Whole-Body Leucine Kinetics and the Acute Phase Response During Acute Infection in Marasmic Malawian Children

0031-3998/04/5506-0940 PEDIATRIC RESEARCH Vol. 55, No. 6, 2004 Copyright © 2004 International Pediatric Research Foundation, Inc. Printed in U.S.A. Whole-Body Leucine Kinetics and the Acute Phase Response during Acute Infection in Marasmic Malawian Children MARK J. MANARY, KEVIN E. YARASHESKI, RICHARD BERGER, ELIZABETH T. ABRAMS, CHARLES ANTHONY HART, AND ROBIN L. BROADHEAD Departments of Pediatrics [M.J.M.] and Internal Medicine [K.E.Y., R.B.], Washington University School of Medicine, St. Louis, MO 63110, U.S.A.; Department of Anthropology [E.T.A.], University of Michigan, Ann Arbor, MI 48109, U.S.A.; Department of Medical Microbiology [C.A.H.], University of Liverpool, Liverpool L69 3GA, United Kingdom; and College of Medicine [M.J.M., R.L.B.], University of Malawi, Private Bag 360, Blantyre 3, Malawi ABSTRACT This study compared leucine kinetics and acute-phase protein Leucine kinetic rates were similar in marasmic children with and and cytokine concentrations in three groups of Malawian chil- without acute infection. Well-nourished children with acute in- dren who were fed an isoenergetic, isonitrogenous diet: children fection increased their serum concentration of five of six acute- with marasmus with (n ϭ 25) and without (n ϭ 17) infection and phase proteins during the first 24 h, whereas marasmic children well-nourished children with infection (n ϭ13). The hypotheses with infection did not have any increases. The serum concentra- tested were that whole-body leucine kinetics will be less in tions of IL-6 were elevated in well-nourished and marasmic marasmic acutely infected children than in well-nourished children with infection. These data suggest that the cytokine acutely infected children but greater than in marasmic uninfected stimulus for the acute-phase protein kinetic response to acute children. Children were studied after 24 h of therapy using infection is present in marasmic children but that the acute-phase standard 13C-leucine stable isotope tracer techniques. Well- protein metabolic response is blunted by malnutrition. (Pediatr nourished children with acute infection had greater leucine ki- Res 55: 940–946, 2004) netic rates than did marasmic children with acute infection; nonoxidative leucine disposal was 153 Ϯ 31 versus 118 Ϯ 43 ␮mol leucine · kgϪ1 ·hϪ1, leucine derived from whole-body Abbreviations proteolysis was 196 Ϯ 34 versus 121 Ϯ 47, and leucine oxidation Ra, rate of appearance was 85 Ϯ 31 versus 45 Ϯ 13 (p Ͻ 0.01 for all comparisons). TNF-␣, tumor necrosis factor-␣ Severe malnutrition and acute systemic infection are often proteolysis can be accelerated to increase the pool of free coincident and synergistic in children (1). In adults, these two amino acids. Malnutrition decreases protein turnover by low- physiologic states are important determinants of whole-body ering dietary intake of amino acids and limiting proteolysis to protein kinetics. Whole-body protein kinetics are characterized conserve amino acids (3). Acute infection increases protein by the dynamic sum of factors that add to the free amino acid turnover (4) by invoking the acute-phase response, the accel- pool, primarily dietary protein intake and the release of amino erated synthesis of a group of proteins useful to the host in acids during proteolysis, and those factors that subtract from successfully responding to the infection (5, 6). Understanding this pool, namely the use of amino acids in the synthesis of new how malnutrition and acute infection together affect protein protein and the oxidation of amino acids (2). Protein synthesis metabolism in children may give insight into the optimum is limited by the availability of free amino acids, and muscle dietary therapy to facilitate recovery, as well as increase the knowledge of the interaction between nutritional status and immunity. Received July 10, 2003; accepted November 20, 2003. Correspondence: Mark J. Manary, M.D., Department of Pediatrics, Washington Uni- Unfortunately, little is known about these relationships, versity School of Medicine, St. Louis Children’s Hospital, One Children’s Place, St. primarily because of the complexity and challenges in measur- Louis, MO 63110, U.S.A.; e-mail: [email protected] ing protein kinetics in young children. In addition, primary Supported by National Institutes of Health (RO1HD38422), the Washington University Biomedical Mass Spectrometry Facility (NIH RR00954), and Clinical Nutrition Research malnutrition usually occurs in poor populations in the devel- Unit (NIH P30 DK56341). oping world, far removed from the clinical research units DOI: 10.1203/01.pdr.0000127017.44938.6d where protein kinetics are often studied. This study used a 940 METABOLISM IN MALNUTRITION AND INFECTION 941 standard 13C-leucine stable isotope tracer dilution method to Metabolic study. The protocol and calculations for the met- measure whole-body leucine kinetics (7) in Malawian children abolic study have been described and validated previously