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Staltner R, Burger K, Baumann A, Bergheim I. Fructose: a modulator of intestinal barrier function and hepatic health? Eur J Nutr 2023; 62:3113-3124. [PMID: 37596353 PMCID: PMC10611622 DOI: 10.1007/s00394-023-03232-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Accepted: 08/04/2023] [Indexed: 08/20/2023]
Abstract
PURPOSE Consumption of fructose has repeatedly been discussed to be a key factor in the development of health disturbances such as hypertension, diabetes type 2, and non-alcoholic fatty liver disease. Despite intense research efforts, the question if and how high dietary fructose intake interferes with human health has not yet been fully answered. RESULTS Studies suggest that besides its insulin-independent metabolism dietary fructose may also impact intestinal homeostasis and barrier function. Indeed, it has been suggested by the results of human and animal as well as in vitro studies that fructose enriched diets may alter intestinal microbiota composition. Furthermore, studies have also shown that both acute and chronic intake of fructose may lead to an increased formation of nitric oxide and a loss of tight junction proteins in small intestinal tissue. These alterations have been related to an increased translocation of pathogen-associated molecular patterns (PAMPs) like bacterial endotoxin and an induction of dependent signaling cascades in the liver but also other tissues. CONCLUSION In the present narrative review, results of studies assessing the effects of fructose on intestinal barrier function and their impact on the development of health disturbances with a particular focus on the liver are summarized and discussed.
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Affiliation(s)
- Raphaela Staltner
- Department of Nutritional Sciences, Molecular Nutritional Science, University of Vienna, Josef-Holaubek-Platz 2, A-1090, Vienna, Austria
| | - Katharina Burger
- Department of Nutritional Sciences, Molecular Nutritional Science, University of Vienna, Josef-Holaubek-Platz 2, A-1090, Vienna, Austria
| | - Anja Baumann
- Department of Nutritional Sciences, Molecular Nutritional Science, University of Vienna, Josef-Holaubek-Platz 2, A-1090, Vienna, Austria
| | - Ina Bergheim
- Department of Nutritional Sciences, Molecular Nutritional Science, University of Vienna, Josef-Holaubek-Platz 2, A-1090, Vienna, Austria.
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2
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Sundaresan S, Johnson C, Dixon KB, Dole M, Kilkelly D, Antoun J, Flynn CR, Abumrad NN, Tamboli R. Intraduodenal nutrient infusion differentially alters intestinal nutrient sensing, appetite, and satiety responses in lean and obese subjects. Am J Clin Nutr 2023; 118:646-656. [PMID: 37661107 PMCID: PMC10517208 DOI: 10.1016/j.ajcnut.2023.06.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 06/02/2023] [Accepted: 06/12/2023] [Indexed: 09/05/2023] Open
Abstract
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.
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Affiliation(s)
- Sinju Sundaresan
- Department of Physiology, Midwestern University, Downers Grove, IL; Department of Surgery, Vanderbilt University Medical Center, Nashville, TN.
| | - Connor Johnson
- Department of Surgery, Vanderbilt University Medical Center, Nashville, TN
| | - Kala B Dixon
- Department of Surgery, Vanderbilt University Medical Center, Nashville, TN
| | - Michael Dole
- Department of Surgery, Vanderbilt University Medical Center, Nashville, TN
| | - Donna Kilkelly
- Department of Surgery, Vanderbilt University Medical Center, Nashville, TN
| | - Joseph Antoun
- Department of Surgery, Vanderbilt University Medical Center, Nashville, TN
| | - Charles Robb Flynn
- Department of Surgery, Vanderbilt University Medical Center, Nashville, TN
| | - Naji N Abumrad
- Department of Surgery, Vanderbilt University Medical Center, Nashville, TN
| | - Robyn Tamboli
- Department of Surgery, Vanderbilt University Medical Center, Nashville, TN
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Wilbrink J, Masclee G, Klaassen T, van Avesaat M, Keszthelyi D, Masclee A. Review on the Regional Effects of Gastrointestinal Luminal Stimulation on Appetite and Energy Intake: (Pre)clinical Observations. Nutrients 2021; 13:nu13051601. [PMID: 34064724 PMCID: PMC8151500 DOI: 10.3390/nu13051601] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 04/22/2021] [Accepted: 05/05/2021] [Indexed: 02/06/2023] Open
Abstract
Macronutrients in the gastrointestinal (GI) lumen are able to activate “intestinal brakes”, feedback mechanisms on proximal GI motility and secretion including appetite and energy intake. In this review, we provide a detailed overview of the current evidence with respect to four questions: (1) are regional differences (duodenum, jejunum, ileum) present in the intestinal luminal nutrient modulation of appetite and energy intake? (2) is this “intestinal brake” effect macronutrient specific? (3) is this “intestinal brake” effect maintained during repetitive activation? (4) can the “intestinal brake” effect be activated via non-caloric tastants? Recent evidence indicates that: (1) regional differences exist in the intestinal modulation of appetite and energy intake with a proximal to distal gradient for inhibition of energy intake: ileum and jejunum > duodenum at low but not at high caloric infusion rates. (2) the “intestinal brake” effect on appetite and energy appears not to be macronutrient specific. At equi-caloric amounts, the inhibition on energy intake and appetite is in the same range for fat, protein and carbohydrate. (3) data on repetitive ileal brake activation are scarce because of the need for prolonged intestinal intubation. During repetitive activation of the ileal brake for up to 4 days, no adaptation was observed but overall the inhibitory effect on energy intake was small. (4) the concept of influencing energy intake by intra-intestinal delivery of non-caloric tastants is intriguing. Among tastants, the bitter compounds appear to be more effective in influencing energy intake. Energy intake decreases modestly after post-oral delivery of bitter tastants or a combination of tastants (bitter, sweet and umami). Intestinal brake activation provides an interesting concept for preventive and therapeutic approaches in weight management strategies.
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Affiliation(s)
- Jennifer Wilbrink
- Division of Gastroenterology-Hepatology, Maastricht University Medical Center, 6229 HX Maastricht, The Netherlands; (J.W.); (G.M.); (T.K.); (M.v.A.); (D.K.)
| | - Gwen Masclee
- Division of Gastroenterology-Hepatology, Maastricht University Medical Center, 6229 HX Maastricht, The Netherlands; (J.W.); (G.M.); (T.K.); (M.v.A.); (D.K.)
| | - Tim Klaassen
- Division of Gastroenterology-Hepatology, Maastricht University Medical Center, 6229 HX Maastricht, The Netherlands; (J.W.); (G.M.); (T.K.); (M.v.A.); (D.K.)
| | - Mark van Avesaat
- Division of Gastroenterology-Hepatology, Maastricht University Medical Center, 6229 HX Maastricht, The Netherlands; (J.W.); (G.M.); (T.K.); (M.v.A.); (D.K.)
| | - Daniel Keszthelyi
- Division of Gastroenterology-Hepatology, Maastricht University Medical Center, 6229 HX Maastricht, The Netherlands; (J.W.); (G.M.); (T.K.); (M.v.A.); (D.K.)
- NUTRIM School of Nutrition and Translational Research in Metabolism, 6229 ER Maastricht, The Netherlands
| | - Adrian Masclee
- Division of Gastroenterology-Hepatology, Maastricht University Medical Center, 6229 HX Maastricht, The Netherlands; (J.W.); (G.M.); (T.K.); (M.v.A.); (D.K.)
- NUTRIM School of Nutrition and Translational Research in Metabolism, 6229 ER Maastricht, The Netherlands
- Correspondence: ; Tel.: +31-43-3875021
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4
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Lu VB, Gribble FM, Reimann F. Nutrient-Induced Cellular Mechanisms of Gut Hormone Secretion. Nutrients 2021; 13:nu13030883. [PMID: 33803183 PMCID: PMC8000029 DOI: 10.3390/nu13030883] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 02/27/2021] [Accepted: 03/05/2021] [Indexed: 02/06/2023] Open
Abstract
The gastrointestinal tract can assess the nutrient composition of ingested food. The nutrient-sensing mechanisms in specialised epithelial cells lining the gastrointestinal tract, the enteroendocrine cells, trigger the release of gut hormones that provide important local and central feedback signals to regulate nutrient utilisation and feeding behaviour. The evidence for nutrient-stimulated secretion of two of the most studied gut hormones, glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), along with the known cellular mechanisms in enteroendocrine cells recruited by nutrients, will be the focus of this review. The mechanisms involved range from electrogenic transporters, ion channel modulation and nutrient-activated G-protein coupled receptors that converge on the release machinery controlling hormone secretion. Elucidation of these mechanisms will provide much needed insight into postprandial physiology and identify tractable dietary approaches to potentially manage nutrition and satiety by altering the secreted gut hormone profile.
