Gastric sensorimotor functions and hormone profile in normal weight, overweight, and obese people

Precision medicine for obesity: current evidence and insights for personalization of obesity pharmacotherapy

Obesity is a chronic and complex disease associated with increased morbidity, mortality, and financial burden. It is expected that by 2030 one of two people in the United States will have obesity. The backbone for obesity management continues to be lifestyle interventions, consisting of calorie deficit diets and increased physical activity levels, however, these interventions are often insufficient to achieve sufficient and maintained weight loss. As a result, multiple patients require additional interventions such as antiobesity medications or bariatric interventions in order to achieve clinically significant weight loss and improvement or resolution of obesity-associated comorbidities. Despite the recent advances in the field of obesity pharmacotherapy that have resulted in never-before-seen weight loss outcomes, comorbidity improvement, and even reduction in cardiovascular mortality, there is still a significant interindividual variability in terms of response to antiobesity medications, with a subset of patients not achieving a clinically significant weight loss. Currently, the trial-and-error paradigm for the selection of antiobesity medications results in increased costs and risks for developing side effects, while also reduces engagement in weight management programs for patients with obesity. The implementation of a precision medicine framework to the selection of antiobesity medications might help reduce heterogeneity and optimize weight loss outcomes by identifying unique subsets of patients, or phenotypes, that have a better response to a specific intervention. The detailed study of energy balance regulation holds promise, as actionable behavioral and physiologic traits could help guide antiobesity medication selection based on previous mechanistic studies. Moreover, the rapid advances in genotyping, multi-omics, and big data analysis might hold the key to discover additional signatures or phenotypes that might respond better to a certain intervention and might permit the widespread adoption of a precision medicine approach for obesity management.

Understanding the gastrointestinal tract in obesity: From gut motility patterns to enzyme secretion

BACKGROUND AND PURPOSE

The pathophysiology of obesity has been the product of extensive research, revealing multiple interconnected mechanisms contributing to body weight regulation. The regulation of energy balance involves an intricate network, including the gut-neuroendocrine interplay. As a consequence, research on the gut-brain-microbiota axis in obesity has grown extensively. The physiology of the gastrointestinal tract, far from being underexplored, has significant implications for the development of specific complications in people living with obesity across the fields of gastroenterology, nutrition, and pharmacology. Clinical research indicates higher fasting bile acids serum levels, and blunted postprandial increases in bilious secretions in people living with obesity. Findings are less straightforward for the impact of obesity on gastric emptying with various studies reporting accelerated, normal, or delayed gastric emptying rates. Conversely, the effect of obesity on gastrointestinal pH, gastrointestinal transit, and gastric and pancreatic enzyme secretion is largely unknown. In this review, we explore the current evidence on the gastrointestinal physiology of obesity.

Gastric emptying times of obese and non-obese school-aged children after preoperative clear fluid intake: A prospective observational study

BACKGROUND

Liberal fasting regimens, which support clear fluid intake up to 1 h before surgery in children scheduled for elective surgery, are taking their place in guidelines. However, because of the lack of publications that investigate the gastric emptying time in preoperative obese children, the practice of 1-hour clear fluid fasting in obese children remained at the level of recommendation with weak evidence.

AIMS

The primary aim was to investigate whether there is a difference in gastric emptying times between obese and non- obese children after preoperative intake of 3 mL/kg clear liquid containing 5% dextrose by using ultrasound.

METHODS

A total of 70 children were included in the study in two groups, 35 obese and 35 non-obese, aged 6-14 years, who were scheduled for elective surgery. The baseline antral cross-sectional area measurements of the children in the groups were made using ultrasound. 3 mL/kg 5% dextrose was consumed. Ultrasound was repeated immediately after fluid intake and every 5 min until the antral cross-sectional area was at the baseline level.

RESULTS

The difference in median (IQR [range]) gastric emptying times (minutes) of non-obese {35 [30.0-45.0 (20-60)]} and obese children {35 [30.0-40.0 (25-60)]} were not statistically significant (median of differences 0.0, 95% CI -5.0 to 5.0; p = .563). The antral cross-sectional area and weight-adjusted gastric volumes returned to the baseline level within 60 min after the intake of clear liquid with 3 mL/kg 5% dextrose in all children in both groups.

CONCLUSIONS

Obese and non-obese children have similar gastric emptying times, and these groups can be offered clear fluids containing 3 mL/kg 5% dextrose 1 h before the surgery.

Differences in gastrointestinal hormones and appetite ratings between individuals with and without obesity-A systematic review and meta-analysis

Determining if gastrointestinal (GI) hormone response to food intake differs between individuals with, and without, obesity may improve our understanding of obesity pathophysiology. A systematic review and meta-analysis of studies assessing the concentrations of GI hormones, as well as appetite ratings, following a test meal, in individuals with and without obesity was undertaken. Systematic searches were conducted in the databases MEDLINE, Embase, Cochrane Library, PsycINFO, Web of Science, and ClinicalTrials.gov. A total of 7514 unique articles were retrieved, 115 included in the systematic review, and 70 in the meta-analysis. The meta-analysis compared estimated standardized mean difference in GI hormones' concentration, as well as appetite ratings, between individuals with and without obesity. Basal and postprandial total ghrelin concentrations were lower in individuals with obesity compared with controls, and this was reflected by lower postprandial hunger ratings in the former. Individuals with obesity had a lower postprandial concentration of total peptide YY compared with controls, but no significant differences were found for glucagon-like peptide 1, cholecystokinin, or other appetite ratings. A large methodological and statistical heterogeneity among studies was found. More comprehensive studies are needed to understand if the differences observed are a cause or a consequence of obesity.

Clinical trial: a single-centre, randomised, controlled trial of tradipitant on satiation, gastric functions, and serum drug levels in healthy volunteers

BACKGROUND

Tradipitant, an NK1 receptor antagonist, improved symptoms in patients with gastroparesis. It is unclear whether these effects are mediated centrally (e.g., vomiting centre) or on gastric functions. As a class, NK1 antagonists may retard gastric emptying (GE) or increase fasting and postprandial gastric volumes (GV).

AIM

To evaluate the effects of tradipitant relative to placebo on gastric motor functions, satiation, postprandial symptoms, and pharmacokinetics.

METHODS

We conducted a randomised, double-blind, placebo-controlled, single-centre study of tradipitant 85 mg or matching placebo b.i.d. for 9 consecutive days in 24 healthy volunteers. During the last 2 days of treatment, participants underwent scintigraphic measurements of GE of 320 kcal egg meal, fasting and postprandial GV by SPECT, and satiation by nutrient drink ingested to maximum tolerated volume (MTV) and symptoms 30 min later. Treatments were compared by Wilcoxon rank sum test. The study had 80% power to detect group differences of 23.6% in GV and 29.2% in GE T_1/2 .

RESULTS

The two groups of healthy participants were well balanced based on demographic features, age, and BMI. There were nonsignificant positive correlations between blood levels of tradipitant and accommodation GV and GE at 4 h. There were no significant effects of tradipitant, 85 mg b.i.d. for 9 days compared to placebo on GE, GV, satiation, or symptoms 30 min after MTV.

CONCLUSION

Tradipitant, 85 mg b.i.d., does not significantly affect gastric motor functions (GV or GE). Importantly, there was no retardation of GE by tradipitant, which is important in relation to its potential use in patients with gastroparesis.

CLINIC TRIALS REGISTRY

ClinicalTrials.gov #NCT04849559.

Correlation Between Preoperative Gastric Volume and Weight Loss After Laparoscopic Sleeve Gastrectomy

Purpose

Long-term studies reported inadequate weight loss or weight regain after laparoscopic sleeve gastrectomy (LSG). This study investigated a possible relationship between preoperative gastric volume (GV) measured by CT volumetry and weight loss one year after LSG.

Methods

This prospective study included 120 patients scheduled for LSG. 3D CT gastric volumetry was done before surgery. The weight loss in the first year was serially recorded. The primary outcome measure was the correlation between preoperative GV and postoperative weight loss after one year. The secondary outcomes were the correlation between preoperative GV and other patients’ characteristics as age and body mass index (BMI).

