Regulation of gastric emptying in humans by cholecystokinin

Cholecystokinin-Induced Duodenogastric Bile Reflux Increases the Severity of Indomethacin-Induced Gastric Antral Ulcers in Re-fed Mice

BACKGROUND/AIMS

We examined the involvement of cholecystokinin (CCK) in the exacerbation of indomethacin (IND)-induced gastric antral ulcers by gastroparesis caused by atropine or dopamine in mice.

METHODS

Male mice were fed for 2 h (re-feeding) following a 22-h fast. Indomethacin (IND; 10 mg/kg, s.c.) was administered after re-feeding; gastric lesions were examined 24 h after IND treatment. In another experiment, mice were fed for 2 h after a 22-h fast, after which the stomachs were removed 1.5 h after the end of the feeding period. Antral lesions, the amount of gastric contents, and the gastric luminal bile acids concentration were measured with or without the administration of the pro- and antimotility drugs CCK-octapeptide (CCK-8), atropine, dopamine, SR57227 (5-HT3 receptor agonist), apomorphine, lorglumide (CCK1 receptor antagonist), ondansetron, and haloperidol alone and in combination.

RESULTS

IND produced severe lesions only in the gastric antrum in re-fed mice. CCK-8, atropine, dopamine, SR57227 and apomorphine administered just after re-feeding increased bile reflux and worsened IND-induced antral lesions. These effects were significantly prevented by pretreatment with lorglumide. Although atropine and dopamine also increased the amount of gastric content, lorglumide had no effect on the delayed gastric emptying provoked by atropine and dopamine. Both ondansetron and haloperidol significantly inhibited the increase of bile reflux and the exacerbation of antral lesions induced by atropine and dopamine, respectively, but did not affect the effects of CCK-8.

CONCLUSIONS

These results suggest that CCK-CCK1 receptor signal increases bile reflux during gastroparesis induced by atropine and dopamine, exacerbating IND-induced antral ulcers.

Phenylalanine requirements using the direct amino acid oxidation technique, and the effects of dietary phenylalanine on food intake, gastric emptying, and macronutrient metabolism in adult cats

Despite Phe being an indispensable amino acid for cats, the minimum Phe requirement for adult cats has not been empirically defined. The objective of study 1 was to determine the minimum Phe requirement, where Tyr is in excess, in adult cats using the direct amino acid oxidation (DAAO) technique. Four adult male cats were used in an 8 × 4 Latin rectangle design. Cats were adapted to a basal diet for 7 d, top dressed with Phe to meet 140% of the adequate intake (NRC, 2006. Nutrient requirements of dogs and cats. Washington, DC: Natl. Acad. Press). Cats were randomly assigned to one of eight experimental Phe diets (0.29%, 0.34%, 0.39%, 0.44%, 0.54%, 0.64%, 0.74%, and 0.84% Phe in the diet on a dry matter [DM] basis). Following 1 d of diet adaptation, individual DAAO studies were performed. During each DAAO study, cats were placed into individual indirect calorimetry chambers, and 75% of the cat's daily meal was divided into 13 equal meals supplied with a dose of L-[1-13C]-Phe. Oxidation of L-[1-13C]-Phe (F13CO2) during isotopic steady state was determined from the enrichment of 13CO2 in breath. Competing models were applied using the NLMIXED procedure in SAS to determine the effects of dietary Phe on 13CO2. The mean population minimum requirement for Phe was estimated at 0.32% DM and the upper 95% population confidence limit at 0.59% DM on an energy density of 4,200 kcal of metabolizable energy/kg DM calculated using the modified Atwater factors. In study 2, the effects of a bolus dose of Phe (44 mg kg-1 BW) on food intake, gastric emptying (GE), and macronutrient metabolism were assessed in a crossover design with 12 male cats. For food intake, cats were given Phe 15 min before 120% of their daily food was offered and food intake was measured. Treatment, day, and their interaction were evaluated using PROC GLIMMIX in SAS. Treatment did not affect any food intake parameters (P > 0.05). For GE and macronutrient metabolism, cats were placed into individual indirect calorimetry chambers, received the same bolus dose of Phe, and 15 min later received 13C-octanoic acid (5 mg kg-1 BW) on 50% of their daily food intake. Breath samples were collected to measure 13CO2. The effect of treatment was evaluated using PROC GLIMMIX in SAS. Treatment did not affect total GE (P > 0.05), but cats receiving Phe tended to delay time to peak enrichment (0.05 < P ≤ 0.10). Overall, Phe at a bolus dose of 44 mg kg-1 BW had no effect on food intake, GE, or macronutrient metabolism. Together, these results suggest that the bolus dose of Phe used may not be sufficient to elicit a GE response, but a study with a greater number of cats and greater food intake is warranted.

Gastrointestinal Biomarkers and Their Association with Feeding in the First Five Days of Pediatric Critical Illness

OBJECTIVES

Predicting the patients' tolerance to enteral nutrition (EN) would help clinicians optimize individual nutritional intake. This study investigated the course of several gastrointestinal (GI) biomarkers and their association with EN advancement (ENA) longitudinally during pediatric intensive care unit (PICU) admission.

METHODS

This is a secondary analysis of the Early versus Late Parenteral Nutrition in the Pediatric Intensive Care Unit randomized controlled trial. EN was started early and increased gradually. The cholecystokinin (CCK), leptin, glucagon, intestinal fatty acid-binding protein 2 (I-FABP2), and citrulline plasma concentrations were measured upon PICU admission, day 3 and day 5. ENA was defined as kcal EN provided as % of predicted resting energy expenditure. The course of the biomarkers and ENA was examined in patients with samples on all time points using Friedman and Wilcoxon signed-rank tests. The association of ENA with the biomarkers was examined using a 2-part mixed-effects model with data of the complete population, adjusted for possible confounders.

RESULTS

For 172 patients, median age 8.6 years (first quartile; third quartile: 4.2; 13.4), samples were available, of which 55 had samples on all time points. The median ENA was 0 (0; 0) on admission, 14.5 (0.0; 43.8) on day 3, and 28.0 (7.6; 94.8) on day 5. During PICU stay, CCK and I-FABP2 concentrations decreased significantly, whereas glucagon concentrations increased significantly, and leptin and citrulline remained stable. None of the biomarkers was longitudinally associated with ENA.

CONCLUSIONS

Based on the current evidence, CCK, leptin, glucagon, I-FABP2, and citrulline appear to have no added value in predicting ENA in the first 5 days of pediatric critical illness.

Pancreatitis and the Risk of Developing Gastric Neuromuscular Dysfunction

INTRODUCTION

Most gastroparesis and functional dyspepsia cases (collectively, gastric neuromuscular dysfunction [GND]) remain idiopathic. It is believed that some idiopathic cases of GND may be triggered by an inflammatory insult to the gastrointestinal tract. We theorized that the profound foregut inflammation induced by pancreatitis could result in increased risk of GND.

METHODS

This was a case-control study of all patients undergoing gastric emptying scintigraphy between October 2017 and 2020 in an urban medical center with presumed GND. These were age-, sex-, and comparative health-matched to control patients with newly diagnosed microscopic colitis. Adjusted odds ratios (aORs) were calculated using conditional logistic regression.

RESULTS

Among the 650 patients with GND, 359 had gastroparesis, and 9.2% had a history of acute pancreatitis (vs 3.1% of controls). Patients with GND demonstrated increased odds of having a history of acute pancreatitis (aOR 2.27, 95% confidence interval [CI] 1.33-4.03, P = 0.004) and recurrent pancreatitis (aOR 2.08, 95% CI 1.67-3.48, P = 0.002). Median time to GND diagnosis after first acute pancreatitis episode was 1,544 days (477.5, 3,832). Patients with a history of pancreatitis-associated GND had increased mortality vs controls (aOR 3.41, 95% CI 0.96-5.48). In addition, patients with pancreatitis-associated GND had more hospitalizations vs GND alone (13.8 vs 3.7, P < 0.0001) during the study period.

