Cardinal Symptom Index (GCSI) bloating subscale scores.

RESULTS

Bloating severity of at least mild (GCSI ≥2) and severe (GCSI ≥4) grades were reported by 76 and 41% of patients, respectively. Bloating severity related to female gender (P<0.0001) and overweight status (P=0.04) on regression analysis and correlated with intensity of nausea, postprandial fullness, visible distention, abdominal pain, and altered bowel function (P<0.05). Disease etiology, smoking status, and gastric emptying did not relate to bloating subset (P>0.05). Disease-specific quality of life and general measures of well-being were progressively impaired with increasing bloating severity (P=0.01). Probiotic use (P=0.03) and use of antidepressants with significant norepinephrine reuptake inhibitor activity (P=0.045) use related to bloating severity; antiemetic use trended higher with worsening bloating (P=0.06).

CONCLUSIONS

Bloating is prevalent in gastroparesis and is severe in many individuals. Bloating severity relates to female gender, body weight, and intensity of other symptoms. The symptom impairs quality of life but is not influenced by gastric emptying rates. Antiemetics, probiotics, and antidepressants with significant norepinephrine reuptake inhibitor activity may affect reports of bloating. These findings provide insight into this underappreciated symptom of gastroparesis.

Ghrelin and oxidative stress in gastrointestinal tract

Oxidative stress is a major cause of the gastrointestinal damage under physical or psychological stress. Ghrelin exhibits gastroprotective effects and they are supposed to be derived from antioxidant effects. In gastroduodenal mucosal injury, the plasma ghrelin levels increase in response to the demand for gastroduodenal cytoprotection. However, in the condition of Helicobacter pylori-induced gastric mucosal severe atrophy, the plasma ghrelin concentration shifted to lower levels. In diabetic gastroparesis, the regulation of ghrelin secretion is impaired with vagal nerve dysfunction. Selective ghrelin agonist is expected to represent a new class of prokinetic agent. In addition, the plasma ghrelin levels are also enhanced by systemic oxidative stress, and ghrelin exhibits antioxidant effects in many organs, such as heart, pancreas, and lung. This suggests that ghrelin would be an important player as a sensor of systemic oxidative stress.

Modulation of ingestive behavior and gastrointestinal motility by ghrelin in diabetic animals and humans

Acyl ghrelin, a 28-amino acid peptide hormone, is the endogenous cognate ligand for the growth hormone secretagogue receptor. Ghrelin is involved in stimulating growth hormone release, eliciting feeding behavior, inducing adiposity and stimulating gastrointestinal motility. Ghrelin is unique for its post-translational modification of O-n-octanoylation at serine 3 through ghrelin O-acyltransferase, and is the only peripheral signal to enhance food intake. Plasma ghrelin levels manifest "biphasic changes" in diabetes mellitus (DM). In the early stage of DM, the stomach significantly increases the secretion of ghrelin into the plasma, and elevated plasma ghrelin levels are correlated with diabetic hyperphagic feeding and accelerated gastrointestinal motility. In the late stage of DM, plasma ghrelin levels may be lower, which might be linked with anorexia/muscle wasting, delayed gastrointestinal transit, and even gastroparesis. Therefore, the unique ghrelin system may be the most important player compared to the other hindgut hormones participating in the "entero-insular axis". Further studies using either knockdown or knockout of ghrelin gene products and ghrelin O-acyltransferase may unravel the pathogenesis of DM, and show benefits in combating this disease and metabolic syndrome.

Ghrelin and obestatin levels in type 2 diabetic patients with and without delayed gastric emptying

Alterations in the neurohumoral regulation of the upper intestine may change rhythmicity and pattern of ghrelin and obestatin, the latter presumably antagonizing ghrelin effects. Five nongastroparetic diabetic patients and five with gastroparesis were investigated. Over 390 min including breakfast and lunch, ghrelin was significantly lower in patients with gastroparesis compared with in those without (P = 0.015). Ghrelin subsequent to lunch decreased significantly (P = 0.011) in patients without gastroparesis, but not in gastroparetic patients (P = 0.669). Obestatin was similar in both groups and unchanged. No significant differences in ghrelin-to-obestatin ratio were observed (P = 0.530). Loss of rhythmicity in the ghrelin levels of gastroparetic diabetics highlights the importance of integrity of the neurohumoral-intestinal axis. Stable diurnal obestatin levels do not support the concept of interaction between ghrelin and obestatin in terms of regulation of food intake and gastric emptying.

