Cross-genetic determination of maternal and neonatal immune mediators during pregnancy

BACKGROUND

The immune system plays a fundamental role in development during pregnancy and early life. Alterations in circulating maternal and neonatal immune mediators have been associated with pregnancy complications as well as susceptibility to autoimmune and neurodevelopmental conditions in later life. Evidence suggests that the immune system in adults not only responds to environmental stimulation but is also under strong genetic control.

METHODS

This is the first genetic study of > 700 mother-infant pairs to analyse the circulating levels of 22 maternal mid-gestational serum-derived and 42 neonatal bloodspot-derived immune mediators (cytokines/chemokines) in the context of maternal and fetal genotype. We first estimated the maternal and fetal genome-wide SNP-based heritability (h2g) for each immune molecule and then performed genome-wide association studies (GWAS) to identify specific loci contributing to individual immune mediators. Finally, we assessed the relationship between genetic immune determinants and ASD outcome.

RESULTS

We show maternal and neonatal cytokines/chemokines displaying genetic regulation using independent methodologies. We demonstrate that novel fetal loci for immune function independently affect the physiological levels of maternal immune mediators and vice versa. The cross-associated loci are in distinct genomic regions compared with individual-specific immune mediator loci. Finally, we observed an interaction between increased IL-8 levels at birth, autism spectrum disorder (ASD) status, and a specific maternal genotype.

CONCLUSIONS

Our results suggest that maternal and fetal genetic variation influences the immune system during pregnancy and at birth via distinct mechanisms and that a better understanding of immune factor determinants in early development may shed light on risk factors for developmental disorders.

Prenatal Stress, Maternal Immune Dysregulation, and Their Association With Autism Spectrum Disorders

PURPOSE OF REVIEW

While genetic factors are a major etiological contributor to autism spectrum disorder (ASD), evidence also supports a role for environmental factors. Herein, we will discuss two such factors that have been associated with a significant proportion of ASD risk: prenatal stress exposure and maternal immune dysregulation, and how sex and gender relate to these factors.

RECENT FINDINGS

Recent evidence suggests that maternal stress susceptibility interacts with prenatal stress exposure to affect offspring neurodevelopment. Additionally, understanding of the impact of maternal immune dysfunction on ASD has recently been advanced by recognition of specific fetal brain proteins targeted by maternal autoantibodies, and identification of unique mid-gestational maternal immune profiles. Animal models have been developed to explore pathophysiology targeting both of these factors, with limited sex-specific effects observed. While prenatal stress and maternal immune dysregulation are associated with ASD, most cases of these prenatal exposures do not result in ASD, suggesting interaction with multiple other risks. We are beginning to understand the behavioral, pharmacopathological, and epigenetic effects related to these interactions, as well as potential mitigating factors. Sex differences of these risks have been understudied but are crucial for understanding the higher prevalence of ASD in boys. Continued growth in understanding of these mechanisms may ultimately allow for the identification of multiple potential points for prevention or intervention, and for a personalized medicine approach for this subset of environmental-associated ASD cases.

Effect of gender on the acute effects of whey protein ingestion on energy intake, appetite, gastric emptying and gut hormone responses in healthy young adults

BACKGROUND/OBJECTIVES

Protein supplements, usually drinks rich in whey protein, are used widely for weight loss purposes in overweight adults. Information comparing the effects of whey protein on appetite and energy intake in men and women is limited. The objective was to compare the acute effects of whey-protein intake on energy intake, appetite, gastric emptying and gut hormones in healthy young men and women.

SUBJECTS/METHODS

Gastric emptying (3D-ultrasonography), blood glucose and plasma insulin, glucagon, ghrelin, cholecystokinin (CCK), gastric inhibitory polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) concentrations (0-180 min), appetite (visual analogue scales), and ad libitum energy intake from a buffet meal (180-210 min) were determined after ingestion of 30 g (120 kcal) or 70 g (280 kcal) whey protein, or a flavoured-water control drink (~2 kcal) in 8 healthy young men (25 ± 2 y, 72 ± 3 kg, 23 ± 1 kg/m²) and 8 women (23 ± 1 y, 64 ± 2 kg, 24 ± 0.4 kg/m²).

RESULTS

There was a protein-load effect on gastric emptying, blood glucose, plasma insulin, glucagon, ghrelin, CCK, GIP and GLP-1 concentrations, and perceptions of hunger, desire to eat and prospective food consumption (P < 0.05). Ad libitum energy intake (average decrease of 206 ± 39 kcal (15 ± 2%) for men and of 46 ± 54 kcal (0 ± 26%) for women for the mean of the intakes after the 30 and 70 g whey-protein loads) and hunger were suppressed more by whey-protein ingestion in men than women (P = 0.046). There was no difference in suppression of energy intake between the 30 and 70 g protein loads (P = 0.75, interaction effect P = 0.19). Consequently, total energy intake (protein drink plus buffet meal) increased more compared to control in women than men (P = 0.010). The drinks emptied more slowly, and plasma glucagon, CCK and GLP-1 increased less after the protein drinks, in women than men (P < 0.05).

CONCLUSION

The acute effects of whey protein ingestion on appetite, energy intake, gastric emptying and gut hormone responses are influenced by gender in healthy young adults.

Effects of intraduodenal administration of the artificial sweetener sucralose on blood pressure and superior mesenteric artery blood flow in healthy older subjects

BACKGROUND

Postprandial hypotension (PPH) occurs frequently, particularly in older people and those with type 2 diabetes, and is associated with increased morbidity and mortality. The magnitude of the decrease in blood pressure (BP) induced by carbohydrate, fat, and protein appears to be comparable and results from the interaction of macronutrients with the small intestine, including an observed stimulation of mesenteric blood flow. It is not known whether artificial sweeteners, such as sucralose, which are widely used, affect BP.

OBJECTIVE

The aim of this study was to evaluate the effects of intraduodenal sucralose on BP and superior mesenteric artery (SMA) blood flow, compared with intraduodenal glucose and saline (control), in healthy older subjects.

DESIGN

Twelve healthy subjects (6 men, 6 women; aged 66-79 y) were studied on 3 separate occasions in a randomized, double-blind, crossover design. After an overnight fast, subjects had concurrent measurements of BP and heart rate (HR; automated device), SMA blood flow (Doppler ultrasound), and blood glucose (glucometer) during intraduodenal infusion of 1) glucose (25% wt:vol, ∼1400 mOsmol/L), 2) sucralose (4 mmol/L, ∼300 mOsmol/L), or 3) saline (0.9% wt:vol, ∼300 mOsmol/L) at a rate of 3 mL/min for 60 min followed by intraduodenal saline for a further 60 min.

RESULTS

There was a decrease in mean arterial BP (P < 0.001) during intraduodenal glucose [baseline (mean ± SEM): 91.7 ± 2.6 mm Hg compared with t = 60 min: 85.9 ± 2.8 mm Hg] but not during intraduodenal saline or intraduodenal sucralose. The HR (P < 0.0001) and SMA blood flow (P < 0.0001) also increased during intraduodenal glucose but not during intraduodenal saline or intraduodenal sucralose. As expected, blood glucose concentrations increased in response to glucose (P < 0.0001) but not saline or sucralose.

CONCLUSIONS

In healthy older subjects, intraduodenal administration of the artificial sweetener sucralose was not associated with changes in BP or SMA blood flow. Further studies are therefore warranted to determine the potential role for artificial sweeteners as a therapy for PPH. This trial was registered at http://www.ANZCTR.org.au as ACTRN12617001249347.

