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为什么1型糖尿病患者天然胰岛和肝内移植胰岛对低血糖的胰高血糖素反应缺失，并确定大网膜或腹腔内移植部位是否比肝内移植部位更能提供最佳的α和β细胞功能支持。明确目标#1。评估另一种假设，即在低血糖期间，关闭锌ci2输注引起的胰高血糖素水平升高是由于循环中胰高血糖素清除率的降低而不是胰高血糖素分泌的增加。确定关闭氯化锌输注对α细胞反应的恢复作用是否通过经典胰岛素受体途径介导。我们假设胰岛素而非锌在低血糖时对α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。通过饥饿和糖异生阻滞剂治疗来确定肝糖原的消耗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，它使移植胰岛对全身性低血糖视而不见。具体目标#3。确定肝内、腹腔内或网膜囊移植部位是否对β和α细胞功能最有利。我们假设非肝部位对免疫抑制药物引起的β细胞毒性更有保护作用，并且对正常的α细胞对低血糖的反应更有支持作用。这些实验将在糖尿病易发大鼠（DP-BB）和近交系Lewis大鼠中进行。这些方法包括建立胰十二指肠动脉胰岛素输注，当糖尿病动物低血糖时可以关闭；延长禁食和输注AICAR以消耗肝糖原；并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，以及钙调磷酸酶抑制剂对β细胞毒性的保护作用。在这些研究的结论中，我们将确定DP-BB大鼠的α细胞缺陷是代谢性的还是自身免疫性的；肝内葡萄糖通量是否导致肝内胰岛胰高血糖素分泌缺陷；非肝部位是否比肝部位在α和β细胞功能以及对钙调磷酸酶抑制剂不良反应的保护方面更有效。

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.