Relationships of upper gastrointestinal motor and sensory function with glycemic control

Glucose increases synaptic transmission from vagal afferent central nerve terminals via modulation of 5-HT3 receptors

Acute hyperglycemia has profound effects on vagally mediated gastrointestinal functions. We have reported recently that the release of glutamate from the central terminals of vagal afferent neurons is correlated directly with the extracellular glucose concentration. The present study was designed to test the hypothesis that 5-HT(3) receptors present on vagal afferent nerve terminals are involved in this glucose-dependent modulation of glutamatergic synaptic transmission. Whole-cell patch-clamp recordings were made from neurons of the nucleus tractus solitarius (NTS) in thin rat brainstem slices. Spontaneous and evoked glutamate release was decreased in a concentration-dependent manner by the 5-HT(3) receptor selective antagonist, ondansetron. Alterations in the extracellular glucose concentration induced parallel shifts in the ondansetron-mediated inhibition of glutamate release. The changes in excitatory synaptic transmission induced by extracellular glucose concentration were mimicked by the serotonin uptake inhibitor, fenfluramine. These data suggest that glucose alters excitatory synaptic transmission within the rat brainstem via actions on tonically active 5-HT(3) receptors, and the number of 5-HT(3) receptors on vagal afferent nerve terminals is positively correlated with the extracellular glucose concentration. These data indicate that the 5-HT(3) receptors present on synaptic connections between vagal afferent nerve terminals and NTS neurons are a strong candidate for consideration as one of the sites where glucose acts to modulate vagovagal reflexes.

Modulation of intestinal cholesterol absorption by high glucose levels: impact on cholesterol transporters, regulatory enzymes, and transcription factors

Growing evidence suggests that the small intestine may contribute to excessive postprandial lipemia, which is highly prevalent in insulin-resistant/Type 2 diabetic individuals and substantially increases the risk of cardiovascular disease. The aim of the present study was to determine the role of high glucose levels on intestinal cholesterol absorption, cholesterol transporter expression, enzymes controlling cholesterol homeostasis, and the status of transcription factors. To this end, we employed highly differentiated and polarized cells (20 days of culture), plated on permeable polycarbonate filters. In the presence of [(14)C]cholesterol, glucose at 25 mM stimulated cholesterol uptake compared with Caco-2/15 cells supplemented with 5 mM glucose (P < 0.04). Because combination of 5 mM glucose with 20 mM of the structurally related mannitol or sorbitol did not change cholesterol uptake, we conclude that extracellular glucose concentration is uniquely involved in the regulation of intestinal cholesterol transport. The high concentration of glucose enhanced the protein expression of the critical cholesterol transporter NPC1L1 and that of CD36 (P < 0.02) and concomitantly decreased SR-BI protein mass (P < 0.02). No significant changes were observed in the protein expression of ABCA1 and ABCG8, which act as efflux pumps favoring cholesterol export out of absorptive cells. At the same time, 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity was decreased (P < 0.007), whereas ACAT activity remained unchanged. Finally, increases were noted in the transcription factors LXR-alpha, LXR-beta, PPAR-beta, and PPAR-gamma along with a drop in the protein expression of SREBP-2. Collectively, our data indicate that glucose at high concentrations may regulate intestinal cholesterol transport and metabolism in Caco-2/15 cells, thus suggesting a potential influence on the cholesterol absorption process in Type 2 diabetes.

Central neuronal mechanisms of gastric electrical stimulation in diabetic gastroparesis

OBJECTIVE

The mechanisms underlying symptom improvement in gastric electrical stimulation (GES) are not fully understood. Modulation of the central nervous system excitability may be involved. The objective of the study was to investigate the central effects of GES, including the possible modulation of the visceral sensory nervous system.

MATERIAL AND METHODS

A gastric electrical stimulator was implanted in seven diabetic patients with medically refractory gastroparesis. A double-blinded protocol was used to investigate the patients at baseline and one month after recovery with the stimulator turned on and off (1-month periods). The following assessments were carried out: mechanical, thermal and electrical stimulations with sensory recordings in the esophagus and duodenum, and standardized, self-administered, daily symptom questionnaires.

RESULTS

No difference was found between baseline and the on- and off periods in overall gut pain thresholds across all stimulus modalities in the esophagus (p=0.63), duodenum (p=0.19) or esophagus and duodenum combined (p=0.76). No difference in the sensory response to mechanical stimulation was found in the esophagus before (all p>0.31) and after (all p>0.43) smooth muscle relaxation with butylscopolamine. Similar findings were observed in the duodenum. No differences were found in thermal sensitivity (esophagus (p=0.67) and duodenum (p=0.17)), sensory response to electrical stimulation (esophagus (p=0.57) and duodenum (p=0.52)) or induced somatic referred pain areas (esophagus (p=0.75) and duodenum (p=0.51)). No difference was seen in the induced somatic referred pain areas or self-reported symptoms.

CONCLUSIONS

No evidence was found for GES-induced modulation of the visceral sensory system and central excitability. However, GES has been proven to modulate the central nervous system in animal studies, necessitating further human experiments in order unambiguously to establish the possible central effects of GES.

Disintegration of solid foods in human stomach

Knowledge of the disintegration of solid foods in human stomach is essential to assess the bioavailability of nutrients in the gastrointestinal (GI) tract. A comprehensive review of food gastric digestion, focusing on disintegration of solid foods, is presented. Most of the research reviewed in this paper is contained in the medical, pharmaceutical, food, and nutritional literature. Stomach physiology is briefly introduced, including composition and rheological properties of gastric contents, stomach wall motility in fed/fasted states, and hydrodynamic and mechanical forces that act on the ingested food. In vivo and in vitro methods used for studying food and drug digestion in GI are summarized. Stomach emptying rate, which controls the rate of absorption of nutrients, is highly related to the disintegration of foods. This topic is highlighted with focus on the important mechanisms and the influence of chemical and physical properties of foods. Future research in this area is identified to increase our fundamental understanding of the food digestion process in the stomach as related to the food composition, material properties such as texture and microstructure, and chemical characteristics. This information is necessary to develop new guidelines for seeking innovative processing methods to manufacture foods specifically targeted for health.

Gastrointestinal symptoms and glycemic control in diabetes mellitus: a longitudinal population study

BACKGROUND

The prevalence of gastrointestinal (GI) symptoms is increased in diabetes, but their natural history is understood poorly and any impact of glycemic control is controversial. We aimed to quantify changes in GI symptom status and glycemic control among a population sample of patients with diabetes.

METHODS

Data on 10 chronic GI symptom complexes were obtained from a validated questionnaire at baseline and after 12 months. Changes in acute and chronic glycemic control were classified as always adequate, variable (deteriorated or improved), or always inadequate; acute glycemic control was assessed by fasting plasma glucose and chronic glycemic control by a validated self-report 5-point graded scale.

RESULTS

Baseline and follow-up data were available in 136 individuals with diabetes (mean age 59 years; 66% males; 95% type 2). The most prevalent GI symptom complexes were abdominal bloating/distension (35%), ulcer-like dyspepsia (35%), and irritable bowel syndrome (27%). Overall, between 7 and 24% reported a change in GI symptoms with the largest change in irritable bowel syndrome (24%), bloating/distension (22%), and ulcer-like dyspepsia (21%). Those who had a change in abdominal bloating (either loss or gain) over 12 months were more likely to have increased their mean fasting plasma glucose (P<0.05). Contrary to expectations, consistently poor self-reported glycemic control was only weakly associated with less persistent abdominal pain (r=-0.2, P=0.03), diarrhea (r=-0.22, P=0.01), and abdominal bloating (r=-0.2, P=0.03). Acute glycemic control was not significantly related to any GI symptoms.

CONCLUSION

We were unable to demonstrate any association between worsening GI symptoms and glycemic control.

