Nitric Oxide and gastric motility in female diabetics

女性糖尿病患者的一氧化氮和胃动力

基本信息

批准号：
7751113
负责人：
PANDU R GANGULA
金额：
$ 20.76万
依托单位：
MEHARRY MEDICAL COLLEGE
依托单位国家：
美国
项目类别：
财政年份：
2008
资助国家：
美国
起止时间：
2008-04-01 至 2010-12-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/7751113
关键词：
Abdominal Pain Accounting Affect American Anabolism Attenuated Biological Biopterin Body Weight decreased Chronic Clinic Clinical Complications of Diabetes Mellitus Data Diabetes Mellitus Dimerization Disease Dyspepsia Enzymes Event Experimental Models Female Functional disorder Gastric Emptying Gastric Tissue Gastrointestinal Motility Gastroparesis Guanosine Triphosphate Health Hyperglycemia Impairment In Vitro Insulin Lead Mechanics Mediating Messenger RNA Molecular Muscle Contraction Nausea and Vomiting Nervous system structure Neurons Neurotransmitters Nitric Oxide Nitric Oxide Synthase Type I Non-Insulin-Dependent Diabetes Mellitus Pathogenesis Pathway interactions Patients Production Progressive Disease Rattus Recurrence Regulation Relaxation Reporting Retina Role Sex Bias Sex Characteristics Solid Stomach Streptozocin Structure Supplementation Symptoms Syndrome Testing Tissues Type I Insulin Vomiting Woman Work base cell motility cofactor design diabetic diabetic gastroparesis diabetic rat dimer enzyme activity gastrointestinal in vivo inhibitor/antagonist kidney vascular structure motility disorder neuron loss new therapeutic target protein expression research study tetrahydrobiopterin

项目摘要

DESCRIPTION (provided by applicant): Gastroparesis is a disabilitating disease affecting predominantly young women. The biological basis of this disorder and its associated gender bias remains poorly understood. Recent studies have implicated a role for dysregulation of neuronal nitric oxide synthase (nNOS) in myenteric neurons and we surmised that gender differences in nitrergic control of gastric motility may possibly account for observed vulnerability of females to diabetic gastroparesis. Our preliminary data suggests that a significant impairment of nitrergic relaxation and delayed gastric emptying for solids was demonstrated selectively in females after diabetes induction with streptozotocin (STZ). Most importantly, we have also shown that changes in nitrergic relaxation in both healthy and diabetic rats correlates well with the state of dimerization of nNOS1 but not with the expression of total nNOS (1, 2 and 3). Dimerization of nNOS is essential for activity of this enzyme but has not been previously studied in gastrointestinal tissue. In this proposal, we have focused on the role of tetrahydrobiopterin (BH4), an essential cofactor for nNOS activity that is required to maintain the homodimeric structure of nNOS. BH4 levels in tissue in turn depend on the activity of GTP cyclohydrolase1 (GTPCH1), the rate limiting enzyme in the de novo synthesis of BH4. In preliminary experiments we have demonstrated that GTPCH1 mRNA and protein expression are down regulated in the diabetic female gastric tissues along with significantly reduced BH4 content, suggesting reduced synthesis of biopterins leading to decreased nitrergic relaxation. In support of this, the GTPCH1 inhibitor, 2, 4 diamino-6-hydroxypyrimidine (DAHP), reduced nNOS1 dimerization, NO release and nitrergic relaxation of gastric tissue in normal female rats in vitro. Conversely, the exogenous addition of BH4 to female gastric tissues in vitro reverses a hyperglycemia-induced decrease in nitrergic relaxation. In addition, in vivo BH4 treatment attenuated reduced nNOS activity in diabetic gastric tissue. We therefore hypothesize that impaired biosynthesis of gastric BH4 accounts for the decrease in nNOS activity and nitrergic relaxation in female diabetic gastroparesis. To test this hypothesis we propose the following specific aims: Specific Aim 1: To determine whether diabetes results in impairment of the BH4 biosynthetic pathway, nNOS dimerization, nNOS activity and nitrergic relaxation in female rat gastric tissues. Specific Aim 2: To investigate whether BH4 supplementation restores delayed gastric emptying, impaired gastric nNOS dimerization, nNOS activity, NO synthesis and nitrergic relaxation in female diabetic rats. The data from these studies will provide important information as to the mechanisms of regulation of nNOS function in normal and diabetic female rat gastric tissues and thereby enhance our understanding of the pathophysiology of gastroparesis. Further, it may lead to the discovery of novel therapeutic targets for the management of this challenging clinical syndrome.Diabetes mellitus is a chronic progressive disease that affects 16 million Americans. Diabetes causes several complications that affect retina, kidney, vascular, gastrointestinal, and nervous system. The mechanism through which diabetic complications develop is unclear. Gastric dysmotility or gastropathy is one of the vigorous complications of diabetic mellitus in clinics and can cause disabling symptoms including nausea, vomiting and weight loss and often leads to delayed or accelerated gastric emptying. Reports indicate that 80% of patients are women suffering with this problem. Although the exact pathogenesis remains unknown, there is fairly convincing evidence in experimental models that diabetes results in the malfunctioning of specific neurons that produce the neurotransmitter nitric oxide (NO). This condition is due to loss of expression of the enzyme responsible for NO production (neuronal nitric oxide synthase: nNOS) and can be reversed with insulin replacement. The molecular events leading to loss of nNOS expression and altered (delay or accelerate) gastric emptying (mechanical due to loss of neuronal control of stomach muscle contractions and relaxations) in diabetic stomachs remain unknown. The data from these studies will provide important information as to the mechanisms of regulation of NO mediated gastric emptying and stomach contractions in diabetic female rat. Further, it may lead to the discovery of novel therapeutic targets for the management of this challenging clinical syndrome.

