exenatide and glucagon-like-peptide-1-(7-36)

Glucagon-like peptide-1 (GLP-1) and its mimetics reduce infarct size in the setting of acute myocardial ischemia/reperfusion (I/R) injury. However, the short serum half-life of GLP-1 and its mimetics may limit their therapeutic use in acute myocardial ischemia. Domain antibodies to serum albumin (AlbudAbs) have been developed to extend the serum half-life of short lived therapeutic proteins, peptides and small molecules. In this study, we compared the effect of a long acting GLP-1 agonist, DPP-IV resistant GLP-1 (7-36, A8G) fused to an AlbudAb (GAlbudAb), with the effect of the GLP-1 mimetic, exendin-4 (short half-life GLP-1 agonist) on infarct size following acute myocardial I/R injury.. Male Sprague-Dawley rats (8-week-old) were treated with vehicle, GAlbudAb or exendin-4. Myocardial ischemia was induced 2 h following the final dose for GAlbudAb and 30 min post the final dose for exendin-4. In a subgroup of animals, the final dose of exendin-4 was administered (1 μg/kg, SC, bid for 2 days) 6 h prior to myocardial ischemia when plasma exendin-4 was at its minimum concentration (C(min)). Myocardial infarct size, area at risk and cardiac function were determined 24 h after myocardial I/R injury.. GAlbudAb and exendin-4 significantly reduced myocardial infarct size by 28% and 23% respectively, compared to vehicle (both p < 0.01 vs. vehicle) after I/R injury. Moreover, both GAlbudAb and exendin-4 markedly improved post-ischemic cardiac contractile function. Body weight loss and reduced food intake consistent with the activation of GLP-1 receptors was observed in all treatment groups. However, exendin-4 failed to reduce infarct size when administered 6 h prior to myocardial ischemia, suggesting continuous activation of the GLP-1 receptors is needed for cardioprotection.. Cardioprotection provided by GAlbudAb, a long acting GLP-1 mimetic, following myocardial I/R injury was comparable in magnitude, but more sustained in duration than that produced by short-acting exendin-4. Very low plasma concentrations of exendin-4 failed to protect the heart from myocardial I/R injury, suggesting that sustained GLP-1 receptor activation plays an important role in providing cardioprotection in the setting of acute myocardial I/R injury. Long-acting GLP-1 agonists such as GAlbudAb may warrant additional evaluation as novel therapeutic agents to reduce myocardial I/R injury during acute coronary syndrome.

Topics: Animals; Cardiotonic Agents; Disease Models, Animal; Exenatide; Glucagon-Like Peptide 1; Glucagon-Like Peptide-1 Receptor; Immunoconjugates; Injections, Subcutaneous; Male; Myocardial Contraction; Myocardial Infarction; Myocardial Reperfusion Injury; Myocardium; Peptide Fragments; Peptides; Rats; Rats, Sprague-Dawley; Receptors, Glucagon; Serum Albumin; Single-Domain Antibodies; Venoms; Ventricular Function, Left

We investigated the vascular effects of glucagon-like peptide-1 (GLP-1) and Exendin-4 in type 2 diabetic rat aortae. Studies were performed in a normal control group (NC) (0.2 ml i.p. saline, n = 10), streptozotocin (STZ)/nicotinamide diabetic control group (DC) (a single dose of 80 mg/kg STZ i.p. injection 15 min after administration of 230 mg/kg nicotinamide i.p.), GLP-1 (GLPC) control group (1 microg/kg twice daily i.p. for 1 month, n = 10), Exendin-4 control group (EXC) (0.1 microg/kg twice daily i.p. for 1 month, n = 10), GLP-1-treated diabetic group (GLPT) (1 microg/kg twice daily i.p. for 1 month, n = 10), and Exendin-4-treated diabetic group (EXT) (0.1 microg/kg twice daily i.p. for 1 month, n = 10). One month of GLP-1 and Exendin-4 treatment significantly decreased the blood glucose levels of diabetic rats (113 +/- 2 mg/dl, p < 0.001, and 117 +/- 1 mg/dl, p < 0.001, respectively versus 181 +/- 9 mg/dl in the DC group). Sensitivity (pD2) and maximum response (% Max. Relax) of acetylcholine-stimulated relaxations in the DC group (pD2: 6.73 +/- 0.12 and 55 +/- 6, respectively) were decreased compared with the non-diabetic NC group (pD2: 7.41 +/- 0.25, p < 0.05, and 87 +/- 4, p < 0.01). Treating diabetic rats with GLP-1, pD2 values and with Exendin-4, Max. Relax %values of aortic strips to acetylcholine returned to near non-diabetic NC values (pD2: 7.47 +/- 0.15, p < 0.05, and 87 +/- 3, p < 0.01, respectively). Maximal contractile responses (Emax) to noradrenaline in aortic strips from the diabetic DC group (341 +/- 27 mg tension/mg wet weight) were significantly decreased compared with the non-diabetic NC (540 +/- 66 mg tension/mg wet weight, p < 0.001) and the GLPT group (490 +/- 25 mg tension/mg wet weight, p < 0.05). There were no significant differences in pD2 values of aortic strips to noradrenaline from all groups. Emax to KCl in aortic strips from the DC group (247 +/- 10 mg tension/mg wet weight, p < 0.01) was significantly decreased compared with non-diabetic NC group (327 +/- 26 mg tension/mg wet weight). Treating diabetic rats with GLP-1 (GLPT), Emax values of aortic strips to KCl returned to near non-diabetic NC values (271 +/- 12 mg tension/mg wet weight). GLP-1 and (partially) Exendin-4 treatment could improve the increased blood glucose level and normalize the altered vascular tone in type 2 diabetic rats.

