Improvement of islet graft function using liraglutide is correlated with its anti-inflammatory properties.

BACKGROUND AND PURPOSE: Liraglutide improves the metabolic control of diabetic animals after islet transplantation. However, the mechanisms underlying this effect remain unknown. The objective of this study was to evaluate the anti-inflammatory and anti-oxidative properties of liraglutide on rat pancreatic islets in vitro and in vivo. EXPERIMENTAL APPROACH: In vitro, rat islets were incubated with 10 µmol·L-1 liraglutide for 12 and 24 h. Islet viability functionality was assessed. The anti-inflammatory properties of liraglutide were evaluated by measuring CCL2, IL-6 and IL-10 secretion and macrophage chemotaxis. The anti-oxidative effect of liraglutide was evaluated by measuring intracellular ROS and the total anti-oxidative capacity. In vivo, 1000 islets were cultured for 24 h with or without liraglutide and then transplanted into the liver of streptozotocin-induced diabetic Lewis rats with or without injections of liraglutide. Effects of liraglutide on metabolic control were evaluated for 1 month. KEY RESULTS: Islet viability and function were preserved and enhanced with liraglutide treatment. Liraglutide decreased CCL2 and IL-6 secretion and macrophage activation after 12 h of culture, while IL-10 secretion was unchanged. However, intracellular levels of ROS were increased with liraglutide treatment at 12 h. This result was correlated with an increase of anti-oxidative capacity. In vivo, liraglutide decreased macrophage infiltration and reduced fasting blood glucose in transplanted rats. CONCLUSIONS AND IMPLICATIONS: The beneficial effects of liraglutide on pancreatic islets appear to be linked to its anti-inflammatory and anti-oxidative properties. These findings indicated that analogues of glucagon-like peptide-1 could be used to improve graft survival.

Impact of the Type of Continuous Insulin Administration on Metabolism in a Diabetic Rat Model.

Exogenous insulin is the only treatment available for type 1 diabetic patients and is mostly administered by subcutaneous (SC) injection in a basal and bolus scheme using insulin pens (injection) or pumps (preimplanted SC catheter). Some divergence exists between these two modes of administration, since pumps provide better glycaemic control compared to injections in humans. The aim of this study was to compare the impacts of two modes of insulin administration (single injections of long-acting insulin or pump delivery of rapid-acting insulin) at the same dosage (4 IU/200 g/day) on rat metabolism and tissues. The rat weight and blood glucose levels were measured periodically after treatment. Immunostaining for signs of oxidative stress and for macrophages was performed on the liver and omental tissues. The continuous insulin delivery by pumps restored normoglycaemia, which induced the reduction of both reactive oxygen species and macrophage infiltration into the liver and omentum. Injections controlled the glucose levels for only a short period of time and therefore tissue stress and inflammation were elevated. In conclusion, the insulin administration mode has a crucial impact on rat metabolic parameters, which has to be taken into account when studies are designed.

Early effects of liver regeneration on endocrine pancreas: in vivo change in islet morphology and in vitro assessment of systemic effects on ß-cell function and viability in the rat model of two-thirds hepatectomy.

Liver and pancreas share key roles in glucose homeostasis. Liver regeneration is associated with systemic modifications and depends especially on pancreatic hormones. The aim of the study was to investigate the role of systemic factors released after two-thirds hepatectomy (2/3H) on early possible consequences of liver regeneration on endocrine pancreas structure and function. The pancreas and serum were harvested 1, 2, or 3 days after 2/3H or sham operation in Lewis rats. The HGF and VEGF serum concentrations and plasma microparticles levels were measured. The fate of endocrine pancreas was examined through islets histomorphometry and function in sham and 2/3H rats. ß-Cell line RIN-m5F viability was assessed after 24 h of growth in media supplemented with 10% serum from 2/3H or sham rats instead of FCS. Three days after surgery, the pancreas was heavier in 2/3H compared to sham rats (0.56 vs. 0.40% of body weight, p < 0.05) and the proportion of islets of intermediate size was lower in 2/3H rats (5 vs. 15%, p < 0.05). Compared to Sham, sera obtained 3 days after hepatectomy were more efficient to maintain the viability of RIN-m5F cells (99 vs. 67%, p < 0.01). Three days after surgery, no significant differences in serum HGF, a trend to significant increase in VEGF concentration and a significant increase in microparticles levels, were observed in 2/3H vs. sham rats (9.8 vs. 6.5 nM Phtd Ser Eq., p < 0.05). Liver regeneration is associated with early effects on islets and could influence ß-cell viability and function by systemic effect.

Improvement of rat islet viability during transplantation: validation of pharmacological approach to induce VEGF overexpression.

Delayed and insufficient revascularization during islet transplantation deprives islets of oxygen and nutrients, resulting in graft failure. Vascular endothelial growth factor (VEGF) could play a critical role in islet revascularization. We aimed to develop pharmacological strategies for VEGF overexpression in pancreatic islets using the iron chelator deferoxamine (DFO), thus avoiding obstacles or safety risks associated with gene therapy. Rat pancreatic islets were infected in vivo using an adenovirus (ADE) encoding human VEGF gene (4.10(8) pfu/pancreas) or were incubated in the presence of DFO (10 µmol/L). In vitro viability, functionality, and the secretion of VEGF were evaluated in islets 1 and 3 days after treatment. Infected islets or islets incubated with DFO were transplanted into the liver of syngenic diabetic rats and the graft efficiency was estimated in vivo by measuring body weight, glycemia, C-peptide secretion, and animal survival over a period of 2 months. DFO induced transient VEGF overexpression over 3 days, whereas infection with ADE resulted in prolonged VEGF overexpression lasting 14 days; however, this was toxic and decreased islet viability and functionality. The in vivo study showed a decrease in rat deaths after the transplantation of islets treated with DFO or ADE compared with the sham and control group. ADE treatment improved body weight and C-peptide levels. Gene therapy and DFO improved metabolic control in diabetic rats after transplantation, but this effect was limited in the presence of DFO. The pharmacological approach is an interesting strategy for improving graft efficiency during transplantation, but this approach needs to be improved with drugs that are more specific.