Incretin mimetics and dipeptidyl peptidase-4 inhibitors: innovative treatment therapies for type 2 diabetes

The prevalence of diabetes and impaired glucose tolerance is predicted to dramatically increase over the next two decades. Clinical therapies for type 2 diabetes mellitus (T2DM) have traditionally included lifestyle modification, oral anti-diabetic agents, and ultimately insulin initiation. In this report, we review the clinical trial results of two innovative T2DM treatment therapies that are based on the glucoregulatory effects of incretin hormones. Incretin mimetics are peptide drugs that mimic several of the actions of glucagon-like peptide-1 (GLP-1) and have been shown to lower glycated hemoglobin (A1C) levels in patients with T2DM. Additionally, incretin mimetics lower postprandial and fasting glucose, suppress elevated glucagon release, and are associated with progressive weight reduction. Dipeptidyl peptidase-4 (DPP-4) inhibitors increase endogenous GLP-1 levels by inhibiting the enzymatic degradation of GLP-1. Clinical studies in patients with T2DM have shown that DPP-4 inhibitors reduce elevated A1C, lower postprandial and fasting glucose, suppress glucagon release, and are weight neutral. Collectively, these new drugs, given in combination with other antidiabetic agents, such as metformin, sulfonylureas, and/or thiazolidinediones, can help restore glucose homeostasis in poorly controlled patients with T2DM.

A stable isotope breath test with a standard meal for abnormal gastric emptying of solids in the clinic and in research

BACKGROUND & AIMS

The aim of this study was to validate a [13C]-Spirulina platensis gastric emptying (GE) breath test (GEBT) with a standardized meal.

METHODS

Thirty-eight healthy volunteers and 129 patients with clinically suspected delayed GE underwent measurements at 45, 90, 120, 150, 180, and 240 minutes after a 238 kcal meal labeled test with 100 mg [13C]-S platensis and 0.5 mCi 99mTc. We established normal ranges for scintigraphy with this test meal, intraindividual and interindividual coefficients of variation (COVs), and the ability of the [13C] GEBT breath percent dose excreted *1000 values to predict scintigraphic half-life and to categorize GE as delayed, normal, or accelerated.

RESULTS

In health, the 10th and 90th percentiles of half-life for scintigraphic GE with this meal were 52 and 86 minutes; intraindividual COVs for scintigraphy and the GEBT were, respectively, 31% and 27% at 45 minutes, 17% and 21% at 90 minutes, 13% and 16% at 120 minutes, 10% and 13% at 150 minutes, and 8% and 12% at 180 minutes. Interindividual COVs at each time for the [13C] GEBT and scintigraphy were typically approximately 1%-4% lower than intraindividual COVs. Individual breath samples at 45, 150, and 180 minutes predicted GE category; at 80% specificity, 45- and 180-minute samples combined were 93% sensitive to identify accelerated GE, and 150- and 180-minute combined were 89% sensitive for delayed GE.

CONCLUSIONS

[13C]-S platensis GEBT is as reproducible as scintigraphy; imprecision with both tests reflects physiologic variation. With 4 breath samples, this method with an off-the-shelf meal is valid to assess GE in clinic and in research.

Effect of duodenal glucose and acute hyperglycemia on rectal perception and compliance in response to tension-controlled rectal distension in healthy humans

BACKGROUND

Acute changes in blood glucose concentration affect gastrointestinal motor and sensory function. Tone and distensibility contribute to intact rectal function.

AIMS

To test the effects of duodenal glucose (euglycemic hyperinsulinemia), intravenous glucose (hyperglycemic hyperinsulinemia), and saline (euglycemic normoinsulinemia as control) on rectal perception and compliance in response to tension-controlled rectal distension.

METHODS

During duodenal glucose at 2 kcal min(-1), marked hyperglycemic clamp (approximately 13 mmol L(-1)), or saline as control, responses to fixed-tension rectal distension, applied by means of a computerized tensostat, were compared randomized on three separate days in eight healthy subjects.

RESULTS

At discomfort level (score 3 on the 0-4 rectal score scale), perception of rectal distension was significantly higher during euglycemic hyperinsulinemia (45 +/- 3 g cm(-2) tolerance) and significantly lower during hyperglycemia (83 +/- 4 g cm(-2) tolerance), both reaching significance versus control (64 +/- 6 g cm(-2) tolerance; P < 0.05). At this level, no relevant variations of rectal compliance were seen, which were 10.3 +/- 1 mL mmHg(-1) during duodenal glucose, 9.5 +/- 1 mL mmHg(-1) for the group with hyperglycemia, and 9.7 +/- 2 mL mmHg(-1) for the control.

CONCLUSION

Duodenal glucose provokes rectal hypersensitivity whereas acute hyperglycemia contributes to rectal hyposensitivity. Despite different rectal tenso-sensitivity, rectal compliance remains virtually unchanged. Any dysfunction may cause rectal complaints.

Upper abdominal symptoms in patients with Type 1 diabetes: unrelated to impairment in gastric emptying caused by autonomic neuropathy

AIMS

Diabetic gastroparesis is a common condition occurring in some 30-50% of patients with long-term diabetes. Some studies have found a relationship between autonomic neuropathy and diabetic gastroparesis. In addition to autonomic neuropathy, acute changes in plasma glucose concentration can also affect gastric emptying. The objective was to examine the relationship between autonomic nerve function, glucose concentration, gastric emptying, and upper abdominal symptoms in Type 1 diabetic patients.

METHODS

Gastric emptying of solids and liquids was measured with scintigraphy in 27 patients with longstanding Type 1 diabetes with upper abdominal symptoms. Autonomic nerve function was examined by standardized cardiovascular tests, and plasma glucose concentrations were measured during scintigraphy. Severity of abdominal symptoms and quality of life were explored by validated questionnaires.

RESULTS

Seven patients (26%) had delayed gastric emptying of solids and three (11%) of liquids. Mean gastric half-emptying time of solids was 128 +/- 116 min and of liquids 42 +/- 30 min. Of the 26 patients undergoing tests, 16 (62%) had autonomic nerve dysfunction. Autonomic neuropathy score (1.6 +/- 1.7) correlated positively with the gastric emptying rate of solids (P = 0.006), a rate unrelated to symptom scores or plasma glucose concentrations during scintigraphy. Quality of life in patients with abdominal symptoms was lower than in the normal Finnish population.

CONCLUSIONS

Impaired gastric emptying of solids in patients with Type 1 diabetes is related to autonomic neuropathy, but not to actual glycaemic control. The upper abdominal symptoms observed in these patients cannot be explained, however, by impaired gastric emptying.

Effect of itopride on gastric emptying in longstanding diabetes mellitus

Delayed gastric emptying (GE) occurs in 30-50% of patients with longstanding type 1 or 2 diabetes, and represents a major cause of morbidity. Current therapeutic options are limited. We aimed at evaluating the effects of itopride on GE in patients with longstanding diabetes. Twenty-five patients (20 type 1, 5 type 2; 10 males, 15 females; mean age 45.2 +/- 2.7 years; body mass index 27.5 +/- 0.9 kg m(-2); duration of diabetes 20.2 +/- 2.4 years) were enrolled in a double-blind, placebo-controlled, randomized, crossover trial. Subjects received both itopride (200 mg) and placebo t.i.d. for 7 days, with a washout of 7-14 days. GE (scintigraphy), blood glucose (glucometer) and upper gastrointestinal (GI) symptoms (questionnaire) were measured following each treatment period. The test meal comprised 100 g ground beef (99mTc-sulphur colloid) and 150 mL of 10% dextrose [67Ga-ethylenediaminetetraacetic acid (EDTA)]. There was a slight trend for itopride to accelerate both solid (P = 0.09) and liquid (P = 0.09) GE. With itopride treatment, the emptying of both solids and liquids tended to be more accelerated, as the emptying with placebo was slower (solids: r = 0.39, P = 0.057; liquids: r = 0.44, P < 0.03). Twelve (48%) patients had delayed solid and/or liquid GE on placebo and in this group, itopride modestly accelerated liquid (P < 0.05), but not solid (P = 0.39), emptying. Itopride had no effect on mean blood glucose during the GE measurement (placebo: 9.8 +/- 0.6 mmol L(-1) vs itopride: 9.6 +/-0.6 mmol L(-1)), or GI symptoms (placebo: 1.4 +/- 0.4 vs itopride: 1.8 +/- 0.5). Itopride, in a dose of 200 mg t.i.d. for 7 days, tends to accelerate GE of liquids and solids in longstanding diabetes. The magnitude of this effect appears to be modest and possibly dependent on the rate of GE without itopride.

Review article: gastroparesis

BACKGROUND

Gastroparesis is a chronic disorder caused by stomach pump failure and characterized by profound nausea, vomiting and epigastric pain. Most often, the cause is unapparent and of the known associations, diabetes is the most common. Diagnosis is usually made using an isotope-labelled test meal. Treatment is incremental and includes education, dietary support, prokinetic and antiemetic agents. There are novel approaches including gastric neurostimulation.