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5
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Hens B, Masuy I, Deloose E, Mols R, Tack J, Augustijns P. Exploring the impact of real-life dosing conditions on intraluminal and systemic concentrations of atazanavir in parallel with gastric motility recording in healthy subjects. Eur J Pharm Biopharm 2020; 150:66-76. [PMID: 32113916 DOI: 10.1016/j.ejpb.2020.02.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 02/21/2020] [Accepted: 02/25/2020] [Indexed: 02/07/2023]
Abstract
This work strived to explore gastrointestinal (GI) dissolution, supersaturation and precipitation of the weakly basic drug atazanavir in humans under different 'real-life' intake conditions. The impact of GI pH and motility on these processes was thoroughly explored. In a cross-over study, atazanavir (Reyataz®) was orally administered to 5 healthy subjects with (i) a glass of water, (ii) a glass of Coca-Cola® and (iii) a glass of water under hypochlorhydric conditions (induced by concomitant intake of a proton-pump inhibitor (PPI)). After intake, GI fluids were aspirated from the stomach and the duodenum and, subsequently, analyzed for atazanavir. In parallel, blood samples were collected to assess systemic concentrations. In general, the results of this study revealed that the acidic gastric pH in combination with gastric residence time played a crucial role in the dissolution of atazanavir along the GI tract. After intake of atazanavir with a glass of water (i.e., reference condition), complete gastric dissolution was observed. After GI transfer, supersaturation was noticed for a limited amount of time (1.25 h). With respect to the Coca-Cola® condition, complete gastric dissolution was also observed. A delay in gastric emptying, highly likely caused by the caloric content (101 kcal), was responsible for delayed arrival of atazanavir into the upper small intestine, creating a longer time window of supersaturated concentrations in the duodenal segment (3.25 h) compared to the water condition. The longer period of supersaturated concentrations resulted in a slightly higher systemic exposure of atazanavir compared to the condition when atazanavir was taken with a glass of water. A remarkable observation was the creation (when the drug was given in the migrating motor complex (MMC) phase 2) or maintenance (when the drug was given in MMC phase 1) of a quiescent phase for up to 80 min. With respect to the PPI condition, negligible gastric and intestinal concentrations were observed, resulting in minimal systemic exposure for all subjects. It can be concluded that gastric pH and residence time play a pivotal role in the intestinal disposition of atazanavir in order to generate sufficiently high concentrations further down in the intestinal tract for a sufficient period of time, thus creating a beneficial driving force for intestinal absorption.
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Affiliation(s)
- Bart Hens
- Drug Delivery and Disposition, KU Leuven, Leuven, Belgium
| | - Imke Masuy
- Translational Research Center for Gastrointestinal Disorders (TARGID), KU Leuven, Leuven, Belgium
| | - Eveline Deloose
- Translational Research Center for Gastrointestinal Disorders (TARGID), KU Leuven, Leuven, Belgium
| | - Raf Mols
- Drug Delivery and Disposition, KU Leuven, Leuven, Belgium
| | - Jan Tack
- Translational Research Center for Gastrointestinal Disorders (TARGID), KU Leuven, Leuven, Belgium
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6
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Gasbjerg LS, Bergmann NC, Stensen S, Christensen MB, Rosenkilde MM, Holst JJ, Nauck M, Knop FK. Evaluation of the incretin effect in humans using GIP and GLP-1 receptor antagonists. Peptides 2020; 125:170183. [PMID: 31693916 DOI: 10.1016/j.peptides.2019.170183] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 10/22/2019] [Accepted: 10/24/2019] [Indexed: 02/07/2023]
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) potentiate glucose-induced insulin secretion and are therefore thought to be responsible for the incretin effect. The magnitude of the incretin effect, defined as the fraction of postprandial insulin secretion stimulated by intestinal factors, has been reported to be up to ∼60% in healthy individuals. In several pathological conditions but especially in patients with type 2 diabetes, the incretin effect is severely reduced or even absent. In line with this, the insulinotropic effects of GIP and GLP-1 are impaired in patients with type 2 diabetes, even when administered in supraphysiological doses. In healthy individuals, GIP has been proposed to be the most important incretin hormone of the two, but the individual contribution of the two is difficult to determine. However, using incretin hormone receptor antagonists: the novel GIP receptor antagonist GIP(3-30)NH2 and the widely used GLP-1 receptor antagonist exendin(9-39)NH2, we can now distinguish between the effects of the two hormones. In this review, we present and discuss studies in which the individual contribution of GIP and GLP-1 to the incretin effect in healthy individuals have been estimated and discuss the limitations of using incretin hormone receptor antagonists.
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Affiliation(s)
- Lærke S Gasbjerg
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark; Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
| | - Natasha C Bergmann
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark
| | - Signe Stensen
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark
| | - Mikkel B Christensen
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark; Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; Department of Clinical Pharmacology, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark
| | - Mette M Rosenkilde
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jens J Holst
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Michael Nauck
- Diabetes Division, St. Josef Hospital, Ruhr-University Bochum, Bochum, Germany
| | - Filip K Knop
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark; Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; Steno Diabetes Center Copenhagen, Gentofte, Denmark
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7
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Meyer-Gerspach AC, Biesiekierski JR, Deloose E, Clevers E, Rotondo A, Rehfeld JF, Depoortere I, Van Oudenhove L, Tack J. Effects of caloric and noncaloric sweeteners on antroduodenal motility, gastrointestinal hormone secretion and appetite-related sensations in healthy subjects. Am J Clin Nutr 2018; 107:707-716. [DOI: 10.1093/ajcn/nqy004] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Accepted: 12/26/2017] [Indexed: 12/11/2022] Open
Affiliation(s)
- Anne Christin Meyer-Gerspach
- Translational Research Center for Gastrointestinal Disorders, Catholic University of Leuven, Leuven, Belgium
- Department of Research, Clara Hospital, Basel, Switzerland
| | - Jessica R Biesiekierski
- Translational Research Center for Gastrointestinal Disorders, Catholic University of Leuven, Leuven, Belgium
| | - Eveline Deloose
- Translational Research Center for Gastrointestinal Disorders, Catholic University of Leuven, Leuven, Belgium
| | - Egbert Clevers
- Translational Research Center for Gastrointestinal Disorders, Catholic University of Leuven, Leuven, Belgium
| | - Alessandra Rotondo
- Translational Research Center for Gastrointestinal Disorders, Catholic University of Leuven, Leuven, Belgium
| | - Jens F Rehfeld
- Department of Clinical Biochemistry, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Inge Depoortere
- Translational Research Center for Gastrointestinal Disorders, Catholic University of Leuven, Leuven, Belgium
| | - Lukas Van Oudenhove
- Translational Research Center for Gastrointestinal Disorders, Catholic University of Leuven, Leuven, Belgium
| | - Jan Tack
- Translational Research Center for Gastrointestinal Disorders, Catholic University of Leuven, Leuven, Belgium
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8
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Human GIP(3-30)NH 2 inhibits G protein-dependent as well as G protein-independent signaling and is selective for the GIP receptor with high-affinity binding to primate but not rodent GIP receptors. Biochem Pharmacol 2018; 150:97-107. [PMID: 29378179 DOI: 10.1016/j.bcp.2018.01.040] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 01/22/2018] [Indexed: 12/21/2022]
Abstract
GIP(3-30)NH2 is a high affinity antagonist of the GIP receptor (GIPR) in humans inhibiting insulin secretion via G protein-dependent pathways. However, its ability to inhibit G protein-independent signaling is unknown. Here we determine its action on arrestin-recruitment and receptor internalization in recombinant cells. As GIP is adipogenic, we evaluate the inhibitory actions of GIP(3-30)NH2 in human adipocytes. Finally, we determine the receptor selectivity of GIP(3-30)NH2 among other human and animal GPCRs. cAMP accumulation and β-arrestin 1 and 2 recruitment were studied in transiently transfected HEK293 cells and real-time internalization in transiently transfected HEK293A and in HEK293A β-arrestin 1 and 2 knockout cells. Furthermore, human subcutaneous adipocytes were assessed for cAMP accumulation following ligand stimulation. Competition binding was examined in transiently transfected COS-7 cells using human 125I-GIP(3-30)NH2. The selectivity of human GIP(3-30)NH2 was examined by testing for agonistic and antagonistic properties on 62 human GPCRs. Human GIP(3-30)NH2 inhibited GIP(1-42)-induced cAMP and β-arrestin 1 and 2 recruitment on the human GIPR and Schild plot analysis showed competitive antagonism with a pA2 and Hill slope of 16.8 nM and 1.11 ± 0.02 in cAMP, 10.6 nM and 1.15 ± 0.05 in β-arrestin 1 recruitment, and 10.2 nM and 1.06 ± 0.05 in β-arrestin 2 recruitment. Efficient internalization of the GIPR was dependent on the presence of either β-arrestin 1 or 2. Moreover, GIP(3-30)NH2 inhibited GIP(1-42)-induced internalization in a concentration-dependent manner and notably also inhibited GIP-mediated signaling in human subcutaneous adipocytes. Finally, the antagonist was established as GIPR selective among 62 human GPCRs being species-specific with high affinity binding to the human and non-human primate (Macaca fascicularis) GIPRs, and low affinity binding to the rat and mouse GIPRs (Kd values of 2.0, 2.5, 31.6 and 100 nM, respectively). In conclusion, human GIP(3-30)NH2 is a selective and species-specific GIPR antagonist with broad inhibition of signaling and internalization in transfected cells as well as in human adipocytes.