Topics: Animals; Aorta, Thoracic; Blood Glucose; Diabetes Mellitus, Experimental; Dose-Response Relationship, Drug; Exenatide; Female; Glucagon; Glucagon-Like Peptide 1; Glucagon-Like Peptides; In Vitro Techniques; Male; Muscle Relaxation; Muscle, Smooth, Vascular; Niacinamide; Oxidative Stress; Peptide Fragments; Peptides; Rats; Rats, Wistar; Streptozocin; Vasodilator Agents; Venoms

The aim of this study was to determine whether rapid conversion to inactive and potentially antagonistic peptides could alter the response to GLP-1.. We evaluated the ability of exendin-4, a GLP-1 analogue resistant to degradation by dipeptidyl peptidase IV, to modulate insulin-induced stimulation of glucose uptake and suppression of glucose production in eight healthy subjects during infusion of GLP-1 (1.2 pmol.kg(-1).min(-1)), exendin-4 (0.12 pmol.kg(-1).min(-1)), or saline. Glucose was clamped at 5.3 mmol/l and insulin was infused to progressively increase insulin concentrations to about 65, 190 and 700 pmol/l, respectively. Endogenous insulin secretion was inhibited with somatostatin to ensure comparable portal insulin concentrations while glucagon and growth hormone were maintained at basal concentrations.. Glucose, insulin, C-peptide, glucagon and growth hormone concentrations did not differ on the three occasions. In contrast, cortisol concentrations were greater during both exendin-4 (25.1+/-4.4 mmol/l per 7 h; p<0.01) and GLP-1, (17.0+/-2.0 mmol/l 7 h; p<0.05) than saline (13.5+/-1.5 mmol/l per 7 h). While insulin-induced stimulation of glucose disappearance at the highest insulin concentrations tended to be greater and insulin-induced suppression of glucose production lower in the presence of exendin-4 or GLP-1 than saline, the differences were not significant.. Exendin-4 and GLP-1 increase cortisol secretion in human subjects. However, neither alters insulin action in non-diabetic human subjects. These data also suggest that the lack of an effect of GLP-1 on insulin action is not likely to be explained by rapid degradation to inactive or antagonistic peptides.

Topics: Adult; Animals; Biotransformation; Blood Glucose; Body Mass Index; C-Peptide; Dipeptidyl Peptidase 4; Exenatide; Glucagon; Glucagon-Like Peptide 1; Glucagon-Like Peptides; Human Growth Hormone; Humans; Hydrocortisone; Infusions, Intravenous; Insulin; Kinetics; Lizards; Peptide Fragments; Peptides; Reference Values; Venoms

Helodermin and exendin-4, two peptides isolated from the salivary gland of the Gila monster, Heloderma suspectum, are approximately 50% homologous to vasoactive intestinal peptide (VIP) and glucagon-like peptide-1 (GLP-1), respectively, and interact with the mammalian receptors for VIP and GLP-1 with equal or higher affinity and efficacy. Immunohistochemical studies suggested the presence of helodermin-like peptides in mammals. To determine whether helodermin and exendin-4 are present in mammals and their evolutionary relationship to VIP and GLP-1, their cDNAs were first cloned from Gila monster salivary gland. Northern blots and reverse transcription-polymerase chain reaction of multiple Gila monster tissues identified approximately 500-base pair transcripts only from salivary gland. Both helodermin and exendin-4 full-length cDNAs were approximately 500 base pairs long, and they encoded precursor proteins containing the entire amino acid sequence of helodermin and exendin-4, as well as a 44- or 45-amino acid N-terminal extension peptide, respectively, having approximately 60% homology. The size and structural organization of these cDNAs indicated that they were closely related to one another but markedly different from known cDNAs for the VIP/GLP-1 peptide family previously identified in both lower and higher evolved species. Cloning of the Gila monster VIP/peptide histidine isoleucine, pituitary adenylate cyclase activating polypeptide, and glucagon/GLP-1 cDNAs and Southern blotting of Gila monster DNA demonstrate the coexistence of separate genes for these peptides and suggests, along with the restricted salivary gland expression, that helodermin and exendin-4 coevolved to serve a separate specialized function. Probing of a variety of rat and human tissues on Northern blots, human and rat Southern blots, and genomic and cDNA libraries with either helodermin- or exendin-4-specific cDNAs failed to identify evidence for mammalian homologues. These data indicate that helodermin and exendin-4 are not the precursors to VIP and GLP-1 and that they belong to a separate peptide family encoded by separate genes. Furthermore, the existence of as yet undiscovered mammalian homologues to helodermin and exendin-4 seems unlikely.

Topics: Amino Acid Sequence; Animals; Base Sequence; Chickens; Cloning, Molecular; DNA Primers; DNA, Complementary; Exenatide; Glucagon; Glucagon-Like Peptide 1; Glucagon-Like Peptides; Humans; Intercellular Signaling Peptides and Proteins; Lizards; Mammals; Molecular Sequence Data; Neuropeptides; Peptide Fragments; Peptides; Pituitary Adenylate Cyclase-Activating Polypeptide; Polymerase Chain Reaction; Protein Precursors; Rats; Recombinant Proteins; Sequence Alignment; Sequence Homology, Amino Acid; Trout; Vasoactive Intestinal Peptide; Venoms