Diet, gut microbiota and cognition

Exercise recovers weight gain, but not increased impulsive choice, caused by a high-fat diet

A high-fat diet has negative effects on physical, neurological, and behavioral outcomes. One consistent finding is that a diet high in fat increases impulsive choice behavior-behavior that is linked to a wide range of other negative health behaviors. While the mechanism for this increase in impulsive choice is not well understood, exercise, with its well-known and many benefits, may serve as an effective and accessible way to combat increased impulsive choice associated with a high-fat diet. The goal of this work was to test this possibility. Rats were divided into four groups in a two-by-two factorial design: exercise and control diet, sedentary and control diet, exercise and high-fat diet, sedentary and high-fat diet. Rats in the exercise groups engaged in 30-min of forced, moderate intensity wheel-running exercise five days per week. Rats in the high-fat diet groups ate a diet high in fat. Impulsive choice was measured using a delay discounting task. Exercise prevented weight gain associated with the high-fat diet. Exercise also preserved relative motivation for food reinforcement. However, exercise did not prevent increases in impulsive choice observed for rats that consumed a high-fat diet relative to the rats that consumed the control diet. This work rules out several possible mechanisms by which a high-fat diet may increase impulsive choice behavior. It makes clear that exercise alone may not stave off increases in impulsive choice caused by a high-fat diet. Future work is necessary to uncover the underlying mechanism for this effect and discover interventions, perhaps ones that combine both physically and cognitively demanding activities, to improve health and behavior as it relates to decision making processes.

Altered intestinal microbiota induced by high-fat diets affect cognition differently in mice

The role of the gut microbiota in the association between high-fat diet and cognition is not clear. We hypothesized that a high-fat diet may influence cognition by altering the intestinal microbiota. Fecal microbiota isolated from male C57BL/6J mice feeding on various high-fat diets and a control basic diet were transplanted to antibiotic-treated recipient mice. The measurement of weight and plasma lipids, novel object recognition test, 16S rRNA gene sequencing of feces, and hematoxylin-eosin staining of the hippocampal cornu ammonis 1 and cornu ammonis 3 areas were performed for all mice. Compared with those in the control and n-3 polyunsaturated fatty acid (n-3 PUFA) groups, donor obese mice fed with diets high in long-chain saturated fatty acids, n-6 polyunsaturated fatty acids (n-6 PUFAs), and trans fatty acids exhibited significant cognitive impairment (all P < .05). There were fewer neurons in the hippocampal area in the n-6 PUFA group than in the n-3 PUFA group (P < .05). Similar effect on cognition and neurons in hippocampal area in corresponding recipient mice were revealed after fecal microbiota transplantation. In addition, the composition of intestinal microbiota differed among recipient mice after fecal microbiota transplantation from donor mice. According to these results, it was concluded that diets rich in long-chain saturated fatty acids, n-6 PUFAs, and trans fatty acids may lead to cognitive impairment by damaging the structure of the hippocampus through influencing the intestinal microbiota in mice, whereas a diet high in n-3 PUFAs may exhibit a beneficial effect.

Microbiota and social behavior alterations in a mouse model of down syndrome: Modulation by a synbiotic treatment

Sex differences in the composition and functionality of gut microbiota are an emerging field of interest in neurodevelopmental disorders, as they may help in understanding the phenotypic disparities between males and females. This study aimed to characterize sex-related specific alterations in gut microbiota composition in a mouse model of Down syndrome (Ts65Dn mice, TS mice) through the sequencing of the PCR-amplified 16S ribosomal DNA fraction. Moreover, it intended to examine whether the modulation of gut microbiota by the administration of a synbiotic (SYN) treatment would be beneficial for the behavioral alterations observed in male and female TS mice. Our results show that male, but not female, TS mice exhibit alterations in beta diversity compared to their wild-type (WT) littermates. Sex-dependent differences are also observed in the relative abundance of the classes Bacilli and Clostridia. Administering the SYN effectively counteracts hypersociability in females, and normalizes the overall abundance of Bacilli, specifically by increasing Lactobacillaceae. On the contrary, it rescues emotional recognition deficits in male TS mice and increases the relative abundance of the families Lactobacillaceae, Streptococcaceae and Atopobiaceae. In addition, a metagenome KEGG analysis of differentially enriched pathways shows relevant changes in the cofactor biosynthesis and the amino acid synthesis categories. Finally, following SYN treatment, both male and female TS mice exhibit a robust increase in propionic acid levels compared to WT littermates. These findings suggest sex-specific mechanisms that could link gut microbiota composition with behavior in TS mice, and underscore the potential of targeted gut microbiota interventions to modulate social abnormalities in neurodevelopmental disorders.

Cognotoxemia: endotoxemia and gender predict changes in working memory performance in healthy adults

Introduction

Examining the contribution of peripheral systems to cognitive function under healthy circumstances may improve our understanding of the systems that confer risk or resilience in diseased states. Endotoxemia-a pro-inflammatory response to the translocation of bacteria that reside in the gut on other sources (e.g., respiratory tract; infection) into the blood-was hypothesized to relate to worsened cognitive functioning. Gender was explored as a moderator.

Methods

A sample of 162 healthy adults (25-65 years old) provided plasma, from which a measure of endotoxemia was determined [i.e., the ratio of lipopolysaccharide binding protein (LBP) to soluble cluster of differentiation 14 receptors (sCD14)]. Participants performed an array of laboratory and ambulatory cognitive tasks at three timepoints, each separated by 9 months. Two sets of multilevel models were used: Prospective models, linking endotoxemia at baseline with changes in cognition across time, and coupling models, which examine correlations of endotoxemia with cognition across time.

Results

A prospective model indicated lower levels of endotoxemia at baseline predicted improvements in working memory across the three timepoints; higher levels were associated with no change in cognitive performance. Gender was not found to modulate this finding. Interestingly, a coupling analysis of endotoxemia and gender across time showed that in men, those with higher endotoxemia performed better at the working memory task overall; in women, working memory performance was similar regardless of endotoxemia level.

Conclusion

This work provides initial evidence that endotoxemia may be associated with a dampening of improvement in working memory, improvement consistent with practice effects, which should be expected in a sample of healthy, relatively young adults. The findings also provide preliminary evidence that, at least for men, higher degrees of endotoxemia are not inherently negative, and may link with short term positive outcomes for working memory.

What is the association between the microbiome and cognition? An umbrella review protocol

INTRODUCTION

Cognitive impairment is reported in a variety of clinical conditions including Alzheimer's disease, Parkinson's and 'long-COVID'. Interestingly, many of these clinical conditions are also associated with microbial dysbiosis. This comanifestation of cognitive and microbiome findings in seemingly unrelated maladies suggests that they could share a common mechanism and potentially presents a treatment target. Although a rapidly growing body of literature has documented this comorbid presentation within specific conditions, an overview highlighting potential parallels across healthy and clinical populations is lacking. The objective of this umbrella review, therefore, is to summarise and synthesise the findings of these systematic reviews.

METHODS AND ANALYSIS

On 2 April 2023, we searched MEDLINE (Pubmed), Embase (Ovid), the Web of Science (Core Collection), the Cochrane Library of Systematic Reviews and Epistemonikos as well as grey literature sources, for systematic reviews on clinical conditions and interventions where cognitive and microbiome outcomes were coreported. An updated search will be conducted before completion of the project if the search-to-publication date is >1 year old. Screening, data abstraction and quality assessment (AMSTAR 2, A MeaSurement Tool to Assess systematic Reviews) will be conducted independently and in duplicate, with disagreements resolved by consensus. Evidence certainty statements for each review's conclusions (eg, Grading of Recommendations Assessment, Development and Evaluation (GRADE)) will be extracted or constructed de novo. A narrative synthesis will be conducted and delineated by the review question. Primary study overlap will be visualised using a citation matrix as well as calculated using the corrected covered area method.

ETHICS AND DISSEMINATION

No participant-identifying information will be used in this review. No ethics approval was required due to our study methodology. Our findings will be presented at national and international conferences and disseminated via social media and press releases. We will recruit at least one person living with cognitive impairment to collaborate on writing the plain language summary for the review.

PROSPERO REGISTRATION NUMBER

CRD42023412903.

