Introduction: Lysine is the first limiting essential amino acid in the diet of newborns. First pass metabolism by the intestine of dietary lysine has a direct effect on systemic availability. We investigated whether first pass lysine metabolism in the intestine is high in preterm infants, particularly at a low enteral intake. Patients and methods: Six preterm infants (birth weight 0.9 (0.1) kg) were studied during two different periods: period A (n=6): 40% of intake administered enterally, 60% parenterally; lysine intake 92 (6) μmol/(kgxh); and period B (n=4): 100% enteral feeding; lysine intake 100 (3) μmol/(kgxh). Dual stable isotope tracer techniques were used to assess splanchnic and whole body lysine kinetics. Results: Fractional first pass lysine uptake by the intestine was significantly higher during partial enteral feeding (period A 32 (10)% v period B 18 (7)%; p<0.05). Absolute uptake was not significantly different. Whole body lysine oxidation was significantly decreased during full enterai feeding (period A 44 (9) v period B 17 (3) μmol/(kgxh); p<0.05) so that whole body lysine balance was significantly higher during full enteral feeding (period A 52 (25) v period B 83 (3) μmol/(kgxh); p<0.05). Conclusions: Fractional first pass lysine uptake was much higher during partial enteral feeding. Preterm infants receiving full enteral feeding have lower whole body lysine oxidation, resulting in a higher net lysine balance, compared with preterm infants receiving partial enteral feeding. Hence parenterally administered lysine is not as effective as dietary lysine in promoting protein deposition in preterm infants.,
Gut (English Edition): an international journal of gastroenterology & hepatology
Department of Pediatrics

van der Schoor, S., Reeds, P. J., Stellaard, F., Wattimena, J., Sauer, P., Büller, H., & van Goudoever, H. (2004). Lysine kinetics in preterm infants: The importance of enteral feeding. Gut (English Edition): an international journal of gastroenterology & hepatology, 53(1), 38–43. doi:10.1136/gut.53.1.38