Cognitive impairment by antibiotic-induced gut dysbiosis: Analysis of gut microbiota-brain communication

Comparison of inflammatory and behavioral responses to chronic stress in female and male mice

Major depressive disorder (MDD) is a debilitating disease with a high worldwide prevalence. Despite its greater prevalence in women, male animals are used in most preclinical studies of depression even though there are many sex differences in key components of depression, such as stress responses and immune system functions. In the present study, we found that chronic restraint stress-induced depressive-like behaviors are quite similar in male and female mice, with both sexes displaying increased immobility time in the tail suspension test and reduced social interactions, and both sexes exhibited deficits in working and spatial memories. However, in contrast to the similar depressive-like behaviors developed by male and female mice in response to stress, they displayed different patterns of pro-inflammatory cytokine increases in the periphery and the brain, different changes in microglia, and different changes in the expression of Toll-like receptor 4 in response to stress. Treatment with (+)-naloxone, a Toll-like receptor 4 antagonist that previously demonstrated anti-depressant-like effects in male mice, was more efficacious in male than female mice in reducing the deleterious effects of stress, and its effects were not microbiome-mediated. Altogether, these results suggest differential mechanisms to consider in potential sex-specific treatments of depression.

Linking Puberty and the Gut Microbiome to the Pathogenesis of Neurodegenerative Disorders

Puberty is a critical period of development marked by the maturation of the central nervous system, immune system, and hypothalamic-pituitary-adrenal axis. Due to the maturation of these fundamental systems, this is a period of development that is particularly sensitive to stressors, increasing susceptibility to neurodevelopmental and neurodegenerative disorders later in life. The gut microbiome plays a critical role in the regulation of stress and immune responses, and gut dysbiosis has been implicated in the development of neurodevelopmental and neurodegenerative disorders. The purpose of this review is to summarize the current knowledge about puberty, neurodegeneration, and the gut microbiome. We also examine the consequences of pubertal exposure to stress and gut dysbiosis on the development of neurodevelopmental and neurodegenerative disorders. Understanding how alterations to the gut microbiome, particularly during critical periods of development (i.e., puberty), influence the pathogenesis of these disorders may allow for the development of therapeutic strategies to prevent them.

The acute effects of antimicrobials and lipopolysaccharide on the cellular mechanisms associated with neurodegeneration in pubertal male and female CD1 mice

Exposure to stressors during puberty can cause enduring effects on brain functioning and behaviours related to neurodegeneration. However, the mechanisms underlying these effects remain unclear. The gut microbiome is a complex and dynamic system that could serve as a possible mechanism through which early life stress may increase the predisposition to neurodegeneration. Therefore, the current study was designed to examine the acute effects of pubertal antimicrobial and lipopolysaccharide (LPS) treatments on the cellular mechanisms associated with neurodegenerative disorders in male and female mice. At five weeks of age, male and female CD-1 mice received 200 μL of broad-spectrum antimicrobials or water, through oral gavage, twice daily for seven days. Mice received an intraperitoneal (i.p.) injection of either saline or LPS at 6 weeks of age (i.e., pubertal period). Sickness behaviours were recorded and mice were euthanized 8 h post-injection. Following euthanasia, brains and blood samples were collected. The results indicated that puberal antimicrobial and LPS treatment induced sex-dependent changes in biomarkers related to sickness behaviour, peripheral inflammation, intestinal permeability, and neurodegeneration. The findings suggest that pubertal LPS and antimicrobial treatment may increase susceptibility to neurodegenerative diseases later in life, particularly in males.

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Pubertal antimicrobial and LPS treatment increase cytokine concentrations.

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Antimicrobial and LPS treatment have sex-specific effects on intestinal permeability.

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They also induce sex-specific changes in neurodegenerative markers.

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Antimicrobial treatment did not potentiate LPS-induced sickness behaviours.

Maternal Obesity and Gut Microbiota Are Associated with Fetal Brain Development

Obesity in pregnancy induces metabolic syndrome, low-grade inflammation, altered endocrine factors, placental function, and the maternal gut microbiome. All these factors impact fetal growth and development, including brain development. The lipid metabolic transporters of the maternal-fetal-placental unit are dysregulated in obesity. Consequently, the transport of essential long-chain PUFAs for fetal brain development is disturbed. The mother’s gut microbiota is vital in maintaining postnatal energy homeostasis and maternal-fetal immune competence. Obesity during pregnancy changes the gut microbiota, affecting fetal brain development. Obesity in pregnancy can induce placental and intrauterine inflammation and thus influence the neurodevelopmental outcomes of the offspring. Several epidemiological studies observed an association between maternal obesity and adverse neurodevelopment. This review discusses the effects of maternal obesity and gut microbiota on fetal neurodevelopment outcomes. In addition, the possible mechanisms of the impacts of obesity and gut microbiota on fetal brain development are discussed.

Prenatal Maternal Antibiotics Treatment Alters the Gut Microbiota and Immune Function of Post-Weaned Prepubescent Offspring

This study aimed to investigate the immediate and continual perturbation to the gut microbiota of offspring in the weeks post-weaning and how these may be modulated by treating pregnant C57BL/6J dams with antibiotics (ABX). We used a broad-spectrum antibiotic cocktail consisting of ampicillin 1 mg/mL, neomycin 1 mg/mL, and vancomycin 0.5 mg/mL, or vancomycin 0.5 mg/mL alone, administered ad-lib orally to dams via drinking water during gestation and stopped after delivery. We analyzed the gut microbiota of offspring, cytokine profiles in circulation, and the brain to determine if there was evidence of a gut-immune-brain connection. Computationally predicted metabolic pathways were calculated from 16s rRNA sequencing data. ABX treatment can negatively affect the gut microbiota, including reduced diversity, altered metabolic activity, and immune function. We show that the maternal ABX-treatment continues to alter the offspring's gut microbiota diversity, composition, and metabolic pathways after weaning, with the most significant differences evident in 5-week-olds as opposed to 4-week-olds. Lower levels of chemokines and inflammatory cytokines, such as interleukin (IL)-1α and IL-2, are also seen in the periphery and brains of offspring, respectively. In conclusion, this study shows maternal antibiotic administration alters gut microbiome profiles in offspring, which undergoes a continuous transformation, from week to week, at an early age after weaning.

Impact of polyphenols on stress and anxiety: a systematic review of molecular mechanisms and clinical evidence

Mental health is a global public concern that contributes raising disability and premature death. Anxiety undertakes around 3.6% of the global population, while psychological stress is a condition associated to anxiety with a prevalence of 36.5%. Treatment for both mental conditions consist mainly of psychological therapy and pharmacotherapy, but the long-term drugs use can trigger adverse effects. Growing evidence shows the effect of specific food compounds on stress and anxiety treatment. The aim of this systematic review is to describe the molecular mechanisms related to dietary polyphenols administration from food matrix (considering food, juices or herbal/food extracts) and their effects on stress and/or anxiety, as well as review the available clinical evidence. Search was based on PRISMA Guidelines using peer-reviewed journal articles sourced from PubMed and Web of Science. A total of 38 articles were considered as eligible. The major effects for anxiety management were: reduction of oxidative stress and inflammation; HPA axis modulation; and regulation of some serotonergic/adrenergic pathways. There is a very limited evidence to conclude about the real effect of dietary polyphenols on stress. Although pharmacological treatment for mood disorders is essential, alternative therapies are necessary using non-pharmacological compounds to improve the long-term treatment effectiveness.