Effects of Glutamine on Gastric Emptying of Low- and High-Nutrient Drinks in Healthy Young Subjects-Impact on Glycaemia

Glutamine is a potent stimulus for the release of glucagon-like peptide-1, which increases postprandial insulin and slows gastric emptying (GE). We determined the effects of glutamine on GE of, and glycaemic responses to, low- and high-nutrient drinks in eight healthy males (mean age 21.6 ± 0.7 years and BMI 22.9 ± 0.7 kg/m²). Participants were studied on four occasions on which they consumed either a low-nutrient (beef soup; 18 kcal) or high-nutrient (75 g dextrose; 255 kcal) drink, each with or without 30 g of glutamine (120 kcal), in a randomised, crossover design. GE (2D ultrasound), blood glucose and plasma insulin concentrations were measured concurrently. Glutamine slowed GE (half emptying time (T50)) of both low- (45 ± 3 min vs. 26 ± 2 min, p < 0.001), and high-nutrient, (100 ± 5 min vs. 77 ± 5 min, p = 0.03) drinks, however, there was no effect on GE of the high nutrient drinks when expressed as kcal/min (3.39 ± 0.21 kcal/min vs. 3.81 ± 0.20 kcal/min, p = 0.25). There was no change in blood glucose after the low-nutrient drinks with or without glutamine, despite a slight increase in plasma insulin with glutamine (p = 0.007). The rise in blood glucose following the high-nutrient drink (p = 0.0001) was attenuated during the first 60 min by glutamine (p = 0.007). We conclude that in healthy subjects, glutamine slows GE of both low- and high-nutrient drinks comparably and attenuates the rise in blood glucose after the high-nutrient glucose drink.

Postprandial hypotension in older survivors of critical illness

PURPOSE

In older people postprandial hypotension occurs frequently; and is an independent risk factor for falls, cardiovascular events, stroke and death. The primary aim of this pilot study was to estimate the frequency of postprandial hypotension and evaluate the mechanisms underlying this condition in older survivors of an Intensive Care Unit (ICU).

MATERIALS AND METHODS

Thirty-five older (>65 years) survivors were studied 3 months after discharge. After an overnight fast, participants consumed a 300 mL drink containing 75 g glucose, labelled with 20 MBq ^99mTc-calcium phytate. Patients had concurrent measurements of blood pressure, heart rate, blood glucose and gastric emptying following drink ingestion. Proportion of participants is presented as percent (95% CI) and continuous variables as mean (SD).

RESULTS

Postprandial hypotension was evident in 10 (29%; 95% CI 14-44), orthostatic hypotension in 2 (6%; 95% CI 0-13) and cardiovascular autonomic dysfunction in 2 (6%; 95% CI 0-13) participants. The maximal postprandial nadir for systolic blood pressure and diastolic blood pressures were -29 (14) mmHg and -18 (7) mmHg.

CONCLUSIONS

In this cohort of older survivors of ICU postprandial hypotension occurred frequently . This suggests that postprandial hypotension is an unrecognised issue in older ICU survivors.

Gastrointestinal Symptoms in Diabetes: Prevalence, Assessment, Pathogenesis, and Management

If you haven't measured something, you really don't know much about it.-Karl Pearson (attributed)Gastrointestinal (GI) symptoms represent an important and often unappreciated cause of morbidity in diabetes, although the significance of this burden across the spectrum of patients and the underlying pathophysiology, including the relationship of symptoms with glycemic control, remain poorly defined. The relevance of GI symptoms and the necessity for their accurate assessment have increased with the greater focus on the gut as a therapeutic target for glucose lowering. This review addresses the prevalence, assessment, pathogenesis, and management of GI symptoms in diabetes, beginning with broad principles and then focusing on specific segments of the GI tract. We initially performed a literature search of PubMed by using synonyms and combinations of the following search terms: "gastrointestinal symptoms", "diabetes", "prevalence", "pathogenesis", "diagnosis", and "management". We restricted the search results to English only. Review papers and meta-analyses are presented as the highest level of evidence where possible followed by randomized controlled trials, uncontrolled trials, retrospective and observational data, and expert opinion.

Identification of the antigenic epitopes of maternal autoantibodies in autism spectrum disorders

Several groups have described the presence of fetal brain-reactive maternal autoantibodies in the plasma of some mothers whose children have autism spectrum disorder (ASD). We previously identified seven autoantigens targeted by these maternal autoantibodies, each of which is expressed at significant levels in the developing brain and has demonstrated roles in typical neurodevelopment. To further understand the binding repertoire of the maternal autoantibodies, as well as the presence of any meaningful differences with respect to the recognition and binding of these ASD-specific autoantibodies to each of these neuronal autoantigens, we utilized overlapping peptide microarrays incubated with maternal plasma samples obtained from the Childhood Autism Risk from Genetics and Environment (CHARGE) Study. In an effort to identify the most commonly recognized (immunodominant) epitope sequences targeted by maternal autoantibodies for each of the seven ASD-specific autoantigens, arrays were screened with plasma from mothers with children across diagnostic groups (ASD and typically developing (TD)) that were positive for at least one antigen by western blot (N = 67) or negative control mothers unreactive to any of the autoantigens (N = 18). Of the 63 peptides identified with the discovery microarrays, at least one immunodominant peptide was successfully identified for each of the seven antigenic proteins using subsequent selective screening microarrays. Furthermore, while limited by our relatively small sample size, there were peptides that were distinctly recognized by autoantibodies relative to diagnosis For example, reactivity was observed exclusively in mothers of children of ASD towards several peptides, including the LDH-B peptides DCIIIVVSNPVDILT (9.1% ASD vs. 0% TD; odds ratio (95% CI) = 6.644 (0.355-124.384)) and PVAEEEATVPNNKIT (5.5% ASD vs. 0% TD; odds ratio (95% CI) = 4.067 (0.203-81.403)).These results suggest that there are differences in the binding repertoire between the antigen positive ASD and TD maternal samples. Further, the autoantibodies in plasma from mothers of children with ASD bound to a more diverse set of peptides, and there were specific peptide binding combinations observed only in this group. Future studies are underway to determine the critical amino acids necessary for autoantibody binding, which will be essential in developing a potential therapeutic strategy for maternal autoantibody related (MAR) ASD.

Comparative effects of small intestinal glucose on blood pressure, heart rate, and noradrenaline responses in obese and healthy subjects

Meal consumption leads to an increase in sympathetic output to compensate for hemodynamic changes and maintain blood pressure (BP). Obesity is associated with a blunting of the sympathetic response to meal ingestion, but interpretation of studies investigating these responses is compromised by their failure to account for the rate of gastric emptying, which is an important determinant of postprandial cardiovascular and sympathetic responses and, in both health and obesity, exhibits a wide interindividual variation. We sought to determine the effects of intraduodenal glucose infusion, bypassing gastric emptying, on BP, heart rate (HR), and noradrenaline responses in obese and healthy control subjects. 12 obese subjects (age 36.6 ± 3.9 years, body mass index (BMI) 36.1 ± 1.3 kg/m2 ) and 23 controls (age 27.8 ± 2.4 years, BMI 22.4 ± 0.5 kg/m2 ) received intraduodenal infusions of glucose at 1 or 3 kcal/min, or saline, for 60 min (t = 0-60 min), followed by intraduodenal saline (t = 60-120 min). BP and HR were measured with an automatic cuff, and blood samples collected for measurement of plasma noradrenaline. Intraduodenal glucose at 1 kcal/min was associated with a fall in diastolic BP in the control subjects only (P < 0.01), with no change in systolic BP, HR or noradrenaline in either group. In both groups, intraduodenal glucose at 3 kcal/min was associated with a fall in diastolic (P < 0.01), but not systolic, BP, and rises in HR (P < 0.001) and plasma noradrenaline (P < 0.01), with no difference in responses between the groups. We conclude that cardiovascular and sympathetic responses to intraduodenal glucose infusion are comparable between obese and control subjects, and dependent on the rate of glucose delivery.