Results

Weight and BMI decreased significantly up to 12 months. The percentage of excess weight loss (%EWL) at 6 and 12 months was significantly higher than at three months. Preoperative GV was 1021 ± 253, ranging from 397 to 1543 mL. GV was not related to sex, age, weight, height, postoperative weight, and BMI.

Conclusion

Preoperative gastric volume cannot predict weight loss one year after LSG. It is not correlated with age, sex, or preoperative weight, and BMI.

Pooled Analysis of Gastric Emptying in Patients With Obesity: Implications for Oral Absorption Projection

PURPOSE

Gastric emptying time is one of limiting factors that determines the pharmacokinetic properties of drugs administered by mouth. Despite the high prevalence of obesity worldwide, modifications in gastric emptying time have not been systematically addressed in this set of patients. The current analysis aims to quantitatively address obesity-related changes in gastric emptying time of solids, semisolids, and liquids compared with lean individuals, highlighting the relevant pharmacokinetic implications of oral drug absorption in patients with obesity.

METHODS

We searched the Cochrane Library, PubMed, Web of Science, and Embase for all relevant articles published until November 1, 2020. Differences in gastrointestinal variables in relation to gastric emptying between obese and lean individuals were quantified by weighted mean difference (WMD) and ratio of means (RoM). Robustness of the analyses was evaluated by subgroup analysis and publication bias test.

FINDINGS

A total of 17 studies with 906 participants were included. The gastric half-emptying time of solids (WMD, -10.4 minutes; P = 0.001; RoM, 0.90; P = 0.01) and liquids (WMD, -6.14 minutes; P < 0.001; RoM, 0.83, P = 0.03) was significantly shorter in individuals with obesity compared with lean individuals. These findings were confirmed by the subgroup analyses and publication bias tests.

IMPLICATIONS

Our pooled analysis systemically quantifies the differences in gastric half-emptying time between individuals with obesity and lean individuals, facilitating better understanding and prediction of drug absorption in individuals with obesity through physiologically based pharmacokinetic approaches. Obesity is associated with a faster transit of both solids and liquids through the stomach.

Gastrointestinal peptides in eating-related disorders

Food intake is tightly controlled by homeostatic signals sensitive to metabolic need for the regulation of body weight. This review focuses on the peripherally-secreted gastrointestinal peptides (i.e., ghrelin, cholecystokinin, glucagon-like peptide 1, and peptide tyrosine tyrosine) that contribute to the control of appetite and discusses how these peptides or the signals arising from their release are disrupted in eating-related disorders across the weight spectrum, namely anorexia nervosa, bulimia nervosa, and obesity, and whether they are normalized following weight restoration or weight loss treatment. Further, the role of gut peptides in the pathogenesis and treatment response in human weight conditions as identified by rodent models are discussed. Lastly, we review the incretin- and hormone-based pharmacotherapies available for the treatment of obesity and eating-related disorders.

Association of gastric emptying with postprandial appetite and satiety sensations in obesity

OBJECTIVE

Satiety, defined as the duration of the sensation of fullness, is usually measured by validated visual analog scales (VAS) for appetite. Gastric function plays a key role in food intake regulation. However, the association between gastric emptying (GE) and VAS appetite is unknown.

METHODS

In this cross-sectional study, 134 participants (mean [SEM] age = 39 [0.8] years, mean [SEM] BMI = 38 [0.5] kg/m² , 67% females) completed simultaneous measurements of GE and VAS appetite. After a 320-kcal meal, GE was measured by scintigraphy and appetite by validated 100-mm VAS for 240 minutes. Satiation was defined as calories consumed to terminate meal and was measured by an ad libitum meal. GE, VAS, and ad libitum meal tests were measured on the same day. Percent of meal retention in the stomach, VAS area under curve (AUC_{0-240 min} ), and overall appetite score (OAS) were calculated. Pearson correlation (ρ) determined the association of GE with VAS appetite and satiation. Appetite components were also analyzed by quartiles based on GE_{120 min} .

RESULTS

GE_{120 min} was correlated with sensation of VAS hunger_{AUC(0-240 min)} (ρ = 0.24, p = 0.004), fullness_{AUC(0-240 min)} (ρ = 0.16, p = 0.05), and OAS_{AUC(0-240 min)} (ρ = 0.20, p = 0.02). Patients with rapid GE_{120 min} had a mean increase in VAS hunger_{AUC(0-240 min)} by 32 mm/min (15.62%, p = 0.03) compared with normal/slow GE_{120 min} .

CONCLUSIONS

GE is associated with the sensations of appetite, and rapid GE is associated with increased appetite, which may contribute to weight gain.

Effect of obesity on gastrointestinal transit, pressure and pH using a wireless motility capsule

BACKGROUND

Despite the increasing prevalence and medical burden of obesity, the understanding of gastrointestinal physiology in obesity is scarce, which hampers drug development.

AIM

To investigate the effect of obesity and food intake on gastrointestinal transit, pressure and pH.

MATERIAL AND METHODS

An exploratory cross-sectional study using a wireless motility capsule (SmartPill©) was performed in 11 participants with obesity and 11 age- and gender-matched participants with normal weight (group) in fasted and fed state (visit). During the first visit, the capsule was ingested after an overnight fast. During a second visit, the capsule was ingested after a nutritional drink to simulate fed state. Linear mixed models were constructed to compare segmental gastrointestinal transit, pressure and pH between groups (obesity or control) and within every group (fasted or fed).

RESULTS

Food intake slowed gastric emptying in both groups (both P < 0.0001), though food-induced gastric contractility was higher in participants with obesity compared to controls (P = 0.02). In the small intestine, a higher contractility (P = 0.001), shorter transit (P = 0.04) and lower median pH (P = 0.002) was observed in participants with obesity compared to controls. No differences were observed for colonic measurements.

CONCLUSION

Obesity has a profound impact on gastrointestinal physiology, which should be taken into account for drug development.

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.

Neuroendocrine Peptides of the Gut and Their Role in the Regulation of Food Intake

The regulation of food intake encompasses complex interplays between the gut and the brain. Among them, the gastrointestinal tract releases different peptides that communicate the metabolic state to specific nuclei in the hindbrain and the hypothalamus. The present overview gives emphasis on seven peptides that are produced by and secreted from specialized enteroendocrine cells along the gastrointestinal tract in relation with the nutritional status. These established modulators of feeding are ghrelin and nesfatin-1 secreted from gastric X/A-like cells, cholecystokinin (CCK) secreted from duodenal I-cells, glucagon-like peptide 1 (GLP-1), oxyntomodulin, and peptide YY (PYY) secreted from intestinal L-cells and uroguanylin (UGN) released from enterochromaffin (EC) cells. © 2021 American Physiological Society. Compr Physiol 11:1679-1730, 2021.

Gastrointestinal pH, Motility Patterns, and Transit Times After Roux-en-Y Gastric Bypass

BACKGROUND

Studies investigating the underlying pathophysiology are needed to help explain and understand the postoperative complications following Roux-en-Y gastric bypass (RYGB) surgery. This study aimed to characterize segmental gastrointestinal pH profiles, motility measures, and transit times in patients with RYGB.

MATERIALS AND METHODS

Nineteen patients with RYGB underwent a standardized wireless motility capsule assessment. The oro-cecal segment was defined from capsule ingestion until the passage of the ileocecal junction. Segmental median pH, motility index, and transit time were determined for the oro-cecal and colonic segment as well as for the first and last hour of both these segments. For comparison to reference values, data from 17 healthy age- and gender-matched controls was used. A mixed effect model was used to describe differences between groups.