The effect of Aβ seeding is dependent on the presence of knock-in genes in the App NL-G-F mice

Alzheimer's disease (AD) is characterized by the prion-like propagation of amyloid-β (Aβ). However, the role of Aβ in cognitive impairment is still unclear. To determine the causal role of Aβ in AD, we intracerebrally seeded the entorhinal cortex of a 2-month-old App NL-G-F mouse model with an Aβ peptide derived from patients who died from rapidly progressing AD. When the mice were 3 months of age or 1 month following seeding, spatial learning and memory were tested using the Morris water task. Immunohistochemical labeling showed seeding with the Aβ was found accelerate Aβ plaque deposition and microgliosis in the App NL-G-F mice, but this was dependent on the presence of the knocked-in genes. However, we found no correlation between pathology and spatial performance. The results of the present study show the seeding effects in the App NL-G-F knock-in model, and how these are dependent on the presence of a humanized App gene. But these pathological changes were not initially causal in memory impairment.

Microbiome influences on neuro-immune interactions in neurodegenerative disease

Mounting evidence points to a role for the gut microbiome in a wide range of central nervous system diseases and disorders including depression, multiple sclerosis, Alzheimer's disease, Parkinson's disease, and autism spectrum disorder. Moreover, immune system involvement has also been implicated in these diseases, specifically with inflammation being central to their pathogenesis. In addition to the reported changes in gut microbiome composition and altered immune states in many neurological diseases, how the microbiome and the immune system interact to influence disease onset and progression has recently garnered much attention. This chapter provides a review of the literature related to gut microbiome influences on neuro-immune interactions with a particular focus on neurological diseases. Gut microbiome-derived mediators, including short-chain fatty acids and other metabolites, lipopolysaccharide, and neurotransmitters, and their impact on neuro-immune interactions as well as routes by which these interactions may occur are also discussed.

The gut-immune-brain axis in neurodevelopment and neurological disorders

The gut-brain axis is gaining momentum as an interdisciplinary field addressing how intestinal microbes influence the central nervous system (CNS). Studies using powerful tools, including germ-free, antibiotic-fed, and fecal microbiota transplanted mice, demonstrate how gut microbiota perturbations alter the fate of neurodevelopment. Probiotics are also becoming more recognized as potentially effective therapeutic agents in alleviating symptoms of neurological disorders. While gut microbes may directly communicate with the CNS through their effector molecules, including metabolites, their influence on neuroimmune populations, including newly discovered brain-resident T cells, underscore the host immunity as a potent mediator of the gut-brain axis. In this review, we examine the unique immune populations within the brain, the effects of the gut microbiota on the CNS, and the efficacy of specific probiotic strains to propose the novel concept of the gut-immune-brain axis.

Dietary Fiber Modulates the Release of Gut Bacterial Products Preventing Cognitive Decline in an Alzheimer's Mouse Model

Fiber intake is associated with a lower risk for Alzheimer´s disease (AD) in older adults. Intake of plant-based diets rich in soluble fiber promotes the production of short-chain fatty acids (SCFAs: butyrate, acetate, propionate) by gut bacteria. Butyrate administration has antiinflammatory actions, but propionate promotes neuroinflammation. In AD patients, gut microbiota dysbiosis is a common feature even in the prodromal stages of the disease. It is unclear whether the neuroprotective effects of fiber intake rely on gut microbiota modifications and specific actions of SCFAs in brain cells. Here, we show that restoration of the gut microbiota dysbiosis through the intake of soluble fiber resulted in lower propionate and higher butyrate production, reduced astrocyte activation and improved cognitive function in 6-month-old male APP/PS1 mice. The neuroprotective effects were lost in antibiotic-treated mice. Moreover, propionate promoted higher glycolysis and mitochondrial respiration in astrocytes, while butyrate induced a more quiescent metabolism. Therefore, fiber intake neuroprotective action depends on the modulation of butyrate/propionate production by gut bacteria. Our data further support and provide a mechanism to explain the beneficial effects of dietary interventions rich in soluble fiber to prevent dementia and AD. Fiber intake restored the concentration of propionate and butyrate by modulating the composition of gut microbiota in male transgenic (Tg) mice with Alzheimer´s disease. Gut dysbiosis was associated with intestinal damage and high propionate levels in control diet fed-Tg mice. Fiber-rich diet restored intestinal integrity and promoted the abundance of butyrate-producing bacteria. Butyrate concentration was associated with better cognitive performance in fiber-fed Tg mice. A fiber-rich diet may prevent the development of a dysbiotic microbiome and the related cognitive dysfunction in people at risk of developing Alzheimer´s disease.

Exploring the potential antidepressant mechanisms of puerarin: Anti-inflammatory response via the gut-brain axis

BACKGROUND

Puerarin has been shown to have a good antidepressant effect, and our previous study found that it can remedy stress-induced dysbiosis. However, its gut microbiota-related mechanism has not been fully elucidated. Therefore, this study aimed to investigate the potential link between puerarin on gut microbiota and inflammatory responses in depressed rats.

METHODS

A chronic unpredictable mild stress (CUMS) rat model of depression was established, open field test (OFT), sucrose preference test (SPT) and forced swimming test (FST) were used to evaluate its antidepressant effect. 16S rRNA sequencing was performed to identify the rat fecal microflora. At the same time, inflammatory cytokines, colonic histopathological changes, and brain-derived neurotrophic factor (BDNF), nuclear factor kappa-B (NF-κB), inhibitor a of NF-κB (IκB-α) protein expression were detected.

RESULTS

Puerarin attenuated CUMS-induced depressive-like behavior and gut microbiota dysregulation in rats, significantly reducing the abundance of harmful bacteria such as Desulfovibrio, Verrucomicrobiae, and Verrucomicrobia. In addition, puerarin can also reduce the pro-inflammatory factors and increase the level of anti-inflammatory factors in depressed rats, improve the damaged colon tissue, enhance the expression of BDNF and IκB-α in the hippocampus and inhibit the expression of NF-κB.

LIMITATIONS

Direct evidence that puerarin improves depressive-like behaviors via gut microbiota is lacking.

CONCLUSION

The underlying mechanism of puerarin's antidepressant-like effect is closely related to the bidirectional communication of the microbiota-gut-brain axis by regulating the inflammatory response.

Inhibition of neuronal nitric oxide synthase protects against hippocampal neuronal injuries by increasing neuropeptide Y expression in temporal lobe epilepsy mice

Neuronal nitric oxide synthase (nNOS) plays a pivotal role in the pathological process of neuronal injury in the development of epilepsy. Our previous study has demonstrated that nitric oxide (NO) derived from nNOS in the epileptic brain is neurotoxic due to its reaction with the superoxide radical with the formation of peroxynitrite. Neuropeptide Y (NPY) is widely expressed in the mammalian brain, which has been implicated in energy homeostasis and neuroprotection. Recent studies suggest that nNOS may act as a mediator of NPY signaling. Here in this study, we sought to determine whether NPY expression is regulated by nNOS, and if so, whether the regulation of NPY by nNOS is associated with the neuronal injuries in the hippocampus of epileptic brain. Our results showed that pilocarpine-induced temporal lobe epilepsy (TLE) mice exhibited an increased level of nNOS expression and a decreased level of NPY expression along with hippocampal neuronal injuries and cognition deficit. Genetic deletion of nNOS gene, however, significantly upregulated hippocampal NPY expression and reduced TLE-induced hippocampal neuronal injuries and cognition decline. Knockdown of NPY abolished nNOS depletion-induced neuroprotection and cognitive improvement in the TLE mice, suggesting that inhibition of nNOS protects against hippocampal neuronal injuries by increasing neuropeptide Y expression in TLE mice. Targeting nNOS-NPY signaling pathway in the epileptic brain might provide clinical benefit by attenuating neuronal injuries and preventing cognitive deficits in epilepsy patients.

