The ageing gastrointestinal tract

Abstract

Alterations in gut function with ageing have particular implications for oesophageal, gastric, and colonic motility. Older individuals are particularly susceptible to malnutrition, postprandial hypotension, dysphagia, constipation, and faecal incontinence. Decrease in the number of nerve cells of the myenteric plexus that impact digestive absorption and the surface area of the small intestine because of degeneration of villi may lead to blunted absorption of nutrients. Impairment of the intestinal immune system as a result of ageing, including the mucosal layer of the gastrointestinal tract, appears to be a significant contributor to the age-related increase in the incidence and severity of infections.

Secretory Products of the Human GI Tract Microbiome and Their Potential Impact on Alzheimer's Disease (AD): Detection of Lipopolysaccharide (LPS) in AD Hippocampus

“…We sincerely hope that this “Perspectives” article has effectively highlighted recent findings on microbial-derived endotoxins, exotoxins, LOSs and LPSs, amyloids and sncRNAs and has stimulated interest in the potential contribution of these neurotoxic and pro-inflammatory microbial exudates to age-related inflammatory neurodegeneration, amyloidogenesis, and AD-relevant pathology (Figure 1). Taken together, these current observations and recent data advance at least seven areas in our understanding of the role of the GI tract microbiome in age-related neurological diseases associated with progressive, inflammatory neurodegeneration of the human brain: (i) that the GI tract microbiome are a potent source of neurotoxic species that are abundantly secreted by multiple Gram-negative bacilli in the gut ( B. fragilis, E. coli , and others); (ii) that bacterial LPS are readily detectable in the neocortex and hippocampus of the AD brain, and at significantly higher abundance in AD than controls, indicating that LPS may be able to transit physiological barriers to access CNS compartments (Figure 2); (iii) that the transit of highly pro-inflammatory neurotoxins such as LPS across compromised GI tract and blood-brain barriers underscore the critical roles of cellular adhesion structures in allowing passage of noxious molecules from the GI tract into the systemic circulation and CNS (Montagne et al, 2016; Soenen et al, 2016; van de Haar et al, 2016); (iv) that extremely complex mixtures of neurotoxins may be generated by either single microbes or by combinations of bacilli that constitute the GI tract microbiome (Figure 1); (v) that biophysical, gastrointestinal, and neurobiological barriers that may become more “leaky” with aging again underscore the important role of intact membrane barriers in moderating systemic and CNS inflammation and immune-mediated inflammatory disease (Hill and Lukiw, 2015; Keaney and Campbell, 2015; Montagne et al, 2015; Choi et al, 2016; Köhler et al, 2016; Minter et al, 2016a; Richards et al, 2016; van de Haar et al, 2016; Zhan and Davies, 2016; Varatharaj and Galea, 2017); (vi) that bacterial complexity, neurotoxin abundance, speciation, and complexity in the CSF, blood serum or in brain tissues may be useful for the diagnosis of AD (Zhao et al, 2015; Soenen et al, 2016); and (vii) that studies on the thanatomicrobiome should be useful for a clearer understanding of the neuro- and micro-biological processes in operation over the PMI that should be useful in scientific research that utilizes post-mortem tissues in basic research, in forensic applications, in criminology and in the more accurate diagnosis of neurological disease (Clement et al, 2016; Javan et al, 2016). While one other recent investigation reported the detection of LPS in gray matter (temporal lobe) and white matter (frontal lobe) in AD (Zhan et al, 2016), here for the first time we report the detection of bacterial LPS in brain lysates from AD hippocampus, an anatomical region of the AD brain that develops the earliest and most profound neuropathology.…”

Factors affecting successful colonoscopy procedures: Single-center experience

“…Reducing the flexures in colorectal surgery may provide advantage for colonoscopy. Increase in colon length and decrease in resistance are seen by age (16). In the literature, advanced age was shown as the factor for failure in colonoscopy (17).…”

Mechanisms of Cell Polarity–Controlled Epithelial Homeostasis and Immunity in the Intestine

“…Along the same lines, further studies are required to determine the organization and function of the endosomal system, expression, and function of cell polarity -determining proteins, and immunity-regulating cell-surface proteins (1) along the vertical (crypt-to-villus) axis (e.g., Lindfors et al 2001;Xiong et al 2016), (2) along the horizontal (from duodenum to colon) axis of the intestine (Middendorp et al 2014), and (3) as a function of age (Man et al 2014;Soenen et al 2016), and to determine how variations herein contribute to the regulation of intestinal epithelial homeostasis and immunity.…”