Endomicroscopic and Transcriptomic Analysis of Impaired Barrier Function and Malabsorption in Environmental Enteropathy

PLoS Negl Trop Dis. 2016 Apr 6;10(4):e0004600. doi: 10.1371/journal.pntd.0004600. eCollection 2016 Apr.

Abstract

Introduction: Environmental enteropathy (EE) is associated with growth failure, micronutrient malabsorption and impaired responses to oral vaccines. We set out to define cellular mechanisms of impaired barrier function in EE and explore protective mechanisms.

Methods: We studied 49 adults with environmental enteropathy in Lusaka, Zambia using confocal laser endomicroscopy (CLE); histology, immunohistochemistry and mRNA sequencing of small intestinal biopsies; and correlated these with plasma lipopolysaccharide (LPS) and a zinc uptake test.

Results: CLE images (median 134 for each study) showed virtually ubiquitous small intestinal damage. Epithelial defects, imaged by histology and claudin 4 immunostaining, were predominantly seen at the tips of villi and corresponded with leakage imaged in vivo by CLE. In multivariate analysis, circulating log-transformed LPS was correlated with cell shedding events (β = 0.83; P = 0.035) and with serum glucagon-like peptide-2 (β = -0.13; P = 0.007). Zinc uptake from a test dose of 25mg was attenuated in 30/47 (64%) individuals and in multivariate analysis was reduced by HIV, but positively correlated with GLP-2 (β = 2.72; P = 0.03). There was a U-shaped relationship between circulating LPS and villus surface area. Transcriptomic analysis identified 23 differentially expressed genes in severe enteropathy, including protective peptides and proteins.

Conclusions: Confocal endomicroscopy, claudin 4 immunostaining and histology identify epithelial defects which are probably sites of bacterial translocation, in the presence of which increased epithelial surface area increases the burden of translocation. GLP 2 and other protective peptides may play an important role in mucosal protection in EE.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biopsy
  • Environmental Exposure*
  • Gastrointestinal Diseases / pathology*
  • Gene Expression Profiling
  • Histocytochemistry*
  • Immunohistochemistry
  • Lipopolysaccharides / analysis
  • Microscopy*
  • Plasma / chemistry
  • Sequence Analysis, RNA
  • Zambia
  • Zinc / metabolism

Substances

  • Lipopolysaccharides
  • Zinc

Grant support

Financial support was obtained from The Bill & Melinda Gates Foundation (www.gatesfoundation.org), grant number OPP1066118 to PK. AW was supported by BBSRC grant BB/J004529/1: The Gut Health and Food Safety ISP. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.