DISCUSSION

This is the first study demonstrating an independent association between pancreatitis and the risk of GND, which occurred ∼4.2 years after the first episode of acute pancreatitis. Pancreatitis should therefore be regarded as a possible risk factor for developing GND with important consequences for healthcare utilization.

Cholecystokinin attenuates β-cell apoptosis in both mouse and human islets

Loss of functional pancreatic β-cell mass and increased β-cell apoptosis are fundamental to the pathophysiology of type 1 and type 2 diabetes. Pancreatic islet transplantation has the potential to cure type 1 diabetes but is often ineffective due to the death of the islet graft within the first few years after transplant. Therapeutic strategies to directly target pancreatic β-cell survival are needed to prevent and treat diabetes and to improve islet transplant outcomes. Reducing β-cell apoptosis is also a therapeutic strategy for type 2 diabetes. Cholecystokinin (CCK) is a peptide hormone typically produced in the gut after food intake, with positive effects on obesity and glucose metabolism in mouse models and human subjects. We have previously shown that pancreatic islets also produce CCK. The production of CCK within the islet promotes β-cell survival in rodent models of diabetes and aging. We demonstrate a direct effect of CCK to reduce cytokine-mediated apoptosis in a β-cell line and in isolated mouse islets in a receptor-dependent manner. However, whether CCK can protect human β-cells was previously unknown. Here, we report that CCK can also reduce cytokine-mediated apoptosis in isolated human islets and CCK treatment in vivo decreases β-cell apoptosis in human islets transplanted into the kidney capsule of diabetic NOD/SCID mice. Collectively, these data identify CCK as a novel therapy that can directly promote β-cell survival in human islets and has therapeutic potential to preserve β-cell mass in diabetes and as an adjunct therapy after transplant.

Gastrointestinal hormones and regulation of gastric emptying

PURPOSE OF REVIEW

In this review, we evaluate recent findings related to the association between gastrointestinal hormones and regulation of gastric emptying.

RECENT FINDINGS

Motilin and ghrelin, which act during fasting, promote gastric motility, whereas most of the hormones secreted after a meal inhibit gastric motility. Serotonin has different progastric or antigastric motility effects depending on the receptor subtype. Serotonin receptor agonists have been used clinically to treat dyspepsia symptoms but other hormone receptor agonists or antagonists are still under development. Glucagon-like peptide 1 agonists, which have gastric motility and appetite-suppressing effects are used as a treatment for obesity and diabetes.

SUMMARY

Gastrointestinal hormones play an important role in the regulation of gastric motility. Various drugs have been developed to treat delayed gastric emptying by targeting gastrointestinal hormones or their receptors but few have been commercialized.

2-Arachidonoyl glycerol suppresses gastric emptying via the cannabinoid receptor 1-cholecystokinin signaling pathway in mice

2-Monoacylglycerol (2-MAG) is one of the digestion products of dietary lipids. We recently demonstrated that a 2-MAG, 2-arachidonoyl glycerol (2-AG) potently stimulated cholecystokinin (CCK) secretion via cannabinoid receptor 1 (CB1) in a murine CCK-producing cell line, STC-1. CCK plays a crucial role in suppressing postprandial gastric emptying. To examine the effect of 2-AG on gastric emptying, we performed acetaminophen and phenol red recovery tests under oral or intraperitoneal administration of 2-AG in mice. Orally administered 2-AG (25 mg/kg) suppressed the gastric emptying rate in mice, as determined by the acetaminophen absorption test and phenol red recovery test. Intraperitoneal administration of a cholecystokinin A receptor antagonist (0.5 mg/kg) attenuated the gastric inhibitory emptying effect. In addition, both oral (10 mg/kg) and intraperitoneal (0.5 mg/kg) administration of a CB1 antagonist counteracted the 2-AG-induced gastric inhibitory effect. Furthermore, intraperitoneal 2-AG (25 mg/kg) suppressed gastric emptying. These results indicate that 2-AG exhibits an inhibitory effect on gastric emptying in mice, possibly mediated by stimulating both CCK secretion via CB1 expressed in CCK-producing cells and acting on CB1 expressed in the peripheral nerves. Our findings provide novel insights into the 2-MAG-sensing mechanism in enteroendocrine cells and the physiological role of 2-MAG.

Comparative Effects of Intragastric and Intraduodenal Administration of Quinine on the Plasma Glucose Response to a Mixed-Nutrient Drink in Healthy Men: Relations with Glucoregulatory Hormones and Gastric Emptying

BACKGROUND

In preclinical studies, bitter compounds, including quinine, stimulate secretion of glucoregulatory hormones [e.g., glucagon-like peptide-1 (GLP-1)] and slow gastric emptying, both key determinants of postprandial glycemia. A greater density of bitter-taste receptors has been reported in the duodenum than the stomach. Thus, intraduodenal (ID) delivery may be more effective in stimulating GI functions to lower postprandial glucose.

OBJECTIVE

We compared effects of intragastric (IG) and ID quinine [as quinine hydrochloride (QHCl)] administration on the plasma glucose response to a mixed-nutrient drink and relations with gastric emptying, plasma C-peptide (reflecting insulin secretion), and GLP-1.

METHODS

Fourteen healthy men [mean ± SD age: 25 ± 3 y; BMI (in kg/m2): 22.5 ± 0.5] received, on 4 separate occasions, in double-blind, randomly assigned order, 600 mg QHCl or control, IG or ID, 60 min (IG conditions) or 30 min (IG conditions) before a mixed-nutrient drink. Plasma glucose (primary outcome) and hormones were measured before, and for 2 h following, the drink. Gastric emptying of the drink was measured using a 13C-acetate breath test. Data were analyzed using repeated-measures 2-way ANOVAs (factors: treatment and route of administration) to evaluate effects of QHCl alone and 3-way ANOVAs (factors: treatment, route-of-administration, and time) for responses to the drink.

RESULTS

After QHCl alone, there were effects of treatment, but not route of administration, on C-peptide, GLP-1, and glucose (P < 0.05); QHCl stimulated C-peptide and GLP-1 and lowered glucose concentrations (IG control: 4.5 ± 0.1; IG-QHCl: 3.9 ± 0.1; ID-control: 4.6 ± 0.1; ID-QHCl: 4.2 ± 0.1 mmol/L) compared with control. Postdrink, there were treatment × time interactions for glucose, C-peptide, and gastric emptying, and a treatment effect for GLP-1 (all P < 0.05), but no route-of-administration effects. QHCl stimulated C-peptide and GLP-1, slowed gastric emptying, and reduced glucose (IG control: 7.2 ± 0.3; IG-QHCl: 6.2 ± 0.3; ID-control: 7.2 ± 0.3; ID-QHCl: 6.4 ± 0.4 mmol/L)  compared with control.

CONCLUSIONS

In healthy men, IG and ID quinine administration similarly lowered plasma glucose, increased plasma insulin and GLP-1, and slowed gastric emptying. These findings have potential implications for lowering blood glucose in type 2 diabetes. This study was registered as a clinical trial with the Australian New Zealand Clinical Trials at www.anzctr.org.au as ACTRN12619001269123.

