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Jerlhag E. Alcohol-mediated behaviours and the gut-brain axis; with focus on glucagon-like peptide-1. Brain Res 2020; 1727:146562. [DOI: 10.1016/j.brainres.2019.146562] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 10/28/2019] [Accepted: 11/19/2019] [Indexed: 12/15/2022]
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Ong ZY, Liu JJ, Pang ZP, Grill HJ. Paraventricular Thalamic Control of Food Intake and Reward: Role of Glucagon-Like Peptide-1 Receptor Signaling. Neuropsychopharmacology 2017; 42:2387-2397. [PMID: 28811669 PMCID: PMC5645740 DOI: 10.1038/npp.2017.150] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Revised: 07/07/2017] [Accepted: 07/12/2017] [Indexed: 01/18/2023]
Abstract
Paraventricular thalamic nucleus (PVT) neurons receive hindbrain and hypothalamic inputs, and project to forebrain sites involved in reward and motivation function. The role of PVT in energy balance and reward control is however understudied. Given that PVT neurons express glucagon-like peptide-1 receptors (GLP-1R), which are critical to feeding and body weight control, we tested the hypothesis that PVT GLP-1R signaling contributes to food intake and reward inhibition. To assess the hypothesis, behavioral tests including chow and high-fat diet intake, meal patterns, conditioned place preference for high-fat food, cue-induced reinstatement of sucrose-seeking, and motivation to work for sucrose were employed following intra-PVT delivery of either GLP-1R agonist, exendin-4 (Ex4), or GLP-1R antagonist, exendin-9-39 (Ex9). Anatomical and electrophysiological experiments were conducted to examine the neural connections and cellular mechanisms of GLP-1R signaling on PVT-to-nucleus accumbens (NAc) projecting neurons. PVT GLP-1R agonism reduced food intake, food-motivation, and food-seeking, while blocking endogenous PVT GLP-1R signaling increased meal size and food intake. PVT neurons receive GLP-1 innervation from nucleus tractus solitarius preproglucagon neurons that were activated by food intake; these GLP-1 fibers formed close appositions to putative GLP-1R-expressing PVT cells that project to the NAc. Electrophysiological recordings of PVT-to-NAc neurons revealed that GLP-1R activation reduced their excitability, mediated in part via suppression of excitatory synaptic drive. Collectively, these behavioral, electrophysiological and anatomical data illuminate a novel function for PVT GLP-1R signaling in food intake control and suggest a role for the PVT-to-NAc pathway in mediating the effects of PVT GLP-1R activation.
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Affiliation(s)
- Zhi Yi Ong
- Department of Psychology, University of Pennsylvania, Philadelphia, PA, USA,School of Psychology, University of New South Wales, High Street, Sydney, NSW 2052, Australia, Tel: +612 9385 5480, Fax: +612 9385 3641, E-mail:
| | - Jing-Jing Liu
- Child Health Institute of New Jersey, Rutgers University Robert Wood Johnson Medical School, New Brunswick, NJ, USA
| | - Zhiping P Pang
- Child Health Institute of New Jersey, Rutgers University Robert Wood Johnson Medical School, New Brunswick, NJ, USA
| | - Harvey J Grill
- Department of Psychology, University of Pennsylvania, Philadelphia, PA, USA
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Andreozzi F, Raciti GA, Nigro C, Mannino GC, Procopio T, Davalli AM, Beguinot F, Sesti G, Miele C, Folli F. The GLP-1 receptor agonists exenatide and liraglutide activate Glucose transport by an AMPK-dependent mechanism. J Transl Med 2016; 14:229. [PMID: 27473212 PMCID: PMC4967343 DOI: 10.1186/s12967-016-0985-7] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Accepted: 07/20/2016] [Indexed: 01/11/2023] Open
Abstract
