Protein turnover in low-birth-weight (LBW) infants

Protein deposition in infants results from an equilibrium between protein synthesis and degradation. Separate measurements of these two simultaneous processes are required for a better understanding of the mechanisms and regulation of growth. Current methods of assessment of whole-body protein synthesis and degradation rely on the use of stable isotope labelled tracer and are briefly reviewed and discussed ("end-products" and precursor method) with an emphasis on their practical and conceptual limits. Overall, protein turnover is higher in infants than in adults, but there are discrepancies within the literature, which are mostly due to methodological differences. The relationships between energy expenditure and protein turnover and the mechanisms of protein deposition during feeding (which is inhibition of protein degradation rather than stimulation of protein synthesis) are also described. Finally, we review the few available data on protein turnover modifications induced by various pathophysiological states.