Gastric Sensory and Motor Functions and Energy Intake in Health and Obesity-Therapeutic Implications

Sensory and motor functions of the stomach, including gastric emptying and accommodation, have significant effects on energy consumption and appetite. Obesity is characterized by energy imbalance; altered gastric functions, such as rapid gastric emptying and large fasting gastric volume in obesity, may result in increased food intake prior to reaching usual fullness and increased appetite. Thus, many different interventions for obesity, including different diets, anti-obesity medications, bariatric endoscopy, and surgery, alter gastric functions and gastrointestinal motility. In this review, we focus on the role of the gastric and intestinal functions in food intake, pathophysiology of obesity, and obesity management.

Effects of energy source in milk replacer on glucose metabolism of neonatal dairy calves

Milk replacers (MR) formulated to contain more lactose than whole milk could potentially reduce insulin sensitivity in dairy calves. This study evaluated how partially replacing lactose in MR with fat on a weight/weight basis affects glucose-insulin kinetics in neonatal dairy calves fed high quantities of MR. Thirty-four Holstein bull calves were blocked by dam parity (1.6 ± 0.3) and randomly assigned to 1 of 2 treatments (n = 17): a high-lactose MR (HL; 46.1% lactose, 18.0% crude fat, and 23.9% crude protein on a dry matter basis) or a high fat MR (HF; 39.9% lactose, 24.6% crude fat, and 24.0% crude protein on a dry matter basis). Calves were individually housed and fed pooled colostrum at 1.5 h and 12 h postnatal at 18 and 9% of metabolic body weight (BW0.75), respectively. From 24 h postnatal until the end of the study (d 7), calves were transitioned to MR (prepared at 150 g/L) at 18% of BW0.75 twice daily at 0700 and 1900 h. On d 4, an insulin-modified intravenous glucose tolerance test was conducted 8 h after the morning meal by intravenous infusion of glucose (0.54 g/kg of BW0.75, min 0) and insulin (3.9 µg/kg of BW0.75, min 20). During postprandial sampling on d 6, abomasal emptying was assessed by dosing acetaminophen (0.13 g/kg of BW0.75) with MR and measuring its appearance within plasma. Sequential blood samples were collected and analyzed for plasma glucose, insulin, and acetaminophen concentrations. Calves were killed on d 7 and liver and pancreatic tissues were collected for histomorphological analysis. Partially replacing lactose in MR with fat increased body weight gain (679.6 vs. 462.0 ± 69.68 g/d) and gain:metabolizable energy intake (186.6 vs. 120.5 ± 20.21 g of body weight/Mcal) compared with feeding HL MR. Furthermore, abomasal emptying rate was reduced in calves fed HF MR. Calculated variables based on postprandial glucose and insulin concentrations, such as maximum concentration or area under the curve, were or tended to be lower in HF than in HL calves. Postprandial insulin sensitivity tended to be reduced in HL compared with HF, although insulin sensitivity estimated from the insulin-modified intravenous glucose tolerance test was not different. Calves fed HF MR showed enhanced glucose-stimulated insulin secretion. In conclusion, partially replacing lactose in MR with fat resulted in smaller fluctuations in postprandial glucose and insulin concentrations and tended to increase postprandial but not fasting insulin sensitivity in neonatal dairy calves.

A comparison of the satiating properties of medium-chain triglycerides and conjugated linoleic acid in participants with healthy weight and overweight or obesity

PURPOSE

Inconsistent evidence exists for greater satiety after medium-chain triglycerides (MCT) or conjugated linoleic acid (CLA) compared to long-chain triglycerides (LCT). Furthermore, the mechanisms are poorly understood and effects in people with a healthy weight and those with overweight/obesity have not been compared. This study aimed to compare appetite responses in these groups and examine the mechanisms behind any differences.

METHODS

Fifteen participants with healthy weight (BMI: 22.7 ± 1.9 kg·m-2) and fourteen participants with overweight/obesity (BMI: 30.9 ± 3.9 kg·m-2) consumed a breakfast containing either 23.06 g vegetable oil (CON), 25.00 g MCT oil (MCT), or 6.25 g CLA and 16.80 g vegetable oil (CLA). Appetite, peptide YY (PYY), total ghrelin (TG), β-hydroxybutyrate, and gastric emptying (GE) were measured throughout. Energy intake was assessed at an ad libitum lunch and throughout the following ~ 36 h.

RESULTS

Neither MCT nor CLA decreased ad libitum intake; however MCT decreased day 1 energy intake (P = 0.031) and the 48-h period (P = 0.005) compared to CON. MCT delayed GE (P ≤ 0.01) compared to CON, whereas CLA did not. PYY and TG concentrations were not different (P = 0.743 and P = 0.188, respectively), but MCT increased β-hydroxybutyrate concentrations compared to CON (P = 0.005) and CLA (P < 0.001). β-hydroxybutyrate concentrations were higher in participants with overweight/obesity (P = 0.009).

CONCLUSION

Consumption of MCT reduces energy intake in the subsequent 48 h, whereas CLA does not. Delayed gastric emptying or increased β-hydroxybutyrate concentrations may mediate this.

Role of Amino Acids in Blood Glucose Changes in Young Adults Consuming Cereal with Milks Varying in Casein and Whey Concentrations and Their Ratio

BACKGROUND

Increasing the total protein content and reducing the casein to whey ratio in milks consumed with breakfast cereal reduce postprandial blood glucose (BG).

OBJECTIVES

We aimed to explore associations between plasma amino acids (AAs), BG, and glucoregulatory hormones.

METHODS

In this repeated-measures design, 12 healthy adults consumed cereal (58 g) and milks (250 mL) with 3.1 wt% or high 9.3 wt% protein concentrations and with casein to whey ratios of either 80:20 or 40:60. Blood was collected at 0, 30, 60, 120, 140, 170, and 200 min for measurement of the primary outcome, BG, and for the exploratory outcomes such as plasma AA, gastric emptying, insulin (INS), and glucoregulatory hormones. Measures were made prior to and after an ad libitum lunch at 120 min. Exploratory correlations were conducted to determine associations between outcomes.

RESULTS

Pre-lunch plasma AA groups [total (TAA), essential (EAA), BCAA, and nonessential (NEAA)] were higher after 9.3 wt% than 3.1 wt% milks by 12.7%, 21.4%, 20.9%, and 7.6%, respectively (P ≤ 0.05), while post-lunch AA groups were higher by 10.9%, 19.8%, 18.8%, and 6.0%, respectively (P ≤ 0.05). Except for NEAA, pre-lunch AAs were higher after 40:60 than 80:20 ratio milks by 4.5%, 8.3%, and 9.3% (P ≤ 0.05). When pooled by all treatments, pre-lunch AA groups associated negatively with BG (r/ρ ≥ -0.45, P ≤ 0.05), but post-lunch only TAA and NEAA correlated (r ≥ -0.37, P < 0.05). Pre-lunch BG was inversely associated with Leu, Ile, Lys, Met, Thr, Cys-Cys, Asn, and Gln (r/ρ ≥ -0.46, P ≤ 0.05), but post-lunch, only with Thr, Ala, and Gly (r ≥ -0.50, P ≤ 0.05). Pre-lunch associations between AA groups and INS were not found.

CONCLUSIONS

Protein concentration and the ratio of casein to whey in milks consumed at breakfast with cereal affect plasma AA concentrations and their associations with decreased BG. The decrease in BG could be explained by INS-independent mechanisms. This trial was registered at www.clinicaltrials.gov as NCT02471092.

