Effects of exogenous glucagon-like peptide-1 on gastric emptying and glucose absorption in the critically ill: relationship to glycemia

The Emerging Role of GLP-1 Agonists in Burn Care: What Do We Know?

Glucagon-like peptide-1 (GLP-1) agonists mimic the action of GLP-1, a hormone that regulates blood glucose levels via stimulation of insulin release and inhibition of glucagon secretion. After the burn, the current literature suggests that the use of GLP-1 agonists results in less insulin dependence with similar glucose control and hypoglycemic events to patients receiving a basal-bolus insulin regimen. Glucagon-like peptide-1 agonists may also promote wound healing through various mechanisms including angiogenesis and improved keratinocyte migration. Despite the potential benefits, GLP-1 agonists reduce gastrointestinal motility which impacts their widespread adoption in burn care. This dysmotility can result in inadequate nutrition delivery, unintentional weight loss, and is a potential aspiration risk. The net impact of these medications on patients with burns is unclear. Given their potential to demonstrate the safety, efficacy, and optimal dosing of various GLP-1 agonists in acute burn management.

Improvement in Helicobacter pylori Eradication Among Adults Receiving Semaglutide: A Population-Based Propensity-Score-Adjusted Analysis

BACKGROUND

Glucagon-like peptide-1 (GLP-1) receptor agonists delay gastric emptying and are used for the treatment of diabetes (DM) and obesity. Successful treatment of Helicobacter pylori (H. pylori) infection depends upon a precise dosing schedule. We aimed to examine the impact of GLP-1 drugs on antibiotic treatment for H. pylori.

METHODS

Adults with a new diagnosis of H. pylori infection who received treatment between 2014 and 2023 were identified in the Clalit Health Services database. Subjects were divided into groups based on diagnoses of DM and obesity, and exposure to GLP-1 drugs. A 1:2 propensity-score matched dataset was used to determine the effect of GLP-1 drugs on eradication success.

RESULTS

We identified 426 individuals who received, and 36,436 who did not receive GLP-1 drugs. Eradication among those who did and did not receive GLP-1 drugs was 86.6% and 83.7%, respectively (p = 0.059 across subgroups). Eradication among those who received semaglutide was 93.8% (OR 2.78, 95% CI 1.32-5.83, p = 0.007). Eradication in subjects who received dulaglutide (88.6%) or liraglutide (81.4%) was not significantly changed. When applying a propensity-score-adjusted analysis, eradication remained significantly increased among individuals who received semaglutide (OR 2.89, 95% CI 1.24-6.74, p = 0.014). Additional independent predictors of successful eradication included male sex, high socioeconomic status, quadruple therapy, and older age (p < 0.001 for all).

CONCLUSIONS

Co-administration of semaglutide and antibiotics for H. pylori infection is associated with an increased likelihood of successful eradication.

Physiology and Pharmacology of Effects of GLP-1-based Therapies on Gastric, Biliary and Intestinal Motility

Glucagon-like peptide-1 (GLP-1) receptor agonists and the dual GLP-1- and glucose-dependent insulinotropic polypeptide receptor co-agonist tirzepatide (referred to here collectively as "GLP-1-based therapy") are incretin-based therapies being used increasingly in the management of both type 2 diabetes and obesity. They are now recognized to have beneficial effects beyond improved glycemic control and weight loss, including cardiovascular and renal protection. GLP-1-based therapy also slows gastric emptying, which has benefits (lowering postprandial glucose), but also potential risks (eg, hypoglycemia in individuals on insulin or sulphonylurea therapy). Their effects on the gallbladder may also be beneficial, contributing to reducing postprandial triglycerides, but they also potentially increase the risk of biliary disease. In this review, we summarize the effects of GLP-1 and incretin-based therapeutics on gastric, biliary and small intestinal function. An improved understanding of these effects will optimize the use of these drugs.

Gastrointestinal effects of GLP-1 receptor agonists: mechanisms, management, and future directions

The availability of glucagon-like peptide-1 (GLP-1) receptor agonists (RAs) such as liraglutide and semaglutide, and a GLP-1 and glucose dependent insulinotropic polypeptide coagonist (tirzepatide) represents a paradigm shift in the management of both type 2 diabetes and obesity. There is now considerable attention, including in the public media, on the effect of both long-acting and short-acting GLP-1RAs to delay gastric emptying. Although slowed gastric emptying is integral to reducing post-prandial blood glucose responses in type 2 diabetes, marked slowing of gastric emptying might also increase the propensity for longer intragastric retention of food, with a consequent increased risk of aspiration at the time of surgery or upper gastrointestinal endoscopy. This Personal View summarises current knowledge of the effects of GLP-1 and GLP-1RAs on gastrointestinal physiology, particularly gastric emptying, and discusses the implications for the development of sound pre-operative or pre-procedural guidelines. The development of pre-procedural guidelines is currently compromised by the poor evidence base, particularly in relation to the effect of long-acting GLP-1RAs on gastric emptying. We suggest pre-procedural management pathways for individuals on GLP-1RA-based therapy and discuss priorities for future research.

The enteroendocrine axis and its effect on gastrointestinal function, nutrition, and inflammation

PURPOSE OF REVIEW

Gastrointestinal (GI) dysfunction limits enteral nutrition (EN) delivery in critical illness and contributes to systemic inflammation. The enteroendocrine (EE) axis plays an integral role in this interface between nutrition, inflammation, and GI function in critical illness. In this review, we present an overview of the EE system with a focus on its role in GI inflammation and function.

RECENT FINDINGS

Enteroendocrine cells have been primarily described in their role in macronutrient digestion and absorption. Recent research has expanded on the diverse functions of EE cells including their ability to sense microbial peptides and metabolites and regulate immune function and inflammation. Therefore, EE cells may be both affected by and contribute to many pathophysiologic states and interventions of critical illness such as dysbiosis , inflammation, and alternative EN strategies. In this review, we present an overview of EE cells including their growing role in nonnutrient functions and integrate this understanding into relevant aspects of critical illness with a focus on EN.

SUMMARY

The EE system is key in maintaining GI homeostasis in critical illness, and how it is impacted and contributes to outcomes in the setting of dysbiosis , inflammation and different feeding strategies in critical illness should be considered.

Association of glucagon-like peptide receptor 1 agonist therapy with the presence of gastric contents in fasting patients undergoing endoscopy under anesthesia care: a historical cohort study

PURPOSE

We aimed to estimate the association of glucagon-like peptide 1 (GLP-1) receptor agonist therapy with the incidence of endoscopically visible gastric contents after preprocedural fasting.

METHODS

We reviewed the records of esophagogastroduodenoscopy (EGD) performed at our institution between 2019 and 2023 and determined the presence of residual gastric contents from the procedure notes and saved images. We compared patients taking GLP-1 agonists at the time of the procedure (GLP group, 90 procedures) with patients who started GLP-1 agonist therapy within 1,000 days after undergoing EGD (control, 102 procedures). We excluded emergent procedures without fasting, combined EGD/colonoscopy procedures, and patients with known gastroparesis or previous gastric surgery. We estimated the association between GLP-1 agonist therapy and residual gastric contents with a confounder-adjusted generalized linear mixed effect model.

RESULTS

Compared with controls, the GLP cohort had a higher age, American Society of Anesthesiologists' Physical Status, and incidence of nausea and diabetes mellitus. Body mass index and fasting duration were comparable between groups. Visible gastric content was documented in 17 procedures in the GLP group (19%) and in five procedures in the control group (5%), with an associated confounder adjusted odds ratio of 5.8 (95% confidence interval, 1.7 to 19.3; P = 0.004). There were five instances of emergent endotracheal intubation in the GLP group vs one case in control and one case of pulmonary aspiration vs none in control.

CONCLUSIONS

In fasting patients, GLP-1 agonist therapy was associated with an increased incidence of residual gastric contents, potentially posing an additional risk of periprocedural pulmonary aspiration.