Alterations in gut microbiota affect behavioral and inflammatory responses to methamphetamine in mice

RATIONALE AND OBJECTIVES

Methamphetamine (METH) is a highly addictive and widely abused drug that causes severe neuroinflammation in the human brain. The gut microbiota has a tremendous impact on the core symptoms of neuropsychiatric disorders via the microbiota-gut-brain (MGB) axis. However, it is not clear whether alterations in the gut microbiota are involved in METH exposure.

METHODS

We established a mouse model with chronic, escalating doses of METH exposure. Intervene in gut microbiota with antibiotics to observe the changes of locomotor activity caused by METH exposure in mice. qPCR and 16S rRNA gene sequencing were used to analyze the gut microbiota profiles. In addition, we tested the levels of inflammatory factors in the nucleus accumbens (NAc), prefrontal cortex (mPFC), hippocampus (HIp), and spleen. Finally, short-chain fatty acids (SCFAs) were supplemented to determine the interaction between behavior changes and the structure of gut microbiota.

RESULTS

In this research, METH increased the locomotor activity of mice, while antibiotics changed the effect. Antibiotics enhanced the expression of pro-inflammatory cytokines in mPFC, HIp, and spleen of METH-exposed mice. METH altered the gut microbiota of mice after antibiotic treatment, such as Butyricicoccus and Roseburia, which are related to butyrate metabolism. Supplementation with SCFAs changed the behavior of METH-exposed mice and decreased Parabacteroides and increased Lactobacillus in METH-exposed mice gut.

CONCLUSIONS

This research showed that antibiotics affected the behavior of METH-exposed mice and promoted inflammation. Our findings suggest that SCFAs might regulate METH-induced gut microbiota changes and behavior.

Impact of a phage cocktail targeting Escherichia coli and Enterococcus faecalis as members of a gut bacterial consortium in vitro and in vivo

Escherichia coli and Enterococcus faecalis have been implicated as important players in human gut health that have been associated with the onset of inflammatory bowel disease (IBD). Bacteriophage (phage) therapy has been used for decades to target pathogens as an alternative to antibiotics, but the ability of phage to shape complex bacterial consortia in the lower gastrointestinal tract is not clearly understood. We administered a cocktail of six phages (either viable or heat-inactivated) targeting pro-inflammatory Escherichia coli LF82 and Enterococcus faecalis OG1RF as members of a defined community in both a continuous fermenter and a murine colitis model. The two target strains were members of a six species simplified human microbiome consortium (SIHUMI-6). In a 72-h continuous fermentation, the phage cocktail caused a 1.1 and 1.5 log (log10 genome copies/mL) reduction in E. faecalis and E. coli numbers, respectively. This interaction was accompanied by changes in the numbers of other SIHUMI-6 members, with an increase of Lactiplantibacillus plantarum (1.7 log) and Faecalibacterium prausnitzii (1.8 log). However, in germ-free mice colonized by the same bacterial consortium, the same phage cocktail administered twice a week over nine weeks did not cause a significant reduction of the target strains. Mice treated with active or inactive phage had similar levels of pro-inflammatory cytokines (IFN-y/IL12p40) in unstimulated colorectal colonic strip cultures. However, histology scores of the murine lower GIT (cecum and distal colon) were lower in the viable phage-treated mice, suggesting that the phage cocktail did influence the functionality of the SIHUMI-6 consortium. For this study, we conclude that the observed potential of phages to reduce host populations in in vitro models did not translate to a similar outcome in an in vivo setting, with this effect likely brought about by the reduction of phage numbers during transit of the mouse GIT.

Differential In Vitro Effects of SGLT2 Inhibitors on Mitochondrial Oxidative Phosphorylation, Glucose Uptake and Cell Metabolism

(1) The cardio-reno-metabolic benefits of the SGLT2 inhibitors canagliflozin (cana), dapagliflozin (dapa), ertugliflozin (ertu), and empagliflozin (empa) have been demonstrated, but it remains unclear whether they exert different off-target effects influencing clinical profiles. (2) We aimed to investigate the effects of SGLT2 inhibitors on mitochondrial function, cellular glucose-uptake (GU), and metabolic pathways in human-umbilical-vein endothelial cells (HUVECs). (3) At 100 µM (supra-pharmacological concentration), cana decreased ECAR by 45% and inhibited GU (IC5o: 14 µM). At 100 µM and 10 µM (pharmacological concentration), cana increased the ADP/ATP ratio, whereas dapa and ertu (3, 10 µM, about 10× the pharmacological concentration) showed no effect. Cana (100 µM) decreased the oxygen consumption rate (OCR) by 60%, while dapa decreased it by 7%, and ertu and empa (all 100 µM) had no significant effect. Cana (100 µM) inhibited GLUT1, but did not significantly affect GLUTs’ expression levels. Cana (100 µM) treatment reduced glycolysis, elevated the amino acids supplying the tricarboxylic-acid cycle, and significantly increased purine/pyrimidine-pathway metabolites, in contrast to dapa (3 µM) and ertu (10 µM). (4) The results confirmed cana´s inhibition of mitochondrial activity and GU at supra-pharmacological and pharmacological concentrations, whereas the dapa, ertu, and empa did not show effects even at supra-pharmacological concentrations. At supra-pharmacological concentrations, cana (but not dapa or ertu) affected multiple cellular pathways and inhibited GLUT1.

Do common antibiotic treatments influence emotional processing?

Antibiotics are among the most commonly prescribed medications worldwide, yet research in recent years has revealed the detrimental effect they can have on the human microbiome, with implications for health. The community of microorganisms inhabiting the gut has been shown to regulate physiological and neural processes. Since studies in both humans and animal models have revealed that the gut microbiome can affect the brain, influencing emotion and cognition, here we investigate whether antibiotic treatment is associated with changes in emotional processing and mood with a between-subject design in 105 young healthy adult volunteers, using both psychological tests and questionnaires. As both the immune system and vagal signalling can mediate the microbiome-gut-brain axis, we also assess whether there is any evidence of such changes in participant physiology. We find that individuals who have taken antibiotics in the past three months show a stronger emotional bias towards sadness and at a physiological level they have a higher heart rate (though this does not mediate the relationship with negative bias). While we cannot rule out a possible role of prior infection, our findings are in any case highly relevant in light of research revealing that antibiotics are linked to increased susceptibility to depression and anxiety. Our results also have implications for listing antibiotic use as an exclusion criterion in studies on emotional processing and psychophysiology.

Evaluating the Potential and Synergetic Effects of Microcins against Multidrug-Resistant Enterobacteriaceae

The advent of multidrug-resistant bacteria has hampered the development of new antibiotics, exacerbating their morbidity and mortality. In this context, the gastrointestinal tract reveals a valuable source of novel antimicrobials. Microcins are bacteriocins produced by members of the family Enterobacteriaceae, which are endowed with a wide diversity of structures and mechanisms of action, and exert potent antibacterial activity against closely related bacteria. In this study, we investigated the antibacterial activities of four microcins against 54 Enterobacteriaceae isolates from three species (Escherichia coli, Klebsiella pneumoniae, and Salmonella enterica). The selected microcins, microcin C (McC, nucleotide peptide), microcin J25 (MccJ25, lasso peptide), microcin B17 (MccB17, linear azol(in)e-containing peptide), and microcin E492 (MccE492, siderophore peptide) carry different post-translational modifications and have distinct mechanisms of action. MICs and minimal bactericidal concentrations (MBC) of the microcins were measured and the efficacy of combinations of the microcins together or with antibiotics was assessed to identify potential synergies. Every isolate showed sensitivity to at least one microcin with MIC values ranging between 0.02 μM and 42.5 μM. Among the microcins tested, McC exhibited the broadest spectrum of inhibition with 46 strains inhibited, closely followed by MccE492 with 38 strains inhibited, while MccJ25 showed the highest activity. In general, microcin activity was observed to be independent of antibiotic resistance profile and strain genus. Of the 42 tested combinations, 20 provided enhanced activity (18 out of 20 being microcin-antibiotic combinations), with two being synergetic. IMPORTANCE With their wide range of structures and mechanisms of action, microcins are shown to exert antibacterial activities against Enterobacteriaceae resistant to antibiotics together with synergies with antibiotics and in particular colistin.

