Effects of variations in duodenal glucose load on blood pressure, heart rate, superior mesenteric artery blood flow and plasma noradrenaline in healthy young and older subjects

PPH (postprandial hypotension), leading to increased morbidity and mortality, is an important clinical problem, particularly in the elderly and individuals with autonomic dysfunction. The magnitude of the postprandial fall in BP (blood pressure) appears to be dependent on the rate of nutrient entry into the small intestine and may be related to changes in splanchnic blood flow and sympathetic nerve activity. We aimed at determining the comparative effects of different ID (intraduodenal) glucose loads on BP, HR (heart rate), SMA (superior mesenteric artery) flow and vascular conductance and plasma NA (noradrenaline) in 'young' and 'older' subjects. A total of 12 'young' (six male and six female; age, 22.2±2.3 years) and 12 'older' (six male and six female; age, 68.7±1.0 years) subjects, the latter who have been studied previously [Vanis, Gentilcore, Rayner, Wishart, Horowitz, Feinle-Bisset and Jones (2011) Am. J. Physiol. Regul. Integr. Comp. Physiol., 300, R1524-R1531], had measurements of BP, HR, SMA flow and plasma NA before, and during, ID infusions of glucose at 1, 2 or 3 kcal/min ('G1', 'G2' and 'G3') (where 1 kcal≈4.184 J), or 'S' (saline) for 60 min. In 'young' subjects, there was no change in BP during any of the four infusions. In contrast, in 'older' subjects, SBP (systolic BP) fell during 'G2', and 'G3' (P<0.005 for both), but not during 'S' or 'G1'. In 'young' and 'older' subjects HR increased during 'G2' (P<0.05) and 'G3' (P<0.001), a response that was greater (P<0.05) in the young, but not during 'S' or 'G1'. The rise in SMA flow and vascular conductance in response to ID glucose were load-dependent in both 'young' and 'older' subjects (P<0.001 for all), with no difference between them. Plasma NA rose in response to 'G2' and 'G3' (P<0.05) in the young, but in 'G3' (P<0.05) only in the 'older' subjects, with no difference between them. Hence, in response to small intestinal glucose infusions at 1, 2 and 3 kcal/min, 'older', but not 'young', subjects exhibit a comparable fall in BP in response to the two higher glucose loads, which may reflect an inadequate, compensatory, rise in HR, in the 'older' subjects, but not a greater increase in SMA conductance.

Comparative effects of variations in duodenal glucose load on glycemic, insulinemic, and incretin responses in healthy young and older subjects

CONTEXT

Aging is associated with deteriorating glucose tolerance. Studies assessing glucose tolerance and subsequent insulin and incretin hormone release often fail to take into account the rate of gastric emptying when evaluating these responses.

OBJECTIVE

Our objective was to determine the comparative effects of variations in the small intestinal glucose load on the glycemic, insulinemic, and incretin responses in healthy young and older subjects.

MATERIALS AND METHODS

Twelve healthy young (six males, six females; age 22.2±2.3 yr) and 12 older (six males, six females; age 68.7±1.0 yr) subjects had measurements of blood glucose, serum insulin and plasma incretin hormones [glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP)] and calculations of insulin resistance (homeostatic model assessment) and β-cell function corrected for insulin sensitivity, before and during intraduodenal infusions of glucose at 1, 2, or 3 kcal/min or saline for 60 minutes. The study was double-blinded and randomized, and performed in the Discipline of Medicine at the Royal Adelaide Hospital.

RESULTS

At baseline, blood glucose and serum insulin were slightly higher in the older subjects (P<0.001), whereas GLP-1 and GIP were comparable between groups. In both groups, the glycemic, insulinemic, and GLP-1 responses were dependent on the duodenal glucose load in a nonlinear fashion (P<0.001). The glycemic response was greater (P<0.001) in the older subjects, whereas GLP-1 and GIP responses were comparable between groups. The older subjects were more insulin resistant (P<0.001) and had impaired β-cell function, particularly at higher glucose loads (P<0.05).

CONCLUSION

When glucose is infused into the small intestine at equal rates in healthy young and older subjects, GLP-1 and GIP responses are comparable, indicating that impaired incretin secretion does not account for age-related glucose intolerance.

Repression of a potassium channel by nuclear hormone receptor and TGF-β signaling modulates insulin signaling in Caenorhabditis elegans

Transforming growth factor β (TGF-β) signaling acts through Smad proteins to play fundamental roles in cell proliferation, differentiation, apoptosis, and metabolism. The Receptor associated Smads (R-Smads) interact with DNA and other nuclear proteins to regulate target gene transcription. Here, we demonstrate that the Caenorhabditis elegans R-Smad DAF-8 partners with the nuclear hormone receptor NHR-69, a C. elegans ortholog of mammalian hepatocyte nuclear factor 4α HNF4α), to repress the exp-2 potassium channel gene and increase insulin secretion. We find that NHR-69 associates with DAF-8 both in vivo and in vitro. Functionally, daf-8 nhr-69 double mutants show defects in neuropeptide secretion and phenotypes consistent with reduced insulin signaling such as increased expression of the sod-3 and gst-10 genes and a longer life span. Expression of the exp-2 gene, encoding a voltage-gated potassium channel, is synergistically increased in daf-8 nhr-69 mutants compared to single mutants and wild-type worms. In turn, exp-2 acts selectively in the ASI neurons to repress the secretion of the insulin-like peptide DAF-28. Importantly, exp-2 mutation shortens the long life span of daf-8 nhr-69 double mutants, demonstrating that exp-2 is required downstream of DAF-8 and NHR-69. Finally, animals over-expressing NHR-69 specifically in DAF-28–secreting ASI neurons exhibit a lethargic, hypoglycemic phenotype that is rescued by exogenous glucose. We propose a model whereby DAF-8/R-Smad and NHR-69 negatively regulate the transcription of exp-2 to promote neuronal DAF-28 secretion, thus demonstrating a physiological crosstalk between TGF-β and HNF4α-like signaling in C. elegans. NHR-69 and DAF-8 dependent regulation of exp-2 and DAF-28 also provides a novel molecular mechanism that contributes to the previously recognized link between insulin and TGF-β signaling in C. elegans.

All animals must ensure metabolic homeostasis; if they fail to do so, diseases such as obesity and diabetes can develop. To maintain glucose balance, insulin is secreted upon glucose intake in a highly regulated and coordinated process. Previous studies suggested that the transforming growth factor beta (TGF-β) signaling pathway regulates insulin secretion in mammals. In the genetically tractable roundworm Caenorhabditis elegans, TGF-β and insulin signaling modulate larval development and aging, although the molecular link between insulin and TGF-β signaling remains poorly understood. In this study, we show that the TGF-β signaling component DAF-8 partners with NHR-69, a nuclear hormone receptor, to control the expression of the potassium channel exp-2, which in turn modulates the secretion of an insulin-like peptide. A loss-of-function exp-2 mutant exhibits increased insulin secretion and a shortened life span, whereas a gain-of-function mutant exhibits decreased insulin secretion. We also show that tissue-specific expression of nhr-69 in a pair of neurons that secrete neuropeptides causes reduced glucose content, increased insulin-like peptide levels and a lethargic phenotype. Because insulin and TGF-β signaling are linked to numerous diseases, our data may provide novel insights into the mechanisms contributing to pathophysiological changes.

Effects of variations in intragastric volume on blood pressure and splanchnic blood flow during intraduodenal glucose infusion in healthy older subjects

The postprandial reduction in blood pressure (BP) is triggered by the interaction of nutrients with the small intestine and associated with an increase in splanchnic blood flow. Gastric distension may attenuate the postprandial fall in BP. The aim of this study was to determine the effects of differences in intragastric volume, including distension at a low (100 ml) volume, on BP and superior mesenteric artery (SMA) blood flow responses to intraduodenal glucose in healthy older subjects. BP and heart rate (HR; automated device), SMA blood flow (Doppler ultrasound), mesenteric vascular resistance (MVR), and plasma norepinephrine of nine male subjects (65-75 yr old) were measured after an overnight fast on 4 separate days in random order. On each day, subjects were intubated with a nasoduodenal catheter, incorporating a duodenal infusion port, and orally with a second catheter, incorporating a barostat bag, positioned in the fundus. Each subject received a 60-min (t = 0-60 min) intraduodenal glucose infusion (3 kcal/min) and gastric distension at a volume of 1) 0 ml (V0), 2) 100 ml (V100), 3) 300 ml (V300), or 4) 500 ml (V500). Systolic BP fell (P < 0.05) during V0, but not during V100, V300, or V500. In contrast, HR (P < 0.01) and SMA blood flow (P < 0.001) increased and MVR decreased (P < 0.05) comparably on all 4 days. Plasma norepinephrine rose (P < 0.01) in response to intraduodenal glucose, with no difference between the four treatments. There was a relationship between the areas under the curve for the change in systolic BP from baseline with intragastric volume (r = 0.60, P < 0.001). In conclusion, low-volume (≤100 ml) gastric distension has the capacity to abolish the fall in BP induced by intraduodenal glucose in healthy older subjects without affecting SMA blood flow or MVR. These observations support the concept that nonnutrient gastric distension prior to a meal has potential therapeutic applications in the management of postprandial hypotension.

