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      Endogenous GLP-1 mediates postprandial reductions in activation in central reward and satiety areas in patients with type 2 diabetes

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          Abstract

          Aims/hypothesis

          The central nervous system (CNS) is a major player in the regulation of food intake. The gut hormone glucagon-like peptide-1 (GLP-1) has been proposed to have an important role in this regulation by relaying information about nutritional status to the CNS. We hypothesised that endogenous GLP-1 has effects on CNS reward and satiety circuits.

          Methods

          This was a randomised, crossover, placebo-controlled intervention study, performed in a university medical centre in the Netherlands. We included patients with type 2 diabetes and healthy lean control subjects. Individuals were eligible if they were 40–65 years. Inclusion criteria for the healthy lean individuals included a BMI <25 kg/m 2 and normoglycaemia. Inclusion criteria for the patients with type 2 diabetes included BMI >26 kg/m 2, HbA 1c levels between 42 and 69 mmol/mol (6.0–8.5%) and treatment for diabetes with only oral glucose-lowering agents. We assessed CNS activation, defined as blood oxygen level dependent (BOLD) signal, in response to food pictures in obese patients with type 2 diabetes ( n = 20) and healthy lean individuals ( n = 20) using functional magnetic resonance imaging (fMRI). fMRI was performed in the fasted state and after meal intake on two occasions, once during infusion of the GLP-1 receptor antagonist exendin 9-39, which was administered to block actions of endogenous GLP-1, and on the other occasion during saline (placebo) infusion. Participants were blinded for the type of infusion. The order of infusion was determined by block randomisation. The primary outcome was the difference in BOLD signal, i.e. in CNS activation, in predefined regions in the CNS in response to viewing food pictures.

          Results

          All patients were included in the analyses. Patients with type 2 diabetes showed increased CNS activation in CNS areas involved in the regulation of feeding (insula, amygdala and orbitofrontal cortex) in response to food pictures compared with lean individuals ( p ≤ 0.04). Meal intake reduced activation in the insula in response to food pictures in both groups ( p ≤ 0.05), but this was more pronounced in patients with type 2 diabetes. Blocking actions of endogenous GLP-1 significantly prevented meal-induced reductions in bilateral insula activation in response to food pictures in patients with type 2 diabetes ( p ≤ 0.03).

          Conclusions/interpretation

          Our findings support the hypothesis that endogenous GLP-1 is involved in postprandial satiating effects in the CNS of obese patients with type 2 diabetes.

          Trial registration: ClinicalTrials.gov NCT 01363609

          Funding The study was funded in part by a grant from Novo Nordisk.

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          Most cited references37

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          The arcuate nucleus mediates GLP-1 receptor agonist liraglutide-dependent weight loss.

          Liraglutide is a glucagon-like peptide-1 (GLP-1) analog marketed for the treatment of type 2 diabetes. Besides lowering blood glucose, liraglutide also reduces body weight. It is not fully understood how liraglutide induces weight loss or to what degree liraglutide acts directly in the brain. Here, we determined that liraglutide does not activate GLP-1-producing neurons in the hindbrain, and liraglutide-dependent body weight reduction in rats was independent of GLP-1 receptors (GLP-1Rs) in the vagus nerve, area postrema, and paraventricular nucleus. Peripheral injection of fluorescently labeled liraglutide in mice revealed the presence of the drug in the circumventricular organs. Moreover, labeled liraglutide bound neurons within the arcuate nucleus (ARC) and other discrete sites in the hypothalamus. GLP-1R was necessary for liraglutide uptake in the brain, as liraglutide binding was not seen in Glp1r(-/-) mice. In the ARC, liraglutide was internalized in neurons expressing proopiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART). Electrophysiological measurements of murine brain slices revealed that GLP-1 directly stimulates POMC/CART neurons and indirectly inhibits neurotransmission in neurons expressing neuropeptide Y (NPY) and agouti-related peptide (AgRP) via GABA-dependent signaling. Collectively, our findings indicate that the GLP-1R on POMC/CART-expressing ARC neurons likely mediates liraglutide-induced weight loss.
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            Widespread reward-system activation in obese women in response to pictures of high-calorie foods.