RESULTS

Median pH was high in patients with RYGB during the first hour of the oro-cecal segment (6.45 ± 0.4 vs 3.65 ± 1.55 pH units for healthy controls; P < 0.001), as well as during the entire oro-cecal segment (6.97 ± 0.4 vs 5.51 ± 1.1 pH units; P < 0.001). The same was evident for the median motility index (152 ± 64 vs 35.8 ± 31.1 mmHg*sec/min; P < 0.001 and 130 ± 65.9 vs 89.1 ± 20 mmHg*sec/min; P < 0.012, respectively). Median motility index was low the first hour of the colon (55.2 ± 45.7 vs 122 ± 77.9 mmHg*sec/min; P < 0.002). Additionally, patients had short oro-cecal transit time (5.8 ± 1.6 vs 7.6 ± 1.4 h; P < 0.001) and long colonic transit time (29.4 ± 17.5 vs 19.6 ± 12.2 h; P = 0.048).

CONCLUSIONS

In patients with RYGB, the oro-cecal segment was characterized by an alkaline intraluminal environment, high motility activity, and short transit time. In contrast, colonic transit time was long.

Neuropeptide Y and Peptide YY in Association with Depressive Symptoms and Eating Behaviours in Adolescents across the Weight Spectrum: From Anorexia Nervosa to Obesity

Neuropeptide Y (NPY) and peptide YY (PYY) are involved in metabolic regulation. The purpose of the study was to assess the serum levels of NPY and PYY in adolescents with anorexia nervosa (AN) or obesity (OB), as well as in a healthy control group (CG). The effects of potential confounders on their concentrations were also analysed. Eighty-nine adolescents were included in this study (AN = 30, OB = 30, and CG = 29). Anthropometric measurements and psychometric assessment of depressive symptoms, eating behaviours, body attitudes, and fasting serum levels of NPY and PYY were analysed. The AN group presented severe depressive symptoms, while the OB group held different attitudes towards the body. The levels of NPY were lower in the AN and OB groups as compared with the CG. The PYY levels were higher in the OB group than in the AN group and the CG. The severity of eating disorder symptoms predicted fasting serum concentrations of NPY. Lower levels of NPY in AN, as well as in OB suggests the need to look for a common link in the mechanism of this effect. Higher level of PYY in OB may be important in explaining complex etiopathogenesis of the disease. The psychopathological symptoms may have an influence on the neurohormones regulating metabolism.

Appetite Control across the Lifecourse: The Acute Impact of Breakfast Drink Quantity and Protein Content. The Full4Health Project

Understanding the mechanisms of hunger, satiety and how nutrients affect appetite control is important for successful weight management across the lifecourse. The primary aim of this study was to describe acute appetite control across the lifecourse, comparing age groups (children, adolescents, adults, elderly), weight categories, genders and European sites (Scotland and Greece). Participants (n = 391) consumed four test drinks, varying in composition (15% (normal protein, NP) and 30% (high protein, HP) of energy from protein) and quantity (based on 100% basal metabolic rate (BMR) and 140% BMR), on four separate days in a double-blind randomized controlled study. Ad libitum energy intake (EI), subjective appetite and biomarkers of appetite and metabolism (adults and elderly only) were measured. The adults' appetite was significantly greater than that of the elderly across all drink types (p < 0.004) and in response to drink quantities (p < 0.001). There were no significant differences in EI between age groups, weight categories, genders or sites. Concentrations of glucagon-like peptide 1 (GLP-1) and peptide YY (PYY) were significantly greater in the elderly than the adults (p < 0.001). Ghrelin and fasting leptin concentrations differed significantly between weight categories, genders and sites (p < 0.05), while GLP-1 and PYY concentrations differed significantly between genders only (p < 0.05). Compared to NP drinks, HP drinks significantly increased postprandial GLP-1 and PYY (p < 0.001). Advanced age was concomitant with reduced appetite and elevated anorectic hormone release, which may contribute to the development of malnutrition. In addition, appetite hormone concentrations differed between weight categories, genders and geographical locations.

Physical activity is associated with accelerated gastric emptying and increased ghrelin in obesity

BACKGROUND

Rapid gastric emptying, increased food intake, and alterations in gastrointestinal hormones are associated with obesity. The effect of regular physical activity (PA) on food intake, gastric emptying (GE), gastric accommodation, and gastrointestinal (GI) hormones in adults with obesity remains unclear. Our aim was to compare, at time of presentation, weight trends, eating behavior, GE, and GI hormone levels among individuals with obesity who engage in regular PA compared to those who do not.

METHODS

In 270 participants with obesity, we performed validated measurements of GI phenotypes: GE of solids and liquids, gastric volume (GV) during fasting and after consumption of 200 mL Ensure®, satiety by kcal intake (T-kcal) during a buffet meal, satiation (volume to fullness [VTF] and maximal tolerated volume [MTV]) of a liquid nutrient, and plasma levels of fasting and postprandial GLP-1, PYY, CCK, and ghrelin. Physical Activity Stages of Change Questionnaire was used to assess whether participants were regularly PA or not.

KEY RESULTS

PA was associated with lower BMI (Δ 2.01 kg/m2 , P = .001) and body weight (Δ 4.42 kg, P = .0278). GE of solids (T-50% Δ 7.54 min, P = .021) and liquids (T-50% Δ 2.99 min, P = .029%) was significantly more rapid in physically active participants. PA was also associated with relatively higher postprandial ghrelin AUC (Δ 10.4 pg/mL, P = .015). There was no significant difference in postprandial satiation, satiety, GV, or other GI hormones (CCK, PYY, or GLP-1) between groups.

CONCLUSIONS & INFERENCES

Physical activity is associated with lower BMI, but faster GE and higher postprandial ghrelin levels, two factors that are also associated with obesity.

Revisiting the Compensatory Theory as an explanatory model for relapse in obesity management

Weight regain remains the main challenge in obesity management, and its etiology remains elusive. The aim of the present review was to revise the available evidence regarding the "Compensatory Theory," which is an explanatory model of relapse in obesity treatment, and to propose alternative mechanisms that can contribute to weight regain. It has been proposed, and generally accepted as true, that when a person loses weight the body fights back, with physiological adaptations on both sides of the energy balance equation that try to bring body weight back to its original state: this is the Compensatory Theory. This theory proposes that the increased orexigenic drive to eat and the reduced energy expenditure that follow weight loss are the main drivers of relapse. However, evidence showing a link between these physiological adaptations to weight loss and weight regain is lacking. Here, we propose that the physiological adaptations to weight loss, both at the level of the homeostatic appetite control system and energy expenditure, are in fact a normalization to a lower body weight and not drivers of weight regain. In light of this we explore other potential mechanisms, both physiological and behavioral, that can contribute to the high incidence of relapse in obesity management. More research is needed to clearly ascertain whether the changes in energy expenditure and homeostatic appetite markers seen in reduced-obese individuals are a compensatory mechanism that drives relapse or a normalization towards a lower body weight, and to explore alternative hypotheses that explain relapse in obesity management.

Changes in the Homeostatic Appetite System After Weight Loss Reflect a Normalization Toward a Lower Body Weight

OBJECTIVE

To compare appetite markers in reduced-obese individuals with a nonobese control group.

METHODS

A total of 34 adults with obesity who lost 17% body weight at week 13 and maintained this weight loss (WL) at 1 year were compared with 33 nonobese controls matched for body composition. Basal and postprandial subjective appetite ratings and appetite-related hormone concentrations (ghrelin, total peptide YY, peptide YY3-36, total and active glucagon-like peptide 1, and cholecystokinin) were measured in all participants and repeated at week 13 and 1 year in the weight-reduced group.

RESULTS

WL led to a reduction in prospective food consumption and an increase in feelings of hunger, fullness, and ghrelin secretion (basal and postprandial), but these new ratings were no different from those seen in controls. Postprandial concentrations of active glucagon-like peptide 1, total peptide YY, and cholecystokinin were lower in individuals with obesity at all time points compared with controls.

CONCLUSION

The increased drive to eat (both subjective feelings of hunger and ghrelin concentrations) seen in reduced-obese individuals, both after acute and sustained WL, reflects a normalization toward a lower body weight. Overall, WL does not have a sustained negative impact on satiety peptide secretion, despite a blunted secretion in individuals with obesity compared with nonobese controls.