Effect of gut hormones on bone metabolism and their possible mechanisms in the treatment of osteoporosis

Bone is a highly dynamic organ that changes with the daily circadian rhythm. During the day, bone resorption is suppressed due to eating, while it increases at night. This circadian rhythm of the skeleton is regulated by gut hormones. Until now, gut hormones that have been found to affect skeletal homeostasis include glucagon-like peptide-1 (GLP-1), glucagon-like peptide-2 (GLP-2), glucose-dependent insulinotropic polypeptide (GIP), and peptide YY (PYY), which exerts its effects by binding to its cognate receptors (GLP-1R, GLP-2R, GIPR, and Y1R). Several studies have shown that GLP-1, GLP-2, and GIP all inhibit bone resorption, while GIP also promotes bone formation. Notably, PYY has a strong bone resorption-promoting effect. In addition, gut microbiota (GM) plays an important role in maintaining bone homeostasis. This review outlines the roles of GLP-1, GLP-2, GIP, and PYY in bone metabolism and discusses the roles of gut hormones and the GM in regulating bone homeostasis and their potential mechanisms.

Heterogeneity of surrogate outcome measures used in critical care studies: A systematic review

BACKGROUND

The choice of outcome measure is a critical decision in the design of any clinical trial, but many Phase III clinical trials in critical care fail to detect a difference between the interventions being compared. This may be because the surrogate outcomes used to show beneficial effects in early phase trials (which informed the design of the subsequent Phase III trials) are not valid guides to the differences between the interventions for the main outcomes of the Phase III trials. We undertook a systematic review (1) to generate a list of outcome measures used in critical care trials, (2) to determine the variability in the outcome reporting in the respiratory subgroup and (3) to create a smaller list of potential early phase endpoints in the respiratory subgroup.

METHODS

Data related to outcomes were extracted from studies published in the six top-ranked critical care journals between 2010 and 2020. Outcomes were classified into subcategories and categories. A subset of early phase endpoints relevant to the respiratory subgroup was selected for further investigation. The variability of the outcomes and the variability in reporting was investigated.

RESULTS

A total of 6905 references were retrieved and a total of 294 separate outcomes were identified from 58 studies. The outcomes were then classified into 11 categories and 66 subcategories. A subset of 22 outcomes relevant for the respiratory group were identified as potential early phase outcomes. The summary statistics, time points and definitions show the outcomes are analysed and reported in different ways.

CONCLUSION

The outcome measures were defined, analysed and reported in a variety of ways. This creates difficulties for synthesising data in systematic reviews and planning definitive trials. This review once again highlights an urgent need for standardisation and validation of surrogate outcomes reported in critical care trials. Future work should aim to validate and develop a core outcome set for surrogate outcomes in critical care trials.

Inter-relationships between gastric emptying and glycaemia: Implications for clinical practice

Gastric emptying (GE) exhibits a wide inter-individual variation and is a major determinant of postprandial glycaemia in health and diabetes; the rise in blood glucose following oral carbohydrate is greater when GE is relatively more rapid and more sustained when glucose tolerance is impaired. Conversely, GE is influenced by the acute glycaemic environment acute hyperglycaemia slows, while acute hypoglycaemia accelerates it. Delayed GE (gastroparesis) occurs frequently in diabetes and critical illness. In diabetes, this poses challenges for management, particularly in hospitalised individuals and/or those using insulin. In critical illness it compromises the delivery of nutrition and increases the risk of regurgitation and aspiration with consequent lung dysfunction and ventilator dependence. Substantial advances in knowledge relating to GE, which is now recognised as a major determinant of the magnitude of the rise in blood glucose after a meal in both health and diabetes and, the impact of acute glycaemic environment on the rate of GE have been made and the use of gut-based therapies such as glucagon-like peptide-1 receptor agonists, which may profoundly impact GE, in the management of type 2 diabetes, has become commonplace. This necessitates an increased understanding of the complex inter-relationships of GE with glycaemia, its implications in hospitalised patients and the relevance of dysglycaemia and its management, particularly in critical illness. Current approaches to management of gastroparesis to achieve more personalised diabetes care, relevant to clinical practice, is detailed. Further studies focusing on the interactions of medications affecting GE and the glycaemic environment in hospitalised patients, are required.

Side effect profile of pharmacologic therapies for liver fibrosis in nonalcoholic fatty liver disease: a systematic review and network meta-analysis

Several studies have found that antifibrosis treatment for nonalcoholic fatty liver disease (NAFLD) can cause a variety of side effects. No network meta-analysis (NMA) analyzes the adverse events of antifibrotic drugs for NAFLD. This NMA aimed to systematically compare the drug-related side effects when using different pharmacological agents for the treatment of liver fibrosis in NAFLD. PubMed, EMBASE, Web of Science and Cochrane Library were systematically searched to select related studies published in English from the database inception until 30 June 2022. We conducted Bayesian fixed-effects NMA using data from randomized controlled trials (RCTs) to derive relative risks (RRs). The surface under the cumulative ranking (SUCRA) probabilities was used to assess ranking. A total of 26 RCTs with 19 interventions met the inclusion criteria. SUCRA analysis suggested that the lanifibranor group had the highest risk of diarrhea (SUCRA, 94), whereas the liraglutide group had the highest risk of constipation (SUCRA, 92.9). The semaglutide group showed the highest incidence of nausea (SUCRA, 81.2) and abdominal pain (SUCRA, 90.5), respectively. The cenicriviroc group showed the highest risk in the incidence of fatigue (SUCRA, 82.4). The MSDC-0602K group had the highest risk of headache (SUCRA, 76.4), whereas the obeticholic acid group had the highest risk of pruritus (SUCRA, 80.1). The risk of side effects significantly varied among different pharmacologic regimens, and evidence showed that lanifibranor, liraglutide, semaglutide, cenicriviroc, MSDC-0602K and obeticholic acid were the pharmacological interventions with the highest risk in patients with NAFLD. This study may guide clinicians and support further research.

One-hour plasma glucose level after a 75 g oral glucose load and its relationship to gastric emptying in survivors of critical illness and stress hyperglycaemia

Objective: A 1-hour plasma glucose level ≥ 8.6 mmol/L in a 75 g oral glucose tolerance test has been strongly associated with increased morbidity and mortality in outpatients without diabetes. Our primary aim was to evaluate the 1-hour plasma glucose level in a 75 g glucose tolerance test in survivors of critical illness with stress hyperglycaemia at 3 months after intensive care unit (ICU) discharge, with the secondary aims to evaluate the 2-hour plasma glucose level, glycated haemoglobin (HbA1c), and gastric emptying. Design:Post hoc analysis of a single-centre, prospective cohort study. Setting: Single-centre, tertiary referral, mixed medical-surgical ICU. Participants: Consecutively admitted patients aged ≥ 18 years who developed stress hyperglycaemia and survived to hospital discharge were eligible. Interventions: Participants returned at 3 months after ICU discharge and underwent a 75 g oral glucose tolerance test. Main outcome measures: One- and 2-hour post load plasma glucose level, HbA1c, and assessment of gastric emptying via an isotope breath test. Results: Thirty-five patients (12 females; mean age, 58.5 years [SD, 10.5]; mean HbA1c, 37.4 mmol/mol [SD, 7.0]) attended the followup. In 32/35 patients (91%) the 1-hour post load plasma glucose level was ≥ 8.6 mmol/L. There was a positive correlation between the plasma glucose level at 1 hour (r2 = 0.21; P = 0.006), but no correlation between the 2-hour glucose level (r2 = 0.006; P = 0.63) and gastric emptying. Conclusion: Glucose intolerance, when defined as 1-hour glucose level ≥ 8.6 mmol/L following a 75 g oral glucose load, persists at 3 months in most survivors of stress hyperglycaemia and is dependent on the rate of gastric emptying. Longitudinal studies to characterise mechanisms underlying dysglycaemia and progression to diabetes in individuals with stress hyperglycaemia are indicated.

Exendin-4 Exacerbates Burn-Induced Mortality in Mice by Switching to Th2 Response

INTRODUCTION

To determine if Exendin-4 could be a therapeutic agent for burn-induced hyperglycemia.

MATERIALS AND METHODS

Male Balb/c mice received a bolus of Exendin-4 intraperitoneally immediately after 15% total body surface area scald injury. Tail glucose levels were recorded and T-cell functions were analyzed at 4 h and 24 h postburn (pb). Pancreatic pathology was observed consecutively. The secretions of cytokines were detected in serum, spleen, and lung. Apoptosis of splenic CD3+ T-cells was examined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling and flow cytometry.

