Gut Barrier Permeability Assessment

The gut barrier was determined by fluorescein isothiocyanate-dextran (FITC-dextran) and the spontaneous elevation of lipopolysaccharides (LPS) and (1→3)-β-D-glucan (BG) in the serum (gut translocation) without systemic infection [23 (link)]. The detection of FITC-dextran, a gut nonabsorbable molecule at a molecular weight of 4.4 kDa, in the serum after an oral administration indicates gut barrier permeability (leaky gut) [41 (link)]. Then, FITC-dextran (Sigma-Aldrich) was orally administered at a concentration of 25 mg/mL in 0.25-mL phosphate buffer solution (PBS) at 3 h before sacrifice, and the serum FITC-dextran was measured by fluorospectrometry (microplate reader; Thermo Scientific, Wilmington, DE, USA). In parallel, serum LPS (endotoxin) BG were measured by HEK-Blue LPS detection (InvivoGen, San Diego, CA, USA) and Fungitell (Associates of Cape Cod, Falmouth, MA, USA). The values of LPS < 0.01 EU/mL and BG <7.8 pg/mL were recorded as 0 due to the limitation of the standard curves.