Sweet food improves chronic stress-induced irritable bowel syndrome-like symptoms in rats

To investigate whether palatable sweet foods have a beneficial effect on chronic stress-induced colonic motility and inflammatory cytokines.

Adult male rats were divided into 3 groups: control (CON, n = 5), chronic variable stress with chow (CVS-A, n = 6), and chronic variable stress with chow and sweet food (CVS-B, n = 6). The rats were fed standard rodent chow as the chow food and/or AIN-76A as the sweet food. A food preference test for AIN-76A was performed in another group of normal rats (n = 10) for twelve days. Fecal pellet output (FPO) was measured for 6 wk during water bedding stress in the CVS groups. The weight of the adrenal glands, adrenocorticotropic hormone (ACTH) and corticosterone levels in plasma were measured. The expression levels of transforming growth factor-β, interleukin (IL)-2, and interferon-gamma (IFN-γ) were measured in the distal part of colonic tissues and plasma using Western blot analysis.

In sweet preference test, all rats initially preferred sweet food to chow food. However, the consumption rate of sweet food gradually decreased and reduced to below 50% of total intake eight days after sweet food feeding. Accumulated FPO was higher in the CVS-A group compared with the CVS-B group over time. All stress groups showed significant increases in the adrenal to body weight ratio (CVS-A, 0.14 ± 0.01; CVS-B, 0.14 ± 0.01) compared with the control group (0.12 ± 0.01, P < 0.05). The plasma corticosterone and ACTH levels were significantly higher in the CVS-A (537.42 ± 32.95, 44.44 ± 6.54 pg/mL) and CVS-B (655.07 ± 30.82, 65.46 ± 4.44 pg/mL) groups than in the control group (46.96 ± 13.29, 8.51 ± 1.35 pg/mL, P < 0.05). Notably, the ratio of corticosterone to ACTH was significantly increased in the CVS-A group only. Rats exposed to CVS displayed significantly increased expression of IL-2 and IFN-γ in the plasma and distal colon compared to the control group, whereas this effect was significantly attenuated in the CVS-B group.

These results suggest that concurrent sweet food ingestion during CVS might have an effect on the reduction of stress-induced colonic hyper-motility and pro-inflammatory cytokine production in rats.