AIM

To review current concepts of gastric motor function, aetiology, investigation and treatment of gastroparesis.

METHODS

A systematic web-based review of the literature was undertaken using a lexicon of terms associated with gastroparesis.

RESULTS

There are few controlled studies of this condition. Little is known about causation or underlying nerve, muscle or pacemaker pathology. Idiopathic gastroparesis occurs most commonly in women and gastric emptying is often abnormal in diabetes. Isotopic gastric scintigraphy remains the gold standard investigation, but alternative tests are being developed. Treatment is multimodal and includes education, and nutritional support. There are no adequately powered controlled trials to support a particular drug regimen. In intractable gastroparesis, gastric neurostimulation appears to offer benefit.

CONCLUSION

Despite a significant progress in the past decade, further controlled trials are required into the therapeutic options available for treating this intriguing condition.

Prevalence and determinants of delayed gastric emptying in hospitalised Type 2 diabetic patients

AIM: To determine the prevalence of delayed gastric emptying (GE) in older patients with Type 2 diabetes mellitus.

METHODS: One hundred and forty seven patients with Type 2 diabetes, of whom 140 had been hospitalised, mean age 62.3 ± 8.0 years, HbA1c 9.1% ± 1.9%, treated with either oral hypoglycemic drugs or insulin were studied. GE of a solid meal (scintigraphy), autonomic nerve function, upper gastrointestinal symptoms, acute and chronic glycemic control were evaluated. Gastric emptying results were compared to a control range of hospitalised patients who did not have diabetes.

RESULTS: Gastric emptying was delayed (T50 > 85 min) in 17.7% patients. Mean gastric emptying was slower in females (T50 72.1 ± 72.1 min vs 56.9 ± 68.1 min, P = 0.02) and in those reporting nausea (112.3 ± 67.3 vs 62.7 ± 70.0 min, P < 0.01) and early satiety (114.0 ± 135.2 vs 61.1 ± 62.6 min, P = 0.02). There was no correlation between GE with age, body weight, duration of diabetes, neuropathy, current glycemia or the total score for upper gastrointestinal symptoms.

CONCLUSION: Prolonged GE occurs in about 20% of hospitalised elderly patients with Type 2 diabetes when compared to hospitalised patients who do not have diabetes. Female gender, nausea and early satiety are associated with higher probability of delayed GE.

D-glucose modulates synaptic transmission from the central terminals of vagal afferent fibers

Experimental evidence suggests that glucose modulates gastric functions via vagally mediated effects. It is unclear whether glucose affects only peripheral vagal nerve activity or whether glucose also modulates vagal circuitry at the level of the brain stem. This study used whole cell patch-clamp recordings from neurons of the nucleus of the tractus solitarius (NTS) to assess whether acute variations in glucose modulates vagal brain stem neurocircuitry. Increasing D-glucose concentration induced a postsynaptic response in 40% of neurons; neither the response type (inward vs. outward current) nor response magnitude was altered in the presence of tetrodotoxin suggesting direct effects on the NTS neuronal membrane. In contrast, reducing d-glucose concentration induced a postsynaptic response (inward or outward current) in 54% of NTS neurons; tetrodotoxin abolished these responses, suggesting indirect sites of action. The frequency, but not amplitude, of spontaneous and miniature excitatory postsynaptic currents (EPSCs) was correlated with d-glucose concentration in 79% of neurons tested (n = 48). Prior surgical afferent rhizotomy abolished the ability of D-glucose to modulate spontaneous EPSC frequency, suggesting presynaptic actions at vagal afferent nerve terminals to modulate glutamatergic synaptic transmission. In experiments in which EPSCs were evoked via electrical stimulation of the tractus solitarius, EPSC amplitude correlated with D-glucose concentration. These effects were not mimicked by L-glucose, suggesting the involvement of glucose metabolism, not uptake, in the nerve terminal. These data suggest that the synaptic connections between vagal afferent nerve terminals and NTS neurons are a strong candidate for consideration as one of the sites where glucose-evoked changes in vagovagal reflexes occurs.

Two-channel gastric pacing with a novel implantable gastric pacemaker accelerates glucagon-induced delayed gastric emptying in dogs

BACKGROUND

The aim of the current study was to investigate the efficacy of 2-channel gastric electrical stimulation (GES) with a custom-made implantable pacemaker on delayed gastric emptying and gastric dysrhythmia induced by glucagon in dogs.

METHODS

Six dogs were studied in 4 randomized session (saline, glucagon, glucagon with single-channel or 2-channel GES). GES was applied via the first pair of electrodes for single-channel GES or the first and third pairs of electrodes for 2-channel GES. Gastric emptying was assessed for 90 minutes and gastric slow waves were recorded at the same time.

RESULTS

Both single-channel and 2-channel GES improved gastric dysrhythmia (P < .05 vs glucagon session). Two-channel GES but not single-channel GES improved glucagon-induced delayed gastric emptying at 30 minutes, 45 minutes, 60 minutes, 75 minutes, and 90 minutes.

CONCLUSION

Two-channel GES with a novel implantable pacemaker is more efficient and effective than single-channel GES in improving delayed gastric emptying induced by glucagon. This implantable multipoint pacemaker may provide a new option for treatment of gastric motility disorders.

Glucose homeostasis and the gastrointestinal tract: insights into the treatment of diabetes

The gastrointestinal tract is increasingly viewed as a critical organ in glucose metabolism because of its role in delivering glucose to the circulation and in secreting multiple glucoregulatory hormones that, in concert with insulin and glucagon, regulate glucose homeostasis. Under normal conditions, a complex interplay of these hormones acts to maintain plasma glucose within a narrow range despite large variations in the availability of glucose, particularly during transition from the fasting to fed state. In the fed state, the rate at which nutrients are passed from the stomach to the duodenum, termed gastric emptying rate, is a key determinant of postprandial glucose flux. In patients with diabetes, the regulation of glucose metabolism is disrupted resulting in fasting and postprandial hyperglycaemia. Elucidation of the role of the gastrointestinal tract, gut-derived glucoregulatory peptides and gastric emptying rate offers a new perspective on glucose homeostasis and the respective importance of these factors in the diabetes state. This review will highlight the importance of the gastrointestinal tract in playing a key role in glucose homeostasis, particularly in the postprandial period, and the role of established or new therapies that either leverage or modify gastrointestinal function to improve glycaemic state.

Exenatide

Exenatide is the first in a new class of compounds, which possess similar activity to the naturally-occurring hormone glucagon-like peptide-1 (GLP-1). It mirrors many of the effects of GLP-1, improving glycaemic control through a combination of mechanisms, which include glucose-dependent stimulation of insulin secretion, suppression of glucagon secretion, slowing of gastric emptying and reduced appetite. Phase III clinical trials showed exenatide therapy for 30 weeks significantly reduced glycated haemoglobin, and fasting and postprandial plasma glucose compared with baseline when added to metformin and sulfonylureas or a combination of the two, with an average weight loss of approximately 2 kg. Exenatide can also be used in combination with thiazolidinediones and may be an alternative to insulin in patients requiring additional therapy. In patients with established Type 2 diabetes, control of both glycaemia and body weight are important to minimise the risk of future diabetes complications. Open-label extensions from these pivotal trials demonstrate that patients treated with exenatide for < or = 3 years sustained the reductions in glycaemic control achieved at 30 weeks and had a progressive reduction in body weight. Exenatide is generally well tolerated; nausea is the most commonly reported side effect, but can be significantly reduced when a target dose of exenatide is achieved in patients with gradual dose titration. Hypoglycaemia has been encountered in clinical trials of exenatide, especially on initiation of therapy with sulfonylureas (not with metformin). Exenatide may enable patients with Type 2 diabetes to improve glycaemic control and reduce or eliminate the risk of hypoglycaemia and weight gain.