Aims/hypothesis Potentiation of glucose-induced insulin secretion is the main mechanism of exenatide (EXE) antidiabetic action, however, increased glucose utilization by peripheral tissues has been also reported. We here studied the effect of EXE on glucose uptake by skeletal muscle cells. Methods 2-deoxy-glucose (2DG) uptake and intracellular signal pathways were measured in rat L6 skeletal muscle myotubes exposed to 100 nmol/l EXE for up to 48 h. Mechanisms of EXE action were explored by inhibiting AMPK activity with compound C (CC, 40 μmol/l) or siRNAs (2 μmol/l). Results Time course experiments show that EXE increases glucose uptake up to 48 h achieving its maximal effect, similar to that induced by insulin, after 20 min (2- vs 2.5-fold-increase, respectively). Differently from insulin, EXE does not stimulate: (i) IR β-subunit- and IRS1 tyrosine phosphorylation and binding to p85 regulatory subunit of PI-3kinase; (ii) AKT activation; and (iii) ERK1/2 and JNK1/2 phosphorylation. Conversely, EXE increases phosphorylation of α-subunit of AMPK at Thr172 by 2.5-fold (p < 0.01). Co-incubation of EXE and insulin does not induce additive effects on 2DG-uptake. Inhibition of AMPK with CC, and reduction of AMPK protein expression by siRNA, completely abolish EXE-induced 2DG-uptake. Liraglutide, another GLP-1 receptor agonist, also stimulates AMPK phosphorylation and 2DG-uptake. Moreover, EXE stimulates 2DG-uptake also by L6 myotubes rendered insulin-resistant with methylglyoxal. Finally, EXE also induces glucose transporter Glut-4 translocation to the plasma membrane. Conclusions/interpretation In L6 myotubes, EXE and liraglutide increase glucose uptake in an insulin-independent manner by activating AMPK. Electronic supplementary material The online version of this article (doi:10.1186/s12967-016-0985-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Francesco Andreozzi
- Department of Medical and Surgical Sciences, University of Catanzaro "Magna-Graecia", Catanzaro, Italy. .,Division of Diabetes, Department of Medicine, University of Texas Health Science Center, San Antonio, TX, USA.
| | - Gregory Alexander Raciti
- Institute of Experimental Endocrinology and Oncology "G. Salvatore", National Council of Research, Naples, Italy.,Department of Translational Medical Sciences, University of Naples "Federico II", Naples, Italy
| | - Cecilia Nigro
- Institute of Experimental Endocrinology and Oncology "G. Salvatore", National Council of Research, Naples, Italy.,Department of Translational Medical Sciences, University of Naples "Federico II", Naples, Italy
| | - Gaia Chiara Mannino
- Department of Medical and Surgical Sciences, University of Catanzaro "Magna-Graecia", Catanzaro, Italy
| | - Teresa Procopio
- Department of Medical and Surgical Sciences, University of Catanzaro "Magna-Graecia", Catanzaro, Italy
| | - Alberto M Davalli
- Department of Medicine Endocrinology Unit, Ospedale San Raffaele, Milan, Italy
| | - Francesco Beguinot
- Institute of Experimental Endocrinology and Oncology "G. Salvatore", National Council of Research, Naples, Italy.,Department of Translational Medical Sciences, University of Naples "Federico II", Naples, Italy
| | - Giorgio Sesti
- Department of Medical and Surgical Sciences, University of Catanzaro "Magna-Graecia", Catanzaro, Italy
| | - Claudia Miele
- Institute of Experimental Endocrinology and Oncology "G. Salvatore", National Council of Research, Naples, Italy.,Department of Translational Medical Sciences, University of Naples "Federico II", Naples, Italy
| | - Franco Folli
- Division of Diabetes, Department of Medicine, University of Texas Health Science Center, San Antonio, TX, USA. .,Department of Internal Medicine, University of Campinas, Campinas, SP, Brazil.
