NITRIC OXIDE AND ASYMMETRIC DIMETHYLARGININE PRODUCTION IN PATIENTS WITH EARL

EarL 患者中一氧化氮和不对称二甲基精氨酸的产生

• 批准号: 7950693
• 负责人: FAROOK JAHOOR
• 金额: $ 0.12万
• 依托单位: BAYLOR COLLEGE OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-12-01 至 2009-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7950693
• 关键词: APACHE II; Adult; Antihypertensive Agents; Arginine; Bilirubin; Biochemical; Biochemical Markers; Catabolism; Child; Childhood; Citrulline; Clinical Research; Computer Retrieval of Information on Scientific Projects Database; Creatinine; Critical Illness; Data; Enzymes; Equilibrium; Excretory function; Failure; Funding; Grant; Hepatic; High Cardiac Output; Human; Hydrolysis; Hypotension; In Vitro; Infection; Inflammation; Institution; Intensive Care Units; Kidney; Kinetics; Lactic acid; Lead; Leucine; Liver Failure; Low Cardiac Output; Measurement; Metabolic; Metabolism; Methods; Methylation; N,N-dimethylarginine; Nitrates; Nitric Oxide; Nitric Oxide Pathway; Nitric Oxide Synthase; Nitrites; Nutritional Support; Organ failure; Outcome; Patients; Physiological; Plasma; Play; Production; Property; Protein Biosynthesis; Protein Isoforms; Proteins; Proteolysis; Research; Research Personnel; Resources; Risk Factors; Role; Sepsis; Septic Shock; Source; Survivors; Testing; Time; Tissues; Tracer; United States National Institutes of Health; Vasoconstrictor Agents; Vasodilation; dimethylarginine; immune function; in vivo; indexing; inhibitor/antagonist; mortality; neurotransmission; oxidation; protein degradation; response; septic; stable isotope; urinary; volunteer

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Nitric oxide (NO) has many physiologic roles, including vasodilatation, immune function, neurotransmission, and inflammation. It is produced by the enzyme nitric oxide synthase (NOS), which converts arginine to citrulline and nitric oxide. However, the roles of arginine and NO in sepsis are not clearly understood, because there is limited in vivo data for septic humans. NO synthesis rates in septic children were significantly higher than in historic adult controls. However, as compared to healthy controls, hypotensive patients with sepsis had higher plasma NO metabolite concentration (NOx), a slower fractional synthesis rate of NOx, and a similar absolute synthesis rate of NOx. These different findings suggest that nitric oxide synthesis may be different in sepsis without hypotension compared to septic shock, and these differences may be related to these patients' underlying metabolic rate. Asymmetric dimethylarginine (ADMA) also plays a role in the arginine-nitric oxide pathway. ADMA inhibits nitric oxide synthase and acts as a competitive inhibitor of arginine for transport across the y+ transporter. ADMA has been shown to be a risk factor for intensive care unit (ICU) mortality, duration of ICU stay, duration of inotropic and vasopressor treatment, mean APACHE II score, and duration of ventilatory support. We will use stable isotope tracer and biochemical methods to study and compare three groups of subjects: normal controls, septic patients without hypotension, and patients with septic shock. Specific aim #1 is to determine the differences in leucine kinetics in these patients. The hypothesis tested is that septic patients without hypotension have faster rates of whole body protein kinetics when compared to septic patients with hypotension. Specific aim #2 is to determine the differences in arginine kinetics and the rate of arginine conversion to NO in these patients. The hypothesis tested is that septic patients with hypotension will have a slower rate of production of arginine and therefore a decreased rate of its conversion to NO as compared to septic patients without hypotension. Specific aim #3 is to determine the plasma and urinary concentrations of ADMA in these patients. The hypothesis tested is that NO synthesis rate will be negatively related to plasma ADMA concentrations. Hypothesis #1: Septic patients without hypotension have faster rates of whole body protein kinetics. Increased protein breakdown results in a faster rate