Heat-inactivated Lacticaseibacillus paracasei N1115 alleviates the damage due to brain function caused by long-term antibiotic cocktail exposure in mice

Critical development period of intestinal microbiota occurs concurrently with brain development, and their interaction is influenced by the microbiota–gut–brain axis. This study examined how antibiotics exposure affected gut microbiota and brain development and analyzed the possible benefits of heat-inactivated Lacticaseibacillus paracasei N1115 (N1115). Thirty neonatal male mice were randomly divided into three groups and treated with sterilized water (control), an antibiotic cocktail (Abx), or antibiotics plus heat-inactivated N1115 (Abx + N1115) for 84 days. We found that while the mRNA levels of GABA_Aα1, GABA_b1, and glucocorticoid receptor (GR) in the hippocampus and brain-derived neurotrophic factor (BDNF), GABA_Aα1, GABA_b1, and nerve growth factor (NGF) in the prefrontal cortex were higher, the mRNA levels of 5-HT_1A were lower in the Abx group. The Abx + N1115 group had lower mRNA levels of GABA_Aα1, GABA_b1, and GR in the hippocampus and BDNF, GABA_b1, and NGF in the prefrontal cortex than the Abx group. The latency period was longer in the Morris water maze test while longer rest time was seen in tail suspension test in the Abx group than the control and Abx + N1115 groups. In the open field test, the moving time and distance of the Abx group were reduced. Further, the alpha-diversity indexes of the Abx and Abx + N1115 groups were significantly lower than the control. Further, long-term exposure to antibiotics disrupted the intestinal microbiota as evidenced by decreased Bacteroides, Firmicutes, and Lactobacillus, and increased Proteobacteria and Citrobacter. However, N1115 significantly decreased the abundance of Citrobacter when compared with those in the Abx group. These results indicate that antibiotics can substantially damage the intestinal microbiota and cognitive function, causing anxiety and depression, which can be alleviated by heat-inactivated N1115 via modulation of the microbiota–gut–brain axis.

Impact of Intestinal Microbiota on Cognitive Flexibility by a Novel Touch Screen Operant System Task in Mice

Cognitive flexibility is the ability to rapidly adapt to a constantly changing environment. It is impaired by aging as well as in various neurological diseases, including dementia and mild cognitive impairment. In rodents, although many behavioral test protocols have been reported to assess learning and memory dysfunction, few protocols address cognitive flexibility. In this study, we developed a novel cognitive flexibility test protocol using touch screen operant system. This test comprises a behavioral sequencing task, in which mice are required to discriminate between the “rewarded” and “never-rewarded” spots and shuttle between the two distantly positioned rewarded spots, and serial reversals, in which the diagonal spatial patterns of rewarded and never-rewarded spots were reversely changed repetitively. Using this test protocol, we demonstrated that dysbiosis treated using streptomycin induces a decline in cognitive flexibility, including perseveration and persistence. The relative abundances of Firmicutes and Bacteroides were lower and higher, respectively, in the streptomycin-treated mice with less cognitive flexibility than in the control mice. This is the first report to directly show that intestinal microbiota affects cognitive flexibility.

Microbial-derived metabolites as a risk factor of age-related cognitive decline and dementia

A consequence of our progressively ageing global population is the increasing prevalence of worldwide age-related cognitive decline and dementia. In the absence of effective therapeutic interventions, identifying risk factors associated with cognitive decline becomes increasingly vital. Novel perspectives suggest that a dynamic bidirectional communication system between the gut, its microbiome, and the central nervous system, commonly referred to as the microbiota-gut-brain axis, may be a contributing factor for cognitive health and disease. However, the exact mechanisms remain undefined. Microbial-derived metabolites produced in the gut can cross the intestinal epithelial barrier, enter systemic circulation and trigger physiological responses both directly and indirectly affecting the central nervous system and its functions. Dysregulation of this system (i.e., dysbiosis) can modulate cytotoxic metabolite production, promote neuroinflammation and negatively impact cognition. In this review, we explore critical connections between microbial-derived metabolites (secondary bile acids, trimethylamine-N-oxide (TMAO), tryptophan derivatives and others) and their influence upon cognitive function and neurodegenerative disorders, with a particular interest in their less-explored role as risk factors of cognitive decline.

Gut Microbial Dysbiosis and Cognitive Impairment in Bipolar Disorder: Current Evidence

Recent studies have reported that the gut microbiota influences mood and cognitive function through the gut-brain axis, which is involved in the pathophysiology of neurocognitive and mental disorders, including Parkinson’s disease, Alzheimer’s disease, and schizophrenia. These disorders have similar pathophysiology to that of cognitive dysfunction in bipolar disorder (BD), including neuroinflammation and dysregulation of various neurotransmitters (i.e., serotonin and dopamine). There is also emerging evidence of alterations in the gut microbial composition of patients with BD, suggesting that gut microbial dysbiosis contributes to disease progression and cognitive impairment in BD. Therefore, microbiota-centered treatment might be an effective adjuvant therapy for BD-related cognitive impairment. Given that studies focusing on connections between the gut microbiota and BD-related cognitive impairment are lagging behind those on other neurocognitive disorders, this review sought to explore the potential mechanisms of how gut microbial dysbiosis affects cognitive function in BD and identify potential microbiota-centered treatment.

Moving beyond descriptive studies: harnessing metabolomics to elucidate the molecular mechanisms underpinning host-microbiome phenotypes

Advances in technology and software have radically expanded the scope of metabolomics studies and allow us to monitor a broad transect of central carbon metabolism in routine studies. These increasingly sophisticated tools have shown that many human diseases are modulated by microbial metabolism. Despite this, it remains surprisingly difficult to move beyond these statistical associations and identify the specific molecular mechanisms that link dysbiosis to the progression of human disease. This difficulty stems from both the biological intricacies of host-microbiome dynamics as well as the analytical complexities inherent to microbiome metabolism research. The primary objective of this review is to examine the experimental and computational tools that can provide insights into the molecular mechanisms at work in host-microbiome interactions and to highlight the undeveloped frontiers that are currently holding back microbiome research from fully leveraging the benefits of modern metabolomics.

Evaluation of fecal microbiota and its correlation with inflammatory, hormonal, and nutritional profiles in women

The present study evaluated the gut microbiota profiles of 40 women and correlated them with their nutritional, inflammatory, and hormonal profiles. Stool and blood samples were collected, and anthropometric measurements were obtained from 20 women diagnosed with obesity ("case" group) and 20 women with weight in the normal range ("control" group). Bacteria belonging to two phyla, Firmicutes and Bacteroidetes, one class, Mollicutes, and four genera were evaluated by real-time polymerase chain reaction. Levels of 18 inflammatory cytokines were measured using the Luminex assay, and ghrelin and leptin levels were measured using enzymatic immunoadsorption assay. Mollicutes proportion differed significantly between the case and control groups, and a significant positive association was detected between the presence of Mollicutes and obesity. Statistically significant differences were observed between the proportions of Firmicutes and Bacteroidetes in the two groups, with a higher proportion of Firmicutes/Bacteroidetes ratio among the gut microbiota of women in the case group compared to those of the control group. Higher counts of Escherichia coli and Clostridium spp. were observed in the control group than in the case group, whereas higher counts of Lactobacillus spp. and Bacteroides spp. were detected in the case group than in the control group. There was a positive correlation between interleukin-6 (IL-6) and interferon-γ (IFN-γ) levels and the anthropometric variables and a negative correlation between IL-10 and these variables. Leptin and ghrelin concentrations differed significantly between the two groups and showed positive and negative correlation with obesity predictors, respectively. Therefore, gut microbiota was associated with obesity in women from this study group. Moreover, this microbiota was associated with inflammatory profiles and alterations in ghrelin and leptin levels.