Pathophysiology and management of gastroparesis

Gastroparesis is characterized by upper gastrointestinal symptoms associated with delayed gastric emptying, without mechanical obstruction. However, symptoms do not correlate well with the magnitude of delay in gastric emptying. Diabetes mellitus and surgery are the most common causes, although more than 30% of cases are idiopathic. Coordination of insulin action with nutrient delivery is important in diabetics, as postprandial blood glucose levels and gastric emptying are interdependent, and gastroparesis probably represents a major cause of poor glycemic control. Scintigraphy is the gold standard for measuring gastric emptying. Current treatment mainly involves the use of prokinetic drugs. Pyloric botulinum toxin injection and gastric electrical stimulation require more evidence from controlled studies before their use can be recommended. Surgical options remain inadequately studied.

Endoscopic pyloric injection of botulinum toxin-A for the treatment of postvagotomy gastroparesis

OBJECTIVES

To evaluate the efficacy of botulinum toxin-A in the treatment of postvagotomy gastroparesis.

METHODS

This open-labeled trial identified and recruited 11 subjects who developed symptomatic gastroparesis after a vagotomy (9 fundoplication, 1 trauma, and 1 exploratory laparotomy). Gastroparesis was defined as an abnormal solid-phase gastric emptying test using the standardized 4-hour radionuclide eggbeater meal method and vagotomy was confirmed with a sham meal challenge test. To complete the study, subjects should have completed the 6-month follow-up visit after their pylorus was injected with botulinum toxin-A injection in a 4-quadrant manner. Patients either received 100 (n = 2) or 200 (n = 9) units of botulinum toxin. Questionnaires recorded symptom severity of gastroparesis at baseline and at monthly intervals for 6 months after the therapy was completed by the patients.

RESULTS

Of the 11 subjects initially recruited, 10 finished the 6-month follow-up visit (7 women). Mean age was 51 years (range, 31-84 years). Mean symptom score at baseline was 16 (95% CI 13-19) and showed a numerical decline to 9 (P > 0.05) over the 6-month period after the procedure (95% CI 5-13). Seven (70%) patients observed >30% improvement in the total symptom score. No complications were recorded.

CONCLUSIONS

In conclusion, this open-label study in patients with postvagotomy gastroparesis patients reveals a reduction of gastroparetic symptoms at 1 and 3 months after treatment with pyloric injection of botulinum toxin-A, with return of symptoms by 6 months. Thus, botulinum toxin treatment does not produce a sustained reduction in gastroparetic symptoms in this clinical setting.

No ghrelin response to oral glucose in diabetes mellitus with gastroparesis

To investigate the role of ghrelin, an endogenous ligand of the growth hormone secretagogue receptor, in diabetic gastroparesis, we evaluated the plasma ghrelin profile during the oral glucose tolerance test in 55 patients with diabetes (men/women: 36/19, mean +/- SE of age: 55.1 +/- 1.7 years) with or without gastroparesis (diagnosed by the (13)C-acetate breath test). We also further examined cardiac autonomic neuropathy by assessing 24-hour variation of the R-R interval in randomly selected 32 patients with diabetes (men/women: 23/9, mean +/- SE of age: 54.2 +/- 2.5 years), and evaluated the influence of autonomic neuropathy on ghrelin. The fasting plasma ghrelin level was significantly lower in diabetes mellitus with gastroparesis than in healthy controls (7.9 +/- 0.7 fmol/ml versus 16.6 +/- 5.3 fmol/ml, p = 0.006). Patients with diabetes with gastroparesis showed no decrease of plasma ghrelin after glucose loading, unlike patients without gastroparesis or healthy controls. Diabetes mellitus with autonomic neuropathy, but not those without it, also showed no decrease of plasma ghrelin after glucose loading. Diabetic gastroparesis may be related to ghrelin-associated neurohormonal abnormalities, but the pathophysiological meaning of this abnormal ghrelin response needs further clarification.

Management of gastroparesis

Gastroparesis presents with nausea, vomiting, early satiety and abdominal discomfort, as well as a range of nongastrointestinal manifestations in association with delays in gastric emptying. The disorder may be a consequence of systemic illnesses, such as diabetes mellitus, occur as a complication of gastroesophageal surgery or develop in an idiopathic fashion and may mimic other disorders with normal gastric emptying. Some cases of idiopathic gastroparesis present after a viral infection. Management relies primarily on therapies that accelerate gastric emptying or reduce vomiting, although endoscopic or surgical options are available for refractory cases. Current research is focusing on the cellular and molecular mechanisms underlying development of delayed gastric emptying, as well as factors unrelated to motor dysfunction that may elicit some symptoms. Future pharmaceuticals will target the contractile and nonmotor defects via novel pathways. Novel electrical stimulation techniques will be employed either alone or in combination with medications.