Amino Acids in Intestinal Physiology and Health

Dietary protein digestion is an efficient process resulting in the absorption of amino acids by epithelial cells, mainly in the jejunum. Some amino acids are extensively metabolized in enterocytes supporting their high energy demand and/or production of bioactive metabolites such as glutathione or nitric oxide. In contrast, other amino acids are mainly used as building blocks for the intense protein synthesis associated with the rapid epithelium renewal and mucin production. Several amino acids have been shown to support the intestinal barrier function and the intestinal endocrine function. In addition, amino acids are metabolized by the gut microbiota that use them for their own protein synthesis and in catabolic pathways releasing in the intestinal lumen numerous metabolites such as ammonia, hydrogen sulfide, branched-chain amino acids, polyamines, phenolic and indolic compounds. Some of them (e.g. hydrogen sulfide) disrupts epithelial energy metabolism and may participate in mucosal inflammation when present in excess, while others (e.g. indole derivatives) prevent gut barrier dysfunction or regulate enteroendocrine functions. Lastly, some recent data suggest that dietary amino acids might regulate the composition of the gut microbiota, but the relevance for the intestinal health remains to be determined. In summary, amino acid utilization by epithelial cells or by intestinal bacteria appears to play a pivotal regulator role for intestinal homeostasis. Thus, adequate dietary supply of amino acids represents a key determinant of gut health and functions.

Race- and sex-specific association between alcohol consumption and hypertension in 22 cohort studies: A systematic review and meta-analysis

BACKGROUND AND AIMS

The alcohol-hypertension relation has been well documented, but whether women have protective effect or race and type of beverage consumed affect the association remain unclear. To quantify the relation between total or beverage-specific alcohol consumption and incident hypertension by considering the effect of sex and race.

METHODS AND RESULTS

Articles were identified in PubMed and Embase databases with no restriction on publication date. Pooled relative risks (RRs) and 95% confidence intervals (CIs) were calculated by random effects models. Restricted cubic splines were used to model the dose-response association. This study involved 22 articles (31 studies) and included 414,477 participants. The hypertension risk was different among liquor, wine, and beer at 5.1-10 g/d of ethanol consumption (P_{-across subgroups} = 0.002). The hypertension risk differed between men (RR: 1.14, 95% CI: 1.07, 1.20) and women (RR: 0.98, 95% CI: 0.89, 1.06) at 10 g/d (P_{-across subgroups} = 0.005). We found a linear alcohol-hypertension association among white (P-_linearity = 0.017), black people (P-_linearity = 0.035), and Asians (P-_linearity<0.001). With 10 g/d increment of consumption, the RRs for hypertension were 1.06 (95% CI: 1.04, 1.08), 1.14 (95% CI: 1.01, 1.28), and 1.06 (95% CI: 1.01, 1.10) for Asians, black, and white people, respectively.

CONCLUSION

Sex modifies the alcohol-hypertension association at low level of alcohol consumption and we did not find evidence of a protective effect of alcohol consumption among women. Black people may have higher hypertension risk than Asians and white people at the same ethanol consumption.

Effects of L-Phenylalanine on Energy Intake and Glycaemia-Impacts on Appetite Perceptions, Gastrointestinal Hormones and Gastric Emptying in Healthy Males

In humans, phenylalanine stimulates plasma cholecystokinin (CCK) and pyloric pressures, both of which are important in the regulation of energy intake and gastric emptying. Gastric emptying is a key determinant of postprandial blood glucose. We evaluated the effects of intragastric phenylalanine on appetite perceptions and subsequent energy intake, and the glycaemic response to, and gastric emptying of, a mixed-nutrient drink. The study consisted of two parts, each including 16 healthy, lean males (age: 23 ± 1 years). In each part, participants received on three separate occasions, in randomised, double-blind fashion, 5 g (Phe-5 g) or 10g ('Phe-10 g) L-phenylalanine, or control, intragastrically, 30 min before a standardised buffet-meal (part A), or a standardised mixed-nutrient drink (part B). In part A, plasma CCK and peptide-YY (PYY), and appetite perceptions, were measured at baseline, after phenylalanine alone, and following the buffet-meal, from which energy intake was assessed. In part B, plasma glucose, glucagon-like peptide-1 (GLP-1), insulin and glucagon were measured at baseline, after phenylalanine alone, and for 2 h following the drink. Gastric emptying of the drink was also measured by ¹³C-acetate breath-test. Phe-10 g, but not Phe-5 g, stimulated plasma CCK (p = 0.01) and suppressed energy intake (p = 0.012); energy intake was correlated with stimulation of CCK (r = -0.4, p = 0.027), and tended to be associated with stimulation of PYY (r = -0.31, p = 0.082). Both Phe-10 g and Phe-5 g stimulated insulin and glucagon (all p < 0.05), but not GLP-1. Phe-10 g, but not Phe-5 g, reduced overall plasma glucose (p = 0.043) and peak plasma glucose (p = 0.017) in response to the mixed-nutrient drink. Phenylalanine had no effect on gastric emptying of the drink. In conclusion, our observations indicate that the energy intake-suppressant effect of phenylalanine is related to the stimulation of CCK and PYY, while the glucoregulatory effect may be independent of stimulation of plasma GLP-1 or slowing of gastric emptying.

Appetite, the enteroendocrine system, gastrointestinal disease and obesity

The enteroendocrine system is located in the gastrointestinal (GI) tract, and makes up the largest endocrine system in the human body. Despite that, its roles and functions remain incompletely understood. Gut regulatory peptides are the main products of enteroendocrine cells, and play an integral role in the digestion and absorption of nutrients through their effect on intestinal secretions and gut motility. Several peptides, such as cholecystokinin, polypeptide YY and glucagon-like peptide-1, have traditionally been reported to suppress appetite following food intake, so-called satiety hormones. In this review, we propose that, in the healthy individual, this system to regulate appetite does not play a dominant role in normal food intake regulation, and that there is insufficient evidence to wholly link postprandial endogenous gut peptides with appetite-related behaviours. Instead, or additionally, top-down, hedonic drive and neurocognitive factors may have more of an impact on food intake. In GI disease however, supraphysiological levels of these hormones may have more of an impact on appetite regulation as well as contributing to other unpleasant abdominal symptoms, potentially as part of an innate response to injury. Further work is required to better understand the mechanisms involved in appetite control and unlock the therapeutic potential offered by the enteroendocrine system in GI disease and obesity.

Maillard Reaction Products of Stir Fried Hordei Fructus Germinatus Are Important for Its Efficacy in Treating Functional Dyspepsia

Hordei Fructus Germinatus (HFG) has been used as a traditional medicine to treat functional dyspepsia (FD) in China. Stir fried HFG (F-HFG) containing Maillard reaction products (MRPs) is used more widely than the raw HFG (R-HFG). However, the exact mechanisms in its functionality remain unclear. This article investigated the effect of R-HFG, F-HFG, and MRPs on brain-gut peptides, gut microbiota, and digestive enzymes using an FD animal mode. After administration of R-HFG, F-HFG, and MRPs, higher mRNA expression level of gastrin (GAS) and lower mRNA expression level of vasoactive intestinal peptide (VIP) were exhibited in F-HFG and MRPs rats than R-HFG rats (P < .05). Furthermore, compared with the R-HFG group, the contents of motilin (MTL) and GAS showed an upward tendency, whereas the contents of VIP and chokcystokinin (CCK) showed a downward tendency in the F-HFG group. In addition, bacterial communities in the control, F-HFG, and MRPs groups clustered closely to one another, and bacterial communities in the model and recovery groups clustered together, whereas the bacterial communities in the R-HFG group were clustered into a category. Moreover, there were no apparent differences in brain-gut peptides and gut microbiota between the F-HFG and MRPs groups. However, after the oral administration of R-HFG, F-HFG, and MRPs, the level of digestive enzyme did not show a significant change as compared with the recovery group. These results indicated that the stronger effect of F-HFG could be attributed to the MRPs produced during stir frying, and MRPs possessed the effect of regulating brain-gut peptides and gut microbiota.

