Fecal Lipocalin 2, a Sensitive and Broadly Dynamic Non-Invasive Biomarker for Intestinal Inflammation Original paper

What was studied?

This original research evaluated fecal lipocalin 2 biomarker performance as a non-invasive, highly sensitive readout of intestinal inflammation in mice, with the specific goal of capturing both “low-grade” inflammatory activity (subclinical immune activation) and classic, histopathologically evident colitis. The investigators quantified fecal lipocalin-2 (Lcn-2) using an ELISA assay and compared it against standard inflammation measures including colonic pro-inflammatory gene expression (KC/CXCL1, TNF-α, IL-1β), tissue myeloperoxidase (MPO) activity, serum cytokines, and blinded histopathology scoring. A key design feature was the use of very low dextran sulfate sodium (DSS) concentrations (0.25–0.5%) to model subtle inflammation alongside higher DSS doses (1–4%) producing overt colitis, enabling assessment of biomarker dynamic range and early responsiveness.

Who was studied?

The study population consisted of laboratory mice in two inflammation paradigms. First, eight-week-old male C57BL/6 mice were exposed to DSS in drinking water at 0.25%, 0.5%, 1.0%, or 4.0% for 7 days (n=5 per group), with daily fecal collection to support longitudinal monitoring. Second, eight-week-old female IL-10 knockout mice (n=20) and wild-type controls were housed for 12 weeks to allow variable spontaneous immune-mediated colitis development, after which fecal Lcn-2, colonic MPO, and histology were assessed. Lcn-2 knockout mice were additionally used as negative controls to confirm assay specificity.

Most important findings

Fecal Lcn-2 showed an unusually broad dynamic range and strong sensitivity to early and mild inflammation compared with conventional metrics. In DSS colitis, fecal Lcn-2 rose >10-fold even at 0.25% DSS—doses that produced only modest immune infiltrates on histology and minimal MPO change—while reaching ~10,000-fold elevation at 4% DSS, paralleling severe epithelial loss and dense inflammatory infiltrates. Importantly, fecal Lcn-2 increased as early as day 1 after DSS exposure across all doses, supporting near-real-time inflammation tracking, whereas MPO and robust systemic signals were mainly evident at higher DSS concentrations. In IL-10 knockout mice, fecal Lcn-2 identified severely colitic animals with >3000-fold elevation relative to wild-type means and also tracked milder, variable inflammation across the cohort. During mucosal healing after DSS withdrawal, fecal Lcn-2 rapidly declined, supporting responsiveness to disease resolution. The analyte was also stable with routine storage (4°C or room temperature for 24 hours) but lost ELISA reactivity with high-heat treatment.

Key implications

For microbiome research translation, fecal Lcn-2 provides a scalable host-response readout that can be paired with sequencing-based microbial signatures to improve phenotyping of inflammation-driven dysbiosis. Clinically, the work supports the concept that stool biomarkers can detect early/subclinical gut inflammation—potentially distinguishing inflammatory states from functional disorders—while enabling frequent, non-invasive monitoring over time, an advantage for intervention studies and mechanistic microbiome experiments where repeated endoscopy or tissue sampling is impractical.

Citation

Chassaing B, Srinivasan G, Delgado MA, Young AN, Gewirtz AT, Vijay-Kumar M. Fecal Lipocalin 2, a Sensitive and Broadly Dynamic Non-Invasive Biomarker for Intestinal Inflammation. PLoS ONE. 2012;7(9):e44328. doi:10.1371/journal.pone.0044328