Oligosaccharide and Flavanoid Mediated Prebiotic Interventions to Treat Gut Dysbiosis Associated Cognitive Decline

Oligosaccharides are potential prebiotic which maintains gut microbiota and improves gut health. The association of gut and brain is named as gut-brain-axis. Gut dysbiosis disrupts gut-brain-axis and effectively contributes to psychiatric disorders. In the present study, Xylo-oligosaccharide (XOS) and Quercetin were used as therapeutic interventions against gut dysbiosis mediated cognitive decline. Gut dysbiosis was established in mice through administration of Ampicillin Sodium, orally for 14 days. XOS and quercetin were administered separately or in combination along with antibiotic. Gene expression studies using mice faecal samples showed both XOS and quercetin could revive Lactobacillus, Bifidobacterium, Firmicutes and Clostridium which were reduced due to antibiotic treatment. FITC-dextran concentration in serum revealed XOS and quercetin protected intestinal barrier integrity against antibiotic associated damage. This was verified by histopathological studies showing restored intestinal architecture. Moreover, intestinal inflammation which increased after antibiotic treated animals was reduced upon XOS and quercetin treatment. Behavioural studies demonstrated that gut dysbiosis reduced fear conditioning, spatial and recognition memory which were reversed upon XOS and quercetin treatment. XOS and quercetin also reduced inflammation and acetylcholine esterase which were heightened in antibiotic treated animal brain. They also reduced oxidative stress, pro-inflammatory cytokines and chemokines and protected hippocampal neurons. In conclusion, XOS and quercetin effectively reduced antibiotic associated gut dysbiosis and prevented gut dysbiosis associated cognitive decline in mice.

Obesity and the Brain

Innate and adaptive immunity are essential for neurodevelopment and central nervous system (CNS) homeostasis; however, the fragile equilibrium between immune and brain cells can be disturbed by any immune dysregulation and cause detrimental effects. Accumulating evidence indicates that, despite the blood-brain barrier (BBB), overactivation of the immune system leads to brain vulnerability that increases the risk of neuropsychiatric disorders, particularly upon subsequent exposure later in life. Disruption of microglial function in later life can be triggered by various environmental and psychological factors, including obesity-driven chronic low-grade inflammation and gut dysbiosis. Increased visceral adiposity has been recognized as an important risk factor for multiple neuropsychiatric conditions. The review aims to present our current understanding of the topic.

Antibiotic cocktail-induced gut microbiota depletion in different stages could cause host cognitive impairment and emotional disorders in adulthood in different manners

Gut microbiota depletion may result in cognitive impairment and emotional disorder. This study aimed to determine the possible association between host gut microbiota, cognitive function, and emotion in various life stages and its related underlying mechanisms. Seventy-five neonatal mice were randomly divided into five groups (n = 15 per group). Mice in the vehicle group were administered distilled water from birth to death, and those in the last four groups were administered antibiotic cocktail from birth to death, from birth to postnatal day (PND) 21 (infancy), from PND 21 to 56 (adolescence), and from PND 57 to 84 (adulthood), respectively. Antibiotic exposure consistently altered the gut microbiota composition and decreased the diversity of gut microbiota. Proteobacteria were the predominant bacteria instead of Firmicutes and Bacteroidetes after antibiotic exposure in different life stages. Long-term and infant gut microbiota depletion resulted in anxiety- and depression-like behaviors, memory impairments, and increased expression of γ-aminobutyric acid type A receptor α1 of adult mice. Long-term antibiotic exposure also significantly decreased serum interleukin (IL)-1β, IL-10, and corticosterone of adult mice. Gut microbiota depletion in adolescence resulted in anxiety-like behaviors, short-term memory decline, decreased serum interferon-γ (IFN-γ), mRNA expression of 5-hydroxytryptamine receptor 1A, and neuropeptide Y receptor Y2 in the prefrontal cortex of adult mice. Antibiotic exposure in adulthood damaged short-term memory and decreased serum IL-10, IFN-γ, and increased γ-aminobutyric acid type B receptor 1 mRNA expression of adult mice. These results suggest that antibiotic-induced gut microbiota depletion in the long term and infancy resulted in the most severe cognitive and emotional disorders followed by depletion in adolescence and adulthood. These results also suggest that gut microbes could influence host cognitive function and emotion in a life stage-dependent manner by affecting the function of the immune system, hypothalamic-pituitary-adrenal axis, and the expression of neurochemicals in the brain.

Pediatric neuropsychiatric syndromes associated with infection and microbiome alterations: clinical findings, possible role of the mucosal epithelium, and strategies for the development of new animal models

INTRODUCTION

: Subsets of pediatric obsessive-compulsive disorder (OCD) and autism spectrum disorder (ASD) respectively have been associated with respiratory tract infections and alterations in the intestinal microbiome. Pediatric Acute-onset Neuropsychiatric Syndromes (PANS) refers to the sudden onset of neuropsychiatric symptoms that are triggered by several different infectious and non-infectious factors. Clinical studies and animal modeling are consistent with the proposal that inflammation plays an important etiological role in PANS, as well as in ASD associated with gut dysbiosis.

AREAS COVERED

The authors provide an overview of clinical studies of PANS and ASD associated with gastrointestinal symptoms, as well as the current strategies for studying these syndromes in rodent models. Finally, the authors highlight similarities between these syndromes that may provide clues to common etiological mechanisms.

EXPERT OPINION

Although data from existing animal models are consistent with an important role for anti-neuronal antibodies in PANS triggered by GAS infection, we lack models for identifying pathophysiological mechanisms of PANS associated with other infectious and non-infectious triggers. The authors propose a strategy for developing such models that incorporates known vulnerability and triggering factors for PANS into the modeling process. This novel strategy should expand our understanding of the pathophysiology of PANS, as well as facilitate the development of new pharmacological treatments for PANS and related syndromes.

Antibiotic-induced microbiome depletion remodels daily metabolic cycles in the brain

The gut microbiome influences cognition and behavior in mammals, yet its metabolic impact on the brain is only starting to be defined. Using metabolite profiling of antibiotics-treated mice, we reveal the microbiome as a key input controlling circadian metabolic cycles in the brain. Intra and inter-region analyses characterise the influence of the microbiome on the suprachiasmatic nucleus, containing the central clockwork, as well as the hippocampus and cortex, regions involved in learning and behavior.

Antibiotic Treatment during Pregnancy Alters Offspring Gut Microbiota in a Sex-Dependent Manner

This study investigated the effect of antibiotics administered to pregnant dams on offspring gut microbiome composition and metabolic capabilities, and how these changes in the microbiota may influence their immune responses in both the periphery and the brain. We orally administered a broad-spectrum antibiotic (ABX) cocktail consisting of vancomycin 0.5 mg/mL, ampicillin 1 mg/mL, and neomycin 1 mg/mL to pregnant dams during late gestation through birth. Bacterial DNA was extracted from offspring fecal samples, and 16S ribosomal RNA gene was sequenced by Illumina, followed by analysis of gut microbiota composition and PICRUSt prediction. Serum and brain tissue cytokine levels were analyzed by Luminex. Our results indicate that the ABX-cocktail led to significant diversity and taxonomic changes to the offspring's gut microbiome. In addition, the predicted KEGG and MetaCyc pathways were significantly altered in the offspring. Finally, there were decreased innate inflammatory cytokines and chemokines and interleukin (IL)-17 seen in the brains of ABX-cocktail offspring in response to lipopolysaccharide (LPS) immune challenge. Our results suggest that maternal ABX can produce long-lasting effects on the gut microbiome and neuroimmune responses of offspring. These findings support the role of the early microbiome in the development of offspring gastrointestinal and immune systems.