Effects of Substitution, and Adding of Carbohydrate and Fat to Whey-Protein on Energy Intake, Appetite, Gastric Emptying, Glucose, Insulin, Ghrelin, CCK and GLP-1 in Healthy Older Men-A Randomized Controlled Trial

Protein-rich supplements are used widely for the management of malnutrition in the elderly. We reported previously that the suppression of energy intake by whey protein is less in older than younger adults. The aim was to determine the effects of substitution, and adding of carbohydrate and fat to whey protein, on ad libitum energy intake from a buffet meal (180-210 min), gastric emptying (3D-ultrasonography), plasma gut hormone concentrations (0-180 min) and appetite (visual analogue scales), in healthy older men. In a randomized, double-blind order, 13 older men (75 ± 2 years) ingested drinks (~450 mL) containing: (i) 70 g whey protein (280 kcal; 'P₂₈₀'); (ii) 14 g protein, 28 g carbohydrate, 12.4 g fat (280 kcal; 'M₂₈₀'); (iii) 70 g protein, 28 g carbohydrate, 12.4 g fat (504 kcal; 'M₅₀₄'); or (iv) control (~2 kcal). The caloric drinks, compared to a control, did not suppress appetite or energy intake; there was an increase in total energy intake (drink + meal, p < 0.05), which was increased most by the M₅₀₄-drink. P₂₈₀- and M₅₀₄-drink ingestion were associated with slower a gastric-emptying time (n = 9), lower ghrelin, and higher cholecystokinin (CCK) and glucagon-like peptide-1 (GLP-1) than M₂₈₀ (p < 0.05). Glucose and insulin were increased most by the mixed-macronutrient drinks (p < 0.05). In conclusion, energy intake was not suppressed, compared to a control, and particularly whey protein, affected gastric emptying and gut hormone responses.

GABAB receptors suppress burst-firing in reticular thalamic neurons

Burst-firing in thalamic neurons is known to play a key role in mediating thalamocortical (TC) oscillations that are associated with non-REM sleep and some types of epileptic seizure. Within the TC system the primary output of GABAergic neurons in the reticular thalamic nucleus (RTN) is thought to induce the de-inactivation of T-type calcium channels in thalamic relay (TR) neurons, promoting burst-firing drive to the cortex and the propagation of TC network activity. However, RTN neurons also project back onto other neurons within the RTN. The role of this putative negative feedback upon the RTN itself is less well understood, although is hypothesized to induce de-synchronization of RTN neuron firing leading to the suppression of TC oscillations. Here we tested two hypotheses concerning possible mechanisms underlying TC oscillation modulation. Firstly, we assessed the burst-firing behavior of RTN neurons in response to GABA_B receptor activation using acute brain slices. The selective GABA_B receptor agonist baclofen was found to induce suppression of burst-firing concurrent with effects on membrane input resistance. Secondly, RTN neurons express Ca_V3.2 and Ca_V3.3 T-type calcium channel isoforms known to contribute toward TC burst-firing and we examined the modulation of these channels by GABA_B receptor activation. Utilizing exogenously expressed T-type channels we assessed whether GABA_B receptor activation could directly alter T-type calcium channel properties. Overall, GABA_B receptor activation had only modest effects on Ca_V3.2 and Ca_V3.3 isoforms. The only effect that could be predicted to suppress burst-firing was a hyperpolarized shift in the voltage-dependence of inactivation, potentially causing lower channel availability at membrane potentials critical for burst-firing. Conversely, other effects observed such as a hyperpolarized shift in the voltage-dependence of activation of both Ca_V3.2 and Ca_V3.3 as well as increased time constant of activation of the Ca_V3.3 isoform would be expected to enhance burst-firing. Together, we hypothesize that GABA_B receptor activation mediates multiple downstream effectors that combined act to suppress burst-firing within the RTN. It appears unlikely that direct GABA_B receptor-mediated modulation of T-type calcium channels is the major mechanistic contributor to this suppression.

Antecedent Hypoglycemia Does Not Attenuate the Acceleration of Gastric Emptying by Hypoglycemia

Context

Acute hypoglycemia accelerates gastric emptying and increases cardiac contractility. However, antecedent hypoglycemia attenuates counterregulatory hormonal responses to subsequent hypoglycemia.

Objective

To determine the effect of antecedent hypoglycemia on gastric and cardiac responses to subsequent hypoglycemia in health.

Design

A prospective, single-blind, randomized, crossover study (performed at the Royal Adelaide Hospital, Adelaide, South Australia, Australia).

Patients

Ten healthy young men 18 to 35 years of age were studied for 36 hours on two occasions.

Interventions

Participants were randomly assigned to either antecedent hypoglycemia [three 45-minute periods of strict hypoglycemia (2.8 mmol/L] or control [three 45-minute periods of strict euglycemia (6 mmol/L)] during the initial 12-hour period. Participants were monitored overnight, and the following morning blood glucose was clamped at 2.8 mmol/L for 60 minutes and then at 6 mmol/L for 120 minutes. At least 6 weeks later participants returned for the alternative intervention. Gastric emptying and cardiac fractional shortening were measured with scintigraphy and two-dimensional echocardiography, respectively, on the morning of all 4 study days.

Results

A single, acute episode of hypoglycemia accelerated gastric emptying (P = 0.01) and augmented fractional shortening (P < 0.01). Gastric emptying was unaffected by antecedent hypoglycemia (P = 0.74) whereas fractional shortening showed a trend to attenuation (P = 0.06). The adrenaline response was diminished (P < 0.05) by antecedent hypoglycemia.

Conclusions

In health, the acceleration of gastric emptying during hypoglycemia is unaffected by antecedent hypoglycemia, whereas the increase in cardiac contractility may be attenuated.

Comparative effects of intraduodenal fat and glucose on the gut-incretin axis in healthy males

BACKGROUND

The interaction of nutrients with the small intestine stimulates the secretion of numerous enteroendocrine hormones that regulate postprandial metabolism. However, differences in gastrointestinal hormonal responses between the macronutrients are incompletely understood. In the present study, we compared blood glucose and plasma hormone concentrations in response to standardised intraduodenal (ID) fat and glucose infusions in healthy humans.

METHODS

In a parallel study design, 16 healthy males who received an intraduodenal fat infusion were compared with 12 healthy males who received intraduodenal glucose, both at a rate of 2kcal/min over 120min. Venous blood was sampled at frequent intervals for measurements of blood glucose, and plasma total and active glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), insulin and glucagon.

RESULTS

Plasma concentrations of the incretin hormones (both total and active GLP-1 and GIP) and glucagon were higher, and plasma insulin and blood glucose concentrations lower, during intraduodenal fat, when compared with intraduodenal glucose, infusion (treatment by time interaction: P<0.001 for each).

CONCLUSIONS

Compared with glucose, intraduodenal fat elicits substantially greater GLP-1, GIP and glucagon secretion, with minimal effects on blood glucose or plasma insulin in healthy humans. These observations are consistent with the concept that fat is a more potent stimulus of the 'gut-incretin' axis than carbohydrate.

Effects of randomized whey-protein loads on energy intake, appetite, gastric emptying, and plasma gut-hormone concentrations in older men and women

Background: Protein- and energy-rich supplements are used widely for the management of malnutrition in the elderly. Information about the effects of protein on energy intake and related gastrointestinal mechanisms and whether these differ between men and women is limited.Objective: We determined the effects of whey protein on energy intake, appetite, gastric emptying, and gut hormones in healthy older men and women.Design: Eight older women and 8 older men [mean ± SEM age: 72 ± 1 y; body mass index (in kg/m²): 25 ± 1] were studied on 3 occasions in which they received protein loads of 30 g (120 kcal) or 70 g (280 kcal) or a flavored water control drink (0 kcal). At regular intervals over 180 min, appetite (visual analog scales), gastric emptying (3-dimensional ultrasonography), and blood glucose and plasma gut-hormone concentrations [insulin, glucagon, ghrelin, cholecystokinin, gastric inhibitory polypeptide (GIP), glucagon-like peptide 1 (GLP-1), and peptide tyrosine tyrosine (PYY)] were measured, and ad libitum energy intake was quantified from a buffet meal (180-210 min; energy intake, appetite, and gastric emptying in the men have been published previously).Results: Energy intake at the buffet meal was ∼80% higher in older men than in older women (P < 0.001). Energy intake was not suppressed by protein compared with the control in men or women (P > 0.05). There was no effect of sex on gastric emptying, appetite, gastrointestinal symptoms, glucose, or gut hormones (P > 0.05). There was a protein load-dependent slowing of gastric emptying, an increase in concentrations of insulin, glucagon, cholecystokinin, GIP, GLP-1, and PYY, and an increase in total energy intake (drink plus meal: 12% increase with 30 g and 32% increase with 70 g; P < 0.001). Energy intake at the buffet meal was inversely related to the stomach volume and area under the curve of hormone concentrations (P < 0.05).Conclusion: In older men and women, whey-protein drinks load-dependently slow gastric emptying and alter gut hormone secretion compared with a control but have no suppressive effect on subsequent ad libitum energy intake. This trial was registered at www.anzctr.org.au as ACTRN12612000941864.