Branched chain amino acids stimulate gut satiety hormone cholecystokinin secretion through activation of the umami taste receptor T1R1/T1R3 using an in vitro porcine jejunum model

Branched chain amino acids (BCAAs) are essential amino acids involved in regulation of feed intake. The function of BCAAs on the central nervous system has been extensively studied, but effects of BCAAs on secretion of gut satiety hormones and their underlying mechanisms are largely unknown. In this study, we evaluated the distribution of gut hormones and amino acid receptors in the porcine GI tract and found cholecystokinin (CCK) and taste dimeric receptor type 1 member 1/3 (T1R1/T1R3) were predominantly expressed in the jejunum and functionally interrelated. We further evaluated the effects of l-leucine, l-isoleucine, l-valine, and BCAAs on CCK and T1R1/T1R3 expression in porcine jejunum tissue. Our data demonstrated that stimulation of porcine jejunum tissue with 10 mM l-leucine, l-isoleucine or BCAAs mix (l-leucine : l-isoleucine : l-valine = 1 : 0.51 : 0.63) for 2 hours significantly increased mRNA expression and protein abundance of T1R1/T1R3 and secretion of CCK (P < 0.05). However, the l-valine treatment only increased the mRNA and protein abundance of T1R1 and T1R3 (P < 0.05), but not CCK secretion (P > 0.10). l-Leucine-, l-isoleucine- or BCAAs mix-induced CCK secretion was significantly decreased after tissues were pretreated with lactisole, a T1R1/T1R3 inhibitor (P < 0.05). Furthermore, the increased mRNA and protein abundance of T1R1/T1R3 were also largely attenuated by blocking T1R1/T1R3 with lactisole (P < 0.05). l-Leucine, l-isoleucine and BCAAs mix appeared to induce the gut satiety hormone CCK secretion through jejunal T1R1/T1R3. These results indicate over-supplementation with BCAAs in the diet might decrease food intake in swine and humans through gastrointestinal feedback.

The effect of brisk walking in the fasted versus fed state on metabolic responses, gastrointestinal function, and appetite in healthy men

OBJECTIVE

To investigate the effect of brisk walking in the fasted versus fed state on gastric emptying rate (GER), metabolic responses and appetite hormone responses.

SUBJECTS/METHODS

Twelve healthy men completed two 45 min treadmill walks, fasted (FASTED) and followed consumption of a standardised breakfast (FED). GER of a standardised lunch was subsequently measured for 2 h using the ¹³C-breath test method. Blood samples were collected at baseline, post-breakfast period, pre-exercise, immediately post exercise, pre-lunch then every 30 min following lunch for 2 h. Circulating concentrations of acylated ghrelin (GHR), glucagon-like peptide-1 (GLP-1), peptide tyrosine tyrosine (PYY), pancreatic polypeptide (PP), glucose, insulin, triglycerides, non-esterified fatty acids (NEFA) and cholesterol were measured. Subjective feelings of appetite were assessed at 15 min intervals throughout. Substrate utilisation was measured every 30 min, and continuously throughout exercise by indirect calorimetry.

RESULTS

No differences were observed for GER T_½ (FASTED 89 ± 22 vs. FED 89 ± 24 min, P = 0.868) nor T_lag (FASTED 55 ± 15 vs. FED 54 ± 14 min, P = 0.704). NEFA concentrations were higher in FASTED at pre-exercise, post exercise and 30 min post exercise (pre-lunch) (all P < 0.05) but no differences were observed for glucose, cholesterol or triglycerides. Carbohydrate oxidation was greater at all time-points during FED exercise (all P < 0.05). Minimal changes in appetite were observed post lunch ingestion with no differences in PYY or GHR observed between trials. GLP-1 concentrations were greater in FED post-breakfast and pre-exercise (P < 0.05), though no differences were observed after lunch. A greater concentration of PP was observed in FED from pre-exercise to 30 min post lunch consumption (all P < 0.05). Insulin concentrations were higher in FED pre-exercise but higher in FASTED 1.5 h post lunch (P < 0.05).

CONCLUSION

These findings suggest that gastrointestinal function, hunger and appetite regulatory hormones are not sensitive to low-intensity bouts of physical activity and holds positive implications for weight management practices.

Implication of neurohormonal-coupled mechanisms of gastric emptying and pancreatic secretory function in diabetic gastroparesis

Recently, diabetic gastroparesis (DGP) has received much attention as its prevalence is increasing in a dramatic fashion and management of patients with DGP represents a challenge in the clinical practice due to the limited therapeutic options. DGP highlights an interrelationship between the gastric emptying and pancreatic secretory function that regulate a wide range of digestive and metabolic functions, respectively. It well documented that both gastric emptying and pancreatic secretion are under delicate control by multiple neurohormonal mechanisms including extrinsic parasympathetic pathways and gastrointestinal (GI) hormones. Interestingly, the latter released in response to various determinants that related to the rate and quality of gastric emptying. Others and we have provided strong evidence that the central autonomic nuclei send a dual output (excitatory and inhibitory) to the stomach and the pancreas in response to a variety of hormonal signals from the abdominal viscera. Most of these hormones released upon gastric emptying to provide feedback, and control this process and simultaneously regulate pancreatic secretion and postprandial glycemia. These findings emphasize an important link between gastric emptying and pancreatic secretion and its role in maintaining homeostatic processes within the GI tract. The present review deals with the neurohormonal-coupled mechanisms of gastric emptying and pancreatic secretory function that implicated in DGP and this provides new insights in our understanding of the pathophysiology of DGP. This also enhances the process of identifying potential therapeutic targets to treat DGP and limit the complications of current management practices.

Co-ingestion of whole eggs or egg whites with glucose protects against postprandial hyperglycaemia-induced oxidative stress and dysregulated arginine metabolism in association with improved vascular endothelial function in prediabetic men

Replacing a portion of a glucose challenge with whole eggs (EGG) or egg whites (WHITE) was shown to protect against glucose-induced impairments in vascular function. We hypothesised in the present study that previously observed vasoprotection following co-ingestion of EGG or WHITE with glucose was attributed to limiting postprandial hyperglycaemia-induced oxidative stress that improves NO∙ bioavailability. Prediabetic men completed a randomised, cross-over study in which they ingested isoenergetic meals containing 100 g glucose (GLU), or 75 g glucose with 1·5 EGG, seven WHITE or two egg yolks (YOLK). At 30 min intervals for 3 h, we assessed plasma NO∙ metabolites, the lipid peroxidation biomarker malondialdehyde, antioxidants, arginine and its methylated metabolites (asymmetric dimethylarginine and symmetric dimethylarginine), tetrahydrobiopterin redox status, vasoconstrictors and inflammatory markers. Compared with GLU, malondialdehyde was lower and NO∙ metabolites were greater in EGG and WHITE, but YOLK was not different from GLU. Malondialdehyde was inversely correlated with NO∙ metabolites and vascular function, whereas NO∙ metabolites were positively correlated with vascular function. Compared with GLU, arginine was greater, but asymmetric and symmetric dimethylarginine and angiotensin-II were lower in all egg-based meals. Antioxidants, tetrahydrobiopterin redox status and inflammatory markers did not differ among treatments. Thus, while each egg-based meal improved arginine metabolism, only EGG and WHITE limited lipid peroxidation. This suggests that vasoprotection mediated by EGG and WHITE likely occurs in an NO∙-dependent manner by improving arginine metabolism and attenuating oxidative stress that otherwise limit NO∙ biosynthesis and bioavailability to the vascular endothelium.

