Hypoglycaemia and gastric emptying

Incretin-based therapies for the management of cardiometabolic disease in the clinic: Past, present, and future

Among newer classes of drugs for type 2 diabetes mellitus (T2DM), glucagon-like peptide 1 receptor agonists (GLP-1 RAs) are incretin-based agents that lower both blood sugar levels and promote weight loss. They do so by activating pancreatic GLP-1 receptors (GLP-1R) to promote glucose-dependent insulin release and inhibit glucagon secretion. They also act on receptors in the brain and gastrointestinal tract to suppress appetite, slow gastric emptying, and delay glucose absorption. Phase 3 clinical trials have shown that GLP-1 RAs improve cardiovascular outcomes in the setting of T2DM or overweight/obesity in people who have, or are at high risk of having atherosclerotic cardiovascular disease. This is largely driven by reductions in ischemic events, although emerging evidence also supports benefits in other cardiovascular conditions, such as heart failure with preserved ejection fraction. The success of GLP-1 RAs has also seen the evolution of other incretin therapies. Tirzepatide has emerged as a dual glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 RA, with more striking effects on glycemic control and weight reduction than those achieved by isolated GLP-1R agonism alone. This consists of lowering glycated hemoglobin levels by more than 2% and weight loss exceeding 15% from baseline. Here, we review the pharmacological properties of GLP-1 RAs and tirzepatide and discuss their clinical effectiveness for T2DM and overweight/obesity, including their ability to reduce adverse cardiovascular outcomes. We also delve into the mechanistic basis for these cardioprotective effects and consider the next steps in implementing existing and future incretin-based therapies for the broader management of cardiometabolic disease.

Considerations for medical nutrition therapy management of the critically ill patient with hematological malignancies: A narrative review

Patients with hematological malignancies (HMs) are more frequently admitted now than in the past to the intensive care unit (ICU) due to more aggressive approaches in primary therapy of HMs and the need for critical care support. Pathophysiological alterations derived from HMs and the different hematological therapies, such as chemotherapy, negatively affect gastrointestinal (GI) function, metabolism, and nutrition status. Further, malnutrition strongly influences outcomes and tolerance of the different hematological therapies. In consequence, these critically ill patients frequently present with malnutrition and pathophysiological alterations that create challenges for the delivery of medical nutrition therapy (MNT) in the ICU. Frequent screening, gauging tolerance, and monitoring nutrition status are mandatory to provide individualized MNT and achieve nutrition objectives. The present review discusses how HM impact GI function and nutrition status, the importance of MNT in patients with HM, and specific considerations for guidance in providing adequate MNT to these patients when admitted to the ICU.

Postprandial plasma GLP-1 levels are elevated in individuals with postprandial hypoglycaemia following Roux-en-Y gastric bypass - a systematic review

BACKGROUND AND AIMS

Bariatric surgery is the most effective treatment in individuals with obesity to achieve remission of type 2 diabetes. Post-bariatric surgery hypoglycaemia occurs frequently, and management remains suboptimal, because of a poor understanding of the underlying pathophysiology. The glucoregulatory hormone responses to nutrients in individuals with and without post-bariatric surgery hypoglycaemia have not been systematically examined.

MATERIALS AND METHODS

The study protocol was prospectively registered with PROSPERO. PubMed, EMBASE, Web of Science and the Cochrane databases were searched for publications between January 1990 and November 2021 using MeSH terms related to post-bariatric surgery hypoglycaemia. Studies were included if they evaluated individuals with post-bariatric surgery hypoglycaemia and included measurements of plasma glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), insulin, C-peptide and/or glucagon concentrations following an ingested nutrient load. Glycated haemoglobin (HbA1c) was also evaluated. A random-effects meta-analysis was performed, and Hedges' g (standardised mean difference) and 95% confidence intervals were reported for all outcomes where sufficient studies were available. The τ2 estimate and I2 statistic were used as tests for heterogeneity and a funnel plot with the Egger regression-based test was used to evaluate for publication bias.

RESULTS

From 377 identified publications, 12 were included in the analysis. In all 12 studies, the type of bariatric surgery was Roux-en-Y gastric bypass (RYGB). Comparing individuals with and without post-bariatric surgery hypoglycaemia following an ingested nutrient load, the standardised mean difference in peak GLP-1 was 0.57 (95% CI, 0.32, 0.82), peak GIP 0.05 (-0.26, 0.36), peak insulin 0.84 (0.44, 1.23), peak C-peptide 0.69 (0.28, 1.1) and peak glucagon 0.05 (-0.26, 0.36). HbA1c was less in individuals with hypoglycaemia - 0.40 (-0.67, -0.12). There was no evidence of substantial heterogeneity in any outcome except for peak insulin: τ2 = 0.2, I2 = 54.3. No publication bias was evident.