Comparative effects of glucose and water drinks on blood pressure and cardiac function in older subjects with and without postprandial hypotension

Postprandial hypotension (PPH) occurs frequently and is thought to reflect an inadequate increase in cardiac output to compensate for the rise in splanchnic blood flow after a meal. Gastric distension by water attenuates the postprandial fall in blood pressure (BP). Cardiac hemodynamics (stroke volume (SV), cardiac output (CO), and global longitudinal strain (GLS)) have hitherto not been measured in PPH We sought to determine the comparative effects of water and glucose drinks on cardiac hemodynamics in healthy older subjects and individuals with PPH Eight healthy older subjects (age 71.0 ± 1.7 years) and eight subjects with PPH (age 75.5 ± 1.0 years) consumed a 300 mL drink of either water or 75 g glucose (including 150 mg ¹³C-acetate) in randomized order. BP and heart rate (HR) were measured using an automatic device, SV, CO, and GLS by transthoracic echocardiography and gastric emptying by measurement of ¹³CO₂ In both groups, glucose decreased systolic BP (P < 0.001) and increased HR, SV, and CO (P < 0.05 for all). The fall in systolic BP was greater (P < 0.05), and increase in HR less (P < 0.05), in the PPH group, with no difference in SV or CO Water increased systolic BP (P < 0.05) in subjects with PPH and, in both groups, decreased HR (P < 0.05) without affecting SV, CO, or GLS In subjects with PPH, the hypotensive response to glucose and the pressor response to water were related (R = -0.75, P < 0.05). These observations indicate that, in PPH, the hypotensive response to oral glucose is associated with inadequate compensatory increases in CO and HR, whereas the pressor response to water ingestion is maintained and, possibly, exaggerated.

Effects of Vildagliptin and Metformin on Blood Pressure and Heart Rate Responses to Small Intestinal Glucose in Type 2 Diabetes

OBJECTIVE

To evaluate effects of vildagliptin and metformin on blood pressure (BP) and heart rate (HR) responses to intraduodenal (ID) glucose in diet-controlled type 2 diabetes.

RESEARCH DESIGN AND METHODS

Study A compared vildagliptin (50 mg) and placebo, given 60 min before a 120-min ID glucose infusion at 2 or 4 kcal/min (ID2 or ID4) in 16 patients. Study B compared metformin (850 mg) and placebo, given 30 min before ID2 over 120 min in 9 patients.

RESULTS

Systolic (P = 0.002) and diastolic (P < 0.001) BP were lower and HR greater (P = 0.005) after vildagliptin compared with placebo, without interaction between vildagliptin and the glucose infusion rate. In contrast, HR was greater after metformin than placebo (P < 0.001), without any difference in systolic or diastolic BP.

CONCLUSIONS

Vildagliptin reduces BP and increases HR, whereas metformin increases HR without affecting BP during ID glucose infusion in type 2 diabetes. These distinct cardiovascular profiles during enteral nutrient exposure may have implications for postprandial hypotension.

Nutrient stimulation of mesenteric blood flow - implications for older critically ill patients

Nutrient ingestion induces a substantial increase in mesenteric blood flow. In older persons (aged ≥ 65 years), particularly those with chronic medical conditions, the cardiovascular compensatory response may be inadequate to maintain systemic blood pressure during mesenteric blood pooling, leading to postprandial hypotension. In older ambulatory persons, postprandial hypotension is an important pathophysiological condition associated with an increased propensity for syncope, falls, coronary vascular events, stroke and death. In older critically ill patients, the administration of enteral nutrition acutely increases mesenteric blood flow, but whether this pathophysiological response is protective, or precipitates mesenteric ischaemia, is unknown. There are an increasing number of older patients surviving admission to intensive care units, who are likely to be at increased risk of postprandial hypotension, both during, and after, their stay in hospital. In this review, we describe the prevalence, impact and mechanisms of postprandial hypotension in older people and provide an overview of the impact of postprandial hypotension on feeding prescriptions in older critically ill patients. Finally, we provide evidence that postprandial hypotension is likely to be an unrecognised problem in older survivors of critical illness and discuss potential options for management.

Relationships of the early insulin secretory response and oral disposition index with gastric emptying in subjects with normal glucose tolerance

The oral disposition index, the product of the early insulin secretory response during an oral glucose tolerance test and insulin sensitivity, is used widely for both the prediction of, and evaluation of the response to interventions, in type 2 diabetes. Gastric emptying, which determines small intestinal exposure of nutrients, modulates postprandial glycemia. The aim of this study was to determine whether the insulin secretory response and the disposition index (DI) related to gastric emptying in subjects with normal glucose tolerance. Thirty-nine subjects consumed a 350 mL drink containing 75 g glucose labeled with ^99mTc-sulfur colloid. Gastric emptying (by scintigraphy), blood glucose (G) and plasma insulin (I) were measured between t = 0-120 min. The rate of gastric emptying was derived from the time taken for 50% emptying (T₅₀) and expressed as kcal/min. The early insulin secretory response was estimated by the ratio of the change in insulin (∆I_0-30) to that of glucose at 30 min (∆G_0-30) represented as ∆I_0-30/∆G_0-30 Insulin sensitivity was estimated as 1/fasting insulin and the DI was then calculated as ∆I_0-30/∆G_0-30 × 1/fasting insulin. There was a direct relationship between ∆G_0-30 and gastric emptying (r = 0.47, P = 0.003). While there was no association of either ∆I_0-30 (r = -0.16, P = 0.34) or fasting insulin (r = 0.21, P = 0.20), there were inverse relationships between the early insulin secretory response (r = -0.45, P = 0.004) and the DI (r = -0.33, P = 0.041), with gastric emptying. We conclude that gastric emptying is associated with both insulin secretion and the disposition index in subjects with normal glucose tolerance, such that when gastric emptying is relatively more rapid, both the early insulin secretory response and the disposition index are less. These findings should be interpreted as "hypothesis generating" and provide the rationale for longitudinal studies to examine the impact of baseline rate of gastric emptying on the prospective risk of type 2 diabetes.

Effects of small intestinal glucose on glycaemia, insulinaemia and incretin hormone release are load-dependent in obese subjects

BACKGROUND/OBJECTIVES

Studies concerning the glycaemic response to oral glucose, or meals in obesity have usually failed to account for gastric emptying. It has been suggested that the incretin effect may be diminished in obesity as a result of a reduction in glucagon-like peptide-1 (GLP-1) secretion. We sought to determine the effect of two different rates of intraduodenal glucose infusions on glycaemic, insulinaemic and incretin hormone responses in lean and obese subjects and compare the effects of oral and intraduodenal glucose in obese subjects.

SUBJECTS/METHODS

Eleven obese subjects (age 37.5±4.1 years, body mass index (BMI) 35.7±1.4 kg m^-2) and 12 controls (age 34.7±4.0 years, BMI 23.9±0.7 kg m^-2) received intraduodenal infusions of glucose at 1 or 3 kcal min^-1, or saline for 60 min (t=0-60 min), followed by intraduodenal saline (t=60-120 min). In obese subjects, an oral glucose tolerance test was performed. Blood glucose, serum insulin, plasma total GLP-1 and total gastric inhibitory polypeptide (GIP) were measured.

RESULTS

In both the groups (P<0.001), the incremental areas under the curve (iAUC)_0-60 min for glucose was greater with the 3 kcal min^-1 than the 1 kcal min^-1 infusion; the iAUC_0-120 min for glucose during 3 kcal min^-1 was greater (P<0.05), in the obese. Insulin responses to 1 kcal min^-1 and, particularly, 3 kcal min^-1 were greater (P<0.001) in the obese. Stimulation of GLP-1 and GIP were greater (P<0.001) in response to 3 kcal min^-1, compared with 1 kcal min^-1 and saline, without any difference between the groups. In the obese, glycaemic, insulinaemic and GIP, but not GLP-1, responses to oral and intraduodenal glucose were related (P<0.05).