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Liu J, Pang ZP. Glucagon-like peptide-1 drives energy metabolism on the synaptic highway. FEBS J 2016; 283:4413-4423. [DOI: 10.1111/febs.13785] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Revised: 06/04/2016] [Accepted: 06/16/2016] [Indexed: 01/17/2023]
Affiliation(s)
- Ji Liu
- Child Health Institute of New Jersey; Rutgers University Robert Wood Johnson Medical School; New Brunswick NJ USA
- Department of Neuroscience and Cell Biology; Rutgers University Robert Wood Johnson Medical School; New Brunswick NJ USA
| | - Zhiping P. Pang
- Child Health Institute of New Jersey; Rutgers University Robert Wood Johnson Medical School; New Brunswick NJ USA
- Department of Neuroscience and Cell Biology; Rutgers University Robert Wood Johnson Medical School; New Brunswick NJ USA
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Yamazaki S, Satoh H, Watanabe T. Liraglutide enhances insulin sensitivity by activating AMP-activated protein kinase in male Wistar rats. Endocrinology 2014; 155:3288-301. [PMID: 24949659 DOI: 10.1210/en.2013-2157] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
We investigated the effects of liraglutide on insulin sensitivity and glucose metabolism in male Wistar rats. The rats were fed a normal chow diet (NCD) or a 60% high-fat diet (HFD) for a total of 4 weeks. After 3 weeks of feeding, they were injected with liraglutide once a day for 7 days. Subsequently, euglycemic-hyperinsulinemic clamp studies were performed after fasting the animals for 8 hours. During the clamp studies on the NCD-fed rats, the glucose infusion rate required for euglycemia was significantly higher in the liraglutide group than in the control group. The clamp hepatic glucose output was significantly lower in the liraglutide group than in the control group, but the insulin-stimulated glucose disposal rate did not change significantly in the liraglutide groups. The clamp studies on the HFD-fed rats revealed that the glucose infusion rate required to achieve euglycemia was significantly higher in the liraglutide group than in the control HFD group, and the insulin-stimulated glucose disposal rate increased significantly in the liraglutide groups. The clamp hepatic glucose output decreased significantly in the liraglutide groups. Consistent with the clamp data, the insulin-stimulated phosphorylation of Akt and AMP-activated protein kinase was enhanced in the livers of the NCD- and HFD-fed rats and in the skeletal muscles of the HFD-fed rats. Oil red O staining indicated that liraglutide also improved hepatic steatosis. In summary, our studies suggest that in normal glucose tolerance states, liraglutide enhances insulin sensitivity in the liver but not in skeletal muscles. However, in insulin-resistant states, liraglutide improves insulin resistance in the liver and muscles and improves fatty liver.
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Affiliation(s)
- Satoru Yamazaki
- Department of Nephrology, Hypertension, Diabetology, Endocrinology, and Metabolism, Fukushima Medical University, Fukushima 960-1295, Japan
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Nuche-Berenguer B, Portal-Núñez S, Moreno P, González N, Acitores A, López-Herradón A, Esbrit P, Valverde I, Villanueva-Peñacarrillo ML. Presence of a functional receptor for GLP-1 in osteoblastic cells, independent of the cAMP-linked GLP-1 receptor. J Cell Physiol 2010; 225:585-92. [PMID: 20506394 DOI: 10.1002/jcp.22243] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Glucagon-like peptide 1 (GLP-1) controls glucose metabolism in extrapancreatic tissues through receptors other than the pancreatic cAMP-linked GLP-1 receptor; also, GLP-1 induces an insulin- and PTH-independent bone anabolic action in insulin-resistant and type-2 diabetic rats. Here we searched for the presence and characteristics of GLP-1 receptors in osteoblastic MC3T3-E1 cells. [(125)I]-GLP-1 specific binding to MC3T3-E1 cells was time- and temperature-dependent, reaching maximal value at 30 min at 25 degrees C; in these conditions, [(125)I]-GLP-1 binding was dissociable, and displaced by GLP-1, partially by GLP-2, but not by exendin-4 (Ex-4), exendin-9 (Ex-9), glucagon or insulin; Scatchard analysis of the unlabeled GLP-1 data showed high and low affinity binding sites; cross-linking of GLP-1 binding revealed an estimated 70 kDa band, almost undetectable in the presence of 10(-6) M GLP-1. GLP-1, Ex-9, insulin or glucagon failed to modify cellular cAMP content, while GLP-2 and Ex-4 increased it. However, GLP-1 induced an immediate hydrolysis of glycosylphosphatidylinositols (GPIs) generating short-lived inositolphosphoglycans (IPGs), and an increase in phosphatidylinositol-3 kinase (PI3K) and mitogen activated protein kinase (MAPK) activities; Ex-4 also affected GPIs, but its action was delayed with respect to that of GLP-1. This incretin was found to decrease Runx2 but increased osteocalcin gene expression, without affecting that of osteoprotegerin or the canonical Wnt pathway activity in MC3T3-E1 cells which do not express the pancreatic GLP-1 receptor. Our data demonstrate for the first time that GLP-1 can directly and functionally interact with osteoblastic cells, possibly through a GPI/IPG-coupled receptor.
