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Human Nutrition and Metabolism

A Minimally Invasive Tracer Protocol Is Effective for Assessing the Response of Leucine Kinetics and Oxidation to Vaccination in Chronically Energy-Deficient Adult Males and Children^{1 ,2}

Anura V. Kurpad³, Farook Jahoor^*, Sudhir Borgonha, Smita Poulo, Swarna Rekha, Carla R. Fjeld^** and Peter J. Reeds^*

Nutrition Research Center, Department of Physiology, St. John's Medical College, Bangalore 560034, India; ^* U.S. Department of Agriculture/ARS Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX; Department of Pediatrics, St. John's Medical College, Bangalore, India; and ^** U.S. Department of Agriculture, Washington, DC

³To whom correspondence and reprint requests should be addressed.

In disadvantaged populations, recurrent infections lead to a loss of body nitrogen and worsen nutritional status. The resulting malnutrition, in its turn, produces a greater susceptibility to infection. This study aimed to examine the ability of a new minimally invasive tracer protocol to measure leucine oxidation, and then to use it to quantify the effect of vaccination on leucine kinetics and oxidation. Undernourished men (n = 5; body mass index 16.3 ± 0.9 kg/m²) and children (n = 9; age 4.1 ± 0.6 y; weight-for-age Z-score -2.3 ± 0.7) underwent metabolic studies 6 d before and 1 d after vaccination with diphtheria, pertussis and tetanus (DPT). The tracer protocol was performed in the fed state and involved two 3-h sequential periods of frequent (20 min) oral doses of NaH¹³CO₃ or [1-¹³C] leucine. Frequent breath samples and urine collections were made. Blood samples were obtained from the men and used for the determination of the isotopic enrichment of -ketoisocaproic acid. The prevaccination oxidation of leucine (percentage of dose ± SD) was 18.1 ± 2.3 (men) and 16.7 ± 3.8 (children). One day after vaccination, these values had risen to 19.9 ± 1.9 (P < 0.05) in the men and to 19.5 ± 4.6 (P < 0.01) in the children. In the adults, vaccination was associated with a rise in whole-body protein breakdown [mg protein/(kg·h)] from 200 ± 40 to 240 ± 10 (P < 0.05). A minor simulated infection increases leucine catabolism in undernourished humans and this new, minimally invasive protocol is sufficiently sensitive to measure these changes.

KEY WORDS: • infection • protein metabolism • undernourished humans • stable isotopes

This article has been cited by other articles:

				A. V Kurpad, M. M Regan, D. Nazareth, S. Nagaraj, J. Gnanou, and V. R Young Intestinal parasites increase the dietary lysine requirement in chronically undernourished Indian men Am. J. Clinical Nutrition, December 1, 2003; 78(6): 1145 - 1151. [Abstract] [Full Text] [PDF]

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				A. V Kurpad, M. M Regan, T. Raj, S. Varalakshmi, J. Gnanou, P. Thankachan, and V. R Young Leucine requirement and splanchnic uptake of leucine in chronically undernourished adult Indian subjects Am. J. Clinical Nutrition, April 1, 2003; 77(4): 861 - 867. [Abstract] [Full Text] [PDF]