Effects of short-term fasting on gut-associated lymphoid tissue and intestinal morphology in mice

Background & aims: Modern management guidelines for surgical patients recommend that the fasting period before surgery be as short as possible. This study aimed to examine the influences of 24-h fasting, with and without water, on intestinal morphology, mucosal IgA levels and gut-associated lymphoid tissue (GALT) cells as a center of systemic mucosal immunity in mice. Methods: Male Institute of Cancer Research mice (6-week-old, n = 24) were divided into three groups: ad libitum chow and water (Control), 24-h fasting without water (Fasted − water), and 24-h fasting with ad libitum water (Fasted + water). The Fasted + water group was used to examine possible influences of dehydration on the parameters measured. After a 24-h fasting, nasal and bronchoalveolar lavage were done under anesthesia. Then, the mice were killed by cardiac puncture. The whole small intestine was harvested and intestinal washing was obtained by lavage. Jejunal and ileal morphologies were evaluated by H&E staining. IgA levels in the intestinal, nasal, and bronchoalveolar washings were determined using ELISA. Lymphocytes were isolated from Peyer's patches (PPLs), the intraepithelial spaces (IELs), and lamina propria (LPLs) of the small intestine and GALT lymphocyte numbers were evaluated. Results: Villous height and crypt depth in the jejunum and ileum were both significantly lower in the Fasted − water and Fasted + water than in the Control group, with no significant difference between the Fasted − water and Fasted + water groups. There were no significant differences in mucosal IgA levels among the 3 groups. PPL numbers were similar in the three groups; however, significant decreases were observed in IEL and LPL numbers in the Fasted − water and Fasted + water groups as compared to the Control. Conclusions: Regardless of water supply, 24 h of fasting causes gut atrophy, with marked GALT lymphocyte losses in the IE space and LP.