CONCLUSIONS

The rate of duodenal glucose delivery is a major determinant of glycaemia, insulinaemia and incretin hormone release in obese subjects. Obesity is not apparently associated with impaired GLP-1 secretion.

Metformin reduces the rate of small intestinal glucose absorption in type 2 diabetes

In rodents, metformin slows intestinal glucose absorption, potentially increasing exposure of the distal gut to glucose to enhance postprandial glucagon-like peptide-1 (GLP-1) secretion. We evaluated the effects of metformin on serum 3-O-methylglucose (3-OMG; a marker of glucose absorption) and plasma total GLP-1 concentrations during a standardized intraduodenal infusion of glucose and 3-OMG in patients with type 2 diabetes. A total of 12 patients, treated with metformin 850 mg twice daily or placebo for 7 days each in a double-blind, randomized, crossover design (14 days' washout between treatments), were evaluated on days 5 or 8 of each treatment (6 subjects each). On each study day, 30 minutes after ingesting 850 mg metformin or placebo, patients received an infusion of glucose (60 g + 5 g 3-OMG, dissolved in water to 240 mL) via an intraduodenal catheter over the course of 120 minutes. Compared with placebo, metformin was associated with lower serum 3-OMG ( P < .001) and higher plasma total GLP-1 ( P = .003) concentrations. The increment in plasma GLP-1 after metformin vs placebo was related to the reduction in serum 3-OMG concentrations ( P = .019). Accordingly, metformin inhibits small intestinal glucose absorption, which may contribute to augmented GLP-1 secretion in type 2 diabetes.

Acute effects of the glucagon-like peptide-1 receptor agonist, exenatide, on blood pressure and heart rate responses to intraduodenal glucose infusion in type 2 diabetes

AIM

To evaluate the effects of the glucagon-like peptide-1 receptor agonist, exenatide, on blood pressure and heart rate during an intraduodenal glucose infusion in type 2 diabetes.

METHODS

Nine subjects with type 2 diabetes were randomised to receive intravenous exenatide or saline control in a crossover design. Glucose (3 kcal min^-1) was infused via an intraduodenal manometry catheter for 60 min. Blood pressure, heart rate, and the frequency and amplitude of duodenal pressure waves were measured at regular intervals. Gastrointestinal symptoms were monitored using 100 mm visual analogue scales.

RESULTS

During intraduodenal glucose infusion (0-60 min), diastolic (p_(0-60) = 0.03) and mean arterial (p_(0-60) = 0.03) blood pressures and heart rate (p_(0-60) = 0.06; p_(0-120) = 0.03)) were higher with exenatide compared to placebo. The increase in the area under the curve for diastolic blood pressure and mean arterial blood pressure was related directly to the suppression of the duodenal motility index with exenatide compared to control (p = 0.007 and 0.04, respectively).

CONCLUSION

In type 2 diabetes, intravenous exenatide increases mean arterial blood pressure and heart rate during an intraduodenal glucose infusion, supporting the need for further research with exenatide for its potential use in postprandial hypotension.

Small Intestinal Glucose Delivery Affects the Lowering of Blood Glucose by Acute Vildagliptin in Type 2 Diabetes

CONTEXT

The rate of gastric emptying is an important determinant of glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) secretion and may influence the magnitude of glucose lowering by dipeptidyl peptidase-4 (DPP-4) inhibitors.

OBJECTIVE

To evaluate the effects of the DPP-4 inhibitor, vildagliptin (VILD), during intraduodenal (ID) glucose infusion at 2 different rates within the physiological range of gastric emptying, in type 2 diabetes.

PARTICIPANTS AND DESIGN

A total of 16 diet-controlled type 2 diabetic patients were studied on 4 separate days in double-blind, randomized, fashion. On each day, either 5-mg VILD or placebo (PLBO) was given 60 minutes before a 120-minute ID glucose infusion at 2 or 4 kcal/min (ID2 or ID4). Plasma glucose and hormones were measured frequently.

RESULTS

Plasma glucose, insulin, C-peptide, glucagon, total GIP, and total and intact GLP-1 concentrations were higher during ID4 than ID2 (P < .01 for each). Compared with PLBO, VILD was associated with higher intact GLP-1, insulin, and C-peptide and lower glucose and total GIP and GLP-1 (P < .01 for each), without affecting glucagon. There were significant interactions between the rate of ID glucose and VILD treatment on plasma glucose, intact and total GLP-1, and GIP (P < .05 for each) but not insulin, C-peptide, or glucagon. The reduction in glucose and the increment in intact GLP-1 after VILD vs PLBO were 3.3- and 3.8-fold greater, respectively, during ID4 compared with ID2.

CONCLUSIONS/INTERPRETATION

These observations warrant further study to clarify whether type 2 diabetic patients with relatively more rapid gastric emptying have greater glucose lowering during treatment with DPP-4 inhibitors.

Regional specificity of the gut-incretin response to small intestinal glucose infusion in healthy older subjects

The importance of the region, as opposed to the length, of small intestine exposed to glucose in determining the secretion of the incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) remains unclear. We sought to compare the glycemic, insulinemic and incretin responses to glucose administered to the proximal (12-60cm beyond the pylorus), or more distal (>70cm beyond the pylorus) small intestine, or both. 10 healthy subjects (9M,1F; aged 70.3±1.4years) underwent infusion of glucose via a catheter into the proximal (glucose proximally; GP), or distal (glucose distally; GD) small intestine, or both (GPD), on three separate days in a randomised fashion. Blood glucose, serum insulin and plasma GLP-1, GIP and CCK responses were assessed. The iAUC for blood glucose was greater in response to GPD than GP (P<0.05), with no difference between GD and GP. GP was associated with minimal GLP-1 response (P=0.05), but substantial increases in GIP, CCK and insulin (P<0.001 for all). GPD and GD both stimulated GLP-1, GIP, CCK and insulin (P<0.001 for all). Compared to GP, GPD induced greater GLP-1, GIP and CCK responses (P<0.05 for all). Compared with GPD, GD was associated with greater GLP-1 (P<0.05), but reduced GIP and CCK (P<0.05 for both), responses. We conclude that exposure of glucose to the distal small intestine appears necessary for substantial GLP-1 secretion, while exposure of both the proximal and distal small intestine result in substantial secretion of GIP.

Critical Illness Is Associated With Impaired Gallbladder Emptying as Assessed by 3D Ultrasound

OBJECTIVE

To quantify gallbladder dysfunction during critical illness.

DESIGN

Prospective observational comparison study of nutrient-stimulated gallbladder emptying in health and critical illness.

SETTING

Single-centre mixed medical/surgical ICU.

PATIENTS

Twenty-four mechanically ventilated critically ill patients suitable to receive enteral nutrition were compared with 12 healthy subjects.

INTERVENTIONS

Participants were studied after an 8-hour fast. Between 0 and 120 minutes, high-fat nutrient (20% intralipid) was infused via a postpyloric catheter into the duodenum at 2 kcal/min.

MEASUREMENTS AND MAIN RESULTS

Three-dimensional images of the gallbladder were acquired at 30-minute intervals from -30 to 180 minutes. Ejection fraction (%) was calculated as changes between 0 and 120 minutes. Blood samples were obtained at 30-minute intervals for plasma cholecystokinin. Data are mean (SD) or median [interquartile range]. In the critically ill, fasting gallbladder volumes (critically ill, 61 mL [36-100 mL] vs healthy, 22 mL [15-25] mL; p < 0.001] and wall thickness (0.45 mm [0.15 mm] vs 0.26 mm [0.08 mm]; p < 0.001] were substantially greater, and sludge was evident in the majority of patients (71% vs 0%). Nutrient-stimulated emptying was incomplete in the critically ill after 120 minutes but was essentially complete in the healthy individuals (22 mL [9-66 mL] vs 4 mL [3-5 mL]; p < 0.01]. In five critically ill patients (21%), there was no change in gallbladder volume in response to nutrient, and overall ejection fraction was reduced in the critically ill (50% [8-83%] vs 77 [72-84%]; p = 0.01]. There were no differences in fasting or incremental cholecystokinin concentrations.