Effects of different sweet preloads on incretin hormone secretion, gastric emptying, and postprandial glycemia in healthy humans

BACKGROUND

Macronutrient "preloads" can stimulate glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), slow gastric emptying, and reduce postprandial glycemic excursions. After sweet preloads, these effects may be signaled by sodium-glucose cotransporter-1 (SGLT1), sweet taste receptors, or both.

OBJECTIVE

We determined the effects of 4 sweet preloads on GIP and GLP-1 release, gastric emptying, and postprandial glycemia.

DESIGN

Ten healthy subjects were studied on 4 separate occasions each. A preload drink containing 40 g glucose, 40 g tagatose/isomalt mixture (TIM), 40 g 3-O-methylglucose (3OMG; a nonmetabolized substrate of SGLT1), or 60 mg sucralose was consumed 15 min before a (13)C-octanoic acid-labeled mashed potato meal. Blood glucose, plasma total GLP-1 and GIP, serum insulin, and gastric emptying were determined.

RESULTS

Both glucose and 3OMG stimulated GLP-1 and GIP release in advance of the meal (each P < 0.05), whereas TIM and sucralose did not. The overall postprandial GLP-1 response was greater after glucose, 3OMG, and TIM than after sucralose (P < 0.05), albeit later after TIM than the other preloads. The blood glucose and insulin responses in the first 30 min after the meal were greatest after glucose (each P < 0.05). Gastric emptying was slower after both 3OMG and TIM than after sucralose (each P < 0.05).

CONCLUSIONS

In healthy humans, SGLT1 substrates stimulate GLP-1 and GIP and slow gastric emptying, regardless of whether they are metabolized, whereas the artificial sweetener sucralose does not. Poorly absorbed sweet tastants (TIM), which probably expose a greater length of gut to nutrients, result in delayed GLP-1 secretion but not in delayed GIP release. These observations have the potential to optimize the use of preloads for glycemic control. This trial was registered at www.actr.org.au as ACTRN12611000775910.

Gastric emptying of a liquid nutrient meal in the critically ill: relationship between scintigraphic and carbon breath test measurement

OBJECTIVE

It is assumed that delayed gastric emptying (GE) occurs frequently in critical illness; however, the prevalence of slow GE has not previously been assessed using scintigraphy. Furthermore, breath tests could potentially provide a convenient method of quantifying GE, but have not been validated in this setting. The aims of this study were to (i) determine the prevalence of delayed GE in unselected, critically ill patients and (ii) evaluate the relationships between GE as measured by scintigraphy and carbon breath test.

DESIGN

Prospective observational study.

SETTING

Mixed medical/surgical intensive care unit.

PATIENTS

25 unselected, mechanically ventilated patients (age 66 years (49-72); and 14 healthy subjects (age 62 years (19-84)).

INTERVENTIONS

GE was measured using scintigraphy and (14)C-breath test. A test meal of 100 ml Ensure (standard liquid feed) labelled with (14)C octanoic acid and (99m)Technetium sulphur colloid was placed in the stomach via a nasogastric tube.

MAIN OUTCOME MEASURES

Gastric 'meal' retention (scintigraphy) at 60, 120, 180 and 240 min, breath test t(50) (BTt(50)), and GE coefficient were determined.

RESULTS

Of the 24 patients with scintigraphic data, GE was delayed at 120 min in 12 (50%). Breath tests correlated well with scintigraphy in both patients and healthy subjects (% retention at 120 min vs BTt(50); r(2)=0.57 healthy; r(2)=0.56 patients; p≤0.002 for both).

CONCLUSIONS

GE of liquid nutrient is delayed in approximately 50% of critically ill patients. Breath tests correlate well with scintigraphy and are a valid method of GE measurement in this group.

The oligosaccharide α-cyclodextrin has modest effects to slow gastric emptying and modify the glycaemic response to sucrose in healthy older adults

In healthy older subjects, the glycaemic response to carbohydrate-containing meals is dependent on gastric emptying and intestinal absorption; when the latter is slowed, the magnitude of the rise in glucose is attenuated. The oligosaccharide α-cyclodextrin has been reported to diminish the glycaemic response to starch in young adults; this effect has been attributed to the inhibition of pancreatic amylase. We examined the effects of α-cyclodextrin on gastric emptying of, and the glycaemic and insulinaemic responses to, oral sucrose in healthy older subjects; as sucrose is hydrolysed by intestinal disaccharides, any effect(s) of α-cyclodextrin would not be attributable to amylase inhibition. A total of ten subjects (seven males and three females, age 68-76 years) were studied on 2 d. Gastric emptying, blood glucose and serum insulin were measured after ingestion of a 300 ml drink containing 100 g sucrose, labelled with (99m)Tc-sulphur colloid, with or without 10 g α-cyclodextrin. Gastric emptying was slowed slightly by α-cyclodextrin; this effect was evident between 135 and 195 min and was associated with a slight increase (P < 0·05) in distal stomach retention. After α-cyclodextrin, blood glucose was slightly less (P < 0·05) at 60 min, and serum insulin was less (P < 0·0005) at 90 and 120 min. There was no difference in the incremental areas under the curve (iAUC) for blood glucose, but there was a trend for the iAUC for serum insulin to be lower (P = 0·09) after α-cyclodextrin. We conclude that in a dose of 10 g, α-cyclodextrin has modest effects to slow gastric emptying of, and modify the glycaemic and insulinaemic responses to, oral sucrose, probably due to delayed intestinal carbohydrate absorption.

The alpha (α)-glucosidase inhibitor, acarbose, attenuates the blood pressure and splanchnic blood flow responses to intraduodenal sucrose in older adults

BACKGROUND

Postprandial hypotension is an important problem in the elderly and may be triggered by the increase in splanchnic blood flow induced by a meal. Acarbose attenuates the fall in blood pressure (BP) induced by oral sucrose and may be useful in the management of postprandial hypotension. It is not known whether the effect of acarbose on postprandial BP reflects slowing of gastric emptying and/or carbohydrate absorption nor whether acarbose affects splanchnic blood flow. We examined the effects of intraduodenal (ID) acarbose on the BP, heart rate, superior mesenteric artery (SMA) flow, and glycemic and insulin responses to ID sucrose in older participants--this approach excluded any "gastric" effect of acarbose.

METHODS

Eight healthy participants (four male and four female, age 66-77 years) received an ID infusion of sucrose (~6 kcal/min), with or without acarbose (100 mg), over 60 minutes. BP, heart rate, SMA flow, blood glucose, and serum insulin were measured.

RESULTS

Acarbose markedly attenuated the falls in systolic (p < .01) and diastolic (p < .05) BP and rises in heart rate (p < .05), SMA flow (p < .05), blood glucose (p < .01), and serum insulin (p < .05). The maximum fall in systolic BP and peak SMA flow was inversely related on the control day (r(2) = -.53, p < .05) but not with acarbose (r(2) = .03, p = .70).

CONCLUSIONS

We conclude that in healthy older participants receiving ID sucrose, (a) acarbose markedly attenuates the hypotensive response by slowing carbohydrate absorption and attenuating the rise in splanchnic blood flow and (b) the fall in BP is related to the concomitant increase in SMA flow.

Orlistat accentuates the fat-induced fall in blood pressure in older adults

Postprandial hypotension may be influenced by the digestion of fat. The aim of the present study was to evaluate the hypothesis that products of fat digestion mediate the hypotensive response to fat. In part A of the study, nine healthy older subjects were studied on three separate occasions in randomised order. Blood pressure, heart rate (HR), plasma TAG and gastric emptying were measured following the ingestion of equivolaemic drinks: (1) 300 ml of high-fat drink (88 % fat); (2) fat drink mixed with 120 mg orlistat (lipase inhibitor); (3) water (control). In part B of the study, ten healthy older subjects were studied on two separate occasions. Blood pressure, HR, plasma TAG and superior mesenteric artery flow were measured during 90 min intraduodenal infusions of 10 % intralipid (2·7 ml/min), with and without 120 mg orlistat. Oral fat ingestion was associated with decreases in systolic and diastolic blood pressures (both P = 0·0001) that were greater when orlistat was co-administered (both P < 0·05), and an increase in HR (P = 0·0001) that was inhibited by orlistat co-administration (P < 0·03). Gastric emptying was slowed by oral fat digestion, and orlistat administration inhibited this slowing (P < 0·04). Intraduodenal fat infusion was not associated with changes in blood pressure but increased HR (P < 0·0001), an effect attenuated by orlistat (P < 0·05). In conclusion, orlistat potentiates the hypotensive response to oral fat in older adults, possibly as a result of faster gastric emptying of fat. The results do not support a role for fat digestion in lowering blood pressure.

