The role of the gut in regulating food intake in man

Effects of physical form of β-lactoglobulin and calcium ingestion on GLP-1 secretion, gastric emptying and energy intake in humans: a randomised crossover trial

The aim of this study was to assess whether adding Ca2+ to aggregate or native forms of β-lactoglobulin alters gut hormone secretion, gastric emptying rates and energy intake in healthy men and women. Fifteen healthy adults (mean ± sd: 9M/6F, age: 24 ± 5 years) completed four trials in a randomised, double-blind, crossover design. Participants consumed test drinks consisting of 30 g of β-lactoglobulin in a native form with (NATIVE + MINERALS) and without (NATIVE) a Ca2+-rich mineral supplement and in an aggregated form both with (AGGREG + MINERALS) and without the mineral supplement (AGGREG). Arterialised blood was sampled for 120 min postprandially to determine gut hormone concentrations. Gastric emptying was determined using 13C-acetate and 13C-octanoate, and energy intake was assessed with an ad libitum meal at 120 min. A protein × mineral interaction effect was observed for total glucagon-like peptide-1 (GLP-1TOTAL) incremental AUC (iAUC; P < 0·01), whereby MINERALS + AGGREG increased GLP-1TOTAL iAUC to a greater extent than AGGREG (1882 ± 603 v. 1550 ± 456 pmol·l-1·120 min, P < 0·01), but MINERALS + NATIVE did not meaningfully alter the GLP-1 iAUC compared with NATIVE (1669 ± 547 v. 1844 ± 550 pmol·l-1·120 min, P = 0·09). A protein × minerals interaction effect was also observed for gastric emptying half-life (P < 0·01) whereby MINERALS + NATIVE increased gastric emptying half-life compared with NATIVE (83 ± 14 v. 71 ± 8 min, P < 0·01), whereas no meaningful differences were observed between MINERALS + AGGREG v. AGGREG (P = 0·70). These did not result in any meaningful changes in energy intake (protein × minerals interaction, P = 0·06). These data suggest that the potential for Ca2+ to stimulate GLP-1 secretion at moderate protein doses may depend on protein form. This study was registered at clinicaltrials.gov (NCT04659902).

Intraduodenal nutrient infusion differentially alters intestinal nutrient sensing, appetite, and satiety responses in lean and obese subjects

BACKGROUND

Intestinal nutrient sensing regulates food intake and energy metabolism by acting locally and relaying nutritional status to the brain. It is unclear whether these mechanisms are altered in obese humans.

OBJECTIVES

We aimed to investigate differences in duodenal nutrient sensing in humans with or without obesity and the effects of transiently blocking vagal transmission on nutrient sensing, hunger, and appetite.

METHODS

In a single-blinded, randomized, cross-over design, subjects with or without obesity (n = 14 and n = 11, respectively) were infused intraduodenally with saline or a combination of glucose and oleic acid for 90 min (glucose load: 22.5 g, 1 kcal/min; oleic acid load: 10 g, 1 kcal/min) in the presence or absence of local anesthetic (benzocaine). Blood was sampled at 10-min intervals (120-240 min) and 15-min intervals until termination of the study for measurements of gut hormones, insulin, leptin, and C-peptide. Hunger and satiety sensations were scored using the visual analog scale, and hepatic glucose production and glucose oxidation rates were measured.

RESULTS

Duodenal nutrient infusion in lean subjects led to a 65% drop in acyl ghrelin release and robustly increased cholecystokinin 8 (CCK-8) release (65%; P = 0.023); benzocaine infusion delayed this response (2-factor repeated-measures analysis of variance, P = 0.0065). In contrast, subjects with obesity had significantly blunted response to nutrient infusion, and no further effects were observed with benzocaine. Additionally, significant delays were observed in peptide YY (3-36), pancreatic polypeptide, glucose inhibitory peptide, and glucagon-like peptide 1 (7-36) response. No significant interactions were found between body mass index (BMI) or baseline hormone levels and areas under the curve for hormones except CCK-8 (BMI, P = 0.018; baseline CCK, P = 0.013). Nutrient-induced hunger and satiety sensations were impeded by benzocaine only in the lean cohort. Hunger and satiety sensations in subjects with obesity were not responsive to nutrient entry into the duodenum, and no additional effects were observed by blocking neural signaling.

CONCLUSION

Nutrient-induced gut hormone release and response to transient vagal blockade are significantly blunted in subjects with obesity. This trial was registered at clinicaltrials.org as NCT02537314.

In-silico study of the interactions between acylated glucagon like-peptide-1 analogues and the native receptor

We have performed a series of multiple molecular dynamics (MD) simulations of glucagon-like peptide-1 (GLP-1) and acylated GLP-1 analogues in complex with the endogenous receptor (GLP-1R) to obtain a molecular understanding of how fatty acid (FA) chain structure, acylation position on the peptide, and presence of a linker affect the binding. MD simulations were analysed to extract heatmaps of receptor-peptide interaction patterns and to determine the free energy of binding using the molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) approach. The extracted free energies from MM-PBSA calculations are in qualitative agreement with experimentally determined potencies. Furthermore, the interaction patterns seen in the receptor-GLP-1 complex simulations resemble previously reported binding interactions validating the simulations. Analysing the receptor-GLP-1 analogue complex simulations, we found that the major differences between the systems stem from FA interactions and positioning of acylation in the peptide. Hydrophobic interactions between the FA chain and a hydrophobic patch on the extracellular domain contribute significantly to the binding affinity. Acylation on Lys26 resulted in noticeably more interactions between the FA chain and the extracellular domain hydrophobic patch than found for acylation on Lys34 and Lys38, respectively. The presence of a charged linker between the peptide and FA chain can potentially stabilise the complex by forming hydrogen bonds to arginine residues in the linker region between the extracellular domain and the transmembrane domain. A molecular understanding of the fatty acid structure and its effect on binding provides important insights into designing acylated agonists for GLP-1R.Communicated by Ramaswamy H. Sarma.

Vagally Mediated Gut-Brain Relationships in Appetite Control-Insights from Porcine Studies

Signals arising from the upper part of the gut are essential for the regulation of food intake, particularly satiation. This information is supplied to the brain partly by vagal nervous afferents. The porcine model, because of its sizeable gyrencephalic brain, omnivorous regimen, and comparative anatomy of the proximal part of the gut to that of humans, has provided several important insights relating to the relevance of vagally mediated gut-brain relationships to the regulation of food intake. Furthermore, its large size combined with the capacity to become obese while overeating a western diet makes it a pivotal addition to existing murine models, especially for translational studies relating to obesity. How gastric, proximal intestinal, and portal information relating to meal arrival and transit are encoded by vagal afferents and their further processing by primary and secondary brain projections are reviewed. Their peripheral and central plasticities in the context of obesity are emphasized. We also present recent insights derived from chronic stimulation of the abdominal vagi with specific reference to the modulation of mesolimbic structures and their role in the restoration of insulin sensitivity in the obese miniature pig model.