CONCLUSION

Following RYGB, postprandial peak plasma GLP-1, insulin and C-peptide concentrations are greater in individuals with post-bariatric surgery hypoglycaemia, while HbA1c is less. These observations support the concept that antagonism of GLP-1 would prove beneficial in the management of individuals with hypoglycaemia following RYGB.PROSPERO Registration Number: CRD42021287515.

The role of gastric emptying in glucose homeostasis and defense against hypoglycemia: Innocent bystander or partner in crime?

Maintenance of plasma glucose (PG) homeostasis is due to a complex network system. Even a minor fall in PG activates multiple neuroendocrine actions promoting hormonal, metabolic and behavioral responses, which prevent and ultimately recover hypoglycemia, primarily neuroglycopenia. Among these responses, gastric emptying (GE) plays an important role by coordinated mechanisms which regulate transit and absorption of nutrients through the small intestine. A bidirectional relationship between GE and glycemia has been established: GE may explain the up to 30-40 % variance in glycemic response following a carbohydrate-rich meal. In addition, acute and chronic hyperglycemia induce deceleration of GE after meals. Hypoglycemia accelerates GE, but its role in counterregulation has been poorly investigated. The role of GE as a counterregulatory mechanism has been confirmed in pathophysiological conditions, such as gastroparesis or following recurrent hypoglycemia. Therefore, it could represent an "ancestral" mechanism, highly conservative and effective in all individuals, conditions and clinical contexts. Recent guidelines recommend GLP-1 receptor agonists (GLP-1RAs) either as the first injectable therapy for type 2 diabetes mellitus or in combination with insulin. Considering the potential impact on GE, it would be important to study subjects on GLP-1 RAs during hypoglycemia, to establish whether a possible deceleration of GE impairs glucose counterregulation.

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.

Normal and disordered gastric emptying in diabetes: recent insights into (patho)physiology, management and impact on glycaemic control

Gastric emptying is a major determinant of postprandial blood glucose, accounting for ~35% of variance in peak glucose in both healthy individuals and those with type 2 diabetes. Gastric emptying is frequently disordered in individuals with diabetes (both abnormally delayed and accelerated). Delayed gastric emptying, i.e. diabetic gastroparesis, may be linked to upper gastrointestinal symptoms for which current treatment remains suboptimal; pharmacological acceleration of delayed emptying is only weakly associated with symptom improvement. Accordingly, the relationship between symptoms and delayed gastric emptying is not simply 'cause and effect'. In insulin-treated patients, disordered gastric emptying, even when not associated with gastrointestinal symptoms, can cause a mismatch between the onset of insulin action and the availability of absorbed carbohydrate, leading to suboptimal glycaemic control. In patients with type 2 diabetes, interventions that slow gastric emptying, e.g. glucagon-like peptide-1 receptor agonists, reduce postprandial blood glucose. This review focuses on recent insights into the impact of gastric emptying on postprandial blood glucose, effects of diabetes therapy on gastric emptying and the management of disordered gastric emptying in diabetes. In view of the broad relevance of gastric emptying to diabetes management, it is important that future clinical trials evaluating novel therapies that may affect gastric emptying should quantify the latter with an appropriate technique, such as scintigraphy or a stable isotope breath test.

Leite AZ, Correa-Giannella ML, Nery M, Queiroz MS. Diet consistency modification improves postprandial glycemic and gastroparesis symptoms

Abstract

Diabetic gastroparesis (DGP) is an autonomic neuropathy resulting from long-standing poorly controlled diabetes, and it is also linked to fluctuations in glycemic control due to variability on nutrient absorption.

Objectives

Considering the scarcity of information, the aim of this study was to identify the impact of modifications on diet consistency on post-prandial glucose variability using a continuous glucose monitoring (CGM) and its effect on the perception and severity of gastrointestinal symptoms.

Methods

This proof-of-concept study was carried out in a cross-sectional cohort of six individuals with type 1 diabetes mellitus with confirmed diagnosis of DGP. Two types of diet were used to evaluate glycemic control and DGP symptoms, general consistency standard meal (SD) and modified consistency test diet (MD), associated with an application of rapid acting insulin at the time of food intake. Glycemic control was evaluated by CGM, and the Gastroparesis Cardinal Symptom Index (GCSI) was applied after meals.