Chemokine receptor CCR5: from AIDS to atherosclerosis

There is increasing recognition of an important contribution of chemokines and their receptors in the pathology of atherosclerosis and related cardiovascular disease. The chemokine receptor CCR5 was initially known for its role as a co-receptor for HIV infection of macrophages and is the target of the recently approved CCR5 antagonist maraviroc. However, evidence is now emerging supporting a role for CCR5 and its ligands CCL3 (MIP-1α), CCL4 (MIP-1β) and CCL5 (RANTES) in the initiation and progression of atherosclerosis. Specifically, the CCR5 deletion polymorphism CCR5delta32, which confers resistance to HIV infection, has been associated with a reduced risk of cardiovascular disease and both CCR5 antagonism and gene deletion reduce atherosclerosis in mouse models of the disease. Antagonism of CCL5 has also been shown to reduce atherosclerotic burden in these animal models. Crucially, CCR5 and its ligands CCL3, CCL4 and CCL5 have been identified in human and mouse vasculature and have been detected in human atherosclerotic plaque. Not unexpectedly, CC chemokines have also been linked to saphenous vein graft disease, which shares similarity to native vessel atherosclerosis. Distinct roles for chemokine-receptor systems in atherogenesis have been proposed, with CCR5 likely to be critical in recruitment of monocytes to developing plaques. With an increased burden of cardiovascular disease observed in HIV-infected individuals, the potential cardiovascular-protective effects of drugs that target the CCR5 receptor warrant greater attention. The availability of clinically validated antagonists such as maraviroc currently provides an advantage for targeting of CCR5 over other chemokine receptors.

Effects of small intestinal glucose load on blood pressure, splanchnic blood flow, glycemia, and GLP-1 release in healthy older subjects

Postprandial hypotension is an important problem, particularly in the elderly. The fall in blood pressure is dependent on small intestinal glucose delivery and, possibly, changes in splanchnic blood flow, the release of glucagon-like peptide-1 (GLP-1), and sympathetic nerve activity. We aimed to determine in healthy older subjects, the effects of variations in small intestinal glucose load on blood pressure, superior mesenteric artery flow, GLP-1, and noradrenaline. Twelve subjects (6 male, 6 female; ages 65-76 yr) were studied on four separate occasions, in double-blind, randomized order. On each day, subjects were intubated via an anesthetized nostril, with a nasoduodenal catheter, and received an intraduodenal infusion of either saline (0.9%) or glucose at a rate of 1, 2, or 3 kcal/min (G1, G2, G3, respectively), for 60 min (t = 0-60 min). Between t = 0 and 60 min, there were falls in systolic and diastolic blood pressure following G2 and G3 (P = 0.003 and P < 0.001, respectively), but no change during saline or G1. Superior mesenteric artery flow increased slightly during G1 (P = 0.01) and substantially during G2 (P < 0.001) and G3 (P < 0.001), but not during saline. The GLP-1 response to G3 was much greater (P < 0.001) than to G2 and G1. Noradrenaline increased (P < 0.05) only during G3. In conclusion, in healthy older subjects the duodenal glucose load needs to be > 1 kcal/min to elicit a significant fall in blood pressure, while the response may be maximal when the rate is 2 kcal/min. These observations have implications for the therapeutic strategies to manage postprandial hypotension by modulating gastric emptying.

Comparative effects of glucose and xylose on blood pressure, gastric emptying and incretin hormones in healthy older subjects

Postprandial hypotension is an important disorder for which current management is suboptimal. In healthy older subjects, oral and small-intestinal glucose administration decreases blood pressure (BP), and the magnitude of the reduction is dependent on the rate of glucose entry into the small intestine and, possibly, the release of glucagon-like peptide-1 (GLP-1). There is little information about the effects of other carbohydrates, particularly those poorly absorbed, on BP. The aim of the present study was to compare the effects of drinks containing xylose, glucose or water alone on BP, gastric emptying (GE), incretin hormone secretion, glycaemia and insulinaemia in healthy older subjects. A total of eight healthy older subjects (aged 65-75 years) had simultaneous measurements of BP (DINAMAP), GE (three-dimensional ultrasound), blood glucose, serum insulin, GLP-1 and glucose-dependent insulinotropic peptide (GIP), on three separate occasions, in a double-blind, randomised order. On each day, subjects consumed a 300 ml drink of water, glucose (50 g) or d-xylose (50 g). Glucose (P = 0·02), but not xylose (P = 0·63), was associated with a fall in BP. There was no difference in the GE of glucose and xylose (P = 0·47); both emptied slower than water (P < 0·001). Xylose had minimal effects on blood glucose, serum insulin or serum GIP, but was more potent than glucose in stimulating GLP-1 (P = 0·002). In conclusion, in healthy older subjects, xylose empties from the stomach at the same rate as glucose, but has no effect on BP, possibly because it is a potent stimulus for GLP-1 release. Xylose may be considered as an alternative sweetener to glucose in the management of postprandial hypotension.

Gastric emptying, incretin hormone secretion, and postprandial glycemia in cystic fibrosis--effects of pancreatic enzyme supplementation

CONTEXT

Postprandial hyperglycemia is an important clinical problem in cystic fibrosis (CF), but the contribution of fat malabsorption, rapid gastric emptying, and the incretin axis has not been widely considered.

OBJECTIVE

The aim of this study was to evaluate these aspects of gut function in nondiabetic CF patients.

DESIGN AND SETTING

We conducted a randomized, double-blind, placebo-controlled crossover study at a clinical research laboratory.

PATIENTS

Five nondiabetic CF patients (three males; age, 25.8 ± 1.0 yr; body mass index, 20.2 ± 1.1 kg/m(2)) with exocrine pancreatic insufficiency and six healthy subjects of similar age and body mass index participated in the study.

INTERVENTIONS

CF patients consumed a radiolabeled mashed potato meal on 2 separate days, together with four capsules of Creon Forte (100,000 IU lipase) or placebo. Healthy subjects consumed the meal once, without pancreatic enzymes.

MAIN OUTCOME MEASURES

Gastric emptying was measured using scintigraphy, and blood was sampled frequently for blood glucose and plasma glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and glucagon concentrations.

RESULTS

CF patients had more rapid gastric emptying (P < 0.001), impaired secretion of GLP-1 (P < 0.01) and GIP (P < 0.001), and greater postprandial glycemic excursions (P < 0.001) than healthy subjects. Pancreatic enzyme supplementation normalized gastric emptying and GLP-1 secretion and tended to increase glucagon (P = 0.08), but did not completely restore GIP secretion or normalize postprandial blood glucose. There was an excellent correlation between gastric emptying and blood glucose concentration at 60 min (R = 0.75; P = 0.01).

CONCLUSIONS

Pancreatic enzyme supplementation plays an important role in incretin secretion, gastric emptying, and postprandial hyperglycemia in CF.

Convergent genesis of an adult neural crest-like dermal stem cell from distinct developmental origins

Skin-derived precursors (SKPs) are multipotent dermal stem cells that reside within a hair follicle niche and that share properties with embryonic neural crest precursors. Here, we have asked whether SKPs and their endogenous dermal precursors originate from the neural crest or whether, like the dermis itself, they originate from multiple developmental origins. To do this, we used two different mouse Cre lines that allow us to perform lineage tracing: Wnt1-cre, which targets cells deriving from the neural crest, and Myf5-cre, which targets cells of a somite origin. By crossing these Cre lines to reporter mice, we show that the endogenous follicle-associated dermal precursors in the face derive from the neural crest, and those in the dorsal trunk derive from the somites, as do the SKPs they generate. Despite these different developmental origins, SKPs from these two locations are functionally similar, even with regard to their ability to differentiate into Schwann cells, a cell type only thought to be generated from the neural crest. Analysis of global gene expression using microarrays confirmed that facial and dorsal SKPs exhibit a very high degree of similarity, and that they are also very similar to SKPs derived from ventral dermis, which has a lateral plate origin. However, these developmentally distinct SKPs also retain differential expression of a small number of genes that reflect their developmental origins. Thus, an adult neural crest-like dermal precursor can be generated from a non-neural crest origin, a finding with broad implications for the many neuroendocrine cells in the body.

Measurement of gastric emptying of a high-nutrient liquid by 3D ultrasonography in diabetic gastroparesis

BACKGROUND

Gastric emptying (GE) is delayed in 30-50% of patients with longstanding diabetes. Scintigraphy represents the 'gold standard' for measurement of GE, but is associated with a radiation burden. Three-dimensional (3D) ultrasonography has recently been demonstrated to provide a valid measure of liquid GE in healthy subjects; however, the technique has not been validated in patients with gastroparesis. The primary aim of this study was to compare measurements of GE of a high-nutrient glucose drink by 3D ultrasonography and scintigraphy in diabetic gastroparesis.

METHODS

Ten patients (eight type 1, two type 2, 6M, 4F, aged 46.1 ± 4.5 years, BMI 29.1 ± 1.6 kg m(-2), duration 19.6 ± 3.3 years) with diabetic gastroparesis [defined as retention at 100 min of solid (100 g minced beef) ≥ 61% and/or 50% emptying time (T50) of liquid (150 mL 10% dextrose) ≥ 31 min], were studied. Concurrent measurements of GE by scintigraphy and 3D ultrasonography were performed following ingestion of 75 g glucose in 300 mL water labeled with 20 MBq (99m) Tc-sulfur colloid.

