GLYCEMIA AND EXHALED GASES

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。假设：摄入标准剂量的葡萄糖引起的急性代谢变化将反映在呼出的挥发性有机化合物(VOCs)的离散模式中。几个世纪以来，众所周知，呼吸中含有糖尿病(丙酮)和尿毒症(异戊二烯)等疾病的线索。在过去的十年中，有人认为呼气可能是一种优雅的、非侵入性的工具，可以深入了解肺生理和病理的基本机制。呼出的一氧化氮在哮喘中得到了广泛的研究，目前的证据表明，它可能是支气管炎活动的一个有价值的替代标记物。鲍林和他的同事在1971年报告说，正常的人类呼吸中含有数百种挥发性有机化合物(VOC)的复杂混合物。新的非侵入性、精确和可重复的标记物将有可能从根本上改善许多涉及慢性炎症的疾病的诊断和个性化治疗，这是一个已知的产生VOCs的过程。大多数挥发性有机化合物的呼气浓度都在微微克分子到毫微摩尔之间，这使得它们的测量成为分析的挑战。我们的研究小组自20世纪70年代以来一直致力于大气痕量气体的量化。我们的分析系统能够准确和精确地量化气体浓度，低至20x10-15，或按体积计算的百万分之20(Ppqv)[Colman等人，2001]。我们非常低的检测下限使我们能够观察到呼气中的气体，这是以前没有报道过的。到目前为止，几乎没有呼气研究报告的VOC浓度低于1-2x10-9，或以体积计的百万分之几(Ppbv)。我们的分析能力将使我们能够观察到不同浓度的气体和不同类型的气体(碳氢化合物、卤代烃、烷基硝酸盐和硫磺气体)，这些气体可能是疾病和/或身体功能的标志。呼气中VOCs浓度的变化可能反映了各种生理和病理条件，包括能量代谢的变化和炎症过程的刺激。糖尿病是西方社会发病率、死亡率、社会成本和生活质量恶化影响最大的疾病之一。尽管过去几十年在糖尿病治疗方面取得了许多进展，但根治的可能性仍然不确定，而且这种疾病(尤其是2型糖尿病，更容易受到环境调节的影响)在西方社会的发病率正在以惊人的速度增加。与糖尿病管理相关的一个重要问题是频繁的血糖检测的必要性。目前广泛使用的指纹法每次测量都需要一滴血，这种方法不舒服，通常很痛苦，而且价格昂贵(每一次测量约1.00美元)，通常限制了医生建议增加测试频率的实际适用性。尽管研究人员和制药公司已经投入了大量的精力和资源来尝试寻找非侵入性的、低成本的血糖监测技术，但还没有取得决定性的结果。因此，识别与普遍血糖水平相关的特定呼出气体模式，有可能为一种全新的非静脉血糖监测方法创造生理学基础。类似的葡萄糖浓度可能来自非常不同的代谢状态，这取决于胰岛素、酮体、反向调节激素和其他糖调节介质的同时浓度。由于呼出气体分析不是基于对一种可用气体浓度的测量(如其他实验性无创技术)，而是基于多种(实际上可能是数百种)单个气体浓度的组合，因此可以确定特定的模式，这些模式不仅可以确定血糖，而且还可以定义更复杂的“代谢状态”(高血糖期间是否存在胆酸中毒，低血糖期间高胰岛素血症的深度等)。因此，作为一组初步的测定，在本研究中，我们打算确定一组健康成年志愿者在基线和标准口服葡萄糖耐量试验(OGTT)执行期间呼出的VOCs的生理模式，即在禁食8小时后摄入75克葡萄糖。同时收集呼出的VOCs和血液中的血糖和胰岛素，在基线以及摄入葡萄糖后2.5、5、10、15、20、30、45、60、75、90、105和120分钟进行。

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. Hypothesis: acute metabolic changes induced by ingestion of a standardized dose of glucose will be reflected in discrete patterns of exhaled volatile organic compounds (VOCs). It has been known for centuries that breath contains clues to diseases such as diabetes (acetone) and uremia (isoprene). In the past decade, it has been suggested that exhaled breath gas might be an elegant and non-invasive tool to gain insight into basic mechanisms of pulmonary physiology and pathology. Exhaled nitric oxide has been extensively studied in asthma, and current evidence suggests that it may be a valuable surrogate marker of bronchial inflammatory activity. Pauling and co-workers reported in 1971 that normal human breath contains a complex mixture of several hundred volatile organic compounds (VOCs). New non-invasive, precise and reproducible markers would have the potential to fundamentally improve the diagnosis and individualized therapy of many diseases that involve chronic inflammation, a process known to produce VOCs. Most VOCs are exhaled in pico- to femtomolar concentrations which renders their measurement an analytical challenge. Our research group has been involved in the quantification of atmospheric trace gases since the 1970s. Our analytical system is capable of accurately and precisely quantifying gas concentrations to as low as 20x10-15, or 20 parts per quadrillion by volume (ppqv) [Colman et al., 2001]. Our very low detection limits enable us to observe gases in exhaled breath that have not been previously reported. To date, few if any exhaled breath studies have reported VOC concentrations below 1-2x10-9, or parts per billion by volume (ppbv). Our analytical capabilities will enable us to observe varying concentrations of gases and different types of gases (hydrocarbons, halocarbons, alkyl nitrates, and sulfur gases) that may be markers of disease and/or bodily function. Altered concentrations of VOCs in the exhaled breath are likely to reflect a variety of physiological and pathological conditions, including changes in energy metabolism and stimulation of inflammatory processes. Diabetes is one of the diseases with the largest impact on western society in terms of morbidity, mortality, social cost and deterioration of quality of life. Despite the many advances in diabetes management over the last few decades, the possibility of a permanent cure remains uncertain, and the incidence of the disease (particularly of Type 2 diabbtes, more stongly susceptible to environmemntal modulation) is increasing in western societies at an alarming rate. An important issue associated with diabetes management is the necessity of frequent plasma glucose testing. The current, broadly used fingerstick method, requiring a droplet of blood for each measurement, is uncomfortable, often painful, and expensive (~$1.00 per measurement), often limiting the practical applicability of the physicians suggestion to increase the frequency of testing. Although considerable energy and resources have beenn invested by researchers and drug companies in the attempt to identify non-invasive, low-cost techniques for glucose monitoring, no conclusive results have yet been obtained. The identification of specific exhaled gas patterns correlating with prevailing plasma glucose levels has therefore the potential to create the physiologic basis for a totally new approach to non-ivasive glucose monitoring. Similar glucose concentrations may derive from very different metabolic states, depending on simultaneous concentrations of insulin, ketone bodies, counterregulatory hormones and other glucoregulatory mediators. Because exhaled gas analysis is not based on measurement of one vairable (as other experimental non-invasive techniques are), but on the combination of multiple (indeed potentially hundreds) individual gas concentrations, specific patterns could be idenfitied that would not only determine glycemia, but indeed define a more complex "metabolic state" (presence or not of chetoacidosis during hyperglycemia, depth of hyperinsulinemia during hypoglycemia, etc.). As a preliminary set of determinations, therefore, with the present study we intend to define the physiological patterns of exhaled VOCs in a group of healthy adult volunteers, at baseline and during the performance of a standard oral glucose tolerance test (OGTT), consisting in the ingestion, after 8 hours of fasting, of 75 grams of glucose. Simultaneous collection of exhaled VOCs and blood for glucose and insulin measurments wil be performed at baseline, and at 2.5, 5, 10, 15, 20, 30, 45, 60, 75, 90, 105 and 120 minutes after glucose ingestion.