CONCLUSIONS

Fasted critically ill patients have larger, thicker-walled gallbladders than healthy subjects and nutrient-stimulated gallbladder emptying is impaired with "gallbladder paresis" occurring in approximately 20%.

Liberal Glycemic Control in Critically Ill Patients With Type 2 Diabetes: An Exploratory Study

OBJECTIVES

The optimal blood glucose target in critically ill patients with preexisting diabetes and chronic hyperglycemia is unknown. In such patients, we aimed to determine whether a " liberal" approach to glycemic control would reduce hypoglycemia and glycemic variability and appear safe.

DESIGN

Prospective, open-label, sequential-period exploratory study.

SETTING

Medical-surgical ICU.

PATIENTS

During sequential 6-month periods, we studied 83 patients with preexisting type 2 diabetes and chronic hyperglycemia (glycated hemoglobin, ≥ 7.0% at ICU admission).

INTERVENTION

During the "standard care" period, 52 patients received insulin to treat blood glucose concentrations greater than 10 mmol/L whereas during the "liberal" period, 31 patients received insulin to treat blood glucose concentrations greater than 14 mmol/L.

MEASUREMENTS AND MAIN RESULTS

Time-weighted mean glucose concentrations and the number and duration of moderate (< 4.0 mmol/L) and severe (≤ 2.2 mmol/L) hypoglycemic episodes were recorded, with moderate and severe hypoglycemic episodes grouped together. Glycemic variability was assessed by calculating the coefficient of variability for each patient. Safety was evaluated using clinical outcomes and plasma concentrations of markers of inflammation, glucose-turnover, and oxidative stress. Mean glucose (TWglucoseday 0-7, standard care: 9.3 [1.8] vs liberal: 10.3 [2.1] mmol/L; p = 0.02) and nadir blood glucose (4.4 [1.5] vs 5.5 [1.6] mmol/L; p < 0.01) were increased during the liberal period. There was a signal toward reduced risk of moderate-severe hypoglycemia (relative risk: liberal compared with standard care: 0.47 [95% CI, 0.19-1.13]; p = 0.09). Ten patients (19%) during the standard period and one patient (3%) during the liberal period had recurrent episodes of moderate-severe hypoglycemia. Liberal therapy reduced glycemic variability (coefficient of variability, 33.2% [12.9%] vs 23.8% [7.7%]; p < 0.01). Biomarker data and clinical outcomes were similar.

CONCLUSIONS

In critically ill patients with type 2 diabetes and chronic hyperglycaemia, liberal glycemic control appears to attenuate glycemic variability and may reduce the prevalence of moderate-severe hypoglycemia.

Energy-Dense Formulae May Slow Gastric Emptying in the Critically Ill

BACKGROUND

Enteral feed intolerance occurs frequently in critically ill patients and can be associated with adverse outcomes. "Energy-dense formulae" (ie, >1 kcal/mL) are often prescribed to critically ill patients to reduce administered volume and are presumed to maintain or increase calorie delivery. The aim of this study was to compare gastric emptying of standard and energy-dense formulae in critically ill patients.

METHODS

In a retrospective comparison of 2 studies, data were analyzed from 2 groups of patients that received a radiolabeled 100-mL "meal" containing either standard calories (1 kcal/mL) or concentrated calories (energy-dense formulae; 2 kcal/mL). Gastric emptying was measured using a scintigraphic technique. Radioisotope data were collected for 4 hours and gastric emptying quantified. Data are presented as mean ± SE or median [interquartile range] as appropriate.

RESULTS

Forty patients were studied (n = 18, energy-dense formulae; n = 22, standard). Groups were well matched in terms of demographics. However, patients in the energy-dense formula group were studied earlier in their intensive care unit admission (P = .02) and had a greater proportion requiring inotropes (P = .002). A similar amount of calories emptied out of the stomach per unit time (P = .57), but in patients receiving energy-dense formulae, a greater volume of meal was retained in the stomach (P = .045), consistent with slower gastric emptying.

CONCLUSIONS

In critically ill patients, the administration of the same volume of a concentrated enteral nutrition formula may not result in the delivery of more calories to the small intestine over time because gastric emptying is slowed.

Gastric emptying, postprandial blood pressure, glycaemia and splanchnic flow in Parkinson’s disease

AIM: To determine gastric emptying, blood pressure, mesenteric artery blood flow, and blood glucose responses to oral glucose in Parkinson’s disease.

METHODS: Twenty-one subjects (13 M, 8 F; age 64.2 ± 1.6 years) with mild to moderate Parkinson’s disease (Hoehn and Yahr score 1.4 ± 0.1, duration of known disease 6.3 ± 0.9 years) consumed a 75 g glucose drink, labelled with 20 MBq ^99mTc-calcium phytate. Gastric emptying was quantified with scintigraphy, blood pressure and heart rate with an automated device, superior mesenteric artery blood flow by Doppler ultrasonography and blood glucose by glucometer for 180 min. Autonomic nerve function was evaluated with cardiovascular reflex tests and upper gastrointestinal symptoms by questionnaire.

RESULTS: The mean gastric half-emptying time was 106 ± 9.1 min, gastric emptying was abnormally delayed in 3 subjects (14%). Systolic and diastolic blood pressure fell (P < 0.001) and mesenteric blood flow and blood glucose (P < 0.001 for both) increased, following the drink. Three subjects (14%) had definite autonomic neuropathy and 8 (38%) had postprandial hypotension. There were no significant relationships between changes in blood pressure, heart rate or mesenteric artery blood flow with gastric emptying. Gastric emptying was related to the score for autonomic nerve function (R = 0.55, P < 0.01). There was an inverse relationship between the blood glucose at t = 30 min (R = -0.52, P < 0.05), while the blood glucose at t = 180 min was related directly (R = 0.49, P < 0.05), with gastric emptying.

CONCLUSION: In mild to moderate Parkinson’s disease, gastric emptying is related to autonomic dysfunction and a determinant of the glycaemic response to oral glucose.

Effects of intraduodenal hydroxycitrate on glucose absorption, incretin release, and glycemia in response to intraduodenal glucose infusion in health and type 2 diabetes: A randomised controlled trial

OBJECTIVE

Hydroxycitric acid (HCA), derived from the fruit Garcinia cambogia, reduces the rate of glucose absorption and lowers postprandial glycemia in rodents, but its effect in humans is unknown. The aim of this study was to investigate the effects of small intestinal perfusion with HCA on glucose absorption, as well as the incretin and glycemic responses to a subsequent intraduodenal glucose infusion, in both healthy individuals and patients with type 2 diabetes.

METHODS

Twelve healthy participants and 8 patients with type 2 diabetes received an intraduodenal infusion of HCA (2800 mg in water) or control (water) over 60 min, followed by an intraduodenal infusion of 60 g glucose over 120 min, in a double-blind, randomized crossover design. In healthy individuals, 5 g 3-O-methylglucose (3-OMG) was co-infused with glucose as a marker of glucose absorption. Blood was sampled frequently.

RESULTS

In healthy individuals, blood glucose was lower with HCA than control, both before and during the intraduodenal glucose infusion (P < 0.05 for each). Plasma glucose-dependent insulinotropic polypeptide (GIP; P = 0.01) and glucagon (P = 0.06) were higher with HCA, but there were no differences in plasma glucagon-like peptide (GLP)-1, insulin, or serum 3-OMG concentrations. In patients with type 2 diabetes, blood glucose, and plasma GIP, GLP-1, and insulin did not differ between HCA and control either before or after intraduodenal glucose, but during glucose infusion, plasma glucagon was higher with HCA (P = 0.04).

CONCLUSION

In healthy individuals, small intestinal exposure to HCA resulted in a modest reduction in glycemia and stimulation of plasma GIP and glucagon, but no effect on plasma GLP-1 or insulin, or on glucose absorption. HCA had no effect on glycemia in patients with type 2 diabetes.

