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United States Department of Agriculture

Agricultural Research Service

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Location: Jean Mayer Human Nutrition Research Center On Aging

2010 Annual Report

1a. Objectives (from AD-416)
1. Develop and validate mathematical models for carbon kinetics that simulate energy intake, energy regulation, and their relationship to body composition and fat stores. 2. Develop and validate practical field tools for the assessment and management of sarcopenia, dehydration and frailty in institutionalized and community living elderly.

1b. Approach (from AD-416)
Simple monitoring of isotope clearance in breath CO2 can provide quantitative information on average energy intake. Our approach includes the use of a single stable isotope administration (C-13 palmitic acid) and monitoring its disappearance in breath CO2. We will use both mathematical modeling and clinical validation of this approach. The development and validation of new portable body composition tools will include the comparison of a hand-held caliper X-ray absorptiometer against tissue analysis by computerized tomography and the full evaluation of a nondestructive method for rapid analysis of extracellular water by X ray fluorescence analysis for stable bromine. For free-living elderly, we expect that portable body composition tools will provide an additional way to help monitor their medical, functional, and nutritional status so that they can extend safely their independent living.

3. Progress Report
We developed a mathematical model to simulate carbon kinetics and energy regulation. A computer code was created that simulates the kinetics of carbon in fuel, assuming that the subject has consumed a known dose of C-13 labeled fatty acid, and calculates the presence of C-13 in breath. To perform this calculation we included some assumptions in the form of pre-determined parameters. The body composition of the subject has been one of the main parameters as the adipose tissue compartment is the main store of energy. The model allows the user to vary the composition of food intake. Details on the participation of free fatty acids and the liver were studied with an animal model. Now we can adjust the parameters of the model to fit data with human volunteers, when they become available. At its final stage the computer code will produce not only predicted isotope clearance curves in breath CO2, but will also calculate the average energy intake based on a series of breath tests. In addition to the mathematical model, we investigated and tested several instruments for the isotopic measurements in breath. A stand-alone computer code was developed in Visual Basic for specialized analysis of mid-thigh computerized tomography (CT) scans. This development was necessary for the validation of the hand-held X-ray absorption instrument that was developed in our laboratory. The purpose of this new computer code was to validate the hand-held instrument against CT. The code allows the user to determine a narrow cylindrical area within the CT image that corresponds to the X-ray beam path of the hand-held instrument. It makes possible the direct comparison of tissue analysis between the new instrument and CT. It also offers the capability to simulate the magnitude of reproducibility errors caused by re-positioning the hand-held instrument. The X-ray Fluorescence (XRF) instrument for the analysis of bromine in plasma and urine was fully designed. The materials for the mechanical parts were selected and tested so that they do not contribute interfering fluorescence photons to the measurement of bromine. The electronic circuit design was completed based on a microprocessor and a microscopic self-cooled solid state detector. The instrument was designed for portability and use in the field. For publications related to project see project #1950-51000-071-00D.

4. Accomplishments
1. A rapid and inexpensive method to determine de-hydration and frailty ARS-funded researchers from Tufts University in Boston, MA have proven the feasibility of measuring extracellular water space in the field using miniaturized equipment. The method replaces traditional neutron activation analysis for plasma bromine, which requires access to a nuclear reactor, or high-performance liquid chromatography (HPLC), which requires extensive sample preparation in the laboratory. Using our non-destructive X-ray technique, the plasma specimen can be analyzed in its original plastic container without opening the vial or contaminating the sample. The method provides a rapid way to determine de-hydration and frailty in nursing homes. Dehydration is a major cause of hospitalization of nursing home residing elderly. This method will make possible the early detection of dehydration and protect the elderly from its compilations.

Last Modified: 06/28/2017
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