Background The brain–gut axis is a key regulator of normal intestinal physiology; for example, psychological stress is linked to altered gut barrier function, development of food allergies and changes in behaviour. Whether intestinal events, such as enteric bacterial infections and bacterial colonisation, exert a reciprocal effect on stress-associated behaviour is not well established. Objective To determine the effects of either acute enteric infection or absence of gut microbiota on behaviour, including anxiety and non-spatial memory formation. Methods Behaviour was assessed following infection with the non-invasive enteric pathogen, Citrobacter rodentium in both C57BL/6 mice and germ-free Swiss-Webster mice, in the presence or absence of acute water avoidance stress. Whether daily treatment with probiotics normalised behaviour was assessed, and potential mechanisms of action evaluated. Results No behavioural abnormalities were observed, either at the height of infection (10 days) or following bacterial clearance (30 days), in C rodentium -infected C57BL/6 mice. When infected mice were exposed to acute stress, however, memory dysfunction was apparent after infection (10 days and 30 days). Memory dysfunction was prevented by daily treatment of infected mice with probiotics. Memory was impaired in germ-free mice, with or without exposure to stress, in contrast to conventionally reared, control Swiss-Webster mice with an intact intestinal microbiota. Conclusions The intestinal microbiota influences the ability to form memory. Memory dysfunction occurs in infected mice exposed to acute stress, while in the germ-free setting memory is altered at baseline.

/pdf/bacterial-infection-causes-stress-induced-memory-dysfunction-34kyu9r6hz.pdf

Bacterial infection causes stress-induced memory dysfunction in mice

Carlos Ricardo Soccol1*, Luciana Porto de Souza Vandenberghe1, Michele Rigon Spier1, Adriane Bianchi Pedroni Medeiros1, Caroline Tiemi Yamaguishi1, Juliano De Dea Lindner1,2, Ashok Pandey3 and Vanete Thomaz-Soccol1,4 Bioprocess Engineering and Biotechnology Department, Federal University of Paraná (UFPR), 81531-990 Curitiba-PR, Brazil State University of Santa Catarina, Food Engineering Department, BR 282, Km 573 Santa Teresinha, 89870-000 Pinhalzinho SC, Brazil Biotechnology Division, National Institut for Interdisciplinary Science and Technology, CSIR, Trivandrum, 695 019, India Positivo University, Industrial Biotechnology Department, Av. Pedro Parigot de Souza 5300, 81280-330, Curitiba-PR, Brazil

/pdf/the-potential-of-probiotics-a-review-4yt3ko22oc.pdf

The potential of probiotics: a review.

The human gastrointestinal tract harbors trillions of bacteria, most of which are commensal and have adapted over time to the milieu of the human colon. Their many metabolic interactions with each other, and with the human host, influence human nutrition and metabolism in diverse ways. Our understanding of these influences has come through breakthroughs in the molecular profiling of the phylogeny and the metabolic capacities of the microbiota. The gut microbiota produce a variety of nutrients including short-chain fatty acids, B vitamins, and vitamin K. Because of their ability to interact with receptors on epithelial cells and subepithelial cells, the microbiota also release a number of cellular factors that influence human metabolism. Thus, they have potential roles in the pathogenesis of metabolic syndrome, diabetes, non-alcoholic fatty liver disease, and cognition, which extend well beyond their traditional contribution to nutrition. This review explores the roles of the gut microbiota in human nutrition and metabolism, and the putative mechanisms underlying these effects.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/jgh.12294

Role of the gut microbiota in human nutrition and metabolism

BACKGROUND Whether probiotics are beneficial at all stages of treatment in inflammatory bowel disease or superior to placebo remains controversial. METHODS Two reviewers independently selected randomized controlled trials comparing probiotics with controls in inflammatory bowel disease and extracted data related to remission/response rates, relapse rates, and adverse events. Subanalyses were also performed. RESULTS Twenty-three randomized controlled trials with a total of 1763 participants met the inclusion criteria. From the meta-analysis, probiotics significantly increase the remission rates in patients with active ulcerative colitis (UC) (P = 0.01, risk ratio [RR] = 1.51). The remission rates were significantly higher in patients with active UC treated with probiotics than placebo (P < 0.0001, RR = 1.80). Unfortunately, subgroup analysis found that only VSL#3 significantly increased the remission rates compared with controls in patients with active UC (P = 0.004, RR = 1.74). Interestingly, VSL#3 (P < 0.00001, RR = 0.18) also significantly reduced the clinical relapse rates for maintaining remission in patients with pouchitis. No significantly different adverse events were detected between probiotics and controls in the treatment of UC (P = 0.94, RR = 0.99) or CD (P = 0.33, RR = 0.87). CONCLUSIONS Administration of probiotics results in additional benefit in inducing remission of patients with UC. VSL#3 are beneficial for maintaining remission in patients with pouchitis. And, probiotics can provide the similar effect as 5-aminosalicylic acid on maintaining remission of UC, although no additional adverse events presented.

Effect of probiotics on inducing remission and maintaining therapy in ulcerative colitis, Crohn's disease, and pouchitis: meta-analysis of randomized controlled trials.

https://www.cell.com/cell-host-microbe/pdf/S1931-3128(10)00077-6.pdf

A Pathobiont of the Microbiota Balances Host Colonization and Intestinal Inflammation

Background: Probiotics are used in the therapy of inflammatory bowel disease. This study aimed to determine whether prior administration of probiotic lactobacilli and bifidobacteria would prevent disease and change gut flora in an animal model of colitis.



Methods:  Swiss albino mice received a probiotic mixture (four Lactobacillus and four Bifidobacterium species) or medium (control) for a week prior to induction of colitis by oral 4% dextran sodium sulfate (DSS) for seven days. Appropriate non-colitis controls were used. Histological damage was assessed (n = 5 per group), as was expression of mRNA for tumor necrosis factor (TNF)-α, interferon (IFN)-γ, transforming growth factor (TGF)-β1 and SOCS-1 in the colonic mucosa (n = 6 per group). Secretion of TNF-α was measured in distal colon organ culture (n = 5–6 per group). Levels of Bacteroides, Bifidobacterium, and Lactobacillus acidophilus in feces were quantified by real time polymerase chain reaction (PCR) targeting 16S rDNA.



Results:  Compared to untreated DSS colitis, probiotic treatment significantly reduced weight loss (P < 0.05), shifted histological damage to lesser grades of severity (P < 0.001), reduced mRNA expression of TNF-α and TGF-β1 (P < 0.05), and down-regulated production of TNF-α from distal colon explants (P < 0.05). Colitis induced a significant reduction in the relative proportions of Bifidobacterium, Bacteroides and Lactobacillus acidophilus group bacteria in feces, and these levels were significantly increased in probiotic-treated mice compared to DSS mice (P < 0.001).



Conclusion:  Prior administration of probiotic bacteria reduced mucosal inflammation and damage in DSS-induced colitis. DSS colitis was associated with significant changes in the fecal anaerobic bacterial flora and these changes were modulated by administration of probiotic bacteria.

Kabirdoss Jayakanthan

Papers

Probiotic administration alters the gut flora and attenuates colitis in mice administered dextran sodium sulfate