Impaired adaptation of energy intake induces severe obesity in aged mice on a high-fat diet

High-fat diet (HFD) feeding induces inflammation in various tissues, including the nodose ganglion and hypothalamus, resulting in obesity and metabolic disorders. In this study, we investigated the effect of short-term HFD on aged and young mice. Aged mice easily gained weight during short-term HFD feeding, and required many days to adapt their energy intake. One-day HFD in aged mice induced inflammation in the distal colon, but not in the nodose ganglion or hypothalamus. The anorexic effect of glucagon-like peptide-1 (GLP-1) was attenuated in aged mice. Intraperitoneal administration of GLP-1 did not induce expression of genes that regulate feeding in the hypothalamus of aged mice. mRNA expression of the gene encoding the GLP-1 receptor (Glp1r) in the nodose ganglion was significantly lower in aged mice than in young mice. Our findings suggest that adaptation of energy intake regulation was attenuated in aged mice, causing them to become obese in response to short-term HFD feeding.

Salt an Essential Nutrient: Advances in Understanding Salt Taste Detection Using Drosophila as a Model System

Taste modalities are conserved in insects and mammals. Sweet gustatory signals evoke attractive behaviors while bitter gustatory information drive aversive behaviors. Salt (NaCl) is an essential nutrient required for various physiological processes, including electrolyte homeostasis, neuronal activity, nutrient absorption, and muscle contraction. Not only mammals, even in Drosophila melanogaster, the detection of NaCl induces two different behaviors: Low concentrations of NaCl act as an attractant, whereas high concentrations act as repellant. The fruit fly is an excellent model system for studying the underlying mechanisms of salt taste due to its relatively simple neuroanatomical organization of the brain and peripheral taste system, the availability of powerful genetic tools and transgenic strains. In this review, we have revisited the literature and the information provided by various laboratories using invertebrate model system Drosophila that has helped us to understand NaCl salt taste so far. We hope that this compiled information from Drosophila will be of general significance and interest for forthcoming studies of the structure, function, and behavioral role of NaCl-sensitive (low and high concentrations) gustatory circuitry for understanding NaCl salt taste in all animals.

Nutritional Health Considerations for Persons with Spinal Cord Injury

Chronic spinal cord injury (SCI) often results in morbidity and mortality due to all-cause cardiovascular disease (CVD) and comorbid endocrine disorders. Several component risk factors for CVD, described as the cardiometabolic syndrome (CMS), are prevalent in SCI, with the individual risks of obesity and insulin resistance known to advance the disease prognosis to a greater extent than other established risks. Notably, adiposity and insulin resistance are attributed in large part to a commonly observed maladaptive dietary/nutritional profile. Although there are no evidence-based nutritional guidelines to address the CMS risk in SCI, contemporary treatment strategies advocate more comprehensive lifestyle management that includes sustained nutritional guidance as a necessary component for overall health management. This monograph describes factors in SCI that contribute to CMS risks, the current nutritional profile and its contribution to CMS risks, and effective treatment strategies including the adaptability of the Diabetes Prevention Program (DPP) to SCI. Establishing appropriate nutritional guidelines and recommendations will play an important role in addressing the CMS risks in SCI and preserving optimal long-term health.

The effect of preload/meal energy density on energy intake in a subsequent meal: A systematic review and meta-analysis

OBJECTIVE

To conduct a systematic review and meta-analysis of the effects of preload/meal energy density on energy intake in a subsequent meal(s).

METHODS

Multiple databases were searched for studies published through December 2016 on the effects of preload/meal energy density on energy intake in a subsequent meal(s). We extracted information on mean energy intake in a subsequent meal(s) and on variables that could contribute to between-subject heterogeneity.

RESULTS

Forty and Thirty nine eligible studies were identified for our systematic review and meta-analysis, respectively. The meta-analysis showed that preload/meal energy density did not affect energy intake in a subsequent meal(s) (95% CI:-21.21, 21.29). As heterogeneity was remarkable among studies, we stratified the studies by intervention type into "meal" or "preload" classifications. In the "preload" subgroup, studies used either fixed energy or fixed weight preloads. The results reveal that in comparison to a high energy-dense (HED) preload, consuming a low energy-dense (LED) preload with same weight resulted in higher energy intake in a subsequent meal (95% CI: 9.72, 56.19). On the other hand, decreased energy intake was observed after consuming an LED preload compared to after consumption of an HED preload with same energy content (95% CI: -138.71, -57.33). In the "meal" subgroup, studies were categorized by different subsequent meal (i.e., "afternoon or evening", "lunch" and "dinner or post-dinner"). Meta-analysis showed that an LED meal resulted in more energy intake only in afternoon or evening meals (95% CI: 14.82, 31.22).

CONCLUSION

In summary, the current analysis revealed that we can restrict the energy intake by consuming an LED preload. Moreover, consuming an LED preload could favorably affect preload+meal energy intake.

Glucagon-Like Peptide-1 and Its Class B G Protein-Coupled Receptors: A Long March to Therapeutic Successes

The glucagon-like peptide (GLP)-1 receptor (GLP-1R) is a class B G protein-coupled receptor (GPCR) that mediates the action of GLP-1, a peptide hormone secreted from three major tissues in humans, enteroendocrine L cells in the distal intestine, α cells in the pancreas, and the central nervous system, which exerts important actions useful in the management of type 2 diabetes mellitus and obesity, including glucose homeostasis and regulation of gastric motility and food intake. Peptidic analogs of GLP-1 have been successfully developed with enhanced bioavailability and pharmacological activity. Physiologic and biochemical studies with truncated, chimeric, and mutated peptides and GLP-1R variants, together with ligand-bound crystal structures of the extracellular domain and the first three-dimensional structures of the 7-helical transmembrane domain of class B GPCRs, have provided the basis for a two-domain-binding mechanism of GLP-1 with its cognate receptor. Although efforts in discovering therapeutically viable nonpeptidic GLP-1R agonists have been hampered, small-molecule modulators offer complementary chemical tools to peptide analogs to investigate ligand-directed biased cellular signaling of GLP-1R. The integrated pharmacological and structural information of different GLP-1 analogs and homologous receptors give new insights into the molecular determinants of GLP-1R ligand selectivity and functional activity, thereby providing novel opportunities in the design and development of more efficacious agents to treat metabolic disorders.