KEY RESULTS

There was no significant difference in GE between the two techniques (T50s: scintigraphy - 103.3 ± 10.0 min VS 3D ultrasonography - 98.8 ± 10.4 min; P = 0.60). There was a significant correlation between scintigraphic and ultrasonographic T50s (r = 0.67, P = 0.03). The limits of agreement for the T50s were -57.22 min and +48.22 min (mean difference -4.5 min). Blood glucose after the drink was greater when GE was relatively more rapid (e.g. at t = 60 min; scintigraphy: r = -0.65, P = 0.04; 3D ultrasonography: r = -0.78, P = 0.008).

CONCLUSIONS & INFERENCES

Three-dimensional ultrasonography appears to provide a valid, and non-invasive, measure of GE of high-nutrient liquids in diabetic gastroparesis.

Diabetic gastroparesis-backwards and forwards

Diabetic gastroparesis was once thought to be rare, associated with a poor prognosis, and to affect only patients with type 1 diabetes and irreversible autonomic neuropathy. A landmark study conducted by Horowitz et al. and published in JGH in 1986 paved the way for further studies to examine the pathophysiology, natural history and prognosis of diabetic gastroparesis, as well as its optimal management. This review summarizes the developments in knowledge gained over the last ∼25 years that have led to understanding about normal and disordered gastric emptying in diabetes, with a particular emphasis on the inter-relationship between the rate of gastric emptying and the regulation of blood glucose.

Effects of GLP-1 and incretin-based therapies on gastrointestinal motor function

Glucagon-like peptide 1 (GLP-1) is a hormone secreted predominantly by the distal small intestine and colon and released in response to enteral nutrient exposure. GLP-1-based therapies are now used widely in the management of type 2 diabetes and have the potential to be effective antiobesity agents. Although widely known as an incretin hormone, there is a growing body of evidence that GLP-1 also acts as an enterogastrone, with profound effects on the gastrointestinal motor system. Moreover, the effects of GLP-1 on gastrointestinal motility appear to be pivotal to its effect of reducing postprandial glycaemic excursions and may, potentially, represent the dominant mechanism. This review summarizes current knowledge of the enterogastrone properties of GLP-1, focusing on its effects on gut motility at physiological and pharmacological concentrations, and the motor actions of incretin-based therapies. While of potential importance, the inhibitory action of GLP-1 on gastric acid secretion is beyond the scope of this paper.

Gastrointestinal hormonal dysfunction in gastroparesis and functional dyspepsia

BACKGROUND

Numerous hormones secreted by the gut, during both the fasted state and in response to a meal, influence gastrointestinal motor and/or sensory function, and appear to contribute to the pathogenesis of delayed gastric emptying associated with gastroparesis, functional dyspepsia (FD) and feed intolerance in critical illness. Gut hormones are, accordingly, potential targets for the management of these patients.

PURPOSE

This article will discuss the hypersensitivity to enteral fat and endogenous (nutrient-stimulated) and exogenous cholecystokinin (CCK) in patients with FD, and the elevation in both fasting and postprandial CCK levels evident in this group. It will review the use of pharmacological agonists of motilin and ghrelin, which accelerate gastric emptying, in the management of gastroparesis and FD. The frequent finding of markedly delayed gastric emptying in the critically ill will be examined; this is associated with elevated plasma CCK and peptide YY in both the fasted and postprandial states, which may account for the increase in small intestinal nutrient inhibitory feedback on gastric motility in this group. The concepts that the rate of gastric emptying is a major determinant of postprandial glycemic excursions in diabetes, and that modulation of gastric emptying may improve glycemic control, will be addressed; in type 1 and insulin-treated type 2 diabetic patients, co-ordination of insulin administration with nutrient delivery and absorption should be optimized, while type 2 patients who are not on insulin are likely to respond to dietary and/or pharmacological interventions which slow gastric emptying.

Effects of metoclopramide on duodenal motility and flow events, glucose absorption, and incretin hormone release in response to intraduodenal glucose infusion

The contribution of small intestinal motor activity to nutrient absorption is poorly defined. A reduction in duodenal flow events after hyoscine butylbromide, despite no change in pressure waves, was associated with reduced secretion of the incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) and a delay in glucose absorption. The aim of this study was to investigate the effect of metoclopramide on duodenal motility and flow events, incretin hormone secretion, and glucose absorption. Eight healthy volunteers (7 males and 1 female; age 29.8 ± 4.6 yr; body mass index 24.5 ± 0.9 kg/m²) were studied two times in randomized order. A combined manometry and impedance catheter was used to measure pressure waves and flow events in the same region of the duodenum simultaneously. Metoclopramide (10 mg) or control was administered intravenously as a bolus, followed by an intraduodenal glucose infusion for 60 min (3 kcal/min) incorporating the ¹⁴C-labeled glucose analog 3-O-methylglucose (3-OMG). We found that metoclopramide was associated with more duodenal pressure waves and propagated pressure sequences than control (P < 0.05 for both) during intraduodenal glucose infusion. However, the number of duodenal flow events, blood glucose concentration, and plasma 3-[¹⁴C]OMG activity did not differ between the two study days. Metoclopramide was associated with increased plasma concentrations of GLP-1 (P < 0.05) and GIP (P = 0.07) but lower plasma insulin concentrations (P < 0.05). We concluded that metoclopramide was associated with increased frequency of duodenal pressure waves but no change in duodenal flow events and glucose absorption. Furthermore, GLP-1 and GIP release increased with metoclopramide, but insulin release paradoxically decreased.

Diabetic gastroparesis and its impact on glycemia

Diabetes is the most common cause of gastroparesis and it is now recognized that the relationship between gastric emptying and glycemia is complex and intertwined. Postprandial blood glucose levels influence, and are influenced by, the rate of gastric emptying, highlighting the difficulty in determining which is the cause and which is the effect. Novel diagnostic techniques and therapeutic strategies have been developed for the management of diabetic gastroparesis. This article highlights recent advances in knowledge about diabetic gastroparesis, with an emphasis on the inter-relationships between disordered gastric motor function on glycemia and vice versa, as well as therapeutic strategies for optimizing glycemic control using modulation of gastric emptying.

Effects of gastric distension on blood pressure and superior mesenteric artery blood flow responses to intraduodenal glucose in healthy older subjects

Postprandial hypotension occurs frequently and is associated with increased morbidity. Gastric distension may attenuate the postprandial fall in blood pressure (BP). Using a barostat, we sought to determine the effects of gastric distension on BP, heart rate (HR), and superior mesenteric artery (SMA) blood flow responses to intraduodenal glucose in eight (6 men, 2 women) healthy older (65-75 yr old) subjects. BP and HR were measured using an automated device and SMA blood flow was measured using Doppler ultrasound on 4 days in random order. SMA blood flow was calculated using the radius of the SMA and time-averaged mean velocity. Subjects were intubated with a nasoduodenal catheter incorporating a duodenal infusion port. On 2 of the 4 days, they were intubated orally with a second catheter, incorporating a barostat bag, positioned in the fundus and set at 8 mmHg above minimal distending pressure. Each subject received a 60-min (0-60 min) intraduodenal infusion of glucose (3 kcal/min) or saline (0.9%); therefore, the four study conditions were as follows: intraduodenal glucose + barostat (glucose + distension), intraduodenal saline + barostat (saline + distension), intraduodenal glucose (glucose), and intraduodenal saline (saline). Systolic and diastolic BP fell during glucose compared with saline (P = 0.05 and P = 0.003, respectively) and glucose + distension (P = 0.01 and P = 0.05, respectively) and increased during saline + distension compared with saline (P = 0.04 and P = 0.006, respectively). The maximum changes in systolic BP were -14 +/- 5, +11 +/- 2, -3 +/- 4, and +15 +/- 3 mmHg for glucose, saline, glucose + distension, and saline + distension, respectively. There was an increase in HR during glucose and glucose + distension (maximum rise = 14 +/- 2 and 14 +/- 3 beats/min, respectively), but not during saline or saline + distension. SMA blood flow increased during glucose and glucose + distension (2,388 +/- 365 and 1,673 +/- 187 ml/min, respectively), but not during saline, and tended to decrease during saline + distension (821 +/- 115 and 864 +/- 116 ml/min, respectively). In conclusion, gastric distension has the capacity to abolish the fall in BP and attenuate the rise in SMA blood flow induced by intraduodenal glucose in healthy older subjects.

Effect of the artificial sweetener, sucralose, on small intestinal glucose absorption in healthy human subjects

It has been reported that the artificial sweetener, sucralose, stimulates glucose absorption in rodents by enhancing apical availability of the transporter GLUT2. We evaluated whether exposure of the proximal small intestine to sucralose affects glucose absorption and/or the glycaemic response to an intraduodenal (ID) glucose infusion in healthy human subjects. Ten healthy subjects were studied on two separate occasions in a single-blind, randomised order. Each subject received an ID infusion of sucralose (4 mM in 0.9% saline) or control (0.9% saline) at 4 ml/min for 150 min (T = - 30 to 120 min). After 30 min (T = 0), glucose (25 %) and its non-metabolised analogue, 3-O-methylglucose (3-OMG; 2.5 %), were co-infused intraduodenally (T = 0-120 min; 4.2 kJ/min (1 kcal/min)). Blood was sampled at frequent intervals. Blood glucose, plasma glucagon-like peptide-1 (GLP-1) and serum 3-OMG concentrations increased during ID glucose/3-OMG infusion (P < 0.005 for each). However, there were no differences in blood glucose, plasma GLP-1 or serum 3-OMG concentrations between sucralose and control infusions. In conclusion, sucralose does not appear to modify the rate of glucose absorption or the glycaemic or incretin response to ID glucose infusion when given acutely in healthy human subjects.