Effects of agar and pectin on gastric emptying and post-prandial glycaemic profiles in healthy human volunteers

1. Dietary fibre, such as pectin, delays gastric emptying and may enhance post-prandial glucose tolerance. Agar, which is high in fibre content, is widely used in the traditional Japanese diet. Although long-term diet therapy with agar decreases fasting plasma glucose levels in diabetes, knowledge is lacking about the acute effects of agar on gastric emptying and the post-prandial glycaemic profiles. The present study was designed to investigate the acute effects of agar. 2. Ten healthy male volunteers were studied on three occasions with three different test meals (450 kcal/500 mL): (i) a fibre-free meal; (ii) a meal with 2.0 g agar; or (iii) a meal with 5.2 g pectin. On each occasion, participants underwent a [(13)C]-acetate breath test along with serial blood sampling. To quantify gastric emptying, the half [(13)CO(2)] excretion time (t((1/2)b)) and the time for maximal [(13)CO(2)] excretion rate (t(lag)) were determined. The post-prandial glycaemic response was expressed as an incremental change from the fasting value at each sampling time. Data were analysed using repeated-measures analysis of variance (anova), followed by a post hoc paired Student's t-test with Bonferroni adjustment. 3. The time-course for respiratory [(13)CO(2)] excretion differed significantly among the three test meals (P = 0.0004, anova). Compared with the control meal, [(13)CO(2)] excretion was significantly lower following consumption of the agar meal (between 40 and 105 min post-prandially; P < 0.025, Student's t-test) and the pectin meal (between 40 and 180 min post-prandially; P < 0.025, Student's t-test). Among the three meals, significant differences were found in t((1/2)b) (P = 0.002, anova) and t(lag) (P = 0.011, anova). Compared with the control meal, the agar and pectin meals exhibited a significantly prolonged t((1/2)b) (P = 0.007 and P < 0.0001, respectively, Student's t-test) and t(lag) (P = 0.006 and P = 0.002, respectively, Student's t-test). Neither the agar nor pectin meal affected the post-prandial glucose profile. 4. In healthy adults, agar and pectin delay gastric emptying but have no impact on the post-prandial glucose response.

Effects of protein on glycemic and incretin responses and gastric emptying after oral glucose in healthy subjects

BACKGROUND

Dietary interventions represent a promising therapeutic strategy to optimize postprandial glycemia. The addition of protein to oral glucose has been reported to improve the glycemic profile.

OBJECTIVE

The aim of the current study was to evaluate the mechanisms by which protein supplementation lowers the blood glucose response to oral glucose.

DESIGN

Nine healthy men were studied on 3 d each in a random order. Subjects consumed 300-mL drinks containing either 50 g glucose (Glucose), 30 g gelatin (Protein), or 50 g glucose with 30 g gelatin (Glucose + Protein) in water labeled with 150 mg [(13)C]acetate. Blood and breath samples were subsequently collected for 3 h to measure blood glucose and plasma insulin, glucagon-like peptide 1 (GLP-1), and glucose-dependent insulinotropic polypeptide (GIP) concentrations and gastric half-emptying time, which was calculated from (13)CO(2) excretion.

RESULTS

The blood glucose response was less after Glucose + Protein than after Glucose (P < 0.005); GIP was lower (P < 0.005), and there were no significant differences in plasma insulin or GLP-1. Protein alone stimulated insulin, GLP-1, and GIP (P < 0.05 for each) without elevating blood glucose. The gastric half-emptying time was greater after Glucose + Protein than after Glucose (P < 0.05) and tended to be greater for Glucose than for Protein (P = 0.06).

CONCLUSIONS

In healthy humans, the addition of protein to oral glucose lowers postprandial blood glucose concentrations acutely, predominantly by slowing gastric emptying, although protein also stimulates incretin hormones and non-glucose-dependent insulin release.

Determination of gastric emptying in nonobese diabetic mice

Animal studies on diabetic gastroparesis are limited by inability to follow gastric emptying changes in the same mouse. The study aim was to validate a nonlethal gastric emptying method in nonobese diabetic (NOD) LtJ mice, a model of type 1 diabetes, and study sequential changes with age and early diabetic status. The reliability and responsiveness of a [(13)C]octanoic acid breath test in NOD LtJ mice was tested, and the test was used to measure solid gastric emptying in NOD LtJ mice and nonobese diabetes resistant (NOR) LtJ mice. The (13)C breath test produced results similar to postmortem recovery of a meal. Bethanechol accelerated gastric emptying [control: 92 +/- 9 min; bethanechol: 53 +/- 3 min, mean half emptying time (T(1/2)) +/- SE], and atropine slowed gastric emptying (control: 92 +/- 9 min; atropine: 184 +/- 31 min, mean T(1/2) +/- SE). Normal gastric emptying (T(1/2)) in nondiabetic NOD LtJ mice (8-12 wk) was 91 +/- 2 min. Aging had differing effects on gastric emptying in NOD LtJ and NOR LtJ mice. Onset of diabetes was accompanied by accelerated gastric emptying during weeks 1-2 of diabetes. Gastric emptying returned to normal by weeks 3-5 with no delay. The [(13)C]octanoic acid breath test accurately measures gastric emptying in NOD LtJ mice, is useful to study the time course of changes in gastric emptying in diabetic NOD LtJ mice, and is able to detect acceleration in gastric emptying early in diabetes. Opposing changes in gastric emptying between NOD LtJ and NOR LtJ mice suggest that NOR LtJ mice are not good controls for the study of gastric emptying in NOD LtJ mice.

Gastric emptying, diabetes, and aging

Gastric emptying is mildly slowed in healthy aging, although generally remains within the normal range for young people. The significance of this is unclear, but may potentially influence the absorption of certain drugs, especially when a rapid effect is desired. Type 2 diabetes is common in the elderly, but there is little data regarding its natural history, prognosis, and management. This article focuses on the interactions between gastric emptying and diabetes, how each is influenced by the process of aging, and the implications for patient management.

The relationship between blood glucose control and intolerance to enteral feeding during critical illness

OBJECTIVE

To assess the relationship between blood glucose concentrations (BSL) and intolerance to gastric feeding in critically ill patients.

DESIGN

Prospective, case-controlled study.

PATIENTS AND PARTICIPANTS

Two-hourly BSL and insulin requirements over the first 10 days after admission were assessed in 95 consecutive feed-intolerant (NG aspirate > 250 ml during feed) critically ill patients and 50 age-matched, feed-tolerant patients who received feeds for at least 3 days. Patients with diabetes mellitus were excluded. A standard insulin protocol was used to maintain BSL at 5.0-7.9 mmol.

MEASUREMENTS AND RESULTS

The peak BSLs were significantly higher before and during enteral feeding in feed-intolerant patients. The mean and trough BSLs were, however, similar between the two groups on admission, 24 h prior to feeding and for the first 4 days of feeding. The variations in BSLs over 24 h before and during enteral feeding were significantly greater in feed-intolerant patients. A BSL greater than 10 mmol/l was more prevalent in patients with feed intolerance during enteral feeding. The time taken to develop feed intolerance was inversely related to the admission BSL (r= -0.40). The amount of insulin administered before and during enteral feeding was similar between the two groups.

CONCLUSIONS

Feed intolerance in critically ill patients is associated with a greater degree of glycaemic variation, with a greater number of patients with transient hyperglycaemia. These data suggest more intensive insulin therapy may be required to minimize feed intolerance, an issue that warrants further study.

Impaired contractility and remodeling of the upper gastrointestinal tract in diabetes mellitus type-1

AIM: To investigate that both the neuronal function of the contractile system and structural apparatus of the gastrointestinal tract are affected in patients with longstanding diabetes and auto mic neuropathy.

METHODS: The evoked esophageal and duodenal contractile activity to standardized bag distension was assessed using a specialized ultrasound-based probe. Twelve type-1 diabetic patients with autonomic neuropathy and severe gastrointestinal symptoms and 12 healthy controls were studied. The geometry and biomechanical parameters (strain, tension/stress, and stiffness) were assessed.

RESULTS: The diabetic patients had increased frequency of distension-induced contractions (6.0 ± 0.6 vs 3.3 ± 0.5, P < 0.001). This increased reactivity was correlated with the duration of the disease (P = 0.009). Impaired coordination of the contractile activity in diabetic patients was demonstrated as imbalance between the time required to evoke the first contraction at the distension site and proximal to it (1.5 ± 0.6 vs 0.5 ± 0.1, P = 0.03). The esophageal wall and especially the mucosa-submucosa layer had increased thickness in the patients (P < 0.001), and the longitudinal and radial compressive stretch was less in diabetics (P < 0.001). The esophageal and duodenal wall stiffness and circumferential deformation induced by the distensions were not affected in the patients (all P > 0.14).