A Taste Circuit that Regulates Ingestion by Integrating Food and Hunger Signals

Ingestion is a highly regulated behavior that integrates taste and hunger cues to balance food intake with metabolic needs. To study the dynamics of ingestion in the vinegar fly Drosophila melanogaster, we developed Expresso, an automated feeding assay that measures individual meal-bouts with high temporal resolution at nanoliter scale. Flies showed discrete, temporally precise ingestion that was regulated by hunger state and sucrose concentration. We identify 12 cholinergic local interneurons (IN1, for "ingestion neurons") necessary for this behavior. Sucrose ingestion caused a rapid and persistent increase in IN1 interneuron activity in fasted flies that decreased proportionally in response to subsequent feeding bouts. Sucrose responses of IN1 interneurons in fed flies were significantly smaller and lacked persistent activity. We propose that IN1 neurons monitor ingestion by connecting sugar-sensitive taste neurons in the pharynx to neural circuits that control the drive to ingest. Similar mechanisms for monitoring and regulating ingestion may exist in vertebrates.

Physiology of Food Intake Control in Children

The purpose of this review is to draw attention to the limited information available on food intake (FI) control in children and adolescents 7-17 y of age, which is essential for developing food policies and guidelines in this population. Although environmental factors have been the overwhelming focus of research on the causative factors of obesity, research focusing on the physiologic control of appetite in children and adolescents is a neglected area of research. To present this message, a review of FI regulation and the role of food and food components in signaling processes are followed by an examination of the role of hormones during puberty in intake regulation. To examine the interaction of environment and physiology on FI regulation, the effects of exercise, television programs, and food advertisements are discussed. In conclusion, although limited, this literature review supports a need for children and adolescents to be a greater focus of research that would lead to sound nutrition policies and actions to reduce chronic disease. A focus on the environment must be balanced with an understanding of physiologic and behavioral changes associated with this age group.

Instant Oatmeal Increases Satiety and Reduces Energy Intake Compared to a Ready-to-Eat Oat-Based Breakfast Cereal: A Randomized Crossover Trial

Background: Foods that enhance satiety can help consumers to resist environmental cues to eat and help adherence to calorie restriction. The objective of this study was to compare the effect of 2 oat-based breakfast cereals on appetite, satiety, and food intake.

Methods: Forty-eight healthy individuals, 18 years of age or older, were enrolled in a randomized, crossover trial. Subjects consumed isocaloric servings of either oatmeal or an oat-based ready-to-eat breakfast cereal (RTEC) in random order at least a week apart. Visual analogue scales measuring appetite and satiety were completed before breakfast and throughout the morning. Lunch was served 4 hours after breakfast. The physicochemical properties of oat soluble fiber (β-glucan) were determined. Appetite and satiety responses were analyzed by area under the curve. Food intake and β-glucan properties were analyzed using t tests.

Results: Oatmeal increased fullness (p = 0.001) and reduced hunger (p = 0.005), desire to eat (p = 0.001), and prospective intake (p = 0.006) more than the RTEC. Energy intake at lunch was lower after eating oatmeal compared to the RTEC (p = 0.012). Oatmeal had higher viscosity (p = 0.03), β-glucan content, molecular weight (p < 0.001), and radius of gyration (p < 0.001) than the RTEC.

Conclusions: Oatmeal suppresses appetite, increases satiety, and reduces energy intake compared to the RTEC. The physicochemical properties of β-glucan and sufficient hydration of oats are important factors affecting satiety and subsequent energy intake.

An afternoon snack of berries reduces subsequent energy intake compared to an isoenergetic confectionary snack

Observational studies suggest that increased fruit and vegetable consumption can contribute to weight maintenance and facilitate weight loss when substituted for other energy dense foods. Therefore, the purpose of the present study was to assess the effect of berries on acute appetite and energy intake. Twelve unrestrained pre-menopausal women (age 21 ± 2 y; BMI 26.6 ± 2.6 kg m(-2); body fat 23 ± 3%) completed a familiarisation trial and two randomised experimental trials. Subjects arrived in the evening (~5pm) and consumed an isoenergetic snack (65 kcal) of mixed berries (BERRY) or confectionary sweets (CONF). Sixty min later, subjects consumed a homogenous pasta test meal until voluntary satiation, and energy intake was quantified. Subjective appetite (hunger, fullness, desire to eat and prospective food consumption) was assessed throughout trials, and for 120 min after the test meal. Energy intake was less (P<0.001) after consumption of the BERRY snack (691 ± 146 kcal) than after the CONF snack (824 ± 172 kcal); whilst water consumption was similar (P=0.925). There were no trial (P>0.095) or interaction (P>0.351) effects for any subjective appetite ratings. Time taken to eat the BERRY snack (4.05 ± 1.12 min) was greater (P<0.001) than the CONF snack (0.93 ± 0.33 min). This study demonstrates that substituting an afternoon confectionary snack with mixed berries decreased subsequent energy intake at dinner, but did not affect subjective appetite. This dietary strategy could represent a simple method for reducing daily energy intake and aiding weight management.

Targeting the intestinal L-cell for obesity and type 2 diabetes treatment

Degradation-resistant glucagon-like peptide-1 (GLP-1) mimetics and GLP-1 enhancers (inhibitors of dipeptidyl peptidase-4, the enzyme which degrades and inactivates GLP-1) have been used for treatment of type 2 diabetes mellitus since 2005-2006. Cutting-edge research is now focusing on uncovering the secretory mechanisms of the GLP-1-producing cells (L-cells) with the purpose of developing agonists that enhance endogenous hormone secretion. Since GLP-1 co-localizes with other anorectic peptides, cholecystokinin, oxyntomodulin/glicentin and peptide YY, L-cell targeting might cause release of several hormones at the same time, providing additive effects on appetite and glucose regulation. In this review, we explore the role of proglucagon-derived peptides and other L-cell co-localizing hormones, in appetite regulation and the mechanism regulating their secretion.

Temperature can influence gastric accommodation and sensitivity in functional dyspepsia with epigastric pain syndrome

BACKGROUND

Functional dyspepsia-epigastric pain syndrome (FD-EPS) is characterized pathophysiologically by visceral hypersensitivity, but the effect of the temperature stimulation on gastric function has been seldom studied.

AIM

The purpose of this study was to investigate the effects of liquid nutrients at different temperatures on the gastric accommodation, sensitivity, and gastric-wall compliance of healthy subjects (HS) and FD-EPS patients.

METHODS

Ten FD-EPS patients (Roma III criteria) and ten HS were recruited into the study. Intragastric pressure (IGP) and gastric perfusion were measured and compared following the administration of liquid nutrients at 37 °C on day 1 and at 8 °C on day 2.

