The Intestinal Barrier and Current Techniques for the Assessment of Gut Permeability

Abstract

The intestinal barrier is essential in human health and constitutes the interface between the outside and the internal milieu of the body. A functional intestinal barrier allows absorption of nutrients and fluids but simultaneously prevents harmful substances like toxins and bacteria from crossing the intestinal epithelium and reaching the body. An altered intestinal permeability, a sign of a perturbed barrier function, has during the last decade been associated with several chronic conditions, including diseases originating in the gastrointestinal tract but also diseases such as Alzheimer and Parkinson disease. This has led to an intensified interest from researchers with diverse backgrounds to perform functional studies of the intestinal barrier in different conditions. Intestinal permeability is defined as the passage of a solute through a simple membrane and can be measured by recording the passage of permeability markers over the epithelium via the paracellular or the transcellular route. The methodological tools to investigate the gut barrier function are rapidly expanding and new methodological approaches are being developed. Here we outline and discuss, in vivo, in vitro and ex vivo techniques and how these methods can be utilized for thorough investigation of the intestinal barrier.

Prevention of Rat Intestinal Injury with a Drug Combination of Melatonin and Misoprostol

“…The role of the intestinal mucosa is to form a selective and dynamic barrier between the external luminal contents and the underlying tissue and systemic circulation [1]. It should restrict passage of potentially harmful intestinal constituents, such as microbiota, toxins, and allergens, while allowing carrier-mediated and/or passive transport of water, nutrients, and ions.…”

New Stable Cell Lines Derived from the Proximal and Distal Intestine of Rainbow Trout (Oncorhynchus mykiss) Retain Several Properties Observed In Vivo

“…These values are consistent with those of fish intestine and RTgutGC cells [ 23 ] that are considered as “leaky” epithelia [ 35 ]. Nevertheless, all cell lines formed a monolayer that significantly attenuated the permeation of FITC-Dextran 4000, a well-documented paracellular probe, widely used to study intestinal permeability in vitro [ 36 ]. This result confirms and extends previous observations describing RTgutGC as able to form a barrier that strongly attenuates dextran and albumin translocation from the apical to the basolateral chamber [ 18 , 27 , 32 , 37 ].…”

Nutritional considerations to counteract gastrointestinal permeability during exertional heat stress

“…I-FABP is applicable in EHS due to its usefulness as marker of acute ischemia (33) and its causal relationship with permeability as well as innate barrier function (34). Although biomarkers like I-FABP are becoming more prevalent, orally ingested probes that are assessed in the urine, like saccharides, are still commonly utilized (35). I-FABP and saccharide ratios such as lactulose/mannitol or lactulose/rhamnose are primarily used for the measurement of small intestine permeability, whereas LPS and LPS binding protein are nonspecific.…”