Differences in intragastric pH in diabetic vs. idiopathic gastroparesis: relation to degree of gastric retention

Evidence suggests that distinct mechanisms underlie diabetic and idiopathic gastroparesis. Differences in gastric acid in gastroparesis of different etiologies and varying degrees of gastric stasis are uninvestigated. We tested the hypotheses that 1) gastric pH profiles show differential alteration in diabetic vs. idiopathic gastroparesis and 2) abnormal pH profiles relate to the severity of gastric stasis. Sixty-four healthy control subjects and 44 gastroparesis patients (20 diabetic, 24 idiopathic) swallowed wireless transmitting capsules and then consumed (99m)Tc-sulfur colloid-labeled meals for gastric scintigraphy. Gastric pH from the capsule was recorded every 5 s. Basal pH was higher in diabetic (3.64 +/- 0.41) vs. control subjects (1.90 +/- 0.18) and idiopathic subjects (2.41 +/- 0.42; P < 0.05). Meals evoked initial pH increases that were greater in diabetic (4.98 +/- 0.32) than idiopathic patients (3.89 +/- 0.39; P = 0.03) but not control subjects (4.48 +/- 0.14). pH nadirs prior to gastric capsule evacuation were higher in diabetic patients (1.50 +/- 0.23) than control subjects (0.58 +/- 0.11; P = 0.003). Four-hour gastric retention was similar in diabetic (18.3 +/- 0.5%) and idiopathic (19.4 +/- 0.5%) patients but higher than control subjects (2.2 +/- 0.5%; P < 0.001). Compared with control subjects, those with moderate-severe stasis (>20% retention at 4 h) had higher basal (3.91 +/- 0.55) and nadir pH (2.23 +/- 0.42) values (P < 0.05). In subgroup analyses, both diabetic and idiopathic patients with moderate-severe gastroparesis exhibited increased pH parameters vs. those with mild gastroparesis. In conclusion, diabetic patients with gastroparesis exhibit reduced gastric acid, an effect more pronounced in those with severely delayed gastric emptying. Idiopathic gastroparetic subjects exhibit nearly normal acid profiles, although those with severely delayed emptying show reduced acid vs. those with mild delays. Thus both etiology and degree of gastric stasis determine gastric acidity in gastroparesis.

Type 1 diabetes and gastroparesis: diagnosis and treatment

Patients with gastroparesis present with gastrointestinal symptoms and non-gastrointestinal manifestations in association with objective delays in gastric emptying. The condition complicates the course of many patients with type 1 diabetes mellitus, usually in those with longstanding poor glycemic control with other associated diabetic complications. The diagnosis is made by directed evaluation to exclude organic diseases that can mimic the clinical presentation of gastroparesis, coupled with verification of gastric retention. Current therapy relies on dietary modifications, medications to stimulate gastric evacuation, and agents to reduce vomiting. Endoscopic and surgical options are increasingly used in patients who are refractory to drug treatment.

Diabetes and the enteric nervous system

Diabetes is associated with several changes in gastrointestinal (GI) motility and associated symptoms such as nausea, bloating, abdominal pain, diarrhoea and constipation. The pathogenesis of altered GI functions in diabetes is multifactorial and the role of the enteric nervous system (ENS) in this respect has gained significant importance. In this review, we summarize the research carried out on diabetes-related changes in the ENS. Changes in the inhibitory and excitatory enteric neurons are described highlighting the role of loss of inhibitory neurons in early diabetic enteric neuropathy. The functional consequences of these neuronal changes result in altered gastric emptying, diarrhoea or constipation. Diabetes can also affect GI motility through changes in intestinal smooth muscle or alterations in extrinsic neuronal control. Hyperglycaemia and oxidative stress play an important role in the pathophysiology of these ENS changes. Antioxidants to prevent or treat diabetic GI motility problems have therapeutic potential. Recent research on the nerve-immune interactions demonstrates inflammation-associated neurodegeneration which can lead to motility related problems in diabetes.

Gastroparesis: symptoms, evaluation, and treatment

Gastroparesis presents with gastrointestinal symptoms and nongastrointestinal manifestations in association with objective delays in gastric emptying. The condition may complicate several systemic disorders or may be idiopathic in nature. The diagnosis is made by directed evaluation to exclude organic diseases, which can mimic the clinical presentation of gastroparesis coupled with quantification of gastric emptying. Current therapies rely on dietary modifications, medications to stimulate gastric evacuation, and agents to reduce vomiting. Endoscopic and surgical options are increasingly used for cases refractory to medication treatment.