Sulfur amino acid metabolism in children with severe childhood undernutrition: methionine kinetics

Abstract

Children with edematous but not nonedematous severe childhood undernutrition (SCU) have lower plasma and erythrocyte-free concentrations of cysteine and methionine, which suggests a decreased availability of methionine for cysteine synthesis. We propose that methionine production and metabolism will be slower in children with edematous SCU than in those with nonedematous SCU. We aimed to measure methionine flux, its transmethylation and its transsulfuration, and homocysteine remethylation in children with SCU. Methionine kinetics were measured in 2 groups of children with edematous (n = 11) and nonedematous (n = 11) SCU when they were infected and malnourished (clinical phase 1), when they were still severely malnourished but no longer infected (clinical phase 2), and when they had recovered (clinical phase 3). At clinical phase 1, children with edematous SCU had rates of total methionine flux, flux from protein breakdown, and flux to protein synthesis that were slower than the rates of the nonedematous group. There were no significant differences in homocysteine remethylation or methionine transsulfuration and transmethylation between the groups at clinical phase 1. These findings suggest that, in the acutely malnourished and infected state, children with edematous SCU have slower methionine production than do children with nonedematous SCU because of a slower rate of release from protein breakdown. This slower methionine production is not, however, associated with slower rates of methionine transsulfuration and transmethylation or homocysteine remethylation.