Feasibility Study to Assess a Trans-nasal Intestinal Potential Difference Probe

Increased gastrointestinal (GI) permeability is associated to several GI conditions that affect millions of people worldwide. Healthy intestinal walls limit only specific molecules to cross into the body. "Leaky gut" is a condition of unregulated and increased gut permeability that allows unwanted antigens, pathogens and microbial toxins into the bloodstream(1). This in turn leads to a subsequent immune response that includes the production of inflammatory mediators. Leaky gut is a key feature in celiac disease, Crohn's disease, inflammatory bowel disease (IBD), and environmental enteropathy and have been associated with systemic diseases including type 1 diabetes, autoimmune hepatitis, and systemic lupus erythematosus (SLE).

The current gold standard for measuring intestinal permeability is the sugar ratio test. Non-metabolized sugars of different molecular sizes are orally administered and the amount of sugar molecules absorbable across the gut lining is then quantified by measuring their relative concentrations in urine. In healthy subjects, low to none of the large-molecule disaccharides can be taken into the circulatory system, while the small-molecule monosaccharides can readily diffuse into the bloodstream. This results in low disaccharide/monosaccharide (DM) ratios for healthy subjects. Subjects with the leaky gut conditions exhibit high DM ratios in their urine. However, the sugar ratio test has low specificity, does not provide specific information on etiology, is challenging to implement when pristine urine samples cannot be collected (e.g. infants), and does not account for spatially heterogeneous disease.

An alternative approach for measuring mucosal permeability is through measuring the voltage across the intestinal wall (Intestinal potential difference; IPD) that changes with intestinal permeability. The Tearney lab has developed an IPD measuring device (IPD probe) that can be deployed trans-nasally and can measure the intestinal potential difference in real time at selected locations of the gut. The probe contains a central channel that allows us to infuse specific ionic solutions into the gut. The IPD probe also has an optical fiber inside the channel that enables the acquisition of M-mode OCT images. The M-mode OCT images make it possible to determine when the IPD probe is in contact with the tissue.