Association between gastrointestinal phenotypes and weight gain in younger adults: a prospective 4-year cohort study

Background/Objectives:

Gastrointestinal phenotypes have previously been associated with obesity, however it is unknown if these phenotypes are a cause or a consequence of obesity and weight gain. Our aim was to assess whether these gastrointestinal phenotypes are associated with future weight gain in younger adults.

Subjects/Methods:

At baseline, 126 adult participants under the age of 35 were weighed and underwent measurement of gastrointestinal phenotypes including gastric emptying (GE), gastric volume, satiation, satiety and gastrointestinal hormones. Patients were re-appraised after median 4.4 years unless, during the period of follow up, they participated in a formal weight loss program, received obesity-weight loss interventions, or developed a health condition likely to affect weight. Participants were dichotomized into two groups for each phenotype at the median of each phenotype.

Results:

In total, 60 participants met criteria for inclusion and were evaluated after a median of 4.4 years [IQR: 3.5 to 5],36 participants were excluded due to conditions that would abnormally affect weight during study period including pregnancy and weight loss treatment, and 30 participants were lost to prospective follow-up. Faster GE was significantly associated with weight gain. Those with faster GE at baseline (n=30) gained a median of 9.6 kg [3.1 to 14.9] compared to those with slower GE at baseline (n=30) who gained a median of 2.8 kg [−4.6 to 9.2] (p=0.03), over the follow-up period. There was no association between the other phenotypes and weight gain.

Conclusions:

In adults ≤35 years old, faster gastric emptying is associated with significantly increased weight gain over the medium term. This provides supportive evidence for the role of gastric emptying in weight gain and development of obesity.

Clinical features and disturbances of gastrointestinal transit in patients with rapid gastric emptying

AIMS

Some patients with upper gastrointestinal symptoms have rapid gastric emptying (GE). We aimed to compare patients with normal and rapid GE and to identify phenotypes among patients with rapid GE.

METHODS

Among 2798 patients who underwent GE scintigraphy, we compared patients with normal and rapid GE and separately, patients with rapid GE at 1 hour (GE1), 2 hours (GE2), or both (GE12).

RESULTS

In 2798 patients, GE was normal (74%), delayed (18%), or rapid (8%). Among 211 patients with rapid GE, patterns were rapid GE1 (48%), 2 hours (17%), or 1 and 2 hours (35%); 42 (20%) had diseases that explain rapid GE. A combination of upper and lower gastrointestinal symptoms (54%) was more common that isolated upper (17%) or lower (28%) gastrointestinal symptoms (P < .001). Constipation was more prevalent in patients with rapid GE 2 (72%) than rapid GE 1 (47%) or rapid GE12 hours (67%) (P < .05). Among 179 diabetes mellitus (DM) patients, 15% had rapid GE, which was not associated with the DM phenotype. By multivariable analysis, insulin therapy (odds ratio [OR], 0.36; 95% confidence interval [CI], 0.15-0.88), and weight loss (OR, 0.10; 95% CI, 0.01-0.78) were associated with a lower risk of rapid than normal GE in DM.

CONCLUSIONS

Eight percent of patients undergoing scintigraphy had rapid GE, which is most frequently associated with upper and lower gastrointestinal symptoms; constipation is common. Insulin therapy and weight loss were associated with a lower risk of rapid than normal GE in DM patients.

A Higher Preoperative Glycemic Profile Is Associated with Rapid Gastric Emptying After Sleeve Gastrectomy for Obese Subjects

BACKGROUND

Recent reports have shown that sleeve gastrectomy (SG) accelerates gastric emptying (GE), but the etiology remains unclear. This study aimed to investigate the factors affecting GE before and after SG.

METHODS

We enrolled 35 normal weight healthy subjects and 23 obese patients receiving SG. The normal individuals and obese patients before and 3 months after SG received oatmeal-based scintigraphy to measure GE. Gastrointestinal symptoms and circulating levels of peptide YY (PYY) were also measured.

RESULTS

There were no differences in the GE parameters, including simple half-time at 3 h and percentage of gastric retention at 0.5, 1, 2, and 3 h between healthy controls and pre-SG obese subjects. SG led to accelerated GE, more gastrointestinal symptoms, and increased fasting PYY levels postoperatively. Based on our previously established normal GE values, 18 (78.3%) obese patients with rapid postoperative GE had higher levels of preoperative fasting glucose and glycated hemoglobin, and homeostasis model assessment of the insulin resistance index than those with normal postoperative GE. Twelve (52.2%) obese patients had preoperative diabetes mellitus (DM), and only four (17.4%) remained diabetic after SG. The post-SG gastric retention at 0.5 and 1 h was lower in patients with preoperative DM than in those without preoperative DM. Neither severity of gastrointestinal symptoms nor fasting PYY levels were associated with postoperative GE alterations.

CONCLUSION

Most of the obese patients had accelerated GE after SG. A higher preoperative glycemic profile was associated with rapid post-SG GE.

Clinical Predictors of Rapid Gastric Emptying in Patients Presenting with Dyspeptic Symptoms

BACKGROUND

Rapid gastric emptying (RGE) is defined as less than 30% retention at 1 h of solid meal ingestion. It is unclear whether RGE represents a separated clinical entity or part of the functional dyspepsia spectrum.

AIMS

To determine clinical predictors of RGE in patients presenting with dyspeptic symptoms.

METHODS

Retrospective study of patients who underwent solid Gastric Emptying Scintigraphy to evaluate dyspeptic symptoms from January 2011 to September 2012. Patients with delayed gastric emptying (> 10% gastric retention at 4 h) or prior gastric surgery were excluded. Patients with RGE were compared to those with normal gastric emptying (NGE) in a patient ratio of 1:3. Demographic data, symptoms, comorbidities, surgeries, endoscopy findings, medications, HbA1c, and TSH were analyzed. Univariate and multivariate logistic regression analyses were performed.

RESULTS

A total of 808 patients were included, 202 patients with RGE and 606 patients with NGE. Mean gastric retention at 1 h was 18% [12.0, 24.0] and 65% [52.0, 76.0], respectively. Patient with RGE were more likely to present with nausea/vomiting (OR 2.4, p < 0.001), weight loss (OR 1.7, p = 0.008), and autonomic symptoms (OR 2.8, p = 0.022). Identified clinical predictors of RGE were older age (OR 1.08 [1.01, 1.1], p = 0.018), male gender (OR 2.0 [1.4, 2.9], p ≤ <0.001), higher BMI (OR 1.03 [1.00, 1.05], p = 0.018), diabetes (OR 1.8 [1.2, 2.7], p = 0.05), and fundoplication (OR 4.3 [2.4, 7.7], p ≤ 0.001).

CONCLUSION

RGE represents a distinct population among patients presenting with dyspepsia in whom fundoplication, diabetes, and male gender were the strongest clinical predictors. RGE was significantly associated with nausea/vomiting, weight loss, and autonomic symptoms.

Mechanism of Glucagon-Like Peptide 1 Improvements in Type 2 Diabetes Mellitus and Obesity

PURPOSE OF REVIEW

The purpose of this review is to emphasize the pivotal role of glucagon-like peptide 1 (GLP-1) in tackling the parallel epidemics of obesity and type 2 diabetes (T2DM).

RECENT FINDINGS

GLP-1-based therapies and in particular GLP-1 receptor agonists (GLP-1 RA) have proven to be effective in lowering blood glucose and decreasing weight. GLP-1 RA not only mitigate these significant medical burdens but also result in weight loss and weight loss independent factors that decrease cardiovascular disease (CVD) and microvascular complications of T2DM, such as diabetic nephropathy. GLP-1-based therapies are critical for a patient-centered approach in choosing appropriate pharmacotherapy for T2DM and obesity while also taking into consideration comorbidities, such as cardiovascular and chronic kidney diseases.

Physiological Predictors of Weight Regain at 1-Year Follow-Up in Weight-Reduced Adults with Obesity

OBJECTIVE

This study aimed to assess whether changes in resting metabolic rate (RMR), exercise-induced energy expenditure (EIEE), and appetite following weight loss (WL) are associated with weight regain at 1 year.