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Raab EL, Vuguin PM, Stoffers DA, Simmons RA. Neonatal exendin-4 treatment reduces oxidative stress and prevents hepatic insulin resistance in intrauterine growth-retarded rats. Am J Physiol Regul Integr Comp Physiol 2009; 297:R1785-94. [PMID: 19846744 DOI: 10.1152/ajpregu.00519.2009] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Intrauterine growth retardation (IUGR) has been linked to the development of type 2 diabetes in adulthood. We have developed an IUGR model in the rat whereby the animals develop diabetes later in life. Previous studies demonstrate that administration of the long-acting glucagon-like-peptide-1 agonist, exendin-4, during the neonatal period prevents the development of diabetes in IUGR rats. IUGR animals exhibit hepatic insulin resistance early in life (prior to the onset of hyperglycemia), characterized by blunted suppression of hepatic glucose production (HGP) in response to insulin. Basal HGP is also significantly higher in IUGR rats. We hypothesized that neonatal administration of exendin-4 would prevent the development of hepatic insulin resistance. IUGR and control rats were given exendin-4 on days 1-6 of life. Hyperinsulinemic-euglycemic clamp studies showed that Ex-4 significantly reduced basal HGP by 20% and normalized insulin suppression of HGP in IUGR rats. While Ex-4 decreased body weight and fat content in both Control and IUGR animals, these differences were only statistically significant in Controls. Exendin-4 prevented development of oxidative stress in liver and reversed insulin-signaling defects in vivo, thereby preventing the development of hepatic insulin resistance. Defects in glucose disposal and suppression of hepatic glucose production in response to insulin were reversed. Similar results were obtained in isolated Ex-4-treated neonatal hepatocytes. These results indicate that exposure to exendin-4 in the newborn period reverses the adverse consequences of fetal programming and prevents the development of hepatic insulin resistance.
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Affiliation(s)
- Elisabeth L Raab
- Department of Pediatrics, Children's Hospital Los Angeles, Los Angeles, California, USA
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Abu-Hamdah R, Rabiee A, Meneilly GS, Shannon RP, Andersen DK, Elahi D. Clinical review: The extrapancreatic effects of glucagon-like peptide-1 and related peptides. J Clin Endocrinol Metab 2009; 94:1843-52. [PMID: 19336511 PMCID: PMC2690432 DOI: 10.1210/jc.2008-1296] [Citation(s) in RCA: 150] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
CONTEXT Glucagon-like peptide-1 (GLP-1) 7-36 amide, an insulinotropic hormone released from the intestinal L cells in response to nutrient ingestion, has been extensively reviewed with respect to beta-cell function. However GLP-1 receptors are abundant in many other tissues. Thus, the function of GLP-1 is not limited to the islet cells, and it has regulatory actions on many other organs. EVIDENCE ACQUISITION A review of published, peer-reviewed medical literature (1987 to September 2008) on the extrapancreatic actions of GLP-1 was performed. EVIDENCE SYNTHESIS The extrapancreatic actions of GLP-1 include inhibition of gastric emptying and gastric acid secretion, thereby fulfilling the definition of GLP-1 as an enterogastrone. Other important extrapancreatic actions of GLP-1 include a regulatory role in hepatic glucose production, the inhibition of pancreatic exocrine secretion, cardioprotective and cardiotropic effects, the regulation of appetite and satiety, and stimulation of afferent sensory nerves. The primary metabolite of GLP-1, GLP-1 (9-36) amide, or GLP-1m, is the truncated product of degradation by dipeptidyl peptidase-4. GLP-1m has insulinomimetic effects on hepatic glucose production and cardiac function. Exendin-4 present in the salivary gland of the reptile, Gila monster (Heloderma suspectum), is a high-affinity agonist for the mammalian GLP-1 receptor. It is resistant to degradation by dipeptidyl peptidase-4, and therefore has a prolonged half-life. CONCLUSION GLP-1 and its metabolite have important extrapancreatic effects particularly with regard to the cardiovascular system and insulinomimetic effects with respect to glucose homeostasis. These effects may be particularly important in the obese state. GLP-1, GLP-1m, and exendin-4 therefore have potential therapeutic roles because of their diffuse extrapancreatic actions.
