Dramatic Improvements to the Doubly Labeled Water Technique by Measurement of 17O

描述（由申请人提供）：美国肥胖症的高患病率是一个主要的公共卫生问题，因为超重和肥胖个体患许多慢性疾病的风险增加。肥胖源于总热量消耗和总能量消耗（TEE）之间的不平衡，因此TEE的准确测量在理解和最终扭转这种流行病方面起着关键作用。在自由生活的个体中测量TEE的金标准是双标记水（DLW）方法。DLW方法的主要局限性包括高成本和单个测量的精度仅为1.5%。在这个小企业创新研究（SBIR）项目中，洛斯加托斯研究（LGR）将开发、制造和测试一种新型的基于激光的分析仪，通过同时测量17 O/16 O来校正18 O和2 H中的天然同位素波动，从而大大改善TEE的DLW测量。三重同位素水分析仪（TIWA）将基于LGR的专利，基于激光的离轴ICOS技术，将能够实时，同时，高通量（50个样品/天）监测人体体液中的2 H/1H，18 O/16 O和17 O/16 O（例如，血液、尿液和血浆），在天然同位素丰度下，2 H/1H、18 O/16 O和17 O/16 O的目标精度优于10.60、10.20和10.30。对于已用2 H和18 O标记的富集水体沃茨，目标准确度将与同位素比质谱法相当，2 H/1H优于11.50，18 O/16 O优于10.50。TIWA将允许在TEE测量期间量化同位素背景波动，消除DLW实验期间做出的重要“恒定背景”假设。同位素背景波动的测量将允许使用小得多的同位素剂量，从而大大降低TEE测量的成本。或者，这些测量结果可用于显著提高DLW技术的准确性，从而有可能将该技术从人群研究扩展到个体受试者TEE的准确评估。在第一阶段，LGR将与代谢研究的资深研究员Edward Melanson教授和DLW方法的主要开发者John Speakman教授合作，展示一种使用真空蒸馏临床样本进行测量的原型仪器。将对来自40名人类的2 H/1H、18 O/16 O和17 O/16 O之间的背景波动的相关性进行量化，以证明使用17 O/16 O信号校正DLW实验中背景波动的适用性。最后，将使用DLW方法测量两个个体，以直接比较传统的双同位素测量与新开发的三同位素测量。在本研究项目结束时，LGR将演示TIWA用于DLW测量，并根据经验确定TEE准确性的提高和DLW方法成本的降低，这是由于使用17 O/16 O测量背景波动。 公共卫生相关性：肥胖在美国的高患病率是一个主要的公共卫生问题，因为超重和肥胖个体患许多慢性疾病的风险增加。肥胖源于总热量消耗和总能量消耗之间的不平衡，因此准确测量总能量消耗（TEE）在理解和最终扭转这种流行病方面起着关键作用。该小型企业创新研究（SBIR）项目将允许在TEE的双标记水测量期间直接量化同位素背景波动，可能将TEE测量的同位素剂量成本从每个成人受试者约400美元降低到80美元，从而大大增加TEE测量在肥胖研究中的应用。

DESCRIPTION (provided by applicant): The high prevalence of obesity in the US is a major public health concern, as overweight and obese individuals are at increased risk for many chronic diseases. Obesity stems from an imbalance between total caloric consumption and total energy expenditure (TEE), therefore accurate measurements of TEE play a pivotal role in understanding and ultimately reversing this epidemic. The gold standard for measuring TEE in free-living individuals is the doubly labeled water (DLW) method. The major limitations of the DLW method include high cost and precision of only 1 5% for individual measurements. In this Small Business Innovative Research (SBIR) project, Los Gatos Research (LGR) will develop, fabricate, and test a novel, laser-based analyzer to dramatically improve DLW measurements of TEE by concurrently measuring 17O/16O to correct for natural isotopic fluctuations in 18O and 2H. The Triple Isotope Water Analyzer (TIWA), which will be based on LGR's patented, laser-based Off-Axis ICOS technology, will be capable of real-time, simultaneous, high-throughput (50 samples/day) monitoring of 2H/1H, 18O/16O, and 17O/16O in H2O from human bodily fluids (e.g., blood, urine, and plasma), with a target accuracy of better than 10.60 for 2H/1H, 10.20 for 18O/16O, and 10.30 for 17O/16O at natural isotopic abundances. For enriched body waters that have been labeled with 2H and 18O, the target accuracy will be comparable to isotope ratio mass spectrometry and better than 11.50 for 2H/1H, 10.50 for 18O/16O. The TIWA will allow quantification of isotopic background fluctuation during measurements of TEE, eliminating the significant "constant background" assumption made during DLW experiments. Measurement of the isotopic background fluctuation will allow for much smaller isotopic doses to be used, substantially reducing the cost of TEE measurements. Alternatively, these measurements can be used to significantly increase the accuracy of the DLW technique, introducing the possibility of extending this technique from population studies to the accurate assessment of the TEE of individual subjects. During Phase I, LGR will work with Professor Edward Melanson, an established researcher of metabolic studies, and Professor John Speakman, a key developer of the DLW method, to demonstrate a prototype instrument for measurements using vacuum-distilled, clinical samples. The correlation in background fluctuations between 2H/1H, 18O/16O, and 17O/16O from 40 humans will be quantified to demonstrate the applicability of using the 17O/16O signal to correct for background fluctuations in DLW experiments. Finally, two individuals will be measured using the DLW method to directly compare the conventional double isotope measurement to the newly-developed triple isotope measurement. At the conclusion of this research project, LGR will have demonstrated the use of the TIWA for DLW measurements and empirically determined the improvement in TEE accuracy and reduction in the DLW method cost due to the measurement of background fluctuation using 17O/16O. PUBLIC HEALTH RELEVANCE: The high prevalence of obesity in the US is a major public health concern, as overweight and obese individuals are at increased risk for many chronic diseases. Obesity stems from an imbalance between total caloric consumption and total energy expenditure, therefore accurate measurements of total energy expenditure (TEE) play a pivotal role in understanding and ultimately reversing this epidemic. This Small Business Innovative Research (SBIR) project will allow direct quantification of isotopic background fluctuation during doubly-labeled water measurements of TEE, potentially reducing the cost of isotope dose for TEE measurements from approximately $400 to $80 per adult subject and thereby greatly increasing the application of TEE measurements for obesity studies.