METHODS

Thirty-six adults with obesity underwent 8 weeks of a very-low-energy diet, followed by 4 weeks of refeeding and a 1-year maintenance program. RMR, EIEE, appetite ratings, and active ghrelin, peptide YY, glucagon-like peptide-1, cholecystokinin, and insulin concentrations were measured at baseline, week 13, and 1 year.

RESULTS

A 17% WL (-20 ± 5 kg [mean ± SD]; range: -11.7 to -32.2 kg; P < 0.001) was achieved at week 13. After 1 year, weight regain was 2.5 ± 9.0 kg (not significant), ranging from -18.2 to 22.5 kg. Both fat mass and fat-free mass were reduced at week 13 (-17.9 ± 4.8 and -2.9 ± 2.7 kg, respectively; P < 0.001), while only loss of fat mass was sustained at 1 year. WL was associated with reduced RMR, EIEE, and fasting/postprandial insulin (all P < 0.001), as well as increased fasting hunger (P < 0.01) and fasting/postprandial active ghrelin (P < 0.001). There were no significant correlations between changes in RMR, EIEE, or appetite with WL and weight regain at 1 year.

CONCLUSIONS

No clear evidence emerged that changes in RMR, EIEE, or appetite following WL can predict weight regain at 1 year, but larger studies are needed to confirm these results.

Allelic variant in the glucagon-like peptide 1 receptor gene associated with greater effect of liraglutide and exenatide on gastric emptying: A pilot pharmacogenetics study

BACKGROUND

Weight loss in response to the long-acting GLP-1 receptor (GLP1R) analog, liraglutide, is correlated with delay in gastric-emptying (GE). The aim of this pilot study was to assess whether specific genetic variants in GLP1R or TCF7L2 are associated with delayed GE and weight loss in obese patients treated with liraglutide or the short-acting GLP-1 agonist, exenatide.

METHODS

We evaluated in obese individuals the associations of genetic variations of GLP1R (rs6923761) and TCF7L2 (rs7903146) on GE T1/2 and weight from two trials that evaluated separately exenatide, 5 μg BID for 30 days, or liraglutide, 3 mg daily for 5 weeks. Data were analyzed using the dominant genetic model and intention-to-treat analysis.

KEY RESULTS

There was a significant correlation between changes in weight and GE T1/2 (rs  = -.382, P = .004). GLP1R rs6923761 minor allele A (AA_AG) carriers who received either exenatide or liraglutide had greater delay in GE T1/2 relative to baseline (117.9 ± 27.5 [SEM] minutes and 128.9 ± 38.32 minutes) compared to GG genotype (95.8 ± 30.4 minutes and 61.4 ± 21.4 minutes, respectively; P = .11). There was a non-significant difference in weight loss based on GLP1R rs6923761 genotype after 5 weeks of treatment. There were no significant correlations with TCF7L2 (rs7903146) genotype.

CONCLUSIONS & INFERENCES

The minor A allele of GLP1R (rs6923761) is associated with greater delay in GE T1/2 in response to liraglutide and exenatide. These studies provide data to plan pharmacogenetics testing of the hypothesis that GLP1R (rs6923761) influences weight loss in response to GLP1R agonists.

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

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

Relationship of gastric emptying or accommodation with satiation, satiety, and postprandial symptoms in health

The contributions of gastric emptying (GE) and gastric accommodation (GA) to satiation, satiety, and postprandial symptoms remain unclear. We aimed to evaluate the relationships between GA or GE with satiation, satiety, and postprandial symptoms in healthy overweight or obese volunteers (total n = 285, 73% women, mean BMI 33.5 kg/m²): 26 prospectively studied obese, otherwise healthy participants and 259 healthy subjects with previous similar GI testing. We assessed GE of solids, gastric volumes, calorie intake at buffet meal, and satiation by measuring volume to comfortable fullness (VTF) and maximum tolerated volume (MTV) by using Ensure nutrient drink test (30 ml/min) and symptoms 30 min after MTV. Relationships between GE or GA with satiety, satiation, and symptoms were analyzed using Spearman rank (r_s ) and Pearson (R) linear correlation coefficients. We found a higher VTF during satiation test correlated with a higher calorie intake at ad libitum buffet meal (r_s = 0.535, P < 0.001). There was a significant inverse correlation between gastric half-emptying time (GE T_1/2) and VTF (r_s = -0.317, P < 0.001) and the calorie intake at buffet meal (r_s = -0.329, P < 0.001), and an inverse correlation between GE Tlag and GE25% emptied with VTF (r_s = -0.273, P < 0.001 and r_s = -0.248, P < 0.001, respectively). GE T_1/2 was significantly associated with satiation (MTV, R = -0.234, P < 0.0001), nausea (R = 0.145, P = 0.023), pain (R = 0.149, P = 0.012), and higher aggregate symptom score (R = 0.132, P = 0.026). There was no significant correlation between GA and satiation, satiety, postprandial symptoms, or GE. We concluded that GE of solids, rather than GA, is associated with postprandial symptoms, satiation, and satiety in healthy participants.NEW & NOTEWORTHY A higher volume to comfortable fullness postprandially correlated with a higher calorie intake at ad libitum buffet meal. Gastric emptying of solids is correlated to satiation (volume to fullness and maximum tolerated volume) and satiety (the calorie intake at buffet meal) and symptoms of nausea, pain, and aggregate symptom score after a fully satiating meal. There was no significant correlation between gastric accommodation and either satiation or satiety indices, postprandial symptoms, or gastric emptying.

The Gastrointestinal Tract as an Integrator of Mechanical and Hormonal Response to Nutrient Ingestion

Glucose tolerance after meal ingestion in vivo is the result of multiple processes that occur in parallel. Insulin secretion together with reciprocal inhibition of glucagon secretion contributes to glucose tolerance. However, other factors beyond glucose effectiveness and insulin action require consideration. The absorption of ingested nutrients and their subsequent systemic rate of appearance largely depend on the rate of delivery of nutrients to the proximal small intestine. This is determined by the integrated response of the upper gastrointestinal tract to a meal. While gastric emptying is probably the most significant component, other factors need to be considered. This review will examine all processes that could potentially alter the fraction and rate of appearance of ingested nutrients in the peripheral circulation. Several of these processes may be potential therapeutic targets for the prevention and treatment of diabetes. Indeed, there is increased interest in gastrointestinal contributions to nutritional homeostasis, as demonstrated by the advent of antidiabetes therapies that alter gastrointestinal motility, the effect of bariatric surgery on diabetes remission, and the potential of the intestinal microbiome as a modulator of human metabolism. The overall goal of this review is to examine current knowledge of the gastrointestinal contributions to metabolic control.

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

BACKGROUND/OBJECTIVES

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

SUBJECTS/METHODS

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

RESULTS

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

CONCLUSIONS

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

Relationship of body weight with gastrointestinal motor and sensory function: studies in anorexia nervosa and obesity

Background

Whether gastrointestinal motor and sensory function is primary cause or secondary effect of abnormal body weight is uncertain. Moreover, studies relating continuous postprandial sensations of satiation to measurable pathology are scarce. This work assessed postprandial gastrointestinal function and concurrent sensations of satiation across a wide range of body weight and after weight change.

Methods

Patients with anorexia nervosa (AN) and obesity (OB) were investigated in reference to normal weight controls (HC). AN were additionally investigated longitudinally. Gastric emptying, antral contractions and oro-cecal transit after ingestion of a solid meal were investigated by MRI and ¹³C-lactose-ureide breath test. The dependency of self-reported sensations of satiation on the varying degree of stomach filling during gastric emptying was compared between groups.

Results

24 AN (BMI 14.4 (11.9–16.0) kg/m²), 16 OB (34.9 (29.6–41.5) kg/m²) and 20 HC (21.9 (18.9–24.9) kg/m²) were studied. Gastric half-emptying time (t₅₀) was slower in AN than HC (p = 0.016) and OB (p = 0.007), and a negative association between t₅₀ and BMI was observed between BMI 12 and 25 kg/m² (p = 0.007). Antral contractions and oro-cecal transit were not different. For any given gastric content volume, self-reported postprandial fullness was greater in AN than in HC or OB (p < 0.001). After weight rehabilitation, t₅₀ in AN tended to become shorter (p = 0.09) and postprandial fullness was less marked (p < 0.01).