CONCLUSION: The impaired contractile activity with an imbalance in the distension-induced contractions likely reflects neuronal abnormalities due to autonomic neuropathy. However, structural changes and remodeling of the gastrointestinal tract are also evident and may add to the neuronal changes. This may contribute to the pathophysiology of diabetic gut dysfunction and impact on future management of diabetic patients with gastrointestinal symptoms.

Effect of tegaserod on gastric emptying and the expression of ghrelin and substance P in diabetic rats

AIM: To investigate the effect of tegaserod on gastric emptying and the expression of ghrelin and substance P (SP) in diabetic rats, and to explore the therapeutic effect of tegaserod on diabetic gastroparesis and its possible mechanism.

METHODS: Fifty Wistar rats were randomly divided into five groups: a normal control group (NC group, n = 10), a diabetes mellitus group (DM group, n = 10), a low dose tegaserod-treated group (TEG-L group, n = 10), a moderate dose tegaserod-treated group (TEG-M group, n = 10) and a high dose tegaserod-treated group (TEG-H group, n = 10). Diabetes was induced by intraperitoneal injection of streptozotocin (STZ). After 8 weeks, tegaserod was administered by intraperitoneal injection at doses of 0.1 mg/kg, 0.5 mg/kg and 1 mg/kg in TEG-L, TEG-M and TEG-H groups, respectively, for 3 days. Gastric emptying was measured by intragastric administration of phenol red. The expression of ghrelin in the gastric mucosa and SP in the gastric antrum was detected by immunohistochemistry.

RESULTS: The staining intensities for ghrelin and SP in all TEG groups were significantly decreased compared with those in the NC group (ghrelin: 34.721 ± 6.759, 33.547 ± 6.255, 35.141 ± 5.987 vs 43.514 ± 5.323, P < 0.05, P < 0.01, P < 0.01; SP: 13.548 ± 1.078, 13.952 ± 1.246, 11.845 ± 1.567 vs 16.383 ± 2.275, all P < 0.01) and increased compared with the DM group (ghrelin: 26.626 ± 4.596, all P < 0.05; SP: 9.257 ± 1.636, all P < 0.01). However, the differences in ghrelin staining intensities among TEG groups were not statistically significant. The staining intensities for SP in the TEG-L and TEG-M groups were increased compared with the TEG-H group (both P < 0.05).

CONCLUSION: Tegaserod may improve delayed gastric emptying in diabetic rats by enhancing the expression and release of ghrelin and SP.

The effect of single-dose orlistat on postprandial serum glucose, insulin and glucagon-like peptide-1 levels in nondiabetic obese patients

OBJECTIVE

Glucagon-like peptide-1 is an insulin secretion-stimulating gut hormone that is produced in response to food intake. Orlistat (Xenical, F. Hoffman-La Roche, Basel, Switzerland), which decreases fat absorption and increases intestinal fat content, may therefore affect the secretion of glucagon-like peptide-1. In this study we examined the immediate effects of orlistat on postprandial serum glucose, insulin and glucagon-like peptide-1 levels prior to a change in body weight.

DESIGN

Randomized, clinical study.

PATIENTS

Sixteen nondiabetic obese patients (body mass index 35.7 +/- 3.8 kg/m(2), range 32.5-43.1) were enrolled in this study. The patients were randomly assigned to either the group treated with orlistat (120 mg, single dose) or the control group. There were eight patients in each of the two groups. Orlistat was given before a standard 600-kcal mixed meal containing 60% carbohydrates, 25% lipids and 15% protein. Blood samples were collected at baseline and at 30-min intervals for 180 min after the test meal. Graphical tendencies, peak value, time to reach the peak value, and area under the curve in the two groups were compared.

MEASUREMENTS

Blood samples were obtained for the measurement of GLP-1, glucose, insulin, high density lipoprotein, total cholesterol and triglycerides.

RESULTS

We found no difference in sex distribution, mean age, anthropometric measurements, or baseline glucose, insulin and glucagon-like peptide-1 levels between the orlistat and placebo groups. The peak insulin and glucagon-like peptide-1 levels were determined at 60 min in the control group. Hourly changes in serum glucose and insulin levels were similar between the groups, although the peak insulin and glucagon-like peptide-1 levels were reached at 120 min in the orlistat group. There were no statistically significant differences between the groups.

CONCLUSIONS

A single dose of 120-mg orlistat caused no change in postprandial serum glucose, insulin or glucagon-like peptide-1 levels in nondiabetic obese patients. Although glucagon-like peptide-1 increases were delayed in the orlistat group, these changes were nonsignificant.

Load-dependent effects of duodenal glucose on glycemia, gastrointestinal hormones, antropyloroduodenal motility, and energy intake in healthy men

Gastric emptying is a major determinant of glycemia, gastrointestinal hormone release, and appetite. We determined the effects of different intraduodenal glucose loads on glycemia, insulinemia, glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP) and cholecystokinin (CCK), antropyloroduodenal motility, and energy intake in healthy subjects. Blood glucose, plasma hormone, and antropyloroduodenal motor responses to 120-min intraduodenal infusions of glucose at 1) 1 ("G1"), 2) 2 ("G2"), and 3) 4 ("G4") kcal/min or of 4) saline ("control") were measured in 10 healthy males in double-blind, randomized fashion. Immediately after each infusion, energy intake at a buffet meal was quantified. Blood glucose rose in response to all glucose infusions (P < 0.05 vs. control), with the effect of G4 and G2 being greater than that of G1 (P < 0.05) but with no difference between G2 and G4. The rises in insulin, GLP-1, GIP, and CCK were related to the glucose load (r > 0.82, P < 0.05). All glucose infusions suppressed antral (P < 0.05), but only G4 decreased duodenal, pressure waves (P < 0.01), resulted in a sustained stimulation of basal pyloric pressure (P < 0.01), and decreased energy intake (P < 0.05). In conclusion, variations in duodenal glucose loads have differential effects on blood glucose, plasma insulin, GLP-1, GIP and CCK, antropyloroduodenal motility, and energy intake in healthy subjects. These observations have implications for strategies to minimize postprandial glycemic excursions in type 2 diabetes.

Effect of vitamin E on oxidative stress status in small intestine of diabetic rat

AIM: To investigate the effect of vitamin E on oxidative stress status in the small intestine of diabetic rats.

METHODS: Twenty-four male Wistar rats were randomly divided into three groups: Control (C), non-treated diabetic (NTD) and vitamin E-treated diabetic (V_ETD) groups. The increases in lipid peroxidation, protein oxidation and superoxide dismutase (SOD) in these three groups was compared after 6 wk.

RESULTS: There was no significant difference in catalase activity between NTD and control rats. Compared to NTD rats, the treatment with vitamin E significantly decreased lipid peroxidation and protein oxidation, and also increased catalase activity and SOD.

CONCLUSION: The results revealed the occurrence of oxidative stress in the small intestine of diabetic rats. Vitamin E, as an antioxidant, attenuates lipid peroxidation and protein oxidation, and increases antioxidant defense mechanism.

Tripeptides of RS1 (RSC1A1) inhibit a monosaccharide-dependent exocytotic pathway of Na+-D-glucose cotransporter SGLT1 with high affinity

The human gene RSC1A1 codes for a 67-kDa protein named RS1 that mediates transcriptional and post-transcriptional regulation of Na(+)-D-glucose cotransporter SGLT1. The post-transcriptional regulation occurs at the trans-Golgi network (TGN). We identified two tripeptides in human RS1 (Gln-Cys-Pro (QCP) and Gln-Ser-Pro (QSP)) that induce posttranscriptional down-regulation of SGLT1 at the TGN leading to 40-50% reduction of SGLT1 in plasma membrane. For effective intracellular concentrations IC(50) values of 2.0 nM (QCP) and 0.16 nm (QSP) were estimated. Down-regulation of SGLT1 by tripeptides was attenuated by intracellular monosaccharides including non-metabolized methyl-alpha-D-glucopyranoside and 2-deoxyglucose. In small intestine post-transcriptional regulation of SGLT1 may contribute to glucose-dependent regulation of liver metabolism and intestinal mobility. QCP and QSP are transported by the H(+)-peptide cotransporter PepT1 that is colocated with SGLT1 in small intestinal enterocytes. Using coexpression of SGLT1 and PepT1 in Xenopus oocytes or polarized Caco-2 cells that contain both transporters we demonstrated that the tripeptides were effective when applied to the extracellular compartment. After a 1-h perfusion of intact rat small intestine with QSP, glucose absorption was reduced by 30%. The data indicate that orally applied tripeptides can be used to down-regulate small intestinal glucose absorption, e.g. in diabetes mellitus.