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9
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Martin AM, Lumsden AL, Young RL, Jessup CF, Spencer NJ, Keating DJ. Regional differences in nutrient-induced secretion of gut serotonin. Physiol Rep 2017; 5:5/6/e13199. [PMID: 28320893 PMCID: PMC5371566 DOI: 10.14814/phy2.13199] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 02/15/2017] [Accepted: 02/16/2017] [Indexed: 12/17/2022] Open
Abstract
Enterochromaffin (EC) cells located in the gastrointestinal (GI) tract provide the vast majority of serotonin (5-HT) in the body and constitute half of all enteroendocrine cells. EC cells respond to an array of stimuli, including various ingested nutrients. Ensuing 5-HT release from these cells plays a diverse role in regulating gut motility as well as other important responses to nutrient ingestion such as glucose absorption and fluid balance. Recent data also highlight the role of peripheral 5-HT in various pathways related to metabolic control. Details related to the manner by which EC cells respond to ingested nutrients are scarce and as that the nutrient environment changes along the length of the gut, it is unknown whether the response of EC cells to nutrients is dependent on their GI location. The aim of the present study was to identify whether regional differences in nutrient sensing capability exist in mouse EC cells. We isolated mouse EC cells from duodenum and colon to demonstrate differential responses to sugars depending on location. Measurements of intracellular calcium concentration and 5-HT secretion demonstrated that colonic EC cells are more sensitive to glucose, while duodenal EC cells are more sensitive to fructose and sucrose. Short-chain fatty acids (SCFAs), which are predominantly synthesized by intestinal bacteria, have been previously associated with an increase in circulating 5-HT; however, we find that SCFAs do not acutely stimulate EC cell 5-HT release. Thus, we highlight that EC cell physiology is dictated by regional location within the GI tract, and identify differences in the regional responsiveness of EC cells to dietary sugars.
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Affiliation(s)
- Alyce M Martin
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Amanda L Lumsden
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Richard L Young
- South Australian Health and Medical Research Institute (SAHMRI), Adelaide, Australia.,Adelaide Medical School, University of Adelaide, Adelaide, Australia
| | - Claire F Jessup
- Department of Anatomy and Histology and Centre for Neuroscience, Flinders University, Adelaide, Australia.,Adelaide Medical School, University of Adelaide, Adelaide, Australia
| | - Nick J Spencer
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Damien J Keating
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia .,South Australian Health and Medical Research Institute (SAHMRI), Adelaide, Australia
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10
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Kaliora AC, Kanellos PT, Gioxari A, Karathanos VT. Regulation of GIP and Ghrelin in Healthy Subjects Fed on Sun-Dried Raisins: A Pilot Study with a Crossover Trial Design. J Med Food 2017; 20:301-308. [PMID: 28170279 DOI: 10.1089/jmf.2016.0123] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The comparative effects of glucose and fructose on appetite and specifically on hormones regulating appetite remain controversial, and the role of different types of sugars has not been investigated broadly. To estimate the effect of raisins, a dried fruit rich in fructose, fibers, and phenolics, on hormones involved in the postprandial response. Ten healthy normal-weight subjects received in a crossover design 74 g raisins or 50 g glucose as reference food. Glucose, insulin, and appetite hormones were measured at time 0 and 60, 120, and 180 min after consumption. Glucose and insulin peaked significantly at 60 min in both trials with no difference in two trials. Gastric inhibitory peptide peaked significantly at 60 min in both trials and was found lower in raisin compared to glucose at 60 and 120 min postprandially. Ghrelin was lower in raisin compared to glucose at 120 and at 180 min postingestion. Ghrelin/obestatin ratio was lower at 120 min in raisin compared to glucose. No differences were reported for glucagon-like peptide-1, apelin, and obestatin in either trial. Raisin consumption could be favorable in terms of regulating appetite compared to refined sugars or glucose-based products in normal-weight healthy subjects.
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Affiliation(s)
- Andriana C Kaliora
- Department of Dietetics and Nutritional Science, School of Health Science and Education, Harokopio University , Athens, Greece
| | - Panagiotis T Kanellos
- Department of Dietetics and Nutritional Science, School of Health Science and Education, Harokopio University , Athens, Greece
| | - Aristea Gioxari
- Department of Dietetics and Nutritional Science, School of Health Science and Education, Harokopio University , Athens, Greece
| | - Vaios T Karathanos
- Department of Dietetics and Nutritional Science, School of Health Science and Education, Harokopio University , Athens, Greece
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11
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Moghadam AA, Moran TH, Dailey MJ. Jejunal Infusion of Glucose Decreases Energy Intake to a Greater Extent than Fructose in Adult Male Rats. J Nutr 2016; 146:2124-2128. [PMID: 27581579 PMCID: PMC5037871 DOI: 10.3945/jn.116.231860] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Accepted: 08/04/2016] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Intestinal nutrient infusions result in variable decreases in energy intake and body weight based on nutrient type and specific intestinal infusion site. OBJECTIVE The objective was to test whether an intrajejunal fructose infusion (FRU) would lower energy intake and body weight and induce similar increases in gut hormones as those found after intrajejunal glucose infusions (GLU). METHODS Male Sprague-Dawley rats received an intrajejunal infusion of either an equal kilocalorie load of glucose or fructose (11.4 kcal) or saline (SAL) for 5 d while intake of a standard rodent diet was continuously recorded; body weight was measured daily. Immediately after the infusion on the final day, rats were killed and plasma was collected to measure hormones. RESULTS Daily energy intake was significantly lower in the GLU group than in the SAL group, but the FRU group did not differ from the GLU or SAL groups when the 11.4 kcal of the infusate was included as energy intake. Lower energy intake was due to smaller meal sizes during the infusion period in the GLU group than in the FRU and SAL groups; the FRU and SAL groups did not differ. The percentage of change in body weight was lower in the GLU group than in the FRU and SAL groups. Plasma glucagon-like-peptide 1 (GLP-1) concentrations were greater in the GLU group than in the SAL group; the FRU group did not differ from the GLU or SAL groups. The plasma insulin concentration was greater in the FRU group than in both the GLU and SAL groups. CONCLUSION These results demonstrate that glucose induces a greater decrease in energy intake and increase in GLP-1 at distal intestinal sites than fructose in rats, which may explain differential effects of these monosaccharides between studies when delivered orally or along the proximal to distal axis of the intestine.