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Affiliation(s)
- Rania Abu-Hamdah
- Johns Hopkins University School of Medicine, Department of Surgery, Johns Hopkins Bayview Medical Center, Baltimore, Maryland 21224-2780, USA
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Kim W, Egan JM. The role of incretins in glucose homeostasis and diabetes treatment. Pharmacol Rev 2008; 60:470-512. [PMID: 19074620 DOI: 10.1124/pr.108.000604] [Citation(s) in RCA: 563] [Impact Index Per Article: 35.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Incretins are gut hormones that are secreted from enteroendocrine cells into the blood within minutes after eating. One of their many physiological roles is to regulate the amount of insulin that is secreted after eating. In this manner, as well as others to be described in this review, their final common raison d'être is to aid in disposal of the products of digestion. There are two incretins, known as glucose-dependent insulinotropic peptide (GIP) and glucagon-like peptide-1 (GLP-1), that share many common actions in the pancreas but have distinct actions outside of the pancreas. Both incretins are rapidly deactivated by an enzyme called dipeptidyl peptidase 4 (DPP4). A lack of secretion of incretins or an increase in their clearance are not pathogenic factors in diabetes. However, in type 2 diabetes (T2DM), GIP no longer modulates glucose-dependent insulin secretion, even at supraphysiological (pharmacological) plasma levels, and therefore GIP incompetence is detrimental to beta-cell function, especially after eating. GLP-1, on the other hand, is still insulinotropic in T2DM, and this has led to the development of compounds that activate the GLP-1 receptor with a view to improving insulin secretion. Since 2005, two new classes of drugs based on incretin action have been approved for lowering blood glucose levels in T2DM: an incretin mimetic (exenatide, which is a potent long-acting agonist of the GLP-1 receptor) and an incretin enhancer (sitagliptin, which is a DPP4 inhibitor). Exenatide is injected subcutaneously twice daily and its use leads to lower blood glucose and higher insulin levels, especially in the fed state. There is glucose-dependency to its insulin secretory capacity, making it unlikely to cause low blood sugars (hypoglycemia). DPP4 inhibitors are orally active and they increase endogenous blood levels of active incretins, thus leading to prolonged incretin action. The elevated levels of GLP-1 are thought to be the mechanism underlying their blood glucose-lowering effects.
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Affiliation(s)
- Wook Kim
- National Institute on Aging, National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA
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Dardevet D, Moore MC, DiCostanzo CA, Farmer B, Neal DW, Snead W, Lautz M, Cherrington AD. Insulin secretion-independent effects of GLP-1 on canine liver glucose metabolism do not involve portal vein GLP-1 receptors. Am J Physiol Gastrointest Liver Physiol 2005; 289:G806-14. [PMID: 16051922 PMCID: PMC2435373 DOI: 10.1152/ajpgi.00121.2005] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Whether glucagon-like peptide (GLP)-1 requires the hepatic portal vein to elicit its insulin secretion-independent effects on glucose disposal in vivo was assessed in conscious dogs using tracer and arteriovenous difference techniques. In study 1, six conscious overnight-fasted dogs underwent oral glucose tolerance testing (OGTT) to determine target GLP-1 concentrations during clamp studies. Peak arterial and portal values during OGTT ranged from 23 to 65 pM and from 46 to 113 pM, respectively. In study 2, we conducted hyperinsulinemic-hyperglycemic clamp experiments consisting of three periods (P1, P2, and P3) during which somatostatin, glucagon, insulin and glucose were infused. The control group received saline, the PePe group received GLP-1 (1 pmol.kg(-1).min(-1)) peripherally, the PePo group received GLP-1 (1 pmol.kg(-1).min(-1)) peripherally (P2) and then intraportally (P3), and the PeHa group received GLP-1 (1 pmol.kg(-1).min(-1)) peripherally (P2) and then through the hepatic artery (P3) to increase the hepatic GLP-1 load to the same extent as in P3 in the PePo group (n = 8 dogs/group). Arterial GLP-1 levels increased similarly in all groups during P2 ( approximately 50 pM), whereas portal GLP-1 levels were significantly increased (2-fold) in the PePo vs. PePe and PeHa groups during P3. During P2, net hepatic glucose uptake (NHGU) increased slightly but not significantly (vs. P1) in all groups. During P3, GLP-1 increased NHGU in the PePo and PeHa groups more than in the control and PePe groups (change of 10.8 +/- 1.3 and 10.6 +/- 1.0 vs. 5.7 +/- 1.0 and 5.4 +/- 0.8 micromol.kg(-1).min(-1), respectively, P < 0.05). In conclusion, physiological GLP-1 levels increase glucose disposal in the liver, and this effect does not involve GLP-1 receptors located in the portal vein.
