Characterizing the metabolic phenotype of intestinal villus blunting in Zambian children with severe acute malnutrition and persistent diarrhea

Abstract

Background: Environmental enteric dysfunction (EED) is widespread throughout the tropics and in children is associated with stunting and other adverse health outcomes. One of the hallmarks of EED is villus damage. In children with severe acute malnutrition (SAM) the severity of enteropathy is greater and short term mortality is high, but the metabolic consequences of enteropathy are unknown. Here, we characterize the urinary metabolic alterations associated with villus health, classic enteropathy biomarkers and anthropometric measurements in severely malnourished children in Zambia.

Methods/principal findings: We analysed 20 hospitalised children with acute malnutrition aged 6 to 23 months in Zambia. Small intestinal biopsies were assessed histologically (n = 15), anthropometric and gut function measurements were collected and the metabolic phenotypes were characterized by 1H nuclear magnetic resonance (NMR) spectroscopy. Endoscopy could not be performed on community controls children. Growth parameters were inversely correlated with enteropathy biomarkers (p = 0.011) and parameters of villus health were inversely correlated with translocation and permeability biomarkers (p = 0.000 and p = 0.015). Shorter villus height was associated with reduced abundance of metabolites related to gut microbial metabolism, energy and muscle metabolism (p = 0.034). Villus blunting was also related to increased sucrose excretion (p = 0.013).

Conclusions/significance: Intestinal villus blunting is associated with several metabolic perturbations in hospitalized children with severe undernutrition. Such alterations include altered muscle metabolism, reinforcing the link between EED and growth faltering, and a disruption in the biochemical exchange between the gut microbiota and host. These findings extend our understanding on the downstream consequences of villus blunting and provide novel non-invasive biomarkers of enteropathy dysfunction. The major limitations of this study are the lack of comparative control group and gut microbiota characterization.

Fig 1. Correlodendogram with pearson correlations among bacterial translocation, intestinal permeability, villus structure, metabolites, and growth variables.

Color intensity and size of the circle are proportional to the correlation coefficients. Significant correlations are shown following correction for multiple testing. FABP, fatty acid binding protein; LAZ, length-for-age Z score; IGF-1, insulin like growth factor 1; IGFBP-3, insulin like growth factor binding protein 3; LPS, lipopolysaccharide; LBP, lipopolysaccharide binding protein; MUAC, mid-upper arm circumference; VH, villus height; VPMM, villus perimeter or epithelial surface area; VW, villus weight; WAZ, weight-for-age Z score; WLZ, weight-for-length Z score.

Fig 2. Mucosal abnormalities in biopsies from hospitalized children.

The biopsies showed a range of abnormalities including (A) moderate villus blunting or (B) total villus atrophy.

Fig 3. Dendogram and heatmap representation of unsupervised hierarchical clustering (HCA) of the metabonome for all children sorted according to the villus height (VH).

Each column corresponds to a single children and each row corresponds to a specific metabolites. Only metabolites identified to correlate with VH through and OPLS model were used for metabolite clustering. Metabolite z-score transformation was performed on the levels of each metabolite across samples, with blue denotating a lower and red a higher level compared to the mean. Metabolites were clustered using correlation distance and average linkage. DMA, dimethylamine; 2-HIB, 2−hydroxyisobutyrate; 4-HPP, 4-hydroxypurate; 4-HPA, 4-hydroxyphenylacetate; 3-IS, 3−indoxyl sulfate; NAG, N-acetylglycoprotein; PAG, phenylacetylglutamine; TMA, trimethylamine.