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MA Luque, N Gonzalez, L Marquez, A Acitores, A Redondo, M Morales, I Valverde, and ML Villanueva-Penacarrillo

Glucagon-like peptide-1 (GLP-1) has been shown to have insulin-like effects upon the metabolism of glucose in rat liver, muscle and fat, and on that of lipids in rat and human adipocytes. These actions seem to be exerted through specific receptors which, unlike that of the pancreas, are not - at least in liver and muscle - cAMP-associated. Here we have investigated the effect, its characteristics, and possible second messengers of GLP-1 on the glucose metabolism of human skeletal muscle, in tissue strips and primary cultured myocytes. In muscle strips, GLP-1, like insulin, stimulated glycogen synthesis, glycogen synthase a activity, and glucose oxidation and utilization, and inhibited glycogen phosphorylase a activity, all of this at physiological concentrations of the peptide. In cultured myotubes, GLP-1 exerted, from 10(-13) mol/l, a dose-related increase of the D-[U-(14)C]glucose incorporation into glycogen, with the same potency as insulin, together with an activation of glycogen synthase a; the effect of 10(-11) mol/l GLP-1 on both parameters was additive to that induced by the equimolar amount of insulin. Synthase a was still activated in cells after 2 days of exposure to GLP-1, as compared with myotubes maintained in the absence of peptide. In human muscle cells, exendin-4 and its truncated form 9-39 amide (Ex-9) are both agonists of the GLP-1 effect on glycogen synthesis and synthase a activity; but while neither GLP-1 nor exendin-4 affected the cellular cAMP content after 5-min incubation in the absence of 3-isobutyl-1-methylxantine (IBMX), an increase was detected with Ex-9. GLP-1, exendin-4, Ex-9 and insulin all induced the prompt hydrolysis of glycosylphosphatidylinositols (GPIs). This work shows a potent stimulatory effect of GLP-1 on the glucose metabolism of human skeletal muscle, and supports the long-term therapeutic value of the peptide. Further evidence for a GLP-1 receptor in this tissue, different from that of the pancreas, is also illustrated, suggesting a role for an inositolphosphoglycan (IPG) as at least one of the possible second messengers of the GLP-1 action in human muscle.

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Alyce M Martin, Emily W Sun, and Damien J Keating

-like peptide 1 (GLP-1), peptide YY (PYY) and oxyntomodulin (OXM), and glucose-dependent insulinotropic peptide (GIP) secreting K cells. It is now clear that such a classification system is not accurate given the accumulation of evidence that cross-over in

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Sara Baldassano, Anna Lisa Bellanca, Rosa Serio, and Flavia Mulè

were in compliance with the guidelines of the European Communities Council Directive of 24 November 1986. Diets After 1 week of free access to a pelletized rodent diet (GLP4RF21; Mucedola, S.r.L. Italy), mice were divided into two groups. One group were

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K K Sidhu, R C Fowkes, R H Skelly, and J M Burrin

Introduction Glucagon-like peptide 1 (GLP-1) is a proglucagon-derived peptide hormone that is synthesized and secreted by intestinal L-cells in response to the ingestion of nutrients and circulates to the pancreas where it stimulates

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L van Bloemendaal, J S ten Kulve, S E la Fleur, R G Ijzerman, and M Diamant

), oxyntomodulin (OXM) and glucagon-like peptide 1 (GLP-1), have been identified as players in the regulation of feeding by relaying meal-related information on nutritional status to the brain. Based on more than three decades of experimental evidence from rodent

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Hongbin Liu, Yunshan Hu, Richard W Simpson, and Anthony E Dear

Introduction Glucagon-like peptide-1 (GLP-1), an incretin first identified in 1984, has been proposed as a potential candidate target for therapy in the treatment of type 2 diabetes ( Nauck et al . 1993 , Edwards 2005 ). GLP-1, the product of the

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Neville H McClenaghan, Peter R Flatt, and Andrew J Ball

-cell desensitisation compared with sulphonylureas may occur following prolonged exposure to nateglinide ( Ball et al. 2004 b ). In vivo , insulin secretion can be stimulated by glucagon-like peptide-1 (GLP-1), a hormone of the enteroinsular axis, released

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Antonella Amato, Sara Baldassano, Rosa Liotta, Rosa Serio, and Flavia Mulè

Introduction Glucagon-like peptide 1 (GLP1), produced by intestinal enteroendocrine L-cells in response to the ingestion of nutrients ( Schirra et al . 1996 ), is highly insulinotropic and an inhibitor of gastrointestinal motility, effects that

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Raylene A Reimer

Introduction Glucagon-like peptide-1 (GLP-1) is a gut hormone released from intestinal L-cells in response to food ingestion ( Kieffer & Habener 1999 ). In addition to potentiating glucose-dependent insulin secretion, GLP-1

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Guillaume Mabilleau, Aleksandra Mieczkowska, Nigel Irwin, Peter R Flatt, and Daniel Chappard

al . 2010 ). Glucagon-like peptide-1 (GLP1) is a gut hormone synthesized and secreted into the blood stream by intestinal endocrine L cells in response to a variety of stimuli ( Wu et al . 2010 ). Biologically active GLP1 is secreted as a 7–37 or 7