Microbiome-driven alterations in metabolic pathways and impaired cognition in aged female TgF344-AD rats

Alzheimer's disease (AD) not only affects cognition and neuropathology, but several other facets capable of negatively impacting quality of life and potentially driving impairments, including altered gut microbiome (GMB) composition and metabolism. Aged (20 + mo) female TgF344-AD and wildtype rats were cognitively characterized on several tasks incorporating several cognitive domains, including task acquisition, object recognition memory, anxiety-like behaviors, and spatial navigation. Additionally, metabolic phenotyping, GMB sequencing throughout the intestinal tract (duodenum, jejunum, ileum, colon, and feces), neuropathological burden assessment and marker gene functional abundance predictions (PICRUSt2) were conducted. TgF344-AD rats demonstrated significant cognitive impairment in multiple domains, as well as regionally specific GMB dysbiosis. Relationships between peripheral factors were investigated using Canonical Correspondence Analysis (CCA), revealing correlations between GMB changes and both cognitive and metabolic factors. Moreover, communities of gut microbes contributing to essential metabolic pathways were significantly altered in TgF344-AD rats. These data indicate dysbiosis may affect cognitive outcomes in AD through alterations in metabolism-related enzymatic pathways that are necessary for proper brain function. Moreover, these changes were mostly observed in intestinal segments required for carbohydrate digestion, not fecal samples. These data support the targeting of intestinal and microbiome health for the treatment of AD.

BDNF/CREB signaling pathway contribution in depression pathogenesis: A survey on the non-pharmacological therapeutic opportunities for gut microbiota dysbiosis

Emerging evidence supports the gut microbiota and the brain communication in general health. This axis may affect behavior through modulating neurotransmission, and thereby involve in the pathogenesis and/or progression of different neuropsychiatric disorders such as depression. Brain-derived neurotrophic factor and cAMP response element-binding protein known as CREB/BDNF pathway plays have critical functions in the pathogenesis of depression as the same of mechanisms related to antidepressants. However, the putative causal significance of the CREB/BDNF signaling cascade in the gut-brain axis in depression remains unknown. Also interventions such as probiotics supplementation and exercise can influence microbiome also improve bidirectional communication of gut and brain. In this review we aim to explain the BDNF/CREB signaling pathway and gut microbiota dysfunction and then evaluate the potential role of probiotics, prebiotics, and exercise as a therapeutic target in the gut microbiota dysfunction induced depression. The current narrative review will specifically focus on the impact of exercise and diet on the intestinal microbiota component, as well as the effect that these therapies may have on the microbiota to alleviate depressive symptoms. Finally, we look at how BDNF/CREB signaling pathway may exert distinct effects on depression and gut microbiota dysfunction.

Chemoprevention by Microencapsulated Lactiplantibacillus Plantarum LAB12 Against Orthotopic Colorectal Cancer Mice is Associated with Apoptosis and Anti-angiogenesis

The pathogenesis of colorectal cancer (CRC) is associated with gut dysbiosis that is attributed to unhealthy lifestyles and dietary habits. Consumption of microencapsulated probiotics may potentially restore the gut microbiota in favour of prevention against CRC. This study determined the fate of microencapsulated Lactiplantibacillus plantarum (formerly known as Lactobacillus plantarum) LAB12 in the gastrointestinal tract (GIT) and assessed the chemopreventive effect of microencapsulated L. plantarum LAB12 in vivo. The targeted release of L. plantarum LAB12 from Alg-based microcapsules at the stomach, ileum, caecum and colon of Sprague-Dawley rats was examined by confocal microscopy and qPCR. Microcapsules loaded with L. plantarum LAB12 remained intact in the stomach. Free L. plantarum LAB12 were present in abundance (> 7 log CFU) only in the intestines. Subsequently, the chemopreventive properties of microencapsulated L. plantarum LAB12 were validated against NU/NU nude mice bearing orthotopic transplanted CT-26 CRC (12 female mice; 4-6 weeks old; 20-22 g; n = 6/group). Orthotopic mice pre-supplemented with microencapsulated L. plantarum LAB12 (10 log CFU kg-1 BW for 11 weeks) were presented with significantly (p < 0.05) reduced tumour volume (- 98.87%) and weight (- 89.27%) when compared to control. Western blots indicated that the chemopreventive effect could be attributed to apoptosis and anti-angiogenesis mediated, at least in part, through upregulation of tumour suppressor p53 (+ 45.4%) and pro-apoptotic caspase-3 (+ 82.4%), and downregulation of pro-inflammatory COX-2 (- 57.9%), pro-angiogenic VEGF (- 66.8%) and PECAM-1 (-64.1%). Altogether, this study strongly implied the possibility of having L. plantarum LAB12-loaded microcapsules safely incorporated into food and nutraceutical products for prevention against CRC.

The impact of diet quality on cognitive ability of Chinese older adults: evidence from the China Health and Nutrition Survey (CHNS)

BACKGROUND

Numerous studies have demonstrated a positive correlation between diet quality and cognitive performance, indicating that improving diet quality may be beneficial in preventing cognitive decline in older adults. However, few study has investigated the causal relationship between diet quality and cognitive performance. The purpose of this study is to evaluate the causal effects of diet quality on cognitive performance in Chinese adults aged 55 years and older. Particularly, we utilize the Chinese Diet Quality Index (CHEI), a dietary assessment tool tailored for Chinese populations, as a proxy for older adults' diet quality.

METHODS

Data were obtained from the China Health and Nutrition Survey (CHNS) ([Formula: see text], [Formula: see text]55 years old) conducted in 2004 and 2006. Cognitive function was tested by a subset of items from the Telephone Interview for Cognitive Status-Modified (TICS-m). Data on dietary intake was retrieved from three consecutive 24 hour recalls by participants and its quality was assessed by the 17-items Chinese Healthy Eating Index (CHEI). An Instrumental Variable technique was used to deal with the potential endogeneity of dietary quality. The instrumental variable used in our study is the community mean of CHEI.

RESULTS

After adjusting for socio-demographic factors (age, gender, education, per capita household income), lifestyle habits (smoking, alcohol consumption, physical activity, BMI), and chronic diseases (hypertension, diabetes), our findings revealed that improving diet quality had a significant positive effect on cognitive performance ([Formula: see text]), particularly in females aged 55-65 years ([Formula: see text]) and females with primary education and below ([Formula: see text]).

CONCLUSION

Our study suggests that improving diet quality and adhering to the Dietary Guidelines for Chinese may enhance cognitive performance in Chinese adults aged 55 years and older.

Multi-nutrient interventions and cognitive ageing: are we barking up the right tree?

As we continue to elucidate the mechanisms underlying age-related brain diseases, the reductionist strategy in nutrition–brain function research has focused on establishing the impact of individual foods. However, the biological processes connecting diet and cognition are complex. Therefore, consideration of a combination of nutritional compounds may be most efficacious. One barrier to establishing the efficacy of multi-nutrient interventions is that the area lacks an established set of evidence-based guidelines for studying their effect on brain health. This review is an output of the International Life Sciences Institute (ILSI) Europe. A multi-disciplinary expert group was assembled with the aim of developing a set of considerations to guide research into the effects of multi-nutrient combinations on brain functions. Consensus recommendations converged on six key issues that should be considered to advance research in this area: (1) establish working mechanisms of the combination and contributions of each individual compound; (2) validate the relevance of the mechanisms for the targeted human condition; (3) include current nutrient status, intake or dietary pattern as inclusion/exclusion criteria in the study design; (4) select a participant population that is clinically and biologically appropriate for all nutritional components of the combination; (5) consider a range of cognitive outcomes; (6) consider the limits of reductionism and the ‘gold standard’ randomised controlled trial. These guiding principles will enhance our understanding of the interactive/complementary activities of dietary components, thereby strengthening the evidence base for recommendations aimed at delaying cognitive decline.

Peripheral inflammation and neurocognitive impairment: correlations, underlying mechanisms, and therapeutic implications

Cognitive impairments, such as learning and memory deficits, may occur in susceptible populations including the elderly and patients who are chronically ill or have experienced stressful events, including surgery, infection, and trauma. Accumulating lines of evidence suggested that peripheral inflammation featured by the recruitment of peripheral immune cells and the release of pro-inflammatory cytokines may be activated during aging and these conditions, participating in peripheral immune system-brain communication. Lots of progress has been achieved in deciphering the core bridging mechanism connecting peripheral inflammation and cognitive impairments, which may be helpful in developing early diagnosis, prognosis evaluation, and prevention methods based on peripheral blood circulation system sampling and intervention. In this review, we summarized the evolving evidence on the prevalence of peripheral inflammation-associated neurocognitive impairments and discussed the research advances in the underlying mechanisms. We also highlighted the prevention and treatment strategies against peripheral inflammation-associated cognitive dysfunction.

The effect of free school fruit on academic performance: a nationwide quasi-experiment

In past research, higher intake of fruit has been associated with better academic achievement. In Norway, the government required lower secondary schools to provide fruit to their pupils from 2007 to 2014. The present study assessed whether this policy improved academic performance. In addition to secondary schools, the policy covered schools with combined elementary and lower secondary education, but not ordinary elementary schools. This differentiation, in combination with administrative data on test scores before, during, and after the law was enforced, created a nationwide quasi-experiment. Population register data on parents' sociodemographic characteristics allowed for targeted analyses on a subsample of boys with low sociodemographic status. In analyses of 5th grade tests, the free fruit policy coincided with a slight decline in test scores among eligible compared to non-eligible pupils in the subsample (B = - 0.18, 95%CI[- 0.35, - 0.01]) and entire population (B = - 0.14, 95%CI[- 0.24, - 0.05]). Exploratory analyses of exam data in 10th grade yielded similar results, and sensitivity tests either failed to detect any effect or demonstrated a negative tendency. In a Western country with low levels of food insecurity, a policy that required schools to provide free fruit to pupils did not appear to improve academic performance.

