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 mumol/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

Deletion of protein kinase D1 in pancreatic β-cells impairs insulin secretion in high-fat diet-fed mice

Bβ-cell adaptation to insulin resistance is necessary to maintain glucose homeostasis in obesity. Failure of this mechanism is a hallmark of type 2 diabetes (T2D). Hence, factors controlling functional β-cell compensation are potentially important targets for the treatment of T2D. Protein kinase D1 (PKD1) integrates diverse signals in the β-cell and plays a critical role in the control of insulin secretion. However, the role of β-cell PKD1 in glucose homeostasis in vivo is essentially unknown. Using β-cell specific, inducible PKD1 knock-out mice (βPKD1KO), we examined the role of beta-cell PKD1 under basal conditions and during high-fat feeding. βPKD1KO mice under chow diet presented no significant difference in glucose tolerance or insulin secretion compared to mice expressing the Cre transgene alone; however, when compared to wild-type mice, both groups developed glucose intolerance. Under high-fat diet, deletion of PKD1 in β-cells worsened hyperglycemia, hyperinsulinemia and glucose intolerance. This was accompanied by impaired glucose-induced insulin secretion both in vivo in hyperglycemic clamps and ex vivo in isolated islets from high-fat fed βPKD1KO mice, without changes in islet mass. This study demonstrates an essential role for PKD1 in the β-cell adaptive secretory response to high-fat feeding in mice

Pro-inflammatory and pro-oxidant status of pancreatic islet in vitro is controlled by TLR-4 and HO-1 pathways

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Instant blood-mediated inflammatory reaction during islet transplantation: the role of Toll-like receptors signaling pathways:

The instant blood-mediated inflammatory reaction (IBMIR) leads to massive destruction of transplanted islets. Islet isolation and time of culture may elicit the release of potent activators of Toll-like receptors (TLRs) signaling pathways during IBMIR. This work sought to evaluate the role of TLR signaling pathways to mediate inflammatory reactions. Isolated rat pancreatic islets were cultured for 12, 24, or 48 hours. Their viability was assessed by fluorescein diacetate/propidium iodide and their functionality, by glucose stimulation tests. Endotoxin levels were quantified using the Limulus Amebocyte Lysate assays. After RNA extraction and reverse transcription, we performed polymerase chain reaction (PCR) arrays. Samples obtained immediately after isolation were defined as controls. Eighty-four genes belonging to the TLR signaling pathways, were compared with control samples. After culture, islets were viable and functional with low endotoxin levels (< 0.1 endotoxin units/mL) showed TLR activation not due to exogenous contamination. Analysis of PCR arrays highlighted significant up-regulation of TLR-2. After 24 hours of culture, TLR-2 was up-regulated to 6.8 +/- 0.6-fold (P < .001) compared with controls but decreased to 4.3 +/- 1.4-fold after 48 hours. In the same way, expression of myeloid differentiation primary response gene 88 (Myd88) was significantly up-regulated (3.2 +/- 0.4-fold [P < .001]) compared with controls. After 12 hours of culture, interleukin-10 gene expression was significantly up-regulated at 11.6 +/- 3.7- fold (P < .05), reaching 17.5 +/- 8.3 after 24 hours. Finally, the cyclo-oxygenase-2 gene expression was up-regulated to 509 +/- 67.1-fold (P < .05) after 12 hours of culture. These data confirmed the implication of TLR signaling pathways in early inflammatory events