RESULTS

Although Exendin-4 could attenuate burn-induced hyperglycemia in mice at 4 h pb, it accelerated their survival dose dependently with progressive depletion of splenocyte number. T-cell function underwent two-phasic changes following Exendin-4 treatment. Compared to placebo mice, T-cell from Exendin-4-treated mice was manifested with increased proliferation, while decreased IL-2 secretion and lower ratio of IL-4/IFN-γ at 4 h pb. However, at 24 h pb, it showed decreased proliferation, while increased IL-2 secretion and higher ratio of IL-4/IFN-γ. Exendin-4 could elicit higher circulating IL-6 and IL-10 levels at 4 h pb, which were pronounced in the lung at 24 h pb. In the meanwhile, severe inflammation could be found in the pancreas. At 24 h pb, the numbers of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling or caspase-3 positive cells and the apoptosis of CD3+ T-cells were significantly increased in the spleens of Exendin-4 mice relative to placebo mice.

CONCLUSIONS

These data support a pathogenic role of Exendin-4 signaling during thermal injury, warning against its clinical application in acute insults.

Stress-Induced Hyperglycemia: Consequences and Management

Hyperglycemia during stress is a common occurrence seen in patients admitted to the hospital. It is defined as a blood glucose level above 180mg/dl in patients without pre-existing diabetes. Stress-induced hyperglycemia (SIH) occurs due to an illness that leads to insulin resistance and decreased insulin secretion. Such a mechanism causes elevated blood glucose and produces a complex state to manage with external insulin. This article compiles various studies to explain the development and consequences of SIH in the critically ill that ultimately lead to an increase in mortality while also discussing the dire impact of SIH on certain acute illnesses like myocardial infarction and ischemic stroke. It also evaluates multiple studies to understand the management of SIH with insulin and proper nutritional therapy in the hospitalized patients admitted to the Intensive care unit (ICU) alongside the non-critical care unit. While emphasizing the diverse effects of improper control of SIH in the hospital, this article elucidates and discusses the importance of formulating a discharge plan due to an increased risk of type 2 diabetes in the recovered.

The impact of a modified carbohydrate formula, and its constituents, on glycaemic control and inflammatory markers: A nested mechanistic sub-study

BACKGROUND

Hyperglycaemia occurs frequently in the critically ill. Dietary intake of advanced glycation end-products (AGEs), specifically Nε-(carboxymethyl)lysine (CML), may exacerbate hyperglycaemia through perturbation of insulin sensitivity. The present study aimed to determine whether the use of nutritional formulae, with varying AGE loads, affects the amount of insulin administered and inflammation.

METHODS

Exclusively tube fed patients (n = 35) were randomised to receive Nutrison Protein Plus Multifibre®, Diason® or Glucerna Select®. Insulin administration was standardised according to protocol based on blood glucose (<10 mmol L^-1 ). Samples were obtained at randomisation and 48 h later. AGEs in nutritional formula, plasma and urine were measured using mass spectrometry. Plasma inflammatory markers were measured using an enzyme-linked immunosorbent assay and multiplex bead-based assays.

RESULTS

AGE concentrations of CML in nutritional formulae were greatest with delivery of Nutrison Protein Plus® (mean [SD]; 6335 pmol mol^-1 [2436]) compared to Diason® (4836 pmol mol^-1 [1849]) and Glucerna Select® (4493 pmol mol^-1 [1829 pmol mol^-1 ]) despite patients receiving similar amounts of energy (median [interquartile range]; 12 MJ [8.2-13.7 MJ], 11.5 MJ [8.3-14.5 MJ], 11.5 MJ [8.3-14.5 MJ]). More insulin was administered with Nutrison Protein Plus® (2.47 units h^-1 [95% confidence interval (CI) = 1.57-3.37 units h^-1 ]) compared to Diason® (1.06 units h^-1 [95% CI = 0.24-1.89 units h^-1 ]) or Glucerna Select® (1.11 units h^-1 [95% CI = 0.25-1.97 units h^-1 ]; p = 0.04). Blood glucose concentrations were similar. There were associations between greater insulin administration and reductions in circulating interleukin-6 (r = -0.46, p < 0.01), tumour necrosis factor-α (r = -0.44, p < 0.05), high sensitivity C-reactive protein (r = -0.42, p < 0.05) and soluble receptor for advanced glycation end-products (r = -0.45, p < 0.01) concentrations.

CONCLUSIONS

The administration of greater AGE load in nutritional formula potentially increases the amount of insulin required to maintain blood glucose within a normal range during critical illness. There was an inverse relationship between exogenous insulin and plasma inflammatory markers.

A Pilot Double-Blind Placebo-Controlled Randomized Clinical Trial to Investigate the Effects of Early Enteral Nutrients in Sepsis

Supplemental Digital Content is available in the text.

Preclinical studies from our laboratory demonstrated therapeutic effects of enteral dextrose administration in the acute phase of sepsis, mediated by the intestine-derived incretin hormone glucose-dependent insulinotropic peptide. The current study investigated the effects of an early enteral dextrose infusion on systemic inflammation and glucose metabolism in critically ill septic patients.

The correlation between gastric residual volumes and markers of gastric emptying: a post-hoc analysis of a randomized clinical trial

BACKGROUND

The correlation between gastric residual volumes (GRV) and markers of gastric emptying (GE) in critically ill patients is unclear. This is especially true for ICU surgical patients as they are underrepresented in previous studies.

METHODS

We conducted a post-hoc analysis of a multicenter trial that investigated the effectiveness of a promotility drug in increasing enteral nutrition intake. Pharmacokinetic markers of GE [3-O-methylglucose (3-OMG) and acetaminophen] were correlated with GRV measurements. High-GRV was defined as one episode of >400 mL or two consecutive episodes of >250 mL, and delayed GE was defined as <20^th percentile of the pharmacokinetic GE marker that had the strongest correlation with GE.

RESULTS

Out of 77 patients, 8 (10.4%) had high-GRV, and 15 (19.5%) had delayed GE. 3-OMG concentration at 60 mins had the strongest correlation with GRV (Rho: - 0.631), and high-GRV had low sensitivity (46.7%) but high specificity (98.4%) in discriminating delayed GE. The positive (87.5%) and negative (88.4%) predictive values were similar. There was a small sample of surgical patients (n = 14, 18.2%), and they had a significantly higher incidence of high-GRV (29% vs 6%, P: 0.032) and a trend towards delayed GE (36% vs 16%, p: 0.132) when compared to medical patients.

CONCLUSION

GRV reflects GE, and high-GRV is an acceptable surrogate marker of delayed GE. Based on our preliminary observation, surgical patients may have a higher risk of high-GRV and delayed GE. In summary, GRV should be monitored to determine if complex investigations or therapeutic interventions are warranted. This article is protected by copyright. All rights reserved.

Safety of Semaglutide

The glucagon-like peptide-1 receptor agonist (GLP-1RA) semaglutide is the most recently approved agent of this drug class, and the only GLP-1RA currently available as both subcutaneous and oral formulation. While GLP-1RAs effectively improve glycemic control and cause weight loss, potential safety concerns have arisen over the years. For semaglutide, such concerns have been addressed in the extensive phase 3 registration trials including cardiovascular outcome trials for both subcutaneous (SUSTAIN: Semaglutide Unabated Sustainability in Treatment of Type 2 Diabetes) and oral (PIONEER: Peptide InnOvatioN for the Early diabEtes tReatment) semaglutide and are being studied in further trials and registries, including real world data studies. In the current review we discuss the occurrence of adverse events associated with semaglutide focusing on hypoglycemia, gastrointestinal side effects, pancreatic safety (pancreatitis and pancreatic cancer), thyroid cancer, gallbladder events, cardiovascular aspects, acute kidney injury, diabetic retinopathy (DRP) complications and injection-site and allergic reactions and where available, we highlight potential underlying mechanisms. Furthermore, we discuss whether effects are specific for semaglutide or a class effect. We conclude that semaglutide induces mostly mild-to-moderate and transient gastrointestinal disturbances and increases the risk of biliary disease (cholelithiasis). No unexpected safety issues have arisen to date, and the established safety profile for semaglutide is similar to that of other GLP-1RAs where definitive conclusions for pancreatic and thyroid cancer cannot be drawn at this point due to low incidence of these conditions. Due to its potent glucose-lowering effect, patients at risk for deterioration of existing DRP should be carefully monitored if treated with semaglutide, particularly if also treated with insulin. Given the beneficial metabolic and cardiovascular actions of semaglutide, and the low risk for severe adverse events, semaglutide has an overall favorable risk/benefit profile for patient with type 2 diabetes.

