exenatide and Hyperplasia

In this study, we aimed to evaluate the effects of exenatide (EXE) treatment on exocrine pancreas of nonhuman primates. To this end, 52 baboons (Papio hamadryas) underwent partial pancreatectomy, followed by continuous infusion of EXE or saline (SAL) for 14 weeks. Histological analysis, immunohistochemistry, Computer Assisted Stereology Toolbox morphometry, and immunofluorescence staining were performed at baseline and after treatment. The EXE treatment did not induce pancreatitis, parenchymal or periductal inflammatory cell accumulation, ductal hyperplasia, or dysplastic lesions/pancreatic intraepithelial neoplasia. At study end, Ki-67-positive (proliferating) acinar cell number did not change, compared with baseline, in either group. Ki-67-positive ductal cells increased after EXE treatment (P = 0.04). However, the change in Ki-67-positive ductal cell number did not differ significantly between the EXE and SAL groups (P = 0.13). M-30-positive (apoptotic) acinar and ductal cell number did not change after SAL or EXE treatment. No changes in ductal density and volume were observed after EXE or SAL. Interestingly, by triple-immunofluorescence staining, we detected c-kit (a marker of cell transdifferentiation) positive ductal cells co-expressing insulin in ducts only in the EXE group at study end, suggesting that EXE may promote the differentiation of ductal cells toward a β-cell phenotype. In conclusion, 14 weeks of EXE treatment did not exert any negative effect on exocrine pancreas, by inducing either pancreatic inflammation or hyperplasia/dysplasia in nonhuman primates.

Topics: Amylases; Animals; Apoptosis; Exenatide; Female; Hyperplasia; Hypoglycemic Agents; Immunohistochemistry; Inflammation; Infusions, Intravenous; Insulin Resistance; Ki-67 Antigen; Male; Microscopy, Fluorescence; Pancreas, Exocrine; Pancreatic Ducts; Papio; Peptides; Phenotype; Venoms

Diabetic patients have an increased risk of restenosis and late stent thrombosis after angioplasty, i.e. complications that are related to a defective re-endothelialization. Exendin-4, a stable glucagon-like peptide (GLP)-1 receptor agonist, has been suggested to influence the formation of intimal hyperplasia and to increase endothelial cell proliferation in vitro. Thus, the aim of this study was to investigate the mechanisms by which treatment with exendin-4 could influence re-endothelialization and intimal hyperplasia after vascular injury.. Sprague-Dawley rats were subjected to balloon injury of the left common carotid artery and treated for 4 weeks with exendin-4 or vehicle. Intimal hyperplasia and vessel wall elasticity were monitored noninvasively by high-frequency ultrasound, and re-endothelialization was evaluated upon sacrifice using Evans blue dye.. Exendin-4 selectively reduced the proliferation of smooth muscle cells (SMCs) and intimal hyperplasia in vivo without affecting the re-endothelialization process, but treatment with exendin-4 improved arterial wall elasticity. Our data also show that exendin-4 significantly decreased the proliferation and increased the apoptosis of SMCs in vitro, effects that appear to be mediated through cAMP signaling and endothelial nitric oxide synthase following GLP-1 receptor activation. Together, these effects of exendin-4 are highly desirable and may lead to an improved outcome for patients undergoing vascular interventions.

Topics: Animals; Blood Glucose; Carotid Artery Injuries; Carotid Artery, Common; Cell Division; Cells, Cultured; Cyclic AMP; Disease Models, Animal; Endothelium, Vascular; Exenatide; Fatty Acids, Nonesterified; Glucagon-Like Peptide-1 Receptor; Hyperplasia; Insulin; Male; Myocytes, Smooth Muscle; Nitric Oxide Synthase Type III; Peptides; Random Allocation; Rats; Rats, Sprague-Dawley; Receptors, Glucagon; Regeneration; Tunica Intima; Vascular Stiffness; Venoms

