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

描述（由申请人提供）：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（TEE）之间的不平衡，因此，准确测量TEE在理解和最终扭转这一流行病方面发挥着关键作用。测量自由生活个体TEE的金标准是双标签水（DLW）法。DLW方法的主要局限性包括成本高，单个测量的精度仅为15%。在这个小型企业创新研究（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激光分析仪，通过同时测量17O/16O来纠正18O和2H的自然同位素波动，从而显著改善DLW对TEE的测量。三同位素水分析仪（TIWA）将基于LGR的专利激光离轴ICOS技术，将能够实时，同时，高通量（50个样品/天）监测人体体液（如血液，尿液和血浆）中的2H/1H， 18O/16O和17O/16O，目标精度优于2H/1H 10.60, 18O/16O 10.20和17O/16O 10.30在自然同位素丰度。对于用2H和18O标记的富集水体，目标精度将与同位素比值质谱法相当，并且优于2H/1H的11.50和18O/16O的10.50。TIWA将允许在TEE测量期间量化同位素背景波动，消除在DLW实验中做出的重要的“恒定背景”假设。对同位素本底波动的测量将允许使用更小的同位素剂量，从而大大降低TEE测量的费用。另外，这些测量可用于显著提高DLW技术的准确性，从而有可能将该技术从人口研究扩展到对个体受试者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方法的主要开发人员John Speakman教授合作，演示使用真空蒸馏临床样品进行测量的原型仪器。将量化40人的2H/1H、18O/16O和17O/16O之间背景波动的相关性，以证明在DLW实验中使用17O/16O信号校正背景波动的适用性。最后，将采用DLW方法对两个个体进行测量，直接比较传统的双同位素测量和新开发的三同位素测量。在本研究项目结束时，LGR将演示使用TIWA进行DLW测量，并通过经验确定使用17O/16O测量背景波动对TEE精度的提高和DLW方法成本的降低。

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.