Measurement of serial serum total and acylated ghrelin levels in critically ill patients: A prospective and observational pilot study

BACKGROUND

Ghrelin is a hormone that regulates appetite and energy metabolism. The change of serial serum total and acylated ghrelin levels during hospital stays of critical patients are unknown. In addition, the relationship of this change with the clinical results of patients in the intensive care unit (ICU) is also unknown. The aim of this study was to determine serum total and acylated ghrelin levels serially in critically ill patients.

METHODS

This prospective study was performed in the ICU. Patients who were >18 years old and stayed in ICU for >48 h were included in the study. Serum total and acylated ghrelin concentrations were measured at baseline in all participants and serially on the 2nd, 5th, and 10th day after entry into the study in those who remained in the ICU.

RESULTS

A total of 60 participants were included. The mean age was 56 ± 21 years. (Baseline, 2nd, 5th, and 10th day median serum total ghrelin levels were 3551 (1651-3995), 3485.20 (1379-4071), 3359 (1167-3919), and 3355 pg/ml (2207-3843), respectively. Baseline, 2nd, 5th, and 10th day acylated ghrelin levels were 47 (0-673), 50 (0-730), 73 (0-808), and 125 pg/ml (0-689), respectively. There was no significant difference between total ghrelin/acylated ghrelin levels and mortality (P > .05). ICU mortality was 30%.

CONCLUSION

Ghrelin levels were decreased slightly and acylated ghrelin levels increased substantially over time in critically ill patients. There were no differences between serum total ghrelin/acylated ghrelin levels and ICU mortality .

Effects of GLP-1 and Its Analogs on Gastric Physiology in Diabetes Mellitus and Obesity

The processing of proglucagon in intestinal L cells results in the formation of glucagon, GLP-1, and GLP-2. The GLP-1 molecule becomes active through the effect of proconvertase 1, and it is inactivated by dipeptidyl peptidase IV (DPP-IV), so that the half-life of endogenous GLP-1 is 2-3 min. GLP-1 stimulates insulin secretion from β cells in the islets of Langerhans. Human studies show that infusion of GLP-1 results in slowing of gastric emptying and increased fasting and postprandial gastric volumes. Retardation of gastric emptying reduces postprandial glycemia. Exendin-4 is a peptide agonist of the GLP-1 receptor that promotes insulin secretion. Chemical modifications of exendin-4 and GLP-1 molecules have been accomplished to prolong the half-life of GLP-1 agonists or analogs. This chapter reviews the effects of GLP-1-related drugs used in treatment of diabetes or obesity on gastric motor functions, chiefly gastric emptying. The literature shows that diverse methods have been used to measure effects of the GLP-1-related drugs on gastric emptying, with most studies using the acetaminophen absorption test which essentially measures gastric emptying of liquids during the first hour and capacity to absorb the drug over 4-6 h, expressed as AUC. The most valid measurements by scintigraphy (solids or liquids) and acetaminophen absorption at 30 or 60 min show that GLP-1-related drugs used in diabetes or obesity retard gastric emptying, and this is associated with reduced glycemia and variable effects on food intake and appetite. GLP-1 agonists and analogs are integral to the management of patients with type 2 diabetes mellitus and obesity. The effects on gastric emptying are reduced with long-acting preparations or long-term use of short-acting preparations as a result of tachyphylaxis. The dual agonists targeting GLP-1 and another receptor (GIP) do not retard gastric emptying, based on reports to date. In summary, GLP-1 agonists and analogs are integral to the management of patients with type 2 diabetes mellitus and obesity, and their effects are mediated, at least in part, by retardation of gastric emptying.

Blinded, Double-Dummy, Parallel-Group, Phase 2a Randomized Clinical Trial to Evaluate the Efficacy and Safety of a Highly Selective 5-Hydroxytryptamine Type 4 Receptor Agonist in Critically Ill Patients With Enteral Feeding Intolerance

Background

Delayed gastric emptying is the leading cause of enteral feeding intolerance (EFI) in critical illness. This phase 2a study compared TAK‐954, a selective agonist of 5‐hydroxytryptamine type 4 receptors, with metoclopramide in critically ill patients with EFI (NCT01953081).

Methods

A blinded, double‐dummy trial was conducted in mechanically ventilated patients with EFI (>200 mL gastric residual volume within 24 hours before randomization). Patients were randomized to receive either 0.5 mg intravenous TAK‐954 over 1 hour then 0.9% saline injection 4 times/d (sham metoclopramide) or the active comparator 10 mg intravenous metoclopramide 4 times/d and a 1‐hour 0.9% saline infusion. After initial dosing, participants received a radiolabeled meal of liquid nutrient (Ensure; 106 kcal), and gastric emptying was measured (scintigraphy). Adverse events (AEs) were recorded from the time of consent through to day 5; serious AEs were collected to day 30.

Results

Thirteen patients (TAK‐954, n = 7; metoclopramide, n = 6) participated. Five patients in the TAK‐954 group and 4 in the metoclopramide group experienced AEs (2 and 3, respectively, were serious). All AEs except 1 (diarrhea in the metoclopramide group) were considered unrelated to study drug. Following treatment, a greater proportion of patients receiving TAK‐954 had normal gastric retention (<13% retention at 180 minutes) than those receiving metoclopramide (6/7 vs 3/6 patients, respectively).

Conclusion

A single dose of 0.5 mg intravenous TAK‐954 appears to have at least similar efficacy in accelerating gastric emptying to multiple doses of 10 mg metoclopramide and was not associated with increased AEs.

Therapeutic Effects of Endogenous Incretin Hormones and Exogenous Incretin-Based Medications in Sepsis

BACKGROUND

Sepsis, a complex disorder characterized by a dysregulated immune response to an inciting infection, affects over one million Americans annually. Dysglycemia during sepsis hospitalization confers increased risk of organ dysfunction and death, and novel targets for the treatment of sepsis and maintenance of glucose homeostasis are needed. Incretin hormones are secreted by enteroendocrine cells in response to enteral nutrients and potentiate insulin release from pancreatic β cells in a glucose-dependent manner, thereby reducing the risk of insulin-induced hypoglycemia. Incretin hormones also reduce systemic inflammation in preclinical studies, but studies of incretins in the setting of sepsis are limited.

METHODS

In this bench-to-bedside mini-review, we detail the evidence to support incretin hormones as a therapeutic target in patients with sepsis. We performed a PubMed search using the medical subject headings "incretins," "glucagon-like peptide-1," "gastric inhibitory peptide," "inflammation," and "sepsis."

RESULTS

Incretin-based therapies decrease immune cell activation, inhibit proinflammatory cytokine release, and reduce organ dysfunction and mortality in preclinical models of sepsis. Several small clinical trials in critically ill patients have suggested potential benefit in glycemic control using exogenous incretin infusions, but these studies had limited power and were performed in mixed populations. Further clinical studies examining incretins specifically in septic populations are needed.

CONCLUSIONS

Targeting the incretin hormone axis in sepsis may provide a means of not only promoting euglycemia in sepsis but also attenuating the proinflammatory response and improving clinical outcomes.

The use of GLP-1 receptor agonists in hospitalised patients: An untapped potential

In the outpatient setting, glucagon-like peptide-1 (GLP-1) receptor agonists have proved to be highly efficacious drugs that provide glycaemic control with a low risk of hypoglycaemia. These characteristics make GLP-1 receptor agonists attractive agents to treat dysglycaemia in perioperative or high-dependency hospital settings, where glycaemic variability and hyperglycaemia are associated with poor prognosis. GLP-1 also has a direct action on the myocardium and vasculature-which may be advantageous in the immediate aftermath of a vascular insult. This is a narrative review of the work in this area. The aim was to determine the populations of hospitalised patients being evaluated and the clinical and mechanistic end-points tested, with the institution of GLP-1 therapy in hospital. We searched the PubMed, Embase, and Google scholar databases, combining the term "glucagon-like peptide 1" OR "GLP-1" OR "incretin" OR "liraglutide" OR "exenatide" OR "lixisenatide" OR "dulaglutide" OR "albiglutide" AND "inpatient" OR "hospital" OR "perioperative" OR "postoperative" OR "surgery" OR "myocardial infarction" OR "stroke" OR "cerebrovascular disease" OR "transient ischaemic attack" OR "ICU" OR "critical care" OR "critical illness" OR "CCU" OR "coronary care unit." Pilot studies were reported in the fields of acute stroke, cardiac resuscitation, coronary care, and perioperative care that showed advantages for GLP-1 therapy, with normalisation of glucose, lower glucose variability, and lower risk of hypoglycaemia. Animal and human studies have reported improvements in myocardial performance when given acutely after vascular insult or surgery, but these have yet to be translated into randomised clinical trials.

