Dynamic Changes in Colonic Structure and Protein Expression Suggest Regulatory Mechanisms of Colonic Barrier Function in Torpor–Arousal Cycles of the Daurian Ground Squirrel

Abstract

Background: Both pathological conditions and hibernation can affect the barrier function of small intestine mucosa. However, the effect of hibernation on the barrier function of colonic mucosa remains unclear. Methods: We investigated morphological changes in colonic mucosa, the concentrations of specific proteins and molecules, and the enzymatic activity of diamine oxidase (DAO), in serum and colonic tissue; the expression of tight junction proteins and mucin, and the changes in inflammatory, farnesoid X receptor (FXR)–small heterodimer partner (SHP), and apoptosis-related molecules that could play a role in gut permeability changes in Daurian ground squirrels in summer active (SA), late torpor (LT), and interbout arousal (IBA) periods. Results: The results show that hibernation reduced the thickness of the colonic mucosa and the depth of the crypt, decreased the number of goblet cells (GCs), and damaged the structure of some microvilli. The concentrations of proteins and molecules, and the enzymatic activity of DAO, were all increased in the serum and colon, and the localization of tight junction proteins and mucin in the colonic mucosa were altered (compensatory response). Although the ground squirrels ate during the interbout arousal period, the changes remained similar to the response to torpor. Inflammation, apoptosis–anti-apoptosis, and FXR–SHP signaling may be involved in the possible changes in intestinal gut permeability during the torpor–arousal cycle in Daurian ground squirrels. In addition, periodic interbout arousal may play an inflammation-correcting role during the long hibernation season of Daurian ground squirrels.

Prevention of Loperamide-Induced Constipation in Mice and Alteration of 5-Hydroxytryotamine Signaling by Ligilactobacillus salivarius Li01

“…Immunofluorescent images were acquired by using laser scanning confocal microscopy (Leica, Wetzlar, Germany). Five fields were randomly selected from each section, and the thickness of muscle and the depth of crypts were measured using Caseviewer software [ 22 ].…”

Integrated transcriptomics and metabolomics reveal protective effects on heart of hibernating Daurian ground squirrels

“…All procedures were in accordance with the guidelines of the Experimental Animal Management Committee of the Ministry of Health of the People's Republic of China (approval number: SL2012‐42). Daurian ground squirrels were housed and treated as previously described by our laboratory (Han et al, 2022; Miao et al, 2022). Two groups of ground squirrels were studied.…”

“…The average length of torpor was 7.4 ± 3.7 days, and accounted for about 89.9% of the whole hibernation period, and the average length of IBA was about 1.4 days, which accounted for about 10.1% of the whole hibernation period. The average length of a torpor‐arousal cycle was about 8.8 days (Miao et al, 2022).…”

“…During hibernation, small mammalian hibernators such as ground squirrels exhibit a remarkable drop in body temperature (often to just 2-10°C), reduced metabolic rate, slower heartbeat, and significantly lower organ perfusion rates (often less than 10% of normal) (Han et al, 2022;Horii et al, 2018). Despite these extreme physiological changes, ground squirrels experience brief interbout arousal (IBA) periods every few days or weeks that are characterized by a rapid return to euthermic body temperature and normal organ perfusion rates, before sinking into another torpor bout within ~24 h. Such torpor-arousal cycles are repeated multiple times over the hibernation season (Miao et al, 2022). Hence, over the annual hibernation cycle, tissues and organs undergo repeated bouts ischemiareperfusion (I/R) and major changes in body temperature, but ground squirrels have evolved mechanisms to resist the damage that often arises from such conditions in non-hibernators, including humans (Andrews, 2007;Han et al, 2022;Otis et al, 2017) Compared with non-hibernators, the heart of hibernating species is highly protected, showing a strong resistance to myocardial ischemia, allowing animals to be protected from I/R injury, which is similar to protection against ischemia that can be achieved with preconditioning (Yan et al, 2015).…”

Activation of MyD88-Dependent TLR Signaling Modulates Immune Response of the Mouse Heart during Pasteurella multocida Infection

“…Hematoxylin and eosin (HE) staining was conducted according to routine protocols [ 22 ]. Briefly, paraffin-embedded hearts were cut into 4 μm thick sections using LEICA RM2016 (LEICA, Wetzlar, Germany).…”