scholarly journals The Glucagon-Like Peptide-1 Receptor Agonist Oxyntomodulin Enhances β-Cell Function but Does Not Inhibit Gastric Emptying in Mice

Endocrinology ◽  
2008 ◽  
Vol 149 (11) ◽  
pp. 5670-5678 ◽  
Author(s):  
Adriano Maida ◽  
Julie A. Lovshin ◽  
Laurie L. Baggio ◽  
Daniel J. Drucker
Keyword(s):  
Blood Glucose ◽  
Amino Acid ◽  
Gastric Emptying ◽  
Food Intake ◽  
Oral Glucose ◽  
Dependent Manner ◽  
Glucose Administration ◽  
Amino Acid Peptide ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1

The proglucagon gene gives rise to multiple peptides that play diverse roles in the control of energy intake, gut motility, and nutrient disposal. Glucagon-like peptide-1 (GLP-1), a 30-amino-acid peptide regulates glucose homeostasis via control of insulin and glucagon secretion and by inhibition of gastric emptying and food intake. Oxyntomodulin (OXM) a 37-amino-acid peptide also derived from the proglucagon gene, binds to both the glucagon and GLP-1 receptor (GLP-1R); however, a separate OXM receptor has not yet been identified. Here we show that OXM, like other GLP-1R agonists, stimulates cAMP formation and lowers blood glucose after both oral and ip glucose administration, actions that require a functional GLP-1R. OXM also directly stimulates insulin secretion from murine islets and INS-1 cells in a glucose- and GLP-1R-dependent manner. Moreover, OXM ameliorates hyperglycemia and significantly reduces apoptosis in murine β-cells after streptozotocin administration and directly reduces apoptosis in thapsigargin-treated INS-1 cells. Unexpectedly, OXM, but not the GLP-1R agonist exendin-4, increased plasma levels of insulin after oral glucose administration. Moreover, OXM administered at doses that potently lower blood glucose had no effect on inhibition of gastric emptying but reduced food intake in WT mice. Taken together, these findings illustrate that although structurally distinct proglucagon-derived peptides such as GLP-1 and OXM engage the GLP-1R, OXM mimics some but not all of the actions of GLP-1R agonists in vivo. These findings may have implications for therapeutic efforts using OXM as a long-acting GLP-1R agonist for the treatment of metabolic disorders.

Long-term metabolic benefits of exenatide in mice are mediated solely via the known glucagon-like peptide 1 receptor

2014 ◽  
Vol 306 (7) ◽  
pp. R490-R498 ◽  
Author(s):  
Krystyna Tatarkiewicz ◽  
Emmanuel J. Sablan ◽  
Clara J. Polizzi ◽  
Christiane Villescaz ◽  
David G. Parkes
Keyword(s):  
Body Weight ◽  
Gastric Emptying ◽  
Food Intake ◽  
High Fat Diet ◽  
Tolerance Test ◽  
Metabolic Effects ◽  
Oral Glucose ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1

Glucagon-like peptide 1 receptors (GLP-1R) are expressed in multiple tissues and activation results in metabolic benefits including enhanced insulin secretion, slowed gastric emptying, suppressed food intake, and improved hepatic steatosis. Limited and inconclusive knowledge exists regarding whether the effects of chronic exposure to a GLP-1R agonist are solely mediated via this receptor. Therefore, we examined 3-mo dosing of exenatide in mice lacking a functional GLP-1R (Glp1r−/−). Exenatide (30 nmol·kg−1·day−1) was infused subcutaneously for 12 wk in Glp1r−/− and wild-type (Glp1r+/+) control mice fed a high-fat diet. Glycated hemoglobin A1c (HbA1c), plasma glucose, insulin, amylase, lipase, alanine aminotransferase (ALT), aspartate aminotransferase (AST), body weight, food intake, terminal hepatic lipid content (HLC), and plasma exenatide levels were measured. At the end of the study, oral glucose tolerance test (OGTT) and rate of gastric emptying were assessed. Exenatide produced no significant changes in Glp1r−/− mice at study end. In contrast, exenatide decreased body weight, food intake, and glucose in Glp1r+/+ mice. When compared with vehicle, exenatide reduced insulin, OGTT glucose AUC0–2h, ALT, and HLC in Glp1r+/+ mice. Exenatide had no effect on plasma amylase or lipase levels. Exenatide concentrations were approximately eightfold higher in Glp1r−/− versus Glp1r+/+ mice after 12 wk of infusion, whereas renal function was similar. These data support the concept that exenatide requires a functional GLP-1R to exert chronic metabolic effects in mice, and that novel “GLP-1” receptors may not substantially contribute to these changes. Differential exenatide plasma levels in Glp1r+/+ versus Glp1r−/− mice suggest that GLP-1R may play an important role in plasma clearance of exenatide and potentially other GLP-1-related peptides.