The rôle of the gastrointestinal tract in the control of voluntary food intake

The short-term regulation of intake is thought to be achieved at least in part by signals from the gastrointestinal tract. Infusions of glucose, protein hydrolysate or emulsified fat into the stomach, and of glucose or protein hydrolysate into the duodenum, jejunum or ileum caused pigs to reduce their intake to compensate approximately for the energy infused, probably through the regulation of gastric emptying. Protein or protein hydrolysate infusions also caused a long-term inhibition of intake for 30 h by up to three times the energy infused. During feeding gastric emptying occurred at a constant rate of calories, the rate increasing linearly with body weight; duodenal infusion of glucose slowed gastric emptying to compensate for the infused energy and satiety occurred at a reduced food intake but at the same stomach volume. Duodenal infusion of emulsified fat caused a greater than caloric inhibition of intake, which was blocked by the cholecystokinin (CCK) antagonist L-364,718 and appeared to be mediated through a mono-glyceride-induced CCK release. Emulsified fat infused into the duodenum slowed gastric emptying by more than the energy infused and the gastric volume at satiety was decreased suggesting that the effects of fats on intake are possibly independent of gastric emptying. Since L-364,718 did not increase intake on a normal diet (186 g protein, 20 g fat per kg), CCK may only contribute to satiety in pigs eating high-fat diets.

Evaluation of a modified rat model for functional dyspepsia

BACKGROUND/AIM

The purpose of this study was to establish a modified rat model with functional dyspepsia (FD) and analyze the changes in gastrointestinal motility and brain-gut peptide levels in serum and brain-gut axis.

MATERIALS AND METHODS

Male Wistar rats were divided into control group (Con) and FD model group. FD model was established by stimulating semi-starvation rats via tail damping, provocation, and forced exercise fatigue until gastrointestinal motility disorder appeared, and then levels of motilin, leptin, cholecystokinin (CCK), and vasoactive intestinal peptide (VIP) were detected in serum by enzyme linked immunosorbent assay and in duodenum, antrum, and hypothalamus by immunohistochemistry, reverse transcriptase-polymerase chain reaction, and Western blot.

RESULTS

The results showed rates of intestinal propulsion and gastric emptying slowed down markedly compared to Con (P < 0.05), the gastrointestinal electric activity attenuated, and migrating motor complex (MMC) interrupted in the model group. The levels of leptin and VIP markedly increased, but motilin decreased as compared to the Con (P < 0.05) in serum and in the above tissues. It is interesting that the level of CCK decreased in the antrum and duodenum but increased in the hypothalamus as compared to Con (P < 0.05).

CONCLUSIONS

The modified rat model meets the diagnostic criteria of FD and can be used as a method for studying FD in animals.

Investigation of mechanisms involved in postprandial glycemia and insulinemia attenuation with dietary fibre consumption

This work examines the mechanisms involved in the attenuation of postprandial glycemic and insulinemic responses associated with soluble dietary fibre (SDF) consumption. The effect of SDF, including yellow mustard mucilage, soluble flaxseed gum and fenugreek gum on in vitro amylolysis and maltose transport was studied. Furthermore, a human clinical trial was conducted to investigate the effect of SDF consumption on postprandial glycemic and insulinemic responses and gastric emptying, as estimated based on the absorption of paracetamol. Participants (n = 15) at risk for type II diabetes consumed maltose syrup- and starch-based pudding treatments supplemented with each SDF, each at a concentration to match three times the apparent viscosity (18.54 mPa s at 60 s^-1) equivalent to the European Food Safety Authority (2011) glycemia control health claim for cereal β-glucan, measured under simulated small intestinal conditions. The presence of each SDF delayed in vitro amylolysis to a similar extent, but had no effect on maltose transport. Generally, all SDF-containing treatments attenuated blood glucose and plasma insulin peak concentrations and plasma paracetamol 1 h incremental area under the curve values to a similar extent, relative to the controls, despite differences in the amounts at which each SDF was used (from 5.9 to 15.5 g). The postprandial attenuations were related to the ability of each SDF to modify digesta viscosity, perhaps through the delay of gastric emptying, as a delay of amylolysis and sugar transport under simulated upper intestinal conditions did not seem to have a substantial effect.

The Effect of Short-Term Dietary Fructose Supplementation on Gastric Emptying Rate and Gastrointestinal Hormone Responses in Healthy Men

This study aimed to examine gastric emptying rate and gastrointestinal hormone responses to fructose and glucose ingestion following 3 days of dietary fructose supplementation. Using the ¹³C-breath test method, gastric emptying rates of equicaloric fructose and glucose solutions were measured in 10 healthy men with prior fructose supplementation (fructose supplement, FS; glucose supplement, GS) and without prior fructose supplementation (fructose control, FC; glucose control, GC). In addition, circulating concentrations of acylated ghrelin (GHR), glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and insulin were determined, as well as leptin, lactate, and triglycerides. Increased dietary fructose ingestion resulted in accelerated gastric emptying rate of a fructose solution but not a glucose solution. No differences in GIP, GLP-1, or insulin incremental area under curve (iAUC) were found between control and supplement trials for either fructose or glucose ingestion. However, a trend for lower ghrelin iAUC was observed for FS compared to FC. In addition, a trend of lower GHR concentration was observed at 45 min for FS compared to FC and GHR concentration for GS was greater than GC at 10 min. The accelerated gastric emptying rate of fructose following short-term supplementation with fructose may be partially explained by subtle changes in delayed postprandial ghrelin suppression.

Ghrelin, CCK, GLP-1, and PYY(3-36): Secretory Controls and Physiological Roles in Eating and Glycemia in Health, Obesity, and After RYGB

The efficacy of Roux-en-Y gastric-bypass (RYGB) and other bariatric surgeries in the management of obesity and type 2 diabetes mellitus and novel developments in gastrointestinal (GI) endocrinology have renewed interest in the roles of GI hormones in the control of eating, meal-related glycemia, and obesity. Here we review the nutrient-sensing mechanisms that control the secretion of four of these hormones, ghrelin, cholecystokinin (CCK), glucagon-like peptide-1 (GLP-1), and peptide tyrosine tyrosine [PYY(3-36)], and their contributions to the controls of GI motor function, food intake, and meal-related increases in glycemia in healthy-weight and obese persons, as well as in RYGB patients. Their physiological roles as classical endocrine and as locally acting signals are discussed. Gastric emptying, the detection of specific digestive products by small intestinal enteroendocrine cells, and synergistic interactions among different GI loci all contribute to the secretion of ghrelin, CCK, GLP-1, and PYY(3-36). While CCK has been fully established as an endogenous endocrine control of eating in healthy-weight persons, the roles of all four hormones in eating in obese persons and following RYGB are uncertain. Similarly, only GLP-1 clearly contributes to the endocrine control of meal-related glycemia. It is likely that local signaling is involved in these hormones' actions, but methods to determine the physiological status of local signaling effects are lacking. Further research and fresh approaches are required to better understand ghrelin, CCK, GLP-1, and PYY(3-36) physiology; their roles in obesity and bariatric surgery; and their therapeutic potentials.

The menstrual cycle influences the gastric emptying of alcohol

We previously reported that ingestion of 60 mL of red wine or vodka prior to the ingestion of a pancake significantly inhibited the gastric emptying of the pancake in male subjects, but not in female subjects, and that the retention times of wine and vodka were significantly longer than those of the congener of red wine and mineral water in male subjects, whereas in female subjects the retention times of these four drinks did not differ significantly from one another. We hypothesized that the menstrual cycle may influence the gastric emptying of alcohol beverages. Here, we determined and compared the retention times of vodka and water in the stomach during the luteal phase and the follicular phase. Ten female healthy volunteers were studied. They recorded their basal body temperatures every day, and participated in the following experiments: each volunteer drank mineral water or vodka containing 14% alcohol (60 mL) during the low-temperature (follicular) phase as well as during the high-temperature (luteal) phase. The retention time of vodka was significantly longer than that of mineral water during the follicular phase, but no significant differences between the retention times of the two drinks were observed during the luteal phase. In conclusion, the menstrual cycle influences the gastric emptying rate of alcohol.