Conclusions

A relationship between body weight and gastric emptying as well as self-reported feelings of satiation is present. AN have slower gastric emptying and heightened visceral perception compared to HC and OB. Longitudinal follow-up after weight rehabilitation in AN suggests these abnormalities are not a primary feature, but secondary to other factors that determine abnormal body weight.

Trial registration

Registered July 20, 2009 at ClinicalTrials.gov (NCT00946816).

Electronic supplementary material

The online version of this article (doi:10.1186/s12876-016-0560-y) contains supplementary material, which is available to authorized users.

Endoscopic Sleeve Gastroplasty Alters Gastric Physiology and Induces Loss of Body Weight in Obese Individuals

BACKGROUND & AIMS

Although bariatric surgery is the most effective therapy for obesity, only a small proportion of candidates undergo this surgery. Endoscopic sleeve gastroplasty (ESG) is a minimally invasive procedure that reduces the size of the gastric reservoir. We investigated its durability and effects on body weight and gastrointestinal function in a prospective study of obese individuals.

METHODS

Twenty-five obese individuals (21 female; mean body mass index, 35.5 ± 2.6 kg/m²; mean age, 47.6 ± 10 years) underwent ESG with endoluminal creation of a sleeve along the gastric lesser curve from September 2012 through March 2015 at the Mayo Clinic in Rochester, Minnesota. Subjects were followed for a median period of 9 months. We measured changes in body weight and recorded adverse events; patients were assessed by endoscopy after 3 months. Four participants underwent pre-ESG and post-ESG analyses to measure solid and liquid gastric emptying, satiation (meal tolerance), and fasting and postprandial levels of insulin, glucose, and gut hormones.

RESULTS

Subjects had lost 53% ± 17%, 56% ± 23%, 54% ± 40%, and 45% ± 41% of excess body weight at 6, 9, 12, and 20 months, respectively, after the procedure (P < .01). Endoscopy at 3 months showed intact gastroplasty in all subjects. After ESG, physiological analyses of 4 participants showed a decrease by 59% in caloric consumption to reach maximum fullness (P = .003), slowing of gastric emptying of solids (P = .03), and a trend toward increased insulin sensitivity (P = .06). Three patients had serious adverse events (a perigastric inflammatory collection, a pulmonary embolism, and a small pneumothorax) but made full recoveries with no need for surgical interventions. No further serious adverse events occurred after the technique was adjusted.

CONCLUSIONS

ESG delays gastric emptying, induces early satiation, and significantly reduces body weight. ESG could be an alternative to bariatric surgery for selected patients with obesity. ClincialTrials.gov number: NCT 01682733.

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 effect of sleeve gastrectomy on GLP-1 secretion and gastric emptying: a prospective study

BACKGROUND

Rapid gastric emptying has been proposed to justify the increase in glucagon-like polypeptide-1 (GLP-1) after laparoscopic sleeve gastrectomy (LSG).

OBJECTIVES

To assess gastric emptying changes after LSG and their relationship with GLP-1 secretion.

SETTING

San Salvatore Hospital general surgery unit, University of L'Aquila, Italy.

METHODS

52 patients underwent gastric emptying scintigraphy for liquid and solid foods, before and 3 months after LSG. Twenty-six patients were in the liquid group (L group) and the remaining in the solid group (S group). We evaluated the half time of gastric emptying (T_1/2) and percentage of gastric retention (%GR) at 15, 30, and 60 minutes for liquids and at 30, 60, 90, and 120 minutes for solids. GLP-1 plasma concentrations were measured in each group before and after LSG and related to %GR. Statistical analysis was performed by Χ2 test and Pearson correlation(r).

RESULTS

After surgery, T_1/2 was significantly accelerated: 15.2±13 min and 33.5±18 min in the L group and S group, respectively (P<.05). In both groups, GLP-1 plasma concentrations were increased at each blood sampling time: 2.91±2.9 pg/mL, 3.06±3.1 pg/mL and 3.21±2.6 pg/mL at 15, 30, and 60 minutes, respectively, (P<.05) for L group and 2.72±1.5 pg/mL, 2.89±2.1 pg/mL, 2.93±1.8 pg/mL, and 2.95±1.9 pg/mL at 30, 60, 90, and 120 minutes, respectively, (P< .05) for the S group. After LSG, GLP-1 and %GR presented a negative linear correlation (r) at each blood sampling time in both groups.

CONCLUSION

The rapid gastric emptying 3 months after LSG upregulates the production of GLP-1 in the distal bowel. Further studies are needed to confirm these findings.

Stress inhibits PYY secretion in obese and normal weight women

The impact of stress on circulating levels of appetite-regulating hormones remains largely unknown. The aim of this study was to analyze the effect of acute psychosocial stress on the gut hormone peptide YY (PYY) secretion in obese and normal weight women. Therefore, we compared pre- and post-prandial plasma PYY secretion of 42 obese and 43 normal weight women in a repeated measure randomized controlled laboratory experiment. PYY and cortisol concentrations were measured and ratings of stress and satiety were also recorded in response to a psychological stressor (Trier Social Stress Test, TSST). PYY samples were collected in the fasting state both before participating in the TSST and before a control session. Participants had a standardized meal after the TSST and control session, respectively. PYY was measured both 30 and 60 min after the TSST and control session, respectively. Stress inhibited PYY secretion as well as food intake in all women, but did not influence subjective satiety perception. The present data indicate that despite of lower PYY levels the subjects' requirement to overeat was not increased. From an evolutionary perspective this finding is adaptive. After stress the organism is prepared for fight or flight reaction, whereas not primarily necessary functions are inhibited. Therefore, increased food intake during stress would be dysfunctional.

Food reward in active compared to inactive men: Roles for gastric emptying and body fat

Habitual exercise could contribute to weight management by altering processes of food reward via the gut-brain axis. We investigated hedonic processes of food reward in active and inactive men and characterised relationships with gastric emptying and body fat. Forty-four men (active: n=22; inactive: n=22, BMI range 21-36kg/m(2); percent fat mass range 9-42%) were studied. Participants were provided with a standardised fixed breakfast and an ad libitum lunch meal 5h later. Explicit liking, implicit wanting and preference among high-fat, low-fat, sweet and savoury food items were assessed immediately post-breakfast (fed state) and again pre-lunch (hungry state) using the Leeds Food Preference Questionnaire. Gastric emptying was assessed by (13)C-octanoic acid breath test. Active individuals exhibited a lower liking for foods overall and a greater implicit wanting for low-fat savoury foods in the fed state, compared to inactive men. Differences in the fed state remained significant after adjusting for percent fat mass. Active men also had a greater increase in liking for savoury foods in the interval between breakfast and lunch. Faster gastric emptying was associated with liking for savoury foods and with an increase in liking for savoury foods in the postprandial interval. In contrast, greater implicit wanting for high-fat foods was associated with slower gastric emptying. These associations were independent of each other, activity status and body fat. In conclusion, active and inactive men differ in processes of food reward. The rate of gastric emptying may play a role in the association between physical activity status and food reward, via the gut-brain axis.

Mechanisms Regulating Insulin Response to Intragastric Glucose in Lean and Non-Diabetic Obese Subjects: A Randomized, Double-Blind, Parallel-Group Trial

Background/Objectives

The changes in blood glucose concentrations that result from an oral glucose challenge are dependent on the rate of gastric emptying, the rate of glucose absorption and the rate of insulin-driven metabolism that include the incretins, glucose-dependent insulinotropic peptide (GIP) and glucagon-like peptide-1 (GLP-1). The rate of insulin-driven metabolism is clearly altered in obese subjects, but it is controversial which of these factors is predominant. We aimed to quantify gastric emptying, plasma insulin, C-peptide, glucagon and glucose responses, as well as incretin hormone secretions in obese subjects and healthy controls during increasing glucose loads.

