Microbes and the gut‐brain axis

Abstract

Background The 'gut-brain' or 'brain-gut axis', depending on whether we emphasize bottom-up or top-bottom pathways, is a bi-directional communication system, comprised of neural pathways, such as the enteric nervous system (ENS), vagus, sympathetic and spinal nerves, and humoral pathways, which include cytokines, hormones, and neuropeptides as signaling molecules. Recent evidence, mainly arising from animal models, supports a role of microbes as signaling components in the gut-brain axis. Aims The purpose of this review is to summarize our current knowledge regarding the role of microbes, including commensals, probiotics and gastrointestinal pathogens, in bottom-up pathways of communication in the gut-brain axis. Although this has clear implications for psychiatric co-morbidity in functional and inflammatory conditions of the gut, the focus of this review will be to discuss the current evidence for a role of bacteria (commensals, probiotics, and pathogens) as key modulators of gut-brain communication. Results & Conclusions The strongest evidence for a role of microbes as signaling components in the gut-brain axis currently arises from animal studies and indicate that mechanisms of communication are likely to be multiple. There is need for the concepts generated in animal models to be translated to the human in the future.

The intestinal microbiome, probiotics and prebiotics in neurogastroenterology

“…A growing body of evidence suggests that the host-microbial interaction may result in dysregulated neuroimmune functions, impacting behavior. 3,4 Probiotic bacteria, "live microorganisms which when administered in adequate amounts confer a health benefit on the host," and dietary prebiotics, "selectively fermented dietary ingredients that result specific changes, in the consumption and/ or activity of the gastrointestinal microbiota, thus conferring benefit(s) upon host health" (www.isapp.net), have been used in proinflammatory cytokines, including tumor necrosis factor-α (TNF), on signaling pathways, specifically myosin light chain kinase (MLCK), that govern tight junction permeability. 5 In this case, MLCK phosphorylates myosin light chain, which interacts with actin, driving cytoskeletal contraction of the perijunctional actomyosin ring that underlies tight junctions thus, increasing paracellular permeability.…”

Adición de Enterococcus faecium mejora poblaciones celulares inmunes y anticuerpos vacunales de lechones destetos

“…Tras la interacción con probióticos estas células secretan ciertas citoquinas que regulan la función de las células T reguladoras, lo que resulta en la inmunomodulación (Forsythe & Bienenstock, 2010). Esto da como resultado un sistema inmunológico eficaz disminuyendo la susceptibilidad a diversas inflamaciones y alergias (tolerancia) a través de diversos ejes tracto grastrointestinal (TGI) -órganos de inmunomodulación, es decir, eje TGI-cerebro, TGI-, pulmón y TGI-piel (Forsythe, 2011;Philpott, Gibson & Thien, 2011;Bercik, Collins & Verdu, 2012). Dicha inmunomodulación ocurre simultáneamente de dos maneras: i) por la presencia de antígenos alimentarios de la nueva dieta y ii) por el consumo de bacterias probióticas que ayudan al equilibrio bacteriano y a la activación controlada del sistema inmune.…”

Microbiota in Obesity

“…Modification on the overall structure of the gut microbiome and resultant shift in the fecal metabolic profiles characterized by marked increase in SCFA, ketones, carbon disulfide, and methyl acetate, suggests potential positive health effects of pro and prebiotics [37]. Some prebiotics exerts their anti-obesogenic function by decreasing appetite and increasing satiety, leading to a lowered total energy intake, as well as a reduced hepatic de novo lipogenesis [38][39][40][41][42][43][44][45] In a 12 week randomized control trial conducted to study the influence of oligofructose on body weight in obese and overweight subjects, a reduction in caloric intake which coincided with increased PYY and decreased grehlin levels were recorded, this indicatings the potential weight loss effect of oligofructose in treatment of obesisty [46][47][48][49][50] Faecal transplantation is yet another suggested means of combating obesity. Promising findings were obtained after transplantation of stools from lean subjects to achieve weight loss [40,[50][51][52][53][54][55][56].…”