The Role of the Gastrointestinal Mucus System in Intestinal Homeostasis: Implications for Neurological Disorders

Abstract

Mucus is integral to gut health and its properties may be affected in neurological disease. Mucus comprises a hydrated network of polymers including glycosylated mucin proteins. We propose that factors that influence the nervous system may also affect the volume, viscosity, porosity of mucus composition and subsequently, gastrointestinal (GI) microbial populations. The gut has its own intrinsic neuronal network, the enteric nervous system, which extends the length of the GI tract and innervates the mucosal epithelium. The ENS regulates gut function including mucus secretion and renewal. Both dysbiosis and gut dysfunction are commonly reported in several neurological disorders such as Parkinson's and Alzheimer's disease as well in patients with neurodevelopmental disorders including autism. Since some microbes use mucus as a prominent energy source, changes in mucus properties could alter, and even exacerbate, dysbiosis-related gut symptoms in neurological disorders. This review summarizes existing knowledge of the structure and function of the mucus of the GI tract and highlights areas to be addressed in future research to better understand how intestinal homeostasis is impacted in neurological disorders.

Jejunal Transcriptomic Profiling for Differences in Feed Conversion Ratio in Slow-Growing Chickens

“…AVD is localized in chicken intestinal goblet cells; given that its expression increases in response to bacterial LPS stimulation, it may serve as an antibacterial mucus layer in the intestinal epithelium [ 76 ]. Variation in the composition of the jejunal mucus layer may be highly important, considering that mucus layer properties are important for the absorptive function of the small intestine [ 77 ]. However, considering that the gene expression profiles of the high-FCR individuals might reduce their immune response, the higher AVD expression may ensure a minimal defense system to protect the epithelium.…”

Adverse Effects of Heat Stress on the Intestinal Integrity and Function of Pigs and the Mitigation Capacity of Dietary Antioxidants: A Review

“…Harmonized regulation of the mucus layer, TJs, IECs and the enteric immune system influences the intestine’s integrity and function [ 9 , 32 ]. The first line of defense against intestinal injury is provided by the intestinal mucus layer [ 70 ], as it serves as a physical barrier against bacteria and antigenic substances in the lumen by coating the interior surface of the intestine and lubricating its luminal contents [ 71 ]. It is composed of mucin glycoprotein (MUC2) and bioactive molecules such as epithelial-bound mucins (MUC1, MUC3 and MUC17), which are synthesized by the intestinal goblet cells [ 72 ] that are confined to the crypts of Lieberkühn and on the small intestinal villi.…”

Disbalance of the intestinal epithelial cell turnover and apoptosis in a rat model of sporadic Alzheimer’s disease

“…Whether the STZ-icv treatment affects all subpopulations of intestinal epithelial cells equally is another important question to be answered in the upcoming experiments. The disbalance of intestinal goblet cell turnover and function might affect the GI barrier by affecting mucus production [11]. Peripherally administered streptozotocin was found to be toxic towards neuroendocrine cells of the gut [73], however, the effect on the population of intestinal neuroendocrine cells was never examined in the STZ-icv rat model of sAD.…”

“…The circadian rhythm dysfunction occurs in the early stage of sAD [8], and host circadian dysrhythmia has been shown to induce dysbiosis and impair intestinal function [9,10]. Furthermore, presymptomatic pathophysiological processes in the CNS may influence GI function and microbiota by affecting the volume, viscosity, and porosity of mucus which plays an integral part in the maintenance of the GI barrier [11]. Interestingly, it has been proposed that brainstem dysfunction precedes neuropathological changes of the supratentorial regions in the early stage of AD [12], and non-invasive measurement of brainstem vagus, the most important neural bidirectional pathway conveying information between the viscera and the brain has been proposed for detection of subtle functional disturbances that may develop even decades before structural damage and clinical symptoms [13].…”