Small intestinal MUC2 synthesis in human preterm infants

Abstract

Schaart MW, de Bruijn ACJM, Schierbeek H, Tibboel D, Renes IB, van Goudoever JB. Small intestinal MUC2 synthesis in human preterm infants. Am J Physiol Gastrointest Liver Physiol 296: G1085-G1090, 2009. First published February 26, 2009 doi:10.1152/ajpgi.90444.2008 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. In this study, we aimed 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. Seven preterm infants with an enterostomy following bowel resection for necrotizing 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 gradient ultracentrifugation and gravity gel filtration chromatography. MUC2-containing fractions were identified by SDS-PAGE/periodic acid-Schiff 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. 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. Systemic threonine is rapidly incorporated into MUC2 in the small intestine of preterm infants, and thereby MUC2 has a very high synthesis rate. mucin 2; small intestine; threonine THE MUCUS LAYER FORMS a physical barrier between the underlying epithelium and the lumen of the gastrointestinal tract.(9) It protects the epithelium against noxious agents, viruses, and pathogenic bacteria. The structural component of this mucus layer is secretory mucin 2 (MUC2), which is secreted by goblet cells of the intestine and gives intestinal mucus a high density and viscoelasticity (30). MUC2 is a glycoprotein rich in oligosaccharides, O-linked to threonine and serine residues in the peptide backbone (29). MUC2 contains high amounts of threonine and proline tandem repeat sequences, which together constitute 20 -55% of total amino acid composition (33). Threonine is an indispensable amino acid utilized in a large amount by the portal-drained viscera in first pass (28). Recently, we showed that the equivalent of almost 90% of dietary threonine is utilized by the intestine of piglets (25). The high visceral need for threonine presumably reflects the high synthesis rate of secretory mucins, e.g., MUC2. Therefore, threonine might be one of the amino acids essential for maintaining the protective mucus layer and thus intestinal barrier function.Disturbances in intestinal barrier function, characterized by inappropriate initial bacterial colonization of the intestine and immature epithelial responses to bacteria and their toxins, are thought to be crucial in the dev...

Modulation of the gut microbiota with antibiotic treatment suppresses whole body urea production in neonatal pigs

“…We measured the fractional synthesis rate and protein expression of MUC2, since this is a major component of goblet cell mucus and thus mucosal host defense. The MUC2 fractions we identified showed great similarity to that found in human preterm infants (39,40). Colonic MUC2 FSR representing the percentage of MUC2 newly synthesized per day was 48, 34, and 57%/day in CO, AB, and PRO pigs, respectively (Fig.…”

“…MUC2 was isolated from colonic tissue using a cesium chloride density gradient ultracentrifugation method combined with gravity gel filtration chromatography, as previously described for human MUC2 in detail (39,40,50). A small aliquot of purified MUC2 was used for confirmation of MUC2 by Western blot, and the remaining was hydrolyzed as described above for the tissue protein hydrolysates.…”

“…Colon tissue samples were homogenized in HIS buffer containing protease inhibitors, and an aliquot was used for Western blotting of MUC2 as described previously (39). MUC2 expression was normalized to ␤-actin immunoreactivity.…”

Effects of Lactobacillus acidophilus and zinc oxide on the growth performance, jejunal morphology and immune function of weaned piglet following an Escherichia coli K88 challenge

“…To the best of our knowledge, data of the influence of nutritional factors on mucin gene expression in the intestinal tract of pigs are limited (Sargeant et al 2010;Liu et al 2014). The mucus layer is organised by the highly glycosylated MUC2 mucin (Johansson et al 2011), and MUC2 synthesis rate might be a potential factor for intestinal barrier (Schaart et al 2009). No influence of age or Zn supplementation was observed on the expression of MUC2 in the distal jejunum of weaned piglets , however, MUC2 concentration was improved with increased Zn supplementation.…”

Nutrition for Preterm Infants: 75 Years of History

“…That may be influenced by the high prevalence of antibiotic use in the first period of life [28], the environment (a NICU with many selected pathogens [29]), the altered mucin production rates and quality [30], the motility [31], and the immune system.…”