RESULTS

Seven patients developed abdominal discomfort or abdominal pain after being given cold liquid nutrient. The administration of liquid nutrient at 8 °C resulted in an increase of IGP in HS (P=0.044), a significant decrease in gastric perfusion (P<0.0001), a marked increase in IGP (P=0.015), and a dramatic reduction in gastric wall compliance (P=0.012) in patients compared to the effects of liquid nutrient at 37 °C. In addition, IGP in patients was lower than that in HS at 37 °C liquid nutrient (P=0.036), and the gastric perfusion volume in patients at maximal satiety was also significantly reduced at 8 °C liquid nutrient compared with HS (P=0.017).

CONCLUSIONS

Cold stimulation can increase the IGP in HS and FD-EPS patients, elevate the visceral sensitivity and reduce the gastric volume of FD-EPS patients. FD-EPS patients who are sensitive to cold may develop epigastric discomfort or pain.

Fructose metabolism in humans - what isotopic tracer studies tell us

Fructose consumption and its implications on public health are currently under study. This work reviewed the metabolic fate of dietary fructose based on isotope tracer studies in humans. The mean oxidation rate of dietary fructose was 45.0% ± 10.7 (mean ± SD) in non-exercising subjects within 3–6 hours and 45.8% ± 7.3 in exercising subjects within 2–3 hours. When fructose was ingested together with glucose, the mean oxidation rate of the mixed sugars increased to 66.0% ± 8.2 in exercising subjects. The mean conversion rate from fructose to glucose was 41% ± 10.5 (mean ± SD) in 3–6 hours after ingestion. The conversion amount from fructose to glycogen remains to be further clarified. A small percentage of ingested fructose (<1%) appears to be directly converted to plasma TG. However, hyperlipidemic effects of larger amounts of fructose consumption are observed in studies using infused labeled acetate to quantify longer term de novo lipogenesis. While the mechanisms for the hyperlipidemic effect remain controversial, energy source shifting and lipid sparing may play a role in the effect, in addition to de novo lipogenesis. Finally, approximately a quarter of ingested fructose can be converted into lactate within a few of hours. The reviewed data provides a profile of how dietary fructose is utilized in humans.

Short-term effects of ratio of energy nutrients on appetite-related hormones in female college students

Understanding the relationship between energy nutrients compositions in a diet and appetite-controlling substances is essential for providing sound advice to anyone attempting to control body weight. Appetite is known to be affected by various hormones, ghrelin and peptide tyrosine-tyrosine (PYY), which are related to the compositions of a diet. The purpose of this study was to investigate the effects of compositions of energy nutrients in the diet on the levels of postprandial appetite-related hormones and satiety in healthy adult women. Ten subjects (BMI: 18.5-22.9 kg/m²) were recruited and assigned to three iso-coloric breakfast meals with different compositions of energy nutrients, regular meal (RM, CHO: 60%, Pro: 20%, Fat: 20%), high protein meal (HPM, CHO: 30%, Pro: 50%, Fat: 20%), and high fat meal (HFM, CHO: 30%, Pro: 20%, Fat: 50%). Blood levels of ghrelin, PYY, insulin and leptin and satiety were assessed at baseline, 30, 60, 90, 120, and 180 min following the consumption of each meal. There was no significant difference in the fasting blood hormones among the subjects taking each meals at baseline. Blood levels of ghrelin and insulin changed significantly following the consumption of each meal (p<0.05) over time, however no significant difference was shown between experimental meals until 180 min. Blood levels of PYY and leptin were not changed following the ingestion of each meals. In conclusion, the composition of energy nutrients in a diet had no effect on the postprandial plasma levels of ghrelin, PYY, insulin and leptin as well as satiety in healthy adult women.

Addition of sucralose enhances the release of satiety hormones in combination with pea protein

SCOPE

Exposing the intestine to proteins or tastants, particularly sweet, affects satiety hormone release. There are indications that each sweetener has different effects on this release, and that combining sweeteners with other nutrients might exert synergistic effects on hormone release.

METHODS AND RESULTS

STC-1 cells were incubated with acesulfame-K, aspartame, saccharine, sucralose, sucrose, pea, and pea with each sweetener. After a 2-h incubation period, cholecystokinin(CCK) and glucagon-like peptide 1 (GLP-1) concentrations were measured. Using Ussing chamber technology, the mucosal side of human duodenal biopsies was exposed to sucrose, sucralose, pea, and pea with each sweetener. CCK and GLP-1 levels were measured in basolateral secretions. In STC-1 cells, exposure to aspartame, sucralose, sucrose, pea, and pea with sucralose increased CCK levels, whereas GLP-1 levels increased after addition of all test products. Addition of sucrose and sucralose to human duodenal biopsies did not affect CCK and GLP-1 release; addition of pea stimulated CCK and GLP-1 secretion.

CONCLUSION

Combining pea with sucrose and sucralose induced even higher levels of CCK and GLP-1. Synchronous addition of pea and sucralose to enteroendocrine cells induced higher levels of CCK and GLP-1 than addition of each compound alone. This study shows that combinations of dietary compounds synergize to enhance satiety hormone release.

The effects of weight loss strategies on gastric emptying and appetite control

The gastrointestinal tract plays an important role in the improved appetite control and weight loss in response to bariatric surgery. Other strategies which similarly alter gastrointestinal responses to food intake could contribute to successful weight management. The aim of this review is to discuss the effects of surgical, pharmacological and behavioural weight loss interventions on gastrointestinal targets of appetite control, including gastric emptying. Gastrointestinal peptides are also discussed because of their integrative relationship in appetite control. This review shows that different strategies exert diverse effects and there is no consensus on the optimal strategy for manipulating gastric emptying to improve appetite control. Emerging evidence from surgical procedures (e.g. sleeve gastrectomy and Roux-en-Y gastric bypass) suggests a faster emptying rate and earlier delivery of nutrients to the distal small intestine may improve appetite control. Energy restriction slows gastric emptying, while the effect of exercise-induced weight loss on gastric emptying remains to be established. The limited evidence suggests that chronic exercise is associated with faster gastric emptying, which we hypothesize will impact on appetite control and energy balance. Understanding how behavioural weight loss interventions (e.g. diet and exercise) alter gastrointestinal targets of appetite control may be important to improve their success in weight management.