Mechanisms of disease: the pathological basis of gastroparesis--a review of experimental and clinical studies

The pathogenesis of gastroparesis is complicated and poorly understood. This lack of understanding remains a major impediment to the development of effective therapies for this condition. Most of the scientific information available on the pathogenesis of gastroparesis has been derived from experimental studies of diabetes in animals. These studies suggest that the disease process can affect nerves (particularly those producing nitric oxide, but also the vagus nerve), interstitial cells of Cajal and smooth muscle. By contrast, human data are sparse, outdated and generally inadequate for the validation of data obtained from experimental models. The available data do, however, suggest that multiple cellular targets are involved. In practice, though, symptoms seldom correlate with objective measures of gastric function and there is still a lot to learn about the pathophysiology of gastroparesis. Future studies should focus on understanding the molecular pathways that lead to gastric dysfunction, in animal models and in humans, and pave the way for the development of rational therapies.

Anesthesia for patients with diabetes mellitus

PURPOSE OF REVIEW

Diabetes mellitus has diverse effects on all organ systems of the body. Insulin physiology and metabolic control are far more complex than previously thought. Research continues to reveal more information about the central role of insulin in metabolism. The treatment of hypertension and nephropathy as well as hyperglycemia in patients with diabetes has emerged as being critical for prevention of long-term diabetic complications. The issue of primary importance to the anesthesiologist is whether strict glycemic and hemodynamic control during the perioperative period affect outcome.

RECENT FINDINGS

Maintenance of euglycemia and physiologic control of insulin responses to changes in glucose levels have been shown to prolong life and reduce complications from diabetes mellitus. The identification and treatment of prediabetic patients may significantly delay the onset of overt diabetes. Perioperative control of glucose has become tighter, but the optimum level of glucose and ideal method of insulin delivery during surgery remain controversial. Perioperative control of blood pressure and vascular responses may be as important as glucose control for prevention of adverse perioperative events.

SUMMARY

Tight long-term control of glucose and blood pressure improve outcome in patients with diabetes. The same philosophy of management is being applied to the perioperative period. Routine measurement of intraoperative blood glucose levels and appropriate insulin administration are now standard practice, but the ideal regimen for insulin administration remains to be determined.

Gastric feed intolerance is not increased in critically ill patients with type II diabetes mellitus

OBJECTIVE

To examine the occurrence of feed intolerance in critically ill patients with previously diagnosed type II diabetes mellitus (DM) who received prolonged gastric feeding.

DESIGN AND SETTING

Retrospective study in a level 3 mixed ICU.

PATIENTS

All mechanically ventilated, enterally fed patients (n = 649), with (n = 118) and without type II DM (n = 531) admitted between January 2003 and July 2005.

INTERVENTIONS

Patients with at least 72 h of gastric feeding were identified by review of case notes and ICU charts. The proportion that developed feed intolerance was determined. All patient received insulin therapy.

RESULTS

The proportion of patients requiring gastric feeding for at least 72 h was similar between patients with and without DM (42%, 50/118, vs. 42%, 222/531). Data from patients with DM were also compared with a group of 50 patients matched for age, sex and APACHE II score, selected from the total non-diabetic group. The occurrence of feed intolerance (DM 52% vs. matched non-DM 50% vs. unselected non-diabetic 58%) and the time taken to develop feed intolerance (DM 62.6 +/- 43.8 h vs. matched non-DM 45.3 +/- 54.6 vs. unselected non-diabetic 50.6 +/- 59.5) were similar amongst the three groups. Feed intolerance was associated with a greater use of morphine/midazolam and vasopressor support, a lower feeding rate and a longer ICU length of stay.

CONCLUSIONS

In critically ill patients who require prolonged enteral nutrition, a prior history of DM type II does not appear to be a further risk factor for feed intolerance.

Gut sensations in diabetic autonomic neuropathy

The pathogenesis of gastrointestinal symptoms in diabetes mellitus is complex and multi-factorial. Diabetes induced peripheral and central changes in the neuronal pain matrix may be of importance and were explored using a new multi-modal and multi-segmental sensory testing approach. The sensitivity to mechanical, thermal and electrical stimulations in the oesophagus and duodenum was assessed in 12 type-1 diabetic patients with proven autonomic neuropathy and severe gastrointestinal symptoms using a comprehensive stimulation device aiming to activate different gut nerves and pain mechanisms. Twelve healthy subjects served as controls. The sensory response and the somatic referred pain areas were recorded. In the diabetic patients an overall hyposensitivity to the combination of all stimulations was found in the oesophagus and duodenum (P=0.02). Post hoc analysis revealed hyposensitivity to mechanical stimulations in the oesophagus (P=0.006) and duodenum (P=0.002), and to thermal (P<0.001) and electrical (P=0.005) stimulations in the oesophagus and duodenum combined. The hyposensitivity in the gut was accompanied by a 46% increase in the somatic referred pain areas (P=0.04) indicating central neuronal changes. The multi-modal and multi-segmental sensory testing approach indicates that the sensory nerves are widely affected in the GI tract and generalized to nerves in all layers of the gut. Changes in the neuronal pain matrix including interactions between peripheral and central pain mechanisms may be involved in the pathogenesis of gastrointestinal symptoms in long-standing diabetes. Future targets in the treatment of gastrointestinal symptoms in diabetic patients with autonomic neuropathy could be based on modulation of the central nervous system excitability.

Glycemic effect of administration of epinephrine-containing local anaesthesia in patients undergoing dental extraction, a comparison between healthy and diabetic patients

OBJECTIVES

To compare the effect of administration of epinephrine (in the dental local anesthetic solution) on blood glucose concentration in healthy and diabetic dental patients after extraction. To determine if there is any correlation between blood glucose level changes and the number of carpules injected, number of teeth extracted and the gender of the patient.

MATERIALS AND METHOD

An open study of 60 patients (30 healthy and 30 diabetics) visiting the Oral Surgery clinic of Ajman University of Science and Technology. A drop of blood was taken from the tip of the patient's finger and placed on a glucometer strip to determine the pre-operative blood glucose level. Dental local anaesthesia (1.8 ml carpule each) containing 1:80,000 epinephrine was injected either through infiltration or block. Extraction was carried out atraumatically and 10 minutes post-extraction the glucose measurement was taken.

RESULTS

The difference in the blood glucose levels pre- and post operatively were not significantly different (p > 0.05) when a comparison was made between the healthy and diabetic groups. Comparison of glucose changes in diabetics who had taken their hypoglycaemic medication and those who had not, showed a significant difference (p < 0.05). Statistical analysis showed no correlation between the blood glucose level changes and the number of carpules used, number of teeth extracted and gender.

CONCLUSION

Dental local anaesthetic solution containing epinephrine is safe to use in all healthy and diabetic patients (irrespective of their gender), excepting those diabetics who have not taken their pre-operative hypoglycaemic medication. There is no relation between the post-extraction glucose changes and the number of carpules used, number of teeth extracted or gender.

Autonomic Peripheral Neuropathy

Most generalized peripheral polyneuropathies are accompanied by clinical or subclinical autonomic dysfunction. There is a group of peripheral neuropathies in which the small or unmyelinated fibers are selectively targeted. In these neuropathies, autonomic dysfunction is the most prominent manifestation. The features associated with an autonomic neuropathy include impairment of cardiovascular, gastrointestinal, urogenital, thermoregulatory, sudomotor, and pupillomotor autonomic function.

Proximal gastric motility in critically ill patients with type 2 diabetes mellitus

AIM: To investigate the proximal gastric motor response to duodenal nutrients in critically ill patients with long-standing type 2 diabetes mellitus.

METHODS: Proximal gastric motility was assessed (using a barostat) in 10 critically ill patients with type 2 diabetes mellitus (59 ± 3 years) during two 60-min duodenal infusions of Ensure^® (1 and 2 kcal/min), in random order, separated by 2 h fasting. Data were compared with 15 non-diabetic critically ill patients (48 ± 5 years) and 10 healthy volunteers (28 ± 3 years).