Effects of physiological hyperglycemia on duodenal motility and flow events, glucose absorption, and incretin secretion in healthy humans

CONTEXT

Acute hyperglycemia slows gastric emptying, but its effects on small intestinal motor activity and glucose absorption are unknown. In type 2 diabetes, the postprandial secretion of glucose-dependent insulinotropic polypeptide (GIP) is preserved, but that of glucagon-like peptide-1 (GLP-1) is possibly reduced; whether the latter is secondary to hyperglycemia or diabetes per se is unknown.

AIM

The aim was to investigate the effects of acute hyperglycemia on duodenal motility and flow events, glucose absorption, and incretin hormone secretion.

METHODS

Nine healthy volunteers were studied on two occasions. A combined manometry/impedance catheter was positioned in the duodenum. Blood glucose was clamped at either 9 mmol/liter (hyperglycemia) or 5 mmol/liter (euglycemia) throughout the study. Manometry and impedance recordings continued between T=-10 min and T=180 min. Between T=0 and 60 min, an intraduodenal glucose infusion was given (approximately 3 kcal/min), together with 14C-labeled 3-O-methylglucose (3-OMG) to evaluate glucose absorption.

RESULTS

Hyperglycemia had no effect on duodenal pressure waves or flow events during the 60 min of intraduodenal glucose infusion, when compared to euglycemia. During hyperglycemia, there was an increase in plasma GIP (P<0.05) and 14C-3-OMG (P<0.05) but no effect on GLP-1 concentrations in response to the intraduodenal infusion, compared to euglycemia.

CONCLUSION

Acute hyperglycemia in the physiological range has no effect on duodenal pressure waves and flow events but is associated with increased GIP secretion and rate of glucose absorption in response to intraduodenal glucose.

Potentially modifiable risk factors for adverse pregnancy outcomes in women with psoriasis

BACKGROUND

Data on pregnancy outcomes among women with psoriasis are lacking. However, there are several known comorbidities of psoriasis, including obesity, smoking and depression, each of which increases the risk for negative birth outcomes.

OBJECTIVES

To determine if pregnant women with psoriasis have an excess of potentially modifiable risk factors for adverse pregnancy outcomes.

METHODS

Prospectively collected data from the Organization of Teratology Information Specialists (OTIS) Autoimmune Diseases in Pregnancy Project were analysed to compare the prevalence of selected risk factors between 170 pregnant women with psoriasis and 158 nondiseased controls.

RESULTS

Women with psoriasis were more likely to be overweight/obese prior to pregnancy (P < 0.0001), to smoke (P < 0.0001), or to have a diagnosis of depression (P = 0.03), and were less likely to have been taking preconceptional vitamin supplements (P = 0.004). After controlling for race/ethnicity and socioeconomic status, women with psoriasis were 2.37 (95% confidence interval 1.45-3.87) times more likely to be overweight/obese as women without psoriasis. Duration of disease, age at onset, measures of disease impact during pregnancy, or use of biologics in pregnancy were not significant predictors of overweight/obesity in the subset of psoriatic women.

CONCLUSIONS

Pregnant women with psoriasis may be at increased risk for adverse pregnancy outcomes due to comorbidities or other health behaviours associated with the disease. These should be taken into consideration during clinical treatment of women with psoriasis who are in their childbearing years.

Combined effect of maternal serotonin transporter genotype and prenatal stress in modulating offspring social interaction in mice

Several studies suggest that prenatal stress is a possible risk factor in the development of autism spectrum disorders. However, many children exposed to stress prenatally are born healthy and develop typically, suggesting that other factors must contribute to autism. Genes that contribute to stress reactivity may, therefore, exacerbate prenatal stress-mediated behavioral changes in the adult offspring. One candidate gene linked to increased stress reactivity encodes the serotonin transporter. Specifically, an insertion/deletion (long/short allele) polymorphism upstream of the serotonin transporter gene correlates with differential expression and function of the serotonin transporter and a heightened response to stressors. Heterozygous serotonin transporter knockout mice show reductions in serotonin transporter expression similar to the human short polymorphism. In this study, the role of prenatal stress and maternal serotonin transporter genotype were assessed in mice to determine whether their combined effect produces reductions in social behavior in the adult offspring. Pregnant serotonin transporter heterozygous knockout and wild-type dams were placed in either a control condition or subjected to chronic variable stress. The adult offspring were subsequently assessed for social interaction and anxiety using a three-chamber social approach task, ultrasonic vocalization detection, elevated-plus maze and an open field task. Results indicated that prenatal stress and reduced serotonin transporter expression of the dam may have the combined effect of producing changes in social interaction and social interest in the offspring consistent with those observed in autism spectrum disorder. This data indicates a possible combined effect of maternal serotonin transporter genotype and prenatal stress contributing to the production of autistic-like behaviors in offspring.

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

OBJECTIVE

To determine the acute effects of exogenous glucagon-like peptide-1 on gastric emptying, glucose absorption, glycemia, plasma insulin, and glucagon in critically ill patients.

DESIGN

Randomized, double-blind, crossover study.

SETTING

Intensive care unit.

SUBJECTS

Twenty-five mechanically ventilated patients, without known diabetes, studied on consecutive days.

INTERVENTIONS

Intravenous glucagon-like peptide-1 (1.2 pmol/kg/min) or placebo was infused between -30 and 330 mins. At 0 min, 100 mL liquid nutrient (1 kcal/mL) including 100 microg of 13C-octanoic acid and 3 grams of 3-O-methyl-glucose was administered.

MEASUREMENTS AND MAIN RESULTS

Blood glucose, serum 3-O-methyl-glucose (as an index of glucose absorption), insulin and glucagon concentrations, as well as exhaled 13CO2 were measured. The gastric emptying coefficient was calculated to quantify gastric emptying. Data are presented as mean (sd). There was a nonsignificant trend for glucagon-like peptide-1 to slow gastric emptying (gastric emptying coefficient) (glucagon-like peptide-1, 2.45 [0.93] vs. placebo, 2.75 [0.83]; p = .09). In 11 of the 25 patients, gastric emptying was delayed during placebo infusion and glucagon-like peptide-1 had no detectable effect on gastric emptying in this group (1.92 [0.82] vs. 1.90 [0.68]; p = .96). In contrast, in patients who had normal gastric emptying during placebo, glucagon-like peptide-1 slowed gastric emptying substantially (2.86 [0.58] vs. 3.41 [0.37]; p = .006). Glucagon-like peptide-1 markedly reduced the rate of glucose absorption (3-O-methyl-glucose area under the curve(0-330), 37 [35] vs. 76 [51] mmol/L/min; p < .001), decreased preprandial glucagon (at 0 min change in glucagon, -15 [15] vs. -3 [14] pmol/L; p < .001), increased the insulin/glucose ratio throughout the infusion (area under the curve(-30-330), 1374 [814] vs. 1172 [649] mU/mmol/min; p = .041), and attenuated the glycemic response to the meal (glucose area under the curve(0-330), 2071 [353] vs. 2419 [594] mmol/L/min; p = .001).

CONCLUSIONS

Exogenous glucagon-like peptide-1 lowers postprandial glycemia in the critically ill. This may occur, at least in part, by slowing gastric emptying when the latter is normal but not when it is delayed.

Seasonally dynamic fungal communities in the Quercus macrocarpa phyllosphere differ between urban and nonurban environments

*The fungal richness, diversity and community composition in the Quercus macrocarpa phyllosphere were compared across a growing season in trees located in six stands within and outside a small urban center using 454-sequencing and DNA tagging. The approaches did not differentiate between endophytic and epiphytic fungal communities. *Fungi accumulated in the phyllosphere rapidly and communities were temporally dynamic, with more than a third of the analyzed operational taxonomic units (OTUs) and half of the BLAST-inferred genera showing distinct seasonal patterns. The seasonal patterns could be explained by fungal life cycles or environmental tolerances. *The communities were hyperdiverse and differed between the urban and nonurban stands, albeit not consistently across the growing season. Foliar macronutrients (nitrogen (N), potassium (K) and sulfur (S)), micronutrients (boron (B), manganese (Mn) and selenium (Se)) and trace elements (cadmium (Cd), lead (Pb) and zinc (Zn)) were enriched in the urban trees, probably as a result of anthropogenic activities. Because of correlations with the experimental layout, these chemical elements should not be considered as community drivers without further empirical studies. *We suggest that a combination of mechanisms leads to differences between urban and nonurban communities. Among those are stand isolation and size, nutrient and pollutant accumulation plus stand management, including fertilization and litter removal.