Dose-dependent suppression of hunger by a specific alginate in a low-viscosity drink formulation

Addition of specific types of alginates to drinks can enhance postmeal suppression of hunger, by forming strong gastric gels in the presence of calcium. However, some recent studies have not demonstrated an effect of alginate/calcium on appetite, perhaps because the selected alginates do not produce sufficiently strong gels or because the alginates were not sufficiently hydrated when consumed. Therefore, the objective of the study was to test effects on appetite of a strongly gelling and fully hydrated alginate in an acceptable, low-viscosity drink formulation. In a balanced order crossover design, 23 volunteers consumed a meal replacement drink containing protein and calcium and either 0 (control), 0.6, or 0.8% of a specific high-guluronate alginate. Appetite (six self-report scales) was measured for 5 h postconsumption. Relevant physicochemical properties of the drinks were measured, i.e., product viscosity and strength of gel formed under simulated gastric conditions. Hunger was robustly reduced (20-30% lower area under the curve) with 0.8% alginate (P < 0.001, analysis of covariance), an effect consistent across all appetite scales. Most effects were also significant with 0.6% alginate, and a clear dose-response observed. Gastric gel strength was 1.8 and 3.8 N for the 0.6 and 0.8% alginate drinks, respectively, while product viscosity was acceptable (<0.5 Pa.s at 10 s(-1)). We conclude that strongly gastric-gelling alginates at relatively low concentrations in a low-viscosity drink formulation produced a robust reduction in hunger responses. This and other related studies indicate that the specific alginate source and product matrix critically impacts upon apparent efficacy.

Satiety: have we neglected dietary non-nutrients?

Satiety, which is the inhibition of eating following the end of a meal, is influenced by a number of food characteristics, including compositional and structural factors. An increased understanding of these factors and the mechanisms whereby they exert their effects on satiety may offer a food-based approach to weight management. Water and gas, which are often neglected in nutrition, are major components of many foods and contribute to volume, and to sensory and other characteristics. A review of previous short-term studies that evaluated the effects of water or gas in foods on satiety showed that while satiety was generally increased, effects on subsequent intakes were not always apparent. These studies were diverse in terms of design, timings and food matrices, which precludes definitive conclusions. However, the results indicate that solids may be more effective at increasing satiety than liquids, but gas may be as effective as water. Although increased gastric distension may be the main mechanism underlying these effects, pre-ingestive and ingestive impacts on cognitive, anticipatory and sensory responses also appear to be involved. Furthermore, there is limited evidence that water on its own may be effective at increasing satiety and decreasing intakes when drunk before, but not with, a meal. Longer-term extrapolation suggests that increasing food volumes with water or gas may offer weight-management strategies. However, from a practical viewpoint, the effects of water and gas on satiety may be best exploited by using these non-nutrients to manipulate perceived portion sizes, without increasing energy contents.

Monosodium glutamate raises antral distension and plasma amino acid after a standard meal in humans

The consumption of monosodium glutamate (MSG) is advocated to elicit physiological and metabolic effects, yet these effects have been poorly investigated directly in humans and in particular in the postprandial phase. Thirteen healthy adults were supplemented for 6 days with a nutritional dose of MSG (2 g) or sodium chloride (NaCl) as control, following a crossover design. On the 7th day, they underwent a complete postprandial examination for the 6 h following the ingestion of the same liquid standard meal (700 kcal, 20% of energy as [(15)N]protein, 50% as carbohydrate, and 30% as fat) supplemented with MSG or NaCl. Real-ultrasound measures of antral area indicated a significant increased distension for the 2 h following the meal supplemented with MSG vs. NaCl. This early postprandial phase was also associated with significantly increased levels of circulating leucine, isoleucine, valine, lysine, cysteine, alanine, tyrosine, and tryptophan after MSG compared with NaCl. No changes to the postprandial glucose, insulin, glucagon-like peptide (GLP)-1, and ghrelin were noted between MSG- and NaCl-supplemented meals. Subjective assessments of hunger and fullness were neither affected by MSG supplementation. Finally, the postprandial fate of dietary N was identical between dietary conditions. Our findings indicate that nutritional dose of MSG promoted greater postprandial elevations of several indispensable amino acids in plasma and induced gastric distension. Further work to elucidate the possible sparing effect of MSG on indispensable amino acid first-pass uptake in humans is warranted. This trial was registered at clinicaltrials.gov as NCT00862017.

Oral and gastrointestinal sensing of dietary fat and appetite regulation in humans: modification by diet and obesity

Dietary fat interacts with receptors in both the oral cavity and the gastrointestinal (GI) tract to regulate fat and energy intake. This review discusses recent developments in our understanding of the mechanisms underlying the effects of fat, through its digestive products, fatty acids (FAs), on GI function and energy intake, the role of oral and intestinal FA receptors, and the implications that changes in oral and small intestinal sensitivity in response to ingested fat may have for the development of obesity.

Gastrointestinal targets of appetite regulation in humans

The aim of this paper is to describe and discuss relevant aspects of the assessment of physiological functions - and related biomarkers - implicated in the regulation of appetite in humans. A short introduction provides the background and the present state of biomarker research as related to satiety and appetite. The main focus of the paper is on the gastrointestinal tract and its functions and biomarkers related to appetite for which sufficient data are available in human studies. The first section describes how gastric emptying, stomach distension and gut motility influence appetite; the second part describes how selected gastrointestinal peptides are involved in the control of satiety and appetite (ghrelin, cholecystokinin, glucagon-like peptide, peptide tyrosin-tyrosin) and can be used as potential biomarkers. For both sections, methodological aspects (adequacy, accuracy and limitation of the methods) are described. The last section focuses on new developments in techniques and methods for the assessment of physiological targets involved in appetite regulation (including brain imaging, interesting new experimental approaches, targets and markers). The conclusion estimates the relevance of selected biomarkers as representative markers of appetite regulation, in view of the current state of the art.

Reduction in postprandial glucose excursion and prolongation of satiety: possible explanation of the long-term effects of whole grain Salba (Salvia Hispanica L.)

Despite strong correlations linking whole-grain consumption to reductions in heart disease, the physiological mechanisms involved remain ambiguous. We assessed whether Salba (Salvia Hispanica L.) whole grain reduces postprandial glycemia in healthy subjects, as a possible explanation for its cardioprotective effects observed in individuals with diabetes. The study used acute, randomized, double-blind, controlled design in which 11 healthy individuals (6 males and 5 females; body mass index 22.3+/-2.8 kg/m(2)) received 0, 7, 15 or 24 g of Salba baked into white bread. Capillary samples and appetite ratings were collected over 2 h after consumption. A dose-response reduction in postprandial glycemia (P=0.002, r(2)=0.203) was observed with all three doses of Salba, significantly decreasing incremental areas under the curve (iAUCs) and time point-specific blood glucose (P<0.05). Appetite ratings were decreased at 60 min after high, 90 min after high and intermediate and at 120 min after all treatments (P<0.05). Decrease in postprandial glycemia provides a potential explanation for improvements in blood pressure, coagulation and inflammatory markers previously observed after 12-week Salba supplementation in type II diabetes.