Gut Microbiota as a Hidden Player in the Pathogenesis of Alzheimer's Disease

Alzheimer's disease (AD), the most common neurodegenerative disorder, is accompanied by cognitive impairment and shows representative pathological features, including senile plaques and neurofibrillary tangles in the brain. Recent evidence suggests that several systemic changes outside the brain are associated with AD and may contribute to its pathogenesis. Among the factors that induce systemic changes in AD, the gut microbiota is increasingly drawing attention. Modulation of gut microbiome, along with continuous attempts to remove pathogenic proteins directly from the brain, is a viable strategy to cure AD. Seeking a holistic understanding of the pathways throughout the body that can affect the pathogenesis, rather than regarding AD solely as a brain disease, may be key to successful therapy. In this review, we focus on the role of the gut microbiota in causing systemic manifestations of AD. The review integrates recently emerging concepts and provides potential mechanisms about the involvement of the gut-brain axis in AD, ranging from gut permeability and inflammation to bacterial translocation and cross-seeding.

Association of midlife antibiotic use with subsequent cognitive function in women

The gut microbiome is increasingly recognized to play a role in cognition and dementia. Antibiotic use impacts the gut microbiome and has been linked with chronic disease. Despite these data, there is no evidence supporting an association between long-term antibiotic use in adults and cognitive function. We conducted a prospective population-based cohort study among 14,542 participants in the Nurses’ Health Study II who completed a self-administered computerized neuropsychological test battery between 2014–2018. Multivariate linear regression models were used to assess if chronic antibiotic use in midlife was associated with cognitive impairment assessed later in life. Women who reported at least 2 months of antibiotic exposure in midlife (mean age 54.7, SD 4.6) had lower mean cognitive scores seven years later, after adjustment for age and educational attainment of the spouse and parent, with a mean difference of -0.11 standard units for the global composite score (P_trend <0.0001), -0.13 for a composite score of psychomotor speed and attention (P_trend <0.0001), and -0.10 for a composite score of learning and working memory (P_trend <0.0001) compared with non-antibiotic users. These differences were not materially changed after multivariate adjustment for additional risk factors, including comorbid conditions. As a benchmark, the mean difference in score associated with each additional year of age was (-0.03) for global cognition, (-0.04) for psychomotor speed and attention, and (-0.03) for learning and working memory; thus the relation of antibiotic use to cognition was roughly equivalent to that found for three to four years of aging. Long-term antibiotic use in midlife is associated with small decreases in cognition assessed seven years later. These data underscore the importance of antibiotic stewardship, especially among aging populations.

Guts Imbalance Imbalances the Brain: A Review of Gut Microbiota Association With Neurological and Psychiatric Disorders

Over the last 10 years, there has been a growing interest in the relationship between gut microbiota, the brain, and neurologic-associated affections. As multiple preclinical and clinical research studies highlight gut microbiota’s potential to modulate the general state of health state, it goes without saying that gut microbiota plays a significant role in neurogenesis, mental and cognitive development, emotions, and behaviors, and in the progression of neuropsychiatric illnesses. Gut microbiota produces important biologic products that, through the gut-brain axis, are directly connected with the appearance and evolution of neurological and psychiatric disorders such as depression, anxiety, bipolar disorder, autism, schizophrenia, Parkinson’s disease, Alzheimer’s disease, dementia, multiple sclerosis, and epilepsy. This study reviews recent research on the link between gut microbiota and the brain, and microbiome’s role in shaping the development of the most common neurological and psychiatric illnesses. Moreover, special attention is paid to the use of probiotic formulations as a potential non-invasive therapeutic opportunity for prevention and management of neuropsychiatric-associated affections.

The Effect of a Probiotic Complex on the Gut-Brain Axis: A Translational Study

BACKGROUND

The gut-brain axis refers to the network of connections that involve multiple biologic systems, allowing bidirectional communication between the gut and the brain. This communication is mainly mediated by gut microbiota, thanks to its ability to modulate several processes like the production of neurotransmitters. As such, keeping a balanced gut microbiota through probiotic intake could be a valid solution in supporting the right gut-brain communications.

METHODS

A two-step in vitro screening of five different probiotic strains was carried out to select the best performers in the modulation of stress markers. A first selection on SK-N-DZ neuronal cell lines was performed to evaluate the inhibition of the epigenetic enzyme LSD1, promotion of GABA, and expression of serotonin. Three out of five strains were tested for their ability to promote serotonin synthesis in the Caco2 cell line. As a result, Limosilactobacillus reuteri PBS072 and Bifidobacterium breve BB077 were selected as the best performing strains. To confirm their effects in humans, a proof-of-concept trial was carried out to evaluate stress-related parameters for 28 days of product intake in a group of 30 stressed students.

RESULTS

A significant improvement of cognitive functions, in terms of short-term memory, attention, and executive performance, as well as of psychophysiological markers, such as salivary cortisol level, skin conductance, sleep quality, and anxiety, were observed.

CONCLUSIONS

According to the results, L. reuteri PBS072 and B. breve BB077 are potential probiotic candidates for improving stress resilience, cognitive functions, and sleep quality.

Mapping the Influence of the Gut Microbiota on Small Molecules across the Microbiome Gut Brain Axis

Microbes exert influence across the microbiome-gut-brain axis through neurotransmitter production, induction of host immunomodulators, or the release or induction of other microbial or host molecules. Here, we used mass spectrometry imaging (MSI), a label-free imaging tool, to map molecular changes in the gut and brain in germ-free, antibiotic-treated and control mice. We determined spatial distribution and relative quantification of neurotransmitters and their precursors in response to the microbiome. Using untargeted MSI, we detected a significant change in the levels of four identified small molecules in the brains of germ-free animals compared to controls. However, antibiotic treatment induced no significant changes in these same metabolites in the brain after 1 week of treatment. This work exemplifies the utility of MSI as a tool for the study of known and discovery of novel, mediators of microbiome-gut-brain axis communication.

Xanthoceraside exerts anti-Alzheimer's disease effect by remodeling gut microbiota and modulating microbial-derived metabolites level in rats

BACKGROUND

Microbial-derived metabolites play important roles in Alzheimer's disease (AD) pathology, yet how intestinal microbes influence AD progression remains uncertain. Xanthoceraside (XAN), a triterpenoid saponin with anti-AD activity, was extracted from the husks of Xanthoceras sorbifolia Bunge. However, it is still unclear that how XAN modulates the gut microbiota community to regulate AD progression through changing the levels of microbial-derived metabolites.

PURPOSE

In this study, we investigated the mechanism underlying the anti-AD effect of XAN.

METHODS

The current combination studies of multiple-targeted metabolomics, natural product chemistry and pharmacology revealed that oral XAN mediated intestinal microbiota to ameliorate Aβ1-42-induced learning and memory deficits in rats, which were confirmed through antibiotic treatments and fecal microbiota transplantation.

RESULTS

As a poor water solubility and low permeability compound that hardly be absorbed into blood-brain barrier, XAN significantly regulated Aβ1-42-induced metabolism disorders directly or indirectly in gut, including neurotransmitters, amino acids, bile acids and SCFAs metabolism that were detected by UHPLC-MS/MS and GC-MS/MS. In particularly, the in vitro evaluation of XAN on SCFAs production not only found a striking increase in the production of SCFAs after fermentation, but revealed the inner relationship among XAN, gut microbiota and SCFAs in vivo. All results demonstrated that XAN could improve AD rats' learning and memory deficits by modulating the community of gut microbiota which was connected through 16S rRNA sequencing and CCA analyses.

