Enriched environment on the intestinal mucosal barrier and brain–gut axis in rats with colorectal cancer

Abstract

An enriched environment (EE) is an animal housing technique in which animals are given increased amounts of space, physical activity, and social interaction. Currently, researchers studying EE focus mainly on its effects within the context of neurological diseases. However, little is known about how EE affects the intestinal mucosal barrier. This study assessed the effects of EE on the intestinal mucosal barrier in rats with colorectal cancer. A rat model of 1,2-dimethylhydrazine (DMH)-induced colorectal cancer was used. The rats were housed in eight conditions for eight weeks: EE, large cages containing eight rats with stimulating objects; enlarged space and socially enriched conditions (ES), large cages containing eight rats; enlarged space and cognition enriched conditions (EC), large cages containing one rat with stimulating objects; enlarged space enriched conditions (E), large cages containing one rat; cognition and socially enriched conditions (CS), four to five rats housed in standard cages containing stimulating objects; cognition enriched conditions (C), rats housed individually in small-size cages containing stimulating objects; socially enriched conditions (S), standard cages containing four rats; and normal conditions (blank group, B). We determined the weight of each rat, measured the intestinal mucosa and plasma levels of tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6), interleukin 10 (IL-10), ghrelin, corticotropin-releasing factor (CRF), occludin, bacterial translocation (BT), and secretory immunoglobulin A (SIgA), and assessed the morphology of the intestinal mucosa. On the whole, the combination of cognitive stimulus and social support was better than the combination of three factors in maintenance of the intestinal mucosal immune barrier and brain–gut peptide. The combination of all three factors and combination of cognitive training and social support were more effective than any single factor. Future studies are needed to study the effects of an EE on body weight, brain–gut peptide, and the intestinal mucosa biological barrier. Impact statement An enriched environment (EE) is an animal housing technique where animals are given increased amounts of space, physical activity, and social interaction. Presently, researchers studying EEs focus mainly on their effects within the context of neurological diseases. However, little is known about how EEs affect the intestinal mucosal barrier. This study assessed the effects of an EE on the intestinal mucosal barrier in rats with colorectal cancer.