scholarly journals The Effects of Sleeve Gastrectomy on Glucose Metabolism and Glucagon-Like Peptide 1 in Goto-Kakizaki Rats

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Laiyuan Li ◽  
Xiaolin Wang ◽  
Liangliang Bai ◽  
Huichuan Yu ◽  
Zenghong Huang ◽  
...  
Keyword(s):  
Body Weight ◽  
Sleeve Gastrectomy ◽  
Blood Glucose ◽  
Food Intake ◽  
Glucose Metabolism ◽  
Tolerance Test ◽  
Oral Glucose ◽  
Gk Rats ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1

Purpose. To investigate the effects of sleeve gastrectomy (SG) on glucose metabolism and changes in glucagon-like peptide 1 (GLP-1) in Goto-Kakizaki (GK) rats. Methods. GK rats were randomly assigned to one of three groups: SG, SG pair-fed plus sham surgery (PF-sham), and ad libitum-fed no surgery (control). Food intake, body weight, blood glucose, GLP-1 and insulin levels, and GLP-1 expression in the jejunum and ileum were compared. Results. The SG rats exhibited lower postoperative food intake, body weight, and fasting glucose than did the control rats (P<0.05). SG significantly improved glucose and insulin tolerance (P<0.05). Plasma GLP-1 levels were higher in SG rats than in control or PF-sham rats in the oral glucose tolerance test (OGTT) (P<0.05). Blood glucose levels expressed as a percentage of baseline were higher in SG rats than in control rats after exendin (9-39) administration (P<0.05). The levels of GLP-1 expression in the jejunum and ileum were higher in SG rats than in PF-sham and control rats (P<0.05). Conclusions. Improvement of glucose metabolism by SG was associated with increased GLP-1 secretion. SG contributes to an increase in plasma GLP-1 levels via increased GLP-1 expression in the mucosa of the jejunum and/or ileum.

Central glucagon-like peptide 1 receptor-induced anorexia requires glucose metabolism-mediated suppression of AMPK and is impaired by central fructose

2013 ◽  
Vol 304 (7) ◽  
pp. E677-E685 ◽  
Author(s):  
Melissa A. Burmeister ◽  
Jennifer Ayala ◽  
Daniel J. Drucker ◽  
Julio E. Ayala
Keyword(s):  
Food Intake ◽  
Glucose Metabolism ◽  
Dependent Manner ◽  
Anorectic Effect ◽  
Dependent Inhibition ◽  
Glycolytic Inhibitor ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1 ◽  
Amp Activated Protein Kinase ◽  
Mediated Reduction

Glucagon-like peptide-1 (GLP-1) suppresses food intake via activation of a central (i.e., brain) GLP-1 receptor (GLP-1R). Central AMP-activated protein kinase (AMPK) is a nutrient-sensitive regulator of food intake that is inhibited by anorectic signals. The anorectic effect elicited by hindbrain GLP-1R activation is attenuated by the AMPK stimulator AICAR. This suggests that central GLP-1R activation suppresses food intake via inhibition of central AMPK. The present studies examined the mechanism(s) by which central GLP-1R activation inhibits AMPK. Supporting previous findings, AICAR attenuated the anorectic effect elicited by intracerebroventricular (icv) administration of the GLP-1R agonist exendin-4 (Ex-4). We demonstrate that Ex-4 stimulates glycolysis and suppresses AMPK phosphorylation in a glucose-dependent manner in hypothalamic GT1-7 cells. This suggests that inhibition of AMPK and food intake by Ex-4 requires central glucose metabolism. Supporting this, the glycolytic inhibitor 2-deoxyglucose (2-DG) attenuated the anorectic effect of Ex-4. However, icv glucose did not enhance the suppression of food intake by Ex-4. AICAR had no effect on Ex-4-mediated reduction in locomotor activity. We also tested whether other carbohydrates affect the anorectic response to Ex-4. Intracerebroventricular pretreatment with the sucrose metabolite fructose, an AMPK activator, attenuated the anorectic effect of Ex-4. This potentially explains the increased food intake observed in sucrose-fed mice. In summary, we propose a model whereby activation of the central GLP-1R reduces food intake via glucose metabolism-dependent inhibition of central AMPK. We also suggest that fructose stimulates food intake by impairing central GLP-1R action. This has significant implications given the correlation between sugar consumption and obesity.