Results

The CGM curve was different for MD + insulin and SD + insulin. There was a smaller increment of interstitial glucose with 2 h after MD + insulin, returning almost to the basal level 4 h later. Patients scored significantly lower GCSI after MD + insulin compared to the same index after they received SD + insulin. Moreover, there was a decrease in important clinical scores present in the index, like: "Not able to finish meal", "Loss of appetite" and "Stomach or belly feels larger".

Conclusion

This study showed that a modified diet can improve postprandial glycemic excursion and the perception and severity of gastroparesis symptoms.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-022-01117-w.

A Food First Approach to Carbohydrate Supplementation in Endurance Exercise: A Systematic Review

This systematic review analyzed whether carbohydrate source (food vs. supplement) influenced performance and gastrointestinal (GI) symptoms during endurance exercise. Medline, SPORTDiscus, and citations were searched from inception to July 2021. Inclusion criteria were healthy, active males and females aged >18 years, investigating endurance performance, and GI symptoms after ingestion of carbohydrate from a food or supplement, <60 min before or during endurance exercise. The van Rosendale scale was used to determine risk of bias, with seven studies having low risk of bias. A total of 151 participants from 15 studies were included in the review. Three studies provided 0.6-1 g carbohydrate/kg body mass during 5-45 min precycling exercise (duration 60-70 min) while 12 studies provided 24-80 g/hr carbohydrate during exercise (60-330 min). Except one study that suggested a likely harmful effect (magnitude-based inferences) of a bar compared to a gel consumed during exercise on cycling performance, there were no differences in running (n = 1) or cycling (n = 13) performance/capacity between food and supplemental sources. Greater GI symptoms were reported with food compared with supplemental sources. Highly heterogenous study designs for carbohydrate dose and timing, as well as exercise protocol and duration, make it difficult to compare findings between studies. A further limitation results from only one study assessing running performance. Food choices of carbohydrate consumed immediately before and during endurance exercise result in similar exercise performance/capacity responses to supplemental carbohydrate sources, but may slightly increase GI symptoms in some athletes, particularly with exercise >2 hr.

Diabetic Gastroenteropathy: Soothe the Symptoms or Unravel a Cure?

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

Hybrid Closed-loop to Manage Gastroparesis in People With Type 1 Diabetes: a Case Series

BACKGROUND

Gastroparesis is associated with unpredictable gastric emptying and can lead to erratic glucose profiles and negative impacts on quality-of-life. Many people with gastroparesis are unable to meet glycemic targets and there is a need for new approaches for this population. Hybrid closed-loop systems improve glucose control and quality-of-life but evidence for their use in people with diabetic gastroparesis is limited.

METHODS

We present a narrative review of the challenges associated with type 1 diabetes management for people with gastroparesis and present a case series of 7 people with type 1 diabetes and gastroparesis. We compare glycemic control before and during the first 12 months of hybrid closed-loop therapy. Data were analyzed using electronic patient records and glucose management platforms. We also discuss future advancements for closed-loop systems that may benefit this population.

RESULTS

Five of 7 patients had data available for time in range before and during hybrid closed-loop therapy, and all had an improvement in percentage time in target glucose range, with the overall mean time in range increasing from 26.0% ± 15.7% to 58.4% ± 8.6% during HCL use, (P = .004). There were significant reductions in HbA1c (83 ± 9 mmol/mol to 71 ± 14 mmol/mol) and mean glucose from 13.0 ± 1.7 mmol/L (234 ± 31 mg/dL) to 10.0 ± 0.7 mmol/L (180 ± 13 mg/dL) with use of a hybrid closed-loop system. Importantly, this was achieved without an increase in time in hypoglycemia (P = .50).

CONCLUSION

Hybrid closed-loop systems may represent a valuable approach to improve glycemic control for people with type 1 diabetes and gastroparesis. Prospective studies are required to confirm these findings.

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.

Day-to-Day Variations in Fasting Plasma Glucose Do Not Influence Gastric Emptying in Subjects With Type 1 Diabetes

OBJECTIVE

Acute experimental variations in glycemia decelerate (hyperglycemia) or accelerate (hypoglycemia) gastric emptying. Whether spontaneous variations in fasting plasma glucose (FPG) have a similar influence on gastric emptying is yet unclear.

RESEARCH DESIGN AND METHODS

Gastric emptying of a mixed meal was prospectively studied three times in 20 patients with type 1 diabetes and 10 healthy subjects with normal glucose tolerance using a ¹³C-CO₂ octanoate breath test with Wagner-Nelson analysis. The velocity of gastric emptying was related to FPG measured before the test (grouped as low, intermediate, or high). In addition, gastric emptying data from 255 patients with type 1 diabetes studied for clinical indications were compared by tertiles of baseline FPG.