Gastric Emptying in Patients With Well-Controlled Type 2 Diabetes Compared With Young and Older Control Subjects Without Diabetes

CONTEXT

Gastric emptying is a major determinant of postprandial glycemia and is often delayed in long-standing, complicated type 2 diabetes mellitus (T2DM). However, there is little information about gastric emptying in well-controlled T2DM.

OBJECTIVE

To evaluate the rate of gastric emptying in community-based patients with relatively well-controlled T2DM compared with young and older control subjects without diabetes.

PARTICIPANTS AND DESIGN

A total of 111 patients with T2DM managed by diet (n = 52) or metformin monotherapy (n = 59) (HbA1c 6.6 ± 0.1%/49.0 ± 0.9 mmol/mol), 18 age- and body mass index (BMI)-matched older subjects without diabetes, and 15 young healthy subjects consumed a standardized mashed potato meal (368.5 kcal) containing 100 μL 13C-octanoic acid. Gastric emptying (by breath test) and blood glucose were evaluated over 240 minutes.

RESULTS

Gastric emptying was slower in the older than in the young subjects without diabetes (2.3 ± 0.1 vs 3.0 ± 0.1 kcal/min, P = 0.0008). However, relative to the age- and BMI-matched subjects without diabetes, gastric emptying (2.8 ± 0.1 kcal/min) was faster in patients with T2DM (P = 0.0005). Furthermore, gastric emptying was faster in the metformin-treated (3.0 ± 0.1 kcal/min) than in the diet-controlled (2.7 ± 0.1 kcal/min) patients with T2DM (P = 0.011), although there were no differences in age, BMI, HbA1c, or the duration of known diabetes. The increments in blood glucose (at t = 30 and 60 minutes and the incremental area under the curve during t = 0 to 120 minutes) after the meal were related directly to the rate of gastric emptying in the subjects with T2DM regardless of treatment with or without metformin (P < 0.05 each).

CONCLUSIONS

Gastric emptying is slowed with aging but otherwise is relatively more rapid in patients with well-controlled T2DM. This provides a strong rationale for slowing gastric emptying to improve postprandial glycemic control in these patients.

Persistently Elevated Glucagon-Like Peptide-1 Levels among Critically Ill Surgical Patients after Sepsis and Development of Chronic Critical Illness and Dismal Long-Term Outcomes

BACKGROUND

Glucagon-like peptide-1 (GLP-1) is a gut-derived incretin hormone that stimulates insulin secretion, cellular glucose uptake, and has immune-regulatory functions. Glucagon-like peptide-1 is markedly altered after trauma and sepsis, but the implications remain unclear.

STUDY DESIGN

We performed an analysis of a prospective, longitudinal cohort study of critically ill surgical patients with sepsis. Patient characteristics and clinical data were collected, as well as peripheral blood sampling for biomarker analysis, out to 28 days after sepsis onset. We prospectively adjudicated sepsis diagnosis, severity, clinical outcomes, and 6-month follow-up.

RESULTS

The cohort included 157 septic surgical patients with significant physiologic derangement (Maximum Sequential Organ Failure Assessment [SOFA] score 8, interquartile range [IQR] 4 to 11), a high rate of multiple organ failure (50.3%), and septic shock (24.2%). Despite high disease severity, both early death (<14 days; n = 4, 2.9%) and overall inpatient mortality were low (n = 12, 7.6%). However, post-discharge 6-month mortality was nearly 3-fold higher (19.7%). Both GLP-1 and interleukin [IL]-6 levels were significantly elevated for 21 days (p ≤ 0.01) in patients who developed chronic critical illness (CCI) compared with patients with a rapid recovery. Elevated GLP-1 at 24 hours was a significant independent predictor for the development of CCI after controlling for IL-6 and glucose levels (p = 0.027), and at day 14 for death or severe functional disability at 6 months (WHO/Zubrod score 4-5, p = 0.014).

CONCLUSIONS

Elevated GLP-1 within 24 hours of sepsis is a predictor of early death or persistent organ dysfunction. Among early survivors, persistently elevated GLP-1 levels at day 14 are strongly predictive of death or severe functional disability at 6 months. Persistently elevated GLP-1 levels may be a marker of a nonresolving catabolic state that is associated with muscle wasting and dismal outcomes after sepsis and chronic critical illness.

Incident Diabetes in Survivors of Critical Illness and Mechanisms Underlying Persistent Glucose Intolerance: A Prospective Cohort Study

OBJECTIVES

Stress hyperglycemia occurs in critically ill patients and may be a risk factor for subsequent diabetes. The aims of this study were to determine incident diabetes and prevalent prediabetes in survivors of critical illness experiencing stress hyperglycemia and to explore underlying mechanisms.

DESIGN

This was a prospective, single center, cohort study. At admission to ICU, hemoglobin A1c was measured in eligible patients. Participants returned at 3 and 12 months after ICU admission and underwent hemoglobin A1c testing and an oral glucose tolerance test. Blood was also collected for hormone concentrations, whereas gastric emptying was measured via an isotope breath test. β-cell function was modeled using standard techniques.

SETTING

Tertiary-referral, mixed medical-surgical ICU.

PATIENTS

Consecutively admitted patients who developed stress hyperglycemia and survived to hospital discharge were eligible.

MEASUREMENTS AND MAIN RESULTS

Consent was obtained from 40 patients (mean age, 58 yr [SD, 10], hemoglobin A1c 36.8 mmol/mol [4.9 mmol/mol]) with 35 attending the 3-month and 26 the 12-month visits. At 3 months, 13 (37%) had diabetes and 15 (43%) had prediabetes. At 12 months, seven (27%) participants had diabetes, whereas 11 (42%) had prediabetes. Mean hemoglobin A1c increased from baseline during the study: +0.7 mmol/mol (-1.2 to 2.5 mmol/mol) at 3 months and +3.3 mmol/mol (0.98-5.59 mmol/mol) at 12 months (p = 0.02). Gastric emptying was not significantly different across groups at either 3 or 12 months.

CONCLUSIONS

Diabetes and prediabetes occur frequently in survivors of ICU experiencing stress hyperglycemia. Based on the occurrence rate observed in this cohort, structured screening and intervention programs appear warranted.

Exendin-4 Exacerbates Burn-Induced Morbidity in Mice by Activation of the Sympathetic Nervous System

Background

Although glucagon-like peptide 1- (GLP-1-) based therapy of hyperglycemia in burn injury has shown great potential in clinical trials, its safety is seldom evaluated. We hypothesize that exendin-4, a GLP-1 analogue, might affect the immune response via the activation of the sympathetic nervous system in burn injury.

Methods

Male Balb/c mice were subjected to sham or thermal injury of 15% total body surface area. Exendin-4 on T cell function in vitro was examined in cultured splenocytes in the presence of β-adrenoceptor antagonist propranolol (1 nmol/L) or GLP-1R antagonist exendin (9-39) (1 μmol/L), whereas its in vivo effect was determined by i.p. injection of exendin-4 (2.4 nmol/kg) in mice. To further elucidate the sympathetic mechanism, propranolol (30 mg/kg) or vehicle was applied 30 min prior to injury.

Results

Although the exacerbated burn-induced mortality by exendin-4 was worsened by propranolol pretreatment, the inhibition of T cell proliferation by exendin-4 in vitro could be restored by propranolol instead of exendin (9-39). However, a Th2 switch by exendin-4 in vitro could only be reversed by exendin (9-39). Likewise, the inhibition of splenic T cell function and NFAT activity by exendin-4 in vivo was restored by propranolol. By contrast, the increased splenic NF-κB translocation by exendin-4 in vivo was potentiated by propranolol in sham mice but suppressed in burn mice. Accordingly, propranolol abrogated the heightened inflammatory response in the lung and the accelerated organ injuries by exendin-4 in burn mice. On the contrary, a Th2 switch and higher serum levels of inflammatory mediators by exendin-4 were potentiated by propranolol in burn mice. Lastly, exendin-4 raised serum stress hormones which could be remarkably augmented by propranolol.