Understanding the impact of radical changes in diet and the gut microbiota on brain function and structure: rationale and design of the EMBRACE study

BACKGROUND

Bariatric surgery leads to profound changes in gut microbiota and dietary patterns, both of which may interact to impact gut-brain communication. Though cognitive function improves postsurgery, there is a large variability in outcomes. How bariatric surgery-induced modifications in the gut microbiota and dietary patterns influence the variability in cognitive function is still unclear.

OBJECTIVES

To elucidate the associations between bariatric surgery-induced changes in dietary and gut microbiota patterns with cognition and brain structure.

SETTING

University hospital.

METHODS

A total of 120 adult patients (≥30 years) scheduled to undergo a primary bariatric surgery along with 60 age-, sex-, and body mass index-matched patients on the surgery waitlist will undergo assessments 3-months presurgery and 6- and 12-month postsurgery (or an equivalent time for the waitlist group). Additionally, 60 age-and sex-matched nonbariatric surgery eligible individuals will complete the presurgical assessments only. Evaluations will include sociodemographic and health behavior questionnaires, physiological assessments (anthropometrics, blood-, urine-, and fecal-based measures), neuropsychological cognitive tests, and structural magnetic resonance imaging. Cluster analyses of the dietary and gut microbiota changes will define the various dietary patterns and microbiota profiles, then using repeated measures mixed models, their associations with global cognitive and structural brain alterations will be explored.

RESULTS

The coordinating study site (Centre intégré universitaire de santé et de services sociaux du Nord-de-l'Île-de-Montréal, QC, Canada), provided the primary ethical approval (Research Ethics Board#: MP-32-2022-2412).

CONCLUSIONS

The insights generated from this study can be used to develop individually-targeted neurodegenerative disease prevention strategies, as well as providing critical mechanistic information.

The microbiota-gut-brain axis in hippocampus-dependent learning and memory: current state and future challenges

A fundamental shift in neuroscience suggests bidirectional interaction of gut microbiota with the healthy and dysfunctional brain. This microbiota-gut-brain axis has mainly been investigated in stress-related psychopathology (e.g. depression, anxiety). The hippocampus, a key structure in both the healthy brain and psychopathologies, is implicated by work in rodents that suggests gut microbiota substantially impact hippocampal-dependent learning and memory. However, understanding microbiota-hippocampus mechanisms in health and disease, and translation to humans, is hampered by the absence of a coherent evaluative approach. We review the current knowledge regarding four main gut microbiota-hippocampus routes in rodents: through the vagus nerve; via the hypothalamus-pituitary-adrenal-axis; by metabolism of neuroactive substances; and through modulation of host inflammation. Next, we suggest an approach including testing (biomarkers of) the four routes as a function of the influence of gut microbiota (composition) on hippocampal-dependent (dys)functioning. We argue that such an approach is necessary to proceed from the current state of preclinical research to beneficial application in humans to optimise microbiota-based strategies to treat and enhance hippocampal-dependent memory (dys)functions.

The relationship between dietary patterns derived from inflammation and cognitive impairment in patients undergoing hemodialysis

Introduction

Dietary patterns were shown to be closely related to inflammation, which was independently associated with cognitive impairment (CI) in patients undergoing hemodialysis (HD). However, it remains unclear the influence of dietary patterns derived from inflammation on CI in this population. This study aimed to examine the association between dietary patterns derived from C-reactive protein (CRP) and interleukin-6 (IL-6) and CI in patients undergoing HD.

Methods

Dietary intake was obtained from the simplified quantitative food frequency questionnaire. Reduced rank regression (RRR) was used to extract two dietary patterns, with IL-6 and CRP as response variables. Cognitive function was examined by the Montreal Cognitive Assessment (Beijing version). Venous blood was drawn for measuring IL-6 and CRP levels. Multivariable logistic regression was used to investigate the association between dietary patterns and CI.

Results

Dietary pattern derived from IL-6 was not significantly associated with CI. The third quartile of dietary pattern, which used CRP as the response variable, significantly contributed to the increased risk of CI (AOR 8.62, 95% CI 1.47-50.67) after controlling age, sex, education level, marital status, and residential pattern (p-for-trend = 0.028). After considering hypertension and diabetes, physical activity level, anxiety and depression, smoking and drinking status, social support, energy intake, and the dietary pattern derived from IL-6 (p-for-trend = 0.026), the relationship between the dietary pattern derived from CRP and CI remained significant (AOR 14.54, 95% CI 1.40-151.13).

Conclusion

Dietary pattern associated with high CRP level, including high intake of rice, liquor, fruit, tea and coffee and low intake of dark vegetables and juice, contributed to the increased risk of CI. The association between the consumption of seafood, sweet beverages, and alcohol and CI is yet to be established. However, they may be dietary contributing factors to inflammation in patients undergoing HD.

Ambient particulate air pollution and the intestinal microbiome; a systematic review of epidemiological, in vivo and, in vitro studies

A healthy indigenous intestinal microbiome is indispensable for intra- and extra-intestinal human health. Since well-established factors such as diet and antibiotic use only explain 16 % of the inter-individual variation in gut microbiome composition, recent studies have focused on the association between ambient particulate air pollution and the intestinal microbiome. We systematically summarize and discuss all evidence concerning the effect of particulate air pollution on intestinal bacterial diversity indices, specific bacterial taxa, and potential underlying intestinal mechanisms. To this end, all possibly relevant publications published between February 1982 and January 2023 were screened, and eventually, 48 articles were included. The vast majority (n = 35) of these studies were animal studies. The exposure periods investigated in the human epidemiological studies (n = 12) ranged from infancy through elderly. This systematic review found that intestinal microbiome diversity indices were generally negatively associated with particulate air pollution in epidemiological studies, with an increase in taxa belonging to Bacteroidetes (two studies), Deferribacterota (one study), and Proteobacteria (four studies), a decrease in taxa belonging to Verrucomicrobiota (one study), and no consensus for taxa belonging to Actinobacteria (six studies) and Firmicutes (seven studies). There was no unequivocal effect of ambient particulate air pollution exposure on bacterial indices and taxa in animal studies. Only one study in humans examined a possible underlying mechanism; yet, the included in vitro and animal studies depicted higher gut damage, inflammation, oxidative stress, and permeability in exposed versus unexposed animals. Overall, the population-based studies showed a dose-related continuum of short- and long-term ambient particulate air pollution exposure on lower gut diversity and shifts in taxa over the entire life course.

Signalling cognition: the gut microbiota and hypothalamic-pituitary-adrenal axis

Cognitive function in humans depends on the complex and interplay between multiple body systems, including the hypothalamic-pituitary-adrenal (HPA) axis. The gut microbiota, which vastly outnumbers human cells and has a genetic potential that exceeds that of the human genome, plays a crucial role in this interplay. The microbiota-gut-brain (MGB) axis is a bidirectional signalling pathway that operates through neural, endocrine, immune, and metabolic pathways. One of the major neuroendocrine systems responding to stress is the HPA axis which produces glucocorticoids such as cortisol in humans and corticosterone in rodents. Appropriate concentrations of cortisol are essential for normal neurodevelopment and function, as well as cognitive processes such as learning and memory, and studies have shown that microbes modulate the HPA axis throughout life. Stress can significantly impact the MGB axis via the HPA axis and other pathways. Animal research has advanced our understanding of these mechanisms and pathways, leading to a paradigm shift in conceptual thinking about the influence of the microbiota on human health and disease. Preclinical and human trials are currently underway to determine how these animal models translate to humans. In this review article, we summarize the current knowledge of the relationship between the gut microbiota, HPA axis, and cognition, and provide an overview of the main findings and conclusions in this broad field.