            Behavioral studies have suggested that exaggerated reactivity to food cues, especially those associated with high-calorie foods, may be a factor underlying obesity. This increased motivational potency of foods in obese individuals appears to be mediated in part by a hyperactive reward system. We used a Philips 3T magnet and fMRI to investigate activation of reward-system and associated brain structures in response to pictures of high-calorie and low-calorie foods in 12 obese compared to 12 normal-weight women. A regions of interest (ROI) analysis revealed that pictures of high-calorie foods produced significantly greater activation in the obese group compared to controls in medial and lateral orbitofrontal cortex, amygdala, nucleus accumbens/ventral striatum, medial prefrontal cortex, insula, anterior cingulate cortex, ventral pallidum, caudate, putamen, and hippocampus. For the contrast of high-calorie vs. low-calorie foods, the obese group also exhibited a larger difference than the controls did in all of the same regions of interest except for the putamen. Within-group contrasts revealed that pictures of high-calorie foods uniformly stimulated more activation than low-calorie foods did in the obese group. By contrast, in the control group, greater activation by high-calorie foods was seen only in dorsal caudate, whereas low-calorie foods were more effective than high-calorie foods in the lateral orbitofrontal cortex, medial prefrontal cortex, and anterior cingulate cortex. In summary, compared to normal-weight controls, obese women exhibited greater activation in response to pictures of high-calorie foods in a large number of regions hypothesized to mediate motivational effects of food cues.
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              Changes in brain activity related to eating chocolate: from pleasure to aversion.

              D M Small (2001)
              We performed successive H(2)(15)O-PET scans on volunteers as they ate chocolate to beyond satiety. Thus, the sensory stimulus and act (eating) were held constant while the reward value of the chocolate and motivation of the subject to eat were manipulated by feeding. Non-specific effects of satiety (such as feelings of fullness and autonomic changes) were also present and probably contributed to the modulation of brain activity. After eating each piece of chocolate, subjects gave ratings of how pleasant/unpleasant the chocolate was and of how much they did or did not want another piece of chocolate. Regional cerebral blood flow was then regressed against subjects' ratings. Different groups of structures were recruited selectively depending on whether subjects were eating chocolate when they were highly motivated to eat and rated the chocolate as very pleasant [subcallosal region, caudomedial orbitofrontal cortex (OFC), insula/operculum, striatum and midbrain] or whether they ate chocolate despite being satiated (parahippocampal gyrus, caudolateral OFC and prefrontal regions). As predicted, modulation was observed in cortical chemosensory areas, including the insula and caudomedial and caudolateral OFC, suggesting that the reward value of food is represented here. Of particular interest, the medial and lateral caudal OFC showed opposite patterns of activity. This pattern of activity indicates that there may be a functional segregation of the neural representation of reward and punishment within this region. The only brain region that was active during both positive and negative compared with neutral conditions was the posterior cingulate cortex. Therefore, these results support the hypothesis that there are two separate motivational systems: one orchestrating approach and another avoidance behaviours.
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                Author and article information

                Contributors
                js.tenkulve@vumc.nl
                Journal
                Diabetologia
                Diabetologia
                Diabetologia
                Springer Berlin Heidelberg (Berlin/Heidelberg )
                0012-186X
                1432-0428
                18 September 2015
                18 September 2015
                2015
                : 58
                : 12
                : 2688-2698
                Affiliations
                [ ]Department of Internal Medicine, Diabetes Center, VU University Medical Center, de Boelelaan 1117, 1081 HV Amsterdam, the Netherlands
                [ ]Department of Psychiatry, VU University Medical Center, Amsterdam, the Netherlands
                [ ]Department of Radiology and Nuclear Medicine, VU University Medical Center, Amsterdam, the Netherlands
                [ ]The NNF Center for Basic Metabolic Research, Department of Biomedical Sciences, Panum Institute, University of Copenhagen, Copenhagen, Denmark
                [ ]Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN USA
                [ ]Department of Internal Medicine/Endocrine Section, VU University Medical Center, Amsterdam, the Netherlands
                [ ]Department of Clinical Neuropsychology, VU University, Amsterdam, the Netherlands
                Article
                3754
                10.1007/s00125-015-3754-x
                4630252
                26385462
                5826a417-6549-4af1-bb1f-9b9833cfbe43
                © The Author(s) 2015

                Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

                History
                : 3 July 2015
                : 20 August 2015
                Categories
                Article
                Custom metadata
                © Springer-Verlag Berlin Heidelberg 2015

                Endocrinology & Diabetes
                fmri,food intake,glp-1,neuroimaging,obesity,type 2 diabetes
                Endocrinology & Diabetes
                fmri, food intake, glp-1, neuroimaging, obesity, type 2 diabetes

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