Submitted on July 9, 2008
Revised on February 6, 2009
Accepted on February 21, 2009
Small intestinal MUC2 synthesis in human preterm infants
Maaike W Schaart1, Adrianus C.J.M de Bruijn1, Henk Schierbeek2, Dick Tibboel1, Ingrid B Renes1, and Johannes B. van Goudoever2*
1 ErasmusMC-Sophia Children's Hospital
2 ErasmusMC
* To whom correspondence should be addressed. E-mail: j.vangoudoever{at}erasmusmc.nl.
Introduction: Mucin 2 (MUC2) is the structural component of the intestinal protective mucus layer, which contains high amounts of threonine in its peptide backbone. MUC2 synthesis rate might be a potential parameter for intestinal barrier function. Aims: To determine whether systemic threonine was used for small intestinal MUC2 synthesis and to calculate the MUC2 fractional synthetic rate (FSR) in human preterm infants. Methods: Seven preterm infants with an enterostomy following bowel resection for necrotising enterocolitis received intravenous infusion of [U-13C]threonine to determine incorporation of systemic threonine into secreted MUC2 in intestinal outflow fluid. Small intestinal MUC2 was isolated using cesium chloride (CsCl) gradient ultracentrifugation and gravity gel filtration chromatography. MUC2-containing fractions were identified by SDS-PAGE/Periodic Acid-Schiff's staining and Western blot analysis and were subsequently pooled. Isotopic enrichment of threonine, measured in MUC2 using Gas Chromatography Isotopic Ratio Mass Spectrometry, was used to calculate the FSR of MUC2. Results: Systemically derived threonine was indeed incorporated into small intestinal MUC2. Median FSR of small intestinal MUC2 was 67.2 (44.3-103.9) % per day. Conclusions: Systemic threonine is rapidly incorporated into MUC2 in the small intestine of preterm infants, and thereby, MUC2 has a very high synthesis rate.
