PROJECT SUMMARY/ABSTRACT Obesity and associated metabolic disorders are among the most common and costly health concerns confronting Western nations. The University of Washington (UW) has been a pioneer in cutting-edge research into mechanisms regulating energy homeostasis and how defects in this system contribute to these disorders. Integral to this research effort are support services provided to the research community by the NIDDK-funded Nutrition Obesity Research Center (NORC). The mission of the UW NORC is to support research in nutrition and obesity, enhance our understanding of causal mechanisms and identify novel, effective and safe treatments for these disorders. In support of this mission, the UW NORC Energy Balance Core has provided a research core infrastructure to investigators for over 20 years that allows comprehensive assessment of energy balance via the simultaneous measurement of energy expenditure, energy intake, substrate utilization and physical activity in rodent models. This S10 grant application seeks to upgrade, expand and transform our capacity to support metabolic research by requesting funds to purchase a new, state-of-the-art 16 cage Promethion Core indirect calorimetry System from Sable Systems International. Our original Columbus Instruments OxyMax indirect calorimetry system is no longer operational and our current 16 cage Sable Systems Promethion Core system is sufficiently old (>13 years) that several parts necessary for routine maintenance and repair are no longer supported by the company. In the coming months, therefore, the very real possibility exists that we will no longer be able to either support funded research or honor commitments made (in the form of letters of support supplied to investigators for inclusion in their NIH grant proposals). At the same time, demand for our services currently exceeds capacity, resulting in long wait times that further limit productivity. To address these concerns, we request funding to support the purchase of new equipment that will not only increase throughput, reducing wait times and improving scientific productivity, but also offer exciting new capabilities while ensuring that commitments made to our research community are honored. Specific features of the new equipment we seek include 1) computer-controlled food access hoppers to allow for pair-feeding or time-restricted feeding studies, 2) metabolic cages designed for use with optogenetics and other sophisticated neuroscience techniques such as fiber photometry that enable manipulation and/or monitoring the activity of discrete neuronal populations while also quantifying energy balance, and 3) a stable isotope gas analyzer for the measurement of 13C and 18O in exhaled breath for precise assessments of substrate oxidation from exogenously- or endogenously-labeled sources. Together, these new capabilities will allow the NORC to further expand its research base and support novel science endeavors that are currently not p...