Reduced glycaemic and insulinaemic responses following isomaltulose ingestion: implications for postprandial substrate use

The impact of slow digestible sources of dietary carbohydrate in reducing the risk of developing obesity and related metabolic disorders is unclear. The aim of the present study was to compare the postprandial metabolic response to the ingestion of sucrose v. isomaltulose. We hypothesised that the reduced digestion and absorption rate of isomaltulose would result in lower glycaemic and insulinaemic responses when compared with the ingestion of sucrose, leading to greater postprandial fat oxidation rates. In a randomised, single-blind, cross-over study, ten overweight subjects ingested two different carbohydrate drinks (sucrose and isomaltulose, 75 g carbohydrate equivalents) following an overnight fast (08.40 hours) and with a standardised meal (12.30 hours, 25 % of total energy content was provided as either a sucrose or isomaltulose drink). Blood samples were taken before ingestion and every 30 min thereafter for a period of 3 h, substrate use was assessed by indirect calorimetry and breath samples were collected. Ingestion of carbohydrates with a mixed meal resulted in a lower peak glucose and insulin response and a lower change in area under the curve (DeltaAUC) following isomaltulose when compared with sucrose. Together with the lower glucose and insulin responses, postprandial fat oxidation rates were higher (14 %) with isomaltulose when compared with sucrose when ingested with a mixed meal (P = 0.02). The attenuated rise in glucose and insulin concentrations following isomaltulose results in reduced inhibition of postprandial fat oxidation. The metabolic response to isomaltulose co-ingestion suggests that this may represent an effective nutritional strategy to counteract overweight-induced metabolic disturbances.

The spectrum of antidiabetic actions of GLP-1 in patients with diabetes

This article focusses on the antidiabetic therapeutic potential of the incretin hormone glucagon-like peptide-1 (GLP-1) in the treatment of patients with type 2 diabetes mellitus (T2DM). T2DM is characterised by insulin resistance, impaired glucose-induced insulin secretion and inappropriately regulated glucagon secretion, which in combination eventually result in hyperglycaemia and, in the longer term, microvascular and macrovascular diabetic complications. Traditional treatment modalities - even multidrug approaches - for T2DM are often unsatisfactory in making patients reach glycaemic goals as the disease progresses caused by a steady, relentless decline in pancreatic beta-cell function. Furthermore, current treatment modalities are often limited by inconvenient dosing regimens and safety and tolerability issues, the latter including hypoglycaemia, body weight gain, oedema and gastrointestinal side effects. Therefore, the actions of GLP-1, which include the potentation of meal-induced insulin secretion and trophic effects on the beta-cell, have attracted a lot of interest. GLP-1 also inhibits glucagon secretion and suppresses food intake and appetite.

Sweetness and bitterness taste of meals per se does not mediate gastric emptying in humans

In cell line and animal models, sweet and bitter tastants induce secretion of signaling peptides (e.g., glucagon-like peptide-1 and cholecystokinin) and slow gastric emptying (GE). Whether human GE and appetite responses are regulated by the sweetness or bitterness per se of ingested food is, however, unknown. We aimed to determine whether intragastric infusion of "equisweet" (Study A) or "equibitter" (Study B) solutions slow GE to the same extent, and whether a glucose solution made sweeter by the addition of saccharin will slow GE more potently than glucose alone. Healthy nonobese subjects were studied in a single-blind, randomized fashion. Subjects received 500-ml intragastric infusions of predetermined equisweet solutions of glucose (560 mosmol/kgH(2)O), fructose (290 mosmol/kgH(2)O), aspartame (200 mg), and saccharin (50 mg); twice as sweet glucose + saccharin, water (volumetric control) (Study A); or equibitter solutions of quinine (0.198 mM), naringin (1 mM), or water (Study B). GE was evaluated using a [(13)C]acetate breath test, and hunger and fullness were scored using visual analog scales. In Study A, equisweet solutions did not empty similarly. Fructose, aspartame, and saccharin did not slow GE compared with water, but glucose did (P < 0.05). There was no additional effect of the sweeter glucose + saccharin solution (P > 0.05, compared with glucose alone). In Study B, neither bitter tastant slowed GE compared with water. None of the solutions modulated perceptions of hunger or fullness. We conclude that, in humans, the presence of sweetness and bitterness taste per se in ingested solutions does not appear to signal to influence GE or appetite perceptions.

Conference on "Multidisciplinary approaches to nutritional problems". Postgraduate Symposium. The role of fat in gastric emptying and satiety: acute and chronic effects

Dietary fat is an important factor in the aetiology of obesity and the metabolic syndrome. It has been widely debated whether gastric emptying (GE) is altered in obesity. GE times have been reported as both longer and shorter in obese individuals compared with matched lean individuals. However, the general consensus is that GE is accelerated and satiety is lower in obesity. Research has implicated a high-fat (HF) diet in these findings. A single HF meal has a longer GE time than a low-fat meal and can even delay GE of the subsequent meal. However, an HF diet has shown different effects. Feeding a HF diet adapts gastrointestinal function to reduce GE times in comparison with a low-fat diet. Increased GE may lead to decreased satiety and faster onset of subsequent eating episodes. Further results have suggested that consuming an HF diet for 14 d increases the GE rate of HF food but not low-fat food. Consuming HF diets for 2 weeks has also been shown to increase food intake. Decreased satiation following an HF diet may cause increased food intake and a positive energy balance, potentially resulting in a gradual increase in adiposity. Recent results have suggested that gastrointestinal transit is accelerated following only 3 d on a HF diet. The variable GE times reported in obesity may be associated with interactions between the HF diet and obesity and not simply the obese state.

Satiety drinking tests: effects of caloric content, drinking rate, gender, age, and body mass index

OBJECTIVE

To compare the maximum tolerated volumes (MTVs) of drinking water and a nutrient liquid at different rates of drinking and to assess the best drinking test correlating with the symptom scores.

MATERIAL AND METHODS

Healthy volunteers were requested to drink water at a rate of 10 ml/min or a nutrient liquid drink at 100 and 20 ml/min on three separate occasions. Symptoms of bloating, nausea, and abdominal pain were assessed 30 min after the cessation of drinking using visual analogue scales.

RESULTS

The MTV of water was 1595 +/- 405 in males and 1327 +/- 308 in females (p<0.05). In rapid nutrient drinking, the MTV was 945 +/- 376 ml in males, whereas females tolerated 760 +/- 174 ml (p<0.05). In slow nutrient drinking, the MTV was 692 +/- 184 ml in males and 594 +/- 131 ml in females (p=0.051). Multiple regression analysis showed no influence of body mass index (BMI), age, or gender in slow nutrient drinking. However, drinking capacity was significantly influenced by gender, age, and BMI in rapid water drinking and by gender in rapid nutrient drinking. When the tolerated volumes for satiety drinking tests were compared, only males showed some significant positive correlations. Symptom scores were higher after slow nutrient drinking compared to the other two drinking tests.

CONCLUSIONS

The rate of drinking and the caloric content affect the MTVs in satiety drinking tests. Slow nutrient drinking appears to be the best choice among the different satiety drink tests, as MTV in this test was not influenced by BMI or age and was associated with higher symptom scores.