Glucagon-like peptide-1 is an incretin hormone from the gastrointestinal tract, which enhances insulin secretion, slows gastric emptying, and reduces food intake. GLP-1 receptor agonists are being developed for Type 2 diabetes mellitus. GLP-1 is rapidly degraded by serum dipeptidyl peptidase IV, so analogues with a prolonged serum half-life are used clinically. Exenatide was the first GLP-1 agonist approved and is a synthetic version of exendin-4 derived from the Gila monster. Liraglutide was approved for clinical use in 2010. GLP-1 receptor agonists have been shown to increase calcitonin secretion and stimulate C-cell hyperplasia and neoplasia in rats and mice of both sexes. Rat C-cells are more sensitive to the effects of GLP-1 agonists than mice. The effects of GLP-1 agonists on C-cell proliferation or neoplasia have not been documented in nonhuman primates or humans. The proliferative C-cell effects may be rodent-specific. GLP-1 receptors have been demonstrated on normal rodent C-cells, but are either not present or occur in low numbers on C-cells of nonhuman primates and humans. Hyperplasia and neoplasia of C-cells in rodents treated with GLP-1 agonists represent a unique example of an on-target species-specific effect that may not have relevance to humans.

Topics: Animals; Diabetes Mellitus, Type 2; Exenatide; Glucagon-Like Peptide 1; Glucagon-Like Peptide-1 Receptor; Humans; Hyperplasia; Hypoglycemic Agents; Immunohistochemistry; Liraglutide; Mice; Peptides; Rats; Receptors, Glucagon; Thyroid Gland; Thyroid Neoplasms; Venoms

A recent autopsy analysis asserted that incretin drugs have the potential of increasing the risk for pancreatic cancer and for pancreatic neuroendocrine tumors. We examined the Network for Pancreatic Organ Donors with Diabetes (nPOD) database from which that analysis was derived. Our findings raise important questions about the comparability of the two groups of diabetes patients used for the analysis. Our review of the data available on the nPOD Web site and our reading of the earlier article lead us to the conclusion that the data, and the implications of the data, as expressed by the authors of the autopsy analysis are vastly overstated and are a misrepresentation of the information available.

Topics: Adolescent; Adult; Aged; Databases, Factual; Diabetes Mellitus, Type 2; Dipeptidyl-Peptidase IV Inhibitors; Drug Therapy, Combination; Exenatide; Female; Glucagon-Like Peptide-1 Receptor; Humans; Hyperplasia; Hypoglycemic Agents; Incretins; Male; Middle Aged; Models, Statistical; Pancreas; Pancreatitis; Peptides; Pyrazines; Receptors, Glucagon; Sitagliptin Phosphate; Tissue Banks; Triazoles; Venoms; Young Adult

We studied the effect of a synthetic GLP-1 receptor agonist, exenatide, a drug approved for the treatment of type 2 diabetes, on the recovery from vascular injury in Zucker (non-diabetic) fatty rats. Exenatide 5.0 microg/kg per day or saline was administered for seven days before, and 21 days after balloon catheter mediated carotid injury. A pair feeding experiment helped differentiate between the drug itself and the known effects of the drug on decreased food intake. Body weight and glucose (weekly), carotid artery I/M ratio, aortic protein eNOS and NFkappaB-p65 were measured. Body weight gain in exenatide rats was significantly lower (53+/-5 vs. 89+/-8 g) than controls. Blood glucose did not change significantly. The I/M ratio in the exenatide group was 0.2+/-0.1 vs. 0.9+/-0.1 in controls (p<0.05). The expression of aortic eNOS was unchanged in exenatide treated rats and a small decrease seen in NFkappaB-p65 expression was not statistically significant. We conclude that exenatide attenuates intimal hyperplasia following balloon catheter induced vascular injury independently of glucose regulation and food intake. Our findings provide additional support for cardiovascular benefits of exenatide, especially in obese and pre-diabetic patients. Further research is needed to elucidate the mechanism underlying these effects.

Topics: Animals; Aorta; Carotid Artery Injuries; Eating; Exenatide; Female; Glucagon-Like Peptide-1 Receptor; Hyperplasia; Insulin Resistance; Nitric Oxide Synthase Type III; Peptides; Rats; Rats, Zucker; Receptors, Glucagon; Transcription Factor RelA; Tunica Intima; Venoms