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Affiliation(s)
- Alexander A Moghadam
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University, Baltimore MD; and
| | - Timothy H Moran
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University, Baltimore MD; and
| | - Megan J Dailey
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL
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13
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Alleleyn AME, van Avesaat M, Troost FJ, Masclee AAM. Gastrointestinal Nutrient Infusion Site and Eating Behavior: Evidence for A Proximal to Distal Gradient within the Small Intestine? Nutrients 2016; 8:117. [PMID: 26927170 PMCID: PMC4808847 DOI: 10.3390/nu8030117] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 02/16/2016] [Accepted: 02/19/2016] [Indexed: 12/23/2022] Open
Abstract
The rapidly increasing prevalence of overweight and obesity demands new strategies focusing on prevention and treatment of this significant health care problem. In the search for new and effective therapeutic modalities for overweight subjects, the gastrointestinal (GI) tract is increasingly considered as an attractive target for medical and food-based strategies. The entry of nutrients into the small intestine activates so-called intestinal "brakes", negative feedback mechanisms that influence not only functions of more proximal parts of the GI tract but also satiety and food intake. Recent evidence suggests that all three macronutrients (protein, fat, and carbohydrates) are able to activate the intestinal brake, although to a different extent and by different mechanisms of action. This review provides a detailed overview of the current evidence for intestinal brake activation of the three macronutrients and their effects on GI function, satiety, and food intake. In addition, these effects appear to depend on region and length of infusion in the small intestine. A recommendation for a therapeutic approach is provided, based on the observed differences between intestinal brake activation.
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Affiliation(s)
- Annick M E Alleleyn
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, P.O. Box 5800, 6202 AZ Maastricht, The Netherlands.
| | - Mark van Avesaat
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, P.O. Box 5800, 6202 AZ Maastricht, The Netherlands.
- Top Institute of Food and Nutrition, 6700 AN Wageningen, The Netherlands.
| | - Freddy J Troost
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, P.O. Box 5800, 6202 AZ Maastricht, The Netherlands.
- Top Institute of Food and Nutrition, 6700 AN Wageningen, The Netherlands.
| | - Adrian A M Masclee
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, P.O. Box 5800, 6202 AZ Maastricht, The Netherlands.
- Top Institute of Food and Nutrition, 6700 AN Wageningen, The Netherlands.
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Dietary sugars: their detection by the gut-brain axis and their peripheral and central effects in health and diseases. Eur J Nutr 2014; 54:1-24. [PMID: 25296886 PMCID: PMC4303703 DOI: 10.1007/s00394-014-0776-y] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Accepted: 09/24/2014] [Indexed: 12/25/2022]
Abstract
Background Substantial increases in dietary sugar intake together with the increasing prevalence of obesity worldwide, as well as the parallels found between sugar overconsumption and drug abuse, have motivated research on the adverse effects of sugars on health and eating behaviour. Given that the gut–brain axis depends on multiple interactions between peripheral and central signals, and because these signals are interdependent, it is crucial to have a holistic view about dietary sugar effects on health. Methods Recent data on the effects of dietary sugars (i.e. sucrose, glucose, and fructose) at both peripheral and central levels and their interactions will be critically discussed in order to improve our understanding of the effects of sugars on health and diseases. This will contribute to the development of more efficient strategies for the prevention and treatment for obesity and associated co-morbidities. Results This review highlights opposing effects of glucose and fructose on metabolism and eating behaviour. Peripheral glucose and fructose sensing may influence eating behaviour by sweet-tasting mechanisms in the mouth and gut, and by glucose-sensing mechanisms in the gut. Glucose may impact brain reward regions and eating behaviour directly by crossing the blood–brain barrier, and indirectly by peripheral neural input and by oral and intestinal sweet taste/sugar-sensing mechanisms, whereas those promoted by fructose orally ingested seem to rely only on these indirect mechanisms. Conclusions Given the discrepancies between studies regarding the metabolic effects of sugars, more studies using physiological experimental conditions and in animal models closer to humans are needed. Additional studies directly comparing the effects of sucrose, glucose, and fructose should be performed to elucidate possible differences between these sugars on the reward circuitry.
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Thazhath SS, Wu T, Young RL, Horowitz M, Rayner CK. Glucose absorption in small intestinal diseases. Expert Rev Gastroenterol Hepatol 2014; 8:301-12. [PMID: 24502537 DOI: 10.1586/17474124.2014.887439] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Recent developments in the field of diabetes and obesity management have established the central role of the gut in glucose homeostasis; not only is the gut the primary absorptive site, but it also triggers neurohumoral feedback responses that regulate the pre- and post-absorptive phases of glucose metabolism. Structural and/or functional disorders of the intestine have the capacity to enhance (e.g.: diabetes) or inhibit (e.g.: short-gut syndrome, critical illness) glucose absorption, with potentially detrimental outcomes. In this review, we first describe the normal physiology of glucose absorption and outline the methods by which it can be quantified. Then we focus on the structural and functional changes in the small intestine associated with obesity, critical illness, short gut syndrome and other malabsorptive states, and particularly Type 2 diabetes, which can impact upon carbohydrate absorption and overall glucose homeostasis.
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Affiliation(s)
- Sony S Thazhath
- Discipline of Medicine, The University of Adelaide, Royal Adelaide Hospital, Adelaide, SA, Australia
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16
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Browning KN. Modulation of gastrointestinal vagal neurocircuits by hyperglycemia. Front Neurosci 2013; 7:217. [PMID: 24324393 PMCID: PMC3840437 DOI: 10.3389/fnins.2013.00217] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Accepted: 10/30/2013] [Indexed: 12/17/2022] Open
Abstract
Glucose sensing within autonomic neurocircuits is critical for the effective integration and regulation of a variety of physiological homeostatic functions including the co-ordination of vagally-mediated reflexes regulating gastrointestinal (GI) functions. Glucose regulates GI functions via actions at multiple sites of action, from modulating the activity of enteric neurons, endocrine cells, and glucose transporters within the intestine, to regulating the activity and responsiveness of the peripheral terminals, cell bodies and central terminals of vagal sensory neurons, to modifying both the activity and synaptic responsiveness of central brainstem neurons. Unsurprisingly, significant impairment in GI functions occurs in pathophysiological states where glucose levels are dysregulated, such as diabetes. A substantial obstacle to the development of new therapies to modify the disease, rather than treat the symptoms, are the gaps in our understanding of the mechanisms by which glucose modulates GI functions, particularly vagally-mediated responses and a more complete understanding of disease-related plasticity within these neurocircuits may open new avenues and targets for research.
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Affiliation(s)
- Kirsteen N Browning
- Department of Neural and Behavioral Sciences, Penn State College of Medicine Hershey, PA, USA
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17
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Shin HS, Ingram JR, McGill AT, Poppitt SD. Lipids, CHOs, proteins: can all macronutrients put a 'brake' on eating? Physiol Behav 2013; 120:114-23. [PMID: 23911804 DOI: 10.1016/j.physbeh.2013.07.008] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Revised: 01/09/2013] [Accepted: 07/23/2013] [Indexed: 01/18/2023]
Abstract
The gastrointestinal (GI) tract and specifically the most distal part of the small intestine, the ileum, has become a renewed focus of interest for mechanisms targeting appetite suppression. The 'ileal brake' is stimulated when energy-containing nutrients are delivered beyond the duodenum and jejunum and into the ileum, and is named for the feedback loop which slows or 'brakes' gastric emptying and duodeno-jejunal motility. More recently it has been hypothesized that the ileal brake also promotes secretion of satiety-enhancing GI peptides and suppresses hunger, placing a 'brake' on food intake. Postprandial delivery of macronutrients to the ileum, other than unavailable carbohydrates (CHO) which bypass absorption in the small intestine en route to fermentation in the large bowel, is an uncommon event and hence this brake mechanism is rarely activated following a meal. However the ability to place a 'brake' on food intake through delivery of protected nutrients to the ileum is both intriguing and challenging. This review summarizes the current clinical and experimental evidence for activation of the ileal brake by the three food macronutrients, with emphasis on eating behavior and satiety as well as GI function. While clinical studies have shown that exposure of the ileum to lipids, CHOs and proteins may activate GI components of the ileal brake, such as decreased gut motility, gastric emptying and secretion of GI peptides, there is less evidence as yet to support a causal relationship between activation of the GI brake by these macronutrients and the suppression of food intake. The predominance of evidence for an ileal brake on eating comes from lipid studies, where direct lipid infusion into the ileum suppresses both hunger and food intake. Outcomes from oral feeding studies are less conclusive with no evidence that 'protected' lipids have been successfully delivered into the ileum in order to trigger the brake. Whether CHO or protein may induce the ileal brake and suppress food intake has to date been little investigated, although both clearly have GI mediated effects. This review provides an overview of the mechanisms and mediators of activation of the ileal brake and assesses whether it may play an important role in appetite suppression.