Subjects/Methods

The study was conducted as a randomized, double-blind, parallel-group trial in a hospital research unit. A total of 12 normal weight (6 men and 6 women) and 12 non-diabetic obese (BMI > 30, 6 men and 6 women) participants took part in the study. Subjects received intragastric loads of 10 g, 25 g and 75 g glucose dissolved in 300 ml tap water.

Results

Main outcome measures were plasma GLP-1 and GIP, plasma glucagon, glucose, insulin, C-peptide and gastric emptying. The primary findings are: i) insulin resistance (P < 0.001) and hyperinsulinemia (P < 0.001); ii) decreased insulin disposal (P < 0.001); iii) trend for reduced GLP-1 responses at 75 g glucose; and iv) increased fasting glucagon levels (P < 0.001) in obese subjects.

Conclusions

It seems that, rather than changes in incretin secretion, fasting hyperglucagonemia and consequent hyperglycemia play a role in reduced disposal of insulin, contributing to hyperinsulinemia and insulin resistance.

Trial Registration

ClinicalTrials.gov NCT01875575

Gastrointestinal traits: individualizing therapy for obesity with drugs and devices

BACKGROUND AND AIMS

The aims of this article were to review the discrepancy between numbers of people requiring weight loss treatment and results and to assess the potential effects of pharmacologic treatments (recently approved for obesity) and endoscopically deployed devices on quantitative GI traits in development for obesity treatment.

METHODS

We conducted a review of relevant literature to achieve our objectives.

RESULTS

The 2013 guidelines increased the number of adults recommended for weight loss treatment by 20.9% (116.0 million to 140.2 million). There is an imbalance between efficacy and costs of commercial weight loss programs and drug therapy (average weight loss about 5 kg). The number of bariatric procedures performed in the United States has doubled in the past decade. The efficacy of bariatric surgery is attributed to reduction in the volume of the stomach, nutrient malabsorption with some types of surgery, increased postprandial incretin responses, and activation of farnesoid X receptor mechanisms. These GI and behavioral traits identify sub-phenotypes of obesity, based on recent research.

CONCLUSIONS

The mechanisms or traits targeted by drug and device treatments include centrally mediated alterations of appetite or satiation, diversion of nutrients, and alteration of stomach capacity, gastric emptying, or incretin hormones. Future treatment may be individualized based on quantitative GI and behavioral traits measured in obese patients.

Exenatide in obesity with accelerated gastric emptying: a randomized, pharmacodynamics study

Obesity is associated with differences in satiety, gastric emptying (GE), gastric volume, and psychological traits. Exenatide, a short-acting glucagon-like peptide 1 (GLP-1) receptor agonist, is associated with variable weight loss. We compared the effects of exenatide, 5 μg, and placebo SQ, twice daily for 30 days on GE of solids and liquids (scintigraphy), satiety (ad libitum buffet meal), satiation (nutrient drink test, maximum tolerated volume [MTV]), and weight loss in 20 participants with documented accelerated GE of solids (T1/2 < 90 min). Exenatide delayed GE of solids (T1/2 [Δ] 86 min relative to placebo, P < 0.001) and reduced calorie intake at buffet meal ([Δ] 129 kcal compared to placebo). Median weight loss was -0.95 kg (IQR -0.7 to -2.1) for exenatide and -0.55 kg (0.3 to -2.1) for placebo (P = 0.23); 80% of exenatide group had documented reduction in weight. In the exenatide treatment group, there was an inverse correlation between gastric emptying T1/2 and MTV (R = -0.548, P = 0.089). The univariate association of weight change with posttreatment MTV was borderline (Rs = 0.43, P = 0.06); in the multiple regression model, posttreatment MTV was associated with weight change (P = 0.047). The effect of the short-acting GLP-1 receptor agonist, exenatide, on GE is associated with the change in food intake, and the latter impacts weight loss in response to exenatide treatment.

The stomach in health and disease

The stomach is traditionally regarded as a hollow muscular sac that initiates the second phase of digestion. Yet this simple view ignores the fact that it is the most sophisticated endocrine organ with unique physiology, biochemistry, immunology and microbiology. All ingested materials, including our nutrition, have to negotiate this organ first, and as such, the stomach is arguably the most important segment within the GI tract. The unique biological function of gastric acid secretion not only initiates the digestive process but also acts as a first line of defence against food-borne microbes. Normal gastric physiology and morphology may be disrupted by Helicobacter pylori infection, the most common chronic bacterial infection in the world and the aetiological agent for most peptic ulcers and gastric cancer. In this state-of-the-art review, the most relevant new aspects of the stomach in health and disease are addressed. Topics include gastric physiology and the role of gastric dysmotility in dyspepsia and gastroparesis; the stomach in appetite control and obesity; there is an update on the immunology of the stomach and the emerging field of the gastric microbiome. H. pylori-induced gastritis and its associated diseases including peptic ulcers and gastric cancer are addressed together with advances in diagnosis. The conclusions provide a future approach to gastric diseases underpinned by the concept that a healthy stomach is the gateway to a healthy and balanced host. This philosophy should reinforce any public health efforts designed to eradicate major gastric diseases, including stomach cancer.

Caloric intake capacity as measured by a standard nutrient drink test helps to predict weight loss after bariatric surgery

BACKGROUND

Instruments that enable to select individuals that will benefit most from bariatric surgery (BS) are necessary to increase its cost-efficiency. Our goal was to assess if intake capacity, measured with a standardized test, predicts response to BS.

METHODS

Patients with criteria for BS were randomly allocated to laparoscopic gastric bypass (LRYGB) or sleeve gastrectomy (LSG). We measured caloric intake capacity before and 1 year after surgery using a standardized nutrient drink test. We evaluated if pre-surgery satiation could predict satiation and weight loss (%) 1 year after surgery using multiple regression modeling. Descriptive statistics are given as mean ± SD.

RESULTS

Fourteen women (48 ± 9 years old, BMI 41 ± 3 kg/m(2)) were evaluated before and 11 ± 2.6 months after surgery (seven LRYGB, seven LSG). Caloric intake capacity diminished after surgery (-950 ± 85 kcal on average [70 ± 8 % decrease over basal intake capacity]; p=0.002) and similarly in both LRYGB (72 ± 7 % decrease) and LSG groups (68 ± 8 % decrease); p=0.5. There was a significant weight reduction after surgery (-32 ± 10 kg [30 ± 8 % of total basal weight]) with a mean post-surgery BMI of 29 ± 2 kg/m(2). The best predictive model of weight loss (%) after surgery (R (2)=89 %, p=0.0009) included: BMI (p=0.0004), surgery type (p=0.01) and pre-surgery intake capacity (p=0.006). Weight loss was higher in heavier patients and those undergoing LRYGB. Patients with higher intake capacity had a poorer outcome independently of basal BMI and surgery type.

CONCLUSIONS

Caloric intake capacity, as measured by a standard nutrient drink test, helps to predict weight loss after bariatric surgery. This test might be useful in algorithms of obesity treatment decision.

Influence of habitual physical activity on gastric emptying in healthy males and relationships with body composition and energy expenditure

Although a number of studies have examined the role of gastric emptying (GE) in obesity, the influences of habitual physical activity level, body composition and energy expenditure (EE) on GE have received very little consideration. In the present study, we compared GE in active and inactive males, and characterised relationships with body composition (fat mass and fat-free mass) and EE. A total of forty-four males (active n 22, inactive n 22; BMI 21-36 kg/m2; percentage of fat mass 9-42%) were studied, with GE of a standardised (1676 kJ) pancake meal being assessed by the [13C]octanoic acid breath test, body composition by air displacement plethysmography, RMR by indirect calorimetry, and activity EE (AEE) by accelerometry. The results showed that GE was faster in active compared with inactive males (mean half-time (t 1/2): active 157 (sd 18) and inactive 179 (sd 21) min, P< 0.001). When data from both groups were pooled, GE t 1/2 was associated with percentage of fat mass (r 0.39, P< 0.01) and AEE (r - 0.46, P< 0.01). After controlling for habitual physical activity status, the association between AEE and GE remained, but not that for percentage of fat mass and GE. BMI and RMR were not associated with GE. In summary, faster GE is considered to be a marker of a habitually active lifestyle in males, and is associated with a higher AEE level and a lower percentage of fat mass. The possibility that GE contributes to a gross physiological regulation (or dysregulation) of food intake with physical activity level deserves further investigation.

