Determining protein metabolism in young children with HIV - Nutrition in HIV

Nutrition Research Newsletter, August, 2003

Loss of lean body mass is a common problem in adults inflicted with AIDS and it is a major predictor of both morbidity and mortality. Several factors, including reduced food intake, nutrient malabsorption, elevated resting energy expenditure, and altered protein and lipid metabolism, appear to play a role in the loss of lean body mass. However, loss of lean body mass is not a typical finding in asymptomatic, HIV-infected adults. In contrast, growth failure secondary to low rates of lean tissue deposition is a common situation in infants and young children with HIV infection, including those without secondary infections. In these children, early growth failure is an important predictor of a poor prognosis. Therefore, it seems that HIV infection causes a disturbance in protein metabolism that leads to reduced protein deposition in infants and young children, but not in adults. However, there is little known about the protein metabolism in asymptomatic, HIV-infected infants and young children.

Recently, a study was designed to ascertain the effect of HIV infection in the absence of secondary infections on the whole-body protein kinetics of infants and young children. The subjects were studied in the fed state to determine the effect of the virus on splanchnic uptake and utilization of dietary protein as well as on whole-body protein kinetics. Additionally, the rates of synthesis of positive and negative acute phase protein (APPs) were measured to determine whether HIV infection without secondary infection elicits an APP response.

Whole-body and splanchnic leucine kinetics and fractional and absolute synthesis rates of 2 positive and 4 negative APPs were measured in 6 asymptomatic, HIV-infected children (4 males and 2 females) aged 6 to 17 months and 4 uninfected children (3 females and 1 male) aged 7 to 9 months who were in the fed stale.

When compared with the control children, the HIV-infected children had significantly lower dietary energy and protein intakes and leucine balance and significantly faster leucine flux and fractional splanchnic leucine extraction; there was no significant difference between the groups in leucine oxidation rates. Children infected with HIV had significantly higher plasma concentrations and absolute synthesis rates of the positive APPs and a significantly higher fractional synthesis rate of fibrinogen. The concentrations of 2 of the 4 negative APPs, albumin and HDL apolipoprotein A-I, were significantly lower in the HIV-infected children but were not associated with slower synthesis rates.

These results indicated that children with HIV infection but without secondary infection have reduced protein balance due to an inability to down-regulate protein catabolism. Furthermore, the acute phase protein response elicited by HIV infection is characterized by higher concentrations and synthesis rates of positive APPs without lower concentrations of some negative APPs.

F. Jahoor; S. Abramson, W. Heird. The protein metabolic response to HIV infection in young children. Am J Clin Nutr; 78:182-189 (July, 2003). [Correspondence: F Jahoor, Children 's Nutrition Research Center; Department of Pediatrics, Baylor College of Medicine, 1100 Bates Street, Houston, TX 77030-2600. E-mail: fjahoor@bcm.tmc.edu].