Exenatide does not evoke pancreatitis and attenuates chemically induced pancreatitis in normal and diabetic rodents

Abstract

The risk of developing pancreatitis is elevated in type 2 diabetes and obesity. Cases of pancreatitis have been reported in type 2 diabetes patients treated with GLP-1 (GLP-1R) receptor agonists. To examine whether the GLP-1R agonist exenatide potentially induces or modulates pancreatitis, the effect of exenatide was evaluated in normal or diabetic rodents. Normal and diabetic rats received a single exenatide dose (0.072, 0.24, and 0.72 nmol/kg) or vehicle. Diabetic ob/ob or HF-STZ mice were infused with exenatide (1.2 and 7.2 nmol·kg(-1)·day(-1)) or vehicle for 4 wk. Post-exenatide treatment, pancreatitis was induced with caerulein (CRN) or sodium taurocholate (ST), and changes in plasma amylase and lipase were measured. In ob/ob mice, plasma cytokines (IL-1β, IL-2, IL-6, MCP-1, IFNγ, and TNFα) and pancreatitis-associated genes were assessed. Pancreata were weighed and examined histologically. Exenatide treatment alone did not modify plasma amylase or lipase in any models tested. Exenatide attenuated CRN-induced release of amylase and lipase in normal rats and ob/ob mice but did not modify the response to ST infusion. Plasma cytokines and pancreatic weight were unaffected by exenatide. Exenatide upregulated Reg3b but not Il6, Ccl2, Nfkb1, or Vamp8 expression. Histological analysis revealed that the highest doses of exenatide decreased CRN- or ST-induced acute inflammation, vacuolation, and acinar single cell necrosis in mice and rats, respectively. Ductal cell proliferation rates were low and similar across all groups of ob/ob mice. In conclusion, exenatide did not modify plasma amylase and lipase concentrations in rodents without pancreatitis and improved chemically induced pancreatitis in normal and diabetic rodents.

Fig. 1.

Plasma amylase (A–C) and lipase (D–F) in rats dosed with single subcutaneous (sc) injections of different doses of exenatide (Ex; 0.072, 0.24, or 0.72 nmol/kg) or vehicle. A and B: time course of amylase in normal Harlan Sprague Dawley (HSD) and Zucker diabetic fatty (ZDF) rats, respectively. C: calculated area under the curve (AUC)_{0–6 h} for amylase. D and E: time course of lipase in HSD and ZDF rats, respectively. F: calculated AUC_{0–6 h} for lipase; n = 4–6/group. No statistically significant differences between Ex- and vehicle-treated groups were found for amylase or lipase.

Fig. 2.

Plasma amylase (A and B) and lipase (C and D) over time in diabetic mice dosed with Ex via continuous sc infusions for 4 wk. A and C: diabetic ob/ob mice were treated with Ex (1.2 or 7.2 nmol·kg⁻¹·day⁻¹) or with vehicle. Wild-type (WT) control mice were infused with vehicle. B and D: diabetic high-fat (HF)-streptozotocin (STZ) mice were treated with Ex (7.2 nmol·kg⁻¹·day⁻¹) or vehicle. Nondiabetic controls, which did not receive STZ, were infused with vehicle; n = 8–10/group.

Fig. 3.

Time course of plasma amylase (A–C) and lipase (D–F) in rats dosed with Ex followed by chemically induced acute pancreatitis. Normal HSD, diabetic ZDF, or normal Wistar rats received a single sc dose of Ex (0.072, 0.24, or 0.72 nmol/kg) or vehicle. Sham-operated Wistar rats received vehicle. Ex, caerulein (CRN), or sodium taurocholate (ST) dosing is indicated by arrows. A, B, and C: plasma amylase for HSD, ZDF, and Wistar rats, respectively. D, E, and F: plasma lipase for HSD, ZDF, and Wistar rats, respectively; n = 6–7/group.

Fig. 4.

Time course of plasma amylase (A) and lipase (C) during CRN-induced pancreatitis in diabetic ob/ob mice pretreated with continuous sc infusion of different doses of exenatide (1.2 or 7.2 nmol·kg⁻¹·day⁻¹) or with vehicle for 4 wk. Strain-matched WT mice were pretreated with vehicle. CRN dosing is indicated by arrows. B and D: calculated 6-h plasma amylase (B) and lipase (D) AUC; n = 8–10/group. *P < 0.05, Ex (7.2 nmol·kg⁻¹·day⁻¹) or vehicle-dosed WT vs. vehicle-dosed ob/ob mice.

Fig. 5.

Pancreatic histology. A: representative sections of pancreata from diabetic ob/ob mice treated with continuous sc infusion of Ex (7.2 nmol·kg⁻¹·day⁻¹) for 4 wk, followed by CRN-induced pancreatitis. White bar represents 100 μm. B: cells in the cell cycle stained positive for Ki-67 (red) and are indicated by white arrows. Ductal epithelial cells stained positive for pan-cytokeratin (pan-CK; green) and nuclei were counterstained with 4,6-diamidino-2-phenylindole (blue). C: quantification of ductal cell proliferation rates presented as the percentage of Ki-67-positive cells within pan-CK-positive cells; n = 10/group. No statistically significant differences between groups were found (P = 0.11).

Fig. 6.

Effects of Ex on gene expression in the pancreas at 6 h post-CRN-induced acute pancreatitis in diabetic ob/ob mice treated with continuous sc infusion of different doses of Ex or vehicle for 4 wk. Strain-matched WT mice were treated with vehicle infusions and were subject to CRN-induced pancreatitis as well; n = 9–10/group. *P < 0.05, Ex (7.2 nmol·kg⁻¹·day⁻¹) or WT vs. vehicle-dosed ob/ob mice.