with marasmus with and without acute infection and compares from a subset of the children included in this report (11, 12). them with well-nourished Malawian children with acute infec- Briefly, at 19 h after admission, each child’sCO2 appearance tion. The hypotheses tested were that nonoxidative leucine rate was determined with a primed (2.5 ␮mol/kg), constant (5 disposal and leucine derived from whole-body proteolysis ␮mol · kgϪ1 · hϪ1) 70-min infusion of 13C-sodium bicarbonate would be less in marasmic acutely infected children than in (99% 13C; Cambridge Isotopes, Andover, MA, U.S.A.). Before well-nourished acutely infected children but greater than in the 13C-sodium bicarbonate infusion was started, breath sam- marasmic uninfected children. In addition, the magnitude of ples were collected using a silicone rubber face mask con- the cytokine and the acute-phase response was measured and nected to a nondiffusing gas collection bag (Hans Rudolph, compared in these groups of children. 13 Kansas City, MO, U.S.A.) to determine the baseline CO2 isotope abundance. Breath samples were collected 60, 65, and 70 min after the initiation of the 13C-sodium bicarbonate METHODS infusion for the measurement of the CO2 appearance rate. Immediately after the collection of these breath samples, a Subjects. Children who were aged 12–60 mo and had primed constant i.v. infusion of 1-13C-leucine (99% 13C) was marasmus and were admitted to Queen Elizabeth Central Hos- begun. Each child received 1-13C-leucine (prime 15.3 ␮mol/ pital in Blantyre, Malawi, were eligible. Marasmus was defined kg, infusion 4 ␮mol · kgϪ1 · hϪ1) for 5 h. During the 5-h Ͻ as having weight-for-age 60% of the international standard infusion, children received feedings in small aliquots every 30 (8) and evidence of wasting, manifest by weight-for-height min. The amount of each feed was such that it provided the Ͻ 80% of the international standard. After mothers gave their same rate of dietary energy intake (350 kJ · kgϪ1 · dϪ1)asthe informed consent for their child’s participation, each child was 2-h feedings. This was done so that the metabolic measure- admitted to a special metabolic ward, which provided more ments would be representative of the fed state rather than the intensive nursing care, better parenteral antibiotics, more fre- postabsorptive state. At 4.5 and 5 h after the start of the leucine quent feedings, and more careful clinical monitoring than the infusion, 24 h after admission and the initiation of feedings, a hospital ward. The initial evaluation of these children included 1-mL blood sample was drawn to measure isotopic abundance blood culture, urine culture obtained by sterile catheter, chest of ␣-ketoisocaproic acid. Three breath samples were collected x-ray, thick blood smear for malaria parasites, and an ELISA 4.5, 4.75, and 5 h after the start of the leucine infusion for the for HIV (Vironostika HIV; Organon Teknika, Durham, NC, measurement of 13CO isotope abundance, representative of U.S.A.). Every child received parenteral ceftriaxone for the 2 leucine oxidation. first 48 h after admission. Acute infection was defined as Sera for the measurement of the concentrations of six acute- sepsis, malaria, or pneumonia. Sepsis was defined as clinical phase proteins, C-reactive protein, properdin factor B, C3, signs of sepsis with a positive blood or urine culture, malaria ␣ ␣ haptoglobin, 1-antitrypsin, and 1-acid glycoprotein, and the was defined as clinical signs of falciparum malaria with a ␤ ␣ ␣ positive smear for malaria parasites, and pneumonia was de- cytokines IL-1 , IL-6, and tumor necrosis factor- (TNF- ) were drawn on admission and 24 and 48 h after admission. fined as cough and tachypnea with a focal infiltrate on chest 13 12 x-ray. The infections were believed to be acute because ac- Sample analyses. In 10-mL aliquots of breath, CO2/ CO2 cording to the caregiver’s report, each child’s clinical condition abundance was measured using an automated gas isotope ratio ϩ had worsened within the day before admission. As a compar- mass spectrometer (Finnigan MAT Delta XL, Bremen, Ger- ison group, children who had weight-for-age within the norms many) (13). ␣ of the World Health Organization’s reference population and Plasma -ketoisocaproic acid, the intracellular deamination 13 acute infection and received the same diet as the malnourished product of leucine, was used to estimate intracellular C- children were enrolled. The study was approved by the Human leucine enrichment. Serum samples were analyzed by gas Studies Committee of Washington University (St. Louis, MO, chromatography electron impact-quadruple mass spectrometry U.S.A.) and the College of Medicine Research Committee of (Agilent Technologies 6890N capillary GC system and 5973 the University of Malawi. Network Mass Selection Detector, Foster City, CA, U.S.A.) Diet. The metabolic ward diet provided 350 kJ · kgϪ1 · dϪ1 after the ␣-ketoisocaproic acid was converted to its quinoxa- (85 kcal) and 1.2 g · kgϪ1 · dϪ1 of protein to all children.

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