Pancreas and Islet Transplantation in Humans

描述(由申请人提供)：这项建议的总体目标是了解为什么1型糖尿病患者的天然胰岛和肝内移植的胰岛对低血糖没有高血糖反应，并确定大网膜或腹膜内移植部位是否比肝脏内移植部位对α和β细胞功能提供更理想的支持。具体目的#1.评估另一种假说，即停输氯化锌引起低血糖时高血糖素水平升高是由于循环中高血糖素清除减少而不是我们所建议的高血糖素分泌增加所致。目的：探讨停输氯化锌对阿尔法细胞反应恢复作用的机制是否通过经典的胰岛素受体途径来实现。我们假设，在低血糖期间，胰岛素而不是锌对阿尔法细胞功能的调节作用是通过经典的胰岛素受体途径介导的。SPECFJC目标2：确定饥饿耗尽肝糖原并用糖异生阻滞剂治疗是否能恢复肝内胰岛高血糖素对低血糖的反应。我们推测，肝内移植胰岛的胰升糖素反应缺陷的作用机制是肝内葡萄糖流量，使移植的胰岛对全身性低血糖视而不见。明确目标#3.确定肝内、腹膜内或大网囊移植部位对于β细胞和α细胞功能而言是最理想的。我们假设，非肝脏部位对免疫抑制药物引起的β细胞毒性有更好的保护作用，并且更有利于正常的阿尔法细胞对低血糖的反应。这些实验将使用易患糖尿病的BB(DP-BB)大鼠和近交系Lewis大鼠进行。这些方法包括建立胰腺十二指肠动脉胰岛素输注，当糖尿病动物出现低血糖时可以关闭胰岛素输注；延长禁食和AICAR输注以耗尽肝糖原；将供体胰岛移植到肝脏、大网膜和腹膜部位，以检查对α和β细胞功能的影响，以及防止钙调神经磷酸酶抑制剂的β细胞毒性影响。在这些研究的结论中，我们将确定DP-BB大鼠的阿尔法细胞缺陷本质上是代谢还是自身免疫；肝内葡萄糖流量是否与肝内胰岛分泌缺陷有关；以及在胰岛移植的α细胞和β细胞功能以及对抗钙蛋白抑制剂的不良影响方面，非肝脏部位是否比肝脏部位更有效。

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.