RESULTS: Baseline proximal gastric volumes were similar between the three groups. In diabetic patients, proximal gastric relaxation during 1 kcal/min nutrient infusion was similar to non-diabetic patients and healthy controls. In contrast, relaxation during 2 kcal/min infusion was initially reduced in diabetic patients (p < 0.05) but increased to a level similar to healthy humans, unlike non-diabetic patients where relaxation was impaired throughout the infusion. Duodenal nutrient stimulation reduced the fundic wave frequency in a dose-dependent fashion in both the critically ill diabetic patients and healthy subjects, but not in critically ill patients without diabetes. Fundic wave frequency in diabetic patients and healthy subjects was greater than in non-diabetic patients.

CONCLUSION: In patients with diabetes mellitus, proximal gastric motility is less disturbed than non-diabetic patients during critical illness, suggesting that these patients may not be at greater risk of delayed gastric emptying.

Pathophysiology and management of diabetic gastropathy: a guide for endocrinologists

Delayed gastric emptying is frequently observed in patients with long-standing type 1 and type 2 diabetes mellitus, and potentially impacts on upper gastrointestinal symptoms, glycaemic control, nutrition and oral drug absorption. The pathogenesis remains unclear and management strategies are currently suboptimal. Therapeutic strategies focus on accelerating gastric emptying, controlling symptoms and improving glycaemic control. The potential adverse effects of hyperglycaemia on gastric emptying and upper gut symptoms indicate the importance of normalising blood glucose if possible. Nutritional and psychological supports are also important, but often neglected. A number of recent pharmacological and non-pharmacological therapies show promise, including gastric electrical stimulation. As with all chronic illnesses, a multidisciplinary approach to management is recommended, but there are few data regarding long-term outcomes.

Exenatide

Exenatide (Byetta) is a novel, synthetic, incretin mimetic, glucoregulatory peptide approved in the US and Europe for the treatment of patients with type 2 diabetes mellitus who have inadequate glycaemic control despite receiving treatment with maximum tolerated doses of metformin and/or a sulfonylurea. In randomised, controlled, phase III trials and post hoc completer analyses in this patient population, the addition of subcutaneous exenatide twice daily significantly improved glycaemic control and was associated with progressive and significant bodyweight reduction from baseline for up to 2 years. The overall intensity of glycaemic control with exenatide was similar to that achieved with once-daily insulin glargine or twice-daily biphasic insulin aspart. Exenatide was generally well tolerated. Most adverse events were mild to moderate in severity and gastrointestinal in nature. The overall rate of hypoglycaemia was similar to rates observed with placebo (when administered with metformin) and insulin comparators (when administered with metformin and a sulfonylurea). The addition of exenatide to therapy with metformin and a sulfonylurea provided significant improvements in treatment satisfaction and patients' health-related quality of life (HR-QOL). The drug was also cost effective compared with pioglitazone, glibenclamide (glyburide), insulin glargine (all in combination with metformin and/or a sulfonylurea) and metformin alone. Overall, adjunctive therapy with exenatide is a valuable therapeutic option in patients with type 2 diabetes requiring moderate improvements in glycaemic control despite treatment with metformin and/or a sulfonylurea.

Pramlintide acetate in the treatment of Type 2 and Type 1 diabetes mellitus

Maintenance of glucose homeostasis involves the interplay of multiple glucoregulatory factors, including the pancreatic β-cell hormones insulin and amylin. Amylin, a neuroendocrine hormone, is secreted in response to nutrient intake and suppresses postprandial glucagon secretion, helps regulate gastric emptying, and reduces food intake. Patients with diabetes are deficient in both insulin and amylin - contributing to postprandial hyperglycemia. Pramlintide, an analogue of amylin, is the active ingredient in the SYMLIN^® (pramlintide acetate) injection. SYMLIN is indicated as an adjunctive treatment for insulin-using patients with diabetes and works through mechanisms similar to those of amylin. Clinical trials have demonstrated that pramlintide therapy improves postprandial glucose control, lowers A1C, and is accompanied by a reduction in body weight. Mild-to-moderate nausea and an increased risk of insulin-induced severe hypoglycemia have been the most common side effects. These side effects can be mitigated by gradual pramlintide dose escalation during treatment initiation and proactive mealtime insulin dose reduction upon initiation of pramlintide therapy.

An update on autonomic neuropathy affecting the gastrointestinal tract

Gastrointestinal symptoms and disordered gut motility occur frequently in the diabetic population and are generally regarded as manifestations of gastrointestinal "autonomic dysfunction," although the relationships between both symptoms and dysmotility with abnormal cardiovascular autonomic function are weak. It is now recognized that the blood glucose concentration is both a determinant of and determined by gastrointestinal function. An improved definition of the underlying pathophysiology should facilitate the development of therapies that are targeted more effectively.

Pramlintide: A new tool in diabetes management

The amylin analogue pramlintide acts in concert with insulin to regulate glucose metabolism. It reduces postprandial hyperglycemia by suppressing postprandial glucagon secretion, regulating gastric emptying, and reducing food intake. In clinical use, pramlintide reduces postprandial glycemic excursions and improves A(1c) without the weight gain and increased risk of hypoglycemia typically seen with intensification of diabetes therapy.

Effects of lipase inhibition on gastric emptying and alcohol absorption in healthy subjects

The rate of alcohol absorption is dependent on gastric emptying (GE). As the slowing of GE by fat is dependent on lipolysis, orlistat may increase the rise in blood alcohol when alcohol is consumed with, or after, fat. The aim of the study was to evaluate the effects of orlistat on GE and blood alcohol after an alcohol-containing drink following a fat 'preload', in healthy subjects. Ten healthy males consumed 120 ml cream with or without 120 mg orlistat, 30 min before an alcohol-containing drink labelled with 20 MBq [(99 m)Tc]sulfur colloid on 2 d. GE, plasma alcohol and blood glucose were measured. GE was slightly faster with orlistat (P<0.05) compared with control. Plasma alcohol at 15 min was slightly higher with orlistat (0.034 (SEM 0.006) g/100 ml) v. control (0.029 (SEM 0.005) g/100 ml) (P<0.05), but there was no effect on the area under the curve 0-240 min. The increase in blood glucose was greater with orlistat, for example, at 15 min (1.07 (SEM 0.2) mmol/l) v. control (0.75 (SEM 0.2) mmol/l) (P=0.05). The rise in blood glucose and plasma alcohol were related (for example, at 15 min r 0.49; P=0.03). In conclusion, lipase inhibition accelerates GE of an alcohol-containing drink following a fat 'preload' with a minor increase in the initial rise in plasma alcohol.

Management of Type 2 diabetes: the role of incretin mimetics

Type 2 diabetes is characterised by insulin resistance and progressive beta-cell dysfunction (which leads to hyperglycaemia), the risk of progressive worsening of glycaemic control and an increased risk of both macrovascular and microvascular complications. Existing treatment strategies target deficient insulin secretion and insulin resistance, but do not generally address the underlying progressive beta-cell dysfunction that is common to Type 2 diabetes. Traditionally, Type 2 diabetes is first treated with medical nutrition therapy (reduced food intake and increased physical activity), followed by stepwise addition of oral antidiabetes therapies and, ultimately, exogenous insulin, as required. Unfortunately, these approaches have not been shown to delay the need for additional therapies, nor do they generally prevent or delay the inexorable decline in beta-cell function. Patients with Type 2 diabetes commonly experience deterioration in glycaemic control, and may have substantial weight gain due to the diabetes therapies that contribute to worsening obesity. In addition, insulin-providing therapies, such as sulfonylureas and exogenous insulin, carry the risk of hypoglycaemia, and cannot fully address the complex hormonal irregularities that characterise Type 2 diabetes, including the role of glucagon hypersecretion. New therapeutic approaches are being developed that couple durable glycaemic control with improved control of body weight. These approaches include development of the incretin mimetics, which are a novel class of agents that share several of the glucoregulatory effects of incretin hormones, such as glucagon-like hormone-1. Deficiency of glucagon-like hormone-1 secretion is known to be present in those with abnormal glucose tolerance. Agents that manipulate the physiological actions of incretin hormones, such as glucagon-like hormone-1, may significantly benefit patients with Type 2 diabetes.