Conclusions

Exendin-4 suppresses T cell function and promotes organ inflammation through the activation of the sympathetic nervous system, while elicits Th2 switch via GLP-1R in burn injury.

Pleiotropic Effects of GLP-1 and Analogs on Cell Signaling, Metabolism, and Function

The incretin hormone Glucagon-Like Peptide-1 (GLP-1) is best known for its "incretin effect" in restoring glucose homeostasis in diabetics, however, it is now apparent that it has a broader range of physiological effects in the body. Both in vitro and in vivo studies have demonstrated that GLP-1 mimetics alleviate endoplasmic reticulum stress, regulate autophagy, promote metabolic reprogramming, stimulate anti-inflammatory signaling, alter gene expression, and influence neuroprotective pathways. A substantial body of evidence has accumulated with respect to how GLP-1 and its analogs act to restore and maintain normal cellular functions. These findings have prompted several clinical trials which have reported GLP-1 analogs improve cardiac function, restore lung function and reduce mortality in patients with obstructive lung disease, influence blood pressure and lipid storage, and even prevent synaptic loss and neurodegeneration. Mechanistically, GLP-1 elicits its effects via acute elevation in cAMP levels, and subsequent protein kinase(s) activation, pathways well-defined in pancreatic β-cells which stimulate insulin secretion in conjunction with elevated Ca2+ and ATP. More recently, new studies have shed light on additional downstream pathways stimulated by chronic GLP-1 exposure, findings which have direct relevance to our understanding of the potential therapeutic effects of longer lasting analogs recently developed for clinical use. In this review, we provide a comprehensive description of the diverse roles for GLP-1 across multiple tissues, describe downstream pathways stimulated by acute and chronic exposure, and discuss novel pleiotropic applications of GLP-1 mimetics in the treatment of human disease.

Systematic review of incretin therapy during peri-operative and intensive care

Background

Glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP) are incretin hormones. By lowering blood glucose in a glucose-dependent manner, incretin-based therapies represent a novel and promising intervention to treat hyperglycaemia in hospital settings. We performed a systematic review of the literature for all current applications of incretin-based therapies in the peri-operative and critical care settings.

Methods

We searched MEDLINE, the Cochrane Library, and Embase databases for all randomised controlled trials using exogenous GLP-1, GLP-1 receptor agonists, exogenous GIP and dipeptidyl peptidase IV inhibitors in the setting of adult peri-operative care or intensive care. We defined no comparator treatment. Outcomes of interest included blood glucose, frequency of hypoglycaemia and insulin administration.

Results

Of the 1190 articles identified during the initial literature search, 38 fulfilled criteria for full-text review, and 19 single-centre studies were subsequently included in the qualitative review. Of the 18 studies reporting glycaemic control, improvement was reported in 15, defined as lower glucose concentrations in 12 and as reduced insulin administration (with similar glucose concentrations) in 3. Owing to heterogeneity, meta-analysis was possible only for the outcome of hypoglycaemia. This revealed an incidence of 7.4% in those receiving incretin-based therapies and 6.8% in comparator groups (P = 0.94).

Conclusions

In small, single-centre studies, incretin-based therapies lowered blood glucose and reduced insulin administration without increasing the incidence of hypoglycaemia.

Trial registration

PROSPERO, CRD42017071926.

Electronic supplementary material

The online version of this article (10.1186/s13054-018-2197-4) contains supplementary material, which is available to authorized users.

Pathophysiology and Treatment of Gastrointestinal Motility Disorders in the Acutely Ill

Gastrointestinal dysmotility causes delayed gastric emptying, enteral feed intolerance, and functional obstruction of the small and large intestine, the latter functional obstructions being frequently termed ileus and Ogilvie syndrome, respectively. In addition to meticulous supportive care, drug therapy may be appropriate in certain situations. There is, however, considerable variation among individuals regarding what gastric residual volume identifies gastric dysmotility and would encourage use of a promotility drug. While the administration of either metoclopramide or erythromycin is supported by evidence it appears that, dual-drug therapy (erythromycin and metoclopramide) reduces the rate of treatment failure. There is a lack of evidence to guide drug therapy of ileus, but neither erythromycin nor metoclopramide appear to have a role. Several drugs, including ghrelin agonists, highly selective 5-hydroxytryptamine receptor agonists, and opiate antagonists are being studied in clinical trials. Neostigmine, when infused at a relatively slow rate in patients receiving continuous hemodynamic monitoring, may alleviate the need for endoscopic decompression in some patients.

Clinical Effectiveness of Intravenous Exenatide Infusion in Perioperative Glycemic Control after Coronary Artery Bypass Graft Surgery

Background

We aimed to assess the clinical effectiveness of intravenous exenatide compared to insulin in perioperative blood glucose control in coronary artery bypass grafting surgery patients.

Methods

Patients more than 18 yr old admitted for elective coronary artery bypass grafting were included in a phase II/III nonblinded randomized superiority trial. Current insulin use and creatinine clearance of less than 60 ml/min were exclusion criteria. Two groups were compared: the exenatide group, receiving exenatide (1-h bolus of 0.05 µg/min followed by a constant infusion of 0.025 µg/min), and the control group, receiving insulin therapy. The blood glucose target range was 100 to 139 mg/dl. The primary outcome was the proportion of patients who spent at least 50% of the study period within the target range. The consumption of insulin (Cinsulin) and the time to start insulin (Tinsulin) were compared between the two groups.

Results

In total, 53 and 51 patients were included and analyzed in the exenatide and control groups, respectively (age: 70 ± 9 vs. 68 ± 11 yr; diabetes mellitus: 12 [23%] vs. 10 [20%]). The primary outcome was observed in 38 (72%) patients in the exenatide group and in 41 (80%) patients in the control group (odds ratio [95% CI] = 0.85 [0.34 to 2.11]; P = 0.30). Cinsulin was significantly lower (60 [40 to 80] vs. 92 [63 to 121] U, P &lt; 0.001), and Tinsulin was significantly longer (12 [7 to 16] vs. 7 [5 to 10] h, P = 0.02) in the exenatide group.

Conclusions

Exenatide alone at the dose used was not enough to achieve adequate blood glucose control in coronary artery bypass grafting patients, but it reduces overall consumption of insulin and increases the time to initiation of insulin.

Is There a Role for Enterohormones in the Gastroparesis of Critically Ill Patients?

OBJECTIVES

Delayed gastric emptying occurs in critically ill patients and impairs the delivery, digestion, and absorption of enteral feeding. A pathophysiologic role of the enterohormones peptide YY and ghrelin is supported by preclinical data. To compare the circulating plasma levels of peptide YY and ghrelin in control subjects and in critically ill patients, during feeding and fasting, and to search for a correlation with gastric emptying.

DESIGN

A prospective observational trial.

SETTINGS

Mixed ICU of an academic hospital.

SUBJECTS

Healthy volunteers and patients expected to stay in ICU for at least 3 days in whom enteral nutrition was indicated.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Plasma peptide YY and ghrelin (enzyme-linked immunosorbent assay) were measured once in 10 fasting volunteers (controls) and daily from admission until day 5 of the ICU stay in 30 critically ill patients (median [interquartile range] age 63 [57-67] yr, median [interquartile range] Acute Physiology and Chronic Health Evaluation II score 21 [14-24]). Eight patients could not be fed (fasting group). In fed patients, 13 never had a gastric residual volume higher than 250 mL (low gastric residual volume group), in contrast to the high gastric residual volume group (n = 9). The plasma levels of peptide YY did not differ between patients (6.4 [0-18.1] pg/mL) and controls (4.8 [0.3-17.7] pg/mL). Ghrelin levels were lower in patients than in control (213 [54.4-522.7] vs 1,435 [1,321.9-1,869.3] pg/mL; p < 0.05). Plasma peptide YY or ghrelin did not differ between fasting and fed patients or between the high and low gastric residual volume groups.

CONCLUSIONS

In critically ill patients, plasma concentration of ghrelin significantly differs from that of controls, irrespective of the feeding status. No correlation was found between the temporal profile of ghrelin or peptide YY plasma concentration with bedside functional assessment of gastric emptying.

