Background Glutamine is a conditionally essential amino acid for very-low-birth weight infants (VLBW) by virtue of its ability to play an important role in several key metabolic processes of immune cells and enterocytes. Other non-essential amino acids such as aspartate and glutamate are important fuel sources for the splanchnic tissues. Although glutamine is known to be utilized to a great extend, the exact splanchnic metabolism is unknown.
Aims To study whole-body and splanchnic glutamine metabolism and to determine the primary metabolic fate of glutamine in the splanchnic tissues.
Methods Five, fully enterally fed, preterm infants (mean (SD) birth weight 1.07 kg±0.22 SD, gestational age 29 wk±2 SD, range 26–31 wk) were studied by dual tracer ([U-13C]glutamine and [15N2]glutamine) techniques on two consecutive study days (within mean postnatal week 3±1 wk). Splanchnic and whole-body glutamine kinetics were assessed by plasma isotopic enrichment of [U-13C]glutamine and [15N2]glutamine and breath 13CO2 enrichments.
Results Mean (SD) fractional first-pass glutamine uptake was 73±6% on d1 and 51±11% on d2. Mean (SD) whole body glutamine oxidation was 340±73 μmol/kg/h of which 55±6% occurred in the splanchnic tissues.
Conclusion Dietary glutamine is used to a great extent by the splanchnic tissues in preterm infants. More than half of the whole-body glutamine oxidation occurs in the splanchnic tissues, stressing its important role as oxidative fuel source for the enterocytes.