The efficient generation of induced pluripotent stem (iPS) cells from adult mouse adipose tissue-derived and neural stem cells

Ectopic expression of key reprogramming transgenes in somatic cells enables them to adopt the characteristics of pluripotency. Such cells have been termed induced pluripotent stem (iPS) cells and have revolutionized the field of somatic cell reprogramming, as the need for embryonic material is obviated. One of the issues facing both the clinical translation of iPS cell technology and the efficient derivation of iPS cell lines in the research laboratory is choosing the most appropriate somatic cell type for induction. In this study, we demonstrate the direct reprogramming of a defined population of neural stem cells (NSCs) derived from the subventricular zone (SVZ) and adipose tissue-derived cells (ADCs) from adult mice using retroviral transduction of the Yamanaka factors Oct4, Sox2, Klf4, and c-Myc, and compared the results obtained with a mouse embryonic fibroblast (mEF) control. We isolated mEFs, NSCs, and ADCs from transgenic mice, which possess a GFP transgene under control of the Oct4 promoter, and validated GFP expression as an indicator of reprogramming. While transduction efficiencies were not significantly different among the different cell types (mEFs 68.70 +/- 2.62%, ADCs 70.61 +/- 15.4%, NSCs, 68.72 +/- 3%, p = 0.97), the number of GFP-positive colonies and hence the number of reprogramming events was significantly higher for both NSCs (13.50 +/- 4.10 colonies, 0.13 +/- 0.06%) and ADCs (118.20 +/- 38.28 colonies, 1.14 +/- 0.77%) when compared with the mEF control (3.17 +/- 0.29 colonies, 0.03 +/- 0.005%). ADCs were most amenable to reprogramming with an 8- and 38-fold greater reprogramming efficiency than NSCs and mEFs, respectively. Both NSC iPS and ADC iPS cells were demonstrated to express markers of pluripotency and could differentiate to the three germ layers, both in vitro and in vivo, to cells representative of the three germ lineages. Our findings confirm that ADCs are an ideal candidate as a readily accessible somatic cell type for high efficiency establishment of iPS cell lines.

Effects of cefaclor on gastric emptying and cholecystokinin release in healthy humans

BACKGROUND AND AIMS

In rodents, cephalosporin antibiotics can mimic peptones and stimulate release of cholecystokinin (CCK), a hormone that slows gastric emptying. The rate of gastric emptying is a major determinant of postprandial blood glucose and insulin concentrations. We therefore evaluated the effect of orally administered cefaclor on plasma CCK and gastric emptying, as well as postprandial glycemic and insulinemic responses, in healthy humans.

MATERIALS AND METHODS

We studied 8 healthy subjects on two days in double-blind, randomized order. On each day, subjects consumed 1000 mg cefaclor or placebo 30 min before a mashed potato meal labeled with (13)C octanoic acid. Blood and breath samples were collected for 4h after the meal.

RESULTS

Blood glucose, serum insulin and plasma CCK increased in response to the carbohydrate meal on both study days, and cefaclor had no effect on these responses. Similarly, the gastric half-emptying time (measured by breath test) did not differ (placebo: 137.5+/-6.0 min vs. cefaclor: 143.1+/-8.0 min).

CONCLUSION

Cefaclor, when given before a meal in the form of a capsule, does not stimulate CCK release or slow gastric emptying in healthy humans.

Endogenous glucagon-like peptide-1 slows gastric emptying in healthy subjects, attenuating postprandial glycemia

INTRODUCTION

The role of glucagon-like peptide-1 (GLP-1) in the regulation of gastric emptying is uncertain. The aim of this study was to determine the effects of endogenous GLP-1 on gastric emptying, glucose absorption, and glycemia in health.

METHODS

Ten healthy fasted subjects (eight males, two females; 48 +/- 7 yr) received the specific GLP-1 antagonist, exendin(9-39) amide [ex(9-39)NH(2)] (300 pmol/kg x min iv), or placebo, between -30 and 180 min in a randomized, double-blind, crossover fashion. At 0 min, a mashed potato meal ( approximately 2600 kJ) containing 3 g 3-ortho-methyl-D-glucose (3-OMG) and labeled with 20 MBq (99m)Technetium-sulphur colloid was eaten. Gastric emptying, including the time taken for 50% of the meal to empty from the stomach (T50), blood glucose, plasma 3-OMG, and plasma insulin were measured.

RESULTS

Ex(9-39)NH(2) accelerated gastric emptying [T50 ex(9-39)NH(2), 68 +/- 8 min, vs. placebo, 83 +/- 7 min; P < 0.001] and increased the overall glycemic response to the meal [area under the curve (0-180 min) ex(9-39)NH(2), 1540 +/- 106 mmol/liter x min, vs. placebo, 1388 +/- 90 mmol/liter x min; P < 0.02]. At 60 min, ex(9-39)NH(2) increased the rise in glycemia [ex(9-39)NH(2), 9.9 +/- 0.5 mmol/liter, vs. placebo, 8.4 +/- 0.5 mmol/liter; P < 0.01], plasma 3-OMG [ex(9-39)NH(2), 0.25 +/- 0.01 mmol/liter, vs. placebo, 0.21 +/- 0.01 mmol/liter; P < 0.05], and plasma insulin [ex(9-39)NH(2), 82 +/- 13 mU/liter, vs. placebo, 59 +/- 9 mU/liter; P < 0.05] concentrations. There was a close within-subject correlation between glycemia and gastric emptying [e.g. at 60 min, the increment in blood glucose and gastric emptying (T50); r = -0.89; P < 0.001].

CONCLUSION

GLP-1 plays a physiological role to slow gastric emptying in health, which impacts on glucose absorption and, hence, postprandial glycemia.

Effects of intravenous fructose on gastric emptying and antropyloroduodenal motility in healthy subjects

Gastric emptying (GE) of glucose is regulated closely, not only as a result of inhibitory feedback arising from the small intestine, but also because of the resulting hyperglycemia. Fructose is used widely in the diabetic diet and is known to empty from the stomach slightly faster than glucose but substantially slower than water. The aims of this study were to determine whether intravenous (iv) fructose affects GE and antropyloroduodenal motility and how any effects compare to those induced by iv glucose. Six healthy males (age: 26.7 +/- 3.8 yr) underwent concurrent measurements of GE of a solid meal (100 g ground beef labeled with 20 MBq (99m)Tc-sulfur colloid) and antropyloroduodenal motility on three separate days in randomized order during iv infusion of either fructose (0.5 g/kg), glucose (0.5 g/kg), or isotonic saline for 20 min. GE (scintigraphy), antropyloroduodenal motility (manometry), and blood glucose (glucometer) were measured for 120 min. There was a rise in blood glucose (P < 0.001) after iv glucose (peak 16.4 +/- 0.6 mmol/l) but not after fructose or saline. Intravenous glucose and fructose both slowed GE substantially (P < 0.005 for both), without any significant difference between them. Between t = 0 and 30 min, the number of antral pressure waves was less after both glucose and fructose (P < 0.002 for both) than saline, and there were more isolated pyloric pressure waves during iv glucose (P = 0.003) compared with fructose and saline (P = NS for both) infusions. In conclusion, iv fructose slows GE and modulates gastric motility in healthy subjects, and the magnitude of slowing of GE is comparable to that induced by iv glucose.

The nitric oxide synthase inhibitor, Ng-nitro-L-arginine-methyl-ester, attenuates the delay in gastric emptying induced by hyperglycaemia in healthy humans

The aim of this study was to determine whether the nitric oxide (NO) synthase inhibitor, N(g)-nitro-L-arginine-methyl-ester (L-NAME), reverses the effects of acute hyperglycaemia on gastric emptying and antropyloroduodenal (APD) motility. The study had a four-way randomized crossover (hyperglycaemia vs euglycaemia; L-NAME vs placebo) design in a clinical laboratory setting. Seven healthy volunteers [four males; age 30.3 +/- 3.8 years; body mass index (BMI) 23.6 +/- 1.2 kg m(-2)] were the study subjects. After positioning a transnasal manometry catheter across the pylorus, the blood glucose concentration was maintained at either 15 or 5 mmol L(-1) using a glucose/insulin clamp. An intravenous infusion of L-NAME (180 microg kg(-1 )h(-1)) or placebo (0.9% saline) was commenced (T = -30 min) and continued for 150 min. At T = -2 min, subjects ingested a drink containing 50 g of glucose made up to 300 mL with water. Gastric emptying was measured using 3D ultrasound, and APD motility using manometry. Hyperglycaemia slowed gastric emptying (P < 0.05), and this effect was abolished by L-NAME. L-NAME had no effect on gastric emptying during euglycaemia. Hyperglycaemia suppressed fasting antral motility [motility index: 3.9 +/- 0.8 (hyperglycaemia) vs 6.5 +/- 0.6 (euglycaemia); P < 0.01]; l-NAME suppressed postprandial antral motility [motility index: 3.6 +/- 0.2 (L-NAME) vs 5.1 +/- 0.2 (placebo); P < 0.001]. Postprandial basal pyloric pressure was higher during hyperglycaemia (P < 0.001), and lower after administration of L-NAME (P < 0.001). Slowing of gastric emptying induced by hyperglycaemia is mediated by NO, and may involve the modulation of tonic pyloric activity.