No effect of added beta-glucan or of fructooligosaccharide on appetite or energy intake

BACKGROUND

An increase in gastrointestinal viscosity or colonic fermentation is suggested to improve appetite control and reduce food intake. It has been proposed that beta-glucan and fructooligosaccharide (FOS) are food ingredients that increase gastrointestinal viscosity and colonic fermentation, but the results are inconclusive.

OBJECTIVE

The objective was to test the effect of FOS, beta-glucan, or a combination thereof on appetite ratings and food intake over 2 consecutive days.

DESIGN

In a 4-way balanced-order, crossover, double-blind design, 21 healthy volunteers [mean body mass index (in kg/m(2)) 25.9] consumed a meal-replacement bar at 0900 and an ad libitum lunch at 1300 on 2 consecutive days. On day 1 only, the subjects consumed a second (identical) bar at 1700 and a fixed snack at 1900. The control bar contained 0.3 g beta-glucan from 6.8 g oats (control), and the 3 equicaloric test bars contained an additional 0.9 g beta-glucan (from 8.0 g barley), 8 g FOS, or 0.9 g beta-glucan + 8 g FOS. Appetite scores and subsequent ad libitum test meal intakes were measured. Viscosities in response to bar consumption were determined under simulated gastric conditions. The results were analyzed by analysis of covariance.

RESULTS

The addition of beta-glucan, FOS, or a combination thereof did not affect appetite ratings or food intake, although the addition of beta-glucan to the bar doubled gastric viscosity (841 compared with 351 mPa . s).

CONCLUSIONS

Consumption of beta-glucan, FOS, or a combination thereof in meal-replacement bars at the levels tested for 2 consecutive days does not improve appetite control. Efficacy may have improved if the consumption period was longer, if the content of beta-glucan was greater, or if a form of beta-glucan that generates even higher gastric viscosity was consumed. This trial was registered at (clinicaltrials.gov) as NCT00776256.

Effect of intragastric acid stability of fat emulsions on gastric emptying, plasma lipid profile and postprandial satiety

Fat is often included in common foods as an emulsion of dispersed oil droplets to enhance the organoleptic quality and stability. The intragastric acid stability of emulsified fat may impact on gastric emptying, satiety and plasma lipid absorption. The aim of the present study was to investigate whether, compared with an acid-unstable emulsion, an acid-stable fat emulsion would empty from the stomach more slowly, cause more rapid plasma lipid absorption and cause greater satiety. Eleven healthy male volunteers received on two separate occasions 500 ml of 15 % (w/w) [13C]palmitate-enriched olive oil-in-water emulsion meals which were either stable or unstable in the acid gastric environment. MRI was used to measure gastric emptying and the intragastric oil fraction of the meals. Blood sampling was used to measure plasma lipids and visual analogue scales were used to assess satiety. The acid-unstable fat emulsion broke and rapidly layered in the stomach. Gastric emptying of meal volume was slower for the acid-stable fat emulsion (P < 0·0001; two-way ANOVA). The rate of energy delivery of fat from the stomach to the duodenum was not different up to t = 110 min. The acid-stable emulsion induced increased fullness (P < 0·05), decreased hunger (P < 0·0002), decreased appetite (P < 0·0001) and increased the concentration of palmitic acid tracer in the chylomicron fraction (P < 0·04). This shows that it is possible to delay gastric emptying and increase satiety by stabilising the intragastric distribution of fat emulsions against the gastric acid environment. This could have implications for the design of novel foods.

The physiology of glucagon-like peptide 1

Glucagon-like peptide 1 (GLP-1) is a 30-amino acid peptide hormone produced in the intestinal epithelial endocrine L-cells by differential processing of proglucagon, the gene which is expressed in these cells. The current knowledge regarding regulation of proglucagon gene expression in the gut and in the brain and mechanisms responsible for the posttranslational processing are reviewed. GLP-1 is released in response to meal intake, and the stimuli and molecular mechanisms involved are discussed. GLP-1 is extremely rapidly metabolized and inactivated by the enzyme dipeptidyl peptidase IV even before the hormone has left the gut, raising the possibility that the actions of GLP-1 are transmitted via sensory neurons in the intestine and the liver expressing the GLP-1 receptor. Because of this, it is important to distinguish between measurements of the intact hormone (responsible for endocrine actions) or the sum of the intact hormone and its metabolites, reflecting the total L-cell secretion and therefore also the possible neural actions. The main actions of GLP-1 are to stimulate insulin secretion (i.e., to act as an incretin hormone) and to inhibit glucagon secretion, thereby contributing to limit postprandial glucose excursions. It also inhibits gastrointestinal motility and secretion and thus acts as an enterogastrone and part of the "ileal brake" mechanism. GLP-1 also appears to be a physiological regulator of appetite and food intake. Because of these actions, GLP-1 or GLP-1 receptor agonists are currently being evaluated for the therapy of type 2 diabetes. Decreased secretion of GLP-1 may contribute to the development of obesity, and exaggerated secretion may be responsible for postprandial reactive hypoglycemia.

Glycaemic response to foods: Impact on satiety and long-term weight regulation

Should future nutritional recommendations for the general population take into account the notion of glycaemic index (GI)? This question is all the more legitimate as the glycaemic response to foods seems to be a factor that affects satiety and could therefore affect food intake. The aim of this review was to evaluate whether altering the glycaemic response per se can modulate satiety and to assess the short-term and long-term consequences. A systematic review of human intervention studies was performed. Confounding factors that may influence both GI and satiety were taken into consideration when selecting the studies. Thirty-two studies were thus selected and analysed. There is evidence from the short-term studies (1 day) that low-glycaemic foods or meals have higher satietogenic effect than high-glycaemic foods or meals. This substantiates claims such as 'low-GI foods help one to feel fuller for longer than equivalent high-GI foods'. The mechanisms involved may be the specific effect of blood glucose levels on satiety (glucostatic theory) and other stimuli (e.g. peptides) involved in the control of appetite. In some studies, however it seems difficult to tease out the separate effect of the lowering of postprandial glycaemia per se and fibres. Because of the increasing number of confounding variables in the available long-term studies, it is not possible to conclude that low-glycaemic diets mediate a health benefit based on body weight regulation. The difficulty of demonstrating the long-term health benefit of a satietogenic food or diet may constitute an obstacle to the recognition of associated claims.