Review of Plant Extracts and Active Components: Mechanisms of Action for the Treatment of Obesity-Induced Cognitive Impairment

Obesity has been shown to negatively impact cognitive functions, but effective treatments for obesity-induced cognitive impairment are lacking. Natural dietary and plant products, functional foods, and plant-derived compounds have gained attention as potential remedies in part due to the nootropic properties of plants and certain plant-derived agents. This review discusses plant extracts and plant-derived substances that have been shown to ameliorate obesity-induced cognitive impairment in animal models. Mechanistic evaluations of their therapeutic effects are also summarized. A literature search was conducted using PubMed and Google Scholar databases, resulting in the review of 27 English language articles meeting the inclusion criteria. The nine plants (e.g., Ashwagandha, Adzuki bean, and olive) and 18 plant-derived substances (e.g., curcumin, Huperzine A, and Roxburgh's jewel orchid polysaccharides) included in this review improved obesity-induced cognitive impairment through several mechanisms, including attenuation of neuroinflammation, improvement in both central and peripheral insulin resistance, enhancement of neuroprotection and neurogenesis, and modulation of the synthesis and release of cognition-associated neurotransmitters. Based on these findings, plants and plant-derived substances may hold promise for the prevention and treatment of obesity-induced cognitive impairment. Further research is warranted to explore the clinical potential of these plant-derived treatments and to elucidate their underlying molecular mechanisms.

Defining the Relationship of Gut Microbiota, Immunity, and Cognition in Early Life-A Narrative Review

Recently, the immune system has been identified as one of the possible main bridges which connect the gut-brain axis. This review aims to examine available evidence on the microbiota-immunity-cognitive relationship and its possible effects on human health early in life. This review was assembled by compiling and analyzing various literature and publications that document the gut microbiota-immune system-cognition interaction and its implications in the pediatric population. This review shows that the gut microbiota is a pivotal component of gut physiology, with its development being influenced by a variety of factors and, in return, supports the development of overall health. Findings from current research focus on the complex relationship between the central nervous system, gut (along with gut microbiota), and immune cells, highlighting the importance of maintaining a balanced interaction among these systems for preserving homeostasis, and demonstrating the influence of gut microbes on neurogenesis, myelin formation, the potential for dysbiosis, and alterations in immune and cognitive functions. While limited, evidence shows how gut microbiota affects innate and adaptive immunity as well as cognition (through HPA axis, metabolites, vagal nerve, neurotransmitter, and myelination).

The relationship between gut microbiota and inflammatory response, learning and memory in mice by sleep deprivation

Objective

Sleep deprivation has developed into a common phenomenon, which can lead to inflammatory responses and cognitive impairment, but the underlying mechanism is ambiguous. Emerging evidence shows that gut microbiota plays a crucial role in theoccurrence and development of inflammatory and psychiatric diseases, possibly through neuroinflammation and the brain-gut axis. The current study investigated the influence of sleep deprivation on gut microbiota composition, pro-inflammatory cytokines, learning and memory in mice. Further, it explored whether changes in gut microbiota increase pro-inflammatory cytokine and induce learning and memory impairment.

Methods

Healthy 8-week-old male C57BL/6J mice were randomly divided into the regular control group (RC), environmental control group (EC), and sleep deprivation group (SD). The sleep deprivation model was established by the Modified Multiple Platform Method. The experimental mice were subjected to sleep deprivation for 6h/d (8:00 am∼14:00 pm) in a sleep deprivation chamber, and the duration of sleep deprivation was 8 weeks. Morris water maze test to assess learning and memory in mice. Enzyme-Linked Immunosorbent Assay determined the concentrations of inflammatory cytokines. The changes in gut microbiota in mice were analyzed by 16S rRNA sequencing.

Results

We found that SD mice had elevated latency of exploration to reach the hidden platform (p>0.05) and significantly decreased traversing times, swimming distance, and swimming time in the target zone when the hidden platform was removed (p<0.05). Sleep deprivation caused dysregulated expression in serum IL-1β, IL-6, and TNF-α in mice, and the difference was significant (all p<0.001). Tannerellaceae, Rhodospirillales, Alistipes, and Parabacteroides were significantly increased in SD mice. Correlation analysis showed IL-1β was positively correlated with the abundance of Muribaculaceae (r=0.497, p<0.05) and negatively correlated with the abundance of Lachnospiraceae (r=-0.583, p<0.05). The TNF-α was positively correlated with the abundances of Erysipelotrichaceae, Burkholderiaceae, and Tannerellaceae (r=0.492, r=0.646, r=0.726, all p<0.05).

Conclusion

Sleep deprivation can increase pro-inflammatory cytokine responses and learning and memory impairment in mice and may be caused by the disorder of the microbiota. These findings of this study may open avenues for potential interventions that can relieve the detrimental consequences of sleep loss.

Probiotics therapy show significant improvement in obesity and neurobehavioral disorders symptoms

Obesity is a complex metabolic disease, with cognitive impairment being an essential complication. Gut microbiota differs markedly between individuals with and without obesity. The microbial-gut-brain axis is an important pathway through which metabolic factors, such as obesity, affect the brain. Probiotics have been shown to alleviate symptoms associated with obesity and neurobehavioral disorders. In this review, we evaluated previously published studies on the effectiveness of probiotic interventions in reducing cognitive impairment, depression, and anxiety associated with obesity or a high-fat diet. Most of the probiotics studied have beneficial health effects on obesity-induced cognitive impairment and anxiety. They positively affect immune regulation, the hypothalamic-pituitary-adrenal axis, hippocampal function, intestinal mucosa protection, and glucolipid metabolism regulation. Probiotics can influence changes in the composition of the gut microbiota and the ratio between various flora. However, probiotics should be used with caution, particularly in healthy individuals. Future research should further explore the mechanisms underlying the gut-brain axis, obesity, and cognitive function while overcoming the significant variation in study design and high risk of bias in the current evidence.

Food, gut barrier dysfunction, and related diseases: A new target for future individualized disease prevention and management

Dysfunction of gut barrier is known as "leaky gut" or increased intestinal permeability. Numerous recent scientific evidences showed the association between gut dysfunction and multiple gastrointestinal tract (GI) and non-GI diseases. Research also demonstrated that food plays a crucial role to cause or remedy gut dysfunction related to diseases. We reviewed recent articles from electronic databases, mainly PubMed. The data were based on animal models, cell models, and human research in vivo and in vitro models. In this comprehensive review, our aim focused on the relationship between dietary factors, intestinal permeability dysfunction, and related diseases. This review synthesizes currently available literature and is discussed in three parts: (a) the mechanism of gut barrier and function, (b) food and dietary supplements that may promote gut health, and food or medication that may alter gut function, and (c) a table that organizes the synthesized information by general mechanisms for diseases related to leaky gut/intestinal permeability and associated dietary influences. With future research, dietary intervention could be a new target for individualized disease prevention and management.

Ghrelin regulates the proliferation and apoptosis of high glucose-induced islet cells through the PI3K-Akt signaling pathway

Ghrelin may have therapeutic value in mitigating insulin resistance and type 2 diabetes, based on which we further explore the action mechanism of ghrelin on islet cells in this research. In the course of experiments, MIN6 cells were induced by glucose and then treated with acylated or unacylated ghrelin. The effects of ghrelin on the viability, proliferation, apoptosis, and insulin release of high glucose-induced islet cells were detected by Cell Counting Kit-8, 5-ethynyl-2'-deoxyuridine, flow cytometry, and enzyme-linked immunosorbent assays, respectively. Meanwhile, cells were treated with LY294002 to explore whether and how the inhibited phosphoinositide 3-kinase-protein kinase B (PI3K-AKT) signaling pathway participated in the internal mechanism of ghrelin-regulating islet cells. Western blotting was performed to quantify the expression levels of Bcl-2, Bax, Cleaved caspase-3, PI3K, and AKT. As a result, ghrelin alleviated high glucose-induced suppression of viability and proliferation and promotion on apoptosis of MIN6 cells. Ghrelin also attenuated the inhibitory effects of high glucose on expression levels of PI3K-Akt signaling axis-related proteins and insulin release in MIN6 cells. Besides, ghrelin weakened the impacts of high glucose on boosting MIN6 cell apoptosis and hindering proliferation through the PI3K-Akt signaling axis. Collectively, ghrelin regulates the proliferation and apoptosis of high glucose-induced islet cells through the PI3K-Akt signaling pathway.