of production of arginine, hence its increased rate of conversion to NO Hypothesis #2: Septic patients with hypotension have slower rates of whole body protein kinetics. Slower protein breakdown results in a slower rate of production of arginine, hence its decreased rate of conversion to NO Hypothesis #3: Plasma concentrations of ADMA are elevated in septic patients because of the faster rate of protein breakdown plus decreased renal excretion and hepatic metabolism. As a consequence, NO synthesis rate will be negatively related to plasma ADMA concentrations SPECIFIC AIMS Stable isotope tracer and biochemical methods will be used to study 3 groups of subjects: normal controls, septic patients without hypotension, and patients with septic shock. The following measurements will be made: Specific Aim #1: Endogenous leucine flux, an index of whole body protein breakdown; leucine oxidation, an index of net protein catabolism; and non-oxidative leucine disposal, an index of protein synthesis Specific Aim #2: Arginine flux, plasma concentration, and its rate of conversion to NO in the whole body Specific Aim #3: Plasma concentration and urinary excretion of ADMA Sepsis is defined as a systemic response to infection. Both arginine and nitric oxide appear to play a role in sepsis. However, the exact metabolism of arginine during sepsis remains unknown. Lower arginine levels have been found in patients who die of sepsis as compared to survivors of sepsis.1 Arginine is converted to NO and citrulline by nitric oxide synthase (NOS). Despite the in vitro evidence that NOS is induced by sepsis, there is limited in vivo data for septic humans. Several studies showed elevated levels of nitrite and nitrate, products of NO metabolism, in septic patients.2-4 In a study of 10 septic pediatric patients, Argaman et al demonstrated that NO synthesis rates in septic children were significantly higher than in historic adult controls. In addition, they found that plasma arginine flux in these septic children were similar to those observed in healthy adults, but that due to a higher rate of arginine oxidation as compared to synthesis, the septic patients were in a negative arginine balance.5 However, in another study of six adult patients in septic shock as compared to healthy controls, the septic patients had higher plasma NO metabolite concentration (NOx), a slower fractional synthesis rate of NOx, slower arginine flux, and lower plasma arginine concentration.6 In addition, significant positive and negative correlations between plasma NOx and creatinine concentrations and with GFR suggested that the higher plasma NOx levels were due to impaired excretion, rather than increased synthesis. Other studies have shown correlation between NOx and plasma creatinine.3, 7 These different findings suggest that nitric oxide synthesis may be different in sepsis without hypotension compared to septic shock. Two different responses are seen in sepsis: a low flow and a high flow response. The low flow state is characterized by low cardiac output and low metabolic rate, while the high flow state is characterized by high cardiac output and high metabolic rate.8 The low flow state occurs later, as a result of failure to resolve infection or tissue damage. When compared to normal volunteers, septic patients have a significantly increased rate of protein turnover.9 An increased rate of protein catabolism is the result of a marked increase in whole body protein breakdown with a more modest increase in whole body synthesis. This increased whole-body protein catabolism persists despite nutritional support. The increased availability of arginine from increased protein breakdown during early sepsis may increase the rate of nitric oxide synthesis. However, the presence of hypotension will lead to decreased rate of metabolic processes, including protein breakdown and hence, arginine production. Depletion of arginine availability over time will therefore lead to decreased NO synthesis. Asymmetric dimethylarginine (ADMA) also plays a role in the arginine-nitric oxide pathway. Dimethylarginines are synthesized