Gut feedback mechanisms and food intake: a physiological approach to slow carbohydrate bioavailability

Glycemic carbohydrates in foods are an important macronutrient providing the biological fuel of glucose for a variety of physiological processes. A classification of glycemic carbohydrates into rapidly digestible carbohydrate (RDC) and slowly digestible carbohydrate (SDC) has been used to specify their nutritional quality related to glucose homeostasis that is essential to normal functioning of the brain and critical to life. Although there have been many studies and reviews on slowly digestible starch (SDS) and SDC, the mechanisms of their slow digestion and absorption were mostly investigated from the material side without considering the physiological processes of their in vivo digestion, absorption, and most importantly interactions with other food components and the gastrointestinal tract. In this article, the physiological processes modulating the bioavailability of carbohydrates, specifically the rate and extent of their digestion and absorption as well as the related locations, in a whole food context, will be discussed by focusing on the activities of the gastrointestinal tract including glycolytic enzymes and glucose release, sugar sensing, gut hormones, and neurohormonal negative feedback mechanisms. It is hoped that a deep understanding of these physiological processes will facilitate the development of innovative dietary approaches to achieve desired carbohydrate or glucose bioavailability for improved health.

The glycemic response to fibre rich foods and their relationship with gastric emptying and motor functions: an MRI study

The chief motor functions of human stomach, namely receiving, storing, mixing and emptying, influence the absorption of ingested food and hence determine the glycemic response to the meal.

Multifaceted interplay among mediators and regulators of intestinal glucose absorption: potential impacts on diabetes research and treatment

Glucose is the prominent molecule that characterizes diabetes and, like the vast majority of nutrients in our diet, it is absorbed and enters the bloodstream directly through the small intestine; hence, small intestine physiology impacts blood glucose levels directly. Accordingly, intestinal regulatory modulators represent a promising avenue through which diabetic blood glucose levels might be moderated clinically. Despite the critical role of small intestine in blood glucose homeostasis, most physiological diabetes research has focused on other organs, such as the pancreas, kidney, and liver. We contend that an improved understanding of intestinal regulatory mediators may be fundamental for the development of first-line preventive and therapeutic interventions in patients with diabetes and diabetes-related diseases. This review summarizes the major important intestinal regulatory mediators, discusses how they influence intestinal glucose absorption, and suggests possible candidates for future diabetes research and the development of antidiabetic therapeutic agents.

Role of the gut in modulating lipoprotein metabolism

The intestinal production of lipoproteins is one of the key processes by which the body prepares dietary lipid for dissemination to locations throughout the body where they are required. Paramount to this is the relationship between dietary lipid and the enterocytes that line the gut, along with the processes which prepare this lipid for efficient uptake by these cells. These include those which occur in the mouth and stomach along with those which occur within the intestinal lumen itself. Additionally, the interplay between digested lipid, dual avenues for lipid uptake by enterocytes (passive and lipid transporter proteins), a system of intercellular lipid resynthesis and transport, and a complex system of lipoprotein synthesis yield a system open to significant modulation. In this review, we will attempt to outline the processes of lipid digestion, lipoprotein synthesis and the exogenous and endogenous factors which exert their influence.

Specificity of infant digestive conditions: some clues for developing relevant in vitro models

Digestion of nutrients is an essential function of the newborn infant gut to allow growth and development and understanding infant digestive function is essential to optimize nutrition and oral drug delivery. Ethical considerations prohibit invasive in vivo trials and as a consequence in vitro assays are often conducted. However, the choice of in vitro model parameters are not supported by an exhaustive analysis of the literature and do not mimic precisely the digestive conditions of the infant. This review contains a compilation of the studies which characterized the gastroduodenal conditions in full-term or preterm infants of variable postnatal age from birth up to six months. Important data about healthy full-term infants are reported. The enzymatic (type of enzymes and level of activity) and nonenzymatic (milk-based diet, frequency of feeding, bile salt concentrations) conditions of digestion in infants are shown to differ significantly from those in adults. In addition, the interindividual and developmental variability of the digestive conditions in infants is also highlighted.

Disturbed release of cholecystokinin in pregnant women with hyperemesis gravidarum

AIMS

We aimed to investigate cholecystokinin (CCK) release in pregnant women with and without hyperemesis gravidarum (HG).

MATERIAL AND METHODS

In this case-control study including 40 pregnant women with HG and 40 women with healthy uncomplicated pregnancies, serum CCK levels in addition to hematological, biochemical and hormonal parameters were investigated.

RESULTS

Serum CCK values were found to be significantly lower in pregnant women with HG (P < 0.001). Additionally, while serum blood urea nitrogen and free thyroxine levels were significantly higher, sodium, potassium, and thyroid stimulating hormone levels were significantly lower in women with HG than in control women. No correlation was detected between CCK and other parameters like ketonuria and thyroid function tests.

CONCLUSIONS

CCK release has been found to be halved in pregnant women with HG, which supports the hypothesis that gastrointestinal motility is increased in pregnant women with HG. A causal effect remains to be confirmed.

Activation of the gut calcium-sensing receptor by peptide agonists reduces rapid elevation of plasma glucose in response to oral glucose load in rats

The calcium-sensing receptor (CaSR) is expressed in various tissues, including the gastrointestinal tract. To investigate the role of gut CaSR on glycemic control, we examined whether single oral administration of CaSR agonist peptides affected the glycemic response in rats. Glucose tolerance tests were performed under oral or duodenal administration of various CaSR agonist peptides (γGlu-Cys, protamine, and poly-d-lysine hydrobromide) in conscious rats. Involvement of CaSR was determined by using a CaSR antagonist. Signaling pathways underlying CaSR agonist-modified glycemia were investigated using gut hormone receptor antagonists. The gastric emptying rate after the administration of CaSR agonist peptides was measured by the phenol red recovery method. Oral and duodenal administration of CaSR agonist peptides attenuated glycemic responses under the oral glucose tolerance test, but the administration of casein did not. The promotive effect on glucose tolerance was weakened by luminal pretreatment with a CaSR antagonist. Treatment with a 5-HT3 receptor antagonist partially diminished the glucose-lowering effect of peptides. Furthermore, the gastric emptying rate was decreased by duodenal administration of CaSR agonist peptides. These results demonstrate that activation of the gut CaSR by peptide agonists promotes glucose tolerance in conscious rats. 5-HT3 receptor and the delayed gastric emptying rate appear to be involved in the glucose-lowering effect of CaSR agonist peptides. Thus, activation of gut CaSR by dietary peptides reduces glycemic responses so that gut CaSR may be a potential target for the improvement of postprandial glycemia.

A new flexible plug and play scheme for modeling, simulating, and predicting gastric emptying

BACKGROUND

In-silico models that attempt to capture and describe the physiological behavior of biological organisms, including humans, are intrinsically complex and time consuming to build and simulate in a computing environment. The level of detail of description incorporated in the model depends on the knowledge of the system's behavior at that level. This knowledge is gathered from the literature and/or improved by knowledge obtained from new experiments. Thus model development is an iterative developmental procedure. The objective of this paper is to describe a new plug and play scheme that offers increased flexibility and ease-of-use for modeling and simulating physiological behavior of biological organisms.

