incretins and Hyperplasia

We reported that native incretins, liraglutide and dipeptidyl peptidase-4 inhibitors (DPP-4i) all confer an anti-atherosclerotic effect in apolipoprotein E-null (Apoe (-/-)) mice. We confirmed the anti-atherogenic property of incretin-related agents in the mouse wire injury model, in which the neointimal formation in the femoral artery is remarkably suppressed. Furthermore, we showed that DPP-4i substantially suppresses plaque formation in coronary arteries with a marked reduction in the accumulation of macrophages in cholesterol-fed rabbits. DPP-4i showed an anti-atherosclerotic effect in Apoe (-/-) mice mainly through the actions of glucagon-like peptide-1 and glucose-dependent insulinotropic polypepide. However, the dual incretin receptor antagonists partially attenuated the suppressive effect of DPP-4i on atherosclerosis in diabetic Apoe (-/-) mice, suggesting an incretin-independent mechanism. Exendin-4 and glucose-dependent insulinotropic polypepide elicited cyclic adenosine monophosphate generation, and suppressed the lipopolysaccharide-induced gene expression of inflammatory molecules, such as interleukin-1β, interleukin-6 and tumor necrosis factor-α, in U937 human monocytes. This suppressive effect, however, was attenuated by an inhibitor of adenylate cyclase and mimicked by 8-bromo-cyclic adenosine monophosphate or forskolin. DPP-4i substantially suppressed the lipopolysaccharide-induced expression of inflammatory cytokines without affecting cyclic adenosine monophosphate generation or cell proliferation. DPP-4i more strongly suppressed the lipopolysaccharide-induced gene expression of inflammatory molecules than incretins, most likely through inactivation of CD26. Glucagon-like peptide-1 and glucose-dependent insulinotropic polypepide suppressed oxidized low-density lipoprotein-induced macrophage foam cell formation in a receptor-dependent manner, which was associated with the downregulation of acyl-coenzyme A cholesterol acyltransferase-1 and CD36, as well as the up-regulation of adenosine triphosphate-binding cassette transporter A1. Our studies strongly suggest that incretin-related agents have favorable effects on macrophage-driven atherosclerosis in experimental animals.

Topics: Animals; Anti-Inflammatory Agents; Apolipoproteins E; Atherosclerosis; Coronary Restenosis; Dipeptidyl-Peptidase IV Inhibitors; Disease Models, Animal; Foam Cells; Gastric Inhibitory Polypeptide; Glucagon-Like Peptide 1; Humans; Hyperplasia; Incretins; Inflammation; Inflammation Mediators; Liraglutide; Macrophages; Mice; Mice, Knockout; Monocytes

Pancreatic α-cell hyperplasia (ACH) was once an esoteric pathological entity, but it has become an important differential diagnosis of hyperglucagonemia after inactivating glucagon receptor (GCGR) genomic mutations were found in patients with ACH. Recently, the controversy over the pancreatic effects of incretins has stimulated much discussion of ACH that often includes inaccurate statements not supported by the literature.. Literature related to ACH was reviewed.. ACH is defined as a diffuse and specific increase in the number of α-cells. A dozen cases have been reported and fall into three clinical types: reactive, functional, and nonfunctional. Characterized by remarkable hyperglucagonemia without glucagonoma syndrome, reactive ACH is caused by inactivating GCGR mutations, and its main clinical significance is pancreatic neuroendocrine tumors diagnosed at middle age. The Gcgr(-/-) mice, a model of reactive ACH, exhibit a multistage tumorigenesis in their pancreata. Pharmacological agents that inhibit glucagon signaling also cause reactive ACH in animals and possibly in humans as well. The pancreata of incretin-treated humans and those of reactive ACH murine models share similarities. Functional ACH features hyperglucagonemia with glucagonoma syndrome. Nonfunctional ACH is associated with normal glucagon levels. The causes of functional and nonfunctional ACH are unknown as yet.. ACH is a histological diagnosis and clinically heterogeneous. Caused by GCGR mutations, reactive ACH is a preneoplastic lesion giving rise to slow-developing pancreatic neuroendocrine tumors. The effects of treatments targeting glucagon signaling in this regard remain controversial. The strong negative feedback control of glucagon signaling conserved in all mammals studied, including humans, makes long-term pancreatic tumor surveillance advisable for the glucagon signaling-targeting therapies.

Topics: Animals; Diabetes Mellitus; Disease Models, Animal; Glucagon-Secreting Cells; Humans; Hyperplasia; Incretins; Mice; Mice, Knockout; Pancreatic Diseases; Receptors, Glucagon

Controversy exists regarding the potential regenerative influences of incretin therapy on pancreatic β-cells versus possible adverse pancreatic proliferative effects. Examination of pancreata from age-matched organ donors with type 2 diabetes mellitus (DM) treated by incretin therapy (n = 8) or other therapy (n = 12) and nondiabetic control subjects (n = 14) reveals an ∼40% increased pancreatic mass in DM treated with incretin therapy, with both increased exocrine cell proliferation (P < 0.0001) and dysplasia (increased pancreatic intraepithelial neoplasia, P < 0.01). Pancreata in DM treated with incretin therapy were notable for α-cell hyperplasia and glucagon-expressing microadenomas (3 of 8) and a neuroendocrine tumor. β-Cell mass was reduced by ∼60% in those with DM, yet a sixfold increase was observed in incretin-treated subjects, although DM persisted. Endocrine cells costaining for insulin and glucagon were increased in DM compared with non-DM control subjects (P < 0.05) and markedly further increased by incretin therapy (P < 0.05). In conclusion, incretin therapy in humans resulted in a marked expansion of the exocrine and endocrine pancreatic compartments, the former being accompanied by increased proliferation and dysplasia and the latter by α-cell hyperplasia with the potential for evolution into neuroendocrine tumors.

Topics: Adenoma; Adolescent; Adult; Aged; Cell Proliferation; Diabetes Mellitus, Type 2; Dipeptidyl-Peptidase IV Inhibitors; Female; Humans; Hyperplasia; Incretins; Insulin-Secreting Cells; Male; Middle Aged; Neuroendocrine Tumors; Organ Size; Pancreas; Pyrazines; Sitagliptin Phosphate; Triazoles

Topics: Diabetes Mellitus, Type 2; Glucagon-Like Peptide 1; Humans; Hyperplasia; Incretins; Metaplasia; Pancreas; Pancreatic Neoplasms; Pancreatitis

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