Metabolic and Endocrine Considerations After Burn Injury

Severe burn injury is followed by a profound hypermetabolic response that persists up to 2 years after injury. It is mediated by up to 50-fold elevations in plasma catecholamines, cortisol, and glucagon that lead to whole-body catabolism, elevated resting energy expenditures, and multiorgan dysfunction. Modulation of the response by early excision and grafting of burn wounds, thermoregulation, control of infection, early and continuous enteral nutrition, and pharmacologic treatments aimed at mitigating physiologic derangements have markedly decreased morbidity.

Inter-regulation of gastric emptying and incretin hormone secretion: implications for postprandial glycemic control

The GI tract is central to the regulation of postprandial glycemia, with the rate of gastric emptying and the secretion of the incretin hormones, glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1, being key determinants. Gastric emptying exhibits a large interindividual variation; the latter not only accounts for differences in postprandial glycemia but also determines postprandial incretin profiles. Accordingly, the rate of gastric emptying may affect the glucose-lowering efficacy of dipeptidyl peptidase-4 inhibitors. In contrast, glucagon-like peptide-1 receptor agonists lower postprandial glycemia predominantly by their action to slow gastric emptying. This review discusses the inter-relationship between gastric emptying and the incretin axis in the context of changes in blood glucose, with an emphasis on the relevant clinical implications.

The effect of camicinal (GSK962040), a motilin agonist, on gastric emptying and glucose absorption in feed-intolerant critically ill patients: a randomized, blinded, placebo-controlled, clinical trial

Background

The promotility agents currently available to treat gastroparesis and feed intolerance in the critically ill are limited by adverse effects. The aim of this study was to assess the pharmacodynamic effects and pharmacokinetics of single doses of the novel gastric promotility agent motilin agonist camicinal (GSK962040) in critically ill feed-intolerant patients.

Methods

A prospective, randomized, double-blind, parallel-group, placebo-controlled, study was performed in mechanically ventilated feed-intolerant patients [median age 55 (19–84), 73 % male, APACHE II score 18 (5–37) with a gastric residual volume ≥200 mL]. Gastric emptying and glucose absorption were measured both pre- and post-treatment after intragastric administration of 50 mg (n = 15) camicinal and placebo (n = 8) using the ¹³C-octanoic acid breath test (BTt_1/2), acetaminophen concentrations, and 3-O-methyl glucose concentrations respectively.

Results

Following 50 mg enteral camicinal, there was a trend to accelerated gastric emptying [adjusted geometric means: pre-treatment BTt_1/2 117 minutes vs. post- treatment 76 minutes; 95 % confidence intervals (CI; 0.39, 1.08) and increased glucose absorption (AUC_240min pre-treatment: 28.63 mmol.min/L vs. post-treatment: 71.63 mmol.min/L; 95 % CI (1.68, 3.72)]. When two patients who did not have detectable plasma concentrations of camicinal were excluded from analysis, camicinal accelerated gastric emptying (adjusted geometric means: pre-treatment BTt_1/2 121 minutes vs. post-treatment 65 minutes 95 % CI (0.32, 0.91) and increased glucose absorption (AUC_240min pre-treatment: 33.04 mmol.min/L vs. post-treatment: 74.59 mmol.min/L; 95 % CI (1.478, 3.449). In those patients receiving placebo gastric emptying was similar pre- and post-treatment.

Conclusions

When absorbed, a single enteral dose of camicinal (50 mg) accelerates gastric emptying and increases glucose absorption in feed-intolerant critically ill patients.

Trial registration

The study protocol was registered with the US NIH clinicaltrials.gov on 23 December 2009 (Identifier NCT01039805).

GLP-1 based therapies: clinical implications for gastroenterologists

The gut-derived incretin hormone, glucagon-like peptide 1 (GLP-1) lowers postprandial blood glucose levels by stimulating insulin and inhibiting glucagon secretion. Two novel antihyperglycaemic drug classes augment these effects; GLP-1 receptor agonists and inhibitors of the GLP-1 degrading enzyme dipeptidyl peptidase 4. These so called GLP-1 based or incretin based drugs are increasingly used to treat type 2 diabetes, because of a low risk of hypoglycaemia and favourable effect on body weight, blood pressure and lipid profiles. Besides glucose control, GLP-1 functions as an enterogastrone, causing a wide range of GI responses. Studies have shown that endogenous GLP-1 and its derived therapies slow down digestion by affecting the stomach, intestines, exocrine pancreas, gallbladder and liver. Understanding the GI actions of GLP-1 based therapies is clinically relevant; because GI side effects are common and need to be recognised, and because these drugs may be used to treat GI disease.

Gastrointestinal actions of glucagon-like peptide-1-based therapies: glycaemic control beyond the pancreas

The gastrointestinal hormone glucagon-like peptide-1 (GLP-1) lowers postprandial glucose concentrations by regulating pancreatic islet-cell function, with stimulation of glucose-dependent insulin and suppression of glucagon secretion. In addition to endocrine pancreatic effects, mounting evidence suggests that several gastrointestinal actions of GLP-1 are at least as important for glucose-lowering. GLP-1 reduces gastric emptying rate and small bowel motility, thereby delaying glucose absorption and decreasing postprandial glucose excursions. Furthermore, it has been suggested that GLP-1 directly stimulates hepatic glucose uptake, and suppresses hepatic glucose production, thereby adding to reduction of fasting and postprandial glucose levels. GLP-1 receptor agonists, which mimic the effects of GLP-1, have been developed for the treatment of type 2 diabetes. Based on their pharmacokinetic profile, GLP-1 receptor agonists can be broadly categorized as short- or long-acting, with each having unique islet-cell and gastrointestinal effects that lower glucose levels. Short-acting agonists predominantly lower postprandial glucose excursions, by inhibiting gastric emptying and intestinal glucose uptake, with little effect on insulin secretion. By contrast, long-acting agonists mainly reduce fasting glucose levels, predominantly by increased insulin and reduced glucagon secretion, with potential additional direct inhibitory effects on hepatic glucose production. Understanding these pharmacokinetic and pharmacodynamic differences may allow personalized antihyperglycaemic therapy in type 2 diabetes. In addition, it may provide the rationale to explore treatment in patients with no or little residual β-cell function.

Interleukin-6 predicts inflammation-induced increase of Glucagon-like peptide-1 in humans in response to cardiac surgery with association to parameters of glucose metabolism

Objective

Glucagon-like peptide-1 (GLP-1) is an incretin hormone, which gets secreted in response to nutritional stimuli from the gut mediating glucose-dependent insulin secretion. Interestingly, GLP-1 was recently found to be also increased in response to inflammatory stimuli in an interleukin 6 (IL-6) dependent manner in mice. The relevance of this finding to humans is unknown but has been suggested by the presence of high circulating GLP-1 levels in critically ill patients that correlated with markers of inflammation. This study was performed to elucidate, whether a direct link exists between inflammation and GLP-1 secretion in humans.

Research design and methods

We enrolled 22 non-diabetic patients scheduled for cardiac surgery as a reproducible inflammatory stimulus with repeated blood sampling before and after surgery.

Results

Mean total circulating GLP-1 levels significantly increased in response to surgery from 25.5 ± 15.6 pM to 51.9 ± 42.7 pM which was not found in a control population. This was preceded by an early rise of IL6, which was significantly associated with GLP-1 under inflammatory but not basal conditions. Using repeated measure ANCOVA, IL6 best predicted the observed kinetics of GLP-1, followed by blood glucose concentrations and cortisol plasma levels. Furthermore, GLP-1 plasma concentrations significantly predicted endogenous insulin production as assessed by C-peptide concentrations over time, while an inverse association was found for insulin infusion rate.

Conclusion

We found GLP-1 secretion to be increased in response to inflammatory stimuli in humans, which was associated to parameters of glucose metabolism and best predicted by IL6.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-016-0330-8) contains supplementary material, which is available to authorized users.

Novel insights into the effects of diabetes on gastric motility

Recent data from the Diabetes Control and Complications Trial/Epidemiology of Diabetic Interventions and Complications cohort indicate that the disease burden of gastroparesis in diabetes remains high, consistent with the outcome of cross-sectional studies in type 1 and 2 diabetes. An improved understanding of the pathogenesis of diabetic gastroparesis at the cellular level has emerged in the last decade, particularly as a result of initiatives such as the National Institute of Health funded Gastroparesis Clinical Research Consortium in the US. Management of diabetic gastroparesis involves dietary and psychological support, attention to glycaemic control, and the use of prokinetic agents. Given that the relationship between upper gastrointestinal symptoms and the rate of gastric emptying is weak, therapies targeted specifically at symptoms, such as nausea or pain, are important. The relationship between gastric emptying and postprandial glycaemia is complex and inter-dependent. Short-acting glucagon-like peptide-1 agonists, that slow gastric emptying, can be used to reduce postprandial glycaemic excursions and, in combination with basal insulin, result in substantial reductions in glycated haemoglobin in type 2 patients.