Soluble TNF mediates amyloid-independent, diet-induced alterations to immune and neuronal functions in an Alzheimer's disease mouse model

Introduction: Increasing evidence indicates that neurodegenerative diseases, including Alzheimer's disease (AD), are a product of gene-by-environment interplay. The immune system is a major contributor mediating these interactions. Signaling between peripheral immune cells and those within the microvasculature and meninges of the central nervous system (CNS), at the blood-brain barrier, and in the gut likely plays an important role in AD. The cytokine tumor necrosis factor (TNF) is elevated in AD patients, regulates brain and gut barrier permeability, and is produced by central and peripheral immune cells. Our group previously reported that soluble TNF (sTNF) modulates cytokine and chemokine cascades that regulate peripheral immune cell traffic to the brain in young 5xFAD female mice, and in separate studies that a diet high in fat and sugar (HFHS) dysregulates signaling pathways that trigger sTNF-dependent immune and metabolic responses that can result in metabolic syndrome, which is a risk factor for AD. We hypothesized that sTNF is a key mediator of peripheral immune cell contributions to gene-by-environment interactions to AD-like pathology, metabolic dysfunction, and diet-induced gut dysbiosis. Methods: Female 5xFAD mice were subjected to HFHS diet for 2 months and then given XPro1595 to inhibit sTNF for the last month or saline vehicle. We quantified immune cell profiles by multi-color flow cytometry on cells isolated from brain and blood; metabolic, immune, and inflammatory mRNA and protein marker biochemical and immunhistological analyses, gut microbiome, and electrophysiology in brain slices were also performed. Results: Here, we show that selective inhibition of sTNF signaling via the biologic XPro1595 modulates the effects of an HFHS diet in 5xFAD mice on peripheral and central immune profiles including CNS-associated CD8+ T cells, the composition of gut microbiota, and long-term potentiation deficits. Discussion: Obesogenic diet induces immune and neuronal dysfunction in 5xFAD mice and sTNF inhibition mitigates its effects. A clinical trial in subjects at risk for AD due to genetic predisposition and underlying inflammation associated with peripheral inflammatory co-morbidities will be needed to investigate the extent to which these findings translate to the clinic.

Lipidomic analysis of brain and hippocampus from mice fed with high-fat diet and treated with fecal microbiota transplantation

BACKGROUND

Dietary fat intake affects brain composition and function. Different types of dietary fatty acids alter species and abundance of brain lipids in mice. The aim of this study is to explore whether the changes are effective through gut microbiota.

METHODS

In our study, 8-week-old male C57BL/6 mice were randomly divided into 7 groups and fed with high-fat diet (HFD) with different fatty acid compositions, control (CON) group, long-chain saturated fatty acid (LCSFA) group, medium-chain saturated fatty acid (MCSFA) group, n-3 polyunsaturated fatty acid (n-3 PUFA) group, n-6 polyunsaturated fatty acid (n-6 PUFA) group, monounsaturated fatty acid (MUFA) group and trans fatty acid (TFA) group. Then, the fecal microbiota transplant (FMT) was performed in other pseudo germ-free mice after antibiotic treatment. The experimental groups were orally perfused with gut microbiota that induced by HFD with different types of dietary fatty acids. The mice were fed with regular fodder before and after FMT. High-performance liquid chromatography-mass spectrometry (LC-MS) was used to analysis the composition of fatty acids in the brain of HFD-fed mice and hippocampus of mice treated with FMT which was collected from HFD-fed mice.

RESULTS

The content of acyl-carnitines (AcCa) increased and lysophosphatidylgylcerol (LPG) decreased in all kinds of HFD groups. phosphatidic acids (PA), phosphatidylethanolamine (PE) and sphingomyelin (SM) contents were significantly increased in the n-6 PUFA-fed HFD group. The HFD elevated the saturation of brain fatty acyl (FA). Lysophosphatidylcholine (LPC), lysodi-methylphosphatidylethanolamine (LdMePE), monolysocardiolipin (MLCL), dihexosylceramides (Hex2Cer), and wax ester (WE) significantly increased after LCSFA-fed FMT. MLCL reduced and cardiolipin (CL) raised significantly after n-3 PUFA-fed FMT.

CONCLUSIONS

The study revealed, HFD and FMT in mice had certain effects on the content and composition of fatty acids in the brain, especially on glycerol phospholipid (GP). The change of AcCa content in FA was a good indicator of dietary fatty acid intake. By altering the fecal microbiota, dietary fatty acids might affect brain lipids.

Microbiota alteration of Chinese young male adults with high-status negative cognitive processing bias

Introduction

Evidence suggests that negative cognitive processing bias (NCPB) is a significant risk factor for depression. The microbiota-gut-brain axis has been proven to be a contributing factor to cognitive health and disease. However, the connection between microbiota and NCPB remains unknown. This study mainly sought to explore the key microbiota involved in NCPB and the possible pathways through which NCPB affects depressive symptoms.

Methods

Data in our studies were collected from 735 Chinese young adults through a cross-sectional survey. Fecal samples were collected from 35 young adults with different levels of NCPB (18 individuals were recruited as the high-status NCPB group, and another 17 individuals were matched as the low-status NCPB group) and 60 with different degrees of depressive symptoms (27 individuals were recruited into the depressive symptom group, as D group, and 33 individuals were matched into the control group, as C group) and analyzed by the 16S ribosomal RNA sequencing technique.

Results

As a result, the level of NCPB correlated with the degree of depressive symptoms as well as anxiety symptoms and sleep quality (p < 0.01). The β-diversity of microbiota in young adults was proven to be significantly different between the high-status NCPB and the low-status NCPB groups. There were several significantly increased bacteria taxa, including Dorea, Christensenellaceae, Christe -senellaceae_R_7_group, Ruminococcaceae_NK4A214_group, Eggerthellaceae, Family-XIII, Family_XIII_AD3011_group, Faecalibaculum, and Oscillibacter. They were mainly involved in pathways including short-chain fatty acid (SCFA) metabolism. Among these variable bacteria taxa, Faecalibaculum was found associated with both NCPB and depressive symptoms. Furthermore, five pathways turned out to be significantly altered in both the high-status NCPB group and the depressive symptom group, including butanoate metabolism, glyoxylate and dicarboxylate metabolism, propanoate metabolism, phenylalanine, tyrosine, and tryptophan biosynthesis, valine, leucine, and isoleucine degradation. These pathways were related to SCFA metabolism.

Discussion

Fecal microbiota is altered in Chinese young male adults with high status NCPB and may be involved in the biochemical progress that influences depressive symptoms.

Interactive relationships of Type 2 diabetes and bipolar disorder with cognition: evidence of putative premature cognitive ageing in the UK Biobank Cohort

Type 2 diabetes (T2D) is disproportionately prevalent in bipolar disorder (BD) and is associated with cognitive deficits in psychiatrically healthy cohorts. Whether there is an interaction effect between T2D and BD on cognition remains unclear. Using the UK Biobank, we explored interactions between T2D, BD and cognition during mid and later life; and examined age-related cognitive performance effects in BD as a function of T2D. Data were available for 1511 participants with BD (85 T2D), and 81,162 psychiatrically healthy comparisons (HC) (3430 T2D). BD and T2D status were determined by validated measures created specifically for the UK Biobank. Diagnostic and age-related associations between T2D status and cognition were tested using analyses of covariance or logistic regression. There was a negative association of T2D with visuospatial memory that was specific to BD. Processing speed and prospective memory performance were negatively associated with T2D, irrespective of BD diagnosis. Cognitive deficits were evident in BD patients with T2D compared to those without, with scores either remaining the same (processing speed) or improving (visuospatial memory) as a function of participant age. In contrast, cognitive performance in BD patients without T2D was worse as participant age increased, although the age-related trajectory remained broadly equivalent to the HC group. BD and T2D associated with cognitive performance deficits across the mid-life period; indicating comorbid T2D as a potential risk factor for cognitive dysfunction in BD. In comparison to BD participants without T2D and HCs, age-independent cognitive impairments in BD participants with comorbid T2D suggest a potential premature deterioration of cognitive functioning compared to what would normally be expected.

Accumulation of Black Carbon Particles in Placenta, Cord Blood, and Childhood Urine in Association with the Intestinal Microbiome Diversity and Composition in Four- to Six-Year-Old Children in the ENVIRONAGE Birth Cohort

BACKGROUND

The gut microbiome plays an essential role in human health. Despite the link between air pollution exposure and various diseases, its association with the gut microbiome during susceptible life periods remains scarce.

OBJECTIVES

In this study, we examined the association between black carbon particles quantified in prenatal and postnatal biological matrices and bacterial richness and diversity measures, and bacterial families.

METHODS

A total of 85 stool samples were collected from 4- to 6-y-old children enrolled in the ENVIRonmental influence ON early AGEing birth cohort. We performed 16S rRNA gene sequencing to calculate bacterial richness and diversity indices (Chao1 richness, Shannon diversity, and Simpson diversity) and the relative abundance of bacterial families. Black carbon particles were quantified via white light generation under femtosecond pulsed laser illumination in placental tissue and cord blood, employed as prenatal exposure biomarkers, and in urine, used as a post-natal exposure biomarker. We used robust multivariable-adjusted linear models to examine the associations between quantified black carbon loads and measures of richness (Chao1 index) and diversity (Shannon and Simpson indices), adjusting for parity, season of delivery, sequencing batch, age, sex, weight and height of the child, and maternal education. Additionally, we performed a differential relative abundance analysis of bacterial families with a correction for sampling fraction bias. Results are expressed as percentage difference for a doubling in black carbon loads with 95% confidence interval (CI).

