Intraduodenal infusion of a combination of tastants decreases food intake in humans

Background: Taste receptors are expressed not only in taste buds but also in the gastrointestinal tract. It has been hypothesized that these receptors may play a role in satiety and food intake. Objective: This study investigated the effect of intraduodenal tastant infusions (bitter, sweet, and umami) on food intake, hunger and fullness, gastrointestinal symptoms, and gastrointestinal peptide release. Design: Fifteen healthy volunteers [6 male; mean ± SEM age: 23.9 ± 2.0 y; mean ± SEM body mass index (in kg/m2): 22.4 ± 0.3] received 5 treatments in a double-blind, randomized, placebo-controlled crossover design. Test days started with the insertion of a nasoduodenal catheter followed by a standardized liquid breakfast. Participants received an intraduodenal infusion 150 min after breakfast, containing quinine (bitter), rebaudioside A (sweet), monosodium glutamate (umami), a combination of the 3 tastants, or placebo (tap water) over a period of 60 min. Food intake was measured during an ad libitum meal, and visual analog scales were used to monitor gastrointestinal complaints and hunger and fullness scores. Blood samples were drawn at regular intervals for cholecystokinin, glucagon-like peptide 1 (GLP-1), and peptide YY (PYY) analysis. Results: Infusion of the combination of tastants substantially decreased food intake (422 ± 97 compared with 486 ± 104 kcal for placebo, P <0.05), whereas both a combination of tastants and umami decreased hunger scores compared with placebo. No change in cholecystokinin, GLP-1, or PYY concentrations was observed during the infusions. Intraduodenal infusions of the tastants did not result in gastrointestinal symptoms. Conclusions: Intraduodenal infusion of umami and a combination of tastants inhibits feelings of hunger, but only the latter also reduces food intake. However, these alterations were not accompanied by changes in the plasma concentrations of the gut-derived peptides cholecystokinin, GLP-1, or PYY. This trial was registered at clinicaltrials.gov as NCT01956838.</p

Effects of mood inductions by meal ambiance and moderate alcohol consumption on endocannabinoids and N-acylethanolamines in humans: a randomized crossover trial.

BackgroundThe endocannabinoid system is suggested to play a regulatory role in mood. However, the response of circulating endocannabinoids (ECs) to mood changes has never been tested in humans. In the present study, we examined the effects of mood changes induced by ambiance and moderate alcohol consumption on plasma ECs 2-arachidonoylglycerol (2-AG), anandamide (AEA), and some N-acylethanolamine (NAE) congeners in humans.MethodsHealthy women (n = 28) participated in a randomized cross-over study. They consumed sparkling white wine (340 mL; 30 g alcohol) or alcohol-free sparkling white wine (340 mL; ResultsPlasma concentrations of palmitoylethanolamide (PEA) and stearoylethanolamide (SEA) increased after 30 min in the unpleasant ambiance, while they decreased in the pleasant ambiance. Changes in ECs and their NAE congeners correlated with mood states, such as happiness and fatigue, but in the pleasant ambiance without alcohol only. ECs and their NAE congeners were correlated with serum free fatty acids and cortisol.ConclusionThis is the first human study to demonstrate that plasma NAEs are responsive to an unpleasant meal ambiance. Furthermore, associations between mood states and ECs and their NAE congeners were observed.Trial registrationClinicaltrials.gov NCT01426022

Nutrient-induced glucagon like peptide-1 release is modulated by serotonin

Glucagon like peptide-1 (GLP-1) and serotonin are both involved in food intake regulation. GLP-1 release is stimulated upon nutrient interaction with G-protein coupled receptors by enteroendocrine cells (EEC), whereas serotonin is released from enterochromaffin cells (ECC). The central hypothesis for the current study was that nutrient-induced GLP-1 release from EECs is modulated by serotonin through a process involving serotonin receptor interaction. This was studied by assessing the effects of serotonin reuptake inhibition by fluoxetine on nutrient-induced GLP-1, PYY and CCK release from isolated pig intestinal segments. Next, serotonin-induced GLP-1 release was studied in enteroendocrine STC-1 cells, where effects of serotonin receptor inhibition were studied using specific and non-specific antagonists.Casein (1% w/v), safflower oil (3.35% w/v), sucrose (50 mM) and rebaudioside A (12.5 mM) stimulated GLP-1 release from intestinal segments, whereas casein only stimulated PYY and CCK release. Combining nutrients with fluoxetine further increased nutrient-induced GLP-1, PYY and CCK release.Serotonin release from intestinal tissue segments was stimulated by casein and safflower oil while sucrose and rebaudioside A had no effect. The combination with fluoxetine (0.155 μM) further enhanced casein and safflower oil induced-serotonin release.Exposure of ileal tissue segments to serotonin (30 μM) stimulated GLP-1 release whereas it did not induce PYY and CCK release. Serotonin (30 and 100 μM) also stimulated GLP-1 release from STC-1 cells, which was inhibited by the non-specific 5HT receptor antagonist asenapine (1 and 10 μM). These data suggest that nutrient-induced GLP-1 release is modulated by serotonin through a receptor mediated process.</p

Postprandial changes in (A) serum free fatty acid and (B) cortisol after mood inductions.

<p>White bars represent pleasant ambiance with alcohol; grey bars represent unpleasant ambaince with alcohol; black bars represent pleasant ambiance without alcohol; striped bars represent unpleasant ambiance without alcohol. Cortisol concentration is more decreased 120 min after a meal with alcohol than without alcohol (*<i>P</i> = 0.001). n = 28.</p

Changes in endocannabinoids and <i>N</i>-acylethanolamines after mood inductions by ambiance and moderate alcohol consumption.

<p>(A) 2-arachidonoylglycerol (2-AG), (B) anandamide (AEA) and related compounds (C) palmitoylethanolamide (PEA) and (D) stearoylethanolamide (SEA). Black bars represent pleasant ambiance with alcohol; white bars represent pleasant ambiance without alcohol; grey bars represent unpleasant ambiance with alcohol; striped bars represent unpleasant ambiance without alcohol. PEA and SEA concentrations are increased 30 min after a meal in the unpleasant ambiance, but decreased after a meal in the unpleasant ambiance (*<i>P</i> = 0.073; ** <i>P</i> = 0.036). n = 16.</p

Flow chart (CONSORT).

<p>Adapted from Schrieks et al. (2014) [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0126421#pone.0126421.ref026" target="_blank">26</a>] under a CC BY license, with permission from PLOS ONE, original copyright 2014.</p