A Protein Preload Enhances the Glucose-Lowering Efficacy of Vildagliptin in Type 2 Diabetes

OBJECTIVE

Nutrient "preloads" given before meals can attenuate postprandial glycemic excursions, at least partly by slowing gastric emptying and stimulating secretion of the incretins (i.e., glucagon-like peptide-1 [GLP-1] and glucose-dependent insulinotropic polypeptide [GIP]). This study was designed to evaluate whether a protein preload could improve the efficacy of the dipeptidyl peptidase-4 (DPP-4) inhibitor vildagliptin to increase incretin concentrations, slow gastric emptying, and lower postprandial glycemia in type 2 diabetes.

RESEARCH DESIGN AND METHODS

Twenty-two patients with type 2 diabetes treated with metformin were studied on four occasions, receiving either 50 mg vildagliptin (VILD) or placebo (PLBO) on both the evening before and the morning of each study day. The latter dose was followed after 60 min by a preload drink containing either 25 g whey protein (WHEY) or control flavoring (CTRL), and after another 30 min by a (13)C-octanoate-labeled mashed potato meal. Plasma glucose and hormones, and gastric emptying, were evaluated.

RESULTS

Compared with PLBO/CTRL, PLBO/WHEY reduced postprandial peak glycemia, increased plasma insulin, glucagon, and incretin hormones (total and intact), and slowed gastric emptying, whereas VILD/CTRL reduced both the peak and area under the curve for glucose, increased plasma intact incretins, and slowed gastric emptying but suppressed plasma glucagon and total incretins (P < 0.05 each). Compared with both PLBO/WHEY and VILD/CTRL, VILD/WHEY was associated with higher plasma intact GLP-1 and GIP, slower gastric emptying, and lower postprandial glycemia (P < 0.05 each).

CONCLUSIONS

In metformin-treated type 2 diabetes, a protein preload has the capacity to enhance the efficacy of vildagliptin to slow gastric emptying, increase plasma intact incretins, and reduce postprandial glycemia.

Effect of duodenal glucose load on blood pressure in type 2 diabetes

Postprandial hypotension occurs frequently in diabetes. We show in 9 type 2 patients, that the fall in systolic blood pressure is greater in response to intraduodenal glucose infused at 4 kcal/min than 2 kcal/min, implying that strategies to slow gastric emptying may be effective in the management of postprandial hypotension.

The ageing gastrointestinal tract

PURPOSE OF REVIEW

This article reviews the impact of ageing on the gastrointestinal tract, including effects on the absorption of nutrients and drugs and the gastrointestinal tract defence system against ingested pathogens.

RECENT FINDINGS

Recent publications support earlier observations of an age-related selective decline in gut function including changes in taste, oesophageal sphincter motility, gastric emptying, and neurons of the myenteric plexus related to gut transit which may impact the nutritional status. Ageing is also associated with structural and functional mucosal defence defects, diminished abilities to generate protective immunity, and increased incidence of inflammation and oxidative stress. A number of gastrointestinal disorders occur more frequently in the elderly population.

SUMMARY

Alterations in gut function with ageing have particular implications for oesophageal, gastric, and colonic motility. Older individuals are particularly susceptible to malnutrition, postprandial hypotension, dysphagia, constipation, and faecal incontinence. Decrease in the number of nerve cells of the myenteric plexus that impact digestive absorption and the surface area of the small intestine because of degeneration of villi may lead to blunted absorption of nutrients. Impairment of the intestinal immune system as a result of ageing, including the mucosal layer of the gastrointestinal tract, appears to be a significant contributor to the age-related increase in the incidence and severity of infections.

Administration of resveratrol for 5 wk has no effect on glucagon-like peptide 1 secretion, gastric emptying, or glycemic control in type 2 diabetes: a randomized controlled trial

BACKGROUND

Resveratrol has been reported to lower glycemia in rodent models of type 2 diabetes associated with the stimulation of glucagon-like peptide 1 (GLP-1), which is known to slow gastric emptying, stimulate insulin secretion, and suppress glucagon secretion and energy intake.

OBJECTIVE

We evaluated the effects of 5 wk of resveratrol treatment on GLP-1 secretion, gastric emptying, and glycemic control in type 2 diabetes.

DESIGN

Fourteen patients with diet-controlled type-2 diabetes [mean ± SEM glycated hemoglobin (HbA1c): 6.4 ± 0.2% (46.4 ± 2.2 mmol/mol)] received resveratrol (500 mg twice daily) or a placebo over two 5-wk intervention periods with a 5-wk washout period in between in a double-blind, randomized, crossover design. Before and after each intervention period (4 visits), body weight and HbA1c were measured, and patients were evaluated after an overnight fast with a standardized mashed-potato meal labeled with 100 μg (13)C-octanoic acid to measure blood glucose and plasma GLP-1 concentrations and gastric emptying (breath test) over 240 min. Daily energy intake was estimated from 3-d food diaries during the week before each visit.

RESULTS

Fasting and postprandial blood glucose and plasma total GLP-1 as well as gastric emptying were similar at each assessment, and the change in each variable from weeks 0 to 5 did not differ between resveratrol and placebo groups. Similarly, changes in HbA1c, daily energy intake, and body weight after 5 wk did not differ between the 2 treatments.

CONCLUSIONS

In patients with diet-controlled type 2 diabetes, 5 wk of twice-daily 500 mg-resveratrol supplementation had no effect on GLP-1 secretion, glycemic control, gastric emptying, body weight, or energy intake. Our observations do not support the use of resveratrol for improving glycemic control. This trial was registered at www.anzctr.org.au as ACTRN12613000717752.

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

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

Novel insights into the effects of diabetes on gastric motility

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

Acute load-dependent effects of oral whey protein on gastric emptying, gut hormone release, glycemia, appetite, and energy intake in healthy men

BACKGROUND

In healthy individuals, intraduodenal whey protein load-dependently modulates gastrointestinal motor and hormonal functions and suppresses energy intake. The effect of oral whey, particularly the impact of load, has not been evaluated.

OBJECTIVE

The purpose of this study was to quantify gastric emptying of 30 and 70 g of oral whey protein loads and their relation to gastrointestinal hormone, glycemic, and appetitive responses.

DESIGN

On 3 separate occasions in a randomized, double-blind order, 18 lean men [mean ± SEM age: 24.8 ± 1.4 y; body mass index (in kg/m(2)): 21.6 ± 0.5] received iso-osmolar, equally palatable drinks (∼450 mL) containing 30 g pure whey protein isolate (L), 70 g pure whey protein isolate (H), or saline (control). Gastric emptying (with the use of 3-dimensional ultrasound), plasma cholecystokinin, glucagon-like peptide 1, glucose-dependent insulinotropic peptide, insulin, glucagon, total amino acids, and blood glucose were measured for 180 min after consumption of the drinks, and energy intake at a buffet-style lunch was quantified.

RESULTS

Gastric emptying of the L and H drinks was comparable when expressed in kilocalories per minute (L: 2.6 ± 0.2 kcal/min; H: 2.9 ± 0.3 kcal/min) and related between individuals (r = 0.54, P < 0.01). Gastrointestinal hormone, insulin, and glucagon responses to the L and H drinks were comparable until ∼45-60 min after ingestion, after which time the responses became more differentiated. Blood glucose was modestly reduced after the H drink between t = 45 and 150 min when compared with the L drink (all P < 0.05). Energy intake was suppressed by both L and H drinks compared with control (P < 0.05) (control: 1174 ± 91 kcal; L: 1027 ± 81 kcal; and H: 997 ± 71 kcal).

CONCLUSION

These findings indicate that, in healthy lean men, the rate of gastric emptying of whey protein is independent of load and determines the initial gastrointestinal hormone response. This study was registered at www.anzctr.org.au as 12611000706976.