Peripheral mechanisms in appetite regulation

Peripheral mechanisms in appetite regulation include the motor functions of the stomach, such as the rate of emptying and accommodation, which convey symptoms of satiation to the brain. The rich repertoire of peripherally released peptides and hormones provides feedback from the arrival of nutrients in different regions of the gut from where they are released to exert effects on satiation, or regulate metabolism through their incretin effects. Ultimately, these peripheral factors provide input to the highly organized hypothalamic circuitry and vagal complex of nuclei to determine cessation of energy intake during meal ingestion, and the return of appetite and hunger after fasting. Understanding these mechanisms is key to the physiological control of feeding and the derangements that occur in obesity and their restoration with treatment (as shown by the effects of bariatric surgery).

Quantitative gastrointestinal and psychological traits associated with obesity and response to weight-loss therapy

BACKGROUND & AIMS

Weight loss after pharmacotherapy varies greatly. We aimed to examine associations of quantitative gastrointestinal and psychological traits with obesity, and to validate the ability of these traits to predict responses of obese individuals to pharmacotherapy.

METHODS

In a prospective study, we measured gastric emptying of solids and liquids, fasting and postprandial gastric volume, satiation by nutrient drink test (volume to fullness and maximal tolerated volume), satiety after an ad libitum buffet meal, gastrointestinal hormones, and psychological traits in 328 normal-weight, overweight, or obese adults. We also analyzed data from 181 previously studied adults to assess associations betwecen a subset of traits with body mass index and waist circumference. Latent dimensions associated with overweight or obesity were appraised by principal component analyses. We performed a proof of concept, placebo-controlled trial of extended-release phentermine and topiramate in 24 patients to validate associations between quantitative traits and response to weight-loss therapy.

RESULTS

In the prospective study, obesity was associated with fasting gastric volume (P = .03), accelerated gastric emptying (P < .001 for solids and P = .011 for liquids), lower postprandial levels of peptide tyrosine tyrosine (P = .003), and higher postprandial levels of glucagon-like peptide 1 (P < .001). In a combined analysis of data from all studies, obesity was associated with higher volume to fullness (n = 509; P = .038) and satiety with abnormal waist circumference (n = 271; P = .016). Principal component analysis identified latent dimensions that accounted for approximately 81% of the variation among overweight and obese subjects, including satiety or satiation (21%), gastric motility (14%), psychological factors (13%), and gastric sensorimotor factors (11%). The combination of phentermine and topiramate caused significant weight loss, slowed gastric emptying, and decreased calorie intake; weight loss in response to phentermine and topiramate was significantly associated with calorie intake at the prior satiety test.

CONCLUSIONS

Quantitative traits are associated with high body mass index; they can distinguish obesity phenotypes and, in a proof of concept clinical trial, predicted response to pharmacotherapy for obesity. ClinicalTrials.gov Number: NCT01834404.

Factors affecting circulating levels of peptide YY in humans: a comprehensive review

As obesity continues to be a global epidemic, research into the mechanisms of hunger and satiety and how those signals act to regulate energy homeostasis persists. Peptide YY (PYY) is an acute satiety signal released upon nutrient ingestion and has been shown to decrease food intake when administered exogenously. More recently, investigators have studied how different factors influence PYY release and circulating levels in humans. Some of these factors include exercise, macronutrient composition of the diet, body-weight status, adiposity levels, sex, race and ageing. The present article provides a succinct and comprehensive review of the recent literature published on the different factors that influence PYY release and circulating levels in humans. Where human data are insufficient, evidence in animal or cell models is summarised. Additionally, the present review explores the recent findings on PYY responses to different dietary fatty acids and how this new line of research will make an impact on future studies on PYY. Human demographics, such as sex and age, do not appear to influence PYY levels. Conversely, adiposity or BMI, race and acute exercise all influence circulating PYY levels. Both dietary fat and protein strongly stimulate PYY release. Furthermore, MUFA appear to result in a smaller PYY response compared with SFA and PUFA. PYY levels appear to be affected by acute exercise, macronutrient composition, adiposity, race and the composition of fatty acids from dietary fat.

Systematic review of ghrelin response to food intake in pediatric age, from neonates to adolescents

OBJECTIVE

Food intake and energy balance are regulated during the lifespan with critical changes in each specific period (infancy, adulthood, aging). Some of ghrelin's changes may contribute to the regulation of food intake and weight in children. We aimed to analyze the ghrelin response to feeding in lean or obese subjects from birth to adolescence.

METHODS

We searched PubMed, Scopus, Google Scholar, Cochrane, and EMBASE (December 1999 to February 2013) and identified 62 relevant articles, of which 29 were suitable to be included.

RESULTS AND CONCLUSIONS

Total ghrelin response to meals is particular, with refractoriness in neonates and lean children and an inhibition that starts from puberty. Total ghrelin levels are decreased after meals, irrespective of pubertal stages in obese children and adolescents. Conversely, total ghrelin is decreased after an oral glucose tolerance test in all ages, with the exception of neonates. Data on unacylated ghrelin response are scant but resemble those of total ghrelin. The acylated ghrelin response to meals or oral glucose tolerance test is discordant, although a precocious inhibition followed by a rise back is present in both lean and obese children. The post-feeding profile in children with Prader-Willi syndrome is also peculiar, with a conserved and deeper inhibition of all ghrelin forms.

Gastrointestinal morbidity in obesity

Obesity is a complex disease that results from increased energy intake and decreased energy expenditure. The gastrointestinal system plays a key role in the pathogenesis of obesity and facilitates caloric imbalance. Changes in gastrointestinal hormones and the inhibition of mechanisms that curtail caloric intake result in weight gain. It is not clear if the gastrointestinal role in obesity is a cause or an effect of this disease. Obesity is often associated with type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD). Obesity is also associated with gastrointestinal disorders, which are more frequent and present earlier than T2DM and CVD. Diseases such as gastroesophageal reflux disease (GERD), cholelithiasis, or nonalcoholic steatohepatitis are directly related to body weight and abdominal adiposity. Our objective is to assess the role of each gastrointestinal organ in obesity and the gastrointestinal morbidity resulting in those organs from the effects of obesity.

Gastric and intestinal satiation in obese and normal weight healthy people

OBJECTIVE

The gastrointestinal tract plays a key role in feelings of satiation. It is known that there is a reciprocal interaction between the stomach and intestine, but it is not known which factors are of gastric origin and which are intestinal. This three-step study therefore sought to provide illumination on satiation parameters with respect to body mass.

METHOD

In the first part, the time needed to reach maximal satiation and total caloric intake was calculated after participants (20 normal weight, 20 obese) imbibed a standardized nutrient drink. In the second part gastric emptying of solids and liquids was evaluated using the (13)C-breath test (participants: 16 normal weight, 9 obese for gastric emptying of solids; 15 normal weight, 14 obese for gastric emptying of liquids). And in the third part, fasting and post-prandial plasma glucagon-like peptide-1 (GLP-1), peptide tyrosine tyrosine (PYY) and ghrelin levels were measured after a standardized nutrient drink (participants: 20 normal weight, 20 obese).

RESULTS

Our results show that, when compared to those of normal weight, obese participants reached maximal satiation sooner (P=0.006), their total intake of calories was higher (P=0.013), and their gastric emptying rates were delayed (P<0.001). Furthermore, their post-prandial increase in plasma GLP-1 and PYY was reduced, (P<0.001 for both), as was their ghrelin suppression (P=0.001).

DISCUSSION

We conclude that, in obese subjects gastric emptying can be impaired with delayed interaction of nutrients with the intestine resulting in decreased GLP-1 and PYY secretion. This could imply that obese participants would require more calories before their maximal satiation is reached and they stop eating.