Enhancement of intragastric acid stability of a fat emulsion meal delays gastric emptying and increases cholecystokinin release and gallbladder contraction

Preprocessed fatty foods often contain calories added as a fat emulsion stabilized by emulsifiers. Emulsion stability in the acidic gastric environment can readily be manipulated by altering emulsifier chemistry. We tested the hypothesis that it would be possible to control gastric emptying, CCK release, and satiety by varying intragastric fat emulsion stability. Nine healthy volunteers received a test meal on two occasions, comprising a 500-ml 15% oil emulsion with 2.5% of one of two emulsifiers that produced emulsions that were either stable (meal A) or unstable (meal B) in the acid gastric environment. Gastric emptying and gallbladder volume changes were assessed by MRI. CCK plasma levels were measured and satiety scores were recorded. Meal B layered rapidly owing to fat emulsion breakdown. The gastric half-emptying time of the aqueous phase was faster for meal B (72 +/- 13 min) than for meal A (171 +/- 35 min, P < 0.008). Meal A released more CCK than meal B (integrated areas, respectively 1,095 +/- 244 and 531 +/- 111 pmol.min.l(-1), P < 0.02), induced a greater gallbladder contraction (P < 0.02), and decreased postprandial appetite (P < 0.05), although no significant differences were observed in fullness and hunger. We conclude that acid-stable emulsions delayed gastric emptying and increased postprandial CCK levels and gallbladder contraction, whereas acid-instability led to rapid layering of fat in the gastric lumen with accelerated gastric emptying, lower CCK levels, and reduced gallbladder contraction. Manipulation of the acid stability of fat emulsion added to preprocessed foods could maximize satiety signaling and, in turn, help to reduce overconsumption of calories.

Appetite signaling: from gut peptides and enteric nerves to brain

The signaling systems underlying eating behavior control are complex. The current review focuses on gastrointestinal (GI) signaling systems as physiological key functions for metabolic control. Many of the peptides that are involved in the regulation of food intake in the brain are also found in the enteric nervous system and enteroendocrine cells of the mucosa of the GI tract. The only identified hunger-driving signal from the GI tract is ghrelin, which is mainly found in the mucosa of the stomach. Neuropeptides in the brain that influence food intake, of which neuropeptide Y, agouti gene-related peptide and orexins are stimulatory, while melanocortins and alpha-melanocortin stimulating hormone are inhibitory, are influenced by peptide signaling from the gut. These effects may take place directly through action of gut peptide in the brain or through nervous signaling from the periphery to the brain. The criteria for considering a gut hormone or neurotransmitter in a satiety signal seem to be fulfilled for cholecystokinin, glucagon-like peptide-1 and peptide YY(3-36). Other endogenous gut signals do not fulfill these criteria as they do not increase food intake in knock-out animals or in response to receptor antagonism, or display an inconsistent temporal profile with satiety and termination of the meal. Satiety signals from the GI tract act through the arcuate nucleus of the hypothalamus and the solitary tract nucleus of the brain stem, where neuronal networks directly linked to hypothalamic centers for food intake and eating behavior are activated. We have primarily focused on GI effects of various gut peptides involved in the regulation of food intake, using motor activity as a biomarker for the understanding of gut peptide effects promoting satiety.

Effect of gastric bypass and gastric banding on proneurotensin levels in morbidly obese patients

CONTEXT

Neurotensin is produced mainly in the N cells of the ileum and has a role in appetite regulation; levels are decreased in obese subjects and increase after bariatric surgery. Mature neurotensin is very unstable, with a short half-life.

OBJECTIVE

The objective of this study was to compare baseline and postoperative levels of the more stable neurotensin precursor, proneurotensin/neuromedin (pro-NT/NMN), in patients after gastric banding, gastric bypass, and nonoperated controls, respectively, during long-term follow-up.

DESIGN AND SETTING

This was a prospective observational study in a university hospital.

PARTICIPANTS AND MAIN OUTCOME MEASURES

Overnight fasting plasma pro-NT/NMN concentrations were measured with a new sandwich immunoassay in morbidly obese subjects at baseline and 6, 12, and 24 months after gastric banding (n = 8), Roux-en-Y gastric bypass (n = 5), and in nonoperated controls (n = 7).

RESULTS

After gastric bypass and banding, body weight decreased by (mean +/- sd) 29.5 +/- 5.5 and 22.8 +/- 5.9 kg, respectively. The decrease after 3 and 6 months was more pronounced after gastric bypass compared with gastric banding (P < 0.05). Plasma pro-NT/NMN levels in patients after gastric bypass increased from 246.3 +/- 174.3 pmol/liter on admission to 748.3 +/- 429.6 pmol/liter after 24 months (P < 0.01). In contrast, in patients with gastric banding, pro-NT/NMN concentrations remained stable (207.3 +/- 60.5 pmol/liter at admission, 226.6 +/- 116.8 pmol/liter after 24 months). Neither body weight nor plasma pro-NT/NMN levels changed in nonoperated controls.

CONCLUSION

Plasma pro-NT/NMN levels show a more pronounced increase after gastric bypass compared with gastric banding, suggesting that specific bariatric surgical procedures result in distinct alterations of gastrointestinal hormone metabolism. The more stable precursor pro-NT/NMN provides a new tool to quantify neurotensin levels in clinical practice.

[Gastric emptying and functional dyspepsia]

Dyspeptic syndrome includes symptoms such as upper abdominal pain, nausea and/or vomiting. These symptoms are common to highly diverse processes such as duodenal ulcer, pancreatitis and even intestinal ischemia, among many others. However, most patients who consult for this syndrome do not have any of these well known processes. New mechanisms have been proposed that could explain the symptoms presented by these patients. Among these mechanisms are those relating to an alteration of normal gastroduodenal motor function, such as alterations of gastric compliance, antral distension, gastric accommodation to anomalous ingestion, and alterations of gastric emptying. The present review evaluates the role of gastric emptying in producing dyspeptic symptoms according to the evidence available to date. We discuss gastric emptying in patients with functional or idiopathic dyspepsia compared with that in the healthy population, the correlation between gastric emptying and dyspeptic symptoms, and the response of dyspeptic symptoms to the prokinetic therapies carried out to date.

Glucagon-related peptide 1 (GLP-1): hormone and neurotransmitter

The interest in glucagon-like petide-1 (GLP-1) and other pre-proglucagon derived peptides has risen almost exponentially since seminal papers in the early 1990s proposed to use GLP-1 agonists as therapeutic agents for treatment of type 2 diabetes. A wealth of interesting studies covering both normal and pathophysiological role of GLP-1 have been published over the last two decades and our understanding of GLP-1 action has widened considerably. In the present review, we have tried to cover our current understanding of GLP-1 actions both as a peripheral hormone and as a central neurotransmitter. From an initial focus on glycaemic control, GLP-1 research has been diverted to study its role in energy homeostasis, neurodegeneration, cognitive functions, anxiety and many more functions. With the upcoming introduction of GLP-1 agonists on the pharmaceutical venue, we have witnessed an outstanding example of how initial ideas from basic science laboratories have paved their way to become a novel therapeutic strategy to fight diabetes.