CONCLUSIONS

Our study provided a novel mechanism for developing XAN as a potential anti-AD drug and revealed that the gut microbiota might be a potential target for AD treatment .

Novel probiotic treatment of autism spectrum disorder associated social behavioral symptoms in two rodent models

The prevalence of autism spectrum disorder (ASD) has rapidly increased in the past decades, and several studies report about the escalating use of antibiotics and the consequent disruption of the gastrointestinal microbiome leading to the development of neurobehavioral symptoms resembling to those of ASD. The primary purpose of this study was to investigate whether depletion of the gastrointestinal microbiome via antibiotics treatment could induce ASD-like behavioral symptoms in adulthood. To reliably evaluate that, validated valproic acid (VPA) ASD animal model was introduced. At last, we intended to demonstrate the assessed potential benefits of a probiotic mixture (PM) developed by our research team. Male Wistar rats were used to create antibiotics treated; antibiotics and PM treated; PM treated, VPA treated; VPA and PM treated; and control groups. In all investigations we focused on social behavioral disturbances. Antibiotics-induced microbiome alterations during adulthood triggered severe deficits in social behavior similar to those observed in the VPA model. Furthermore, it is highlighted that our PM proved to attenuate both the antibiotics- and the VPA-generated antisocial behavioral symptoms. The present findings underline potential capacity of our PM to improve social behavioral alterations thus, indicate its promising therapeutic power to attenuate the social-affective disturbances of ASD.

A Gut Instinct on Leukaemia: A New Mechanistic Hypothesis for Microbiota-Immune Crosstalk in Disease Progression and Relapse

Despite significant advances in the treatment of Chronic Myeloid and Acute Lymphoblastic Leukaemia (CML and ALL, respectively), disease progression and relapse remain a major problem. Growing evidence indicates the loss of immune surveillance of residual leukaemic cells as one of the main contributors to disease recurrence and relapse. More recently, there was an appreciation for how the host’s gut microbiota predisposes to relapse given its potent immunomodulatory capacity. This is especially compelling in haematological malignancies where changes in the gut microbiota have been identified after treatment, persisting in some patients for years after the completion of treatment. In this hypothesis-generating review, we discuss the interaction between the gut microbiota and treatment responses, and its capacity to influence the risk of relapse in both CML and ALL We hypothesize that the gut microbiota contributes to the creation of an immunosuppressive microenvironment, which promotes tumour progression and relapse.

The Effect of Long-Term or Repeated Use of Antibiotics in Children and Adolescents on Cognitive Impairment in Middle-Aged and Older Person(s) Adults: A Cohort Study

Objectives

We evaluated the effects of long-term/recurrent use of antibiotics in childhood on developing cognitive impairment in middle and old age from UK Biobank Database.

Methods

UK Biobank recruited participants aged 37-73 years. Cognitive impairment was ascertained by fluid intelligence questionnaire. Primary outcome was the occurrence of cognitive impairment in middle and old age. Multivariate logistic regression models were used to explore the relationship between long-term/recurrent use of antibiotics and cognitive impairment.

Results

Over 3.8-10.8 years' follow-up, 4,781 of the 35,921 participants developed cognitive impairment. The odds of cognitive impairment in middle and old age among long-term/recurrent use of antibiotics in childhood were increased by 18% compared with their counterparts (adjusted odd ratio 1.18, 95% confidence interval 1.08-1.29, p < 0.01). The effect of long-term/recurrent use of antibiotics in childhood on cognitive impairment was homogeneous across different categories of various subgroup variables such as sex, age, APOE4, ethnic groups, income before tax, smoking status, alcohol status, BMI, hypertension and diabetes but the effect of long-term/recurrent use of antibiotics in childhood was modified by the educational qualification (p-value for interaction <0.05).

Conclusion

Long-term/recurrent use of antibiotics in childhood may increase the risk of cognitive impairment in middle and old age.

Exogenous lipase administration alters gut microbiota composition and ameliorates Alzheimer's disease-like pathology in APP/PS1 mice

Alzheimer's disease (AD) represents the most common form of dementia in the elderly with no available disease modifying treatments. Altered gut microbial composition has been widely acknowledged as a common feature of AD, which potentially contributes to progression or onset of AD. To assess the hypothesis that Candida rugosa lipase (CRL), which has been shown to enhance gut microbiome and metabolite composition, can rebalance the gut microbiome composition and reduce AD pathology, the treatment effects in APPswe/PS1de9 (APP/PS1) mice were investigated. The analysis revealed an increased abundance of Acetatifactor and Clostridiales vadin BB60 genera in the gut; increased lipid hydrolysis in the gut lumen, normalization of peripheral unsaturated fatty acids, and reduction of neuroinflammation and memory deficits post treatment. Finally, we demonstrated that the evoked benefits on memory could be transferred via fecal matter transplant (FMT) into antibiotic-induced microbiome-depleted (AIMD) wildtype mice, ameliorating their memory deficits. The findings herein contributed to improve our understanding of the role of the gut microbiome in AD's complex networks and suggested that targeted modification of the gut could contribute to amelioration of AD neuropathology.

Insights into the Composition of a Co-Culture of 10 Probiotic Strains (OMNi BiOTiC® AAD10) and Effects of Its Postbiotic Culture Supernatant

BACKGROUND

We aimed to gain insights in a co-culture of 10 bacteria and their postbiotic supernatant.

METHODS

Abundances and gene expression were monitored by shotgun analysis. The supernatant was characterized by liquid chromatography mass spectroscopy (LC-MS) and gas chromatography mass spectroscopy (GC-MS). Supernatant was harvested after 48 h (S48) and 196 h (S196). Susceptibility testing included nine bacteria and C. albicans. Bagg albino (BALBc) mice were fed with supernatant or culture medium. Fecal samples were obtained for 16S analysis.

RESULTS

A time-dependent decrease of the relative abundances and gene expression of L. salivarius, L. paracasei, E. faecium and B. longum/lactis and an increase of L. plantarum were observed. Substances in LC-MS were predominantly allocated to groups amino acids/peptides/metabolites and nucleotides/metabolites, relating to gene expression. Fumaric, panthotenic, 9,3-methyl-2-oxovaleric, malic and aspartic acid, cytidine monophosphate, orotidine, phosphoserine, creatine, tryptophan correlated to culture time. Supernatant had no effect against anaerobic bacteria. S48 was reactive against S. epidermidis, L. monocytogenes, P. aeruginosae, E. faecium and C. albicans. S196 against S. epidermidis and Str. agalactiae. In vivo S48/S196 had no effect on alpha/beta diversity. Linear discriminant analysis effect size (LEfSe) and analysis of composition of microbiomes (ANCOM) revealed an increase of Anaeroplasma and Faecalibacterium prausnitzii.

CONCLUSIONS

The postbiotic supernatant had positive antibacterial and antifungal effects in vitro and promoted the growth of distinct bacteria in vivo.

No guts about it: captivity, but not neophobia phenotype, influences the cloacal microbiome of house sparrows (Passer domesticus)

Behavioral traits such as anxiety and depression have been linked to diversity of the gut microbiome in humans, domesticated animals, and lab-bred model species, but the extent to which this link exists in wild animals, and thus its ecological relevance, is poorly understood. We examined the relationship between a behavioral trait (neophobia) and the cloacal microbiome in wild house sparrows (Passer domesticus,n = 22) to determine whether gut microbial diversity is related to personality in a wild animal. We swabbed the cloaca immediately upon capture, assessed neophobia phenotypes in the lab, and then swabbed the cloaca again after several weeks in captivity to additionally test whether the microbiome of different personality types is affected disparately by captivity, and characterized gut microbiomes using 16S rRNA gene amplicon sequencing. We did not detect differences in cloacal alpha or beta microbial diversity between neophobic and non-neophobic house sparrows, and diversity for both phenotypes was negatively impacted by captivity. Although our results suggest that the adult cloacal microbiome and neophobia are not strongly linked in wild sparrows, we did detect specific OTUs that appeared more frequently and at higher abundances in neophobic sparrows, suggesting that links between the gut microbiome and behavior may occur at the level of specific taxa. Further investigations of personality and the gut microbiome are needed in more wild species to reveal how the microbiome-gut-brain axis and behavior interact in an ecological context.