The impact of micronutrient supplementation in alcohol-exposed pregnancies on information processing skills in Ukrainian infants

The potential of micronutrients to ameliorate the impact of prenatal alcohol exposure (PAE) was explored in a clinical trial conducted in Ukraine. Cardiac orienting responses (ORs) during a habituation/dishabituation learning paradigm were obtained from 6 to 12 month-olds to assess neurophysiological encoding and memory. Women who differed in prenatal alcohol use were recruited during pregnancy and assigned to a group (No study-provided supplements, multivitamin/mineral supplement, or multivitamin/mineral supplement plus choline supplement). Heart rate was collected for 30 s prior to stimulus onset and 12 s post-stimulus onset. Difference values (∆HR) for the first 3 trials of each condition were aggregated for analysis. Gestational blood samples were collected to assess maternal nutritional status and changes as a function of the intervention. Choline supplementation resulted in a greater ∆HR on the visual habituation trials for all infants and for the infants with no PAE on the dishabituation trials. The latency of the response was reduced in both conditions for all infants whose mothers received choline supplementation. Change in gestational choline level was positively related to ∆HR during habituation trials and levels of one choline metabolite, dimethylglycine (DMG), predicted ∆HR during habituation trials and latency of responses. A trend was found between DMG and ∆HR on the dishabituation trials and latency of the response. Supplementation did not affect ORs to auditory stimuli. Choline supplementation when administered together with routinely recommended multivitamin/mineral prenatal supplements during pregnancy may provide a beneficial impact to basic learning mechanisms involved in encoding and memory of environmental events in alcohol-exposed pregnancies as well as non- or low alcohol-exposed pregnancies. Changes in maternal nutrient status suggested that one mechanism by which choline supplementation may positively impact brain development is through prevention of fetal alcohol-related depletion of DMG, a metabolic nutrient that can protect against overproduction of glycine, during critical periods of neurogenesis.

The duodenal glucose load impacts the oral disposition index in healthy subjects

AIM

In healthy subjects, the oral disposition index (ratio of insulin response to insulin sensitivity) is predictive of the development of Type 2 diabetes. Gastric emptying, which exhibits a substantial interindividual variation, is a major determinant of postprandial glycaemia in health and diabetes. We sought to determine whether the rate of intraduodenal glucose delivery affects the disposition index in people without diabetes.

METHODS

Nineteen Caucasian males received glucose infusions via an intraduodenal catheter at either 2 kcal/min (ID2) or 4 kcal/min (ID4) for 120 min, on two separate days with measurements of blood glucose (G) and plasma insulin (I) at frequent intervals. The insulin response was estimated by the ratio of the change in insulin to that of change in glucose at 30 min (∆I(0-30)/∆G(0-30)) and 60 min (∆I(0-60)/∆G(0-60)). Insulin sensitivity was estimated as 1/fasting insulin. The oral disposition index (DI) was calculated as ∆I(0-30)/∆G(0-30) × 1/fasting insulin and ∆I(0-60)/∆G(0-60) × 1/fasting insulin.

RESULTS

The overall glycaemic response was comparable on both days, but the insulin response was much greater at ID4 when calculated at either 30 or 60 min (P < 0.05). DI was also greater (P < 0.05) in response to ID4 than ID2.

CONCLUSIONS

The rate of duodenal glucose delivery has a major impact on insulin release and, thereby, DI. This suggests that the rate of gastric emptying, which determines duodenal glucose delivery, is a determinant of DI.

Z chromosome divergence, polymorphism and relative effective population size in a genus of lekking birds

Sex chromosomes contribute disproportionately to species boundaries as they diverge faster than autosomes and often have reduced diversity. Their hemizygous nature contributes to faster divergence and reduced diversity, as do some types of selection. In birds, other factors (mating system and bottlenecks) can further decrease the effective population size of Z-linked loci and accelerate divergence (Fast-Z). We assessed Z-linked divergence and effective population sizes for two polygynous sage-grouse species and compared them to estimates from birds with various mating systems. We found lower diversity and higher FST for Z-linked loci than for autosomes, as expected. The π(Z)/π(A) ratio was 0.38 in Centrocercus minimus, 0.48 in Centrocercus urophasianus and 0.59 in a diverged, parapatric population of C. urophasianus, a broad range given the mating system among these groups is presumably equivalent. The full data set had unequal males and females across groups, so we compared an equally balanced reduced set of C. minimus and individuals pooled from both C. urophasianus subgroups recovering similar estimates: 0.54 for C. urophasianus and 0.38 for C. minimus. We provide further evidence that N(eZ)/N(eA) in birds is often lower than expected under random mating or monogamy. The lower ratio in C. minimus could be a consequence of stronger selection or drift acting on Z loci during speciation, as this species differs strongly from C. urophasianus in sexually selected characters with minimal mitochondrial divergence. As C. minimus also exhibited lower genomic diversity, it is possible that a more severe demographic history may contribute to its lower ratio.

Lesser suppression of energy intake by orally ingested whey protein in healthy older men compared with young controls

Protein-rich supplements are used widely for the management of malnutrition in young and older people. Protein is the most satiating of the macronutrients in young. It is not known how the effects of oral protein ingestion on energy intake, appetite, and gastric emptying are modified by age. The aim of the study was to determine the suppression of energy intake by protein compared with control and underlying gastric-emptying and appetite responses of oral whey protein drinks in eight healthy older men (69-80 yr) compared with eight young male controls (18-34 yr). Subjects were studied on three occasions to determine the effects of protein loads of 30 g/120 kcal and 70 g/280 kcal compared with a flavored water control-drink (0 g whey protein) on energy intake (ad libitum buffet-style meal), and gastric emptying (three-dimensional-ultrasonography) and appetite (0-180 min) in a randomized, double-blind, cross-over design. Energy intake was suppressed by the protein compared with control (P = 0.034). Suppression of energy intake by protein was less in older men (1 ± 5%) than in young controls (15 ± 2%; P = 0.008). Cumulative energy intake (meal+drink) on the protein drink days compared with the control day increased more in older (18 ± 6%) men than young (1 ± 3%) controls (P = 0.008). Gastric emptying of all three drinks was slower in older men (50% gastric-emptying time: 68 ± 5 min) than young controls (36 ± 5 min; P = 0.007). Appetite decreased in young, while it increased in older (P < 0.05). In summary, despite having slower gastric emptying, elderly men exhibited blunted protein-induced suppression of energy intake by whey protein compared with young controls, so that in the elderly men, protein ingestion increased overall energy intake more than in the young men.

Relationships of Early And Late Glycemic Responses With Gastric Emptying During An Oral Glucose Tolerance Test

CONTEXT

The early glycemic response during a 75-g oral glucose tolerance test (OGTT) is directly related to the rate of gastric emptying (GE). There is little information about the effect of GE on the blood glucose at either 60 min (a predictor of diabetes) or 120 min (used diagnostically).

OBJECTIVE

This study aimed to evaluate the relationships between glycemic responses at 30, 60, and 120 min and GE following a 75-g OGTT in subjects with normal glucose tolerance (NGT), impaired glucose tolerance (IGT), and type 2 diabetes (T2D).

DESIGN, SETTING, AND SUBJECTS

Eighty-two subjects in the general community without diabetes (57 NGT, 25 IGT) and 16 with T2D consumed a 75-g glucose drink labeled with (99m)Tc-sulfur colloid. GE (by scintigraphy) and glycemia were measured from t = 0-120 min and relationships between blood glucose (absolute, change from baseline, and area under the curve) and GE at 30, 60, and 120 min determined.

RESULTS

There were no differences in GE. There were relationships between the blood glucose at 30 min and GE (NGT: r = 0.40; P < .01; IGT: r = 0.49; P = .02; T2D: r = 0.62; P = .01). There was also a relationship between the blood glucose at 60 min and GE in IGT (r = 0.52; P = .02) and T2D (r = 0.77; P < .01), but not NGT (r = 0.16; P = .24). In NGT, there was an inverse relationship between blood glucose at 120 min and GE (r = -0.30; P = .02), but not in IGT (r = 0.05; P = .82) or T2D (r = 0.37; P = .16).

CONCLUSIONS

GE is a determinant of the glycemic response to an OGTT in NGT, IGT, and T2D but these relationships differ and are time dependent.