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Affiliation(s)
- Dominique Dardevet
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0615, USA
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González N, Acitores A, Sancho V, Valverde I, Villanueva-Peñacarrillo ML. Effect of GLP-1 on glucose transport and its cell signalling in human myocytes. ACTA ACUST UNITED AC 2005; 126:203-11. [PMID: 15664668 DOI: 10.1016/j.regpep.2004.10.002] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2004] [Revised: 10/01/2004] [Accepted: 10/01/2004] [Indexed: 11/24/2022]
Abstract
Glucagon-like peptide-1 (GLP-1) controls glucose metabolism in extrapancreatic tissues participating in glucose homeostasis, through receptors not associated to cAMP. In rat hepatocytes, activation of PI3K/PKB, PKC and PP-1 mediates the GLP-1-induced stimulation of glycogen synthase. We have investigated the effect of GLP-1 in normal human myocytes, and that of its structurally related peptides exendin-4 (Ex-4) and its truncated form 9-39 (Ex-9) upon glucose uptake, and the participation of cellular enzymes proposed to mediate insulin actions. GLP-1 and both exendins activated, like insulin, PI3K/PKB and p42/44 MAPK enzymes, but p70s6k was activated only by GLP-1 and insulin. GLP-1, Ex-4 and Ex-9, like insulin, stimulated glucose uptake; wortmannin blocked the action of GLP-1, insulin and Ex-9, and reduced that of Ex-4; PD98059 abolished the effect of all peptides/hormones, while rapamycin blocked that of insulin and partially prevented that of GLP-1. H-7 abolished the action of GLP-1, insulin and Ex-4, while Ro 31-8220 prevented only the Ex-4 and Ex-9 effect. In conclusion, GLP-1, like insulin, stimulates glucose uptake, and this involves activation of PI3K/PKB, p44/42 MAPKs, partially p70s6k, and possibly PKC; Ex-4 and Ex-9 both have GLP-1-like effect upon glucose transport, in which both share with GLP-1 an activation of PI3K/PKB--partially in the case of Ex-4--and p44/42 MAPKs but not p70s6k.
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Affiliation(s)
- Nieves González
- Department of Metabolism, Nutrition and Hormones, Fundación Jiménez Díaz, Avda. Reyes Católicos 2, 28040-Madrid, Spain
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Kieffer TJ, Hussain MA, Habener JF. Glucagon and Glucagon‐like Peptide Production and Degradation. Compr Physiol 2001. [DOI: 10.1002/cphy.cp070208] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Hällbrink M, Holmqvist T, Olsson M, Ostenson CG, Efendic S, Langel U. Different domains in the third intracellular loop of the GLP-1 receptor are responsible for Galpha(s) and Galpha(i)/Galpha(o) activation. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1546:79-86. [PMID: 11257510 DOI: 10.1016/s0167-4838(00)00270-3] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
It has previously been shown that the GLP-1 receptor is primarily coupled to the adenylate cyclase pathway via activation of Galpha(s) proteins. Recent studies have shown that the third intracellular loop of the receptor is important in the stimulation of cAMP production. We have studied the effect of three synthetic peptide sequences derived from the third intracellular loop of the GLP-1 receptor on signal transduction in Rin m5F cell membranes. The whole third intracellular loop strongly stimulates both pertussis toxin and cholera toxin-sensitive G proteins, while the N-terminal half exclusively stimulates cholera toxin-sensitive G proteins and the C-terminal half only stimulates pertussis toxin-sensitive G-proteins as demonstrated by measurements of GTPase activity. These data confirm that the principal stimulatory G-protein interaction site resides in the third intracellular loop, but also suggest that the GLP-1 receptor is not only coupled to the Galpha(s) but also to the Galpha(i)/Galpha(o) type of G proteins and that distinct domains within the third intracellular loop are responsible for the activation of the different G-protein subfamilies.