RESULTS

Two diversity indices were negatively associated with placental black carbon [Shannon: -4.38% (95% CI: -8.31%, -0.28%); Simpson: -0.90% (95% CI: -1.76%, -0.04%)], cord blood black carbon [Shannon: -3.38% (95% CI: -5.66%, -0.84%); Simpson: -0.91 (95% CI: -1.66%, -0.16%)], and urinary black carbon [Shannon: -3.39% (95% CI: -5.77%, -0.94%); Simpson: -0.89% (95% CI: -1.37%, -0.40%)]. The explained variance of black carbon on the above indices varied from 6.1% to 16.6%. No statistically significant associations were found between black carbon load and the Chao1 richness index. After multiple testing correction, placental black carbon was negatively associated with relative abundance of the bacterial families Defluviitaleaceae and Marinifilaceae, and urinary black carbon with Christensenellaceae and Coriobacteriaceae; associations with cord blood black carbon were not statistically significant after correction.

CONCLUSION

Black carbon particles quantified in prenatal and postnatal biological matrices were associated with the composition and diversity of the childhood intestinal microbiome. These findings address the influential role of exposure to air pollution during pregnancy and early life in human health. https://doi.org/10.1289/EHP11257.

Intriguing Role of Gut-Brain Axis on Cognition with an Emphasis on Interaction with Papez Circuit

The gut microbiome is a complicated ecosystem of around a hundred billion symbiotic bacteria cells. Bidirectional communication between the gut and the brain is facilitated by the immune system, the enteric nervous system, the vagus nerve, and microbial compounds such as tryptophan metabolites and short-chain fatty acids (SCFAs). The current study emphasises the relationship of the gut-brain axis with cognitive performance and elucidates the underlying biological components, with a focus on neurotransmitters such as serotonin, indole derivatives, and catecholamine. These biological components play important roles in both the digestive and brain systems. Recent research has linked the gut microbiome to a variety of cognitive disorders, including Alzheimer's (AD). The review describes the intriguing role of the gut-brain axis in recognition memory depending on local network connections within the hippocampal as well as other additional hippocampal portions of the Papez circuit. The available data from various research papers show how the gut microbiota might alter brain function and hence psychotic and cognitive illnesses. The role of supplementary probiotics is emphasized for the reduction of brain-related dysfunction as a viable strategy in handling cognitive disorders. Further, the study elucidates the mode of action of probiotics with reported adverse effects.

Integrating Rehabilomics into the Multi-Omics Approach in the Management of Multiple Sclerosis: The Way for Precision Medicine?

Over recent years, significant improvements have been made in the understanding of (epi)genetics and neuropathophysiological mechanisms driving the different forms of multiple sclerosis (MS). For example, the role and importance of the bidirectional communications between the brain and the gut-also referred to as the gut-brain axis-in the pathogenesis of MS is receiving increasing interest in recent years and is probably one of the most promising areas of research for the management of people with MS. However, despite these important advances, it must be noted that these data are not-yet-used in rehabilitation. Neurorehabilitation is a cornerstone of MS patient management, and there are many techniques available to clinicians and patients, including technology-supported rehabilitation. In this paper, we will discuss how new findings on the gut microbiome could help us to better understand how rehabilitation can improve motor and cognitive functions. We will also see how the data gathered during the rehabilitation can help to get a better diagnosis of the patients. Finally, we will discuss how these new techniques can better guide rehabilitation to lead to precision rehabilitation and ultimately increase the quality of patient care.

What Are the Key Gut Microbiota Involved in Neurological Diseases? A Systematic Review

There is a growing body of evidence highlighting there are significant changes in the gut microbiota composition and relative abundance in various neurological disorders. We performed a systematic review of the different microbiota altered in a wide range of neurological disorders (Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis, and stroke). Fifty-two studies were included representing 5496 patients. At the genus level, the most frequently involved microbiota are Akkermansia, Faecalibacterium, and Prevotella. The overlap between the pathologies was strongest for MS and PD, sharing eight genera (Akkermansia, Butyricicoccus, Bifidobacterium, Coprococcus, Dorea, Faecalibacterium, Parabacteroides, and Prevotella) and PD and stroke, sharing six genera (Enterococcus, Faecalibacterium, Lactobacillus, Parabacteroides, Prevotella, and Roseburia). The identification signatures overlapping for AD, PD, and MS raise the question of whether these reflect a common etiology or rather common consequence of these diseases. The interpretation is hampered by the low number and low power for AD, ALS, and stroke with ample opportunity for false positive and false negative findings.

Mixed Tree Nuts, Cognition, and Gut Microbiota: A 4-Week, Placebo-Controlled, Randomized Crossover Trial in Healthy Nonelderly Adults

BACKGROUND

Beneficial effects of nut supplementation on cognitive function have previously been demonstrated in young and older adults. Alterations to gut microbiota have also been shown following tree nut consumption. However, no data exists on the effects of nuts on cognition and intestinal microbial communities assessed within the same study.

OBJECTIVES

The study aimed to examine the effects of daily consumption of tree nuts for 4 wk on cognitive function (primary outcome), mood, metabolomics, and gut microbial species (secondary outcomes) in healthy, nonelderly adults.

METHODS

This randomized, placebo-controlled, double-blind, counterbalanced crossover study assessed the effects of 4 wk of supplementation with 30 g/d mixed tree nuts versus placebo on cognition and mood in 79 healthy adults aged 18-49 y. Metabolic responses, gut bacterial community structure, and the potential for these to impact cognition were explored using a multi-omic approach. Bacterial community analysis was conducted in Quantitative Insights Into Microbial Ecology 2 (QIIME2).

RESULTS

Mixed model analysis indicated that nut consumption led to significant improvements to accuracy (placebo M = 92.2% compared with NUTS M = 94.5%; P = 0.019) and speed of response (placebo M = 788 ms compared with NUTS M = 757 ms; P = 0.004) on a picture recognition task. No significant changes to bacterial community α or β diversity were observed when comparing nut consumption to the placebo arm. However, an unclassified Lachnospiraceae amplicon sequence variant (ASV) was significantly enriched in participants when supplemented with nuts (P = 0.015). No correlations were observed between the changes to picture recognition and the changes to the unclassified Lachnospiraceae ASV. There were no significant changes to the urinary metabolome.

CONCLUSIONS

These findings indicate a positive effect of nut on cognition following only 4 wk of consumption in a healthy nonelderly sample, as well as upregulation of a microbial taxa associated with gut health. The effects appear to be independent of one another, but further exploration is required in those experiencing cognitive decline and/or gut dysbiosis.

Gut microbiota and obesity

Worldwide, adults and childhood obesity are increasing alarmingly, being a major health problem. Obesity is correlated with an increased incidence of various systemic diseases including cancer, heart diseases, and diabetes mellitus type 2. Risk factors for obesity are dysbiosis, genetic, socioeconomic, behavioural and environmental. The gut microbiota has beneficial effects on human health, like host immune system stimulation, being influenced by pH, or nutrient intake. Studies performed on humans and animal models reported differences regarding microbiota at lean and obese individuals. The consumption of probiotics and prebiotics may balance the microbiota with positive effects in obesity. The main aim of this review is to reveal the interaction between dysbiosis and obesity

Modulation of gut microbiota by bioactive compounds for prevention and management of type 2 diabetes

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder characterized by hyperglycemia and insulin resistance. Gut microbiota (GM) are specific groups of microbes colonized in the gastrointestinal (GI) tract. They profoundly influence health, disease protection, and associated with metabolic activities, and play a vital role in the production of functional metabolites from dietary substances. Dysbiosis of GM has been linked to the onset of T2DM and can be altered to attain eubiosis by intervention with various nutritional bioactive compounds such as polyphenols, prebiotics, and probiotics. This review presents an overview of the evidence and underlying mechanisms by which bioactive compounds modulate the GM for the prevention and management of T2DM.

Neurovascular Dysfunction in Diverse Communities With Health Disparities-Contributions to Dementia and Alzheimer's Disease

Alzheimer's disease and related dementias (ADRD) are an expanding worldwide crisis. In the absence of scientific breakthroughs, the global prevalence of ADRD will continue to increase as more people are living longer. Racial or ethnic minority groups have an increased risk and incidence of ADRD and have often been neglected by the scientific research community. There is mounting evidence that vascular insults in the brain can initiate a series of biological events leading to neurodegeneration, cognitive impairment, and ADRD. We are a group of researchers interested in developing and expanding ADRD research, with an emphasis on vascular contributions to dementia, to serve our local diverse community. Toward this goal, the primary objective of this review was to investigate and better understand health disparities in Alabama and the contributions of the social determinants of health to those disparities, particularly in the context of vascular dysfunction in ADRD. Here, we explain the neurovascular dysfunction associated with Alzheimer's disease (AD) as well as the intrinsic and extrinsic risk factors contributing to dysfunction of the neurovascular unit (NVU). Next, we ascertain ethnoregional health disparities of individuals living in Alabama, as well as relevant vascular risk factors linked to AD. We also discuss current pharmaceutical and non-pharmaceutical treatment options for neurovascular dysfunction, mild cognitive impairment (MCI) and AD, including relevant studies and ongoing clinical trials. Overall, individuals in Alabama are adversely affected by social and structural determinants of health leading to health disparities, driven by rurality, ethnic minority status, and lower socioeconomic status (SES). In general, these communities have limited access to healthcare and healthy food and other amenities resulting in decreased opportunities for early diagnosis of and pharmaceutical treatments for ADRD. Although this review is focused on the current state of health disparities of ADRD patients in Alabama, future studies must include diversity of race, ethnicity, and region to best be able to treat all individuals affected by ADRD.

