Measurement of gut permeability using fluorescent tracer agent technology

Richard B Dorshow,Martin P Debreczeny,Thomas E Rogers,Ravinder J Singh,Roy B Dyer,Carla Hall-Moore,Phillip I Tarr,Jeng Jong Shieh,Nurmohammad Shaikh,Michael R Talcott,James R Johnson,William A Faubion

doi:10.1038/s41598-017-09971-y

Richard B Dorshow, Martin P Debreczeny + Show 10 more

Open Access

https://doi.org/10.1038/s41598-017-09971-y

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Abstract

The healthy gut restricts macromolecular and bacterial movement across tight junctions, while increased intestinal permeability accompanies many intestinal disorders. Dual sugar absorption tests, which measure intestinal permeability in humans, present challenges. Therefore, we asked if enterally administered fluorescent tracers could ascertain mucosal integrity, because transcutaneous measurement of differentially absorbed molecules could enable specimen-free evaluation of permeability. We induced small bowel injury in rats using high- (15 mg/kg), intermediate- (10 mg/kg), and low- (5 mg/kg) dose indomethacin. Then, we compared urinary ratios of enterally administered fluorescent tracers MB-402 and MB-301 to urinary ratios of sugar tracers lactulose and rhamnose. We also tested the ability of transcutaneous sensors to measure the ratios of absorbed fluorophores. Urinary fluorophore and sugar ratios reflect gut injury in an indomethacin dose dependent manner. The fluorophores generated smooth curvilinear ratio trajectories with wide dynamic ranges. The more chaotic sugar ratios had narrower dynamic ranges. Fluorophore ratios measured through the skin distinguished indomethacin-challenged from same day control rats. Enterally administered fluorophores can identify intestinal injury in a rat model. Fluorophore ratios are measureable through the skin, obviating drawbacks of dual sugar absorption tests. Pending validation, this technology should be considered for human use.

Highlights

A cardinal function of the gut is to restrict entry of undigested food, macromolecules, and bacteria into the submucosa, lymphatics, and circulation
Dual sugar absorption testing is a functional assessment of permeability that compares uptake into the circulation of a synthetic disaccharide, generally lactulose (MW = 342), and a monosaccharide, usually mannitol (MW = 182) or rhamnose (MW = 164)
We asked if fluorescent tracer agents that have molecular weights similar to those of the molecules used in the dual sugar absorption test, and which are exclusively excreted by glomerular filtration, could be used to assess intestinal permeability

Summary

Introduction

A cardinal function of the gut is to restrict entry of undigested food, macromolecules, and bacteria into the submucosa, lymphatics, and circulation. Tight junctions between the apical surfaces of the epithelial cells blanket the inner lining of the mucosa and maintain the barrier between luminal contents and the host This barrier is disrupted in many different inflammatory conditions. Dual sugar absorption testing is a functional assessment of permeability that compares uptake into the circulation of a synthetic disaccharide, generally lactulose (MW = 342), and a monosaccharide, usually mannitol (MW = 182) or rhamnose (MW = 164). These sugars are administered together in solution by mouth. The limitations of dual sugar absorption tests largely relate to timing of specimen acquisition, handling of urines, and assay performance. If fluorophores are physiologically equivalent to the sugars, they could offer advantages because their clearance can be measured through the skin, thereby obviating the need to obtain urine and to perform assays to determine relative concentrations

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