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Affiliation(s)
- H S Shin
- Human Nutrition Unit, University of Auckland, Auckland, New Zealand; School of Biological Sciences, University of Auckland, Auckland, New Zealand
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18
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The role of gut hormones in controlling the food intake. What is their role in emerging diseases? ACTA ACUST UNITED AC 2012; 59:197-206. [DOI: 10.1016/j.endonu.2011.11.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Revised: 11/22/2011] [Accepted: 11/28/2011] [Indexed: 12/22/2022]
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Browning KN, Travagli RA. Plasticity of vagal brainstem circuits in the control of gastrointestinal function. Auton Neurosci 2011; 161:6-13. [PMID: 21147043 PMCID: PMC3061976 DOI: 10.1016/j.autneu.2010.11.001] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2010] [Revised: 10/28/2010] [Accepted: 11/02/2010] [Indexed: 12/16/2022]
Abstract
The afferent vagus transmits sensory information from the gastrointestinal (GI) tract and other viscera to the brainstem via a glutamatergic synapse at the level of the nucleus of the solitary tract (NTS). Second order NTS neurons integrate this sensory information with inputs from other CNS regions that regulate autonomic functions and homeostasis. Glutamatergic and GABAergic neurons are responsible for conveying the integrated response to other nuclei, including the adjacent dorsal motor nucleus of the vagus (DMV). The preganglionic neurons in the DMV are the source of the parasympathetic motor response back to the GI tract. The glutamatergic synapse between the NTS and DMV is unlikely to be tonically active in regulating gastric motility and tone although almost all neurotransmitters tested so far modulate transmission at this synapse. In contrast, the tonic inhibitory GABAergic input from the NTS to the DMV appears to be critical in setting the tone of gastric motility and, under basal conditions, is unaffected by many neurotransmitters or neurohormones. This review is based, in part, on a presentation by Dr Browning at the 2009 ISAN meeting in Sydney, Australia and discusses how neurohormones and macronutrients modulate glutamatergic transmission to NTS neurons and GABAergic transmission to DMV neurons in relation to sensory information that is received from the GI tract. These neurohormones and macronutrients appear to exert efficient "on-demand" control of the motor output from the DMV in response to ever-changing demands required to maintain homeostasis.
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Affiliation(s)
- Kirsteen N Browning
- Department of Neural and Behavioral Sciences, Penn State University College of Medicine, 500 University Drive, MC H109, Hershey, PA 17033, USA.
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20
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Wu T, Rayner CK, Jones K, Horowitz M. Dietary effects on incretin hormone secretion. VITAMINS AND HORMONES 2011; 84:81-110. [PMID: 21094897 DOI: 10.1016/b978-0-12-381517-0.00003-5] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The delivery of nutrients from the stomach into the duodenum and their subsequent interaction with the small intestine to stimulate incretin hormone release are central determinants of the glycemic response. The incretin effect has hitherto been attributed to the secretion of glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) from enteroendocrine cells in the intestinal epithelium. A number of recent studies have yielded fundamental insights into the influence of individual nutrients on incretin release and the mechanisms involved in the detection of carbohydrates, fats, and proteins by enteroendocrine cells, including the K(ATP) channel, sodium-glucose cotransporter 1 (SGLT1), sweet taste receptors, G-protein-coupled receptors (GPRs), and oligopeptide transporter 1 (PepT1). Dietary modification, including modifying macronutrient composition or the consumption of "preloads" in advance of a meal, represents a novel approach to manipulate the incretin response and thereby regulate glucose homeostasis in patients with type 2 diabetes. This review focuses on the effects of individual nutrients on incretin hormone secretion, our current understanding of the signaling mechanisms that trigger secretion by enteroendocrine cells, and the therapeutic implications of these observations.
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Affiliation(s)
- Tongzhi Wu
- University of Adelaide Discipline of Medicine, Royal Adelaide Hospital, North Terrace, Adelaide, South Australia, Australia
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21
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van Boxel OS, ter Linde JJM, Siersema PD, Smout AJPM. Role of chemical stimulation of the duodenum in dyspeptic symptom generation. Am J Gastroenterol 2010; 105:803-11; quiz 802, 812. [PMID: 20234343 DOI: 10.1038/ajg.2010.100] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The response to chemical stimuli such as acid, nutrients, and capsaicin at the level of the duodenum is increasingly recognized as important in the etiology of dyspeptic symptoms. Increased duodenal acid exposure has been reported for patients with dyspeptic symptoms. Duodenal hypersensitivity to acid and the enhancing effect of duodenal acid on gastroduodenal mechanosensitivity may also contribute to dyspeptic symptom generation. Serotonergic signaling pathways may be involved in acid-induced dyspeptic symptoms. As for nutrients, lipid has been unequivocally shown to have a function in the pathogenesis of dyspeptic symptoms. Cholecystokinin (CCK) is an important mediator of the effects of duodenal lipid on gastroduodenal sensorimotor activities. It is unclear whether CCK hypersecretion or hypersensitivity to CCK is responsible for symptoms in dyspeptic patients. The presence of capsaicin in the duodenum evokes symptoms and affects gastric sensorimotor function. In patients with dyspepsia, capsaicin-induced symptoms appeared to occur earlier and to be more severe, however the effects of duodenal infusion and putative consequent gastric sensorimotor abnormalities have not been examined. Capsaicin activates transient receptor potential ion channel of the vanilloid type I, which can also be activated and sensitized by acid. The interaction between the different chemical stimuli is complex and has not yet been studied in patients with dyspeptic symptoms. In conclusion, the mechanisms underlying an enhanced response to duodenal chemical stimulation in patients with dyspeptic symptoms are partially understood. At the level of the duodenum, abnormalities may exist in stimulus intensity, mucosal mRNA expression, biosynthesis, release, or inactivation of mucosal mediators, or receptor expression on afferent nerve endings. Elucidation of the abnormalities involved will provide a basis for rational treatment of dyspeptic symptoms.
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Affiliation(s)
- O S van Boxel
- Department of Gastroenterology and Hepatology, University Medical Center Utrecht, Utrecht, The Netherlands.
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22
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Dolan LC, Potter SM, Burdock GA. Evidence-based review on the effect of normal dietary consumption of fructose on development of hyperlipidemia and obesity in healthy, normal weight individuals. Crit Rev Food Sci Nutr 2010; 50:53-84. [PMID: 20047139 DOI: 10.1080/10408390903461426] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
In recent years, there has been episodic speculation that an increase in consumption of fructose from foods and beverages is an underlying factor responsible for the relatively recent increase in obesity and obesity-related diseases such as diabetes. Reports in support of this hypothesis have been published, showing that concentrations of triglycerides (TG) are higher and concentrations of insulin and hormones associated with satiety are lower in animals following the ingestion of fairly large quantities of fructose, compared to other carbohydrates. However, results from human studies are inconsistent. A possible reason for the inconsistent results is that they are dependent on the particular study population, the design of the studies, and/or the amount of fructose administered. A systematic assessment of the strength and quality of the studies and their relevance for healthy, normal weight humans ingesting fructose in a normal dietary manner has not been performed. The purpose of this review was to critically evaluate the existing database for a causal relationship between the ingestion of fructose in a normal, dietary manner and the development of hyperlipidemia or increased body weight in healthy, normal weight humans, using an evidence-based approach. The results of the analysis indicate that fructose does not cause biologically relevant changes in TG or body weight when consumed at levels approaching 95th percentile estimates of intake.