by the methylation of arginine residues in proteins and subsequent release when these proteins are hydrolyzed. ADMA inhibits all isoforms of nitric oxide synthase. It also acts as a competitive inhibitor of arginine for transport across the y+ transporter. The major mechanism for elimination of ADMA from the body is degradation by the enzyme arginine dimethylaminohydrolase (DDAH). ADMA appears to play an important role in critically ill patients. ADMA has been shown to be a risk factor for ICU mortality10 as well as duration of ICU stay, duration of inotropic and vasopressor treatment, mean APACHE II score, and duration of ventilatory support.11 In addition, hepatic failure as well as lactic acid and bilirubin, biochemical markers of hepatic function, were independent determinants of plasma ADMA concentration. Nijveldt et al hypothesized that because of the association between ADMA levels and outcome, ADMA plays a causative role in multisystem organ failure by interfering with nitric oxide (NO) production and the physiologic properties of NO.12 They also hypothesize that ADMA accumulates by increased proteolysis as well as decreased elimination during renal and hepatic failure.13

该副本是利用众多研究子项目之一 由NIH/NCRR资助的中心赠款提供的资源。子弹和 调查员（PI）可能已经从其他NIH来源获得了主要资金， 因此可以在其他清晰的条目中代表。列出的机构是 对于中心，这不一定是调查员的机构。 一氧化氮（NO）具有许多生理作用，包括血管舒张，免疫功能，神经传递和炎症。 它是由一氧化氮合酶（NOS）产生的，该酶将精氨酸转化为瓜氨酸和一氧化氮。 但是，由于体内数据的败血性数据有限，因此在败血症中的精氨酸和无败血症的作用尚不清楚。 化粪池儿童的合成率显着高于历史悠久的成人对照。 但是，与健康对照相比，败血症的低血压患者具有较高的血浆NO代谢物浓度（NOX），NOX的分数合成速率较慢，NOX的绝对合成速率相似。 这些不同的发现表明，与败血性休克相比，败血症一氧化氮的合成可能有所不同，并且这些差异可能与这些患者的潜在代谢率有关。 非对称二甲基精氨酸（ADMA）也在精氨酸氮氧化物途径中起作用。 ADMA抑制一氧化氮合酶，并充当精氨酸的竞争抑制剂，用于跨Y+转运蛋白。 ADMA已被证明是重症监护病房（ICU）死亡率，ICU停留时间，肌力和加速器治疗持续时间，平均APACHE II评分以及通气支持持续时间的危险因素。 我们将使用稳定的同位素示踪剂和生化方法来研究和比较三组受试者：正常对照，没有低血压的化粪池患者以及感染性休克的患者。 具体目的＃1是确定这些患者亮氨酸动力学的差异。 所检验的假设是，与败血症患者相比，没有低血压的化粪池患者的全身蛋白动力学速率更快。 具体目的2是确定这些患者的精氨酸动力学差异以及精氨酸转化率的差异。 测试的假设是，与没有低血压的化粪池患者相比，患有低血压的败血症患者的产生速度较慢，因此其转化率降低了NO。 具体目的＃3是确定这些患者ADMA的血浆和尿液浓度。 测试的假设是，没有合成速率将与血浆ADMA浓度负相关。 假设1：没有低血压的化粪池患者的全身蛋白动力学速率更快。 蛋白质分解的增加导致精氨酸的生产速度更快，因此转化率提高到NO 假设2：败血症患者的全身蛋白动力学率较慢。 较慢的蛋白质分解会导致精氨酸的生产速度较慢，因此转化率降低到NO 假设3：化脓性患者的血浆浓度升高，因为蛋白质分解的速度加快了肾脏排泄和肝代谢的降低。结果，没有合成率将与血浆ADMA浓度负相关 具体目标 稳定的同位素示踪剂和生化方法将用于研究3组受试者：正常对照，没有低血压的化脓性患者以及败血性休克的患者。 将进行以下测量： 特定目的＃1：内源性亮氨酸通量，全身蛋白质分解的指数；亮氨酸氧化，净蛋白质分解代谢的指数；和非氧化亮氨酸处置，蛋白质合成指数 特定目标＃2：精氨酸通量，等离子体浓度及其转换率在全身 特定目的＃3：血浆浓度和ADMA的尿液排泄 败血症被定义为对感染的全身反应。 精氨酸和一氧化氮似乎在败血症中起作用。 但是，败血症期间精氨酸的确切代谢仍然未知。 与败血症的幸存者相比，死于败血症的患者的精氨酸水平较低。1精氨酸通过一氧化氮合酶（NOS）转化为NO和瓜氨酸。 尽管体外证据表明败血症诱导了NOS，但化粪池的体内数据有限。 几项研究表明，在化粪池患者中，亚硝酸盐和硝酸盐水平升高，无代谢产物。2-4在对10名败血症患者的研究中，Argaman等人证明，败血症儿童的合成率没有明显高于历史悠久的成人对照组。 In addition, they found that plasma arginine flux in these septic children were similar to those observed in healthy adults, but that due to a higher rate of arginine oxidation as compared to synthesis, the septic patients were in a negative arginine balance.5 However, in another study of six adult patients in septic shock as compared to healthy controls, the septic patients had higher plasma NO metabolite concentration (NOx), a slower fractional synthesis rate of 6此外，血浆NOX和肌酐浓度之间的显着正相关和负相关性，与GFR之间的显着正相关，并且与GFR有关，较高的血浆NOX水平是由于排泄受损而而不是增加的合成。 其他研究表明，NOX和血浆肌酐之间的相关性。3，7 这些不同的发现表明，与败血性休克相比，败血症中一氧化氮的合成可能有所不同。 败血症中看到了两种不同的反应：低流量和高流动响应。 低流量状态的特征是心输出量低和代谢率低，而高流量状态的特征是高心输出量和高代谢率。8低流量状态由于未能解决感染或组织损伤而导致低流量状态。 与正常的志愿者相比，化粪池患者的蛋白质周转率显着增加。9蛋白质分解代谢率的提高是全身蛋白质分解明显增加，全身合成的增加。 尽管营养支持，但这种增加的全身蛋白质分解代谢仍然存在。 败血症期间蛋白质分解增加的精氨酸的可用性增加可能会增加一氧化氮合成的速率。 但是，低血压的存在将导致代谢过程的速率降低，包括蛋白质分解以及精氨酸产生。 因此，随着时间的推移，精氨酸的可用性耗竭将导致无合成降低。 非对称二甲基精氨酸（ADMA）也在精氨酸氮氧化物途径中起作用。 通过蛋白质中精氨酸残基的甲基化并在这些蛋白质水解时释放，通过精氨酸残基的甲基化来合成二甲基丁金。 ADMA抑制一氧化氮合酶的所有同工型。 它也充当精氨酸的竞争抑制剂，用于跨Y+转运蛋白的运输。 从体内消除ADMA的主要机制是酶精氨酸二甲基氨基氢化酶（DDAH）降解。 ADMA似乎在重病患者中起着重要作用。 ADMA has been shown to be a risk factor for ICU mortality10 as well as duration of ICU stay, duration of inotropic and vasopressor treatment, mean APACHE II score, and duration of ventilatory support.11 In addition, hepatic failure as well as lactic acid and bilirubin, biochemical markers of hepatic function, were independent determinants of plasma ADMA concentration. Nijveldt等人假设，由于ADMA水平与结果之间的关联，ADMA通过干扰一氧化氮（NO）生产（NO）生产（NO）和第12号生理特性，在多系统器官的失败中起致病作用