In this Small Business Innovative Research Phase II project, Los Gatos Research (LGR) proposes to develop and test (with collaborators KineMed and Metabolic Solutions) a novel laser-based spectrophotometer (Water Isotope Analyzer) for measurements of glucose metabolism and of energy expenditure. The instrument will be based on LGR's patented Off-Axis ICOS technology. The Water Isotope Analyzer will be capable of real-time monitoring of oxygen and hydrogen isotopes in human and animal biological samples (blood, urine, saliva) directly and without distillation. In this effort, LGR is collaborating with KineMed Inc. and Metabolic Solutions Inc. to develop and deploy this inexpensive, portable and fast instrument for measurements of 2H/1H (or D/H) and 18O/16O in biological samples directly (without distillation) with a target precision of better than 1 per mil for D/H and 0.4 per mil for 18O/16O. System performance will be demonstrated first in gravimetrically prepared water samples and subsequently in aqueous biological (human and animal) samples. All results will be validated by direct comparison with Isotope Ratio Mass Spectrometry (IRMS) measurements made on the same samples. LGR will develop the instrument, MSI and LGR will develop the direct injection strategy, and MSI and KineMed will provide the test samples and measure them using IRMS. At the end of Phase II, a system will be made available to a USDA, NIA- or CALERIE-designated (Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy) laboratory for evaluation. PUBLIC HEALTH RELEVANCE: LGR's proposed Water Isotope Analyzer will operate autonomously in a clinical setting and report real-time measurements of D/H and 18O/16O in human and animal biological samples (blood, urine, saliva). These new and unique instruments will become the standard methodology for the Doubly-Labeled-Water test for energy expenditure, and for metabolic tests for measuring molecular kinetics in living systems, including humans, for metabolic disorders, cancer, and diseases of inflammation and neurodegeneration. The Deuterated Glucose Disposal Test (patented by KineMed) that KineMed will initially deploy with LGR's Water Isotope Analyzer (Phase II instrument) involves measurement of glucose metabolism and thus serves as an indicator of insulin resistance.