The role of neprilysin in pancreatic beta-cell dysfunction and death

胰岛β细胞衰竭是2型糖尿病发展的核心， 高血糖和高脂血症。脑啡肽酶是肾素-血管紧张素系统的一种成分 (RAS)在非胰岛组织中，已显示随着葡萄糖和脂肪的慢性升高而上调。 2型糖尿病的发病机制虽然脑啡肽酶在胰岛中的功能还没有研究，但我们已经研究了脑啡肽酶在胰岛中的作用。 数据显示它在胰岛中合成并具有活性，并可能在β细胞功能的调节中发挥作用 对胰岛应激源的反应。因此，该提议的总体目标是阐明脑啡肽酶在脑啡肽释放中的作用。 与β细胞功能受损相关的病症，即脂肪和葡萄糖增加。我们假设 在脂肪和葡萄糖长期升高的状态下，脑啡肽酶活性上调，从而促进 β细胞功能障碍 在该奖项的K99阶段，进行了研究，以确定脑啡肽酶的贡献， 由长期脂肪升高引起的胰岛素分泌受损。我们的研究结果表明，脑啡肽酶是 事实上，在慢性脂肪升高的条件下上调，这与降低的葡萄糖估计有关。 体外胰岛素分泌。此外，高脂饮食喂养的脑啡肽酶缺陷（NEP-KO）小鼠， 在体内免受高脂肪饮食诱导的葡萄糖刺激的胰岛素分泌减少。 在本合同的ROO阶段，将进行以下研究以确定： 1)脑啡肽酶在慢性高血糖引起的胰岛素分泌障碍中的作用。我们 初步数据表明脑啡肽酶在高葡萄糖条件下也可能上调 可能介导氧化应激的诱导。首先，NEP-KO小鼠将接受48小时葡萄糖输注 诱发高血糖，那么胰岛素分泌就会增加。在体内测量。第二，从NEPKO分离的胰岛 将小鼠在高葡萄糖中培养，并在体外检查胰岛素分泌。 2)慢性脂肪和葡萄糖升高时RAS在介导脑啡肽酶作用中的作用 条件由于脑啡肽酶是RAS的一种成分，因此将使用分离的胰岛来确定是否 脑啡肽酶在该途径中的活性是β-细胞功能受损的原因。

Islet beta-cell failure is central to the development of type 2 diabetes and is contributed to by both hyperglycemia and hyperlipidemia. The protein neprilysin, a component ofthe renin-angiotensin system (RAS), has been shown in non-islet tissues to be upregulated with the chronically elevated glucose and fat levels seen in type 2 diabetes. While the function of neprilysin in islets has not been investigated, we have data that show it is synthesized and active in islets and may play a role in the modulation of beta-cell function in response to islet stressors. Thus, the overall aim of this proposal is to elucidate the role of neprilysin under conditions associated with impaired beta-cell function, namely increased fat and glucose. We hypothesize that in states of chronically elevated fat and glucose, neprilysin activity is upregulated thereby promoting beta-cell dysfunction. During the K99 phase of this award, studies were conducted to determine the contribution of neprilysin to impaired insulin secretion induced by chronically elevated fat. Our findings demonstrate that neprilysin is indeed upregulated under conditions of chronically elevated fat and this is associated with reduced glucosestimulated insulin secretion in vitro. Moreover, neprilysin deficient (NEP-KO) mice fed a high fat diet are protected from high fat diet-induced reductions in glucose-stimulated insulin secretion in vivo. During the ROO phase of this award, the following studies will be performed to determine: 1) The role of neprilysin in the impairment Of insulin secretion induced by chronically elevated glucose. Our preliminary data suggest that neprilysin may also be upregulated under high glucose conditions and thereby may mediate the induction of oxidative stress. Firstly, NEP-KO mice will receive a 48-hour glucose infusion to induce hyperglycemia, then insulin secretion wil! be measured in vivo. Secondly, isolated islets from NEPKO mice will be cultured in high glucose and insulin secretion will be examined in vitro. 2) The role ofthe RAS in mediating neprilysin's effects under chronically elevated fat and glucose conditions. Since neprilysin is a component of the RAS, isolated islets will be used to determine whether neprilysin's activity in this pathway is responsible for impaired beta-cell function.