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Affiliation(s)
- M Hällbrink
- Department of Neurochemistry and Neurotoxicity, Stockholm University, S-106 91 Stockholm, Sweden
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Nishizawa M, Nakabayashi H, Kawai K, Ito T, Kawakami S, Nakagawa A, Niijima A, Uchida K. The hepatic vagal reception of intraportal GLP-1 is via receptor different from the pancreatic GLP-1 receptor. JOURNAL OF THE AUTONOMIC NERVOUS SYSTEM 2000; 80:14-21. [PMID: 10742535 DOI: 10.1016/s0165-1838(99)00086-7] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Glucagon-like peptide-1 (7-36)amide (tGLP-1), a representative humoral incretin, released into the portal circulation in response to a meal ingestion, exerts insulinotropic action through binding to the tGLP-1 receptor known to be a single molecular form thus far. We previously reported that the hepatic vagal nerve is receptive to intraportal tGLP-1, but not to non-insulinotropic full-length GLP-1-(1-37), through a mechanism mediated by specific receptor to the hormone. In the present study, we aimed to examine how modification of the receptor function alters this neural reception of tGLP-1, by using the specific agonist, exendin-4, and the specific antagonist, exendin (9-39)amide, of the receptor at doses known to exert their effects on the insulinotropic action of tGLP-1. Intraportal injection of 0.2 or 4.0 pmol tGLP-1, a periphysiological and pharmacological dose, respectively, facilitated significantly the afferent impulse discharge rate of the hepatic vagus in anesthetized rats, as reported previously. However, unexpectedly, intraportal injection of exendin-4 at a dose of 0.2 or 4.0 pmol, or of even 40.0 pmol, did not facilitate the afferents at all. Moreover, intraportal injection of exendin (9-39)amide at 100 times or more molar dose to that of tGLP-1, either 5 min before or 10 min after injection of 0.2 or 4.0 pmol tGLP-1, failed to modify the tGLP-1-induced facilitation of the afferents. The present results suggest that the neural reception of tGLP-1 involves a receptor mechanism distinct from that in the well-known humoral insulinotropic action.
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Affiliation(s)
- M Nishizawa
- Division of Life Science, Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Japan
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16
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Affiliation(s)
- T J Kieffer
- Department of Medicine, University of Alberta, Edmonton, Canada.
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17
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Yang H, Egan JM, Wang Y, Moyes CD, Roth J, Montrose MH, Montrose-Rafizadeh C. GLP-1 action in L6 myotubes is via a receptor different from the pancreatic GLP-1 receptor. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:C675-83. [PMID: 9730951 DOI: 10.1152/ajpcell.1998.275.3.c675] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The incretin hormone glucagon-like peptide-1 (GLP-1)-(7-36) amide is best known for its antidiabetogenic actions mediated via a GLP-1 receptor present on pancreatic endocrine cells. To investigate the molecular mechanisms of GLP-1 action in muscle, we used cultured L6 myotubes. In L6 myotubes, GLP-1 enhanced insulin-stimulated glycogen synthesis by 140% while stimulating CO2 production and lactate formation by 150%. In the presence of IBMX, GLP-1 diminished cAMP levels to 83% of IBMX alone. In L6 myotubes transfected with pancreatic GLP-1 receptor, GLP-1 increased cAMP levels and inhibited glycogen synthesis by 60%. An antagonist of pancreatic GLP-1 receptor, exendin-4-(9-39), inhibited GLP-1-mediated glycogen synthesis in GLP-1 receptor-transfected L6 myotubes. However, in parental L6 myotubes, exendin-4-(9-39) and GLP-1-(1-36) amide, an inactive peptide on pancreatic GLP-1 receptor, displaced 125I-labeled GLP-1 binding and stimulated glycogen synthesis by 186 and 130%, respectively. These results suggest that the insulinomimetic effects of GLP-1 in L6 cells are likely to be mediated by a receptor that is different from the GLP-1 receptor found in the pancreas.