描述（由申请人提供）：胃轻瘫是一种主要影响年轻女性的致残性疾病。这种疾病的生物学基础及其相关的性别偏见仍然知之甚少。最近的研究表明肌间神经元中神经元一氧化氮合酶（nNOS）失调的作用，我们推测胃运动的氮能控制的性别差异可能是观察到的女性易患糖尿病胃轻瘫的原因。我们的初步数据表明，在用链脲佐菌素（STZ）诱导糖尿病后，女性选择性地表现出氮能松弛和固体胃排空延迟的显着损害。最重要的是，我们还表明，健康和糖尿病大鼠的氮能舒张变化与 nNOS1 二聚化状态密切相关，但与总 nNOS 的表达无关（1、2 和 3）。 nNOS 的二聚化对该酶的活性至关重要，但之前尚未在胃肠道组织中进行过研究。在本提案中，我们重点关注四氢生物蝶呤 (BH4) 的作用，它是 nNOS 活性的重要辅助因子，是维持 nNOS 同二聚体结构所必需的。组织中的 BH4 水平又取决于 GTP 环化水解酶 1 (GTPCH1) 的活性，GTPCH1 是 BH4 从头合成的限速酶。在初步实验中，我们已经证明，糖尿病女性胃组织中 GTPCH1 mRNA 和蛋白表达下调，同时 BH4 含量显着降低，表明生物蝶呤合成减少，导致氮能舒张减少。为了支持这一点，GTPCH1 抑制剂 2, 4 二氨基-6-羟基嘧啶 (DAHP) 在体外可减少正常雌性大鼠胃组织的 nNOS1 二聚化、NO 释放和胃组织的氮能松弛。相反，在体外向女性胃组织中外源添加 BH4 可逆转高血糖引起的氮能舒张下降。此外，体内 BH4 治疗可减弱糖尿病胃组织中 nNOS 活性的降低。因此，我们推测胃 BH4 生物合成受损是女性糖尿病性胃轻瘫中 nNOS 活性和氮能舒张下降的原因。为了检验这一假设，我们提出以下具体目标：具体目标 1：确定糖尿病是否会导致雌性大鼠胃组织中 BH4 生物合成途径、nNOS 二聚化、nNOS 活性和氮能舒张受损。具体目标 2：研究补充 BH4 是否可以恢复雌性糖尿病大鼠的胃排空延迟、胃 nNOS 二聚化受损、nNOS 活性、NO 合成和氮能舒张。这些研究的数据将提供有关正常和糖尿病雌性大鼠胃组织中 nNOS 功能调节机制的重要信息，从而增强我们对胃轻瘫病理生理学的理解。此外，它可能会导致发现新的治疗靶点来管理这种具有挑战性的临床综合征。糖尿病是一种慢性进行性疾病，影响着 1600 万美国人。糖尿病会引起多种并发症，影响视网膜、肾脏、血管、胃肠道和神经系统。糖尿病并发症发生的机制尚不清楚。胃动力障碍或胃病是临床上糖尿病的严重并发症之一，可引起恶心、呕吐和体重减轻等致残症状，并常常导致胃排空延迟或加速。报告显示，80%的患者是患有此问题的女性。尽管确切的发病机制仍不清楚，但实验模型中有相当令人信服的证据表明，糖尿病会导致产生神经递质一氧化氮（NO）的特定神经元功能障碍。这种情况是由于负责 NO 生成的酶（神经元一氧化氮合酶：nNOS）表达缺失所致，可以通过补充胰岛素来逆转。导致糖尿病胃中 nNOS 表达丧失和胃排空改变（延迟或加速）（由于胃肌肉收缩和松弛的神经元控制丧失而导致的机械性）的分子事件仍然未知。这些研究的数据将为糖尿病雌性大鼠中 NO 介导的胃排空和胃收缩的调节机制提供重要信息。此外，它可能会导致发现新的治疗靶点来管理这种具有挑战性的临床综合征。