Massively parallel 454 sequencing indicates hyperdiverse fungal communities in temperate Quercus macrocarpa phyllosphere

* This study targeted the fungal communities in the phyllosphere of Quercus macrocarpa and compared the fungal species richness, diversity and community composition among trees located within and outside a small urban center using recently developed 454 sequencing and DNA tagging. * The results indicate that the fungal phyllosphere communities are extremely diverse and strongly dominated by ascomycetes, with Microsphaeropsis [two Operational Taxonomic Units (OTUs); 23.6%], Alternaria (six OTUs; 16.1%), Epicoccum (one OTU; 6.0%) and Erysiphe (two OTUs; 5.9%) as the most abundant genera. * Although the sequencing effort averaged 1000 reads per tree and detected nearly 700 distinct molecular OTUs at 95% internal transcribed spacer 1 similarity, the richness of the hyperdiverse phyllosphere communities could not be reliably estimated as nearly one-half of the molecular OTUs were singletons. * The fungal communities within and outside the urban center differed in richness and diversity, which were lower within the urban development. The two land-use types contained communities that were distinct and more than 10% of the molecular OTUs differed in their frequency.

Comparative effects of oral and intraduodenal glucose on blood pressure, heart rate, and splanchnic blood flow in healthy older subjects

Postprandial hypotension occurs frequently, particularly in the elderly. The magnitude of the fall in blood pressure (BP) and rise in heart rate (HR) in response to enteral glucose are greater when gastric emptying (GE) or small intestinal infusion are more rapid. Meal ingestion is associated with an increase in splanchnic blood flow. In contrast, gastric distension may attenuate the postprandial fall in BP. The aims of this study were to evaluate, in older subjects, the comparative effects of intraduodenal glucose infusion, at a rate similar to GE of oral glucose, on BP, HR, superior mesenteric artery (SMA) flow, and blood glucose. Eight healthy subjects (5 men, 3 women, age 66-75 yr) were studied on two occasions. On day 1, each subject ingested 300 ml of water containing 75 g glucose. GE was quantified by three-dimensional ultrasonography between time t = 0-120 min, and the rate of emptying (kcal/min) was calculated. On day 2, glucose was infused intraduodenally at the same rate as that on day 1. On both days, BP, HR, SMA flow, and blood glucose were measured. The mean GE of oral glucose was 1.3 +/- 0.1 kcal/min. Systolic BP (P < 0.01), SMA flow (P < 0.05), and blood glucose (P < 0.01) were greater and HR less (P < 0.01) after oral, compared with intraduodenal, glucose. There were comparable falls in diastolic BP during the study days (P < 0.01 for both). We conclude that the magnitude of the fall in systolic BP and rise in HR are less after oral, compared with intraduodenal, glucose, presumably reflecting the "protective" effect of gastric distension.

Effects of a protein preload on gastric emptying, glycemia, and gut hormones after a carbohydrate meal in diet-controlled type 2 diabetes

OBJECTIVE

We evaluated whether a whey preload could slow gastric emptying, stimulate incretin hormones, and attenuate postprandial glycemia in type 2 diabetes.

RESEARCH DESIGN AND METHODS

Eight type 2 diabetic patients ingested 350 ml beef soup 30 min before a potato meal; 55 g whey was added to either the soup (whey preload) or potato (whey in meal) or no whey was given.

RESULTS

Gastric emptying was slowest after the whey preload (P < 0.0005). The incremental area under the blood glucose curve was less after the whey preload and whey in meal than after no whey (P < 0.005). Plasma glucose-dependent insulinotropic polypeptide, insulin, and cholecystokinin concentrations were higher on both whey days than after no whey, whereas glucagon-like peptide 1 was greatest after the whey preload (P < 0.05).

CONCLUSIONS

Whey protein consumed before a carbohydrate meal can stimulate insulin and incretin hormone secretion and slow gastric emptying, leading to marked reduction in postprandial glycemia in type 2 diabetes.

Effects of the phases of the menstrual cycle on gastric emptying, glycemia, plasma GLP-1 and insulin, and energy intake in healthy lean women

There is evidence that the menstrual cycle affects appetite, such that energy intake is lower during the follicular compared with the luteal phase. Gastric emptying influences energy intake, glycemia, and plasma glucagon-like peptide-1 (GLP-1), insulin, and cholecystokinin (CCK) release. We hypothesized that 1) gastric emptying of a glucose drink is slower, and glycemia, plasma hormones, hunger, and energy intake are less, during the follicular compared with the luteal phase; 2) the reduction in the latter parameters during the follicular phase are related to slower gastric emptying; and 3) these parameters are reproducible when assessed twice within a particular phase of the menstrual cycle. Nine healthy, lean women were studied on three separate occasions: twice during the follicular phase (days 6-12) and once during the luteal phase (days 18-24). Following consumption of a 300-ml glucose drink (0.17 g/ml), gastric emptying, blood glucose, plasma hormone concentrations, and hunger were measured for 90 min, after which energy intake at a buffet meal was quantified. During the follicular phase, gastric emptying was slower (P < 0.05), and blood glucose (P < 0.01), plasma GLP-1 and insulin (P < 0.05), hunger (P < 0.01), and energy intake (P < 0.05) were lower compared with the luteal phase, with no differences for CCK or between the two follicular phase visits. There were inverse relationships between energy intake, blood glucose, and plasma GLP-1 and insulin concentrations with the amount of glucose drink remaining in the stomach at t = 90 min (r < -0.6, P < 0.05). In conclusion, in healthy women 1) gastric emptying of glucose is slower, and glycemia, plasma GLP-1 and insulin, hunger, and energy intake are less during the follicular compared with the luteal phase; 2) energy intake, glycemia, and plasma GLP-1 and insulin are related to gastric emptying; and 3) these parameters are reproducible when assessed twice during the follicular phase.

Insulin secretion in healthy subjects and patients with Type 2 diabetes--role of the gastrointestinal tract

Postprandial glycaemia is now recognised as the major determinant of average glycaemic control in type 2 diabetes, as assessed by glycated haemoglobin. Therefore, an understanding of the factors influencing both the rise in blood glucose and insulin secretion after a meal is fundamental to the development of dietary and pharmacological approaches to optimise glycaemic control. The gastrointestinal tract regulates the rate at which carbohydrate and other nutrients are absorbed and is the source of regulatory peptides that stimulate pancreatic insulin secretion in the setting of elevated blood glucose levels. This article highlights the importance of the gastrointestinal tract in insulin secretion and glucose homeostasis and discusses potential strategies directed at modification of gastrointestinal function in order to improve glycaemic control in the management of diabetes.

Stable transgene expression in human embryonic stem cells after simple chemical transfection

In this study we used plasmid-based vectors to investigate the transcriptional activities of three commonly used promoters in transient and stable transfection of MEL-1, a human embryonic stem (ES) cell line, using ExGen500, Fugene HD, and Lipofectamine. We demonstrated that cytomegalovirus (CMV), phosphoglycerate kinase (PGK) and human elongation factor-1alpha (EF1alpha) promoters all resulted in robust activity of a reporter gene in MEL-1 ES cell transient transfections regardless of the transfection reagent. Stable transfection outcomes varied, depending on the promoter and the transfection reagent used in the study. The phenomenon of transgene silencing was observed, most notably with the CMV vector, with which no positive stably transfected clones were obtained. Of the methods used in the study, Fugene HD resulted in the highest stable transfection rate, estimated by antibiotic selection, with plasmids containing genes under the control of the EF1alpha or PGK promoters. Stably transfected cells maintained typical hES cell morphology, with immunostaining exhibiting expression of the hES cell markers: Oct4, SSEA4, Tra-1-60, and Tra-1-81. Further, embryoid bodies formed by suspension culture retained reporter gene expression. Following injection into immunodeficient mice, the transfected cell lines showed robust formation of teratomas with cell types representative of the three germ layers.

Can prenatal ultrasound detect the effects of in-utero alcohol exposure? A pilot study

OBJECTIVES

The aim of this pilot study was to explore possible ultrasound parameters for the early detection of alcohol-mediated fetal somatic and central nervous system (CNS) maldevelopment. Maternal alcohol ingestion during pregnancy may lead to fetal alcohol spectrum disorders (FASD), which encompass a broad range of structural abnormalities including growth impairment, specific craniofacial features and CNS abnormalities. Early detection of fetuses at risk of FASD would support earlier interventions.

METHODS

We performed a longitudinal prospective pilot study from 2004 to 2006 at two sites in Ukraine. A sample of pregnant women who reported consuming moderate-to-heavy amounts of alcohol participated in a comprehensive maternal interview, and received ultrasound evaluation of fetal growth and specific fetal brain measurements during the second and third trimesters. These measurements were compared with those collected from a group of pregnant women who consumed little-to-no alcohol during pregnancy, and who were recruited and followed in the same manner.

RESULTS

From 6745 screened women, 84 moderate-to-heavy alcohol users and 82 comparison women were identified and ultrasound examinations performed. After controlling for maternal smoking, alcohol-exposed fetuses had shorter mean femur length, caval-calvarial distance and frontothalamic measurements in the second trimester (P < 0.05), and alcohol-exposed fetuses also had shorter frontothalamic distance measurements in the third trimester relative to comparison fetuses (P < 0.05). In addition, after controlling for maternal smoking, both mean orbital diameter and biparietal diameter measurements were significantly smaller on average in the alcohol-exposed group in the third trimester relative to comparison fetuses (P < 0.05).

