Effect of cysteine on glutathione production in critically ill neonates

应聘者描述(由申请人提供)：应聘者是加州大学洛杉矶分校大卫·格芬医学院的儿科外科医生和外科助理教授，他的长期目标是成为一名独立的临床医生兼科学家，其研究将对减少新生儿遭受的疾病产生重大影响。通过经验丰富的科学研究人员作为导师的指导，以及加州大学洛杉矶分校提供的广泛的教育、研究和临床设施网络，这项提议的目的是在五年内促进候选人的学术生涯发展。该提案包括接受培训，成为一名独立的临床科学家，同时调查半胱氨酸对抗氧化剂谷胱甘肽的产生的影响，以及它对危重新生儿氧化组织损伤的影响。与氧化损伤相关疾病的发病率较高的危重新生儿，如慢性肺部疾病和坏死性小肠结肠炎，其体内半胱氨酸和谷胱甘肽水平较低。半胱氨酸是合成谷胱甘肽的限速底物，但它不容易被危重的非肠道喂养的新生儿合成，也不是常规给药。候选人假设，与没有补充半胱氨酸的类似新生儿相比，接受半胱氨酸补充常规肠外营养的危重新生儿将具有更高的合成率和谷胱甘肽的储存水平，从而导致细胞因子炎症反应减弱，氧化组织损伤减少，氧化损伤相关疾病的严重程度降低。为了验证这一假设，我们提出了一项随机、前瞻性、双盲的临床试验，对接受等氮肠外营养的危重新生儿补充半胱氨酸，目的如下：(1)利用一种新的非放射性、稳定的甘氨酸同位素示踪技术，测量红细胞谷胱甘肽的总浓度、红细胞谷胱甘肽的氧化还原比率和红细胞谷胱甘肽的体内合成率；(2)测量血浆白介素6、肿瘤坏死因子-α和丙二醛浓度作为炎症反应严重程度和氧化组织损伤程度的决定因素；以及(3)测量机械通气的持续时间、补充氧气、氧气和氧化组织损伤的程度。住院时间作为病情严重程度的主要临床结局。所获得的数据应该有助于深入了解以前未知的体内谷胱甘肽合成动力学和危重新生儿氧化组织损伤的发病机制，并为改善抗氧化防御的潜在治疗方法提供建议，如补充半胱氨酸。这项调查的结果可能最终改变危重新生儿的标准营养和治疗做法，以改善这些极其脆弱的患者的结局。

DESCRIPTION (provided by applicant): The candidate is a pediatric surgeon and Assistant Professor of Surgery at the David Geffen School of Medicine at UCLA, whose long-term goal is to become an independent clinician-scientist with research that will make a significant impact on diminishing the illnesses endured by neonates. Through the guidance from experienced scientific investigators as mentors and an extensive network of educational, research, and clinical facilities available at UCLA, the purpose of this proposal is to foster the candidate's academic career development over a five-year period. The proposal involves acquiring the training to become an independent clinician-scientist while investigating the effect of cysteine on the production of the antioxidant glutathione and its impact on oxidative tissue injury in critically ill neonates. Low levels of cysteine and glutathione have been demonstrated in critically ill neonates who have a high incidence of disease associated with oxidative-injury, such as chronic lung disease and necrotizing enterocolitis. Cysteine is the rate limiting substrate for the synthesis of glutathione, but it is not readily synthesized by nor routinely given to critically ill, parenterally fed neonates. The candidate hypothesizes that critically ill neonates administered cysteine supplementation with their routine parenteral nutrition will have a higher rate of synthesis and stored levels of glutathione that will subsequently result in a diminished cytokine inflammatory response, less oxidative tissue injury, and a decrease in the severity of oxidative-injury associated diseases compared to similar neonates without cysteine supplementation. To test this hypothesis, a randomized, prospective, double-blinded, clinical trial of cysteine supplementation to critically ill neonates fed isonitrogenous parenteral nutrition is proposed with the following specific aims: (1) to measure total concentrations of erythrocyte glutathione, redox ratios of erythrocyte glutathione, and the in vivo synthetic rates of erythrocyte glutathione utilizing a novel non-radioactive, stable isotope tracer technique with [13C]-glycine, (2) to measure plasma interleukin-6, tumor necrosis factor-a, and malondialdehyde concentrations as determinants of inflammatory response severity and degree of oxidative tissue injury, and (3) to measure the duration of mechanical ventilation, supplemental oxygen, and hospitalization as primary clinical outcomes of disease severity. The data obtained should provide insight into the previously uncharacterized in vivo kinetics of glutathione synthesis and the pathogenesis of oxidative tissue injury in critically ill neonates, as well as suggesting potential therapeutic approaches to improve antioxidant defense, such as cysteine supplementation. The result of this investigation could ultimately change the standard nutritional and treatment practices for critically ill neonates in order to improve the outcome for these extremely fragile patients.