scholarly journals The common hepatic branch of the vagus is not required to mediate the glycemic and food intake suppressive effects of glucagon-like-peptide-1

2011 ◽  
Vol 301 (5) ◽  
pp. R1479-R1485 ◽  
Author(s):  
Matthew R. Hayes ◽  
Scott E. Kanoski ◽  
Bart C. De Jonghe ◽  
Theresa M. Leichner ◽  
Amber L. Alhadeff ◽  
...  
Keyword(s):  
Food Intake ◽  
Vagal Afferents ◽  
Oral Glucose ◽  
Afferent Fibers ◽  
The Common ◽  
Vagal Afferent ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1 ◽  
And Control ◽  
Hepatic Branch

The incretin and food intake suppressive effects of intraperitoneally administered glucagon-like peptide-1 (GLP-1) involve activation of GLP-1 receptors (GLP-1R) expressed on vagal afferent fiber terminals. Central nervous system processing of GLP-1R-driven vagal afferents results in satiation signaling and enhanced insulin secretion from pancreatic-projecting vagal efferents. As the vast majority of endogenous GLP-1 is released from intestinal l-cells following ingestion, it stands to reason that paracrine GLP-1 signaling, activating adjacent GLP-1R expressed on vagal afferent fibers of gastrointestinal origin, contributes to glycemic and food intake control. However, systemic GLP-1R-mediated control of glycemia is currently attributed to endocrine action involving GLP-1R expressed in the hepatoportal bed on terminals of the common hepatic branch of the vagus (CHB). Here, we examine the hypothesis that activation of GLP-1R expressed on the CHB is not required for GLP-1's glycemic and intake suppressive effects, but rather paracrine signaling on non-CHB vagal afferents is required to mediate GLP-1's effects. Selective CHB ablation (CHBX), complete subdiaphragmatic vagal deafferentation (SDA), and surgical control rats received an oral glucose tolerance test (2.0 g glucose/kg) 10 min after an intraperitoneal injection of the GLP-1R antagonist, exendin-(9–39) (Ex-9; 0.5 mg/kg) or vehicle. CHBX and control rats showed comparable increases in blood glucose following blockade of GLP-1R by Ex-9, whereas SDA rats failed to show a GLP-1R-mediated incretin response. Furthermore, GLP-1(7–36) (0.5 mg/kg ip) produced a comparable suppression of 1-h 25% glucose intake in both CHBX and control rats, whereas intake suppression in SDA rats was blunted. These findings support the hypothesis that systemic GLP-1R mediation of glycemic control and food intake suppression involves paracrine-like signaling on GLP-1R expressed on vagal afferent fibers of gastrointestinal origin but does not require the CHB.

Incretin release from gut is acutely enhanced by sugar but not by sweeteners in vivo

2009 ◽  
Vol 296 (3) ◽  
pp. E473-E479 ◽  
Author(s):  
Yukihiro Fujita ◽  
Rhonda D. Wideman ◽  
Madeleine Speck ◽  
Ali Asadi ◽  
David S. King ◽  
...  
Keyword(s):  
Blood Glucose ◽  
Sweet Taste ◽  
Tolerance Test ◽  
Oral Glucose ◽  
Dependent Manner ◽  
Glucose Levels ◽  
Zucker Diabetic Fatty Rats ◽  
Glucagon Like Peptide 1

Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are released during meals from endocrine cells located in the gut mucosa and stimulate insulin secretion from pancreatic β-cells in a glucose-dependent manner. Although the gut epithelium senses luminal sugars, the mechanism of sugar sensing and its downstream events coupled to the release of the incretin hormones are not clearly elucidated. Recently, it was reported that sucralose, a sweetener that activates the sweet receptors of taste buds, triggers incretin release from a murine enteroendocrine cell line in vitro. We confirmed that immunoreactivity of α-gustducin, a key G-coupled protein involved in taste sensing, is sometimes colocalized with GIP in rat duodenum. We investigated whether secretion of incretins in response to carbohydrates is mediated via taste receptors by feeding rats the sweet-tasting compounds saccharin, acesulfame potassium, d-tryptophan, sucralose, or stevia. Oral gavage of these sweeteners did not reduce the blood glucose excursion to a subsequent intraperitoneal glucose tolerance test. Neither oral sucralose nor oral stevia reduced blood glucose levels in Zucker diabetic fatty rats. Finally, whereas oral glucose increased plasma GIP levels ∼4-fold and GLP-1 levels ∼2.5-fold postadministration, none of the sweeteners tested significantly increased levels of these incretins. Collectively, our findings do not support the concept that release of incretins from enteroendocrine cells is triggered by carbohydrates via a pathway identical to the sensation of “sweet taste” in the tongue.