CONCLUSIONS

Significant differences in selected somatic and brain measurements were noted between alcohol-exposed and comparison fetuses, suggesting these markers may be further explored for clinical utility in prenatal identification of affected children. Further study correlating these findings with alcohol-related physical features of the newborn and subsequent comparisons of neuro-developmental outcomes will help define potential uses of prenatal ultrasound for intervention and prevention of FASD.

Incretin-based therapies: new treatments for type 2 diabetes in the new millennium

The advent of 'incretin-based therapies' - GLP-1 agonists and dipeptidyl-peptidase-4 inhibitors - which result in improvements in glycemic control comparable to those with existing oral hypoglycemic agents, and potentially improve cardiovascular and pancreatic beta-cell function, represents a major therapeutic advance in the management of type 2 diabetes. Gastrointestinal adverse effects occur commonly with GLP-1 agonists, and rarely with DPP-4 inhibitors, but are dose-dependent and usually transient. The low risk of hypoglycemia, and beneficial or neutral effects on body weight, render GLP-1 agonists and DPP-4 inhibitors suitable alternatives to insulin secretagogues and insulin in overweight and elderly patients. Incretin-based therapies also improve quality of life in patients with type 2 diabetes, and may be cost-effective in the long term.

Diabetic gastroparesis: diagnosis and management

Gastric emptying is frequently abnormal in patients with long-standing type 1 and type 2 diabetes mellitus. Symptoms commonly associated with disordered gastric emptying include nausea, vomiting, bloating and epigastric pain, while patients are also at risk of malnutrition, weight loss, impaired drug absorption, disordered glycaemic control and poor quality of life. Although often attributed to the presence of irreversible autonomic neuropathy, acute hyperglycaemia represents a potentially reversible cause of gastric dysfunction in diabetes. Scintigraphy represents the gold standard for measuring gastric emptying. The management of diabetic gastroparesis is less than optimal, partly because the pathogenesis has not been clearly defined. Treatment approaches include dietary modification and optimization of glycaemia, and the use of prokinetic drugs, while novel therapies such as gastric electrical stimulation are the subject of ongoing investigation.

Reproducibility of energy intake, gastric emptying, blood glucose, plasma insulin and cholecystokinin responses in healthy young males

Gastric emptying, as well as intragastric meal distribution, and gastrointestinal hormones, including cholecystokinin (CCK), play an important role in appetite regulation. The evaluation of gastrointestinal factors regulating food intake is commonly performed in healthy, lean, young male participants. It has, however, been suggested that there is a marked interindividual variability in the effects of nutrient 'preloads' on energy intake in this group. Whether there is significant intraindividual variation in acute energy intake after a nutrient preload, and, if so, how this relates to day-to-day differences in gastric emptying and gastrointestinal hormone release, is unclear. The purpose of the present paper is to evaluate the hypothesis that energy intake after a nutrient preload would be reproducible and associated with reproducible patterns of gastric emptying, intragastric distribution and gastrointestinal hormone release. Fifteen healthy men (age 25 (sem 5) years) consumed a glucose preload (50 g glucose in 300 ml water; 815 kJ) on three occasions. Gastric emptying and intragastric meal distribution (using three-dimensional ultrasound), blood glucose, plasma insulin and CCK concentrations and appetite perceptions were evaluated over 90 min, and energy intake from a cold buffet-style meal was then quantified. Energy intake was highly reproducible within individuals between visits (intraclass correlation coefficient, ri = 0.9). Gastric emptying, intragastric meal distribution, blood glucose, plasma insulin and CCK concentrations and appetite perceptions did not differ between visits (ri>0.7 for all). In healthy males, energy intake is highly reproducible, at least in the short term, and is associated with reproducible patterns of gastric emptying, glycaemia, insulinaemia and CCK release.

Pathophysiology and management of gastroparesis

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

Effect of the artificial sweetener, sucralose, on gastric emptying and incretin hormone release in healthy subjects

The incretin hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), play an important role in glucose homeostasis in both health and diabetes. In mice, sucralose, an artificial sweetener, stimulates GLP-1 release via sweet taste receptors on enteroendocrine cells. We studied blood glucose, plasma levels of insulin, GLP-1, and GIP, and gastric emptying (by a breath test) in 7 healthy humans after intragastric infusions of 1) 50 g sucrose in water to a total volume of 500 ml (approximately 290 mosmol/l), 2) 80 mg sucralose in 500 ml normal saline (approximately 300 mosmol/l, 0.4 mM sucralose), 3) 800 mg sucralose in 500 ml normal saline (approximately 300 mosmol/l, 4 mM sucralose), and 4) 500 ml normal saline (approximately 300 mosmol/l), all labeled with 150 mg 13C-acetate. Blood glucose increased only in response to sucrose (P<0.05). GLP-1, GIP, and insulin also increased after sucrose (P=0.0001) but not after either load of sucralose or saline. Gastric emptying of sucrose was slower than that of saline (t50: 87.4+/-4.1 min vs. 74.7+/-3.2 min, P<0.005), whereas there were no differences in t50 between sucralose 0.4 mM (73.7+/-3.1 min) or 4 mM (76.7+/-3.1 min) and saline. We conclude that sucralose, delivered by intragastric infusion, does not stimulate insulin, GLP-1, or GIP release or slow gastric emptying in healthy humans.

Effect of domperidone supplementation of fescue-fed heifers on plasma and follicular fluid fatty acid composition and oocyte quality

This study continues a series of investigations evaluating fescue endotoxin exposure in beef heifer production. The objectives were to evaluate fatty acid compositions in plasma and follicular fluid, and to assess oocyte quality from cattle fed fescue diets. The ability of domperidone, a dopamine antagonist, to mitigate these variables was also assessed. Thirty heifers were divided into 3 treatment groups (n = 10/group) and administered treatment regimens for 24 d, at which time blood samples were collected. The treatment regimens were a diet with endophyte-free fescue (EF), a diet with endophyte-infected fescue (EI), or EI supplemented with daily subcutaneous injections of domperidone (0.44 mg/kg of BW; EID). Three heifers/group were administered treatments for an additional 10 d, at which time their luteal phase ovarian follicular fluid and oocytes were collected. Plasma and follicular fluid samples were analyzed to determine fatty acid concentrations. Oocytes were matured in vitro to assess quality. In addition, abattoir oocytes were cultured in plasma from treated heifers. In plasma, arachidonic acid was less (P < 0.001) in EF-fed compared with EI-fed heifers. Decreased (P < 0.05) total n-6 fatty acid concentration was observed in EF-fed compared with EI-fed heifers. Similarly, the EF-containing diets decreased (P < 0.05) concentrations of eicosapentaenoic acid and C22:5n-3 (P < 0.05) compared with EI-containing diets. Domperidone supplementation increased (P < 0.05) C18:2 cis-9, trans-11, C17:1n-7, and several C18:1 isomers compared with the diet with EI and no supplementation. No differences between fescue endophyte groups were detected in any of the fatty acid concentrations analyzed in follicular fluid from small follicles. In follicular fluid from large follicles, C18:4n-3 and C22:6n-3 concentrations were greater (P < 0.05) in EI-fed compared with EF-fed heifers. Oocytes cultured in serum (control) or plasma from EF-, EI-, or EID-fed cattle did not differ in their ability to progress to metaphase II. These observations indicate that fescue endotoxins can alter fatty acid composition and may contribute to altered physiology in heifers.

Effects of intraluminal local anesthetic on upper gastrointestinal motor, sensory, and peptide hormone responses to intraduodenal glucose

OBJECTIVE

Enterally administered glucose modifies gut sensation, diminishes hunger, and slows gastric emptying by suppressing antral motility and stimulating pyloric pressures. We aimed to clarify the mechanism of small intestinal glucose sensing.

METHODS

We studied eight healthy males twice, in random order. An antroduodenal manometry catheter was positioned with a sleeve sensor across the pylorus. Benzocaine, or vehicle alone, was given into the proximal duodenum as a bolus, followed by continuous infusion for 105 min (T=-15 to 90 min). Glucose was also infused into the proximal duodenum at 3 kcal/min for 90 min (T=0-90 min). Sensations of hunger, bloating, and nausea were assessed with visual analog questionnaires, blood was sampled at intervals, and energy intake at a buffet meal (T=90-120 min) was measured.

RESULTS

Perceptions of bloating and nausea were markedly less with benzocaine when compared with vehicle (P<0.05 for each), with no difference in hunger, or energy intake. In contrast, the suppression of antral waves and stimulation of phasic and tonic pyloric pressures, duodenal waves, and propagated duodenal wave sequences by intraduodenal glucose infusion did not differ between the 2 days. No difference in blood glucose, plasma insulin, or plasma glucagon-like peptide 1 between benzocaine and control was observed, whereas glucose-dependent insulinotropic polypeptide and cholecystokinin concentrations were slightly higher with benzocaine (P<0.05 for both).

CONCLUSION

Mucosal anesthesia ameliorates unpleasant sensations induced by enteral glucose, but does not inhibit the release of gut peptides that feed back on appetite and gastroduodenal motility.