Fenofibrate Ameliorated Systemic and Retinal Inflammation and Modulated Gut Microbiota in High-Fat Diet-Induced Mice

Fenofibrate, as a lipid-lowering drug, has been reported to have a protective effect on the retina independent with plasma lipid levels. This study aimed to investigate that the ameliorative effects of fenofibrate on systemic and retinal inflammation, as well as gut microbiota dysbiosis in high-fat diet (HFD)-induced mice. C57BL/6J mice were randomly allocated into four groups: standard diet (SD) group; HFD group; SD plus fenofibrate (SD_ Fe) group; HFD plus fenofibrate (HFD_ Fe) group. After successfully establishing models (5 months), indicators associated with lipid, gut barrier, inflammation and gut microbiota were investigated. Our results showed that supplementing the HFD with fenofibrate decreased body weight gain, alleviated dyslipidemia and reversed the downregulation of short-chain fatty acid (SCFAs) in serum, retina and feces. Fenofibrate ameliorated intestinal barrier function damage in HFD-induced mice. Fenofibrate coadministration inhibited the levels of inflammatory factor and lipopolysaccharide (LPS) in the serum and attenuated inflammatory response in the retina of HFD-induced mice. Systemic LPS was positively correlated with a series of inflammatory factors in serum and retina, respectively. Fenofibrate supplementation down-regulated the abundances of LPS-associated bacteria in HFD mice, including Firmicutes and Proteobacteria at the phylum level, Desulfovibrionaceae at the family level, as well as unclassified_ Desulfovibrionaceae, Acetatifactor, Flavonifractor, Oscillibacter and Anaerotruncus at the genus level. However, fenofibrate treatment up-regulated the abundances of SCFA-associated bacteria in HFD mice, including Bacteroidetes at the phylum level, Porphyromonadaceae at the family level, as well as unclassified_Porphyromonadaceae, Barnesiella, Alloprevotella and Bifidobacterium at the genus level. In conclusion, our results confirmed fenofibrate could attenuate HFD-induced systemic and retinal inflammation, accompanying with restoration of intestinal barrier damage and modulation of gut microbiota/metabolites. This work provided an explanation for the ameliorative effects of fenofibrate on HFD-induced systemic and retinal inflammation might be partially related with the modulation of gut microbiota and its metabolites.

Metabolites of Gut Microbiota and Possible Implication in Development of Diabetes Mellitus

Diabetes mellitus is characterized by having a disorder of glucose metabolism. The types of diabetes mellitus include type 1 diabetes mellitus, type 2 diabetes mellitus, gestational diabetes mellitus, and other specific types of diabetes mellitus. Many risk factors contribute to diabetes mellitus mainly including genetics, environment, obesity, and diet. In the recent years, gut microbiota has been shown to be linked to the development of diabetes. It has been reported that the gut microbiota composition of diabetic patients is different from that of healthy people. Although the mechanism behind the abnormality remains to be explored, most hypotheses focus on the inflammation response and leaky gut in relation to the changes in production of endotoxins and metabolites derived from the intestinal flora. Consequently, the above-mentioned abnormalities trigger a series of metabolic changes, gradually leading to development of hyperglycemia, insulin resistance, and diabetes. This review is (i) to summarize the differences in gut microbiota between diabetic patients and healthy people, (ii) to discuss the underlying mechanism(s) by which how lipopolysaccharide, diet, and metabolites of the gut microbiota affect diabetes, and (iii) to provide a new insight in the prevention and treatment of diabetes.

Trialling a microbiome-targeted dietary intervention in children with ADHD-the rationale and a non-randomised feasibility study

Background

Dietary interventions have been previously explored in children with ADHD. Elimination diets and supplementation can produce beneficial behaviour changes, but little is known about the mechanisms mediating change. We propose that these interventions may work, in part, by causing changes in the gut microbiota. A microbiome-targeted dietary intervention was developed, and its feasibility assessed.

Methods

A non-randomised feasibility study was conducted on nine non-medicated children with ADHD, aged 8–13 years (mean 10.39 years), using a prospective one-group pre-test/post-test design. Participants were recruited from ADHD support groups in London and took part in the 6-week microbiome-targeted dietary intervention, which was specifically designed to impact the composition of gut bacteria. Children were assessed pre- and post-intervention on measures of ADHD symptomatology, cognition, sleep, gut function and stool-sample microbiome analysis. The primary aim was to assess the study completion rate, with secondary aims assessing adherence, adverse events (aiming for no severe and minimal), acceptability and suitability of outcome measures.

Results

Recruitment proved to be challenging and despite targeting 230 participants directly through support groups, and many more through social media, nine families (of the planned 10) signed up for the trial. The completion rate for the study was excellent at 100%. Exploration of secondary aims revealed that (1) adherence to each aspect of the dietary protocol was very good; (2) two mild adverse events were reported; (3) parents rated the treatment as having good acceptability; (4) data collection and outcome measures were broadly feasible for use in an RCT with a few suggestions recommended; (5) descriptive data for outcome measures is presented and suggests that further exploration of gut microbiota, ADHD symptoms and sleep would be helpful in future research.

Conclusions

This study provides preliminary evidence for the feasibility of a microbiome-targeted dietary intervention in children with ADHD. Recruitment was challenging, but the diet itself was well-tolerated and adherence was very good. Families wishing to trial this diet may find it an acceptable intervention. However, recruitment, even for this small pilot study, was challenging. Because of the difficulty experienced recruiting participants, future randomised controlled trials may wish to adopt a simpler dietary approach which requires less parental time and engagement, in order to recruit the number of participants required to make meaningful statistical interpretations of efficacy.

Trial registration

ClinicalTrials.gov Identifier: NCT03737877. Registered 13 November 2018—retrospectively registered, within 2 days of the first participant being recruited.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40814-022-01058-4.

Influence of Aging, Macronutrient Composition and Time-Restricted Feeding on the Fischer344 x Brown Norway Rat Gut Microbiota

Both ketogenic diets (KD) and time-restricted feeding (TRF) regimens have the ability to influence several parameters of physical health, including gut microbiome composition and circulating cytokine concentration. Moreover, both of these dietary interventions prevent common impairments associated with the aging process. However, significantly altering macronutrient intake, which is required for a KD, may be unappealing to individuals and decrease compliance to dietary treatments. In contrast to a KD, TRF allows individuals to continue eating the foods they are used to, and only requires a change in the time of day at which they eat. Therefore, we investigated both a KD and a diet with a more Western-like macronutrient profile in the context of TRF, and compared both diets to animals allowed access to standard chow ad libitum in young adult and aged rats. While limited effects on cytokine levels were observed, both methods of microbiome analysis (16S sequencing and metagenomics) indicate that TRF and KDs significantly altered the gut microbiome in aged rats. These changes were largely dependent on changes to feeding paradigm (TRF vs. ad libitum) alone regardless of macronutrient content for many gut microbiota, but there were also macronutrient-specific changes. Specifically, functional analysis indicates significant differences in several pathways, including those involved in the tricarboxylic acid (TCA) cycle, carbohydrate metabolism and neurodegenerative disease. These data indicate that age- and disease-related gut dysbiosis may be ameliorated through the use of TRF with both standard diets and KDs.

Dietary fiber combinations to mitigate the metabolic, microbial, and cognitive imbalances resulting from diet-induced obesity in rats

Dietary fiber promotes a healthy gut microbiome and shows promise in attenuating the unfavorable microbial changes resulting from a high-fat/sucrose (HFS) diet. High-fiber diets consisting of oligofructose alone (HFS/O) or in combination with β-glucan (HFS/OB), resistant starch (HFS/OR), or β-glucan and resistant starch (HFS/OBR) were fed to diet-induced obese rats for 8 weeks to determine if these fibers could attenuate the obese phenotype. Only the HFS/O group displayed a decrease in body weight and body fat, but all fiber interventions improved insulin sensitivity and cognitive function. The HFS/O diet was the least effective at improving cognitive function and only the HFS/OB group showed improvements in glucose tolerance, thus highlighting the differential effects of fiber types. Hippocampal cytokines (IL-6, IL-10) were more pronounced in the HFS/OB group which coincided with the most time spend in the open arms of the elevated plus maze. All fiber groups showed an increase in beneficial Bifidobacterium and Lactobacillus abundance while the HFS group showed higher abundance of Clostridium. Fecal microbiota transplant from fiber-treated rats into germ-free mice did not alter body composition in the mice but did result in a higher abundance of Bacteroides in the HFS/O and HFS/OB groups compared to HFS. The HFS/OB recipient mice also had higher insulin sensitivity compared to the other groups. This study highlights the influence of dietary fiber type on metabolic and cognitive outcomes suggesting that the type of supplementation (single or combined fibers) could be tailored to specific targeted outcomes.