scholarly journals Glucagon Like Peptide 1 and Evidence Around Diabetes Specific Nutrition

2019 ◽  
Vol 10 (2) ◽  
pp. 64-75
Author(s):  
ANSHU JOSHI ◽  
SAMEER RAO ◽  
GANESH KADHE
Keyword(s):  
Fatty Acids ◽  
Insulin Secretion ◽  
Gastric Emptying ◽  
Food Intake ◽  
Diabetes Management ◽  
Monounsaturated Fatty Acids ◽  
Complex Carbohydrate ◽  
Soluble Fibre ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1

There has been significant research and development in pharmaco-therapeutic molecules for management of type 2 diabetes mellitus (T2DM). Diabetes specific nutrition intervention & newer incretin-based therapies have gained a lot of attention. Since incretins play an essential role in augmenting the post-prandial release of insulin, it is important to understand the science behind incretins and modulation of same by diabetic-specific nutrition (DSN). The purpose of this article is to summarize the available science around glucagon like peptide 1 (GLP-1) and the known role of nutrition, particularly diabetes specific nutrition. Literature published in PubMed, Google scholar and Embase were studied up to the end of August 2018. The key words of GLP-1, T2DM and Nutrients were used in different combinations. It was found that macronutrient aspects of DSN like complex carbohydrate, soluble fibre, proteins and high monounsaturated fatty acids augment GLP-1 secretion from intestinal L-cells. This may be attributed to insulin-trophic effects of DSN as well as its effects in causing deceleration in gastric emptying and reducing food intake. Hence, it was concluded that augmenting GLP-1 secretion in response to the intake of certain nutrients helps in modulating insulin secretion, metabolic homeostasis as well as decelerating gastric emptying and reducing food intake. DSN increases endogenous GLP-1 secretion which in turn improves insulin secretion and sensitivity. Thus, integrating DSN in mainstay diabetes management plans may result in better glycaemic and metabolic controls, particularly when GLP-1 based therapies are concurrently in use. Key Messages: DSN containing complex carbohydrate, soluble fibre, proteins and high monounsaturated fatty acids (MUFAs) augments GLP-1 secretion which in turn improves insulin secretion and sensitivity.

Effects of intraduodenal glucose and fructose on antropyloric motility and appetite in healthy humans

2000 ◽  
Vol 278 (2) ◽  
pp. R360-R366 ◽  
Author(s):  
C. K. Rayner ◽  
H. S. Park ◽  
J. M. Wishart ◽  
M.-F. Kong ◽  
S. M. Doran ◽  
...  
Keyword(s):  
Blood Glucose ◽  
Food Intake ◽  
Plasma Insulin ◽  
Insulin Response ◽  
Oral Glucose ◽  
Inhibitory Peptide ◽  
Healthy Humans ◽  
Significant Difference ◽  
Glucagon Like Peptide 1 ◽  
Gip Release

Oral fructose empties from the stomach more rapidly and may suppress food intake more than oral glucose. The purpose of the study was to evaluate the effects of intraduodenal infusions of fructose and glucose on antropyloric motility and appetite. Ten healthy volunteers were given intraduodenal infusions of 25% fructose, 25% glucose, or 0.9% saline (2 ml/min for 90 min). Antropyloric pressures, blood glucose, and plasma insulin, gastric inhibitory peptide (GIP), and glucagon-like peptide-1 (GLP-1) were measured concurrently; a buffet meal was offered at the end of the infusion. Intraduodenal fructose and glucose suppressed antral waves ( P < 0.0005 for both), stimulated isolated pyloric pressure waves ( P < 0.05 for both), and increased basal pyloric pressure ( P = 0.10 and P < 0.05, respectively) compared with saline, without any significant difference between them. Intraduodenal glucose increased blood glucose ( P < 0.0005), as well as plasma insulin ( P < 0.0005) and GIP ( P < 0.005) more than intraduodenal fructose, whereas there was no difference in the GLP-1 response. Intraduodenal fructose suppressed food intake compared with saline ( P < 0.05) and glucose ( P = 0.07). We conclude that, when infused intraduodenally at 2 kcal/min for 90 min 1) fructose and glucose have comparable effects on antropyloric pressures, 2) fructose tends to suppress food intake more than glucose, despite similar GLP-1 and less GIP release, and 3) GIP, rather than GLP-1, probably accounts for the greater insulin response to glucose than fructose.

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