Incretins

Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are the known incretin hormones in humans, released predominantly from the enteroendocrine K and L cells within the gut. Their secretion is regulated by a complex of integrated mechanisms involving direct contact for the activation of different chemo-sensors on the brush boarder of K and L cells and several indirect neuro-immuno-hormonal loops. The biological actions of GIP and GLP-1 are fundamental determinants of islet function and blood glucose homeostasis in health and type 2 diabetes. Moreover, there is increasing recognition that GIP and GLP-1 also exert pleiotropic extra-glycaemic actions, which may represent therapeutic targets for human diseases. In this review, we summarise current knowledge of the biology of incretin hormones in health and metabolic disorders and highlight the therapeutic potential of incretin hormones in metabolic regulation.

The Glucagon-Like Peptide 1 Receptor Agonist Exenatide Inhibits Small Intestinal Motility, Flow, Transit, and Absorption of Glucose in Healthy Subjects and Patients With Type 2 Diabetes: A Randomized Controlled Trial

The short-acting glucagon-like peptide 1 receptor agonist exenatide reduces postprandial glycemia, partly by slowing gastric emptying, although its impact on small intestinal function is unknown. In this study, 10 healthy subjects and 10 patients with type 2 diabetes received intravenous exenatide (7.5 μg) or saline (-30 to 240 min) in a double-blind randomized crossover design. Glucose (45 g), together with 5 g 3-O-methylglucose (3-OMG) and 20 MBq (99m)Tc-sulfur colloid (total volume 200 mL), was given intraduodenally (t = 0-60 min; 3 kcal/min). Duodenal motility and flow were measured using a combined manometry-impedance catheter and small intestinal transit using scintigraphy. In both groups, duodenal pressure waves and antegrade flow events were fewer, and transit was slower with exenatide, as were the areas under the curves for serum 3-OMG and blood glucose concentrations. Insulin concentrations were initially lower with exenatide than with saline and subsequently higher. Nausea was greater in both groups with exenatide, but suppression of small intestinal motility and flow was observed even in subjects with little or no nausea. The inhibition of small intestinal motor function represents a novel mechanism by which exenatide can attenuate postprandial glycemia.

Effect of Critical Illness on Triglyceride Absorption

BACKGROUND

Adequate nutrition support for critically ill patients optimizes outcome, and enteral feeding is the preferred route of nutrition. Small intestinal glucose absorption is frequently impaired in critical illness. Despite lipid being a major constituent of liquid nutrient administered, there is little information about lipid absorption during critical illness.

OBJECTIVES

To determine small intestinal lipid, as well as glucose, absorption in critical illness compared with health.

MATERIALS AND METHODS

Twenty-nine mechanically ventilated critically ill patients and 16 healthy volunteers were studied. Liquid nutrient (60 mL, 1 kcal/mL), containing 200 µL (13)C-triolein and 3 g 3-O-methyl-glucose (3-OMG), was infused directly into the duodenum at a rate of 2 kcal/min. Exhaled (13)CO2 and serum 3-OMG concentrations were measured at timed intervals over 360 minutes. Lipid absorption was measured as the cumulative percentage dose (cPDR) of (13)CO2 recovered at 360 minutes. Glucose absorption was measured as the area under the 3-OMG concentration curve. Data are median (range) and analyzed using the Mann-Whitney U and Pearson correlation tests.

RESULTS

Lipid absorption was markedly less in the critically ill (cPDR(13)CO2: patients, 22.6% [0%-100%] vs healthy participants, 40.7% [5.3%-84.7%]; P = .018). While glucose absorption was less at 60 minutes in the critically ill (3-OMG60: 13.2 [3.5-29.5] vs 21.1 [9.3-31.9] mmol/L·min; P = .003), this was not apparent at 360 minutes (3-OMG360: 92.7 [54.5-147.9] vs 107.9 [64.0-168.7] mmol/L·min; P = .126). There was no relationship between lipid and glucose absorption.

CONCLUSION

Small intestinal absorption of lipid is diminished during critical illness.

Gastric Dysmotility in Critically Ill Children: Pathophysiology, Diagnosis, and Management

OBJECTIVE

We aimed to review gastric dysmotility in critically ill children: 1) its pathophysiology, with a focus on critical care diseases and therapies that affect gastric motility, 2) diagnostic methodologies, and 3) current and future potential therapies.

DATA SOURCES

Eligible studies were identified from PubMed and MEDLINE.

STUDY SELECTION

Literature search included the following key terms: "gastric emptying," "gastric motility/dysmotility," "gastrointestinal motility/dysmotility," "nutrition intolerance," and "gastric residual volume."

DATA EXTRACTION

Studies since 1995 were extracted and reviewed for inclusion by the authors related to the physiology, pathophysiology, diagnostic methodologies, and available therapies for gastric emptying.

DATA SYNTHESIS

Delayed gastric emptying, a common presentation of gastric dysmotility, is present in up to 50% of critically ill children. It is associated with the potential for aspiration, ventilator-associated pneumonia, and inadequate delivery of enteral nutrition and may affect the efficacy of enteral medications, all of which may be result in poor patient outcomes. Gastric motility is affected by critical illness and its associated therapies. Currently available diagnostic tools to identify gastric emptying at the bedside have not been systematically studied and applied in this cohort. Gastric residual volume measurement, used as an indirect marker of delayed gastric emptying in PICUs around the world, may be inaccurate.

CONCLUSIONS

Gastric dysmotility is common in critically ill children and impacts patient safety and outcomes. However, it is poorly understood, inadequately defined, and current therapies are limited and based on scant evidence. Understanding gastric motility and developing accurate bedside measures and novel therapies for gastric emptying are highly desirable and need to be further investigated.

Measurement of gastric emptying in the critically ill

BACKGROUND & AIMS

Enteral nutrition is important in critically ill patients and is usually administered via a nasogastric tube. As gastric emptying is frequently delayed, and this compromises the delivery of nutrient, it is important that the emptying rate can be quantified.

METHODS

A comprehensive search of MEDLINE/PubMed, of English articles, from inception to 1 July 2014. References of included manuscripts were also examined for additional studies.

RESULTS

A number of methods are available to measure gastric emptying and these broadly can be categorised as direct- or indirect-test and surrogate assessments. Direct tests necessitate visualisation of the stomach contents during emptying and are unaffected by liver or kidney metabolism. The most frequently used direct modality is scintigraphy, which remains the 'gold standard'. Indirect tests use a marker that is absorbed in the proximal small intestine, so that measurements of the marker, or its metabolite measured in plasma or breath, correlates with gastric emptying. These tests include drug and carbohydrate absorption and isotope breath tests. Gastric residual volumes (GRVs) are used frequently to quantify gastric emptying during nasogastric feeding, but these measurements may be inaccurate and should be regarded as a surrogate measurement. While the inherent limitations of GRVs make them less suitable for research purposes they are often the only technique that is available for clinicians at the bedside.

CONCLUSIONS

Each of the available techniques has its strength and limitations. Accordingly, the choice of gastric emptying test is dictated by the particular requirement(s) and expertise of the investigator or clinician.

The potential role of incretin therapy in the hospital setting

Hyperglycemia has been associated with increased morbidity and mortality in hospitalized patients. Insulin has traditionally been the drug of choice for managing hyperglycemia in this setting, but carries a significant risk of hypoglycemia. Incretin-based therapies, including glucagon-like peptide-1, glucagon-like peptide-1 receptor agonists and dipeptidyl peptidase-4 inhibitors, have potential use in the hospital. These agents have a relatively low risk of hypoglycemia, favorable short-term side effect profile, and can be used alone or in combination with insulin. Several small studies have supported the safety and efficacy of incretin therapies in the inpatient setting with the majority of data coming from the intensive care setting. Large-scale clinical studies are needed to further evaluate the potential role of incretins in the management of inpatient hyperglycemia.