Upper gastrointestinal function and glycemic control in diabetes mellitus

Recent evidence has highlighted the impact of glycemic control on the incidence and progression of diabetic micro- and macrovascular complications, and on cardiovascular risk in the non-diabetic population. Postprandial blood glucose concentrations make a major contribution to overall glycemic control, and are determined in part by upper gastrointestinal function. Conversely, poor glycemic control has an acute, reversible effect on gastrointestinal motility. Insights into the mechanisms by which the gut contributes to glycemia have given rise to a number of novel dietary and pharmacological strategies designed to lower postprandial blood glucose concentrations.

Oesophageal dysmotility, delayed gastric emptying and autonomic neuropathy correlate to disturbed glucose homeostasis

AIMS/HYPOTHESIS

Among diabetic patients, glucose homeostasis may be affected by abnormal gastrointestinal motility and autonomic neuropathy. This study analysed whether oesophageal dysmotility, delayed gastric emptying or autonomic neuropathy affect glucose homeostasis.

MATERIALS AND METHODS

Oesophageal manometry and gastric emptying scintigraphy were performed in 20 diabetic patients. Heart-rate variation during deep breathing (expiration/inspiration [E/I] ratio) and continuous subcutaneous glucose concentrations for a period of 72 h were also monitored in the same patients.

RESULTS

Oesophageal dysmotility was found in eight of 14 patients. Eleven of 20 patients had delayed gastric emptying (abnormal gastric emptying half-time [T (50)]) and nine of 18 had an abnormal E/I ratio. Complaints of abdominal fullness were predictive of delayed gastric emptying. A low peristaltic speed of the oesophagus was associated with impaired T (50) (r ( s )=-0.67; p=0.02). One hour after breakfast, subcutaneous glucose levels decreased in patients with delayed gastric emptying but continued to rise in those with normal emptying. Consequently, the median glucose level 2.5 h after breakfast was lower in the former (9.1 [4.2-12.5] vs 14.3 [11.2-17.7] mmol/l; p<0.05). Glucose fluctuations during the 72 h were significantly higher in patients with an abnormal E/I ratio than in those with a normal E/I ratio (coefficient of variation: 41 [46-49] vs 28 [27-34]%; p=0.008).

CONCLUSIONS/INTERPRETATION

Abdominal fullness predicted delayed gastric emptying that was associated with diminished glucose uptake after breakfast. Low oesophageal peristaltic speed was associated with slow gastric emptying whereas parasympathetic neuropathy was associated with increased glucose variations.

Oesophageal motility disorders in type 1 diabetes mellitus and their relation to cardiovascular autonomic neuropathy

The relationship between cardiovascular autonomic neuropathy (CVAN) and oesophageal dysfunction in diabetes mellitus has not been well established because reports are contradictory. The aim of this study was to assess oesophageal function and its correlation with CVAN in type 1 diabetic patients without oesophageal symptoms. Forty-six type 1 diabetic patients without oesophageal symptoms (DG) and 34 healthy volunteers (CG) were studied. Both groups underwent CVAN tests and oesophageal manometry and pH-metry. Differences between groups regarding results of cardiovascular autonomic tests and oesophageal studies were statistically analysed. Compared with the CG, the DG group showed insufficient lower oesophageal sphincter (LOS) relaxation and a higher percentage of simultaneous waves (P < 0.01). Patients with CVAN (n = 22) showed a higher prevalence of pathological simultaneous contractions (>10%), and the prevalence of simultaneous waves related to the degree of autonomic neuropathy was: 9% of patients without CVAN, 7% of those suspected to have it and 50% of patients with CVAN (P < 0.001). Factors associated with the presence of pathological simultaneous waves (>10%) were the presence of CVAN and duration of diabetes (P < 0.05, logistic regression analysis). Increase in simultaneous waves and impaired relaxation of LOS are more frequent in diabetic patients with CVAN.

The physiology of amylin and insulin: maintaining the balance between glucose secretion and glucose uptake

Glucose homeostasis is accomplished through intricate, and arguably, elegant interactions among several organs and hormones. Historically, glucose homeostasis has been viewed somewhat narrowly--insulin from pancreatic beta cells regulated glucose disposal, while glucagon from pancreatic alpha [corrected] cells regulated glucose appearance during fasting states. But more recent characterization and understanding of the role of incretin hormones from the gut--notably, glucagon-like peptide 1 and gastric inhibitory polypeptide--and amylin from pancreatic beta cells has led to a more complete model of glucose homeostasis. Furthermore, availability of pharmacologic agents to replace, mimic, or enhance the actions of these hormones allows application of this more complete model of glucose homeostasis to the treatment of type 1 and type 2 diabetes. This article provides an overview of the role of the pancreatic hormone amylin in glucose homeostasis and of Pramlintide, a analogue of native amylin, recently approved as adjunct therapy to insulin in people with type 1 and type 2 diabetes.

Interim analysis of the effects of exenatide treatment on A1C, weight and cardiovascular risk factors over 82 weeks in 314 overweight patients with type 2 diabetes

AIM

Exenatide, an incretin mimetic for the adjunct treatment of type 2 diabetes (DM2), reduced A1C and weight in 30-week placebo-controlled trials. This analysis examined the effects of exenatide on glycaemic control and weight over an 82-week period in patients with DM2 unable to achieve adequate glycaemic control with sulphonylurea (SU) and/or metformin (MET).

METHODS

This interim analysis is of 314 patients who received exenatide in the 30-week placebo-controlled trials and subsequently in 52 weeks of open-label uncontrolled extension studies for 82 weeks of exenatide in total. Patients continued their SU and/or MET regimens throughout.

RESULTS

Patients completed 82 weeks of exenatide treatment [n = 314, 63% M, age 56 +/- 10 years, weight 99 +/- 21 kg, body mass index 34 +/- 6 kg/m2, A1C 8.3 +/- 1.0% (mean +/- SD)]. Reduction in A1C from baseline to week 30 [-0.9 +/- 0.1% (mean +/- SE)] was sustained to week 82 (-1.1 +/- 0.1%), with 48% of patients achieving A1C < or = 7% at week 82. At week 30, exenatide reduced body weight (a secondary endpoint) from baseline (-2.1 +/- 0.2 kg), with progressive reduction at week 82 (-4.4 +/- 0.3 kg). Similar results were observed for the intent-to-treat population (n = 551), with reductions in A1C and weight at week 82 of -0.8 +/- 0.1% and -3.5 +/- 0.2 kg respectively. The 82-week completer cohort showed statistically significant improvement in some cardiovascular risk factors. The most frequent adverse events were generally mild-to-moderate nausea and hypoglycaemia.

CONCLUSION

In summary, 82 weeks of adjunctive exenatide treatment in patients with DM2 treated with SU and/or MET resulted in sustained reduction in A1C and progressive reduction in weight, as well as improvement in some cardiovascular risk factors.

Long-standing type II diabetes mellitus is not a risk factor for slow gastric emptying in critically ill patients

OBJECTIVE

Delayed gastric emptying (GE) is common both in critical illness and in patients with diabetes mellitus (DM). The effect of DM on the incidence of slow GE in these patients is unknown. We evaluated the effect of DM on liquid GE in critically ill patients.

METHODS

Retrospective analysis of GE using a standard [13C]octanoic acid breath test in 12 type 2 DM patients compared with (a) 44 critically ill patients without DM, including (b) a subgroup of 15 age- and sex-matched patients and (c) 15 healthy volunteers. We determined the gastric emptying coefficient (GEC) and the gastric half-emptying time (t50). Mean APACHE II scores, blood glucose levels and use of morphine were similar between patient groups.

RESULTS

GE was faster in critically ill patients with DM (t50 122 +/- 11 min, GEC: 3.8 +/- 0.3) than in patients without DM (t50 168 +/- 16 min, GEC 2.8 +/- 0.1) and in age- and sex-matched controls (t50 165 +/- 13 min, GEC 2.7 +/- 0.2) and was similar to that in healthy volunteers (t50 148 +/- 13 min, GEC 3.5 +/- 0.1). The proportion of patients with slow emptying (GEC < 3.2) was greater in non-DM (all = 56%, matched = 60%) than in DM patients (25%) and healthy subjects (26%).

CONCLUSION

Long-standing type diabetes mellitus is not a risk factor for slow GE in critically ill patients.