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, zinc status 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
The progress described below are related to “Problem Statement 3A: Understand the Causes and Consequences of Obesity and Related Disorders” [Objective 1], and “Problem Statement 4A: Understand Mechanisms by which Nutrition Promotes Healthy Development and Function from Conception to Old Age” [Objective 2]. After we established how fast a labeled fatty acid oxidizes in the body as fuel, we designed the second level of this experiment. We obtained institutional license and initiated the multiple-dose phase of the human study. Palmitic acid fully labeled with the stable isotope C-13 is given with food to volunteers after every dinner for two weeks. As predicted by our model, we observe elevated C-13 in breath carbon dioxide samples resulting from “burning” the labeled palmitic acid together with the other foods. The volunteers are receiving all their meals from the metabolic kitchen in our institution and provide us with several breath samples per day. At the mid-point of their participation, we change their caloric intake to a lower level. As a result we expect to observe even higher levels of C-13 in breath. Working backwards we can calculate the amount of “new carbon” entering the body as food, diluting the C-13 isotope. This experiment (in progress) is a response investigation to test the validity of our mathematical model and the first of its kind performed with human subjects. At its final form this work will produce a breath test method to calculate average energy intake in free-living adults. This year’s work also completed the evaluation of two instruments for rapid isotopic analysis in breath; a mass spectrometer and a laser absorption resonance cavity. We installed a dedicated mass spectrometer for this project. A computer code was developed in Visual Basic to test the effect of repeated measurements using the hand-held X-ray caliper instrument when measuring tissue composition at mid-thigh. Eleven computerized tomography (CT) images were used as input for the mathematical analysis. The computer program simulated soft tissue analysis for several variations of caliper re-positioning. We concluded that an error of 2mm in re-positioning translated into a % fat measurement error of 0-2%, depending on the specific morphology of the subject. Computer software for the X-ray Fluorescence (XRF) instrument for the analysis of bromine in plasma and urine was fully developed. It included the programming of the instrument’s microprocessor which controls the automation of the sample handling. We also fully developed the data acquisition software. The two programs work together for automated XRF analysis. A full prototype was tested. The instrument was designed for portability and use in the field.
1. A method to gauge frailty Patients with unwanted weight loss and the elderly are screened for “frailty” using five physiological criteria related to their ability to perform some tasks. This definition provides only a Yes/No result. ARS-funded researchers at JMUSDA-HNRCA at Tufts University, Boston, MA, using their newly developed field methods and utilizing data from their studies and a national database, developed a more detailed test that assigns a numerical value to the level of frailty. The impact of this approach is significant. The test requires no cooperation from the subject and because of its numerical outcome, the results can be used to monitor effectiveness of nutritional support and quality of care. The results were published (in press) at the Journal of Nutrition Health and Aging.