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

描述（由申请人提供）： 胰岛β细胞衰竭是2型糖尿病发展的核心，并由高血糖症和高脂血症引起。蛋白质脑啡肽酶，已被证明在非胰岛组织中被上调与慢性升高的葡萄糖和2型糖尿病中看到的脂肪水平。虽然还没有研究脑啡肽酶在胰岛中的功能，但我们的初步数据显示，它在胰岛中合成并具有活性，并且可能在响应胰岛应激因子的β细胞功能调节中发挥作用。因此，该提案的总体目标是阐明脑啡肽酶在与β细胞功能受损相关的条件下的作用，即增加的脂肪和葡萄糖。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。将进行以下研究以调查： 1.脑啡肽酶在慢性高脂血症引起的胰岛素分泌障碍中的作用。首先，将脑啡肽酶缺陷（NEP-KO）小鼠饲喂高脂肪饮食12周，并在体内测量胰岛素分泌。我们的初步数据表明，NEP-KO小鼠受到保护，不受高脂饮食诱导的葡萄糖刺激的胰岛素分泌减少的影响。其次，将NEP-KO小鼠的胰岛与游离脂肪酸一起培养，并在体外检查胰岛素分泌。 2.脑啡肽酶在慢性血糖升高引起的胰岛素分泌障碍中的作用。我们的初步数据表明，neprilysin可能在高糖条件下上调，从而可能介导氧化应激的诱导。首先，NEP-KO小鼠将接受48小时葡萄糖输注以诱导高血糖症，然后将在体内测量胰岛素分泌。其次，将来自NEP-KO小鼠的胰岛在高葡萄糖中培养，并在体外检查胰岛素分泌。 3.在慢性高脂高糖条件下，肾素-血管紧张素系统（RAS）在介导脑啡肽酶作用中的作用。由于脑啡肽酶是RAS的组分，因此分离的胰岛将用于确定脑啡肽酶在该途径中的活性是否是β细胞功能受损的原因。β细胞中的脑啡肽酶抑制可能对2型糖尿病有有益的结果，因此我们的发现将对开发减少/预防β细胞功能障碍的治疗方法具有重要意义。

DESCRIPTION (provided by applicant): 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, 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, our preliminary data show that 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. The following studies will be performed to investigate: 1. The role of neprilysin in the impairment of insulin secretion induced by chronically elevated fat. Firstly, neprilysin deficient (NEP-KO) mice will be fed a high fat diet for 12 weeks and insulin secretion will be measured in vivo. Our preliminary data indicate that NEP-KO mice are protected from high fat diet-induced reductions in glucose-stimulated insulin secretion. Secondly, islets from NEP-KO mice will be cultured with free fatty acids and insulin secretion will be examined in vitro. 2. The role of neprilysin in the impairment of insulin secretion induced by chronically elevated glucose. Our preliminary data suggest that neprilysin may 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 will be measured in vivo. Secondly, islets from NEP-KO mice will be cultured in high glucose and insulin secretion will be examined in vitro. 3. The role of the renin-angiotensin system (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. Neprilysin inhibition in the beta-cells may have beneficial outcomes in type 2 diabetes and so our findings will have significant implications for the development of therapeutics to reduce/prevent beta-cell dysfunction.