Establishment and evaluation of a specific antibiotic-induced inflammatory bowel disease model in rats

Physical and chemical methods for generating rat models of enteritis have been established; however, antibiotic induction has rarely been used for this purpose. The present study aimed to establish and evaluate a rat model of inflammatory bowel disease (IBD) using antibiotics. A total of 84 Sprague-Dawley (SD) rats were divided into the following groups, according to the dosage and method of administration of the antibiotics: A, control; B, low-dose clindamycin; C, medium-dose clindamycin; D, high-dose clindamycin; E, low-dose clindamycin, ampicillin and streptomycin; F, medium-dose clindamycin, ampicillin and streptomycin; and G, high-dose clindamycin, ampicillin and streptomycin. Antibiotic administration was stopped on day 7; the modeling period covered days 1-7, and the recovery period covered days 8-15. Half of the animals were dissected on day 11, with the remaining animals dissected on day 15. Food and water intake, body weight and fecal weight were recorded. Intestinal flora was analyzed via microbial culture and quantitative PCR. The content of TNF-α, IL1-β, IL-6 and C-reactive protein (CRP) was assessed in abdominal aorta blood. Colonic and rectal tissues were examined pathologically via hematoxylin-eosin staining to assess leukocyte infiltration and intestinal mucosal changes as indicators of inflammation. Rat weight, food intake, water intake and 2-h fecal weight were significantly different across the experimental groups (P = 0.040, P = 0.016, P<0.001 and P = 0.009, respectively). Microbial cultures revealed no significant differences between group A and B,C (P = 0.546,0.872) but significant differences betwenn group A and the other experimental groups (all P<0.001). Furthermore, significant differences in the levels of Bacteroides, Faecalibacterium prausnitzii and Dialister invisus on day 4 between groups A, C and F (P = 0.033, P = 0.025 and P = 0.034, respectively). Significant differences were detected in the levels of TNF-α, IL1-β, IL-6 and CRP between the groups (all P<0.001). The colonic and rectal pathological inflammation scores of the experimental groups were significantly different compared with group A (B vs. A, P = 0.002; others, all P<0.001). These findings indicated that an antibiotic-induced IBD model was successfully established in SD rats; this animal model may serve as a useful model for clinical IBD research.

Interaction Between Diet and Microbiota in the Pathophysiology of Alzheimer's Disease: Focus on Polyphenols and Dietary Fibers

Animal studies increasingly indicate that the gut microbiota composition and function can be involved in the pathophysiology and progression of Alzheimer's disease (AD) at multiple levels. However, few studies have investigated this putative gut-brain axis in human beings, and none of them considered diet as a determinant of intestinal microbiota composition. Epidemiological studies highlight that a high intake of fruit and vegetables, such as that typical of the Mediterranean diet, can modulate AD progression. Thus, nutritional interventions are being increasingly studied as a possible non-pharmacological strategy to slow down the progression of AD. In particular, polyphenols and fibers represent the nutritional compounds with the higher potential of counterbalancing the pathophysiological mechanisms of dementia due to their antioxidant, anti-inflammatory, and anti-apoptotic properties. These actions are mediated by the gut microbiota, that can transform polyphenols and fibers into biologically active compounds including, among others, phenyl-γ-valerolactones, urolithins, butyrate, and other short-chain fatty acids. In this review, the complex mechanisms linking nutrition, gut microbiota composition, and pathophysiology of cognitive decline in AD are discussed, with a particular focus on the role of polyphenols and fibers. The gaps between pre-clinical and clinical studies are particularly emphasized, as well as the urgent need for studies comprehensively evaluating the link between nutrition, microbiome, and clinical aspects of AD.

Establishment and characterization of stable, diverse, fecal-derived in vitro microbial communities that model the intestinal microbiota

Efforts to probe the role of the gut microbiota in disease would benefit from a system in which patient-derived bacterial communities can be studied at scale. We addressed this by validating a strategy to propagate phylogenetically complex, diverse, stable, and highly reproducible stool-derived communities in vitro. We generated hundreds of in vitro communities cultured from diverse stool samples in various media; certain media generally preserved inoculum composition, and inocula from different subjects yielded source-specific community compositions. Upon colonization of germ-free mice, community composition was maintained, and the host proteome resembled the host from which the community was derived. Treatment with ciprofloxacin in vivo increased susceptibility to Salmonella invasion in vitro, and the in vitro response to ciprofloxacin was predictive of compositional changes observed in vivo, including the resilience and sensitivity of each Bacteroides species. These findings demonstrate that stool-derived in vitro communities can serve as a powerful system for microbiota research.

Upper-limit agricultural dietary exposure to streptomycin in the laboratory reduces learning and foraging in bumblebees

In the past decade, the broadcast-spray application of antibiotics in US crops has increased exponentially in response to bacterial crop pathogens, but little is known about the sublethal impacts on beneficial organisms in agroecosystems. This is concerning given the key roles that microbes play in modulating insect fitness. A growing body of evidence suggests that insect gut microbiomes may play a role in learning and behaviour, which are key for the survival of pollinators and for their pollination efficacy, and which in turn could be disrupted by dietary antibiotic exposure. In the laboratory, we tested the effects of an upper-limit dietary exposure to streptomycin (200 ppm)-an antibiotic widely used to treat bacterial pathogens in crops-on bumblebee (Bombus impatiens) associative learning, foraging and stimulus avoidance behaviour. We used two operant conditioning assays: a free movement proboscis extension reflex protocol focused on short-term memory formation, and an automated radio-frequency identification tracking system focused on foraging. We show that upper-limit dietary streptomycin exposure slowed training, decreased foraging choice accuracy, increased avoidance behaviour and was associated with reduced foraging on sucrose-rewarding artificial flowers flowers. This work underscores the need to further study the impacts of antibiotic use on beneficial insects in agricultural systems.

Microbiota and stress: a loop that impacts memory

Chronic stress and the gut microbiota appear to comprise a feed-forward loop, which contributes to the development of depressive disorders. Evidence suggests that memory can also be impaired by either chronic stress or microbiota imbalance. However, it remains to be established whether these could be a part of an integrated loop model and be responsible for memory impairments. To shed light on this, we used a two-pronged approach in Japanese quail: first stress-induced alterations in gut microbiota were characterized, then we tested whether this altered microbiota could affect brain and memory function when transferred to a germ-free host. The cecal microbiota of chronically stressed quails was found to be significantly different from that of unstressed individuals with lower α and β diversities and increased Bacteroidetes abundance largely represented by the Alistipes genus, a well-known stress target in rodents and humans. The transfer of this altered microbiota into germ-free quails decreased their spatial and cue-based memory abilities as previously demonstrated in the stressed donors. The recipients also displayed increased anxiety-like behavior, reduced basal plasma corticosterone levels and differential gene expression in the brain. Furthermore, cecal microbiota transfer from a chronically stressed individual was sufficient to mimic the adverse impact of chronic stress on memory in recipient hosts and this action may be related to the Alistipes genus. Our results provide evidence of a feed-forward loop system linking the microbiota-gut-brain axis to stress and memory function and suggest that maintaining a healthy microbiota could help alleviate memory impairments linked to chronic stress.