METHODS

This scheme requires the modeler (user) first to supply the structure of the interacting components and experimental data in a tabular format. The behavior of the components described in a mathematical form, also provided by the modeler, is externally linked during simulation. The advantage of the plug and play scheme for modeling is that it requires less programming effort and can be quickly adapted to newer modeling requirements while also paving the way for dynamic model building.

RESULTS

As an illustration, the paper models the dynamics of gastric emptying behavior experienced by humans. The flexibility to adapt the model to predict the gastric emptying behavior under varying types of nutrient infusion in the intestine (ileum) is demonstrated. The predictions were verified with a human intervention study. The error in predicting the half emptying time was found to be less than 6%.

CONCLUSIONS

A new plug-and-play scheme for biological systems modeling was developed that allows changes to the modeled structure and behavior with reduced programming effort, by abstracting the biological system into a network of smaller sub-systems with independent behavior. In the new scheme, the modeling and simulation becomes an automatic machine readable and executable task.

Intra-gastric triacetin alters upper gastrointestinal motility in conscious dogs

AIM: To examine the effect of intra-gastric triacetin on both upper gastrointestinal motility and proximal gastric tone in conscious dogs.

METHODS: Three beagle dogs under sedation were surgically implanted with gastrocutaneous fistula in the gastric body and force transducers in the gastric antrum and duodenum. Beginning at week-2 after insertion, the animals were either fasted for 24 h or fed a liquid meal 2-3 h before the experiment. With the animals fully conscious, a polyethylene bag was inserted into the proximal stomach through the gastrocutaneous fistula, followed by 15 min of air inflation (minimal distending pressure of ＋2 mmHg) and then 20 mL of a low-, mid- or high-concentration triacetin solution (0.5%, 1.0% and 2.0%) or warm water (vehicle control). The proximal stomach receptive volume and gastric antral and duodenal contractions were measured over 10 min. The experiment was repeated twice per week over several months, with each animal receiving at least one infusion of the various triacetin solutions and the vehicle at different times. Intergroup differences were assessed by ANOVA and Bonferroni-Dunn post-hoc testing.

RESULTS: Intra-gastric infusion of mid- and high-concentration triacetin induced an increase in the proximal stomach receptive volume, and the average increase induced by the high-concentration at 0-4 min after infusion was significantly greater than that induced by the vehicle control (62.4 ± 9.8 vs 18.4 ± 4.7, P < 0.01). The mid- and high-concentration triacetin also produced a temporary inhibition of the gastric antral contractions at 2 min after infusions; however, only the fasted group showed triacetin-induced antral contractile inhibition that was significantly greater than that in the vehicle control group (P < 0.05). In addition, only the fasted group showed a high-concentration triacetin-induced increase in duodenal contractions at 9-10 min that was significantly different from that in the vehicle control group (P < 0.05).

CONCLUSION: Intra-gastric infusion of 1.0%-2.0% triacetin delays gastric emptying by increasing proximal stomach receptive volume, temporarily inhibiting gastric antral contractions and facilitating duodenal contractions.

Enteroendocrine cells in gastrointestinal pathophysiology

Enteroendocrine cells in the gastrointestinal tract play an important role in the regulation of appetite and digestive responses through the secretion of peptides. Their involvement in gastrointestinal diseases has been acknowledged, but relatively few studies have sought to clearly define their role in the pathogenesis or as therapeutic targets. Recent, but still limited, work has identified new roles for EEC in GI diseases.

Specific food structures supress appetite through reduced gastric emptying rate

The aim of this study was to determine the extent to which gastric layering and retention of a meal could be used to reduce appetite using the same caloric load. Liquid (control) and semi-solid (active) meals were produced with the same protein, fat, carbohydrate, and mass. These were fed to 10 volunteers on separate days in a crossover study, and subjective appetite ratings, gastric contents, and plasma cholecystokinin (CCK) were assessed over a period of 3 h. The active meal showed food boluses in the stomach persisting for ~45 min, slower emptying rates, and lower plasma CCK levels over the first hour. After the first hour, both gastric emptying rates and plasma CCK levels were similar for both systems and slightly increased compared with the unfed situation. Despite the lower plasma CCK levels for the active meal over the first hour, this meal reduced appetite more than the control meal over the 3 h of the study. For a moderately increased plasma CCK level in the fed state, appetite was correlated with the volume of gastric contents rather than gastric emptying rates or plasma CCK. This suggests that enhanced gastric retention was the key factor in decreasing appetite and was probably mediated by a combination of intestinal nutrient sensing and increased viscosity in the stomach.

Gastric secretion does not affect the reliability of the 13C-acetate breath test: A validation of the 13C-acetate breath test by magnetic resonance imaging

BACKGROUND

(13)C-Acetate labeled meals are widely used to determine meal emptying by means of analyzing resulting (13)CO(2) exhalation dynamics. In contrast to the underlying metabolic processes, only few (13)C breath test meal emptying studies have focused on intragastric processes that may alter (13)CO(2) exhalation. This work assessed the effect of enhanced gastric secretion on the reliability of half emptying time (t50) measurements by (13)C-acetate breath test.

METHODS

(13)CO(2) exhalation data were acquired in a double-blind, randomized, cross-over gastric emptying study in 12 healthy volunteers receiving either pentagastrin or placebo intravenously. The standard method proposed by Ghoos et al. was applied to calculate t50 (t50_Ghoos) from (13)CO(2) exhalation data, which were compared and tested for agreement to meal half emptying times (t50_MV) from concurrent recorded MRI (magnetic resonance imaging) volume data. In addition, the accumulated gastric secretion volumes during infusion as detected by MRI (AUC_SV(60)) were correlated with the corresponding cumulative percent (13)C doses recovered (cPDR(60)).

KEY RESULTS

t50_Ghoos and t50_MV showed a linear correlation with a slope of 1.1 ± 0.3 (r(2) = 0.67), however, a positive offset of 136 min for t50_Ghoos. No correlation was detected between AUC_SV(60) and cPDR(60) (r(2) = 0.11). Both, breath test and MRI, revealed a prolonged t50 under pentagastrin infusion with median differences in t50_Ghoos of 45[28-84] min (P = 0.002) and t50_MV of 39[28-52] min (P = 0.002).

CONCLUSIONS & INFERENCES

This study suggests that (13)CO(2) exhalation after ingestion of a (13) C-labeled liquid test meal is not affected by stimulated gastric secretion, but is rather reflecting the dynamics of meal or caloric emptying from the stomach.

Axon-like basal processes in enteroendocrine cells: characteristics and potential targets

Enteroendocrine cells (EECs) play a key role in nutrient digestion and absorption, and are essential for normal life. Recently, EEC function has received considerable attention because several gastrointestinal hormones modulate insulin secretion and food intake; and, gut hormone-based therapies have been developed to treat diabetes mellitus. Despite these advances, the regulation of EECs remains poorly understood. The development of transgenic mouse models that express green fluorescent proteins (GFP) under specific hormone promoters (e.g., peptide YY-GFP) is shedding light onto previously overlooked features of EECs. These cells have prominent cytoplasmic processes that extend underneath enterocytes, and in some EECs, such as the L cell of the distal ileum, the basal process can be over 50 μm long. These basal cytoplasmic processes resemble axons and end in synaptic-like bouton. The location and anatomy of these processes suggest two functions: (1) to monitor absorbed nutrients at the base of enterocytes; and (2) to convey electrochemical information through cell-cell connections with subepithelial myofibroblasts and/or nerves located directly beneath in the lamina propria. Understanding how EECs communicate with cells in the lamina propria may provide novel ways to treat metabolic disorders such as obesity and diabetes.