RESULTS

Despite marked variations in FPG (by 4.8 [95% CI 3.4; 6.2] mmol/L), gastric emptying did not differ among the three prospective examinations in patients with type 1 diabetes (Δ T_1/2 between highest and lowest FPG: 1 [95% CI -35; 37] min; P = 0.90). The coefficient of variation for T_1/2 determined three times was 21.0%. Similar results at much lower variations in FPG were found in healthy subjects. In the cross-sectional analysis, gastric emptying did not differ between the tertiles of FPG (Δ T_1/2 between highest and lowest FPG: 7 [95% CI -10; 23] min; P = 0.66), when FPG varied by 7.2 (6.7; 7.8) mmol/L. However, higher HbA_1c was significantly related to slower gastric emptying.

CONCLUSIONS

Day-to-day variations in FPG not induced by therapeutic measures do not influence gastric emptying significantly. These findings are in contrast with those obtained after rapidly clamping plasma glucose in the hyper- or hypoglycemic concentrations range and challenge the clinical importance of short-term glucose fluctuations for gastric emptying in patients with type 1 diabetes. Rather, chronic hyperglycemia is associated with slowed gastric emptying.

Acceleration of Gastric Emptying by Insulin-Induced Hypoglycemia is Dependent on the Degree of Hypoglycemia

CONTEXT

Hypoglycemia is a major barrier to optimal glycemic control in insulin-treated diabetes. Recent guidelines from the American Diabetes Association have subcategorized "non-severe" hypoglycemia into level 1 (<3.9 mmol/L) and 2 (<3 mmol/L) hypoglycemia. Gastric emptying of carbohydrate is a major determinant of postprandial glycemia but its role in hypoglycemia counter-regulation remains underappreciated. "Marked" hypoglycemia (~2.6 mmol/L) accelerates gastric emptying and increases carbohydrate absorption in health and type 1 diabetes, but the impact of "mild" hypoglycemia (3.0-3.9 mmol/L) is unknown.

OBJECTIVE

To determine the effects of 2 levels of hypoglycemia, 2.6 mmol/L ("marked") and 3.6 mmol/L ("mild"), on gastric emptying in health.

DESIGN, SETTING, AND SUBJECTS

Fourteen healthy male participants (mean age: 32.9 ± 8.3 years; body mass index: 24.5 ± 3.4 kg/m2) from the general community underwent measurement of gastric emptying of a radiolabeled solid meal (100 g beef) by scintigraphy over 120 minutes on 3 separate occasions, while blood glucose was maintained at either ~2.6 mmol/L, ~3.6 mmol/L, or ~6 mmol/L in random order from 15 minutes before until 60 minutes after meal ingestion using glucose-insulin clamp. Blood glucose was then maintained at 6 mmol/L from 60 to 120 minutes on all days.

RESULTS

Gastric emptying was accelerated during both mild (P = 0.011) and marked (P = 0.001) hypoglycemia when compared to euglycemia, and was more rapid during marked compared with mild hypoglycemia (P = 0.008). Hypoglycemia-induced gastric emptying acceleration during mild (r = 0.57, P = 0.030) and marked (r = 0.76, P = 0.0014) hypoglycemia was related to gastric emptying during euglycemia.

CONCLUSION

In health, acceleration of gastric emptying by insulin-induced hypoglycemia is dependent on the degree of hypoglycemia and baseline rate of emptying.

Gastrointestinal autonomic neuropathy in diabetes

Gastrointestinal autonomic neuropathy represents an important and diverse, but poorly appreciated, manifestation of diabetic autonomic neuropathy that impacts negatively on quality of life. There is no test to assess gastrointestinal autonomic nerve damage directly in humans; cardiovascular autonomic reflex tests are often used as a surrogate, but are suboptimal. Gastrointestinal symptoms are common in diabetes, but usually correlate only weakly with disordered motility. Diabetic gastroparesis, or abnormally delayed gastric emptying, occurs frequently and is the best characterized manifestation of gastrointestinal autonomic neuropathy. There is a bi-directional relationship between postprandial glycaemia and the rate of gastric emptying. However, autonomic neuropathy can affect the function of any gut segment from the esophagus to the anus. Current management options for gastrointestinal autonomic neuropathy are, for the main part, empirical and sub-optimal.