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Stevens JE, Doran S, Russo A, O'Donovan D, Feinle-Bisset C, Rayner CK, Horowitz M, Jones KL. Effects of intravenous fructose on gastric emptying and antropyloroduodenal motility in healthy subjects. Am J Physiol Gastrointest Liver Physiol 2009; 297:G1274-80. [PMID: 19808656 DOI: 10.1152/ajpgi.00214.2009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Gastric emptying (GE) of glucose is regulated closely, not only as a result of inhibitory feedback arising from the small intestine, but also because of the resulting hyperglycemia. Fructose is used widely in the diabetic diet and is known to empty from the stomach slightly faster than glucose but substantially slower than water. The aims of this study were to determine whether intravenous (iv) fructose affects GE and antropyloroduodenal motility and how any effects compare to those induced by iv glucose. Six healthy males (age: 26.7 +/- 3.8 yr) underwent concurrent measurements of GE of a solid meal (100 g ground beef labeled with 20 MBq (99m)Tc-sulfur colloid) and antropyloroduodenal motility on three separate days in randomized order during iv infusion of either fructose (0.5 g/kg), glucose (0.5 g/kg), or isotonic saline for 20 min. GE (scintigraphy), antropyloroduodenal motility (manometry), and blood glucose (glucometer) were measured for 120 min. There was a rise in blood glucose (P < 0.001) after iv glucose (peak 16.4 +/- 0.6 mmol/l) but not after fructose or saline. Intravenous glucose and fructose both slowed GE substantially (P < 0.005 for both), without any significant difference between them. Between t = 0 and 30 min, the number of antral pressure waves was less after both glucose and fructose (P < 0.002 for both) than saline, and there were more isolated pyloric pressure waves during iv glucose (P = 0.003) compared with fructose and saline (P = NS for both) infusions. In conclusion, iv fructose slows GE and modulates gastric motility in healthy subjects, and the magnitude of slowing of GE is comparable to that induced by iv glucose.
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Affiliation(s)
- Julie E Stevens
- University of Adelaide, Royal Adelaide Hospital, SA, Australia
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24
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Ma J, Rayner CK, Jones KL, Horowitz M. Insulin secretion in healthy subjects and patients with Type 2 diabetes--role of the gastrointestinal tract. Best Pract Res Clin Endocrinol Metab 2009; 23:413-24. [PMID: 19748059 DOI: 10.1016/j.beem.2009.03.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Postprandial glycaemia is now recognised as the major determinant of average glycaemic control in type 2 diabetes, as assessed by glycated haemoglobin. Therefore, an understanding of the factors influencing both the rise in blood glucose and insulin secretion after a meal is fundamental to the development of dietary and pharmacological approaches to optimise glycaemic control. The gastrointestinal tract regulates the rate at which carbohydrate and other nutrients are absorbed and is the source of regulatory peptides that stimulate pancreatic insulin secretion in the setting of elevated blood glucose levels. This article highlights the importance of the gastrointestinal tract in insulin secretion and glucose homeostasis and discusses potential strategies directed at modification of gastrointestinal function in order to improve glycaemic control in the management of diabetes.
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Affiliation(s)
- Jing Ma
- University of Adelaide Discipline of Medicine, Royal Adelaide Hospital, Adelaide, SA, Australia
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25
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Tran LT, Yuen VG, McNeill JH. The fructose-fed rat: a review on the mechanisms of fructose-induced insulin resistance and hypertension. Mol Cell Biochem 2009; 332:145-59. [PMID: 19536638 DOI: 10.1007/s11010-009-0184-4] [Citation(s) in RCA: 258] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2009] [Accepted: 06/09/2009] [Indexed: 02/07/2023]
Abstract
The metabolic syndrome is an important public health concern that predisposes individuals to the development of cardiovascular disease and/or Type 2 diabetes. The fructose-fed rat is an animal model of acquired systolic hypertension that displays numerous features of the metabolic syndrome. This animal model is used to study the relationship between insulin resistance/compensatory hyperinsulinemia and the development of hypertension. Several mechanisms have been proposed to mediate the link between insulin resistance and hypertension. In this review, we have addressed the role of sympathetic nervous system overactivation, increased production of vasoconstrictors, such as endothelin-1 and angiotensin II, and prostanoids in the development of hypertension in fructose-fed rats. The roles of nitric oxide, impaired endothelium-dependent relaxation and sex hormones in the pathogenesis of the fructose-fed induced hypertensive rats have also been highlighted. More recently, increased formation of reactive oxygen species and elevated levels of uric acid have been reported to contribute to fructose-induced hypertension.
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Affiliation(s)
- Linda T Tran
- Division of Pharmacology & Toxicology, Faculty of Pharmaceutical Sciences, University of British Columbia, 2146 East Mall, Vancouver, BC, V6T 1Z3, Canada
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Ma J, Bellon M, Wishart JM, Young R, Blackshaw LA, Jones KL, Horowitz M, Rayner CK. Effect of the artificial sweetener, sucralose, on gastric emptying and incretin hormone release in healthy subjects. Am J Physiol Gastrointest Liver Physiol 2009; 296:G735-9. [PMID: 19221011 PMCID: PMC2670679 DOI: 10.1152/ajpgi.90708.2008] [Citation(s) in RCA: 177] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The incretin hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), play an important role in glucose homeostasis in both health and diabetes. In mice, sucralose, an artificial sweetener, stimulates GLP-1 release via sweet taste receptors on enteroendocrine cells. We studied blood glucose, plasma levels of insulin, GLP-1, and GIP, and gastric emptying (by a breath test) in 7 healthy humans after intragastric infusions of 1) 50 g sucrose in water to a total volume of 500 ml (approximately 290 mosmol/l), 2) 80 mg sucralose in 500 ml normal saline (approximately 300 mosmol/l, 0.4 mM sucralose), 3) 800 mg sucralose in 500 ml normal saline (approximately 300 mosmol/l, 4 mM sucralose), and 4) 500 ml normal saline (approximately 300 mosmol/l), all labeled with 150 mg 13C-acetate. Blood glucose increased only in response to sucrose (P<0.05). GLP-1, GIP, and insulin also increased after sucrose (P=0.0001) but not after either load of sucralose or saline. Gastric emptying of sucrose was slower than that of saline (t50: 87.4+/-4.1 min vs. 74.7+/-3.2 min, P<0.005), whereas there were no differences in t50 between sucralose 0.4 mM (73.7+/-3.1 min) or 4 mM (76.7+/-3.1 min) and saline. We conclude that sucralose, delivered by intragastric infusion, does not stimulate insulin, GLP-1, or GIP release or slow gastric emptying in healthy humans.
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Affiliation(s)
- Jing Ma
- University of Adelaide, Discipline of Medicine, Royal Adelaide Hospital, North Terr., Adelaide SA 5000, Australia
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Melanson KJ, Angelopoulos TJ, Nguyen V, Zukley L, Lowndes J, Rippe JM. High-fructose corn syrup, energy intake, and appetite regulation. Am J Clin Nutr 2008; 88:1738S-1744S. [PMID: 19064539 DOI: 10.3945/ajcn.2008.25825e] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
High-fructose corn syrup (HFCS) has been implicated in excess weight gain through mechanisms seen in some acute feeding studies and by virtue of its abundance in the food supply during years of increasing obesity. Compared with pure glucose, fructose is thought to be associated with insufficient secretion of insulin and leptin and suppression of ghrelin. However, when HFCS is compared with sucrose, the more commonly consumed sweetener, such differences are not apparent, and appetite and energy intake do not differ in the short-term. Longer-term studies on connections between HFCS, potential mechanisms, and body weight have not been conducted. The main objective of this review was to examine collective data on associations between consumption of HFCS and energy balance, with particular focus on energy intake and its regulation.
