Effects of food and gastrointestinal secretions on intestinal integrity in an experimental rat model

The present study aimed to investigate the individual and combined effects of food and biliopancreatic secretions on intestinal morphology, tight junction (TJ) protein expression and microbial composition in a rat model. A total of 30 male Sprague‑Dawley rats were randomly allocated into three groups: Control, biliopancreatic diversion and jejunal bypass. Jejunal segments were surgically manipulated to selectively exclude biliopancreatic secretions, food or both. Corresponding control segments were also collected. Intestinal samples were analysed for villus height/crypt depth ratios and intraepithelial lymphocyte (IEL) counts using H&E staining, as well as TJ protein expression (occludin, claudin‑1, zonula occludens‑3) measured using immunohistochemistry. In addition, portal venous blood samples were obtained to assess serum lipopolysaccharide and citrulline levels using ELISA. Furthermore, quantitative bacterial cultures were performed on jejunal tissues. The villus height/crypt depth ratio was significantly reduced in segments deprived of both bile and food (P=0.007), and IEL counts were significantly elevated in food‑ and bile‑deficient segments (P<0.001). Moreover, claudin‑1 expression was significantly lower in food‑deficient segments (surgically created intestinal segment that is bypassed from luminal nutrient flow)(BPS1 and JPS2) (P=0.035), whereas occludin expression was increased in the presence of food (P=0.016). In conclusion both food and biliopancreatic secretions are essential in maintaining intestinal epithelial morphology and TJ integrity. Food deprivation induced more pronounced changes in intestinal integrity than the absence of biliopancreatic secretions. The present findings highlight the synergistic role of luminal nutrition and digestive secretions in preserving gut barrier function.