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Affiliation(s)
- H Yang
- Laboratory of Clinical Physiology, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA
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18
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Márquez L, Trapote MA, Luque MA, Valverde I, Villanueva-Peñacarrillo ML. Inositolphosphoglycans possibly mediate the effects of glucagon-like peptide-1(7-36)amide on rat liver and adipose tissue. Cell Biochem Funct 1998; 16:51-6. [PMID: 9580153 DOI: 10.1002/(sici)1099-0844(199803)16:1<51::aid-cbf767>3.0.co;2-t] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Insulin-like effects of glucagon-like peptide-1(7-36)amide (GLP-1) in rat liver, skeletal muscle and fat, and also the presence of GLP-1 receptors in these extrapancreatic tissues, have been documented. In skeletal muscle and liver, the action of GLP-1 is not associated with an activation of adenylate cyclase, and in cultured murine myocytes and hepatoma cell lines, it was found that GLP-1 provokes the generation of inositolphosphoglycan molecules (IPGs), which are considered second messengers of insulin action. In the present work, we document in isolated normal rat adipocytes and hepatocytes that GLP-1 exerts a rapid decrease of the radiolabelled glycosylphosphatidylinositols (GPIs)--precursors of IPGs--in the same manner as insulin, indicating their hydrolysis and the immediate short-lived generation of IPGs. Thus, IPGs could be mediators in the GLP-1 actions in adipose tissue and liver, as well as in skeletal muscle, through GLP-1 receptors which are, at least functionally, different from that of the pancreatic B-cell.
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Affiliation(s)
- L Márquez
- Departamento Metabolismo Nutrición y Hormonas, Fundación Jiménez Díaz, Madrid, Spain
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19
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Alcántara AI, Morales M, Delgado E, López-Delgado MI, Clemente F, Luque MA, Malaisse WJ, Valverde I, Villanueva-Peñacarrillo ML. Exendin-4 agonist and exendin(9-39)amide antagonist of the GLP-1(7-36)amide effects in liver and muscle. Arch Biochem Biophys 1997; 341:1-7. [PMID: 9143346 DOI: 10.1006/abbi.1997.9951] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The GLP-1 structurally related peptides exendin-4 and exendin(9-39)amide were found to act, in rat liver and skeletal muscle, as agonist and antagonist, respectively, of the GLP-1(7-36)amide effects on glucose metabolism. Thus, like GLP-1(7-36)amide, exendin-4 increased glycogen synthase a activity and glucose incorporation into glycogen in both tissues and also stimulated exogenous D-glucose utilization and oxidation in muscle. These effects of GLP-1(7-36)amide and exendin-4 were inhibited by exendin(9-39)amide. Our findings provide further support to the proposed use of GLP-1, or exendin-4, as a tool in the treatment of diabetes mellitus. Thus, in addition to the well-known insulinotropic action of the peptides, they act both in liver and in muscle in a manner most suitable for restoration of glucose homeostasis, with emphasis on their positive effects upon glycogen synthesis in the two tissues and on the stimulation of exogenous glucose catabolism in muscle.
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Affiliation(s)
- A I Alcántara
- Departamento de Metabolismo, Nutrición y Hormonas, Fundación Jiménez Díaz, Madrid, Spain
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20
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O'Harte FP, Gray AM, Abdel-Wahab YH, Flatt PR. Effects of non-glycated and glycated glucagon-like peptide-1(7-36) amide on glucose metabolism in isolated mouse abdominal muscle. Peptides 1997; 18:1327-33. [PMID: 9392833 DOI: 10.1016/s0196-9781(97)00201-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
This study investigated the actions of non-glycated and glycated glucagon-like peptide-1(7-36)amide (tGLP-1) on glucose uptake and metabolism in isolated mouse abdominal muscle. Monoglycated tGLP-1 (Mr 3463.8) was prepared under hyperglycemic reducing conditions and purified by HPLC. Non-glycated tGLP-1 (10(-10)-10(-8) mol/l) stimulated both 2-deoxy-D-[1-3H]glucose uptake (1.3-1.5 fold) and 14C-glucose oxidation (1.4-1.7 fold) in muscle compared to controls without tGLP-1. Glycation reduced these stimulatory effects by 27-33% and 25% (at 10(-9) mol/l), respectively. tGLP-1 (10(-10)-10(-8) mol/l) promoted muscle glycogenesis and lactate production, whereas glycated peptide was ineffective below 10(-9) mol/l. This study demonstrates that tGLP-1 has potent glycogenic effects in mouse abdominal muscle in vitro and that glycation impairs its action.
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Affiliation(s)
- F P O'Harte
- School of Biomedical Sciences, University of Ulster, Coleraine, N. Ireland.
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