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Adams SH, Stanhope KL, Grant RW, Cummings BP, Havel PJ. Metabolic and endocrine profiles in response to systemic infusion of fructose and glucose in rhesus macaques. Endocrinology 2008; 149:3002-8. [PMID: 18308841 PMCID: PMC2408804 DOI: 10.1210/en.2007-1812] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Diurnal patterns of circulating leptin concentrations are attenuated after consumption of fructose-sweetened beverages compared with glucose-sweetened beverages, likely a result of limited postprandial glucose and insulin excursions after fructose. Differences in postprandial exposure of adipose tissue to peripheral circulating fructose and glucose or in adipocyte metabolism of the two sugars may also be involved. Thus, we compared plasma leptin concentrations after 6-h iv infusions of saline, glucose, or fructose (15 mg/kg.min) in overnight-fasted adult rhesus monkeys (n = 9). Despite increases of plasma fructose from undetectable levels to about 2 mm during fructose infusion, plasma leptin concentrations did not increase, and the change of insulin was only about 10% of that seen during glucose infusion. During glucose infusion, plasma leptin was significantly increased above baseline concentrations by 240 min and increased steadily until the final 480-min time point (change in leptin = +2.5 +/- 0.9 ng/ml, P < 0.001 vs. saline; percent change in leptin = +55 +/- 16%; P < 0.005 vs. saline). Substantial anaerobic metabolism of fructose was suggested by a large increase of steady-state plasma lactate (change in lactate = 1.64 +/- 0.15 mm from baseline), which was significantly greater than that during glucose (+0.53 +/- 0.14 mm) or saline (-0.51 +/- 0.14 mm) infusions (P < 0.001). Therefore, increased adipose exposure to fructose and an active whole-body anaerobic fructose metabolism are not sufficient to increase circulating leptin levels in rhesus monkeys. Thus, additional factors (i.e. limited post-fructose insulin excursions and/or hexose-specific differences in adipocyte metabolism) are likely to underlie disparate effects of fructose and glucose to increase circulating leptin concentrations.
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Affiliation(s)
- Sean H Adams
- US Department of Agriculture-Agricultural Research Service Western Human Nutrition Research Center, University of California, Davis, Davis, California 95616, USA
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Kuo P, Chaikomin R, Pilichiewicz A, O'Donovan D, Wishart JM, Meyer JH, Jones KL, Feinle-Bisset C, Horowitz M, Rayner CK. Transient, early release of glucagon-like peptide-1 during low rates of intraduodenal glucose delivery. REGULATORY PEPTIDES 2008; 146:1-3. [PMID: 17964673 DOI: 10.1016/j.regpep.2007.09.032] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2007] [Revised: 09/26/2007] [Accepted: 09/26/2007] [Indexed: 02/07/2023]
Abstract
CONTEXT The "incretin" hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), account for some 60% of the stimulation of insulin by oral glucose, but the determinants of their secretion from the small intestine are poorly understood. Cells which release GIP (K cells) are localized to the proximal small intestine, while GLP-1 releasing cells (L cells) predominate in the distal gut. It has been suggested that a threshold rate of duodenal glucose delivery (approximately 1.8 kcal/min) needs to be exceeded for stimulation of GLP-1. OBJECTIVE To determine whether a low intraduodenal glucose load (1 kcal/min) has the capacity to stimulate GLP-1, and if so, the characteristics of the response. DESIGN Retrospective analysis of all studies in our laboratory involving healthy humans administered intraduodenal glucose at 1 kcal/min for 120 min. SETTING Clinical research laboratory. PARTICIPANTS 27 healthy subjects (24 male; age 36+/-3 years; BMI 25.2+/-0.7 kg/m(2)). MAIN OUTCOME MEASURES Plasma GLP-1, GIP, insulin, and blood glucose concentrations, reported as mean+/-SEM. RESULTS During intraduodenal glucose, plasma GLP-1 increased at 15 and 30 min (P<0.001 for both) and returned to baseline thereafter. In contrast, there were sustained increases in plasma GIP (P<0.001), insulin (P<0.001), and blood glucose (P<0.001). CONCLUSION In healthy subjects, there is early, transient stimulation of GLP-1 by glucose loads hitherto believed to be "sub-threshold". The mechanisms underlying this effect, which could be attributed to initially rapid transit to jejunal L cells, or a duodeno-jejunoileal neural or hormonal loop, remain to be determined.
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Affiliation(s)
- Paul Kuo
- University of Adelaide, Discipline of Medicine, Royal Adelaide Hospital, Australia
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Pilichiewicz AN, Chaikomin R, Brennan IM, Wishart JM, Rayner CK, Jones KL, Smout AJPM, Horowitz M, Feinle-Bisset C. Load-dependent effects of duodenal glucose on glycemia, gastrointestinal hormones, antropyloroduodenal motility, and energy intake in healthy men. Am J Physiol Endocrinol Metab 2007; 293:E743-53. [PMID: 17609258 DOI: 10.1152/ajpendo.00159.2007] [Citation(s) in RCA: 142] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Gastric emptying is a major determinant of glycemia, gastrointestinal hormone release, and appetite. We determined the effects of different intraduodenal glucose loads on glycemia, insulinemia, glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP) and cholecystokinin (CCK), antropyloroduodenal motility, and energy intake in healthy subjects. Blood glucose, plasma hormone, and antropyloroduodenal motor responses to 120-min intraduodenal infusions of glucose at 1) 1 ("G1"), 2) 2 ("G2"), and 3) 4 ("G4") kcal/min or of 4) saline ("control") were measured in 10 healthy males in double-blind, randomized fashion. Immediately after each infusion, energy intake at a buffet meal was quantified. Blood glucose rose in response to all glucose infusions (P < 0.05 vs. control), with the effect of G4 and G2 being greater than that of G1 (P < 0.05) but with no difference between G2 and G4. The rises in insulin, GLP-1, GIP, and CCK were related to the glucose load (r > 0.82, P < 0.05). All glucose infusions suppressed antral (P < 0.05), but only G4 decreased duodenal, pressure waves (P < 0.01), resulted in a sustained stimulation of basal pyloric pressure (P < 0.01), and decreased energy intake (P < 0.05). In conclusion, variations in duodenal glucose loads have differential effects on blood glucose, plasma insulin, GLP-1, GIP and CCK, antropyloroduodenal motility, and energy intake in healthy subjects. These observations have implications for strategies to minimize postprandial glycemic excursions in type 2 diabetes.
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Affiliation(s)
- Amelia N Pilichiewicz
- University of Adelaide Discipline of Medicine, Royal Adelaide Hospital, Adelaide SA 5000, Australia
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Chaikomin R, Rayner CK, Jones KL, Horowitz M. Upper gastrointestinal function and glycemic control in diabetes mellitus. World J Gastroenterol 2006; 12:5611-21. [PMID: 17007012 PMCID: PMC4088160 DOI: 10.3748/wjg.v12.i35.5611] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Recent evidence has highlighted the impact of glycemic control on the incidence and progression of diabetic micro- and macrovascular complications, and on cardiovascular risk in the non-diabetic population. Postprandial blood glucose concentrations make a major contribution to overall glycemic control, and are determined in part by upper gastrointestinal function. Conversely, poor glycemic control has an acute, reversible effect on gastrointestinal motility. Insights into the mechanisms by which the gut contributes to glycemia have given rise to a number of novel dietary and pharmacological strategies designed to lower postprandial blood glucose concentrations.
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Affiliation(s)
- Reawika Chaikomin
- Department of Medicine, Royal Adelaide Hospital, North Terrace, Adelaide, South Australia 5000, Australia
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Havel PJ. Dietary fructose: implications for dysregulation of energy homeostasis and lipid/carbohydrate metabolism. Nutr Rev 2005. [PMID: 15971409 DOI: 10.1111/j.1753-4887.2005.tb00132.x] [Citation(s) in RCA: 377] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Fructose intake and the prevalence of obesity have both increased over the past two to three decades. Compared with glucose, the hepatic metabolism of fructose favors lipogenesis, which may contribute to hyperlipidemia and obesity. Fructose does not increase insulin and leptin or suppress ghrelin, which suggests an endocrine mechanism by which it induces a positive energy balance. This review examines the available data on the effects of dietary fructose on energy homeostasis and lipid/carbohydrate metabolism. Recent publications, studies in human subjects, and areas in which additional research is needed are emphasized.
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Affiliation(s)
- Peter J Havel
- Department of Nutrition, University of California, One Shields Avenue, Davis, CA 95616, USA.