The Role of Gut Microbiota in Neuropsychiatric Diseases – Creation of An Atlas-Based on Quantified Evidence

There is a growing body of evidence highlighting the significant role of gut microbiota in various pathologies. We performed a systematic review to review the different microbiota involved in neuropsychiatric diseases. 50 studies (23 studies for autism spectrum disorders, 18 for major depression, and 9 for schizophrenia), representing 2,137 patients and 2,844 controls. Concerning the microbiota, the genera Prevotella, Clostridium, Bacteroides, Bifidobacterium, Ruminococcus, Megamonas, and Faecalbacterium were the ones detected with the most frequent variation of their relatives abundance. We also assess the overlap between the different pathologies. This study provides new insights into the complex relationship between the brain and the gut and the implications in neuropsychiatric pathologies. The identification of unique signatures in neuropsychiatric diseases suggests new possibilities in targeted anti or probiotic treatment.

Effects of prenatal nutrient supplementation and early life exposures on neurodevelopment at age 10: a randomised controlled trial - the COPSYCH study protocol

INTRODUCTION

Nutrient deficiency and immune and inflammatory disturbances in early life may compromise neurodevelopment and be implicated in the aetiology of psychiatric disorders. However, current evidence is limited by its predominantly observational nature. COpenhagen Prospective Study on Neuro-PSYCHiatric Development (COPSYCH) is a research alliance between Copenhagen Prospective Studies on Asthma in Childhood (COPSAC) and Center for Clinical Intervention and Neuropsychiatric Schizophrenia Research with the overall aim to investigate effects of prenatal and early life exposures on neurodevelopment at 10 years. COPSYCH will investigate the impact of prenatal n-3 long-chain polyunsaturated fatty acids (n-3 LCPUFA) and high-dose vitamin D supplementation on neurodevelopment reflected by brain development, neurocognition and psychopathology. Moreover, the neurodevelopmental impact of early life exposures such as infections, low grade inflammation and the gut microbiome will be scrutinised.

METHODS AND ANALYSIS

COPSYCH is based on the prospective and ongoing COPSAC2010 birth cohort of 700 mother-child pairs. Randomised controlled trials of supplementation with n-3 LCPUFA and/or high-dose vitamin D or placebo in the third trimester were embedded in a factorial 2×2 design (ClinicalTrials.gov: NCT01233297 and NCT00856947). This unique cohort provides deep phenotyping data from 14 previous clinical follow-up visits and exposure assessments since birth. The ongoing 10-year visit is a 2-day visit. Day 1 includes a comprehensive neurocognitive examination, and assessment of psychopathological dimensions, and assessment of categorical psychopathology. Day 2 includes acquisition of brain structural, diffusion and functional sequences using 3 Tesla MRI. Study outcomes are neurocognitive, psychopathological and MRI measures.

ETHICS AND DISSEMINATION

This study has been approved by the Danish National Committee on Health Research Ethics and The Danish Data Protection Agency. The study is conducted in accordance with the guiding principles of the Declaration of Helsinki. Parents gave written informed consent before enrolment.

Dietary Correlates of Oral and Gut Microbiota in the Water Monitor Lizard, Varanus salvator (Laurenti, 1768)

Numerous studies have demonstrated that food shapes the structure and composition of the host’s oral and gut microbiota. The disorder of oral and gut microbiota may trigger various host diseases. Here, we collected oral and gut samples from wild water monitor lizards (Varanus salvator) and their captive conspecifics fed with bullfrogs, eggs, and depilated chicken, aiming to examine dietary correlates of oral and gut microbiota. We used the 16S rRNA gene sequencing technology to analyze the composition of the microbiota. Proteobacteria and Bacteroidota were the dominant phyla in the oral microbiota, and so were in the gut microbiota. The alpha diversity of microbiota was significantly higher in the gut than in the oral cavity, and the alpha diversity of oral microbiota was higher in captive lizards than in wild conspecifics. Comparing the relative abundance of oral and gut bacteria and their gene functions, differences among different animal groups presumably resulted from human contact in artificial breeding environments and complex food processing. Differences in gene function might be related to the absolute number and/or the taxonomic abundance of oral and gut microorganisms in the wild and the water environment. This study provides not only basic information about the oral and gut microbiota of captive and wild water monitor lizards, but also an inference that feeding on frogs and aquatic products and reducing human exposure help water monitor lizards maintain a microbiota similar to that in the wild environment.

Gut Microbiome and Plasma Metabolome Signatures in Middle-Aged Mice With Cognitive Dysfunction Induced by Chronic Neuropathic Pain

Patients with chronic neuropathic pain (CNP) often complain about their terrible memory, especially the speed of information processing. Accumulating evidence suggests a possible link between gut microbiota and pain processing as well as cognitive function via the microbiota-gut-brain axis. This study aimed at exploring the fecal microbiome and plasma metabolite profiles in middle-aged spared nerve injury (SNI) mice model with cognitive dysfunction (CD) induced by CNP. The hierarchical cluster analysis of performance in the Morris water maze test was used to classify SNI mice with CD or without CD [i.e., non-CD (NCD)] phenotype. 16S rRNA sequencing revealed a lower diversity of gut bacteria in SNI mice, and the increase of Actinobacteria, Proteus, and Bifidobacterium might contribute to the cognitive impairment in the CNP condition. The plasma metabolome analysis showed that the endocannabinoid (eCB) system, disturbances of lipids, and amino acid metabolism might be the dominant signatures of CD mice. The fecal microbiota transplantation of the Sham (not CD) group improved allodynia and cognitive performance in pseudo-germ-free mice via normalizing the mRNA expression of eCB receptors, such as cn1r, cn2r, and htr1a, reflecting the effects of gut bacteria on metabolic activity. Collectively, the findings of this study suggest that the modulation of gut microbiota and eCB signaling may serve as therapeutic targets for cognitive deficits in patients with CNP.

Effects of Bifidobacterium Lactis BS01 and Lactobacillus Acidophilus LA02 on cognitive functioning in healthy women

A growing body of research studies the relationship between probiotic bacteria in the gut and the host organism, including the impact on cognitive functioning. Data from human studies are scarce; however, recent studies point toward the beneficial role of probiotics for cognitive functioning. One of the mechanisms involved in this relationship is the probiotic's ability to influence inflammation and immune response. The aim of this initial study was to investigate the effects of probiotic supplementation with Bifidobacterium Lactis BS01 and Lactobacillus Acidophilus LA02 on cognitive functioning in healthy, young adult females. A total of 53 participants aged 19-31 were enrolled, and 38 completed the trial. A 6-week probiotic or placebo treatment was conducted. Five measures of cognitive functioning were applied pre- and post-treatment. Both groups showed general improvement at the second assessment. Contrary to our hypothesis, the placebo group improved slightly, but significantly, in four out of five measures of cognitive functioning, with the exception of the Wisconsin Card Sorting Test (WCST). The supplementation group improved significantly in two measures of the WCST, compared to the placebo group. Similar results have been previously reported. Probiotic supplementation, while not harmful, might not be beneficial for cognition in the healthy population, or at least not universally.

Dietary supplementation with Ceriporia lacerata improves learning and memory in a scopolamine-induced amnesia mouse model

Ceriporia lacerata (CL) is a species of white rot fungi. In this study, we have examined the beneficial effect of CL on scopolamine-induced memory impairment in mice. A freeze-dried CL mycelial culture broth was dissolved and orally administered to scopolamine-treated C57BL/6J mice followed by behavioral tests using the Y-maze, passive avoidance, and Morris water maze tasks. CL administration at a daily dose of 200 mg/kg body weight resulted in restoration of exploration reduction and improvement of associative and spatial learning and memory impairment in scopolamine-treated mice. Concomitantly, heme oxygenase-1 was highly expressed in the hippocampal region of CL-administered mice. Moreover, the ethanolic extract of CL significantly increased the transcriptional activity of antioxidant response element and attenuated the glutamate-induced cytotoxicity in HT22 mouse hippocampal neuronal cells. These findings suggest that the CL intake can confer a beneficial effect on learning and memory presumably through protecting hippocampal neuronal cells from oxidative stress-induced damage.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10068-021-00945-5.