Study on the Mechanisms of Banxia Xiexin Decoction in Treating Diabetic Gastroparesis Based on Network Pharmacology

In China, Banxia Xiexin decoction (BXD) is applied to treat diabetic gastroparesis (DGP), but its key active ingredients and mechanisms against DGP are unclear. This study is designated to reveal the molecular mechanisms of BXD in treating DGP by adopting a creative approach known as network pharmacology to explore the active ingredients and therapeutic targets of BXD. In our study, 730 differentially expressed genes of DGP were obtained, and 30 potential targets of BXD against DGP were screened out (including ADRB2, DRD1, FOS, MMP9, FOSL1, FOSL2, JUN, MAP2, DRD2, MYC, F3, CDKN1A, IL6, NFKBIA, ICAM1, CCL2, SELE, DUOX2, MGAM, THBD, SERPINE1, ALOX5, CXCL11, CXCL2, CXCL10, RUNX2, CD40LG, C1QB, MCL1, and ADCYAP1). Based on the findings, BXD contains 60 compounds with therapeutic effect on DGP, including the key active ingredients such as quercetin, wogonin, baicalein, beta-sitosterol, and kaempferol. Sixty-eight pathways including TNF signaling pathway, IL-17 signaling pathway, and AGE-RAGE signaling pathway were significantly enriched. In this study, the mechanisms of BXD in treating DGP are affirmed to be a complex network with multi-target and multi-pathway, which provides a reference for future experimental studies.

Preoperative Blood Glucose Level Predicts Postsurgical Gastroparesis Syndrome after Subtotal Gastrectomy: Development of an Individualized Usable Nomogram

BACKGROUND

Postsurgical gastroparesis syndrome (PGS) after subtotal gastrectomy imposes significant social and economic burdens. We aimed to investigate the relationship between preoperative blood glucose level and PGS and develop a nomogram for individualized prediction. Patients and Methods. We retrospectively analyzed 633 patients with gastric cancer who underwent subtotal gastrectomy. Preoperative blood glucose levels were evaluated via receiver operating characteristic (ROC) curve analysis. Chi-squared tests and multivariable logistic regression analyses were used to develop a predictive model for PGS, presented as a nomogram, which was assessed for its clinical usefulness.

RESULTS

Thirty-eight of 633 patients were diagnosed with PGS. Based on the ROC curve analysis, the preoperative blood glucose cutoff value for PGS was 6.25 mmol/L. The predictors of PGS included preoperative hyperglycemia (odds ratio (OR) 2.3, P = 0.03), body mass index (BMI; OR 0.21, P = 0.14 for BMI < 18.5 and OR 3.0, P = 0.004 for BMI > 24), and the anastomotic method (OR 7.3, P = 0.001 for Billroth II and OR 5.9, P = 0.15 for Roux-en-Y). The predictive model showed good discrimination ability, with a C-index of 0.710, and was clinically useful.

CONCLUSIONS

Preoperative hyperglycemia effectively predicts PGS. We present a nomogram incorporating the preoperative blood glucose level, BMI, anastomotic method, and tumor size, for individualized prediction of PGS.

Rapid gastric emptying in diabetes mellitus: Pathophysiology and clinical importance

Although slow gastric emptying (gastroparesis) is a well-known complication of chronic hyperglycemia in diabetes mellitus (DM), it recently has become clear that rapid gastric emptying also is a frequent and important diabetic complication. In contrast, acute hyperglycemia causes slow gastric emptying, and acute hypoglycemia causes rapid gastric emptying. Rapid gastric emptying is frequent in T2DM; however, it may also occur in T1DM, particularly in the early stages of the disease, but may persist even into late stages. Recent studies suggest that usually, the stomach restricts the emptying of nutrients to 1-4 kcals/min. This restriction is due to the action of the gastric 'braking' hormones such as GLP-1, leptin, and amylin acting via the gastric inhibitory vagal motor circuit (GIVMC). Disruption of this braking system leads to rapid gastric emptying. Acute hyperglycemia also slows gastric emptying by stimulating the GIVMC, while acute hypoglycemia causes rapid gastric emptying by stimulating the gastric excitatory vagal motor circuit (GEVMC). In contrast, chronic hyperglycemia causes rapid gastric emptying by inducing oxidative stress in the stomach wall that disrupts inhibitory neuromuscular transmission and increases the contractility of the smooth muscle, while chronic hyperglycemia may also cause slow gastric emptying via severe inflammatory stress caused by proinflammatory macrophages and reduce contractility of the smooth muscle. There is a bidirectional relationship between blood glucose and gastric emptying. Thus, rapid gastric emptying may lead to a sizeable postprandial spike, and slow gastric emptying may blunt it. Postprandial hyperglycemia is involved in the development, progression, and complications of DM. Correction of fast gastric emptying involves agents that activate GIVMC and the use of gastric 'braking' hormones or their analogs. Recognition and treatment of rapid gastric emptying may contribute to better management of postprandial hyperglycemia and prevention of some diabetic complications.