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Abstract
OBJECTIVE To investigate whether low-carbohydrate diets are efficient for reduction of body weight and through which mechanism. DESIGN A couple of studies using low-carbohydrate diets in the treatment of obesity are reviewed. Mechanisms for explaining the reduced appetite are described in relation to knowledge on regulation of appetite for fat and carbohydrate. RESULTS Studies with low-carbohydrate diets demonstrate a rapid weight loss, being more pronounced after 3 and 6 months compared to low-fat diets. After 12 months there is no difference between the low-carbohydrate and the conventional low-fat diet on weight loss. Both diets lead to improvements in risk factors for coronary heart disease, the low-carbohydrate diet leading to a greater decrease in serum triglycerides and increase in HDL cholesterol compared to the low-fat diet. Blood pressure, insulin sensitivity and LDL cholesterol were improved to a similar degree by the two diets. The mechanism for the rapid weight loss with the low-carbohydrate diet is a suppressed appetite, first through the high-protein content of the diet, second through the ketogenic nature of the diet with satiety signals for fat being active and third through the absence of hunger-promoting carbohydrate components like sucrose and/or fructose. CONCLUSION A rapid initial weight loss occurs with a low-carbohydrate diet due to a suppressed appetite. There is as yet no indication of an increased metabolic rate and an increased thermogenesis by the low-carbohydrate diet. The safety and efficacy of low-carbohydrate diets have to await further studies.
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Affiliation(s)
- C Erlanson-Albertsson
- Section of Metabolism, Endocrinology and Diabetes, Department of Experimental Medicine, University of Lund, Lund, Sweden.
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de Graaf C, Blom WAM, Smeets PAM, Stafleu A, Hendriks HFJ. Biomarkers of satiation and satiety. Am J Clin Nutr 2004; 79:946-61. [PMID: 15159223 DOI: 10.1093/ajcn/79.6.946] [Citation(s) in RCA: 310] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
This review's objective is to give a critical summary of studies that focused on physiologic measures relating to subjectively rated appetite, actual food intake, or both. Biomarkers of satiation and satiety may be used as a tool for assessing the satiating efficiency of foods and for understanding the regulation of food intake and energy balance. We made a distinction between biomarkers of satiation or meal termination and those of meal initiation related to satiety and between markers in the brain [central nervous system (CNS)] and those related to signals from the periphery to the CNS. Various studies showed that physicochemical measures related to stomach distension and blood concentrations of cholecystokinin and glucagon-like peptide 1 are peripheral biomarkers associated with meal termination. CNS biomarkers related to meal termination identified by functional magnetic resonance imaging and positron emission tomography are indicators of neural activity related to sensory-specific satiety. These measures cannot yet serve as a tool for assessing the satiating effect of foods, because they are not yet feasible. CNS biomarkers related to satiety are not yet specific enough to serve as biomarkers, although they can distinguish between extreme hunger and fullness. Three currently available biomarkers for satiety are decreases in blood glucose in the short term (<5 min), which have been shown to be involved in meal initiation; leptin changes during longer-term (>2-4 d) negative energy balance; and ghrelin concentrations, which have been implicated in both short-term and long-term energy balance. The next challenge in this research area is to identify food ingredients that have an effect on biomarkers of satiation, satiety, or both. These ingredients may help consumers to maintain their energy intake at a level consistent with a healthy body weight.
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Affiliation(s)
- Cees de Graaf
- TNO Nutrition and Food Research, Zeist, Netherlands.
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Rayner CK, Schwartz MP, van Dam PS, Renooij W, de Smet M, Horowitz M, Wishart JM, Smout AJPM, Samsom M. Upper gastrointestinal responses to intraduodenal nutrient in type 1 diabetes mellitus. Eur J Gastroenterol Hepatol 2004; 16:183-9. [PMID: 15075992 DOI: 10.1097/00042737-200402000-00010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
BACKGROUND Abnormal nutrient-related small-intestinal feedback may contribute to disordered gastric motility and upper gastrointestinal symptoms in patients with diabetes. AIM To evaluate the motor, sensory and incretin responses to intraduodenal nutrients in patients with type 1 diabetes and in controls. METHODS Eight type 1 diabetes patients (two with autonomic neuropathy) and nine controls were studied during euglycaemia. A manometric catheter was positioned across the pylorus, and nutrient was infused intraduodenally (90 kcal over 30 min). Blood glucose and plasma glucagon-like peptide 1 and gastric inhibitory polypeptide were measured, and sensations were assessed with visual analogue questionnaires. RESULTS During nutrient infusion, neither the number of antral waves nor the stimulation of phasic or basal pyloric pressures differed between patients and controls. Upper gut sensations and areas under the plasma incretin peptide curves did not differ between the groups. CONCLUSIONS During euglycaemia, the upper gastrointestinal motor, sensory and incretin peptide responses to small-intestinal nutrient are comparable in patients with relatively uncomplicated type 1 diabetes and in healthy subjects.
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Gribble FM, Williams L, Simpson AK, Reimann F. A novel glucose-sensing mechanism contributing to glucagon-like peptide-1 secretion from the GLUTag cell line. Diabetes 2003; 52:1147-54. [PMID: 12716745 DOI: 10.2337/diabetes.52.5.1147] [Citation(s) in RCA: 292] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Glucagon-like peptide 1 (GLP-1) secretion from intestinal L-cells is triggered by luminal nutrients. We reported previously that glucose-triggered GLP-1 release from the L-cell model GLUTag involves closure of ATP-sensitive K+ (K(ATP)) channels. We show here that GLP-1 secretion and electrical activity of GLUTag cells is triggered not only by metabolizable sugars (glucose or fructose) but also by the nonmetabolizable monosaccharide methyl-alpha-glucopyranoside. Responses to glucose and methyl-alpha-glucopyranoside were impaired by the sodium-glucose cotransporter (SGLT) inhibitor phloridzin. SLGT1 and 3 were detected in GLUTag cells by RT-PCR. Whereas fructose closed K(ATP) channels, methyl-alpha-glucopyranoside increased the membrane conductance and generated an inward current. Low concentrations of glucose and methyl-alpha-glucopyranoside also triggered small inward currents and enhanced the action potential frequency. We conclude that whereas low concentrations of metabolizable sugars trigger GLP-1 secretion via K(ATP) channel closure, SGLT substrates generate small inward currents as a result of the electrogenic action of the transporter. This transporter-associated current can trigger electrical activity and secretion when the concentration of substrate is high or when outward currents are reduced by metabolic closure of the K(ATP) channels. Electrogenic sugar entry via SGLTs provides a novel mechanism for glucose sensing by neuroendocrine cells.
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Affiliation(s)
- Fiona M Gribble
- Department of Clinical Biochemistry, University of Cambridge, Addenbrooke's Hospital, Cambridge CB2 2QR, United Kingdom
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Daniel EE, Anvari M, Fox-Threlkeld JET, McDonald TJ. Local, exendin-(9-39)-insensitive, site of action of GLP-1 in canine ileum. Am J Physiol Gastrointest Liver Physiol 2002; 283:G595-602. [PMID: 12181172 DOI: 10.1152/ajpgi.00110.2002] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Glucagon-like peptide-1 (GLP-1) modulates glucose levels following a meal, including by inhibition of gastric emptying and intestinal transport. Intra-arterial injection of GLP-1 into the gastric corpus, antrum, or pylorus of anesthetized dogs had no effect on the contractile activity of the resting or neurally activated stomach. GLP-1 injected intra-arterially inhibited intestinal segments when activated by enteric nerve stimulation but not by acetylcholine. Isolated ileum segments were perfused intra-arterially, instrumented with strain gauges to record circular muscle activity and with subserosal electrodes to stimulate enteric nerves. GLP-1 caused concentration-dependent inhibition of nerve-stimulated phasic but not tonic activity. This was absent during TTX-induced activity and partly prevented by N(G)-nitro-L-arginine. Exendin-(9-39), the GLP-1 antagonist, had no intrinsic activity and did not affect the actions of GLP-1. Capsaicin mimicked the effects of GLP-1 and may have reduced the effect of subsequent GLP-1. GLP-1 may mediate paracrine action on afferent nerves in the canine ileal mucosa using an unusual receptor.
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Affiliation(s)
- E E Daniel
- Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
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