Pancreas and Islet Transplantation in Humans

描述（由申请人提供）：本提案的总体目标是了解1型糖尿病患者的天然胰岛和肝内移植胰岛中胰高血糖素对低血糖反应缺失的原因，并确定网膜或腹膜内移植部位是否比肝内部位提供更佳的α和β细胞功能支持。具体目标#1。验证另一种假设，即低血糖期间响应于去除ZnCl 2输注的胰高血糖素水平升高是由于胰高血糖素从血液中清除减少而不是我们所建议的胰高血糖素分泌增加所致。确定清除氯化锌输注引起的α细胞反应恢复作用的机制是否由经典胰岛素受体途径介导。我们推测，在低血糖期间，胰岛素（而非锌）对α细胞功能的调节作用是由经典的胰岛素受体途径介导的。规范JC目标#2。确定通过饥饿消耗肝糖原和用新生血管生成阻断剂治疗是否会恢复肝内胰岛胰高血糖素对低血糖的反应。我们假设肝内移植胰岛的胰高血糖素反应缺陷的作用机制是肝内葡萄糖通量，它使移植的胰岛对系统性低血糖视而不见。具体目标#3确定肝内、腹膜内或网膜囊移植部位对β和α细胞功能是否最佳。我们假设非肝脏部位对免疫抑制药物引起的β细胞毒性更具保护作用，并且更支持正常的α细胞对低血糖的反应。这些实验将使用糖尿病易感BB（DP-BB）大鼠和近交系刘易斯大鼠进行。所述方法包括建立胰十二指肠内动脉胰岛素输注，当糖尿病动物变得低血糖时可以关闭所述胰岛素输注;延长禁食和AICAR输注以消耗肝糖原;以及将供体胰岛移植到肝脏、网膜和腹膜部位以检查对α和β细胞功能的后果以及针对钙调磷酸酶抑制剂的β细胞毒性作用的保护。在这些研究结束时，我们将确定DP-BB大鼠中的α细胞缺陷本质上是代谢性的还是自身免疫性的;肝内葡萄糖流量是否是肝内胰岛分泌胰高血糖素缺陷的原因;以及就α和β细胞功能以及针对钙蛋白抑制剂的不良作用的保护而言，非肝部位对于胰岛移植是否比肝部位更有效。

DESCRIPTION (provided by applicant): The overall objectives of this proposal are to understand why glucagon responses to hypoglycemia from native pancreatic islets in type 1 diabetes and from islets transplanted intrahepatically are absent and to establish whether the omental or intraperitoneal transplant sites provide more optimal support of alpha and beta cell function than the intrahepatic site. Specific Aim #1. TO EVALUATE THE ALTERNATE HYPOTHESIS THAT THE RISE IN GLUCAGON LEVELS DURING HYPOGLYCEMIA IN RESPONSE TO SWITCHING OFF ZnCI2 INFUSIONS IS CAUSED BY DECREASED CLEARANCE OF GLUCAGON FROM THE CIRCULATION RATHER THAN INCREASED GLUCAGON SECRETION AS WE HAVE SUGGESTED. TO DETERMINE WHETHER THE MECHANISM OF THE RESTORATIVE EFFECT ON ALPHA CELL RESPONSES CAUSED BY SWITCHING OFF ZINC CHLORIDE INFUSIONS IS MEDIATED BY CLASSICAL INSULIN RECEPTOR PATHWAYS. WE HYPOTHESIZE THAT REGULATORY EFFECTS OF INSULIN, BUT NOT ZINC, ON ALPHA CELL FUNCTION DURING HYPOGLYCEMIA ARE MEDIATED BY CLASSICAL INSULIN RECEPTOR PATHWAYS. SpecfJC Aim #2. To determine whether depletion of liver glycogen by starvation and treatment with a blocker of gluconeogenesis will restore intrahepatic islet glucagon responses to hypoglycemia. We hypothesize that the mechanism of action for defective glucagon responses of islets transplanted intrahepatically is intrahepatic glucose flux, which blinds the transplanted islet to systemic hypoglycemia. Specific Aim #3. To determine whether the intrahepatic, intraperitoneal, or the omental sac transplantation sites is most optimal for beta and alpha cell function. We hypothesize that the non-hepatic sites will be more protective against beta cell toxicity caused by immunosuppressive drugs and will be more supportive of normal alpha cell responses to hypoglycemia. These experiments will be carried out using diabetes-prone BB (DP-BB) rats and inbred Lewis rats. The methods involve establishment of an intra-pancreaticoduodenal arterial insulin infusion that can be switched off when diabetic animals become hypoglycemic; prolonged fasting and AICAR infusion to deplete hepatic glycogen; and transplantation of donor islets into the hepatic, omental, and peritoneal sites to examine consequences on alpha and beta cell function as well as protection against the beta cell toxic effects of a calcineurin inhibitor. At the conclusion of these studies we will have established whether the alpha cell defect in DP-BB rats is metabolic or autoimmune in nature; whether intrahepatic glucose flux is responsible for defective glucagon secretion from intrahepatic islets; and whether non-hepatic sites are more efficacious than the hepatic site for islet transplantation in terms of alpha and beta cell function as well as protection against adverse effects of calcineruin inhibitors.