Fermented milk of Lactobacillus helveticus IDCC3801 improves cognitive functioning during cognitive fatigue tests in healthy older adults

Fibre & fermented foods: differential effects on the microbiota-gut-brain axis

The ability to manipulate brain function through the communication between the microorganisms in the gastrointestinal tract and the brain along the gut-brain axis has emerged as a potential option to improve cognitive and emotional health. Dietary composition and patterns have demonstrated a robust capacity to modulate the microbiota-gut-brain axis. With their potential to possess pre-, pro-, post-, and synbiotic properties, dietary fibre and fermented foods stand out as potent shapers of the gut microbiota and subsequent signalling to the brain. Despite this potential, few studies have directly examined the mechanisms that might explain the beneficial action of dietary fibre and fermented foods on the microbiota-gut-brain axis, thus limiting insight and treatments for brain dysfunction. Herein, we evaluate the differential effects of dietary fibre and fermented foods from whole food sources on cognitive and emotional functioning. Potential mediating effects of dietary fibre and fermented foods on brain health via the microbiota-gut-brain axis are described. Although more multimodal research that combines psychological assessments and biological sampling to compare each food type is needed, the evidence accumulated to date suggests that dietary fibre, fermented foods, and/or their combination within a psychobiotic diet can be a cost-effective and convenient approach to improve cognitive and emotional functioning across the lifespan.

Synbiotic supplementation may globally improve non-motor symptoms in patients with stable Parkinson's disease: results from an open label single-arm study

Gut microbiota changes and brain-gut-axis (BGA) dysregulation are common in people with Parkinson's Disease (PD). Probiotics and prebiotics are emerging as a potential therapeutic approach for PD patients. The aim of this paper was to assess the neurological and gastroenterological effects in PD patients with constipation after the administration of a synbiotic product, with a focus on behavioral and cognitive symptoms. We enrolled patients with stable PD who met diagnostic criteria for functional constipation and/or irritable bowel syndrome with constipation according to Rome IV Criteria. Patients received a synbiotic treatment (Enterolactis Duo, containing the probiotic strain Lacticaseibacillus paracasei DG and the prebiotic fiber inulin) for 12 weeks. A neurological and a gastroenterological evaluation were collected before and after the treatment. In addition, 16S rRNA gene profiling and short chain fatty acid quantification were performed to characterize the microbial ecosystem of fecal samples collected before (n = 22) and after (n = 9) the synbiotic administration. 30 patients were consecutively enrolled. After treatment, patients performed better in MDS-UPDRS part 1 (p = 0.000), SCOPA-AUT (p = 0.001), TAS-20 (p = 0.014), HAM-D (p = 0.026), DIFt (p = 0.003), PAS-A (p = 0.048). Gastroenterological evaluations showed improvements in PAC-SYM score (p < 0.001), number of complete bowel movement (p < 0.001) and BSFS (p < 0.001). After the synbiotic administration, we observed a significant increase in the abundance of the order Oscillospirales, as well as the Oscillospiraceae family and the species Faecalibacterium prausnitzii within this order in fecal samples. Synbiotic treatment demonstrates potential efficacy in ameliorating non-motor features in PD patients.

Psychobiotic Properties of Lactiplantibacillus plantarum in Neurodegenerative Diseases

Neurodegenerative disorders are the main cause of cognitive and physical disabilities, affect millions of people worldwide, and their incidence is on the rise. Emerging evidence pinpoints a disturbance of the communication of the gut-brain axis, and in particular to gut microbial dysbiosis, as one of the contributors to the pathogenesis of these diseases. In fact, dysbiosis has been associated with neuro-inflammatory processes, hyperactivation of the neuronal immune system, impaired cognitive functions, aging, depression, sleeping disorders, and anxiety. With the rapid advance in metagenomics, metabolomics, and big data analysis, together with a multidisciplinary approach, a new horizon has just emerged in the fields of translational neurodegenerative disease. In fact, recent studies focusing on taxonomic profiling and leaky gut in the pathogenesis of neurodegenerative disorders are not only shedding light on an overlooked field but are also creating opportunities for biomarker discovery and development of new therapeutic and adjuvant strategies to treat these disorders. Lactiplantibacillus plantarum (LBP) strains are emerging as promising psychobiotics for the treatment of these diseases. In fact, LBP strains are able to promote eubiosis, increase the enrichment of bacteria producing beneficial metabolites such as short-chain fatty acids, boost the production of neurotransmitters, and support the homeostasis of the gut-brain axis. In this review, we summarize the current knowledge on the role of the gut microbiota in the pathogenesis of neurodegenerative disorders with a particular focus on the benefits of LBP strains in Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, autism, anxiety, and depression.

The brain-gut axis: communication mechanisms and the role of the microbiome as a neuroprotective factor in the development of neurodegenerative diseases: A literature overview

The study of the brain-gut axis and its impact on cognitive function and in the development of neurodegenerative diseases is a very timely topic of interest to researchers. This review summarizes information on the basic mechanisms of gut-brain communication. We then discuss the roles of the gut microbiome as a neuroprotective factor in neurodegeneration. The gut microbiota is extremely important in maintaining the body's homeostasis, shaping the human immune system and the proper functioning of the brain. The intestinal microflora affects the processes of neuroplasticity, synaptogenesis, and neuronal regeneration. This review aims to explain changes in the composition of the bacterial population of the intestinal microflora among patients with Alzheimer's disease, Parkinson's disease, and multiple sclerosis. Abnormalities in gut microflora composition are also noted in stress, depression, or autism spectrum development. New observations on psychobiotic supplementation in alleviating the symptoms of neurodegenerative diseases are also presented.

Survival of Probiotic Bacterial Cells in the Upper Gastrointestinal Tract and the Effect of the Surviving Population on the Colonic Microbial Community Activity and Composition

Many health-promoting effects have been attributed to the intake of probiotic cells. However, it is important that probiotic cells arrive at the site of their activity in a viable state in order to exert their beneficial effects. Careful selection of the appropriate probiotic formulation is therefore required as mainly the type of probiotic species/strain and the administration strategy may affect survival of the probiotic cells during the upper gastrointestinal (GIT) passage. Therefore, the current study implemented Simulator of the Human Microbial Ecosystem (SHIME®) technology to investigate the efficacy of different commercially available probiotic formulations on the survival and culturability of probiotic bacteria during upper GIT passage. Moreover, Colon-on-a-Plate (CoaP™) technology was applied to assess the effect of the surviving probiotic bacteria on the gut microbial community (activity and composition) of three human donors. Significantly greater survival and culturability rates were reported for the delayed-release capsule formulation (>50%) as compared to the powder, liquid, and standard capsule formulations (<1%) (p < 0.05), indicating that the delayed-release capsule was most efficacious in delivering live bacteria cells. Indeed, administration of the delayed-release capsule probiotic digest resulted in enhanced production of SCFAs and shifted gut microbial community composition towards beneficial bacterial species. These results thus indicate that careful selection of the appropriate probiotic formulation and administration strategy is crucial to deliver probiotic cells in a viable state at the site of their activity (distal ileum and colon).

Probiotics and Paraprobiotics: Effects on Microbiota-Gut-Brain Axis and Their Consequent Potential in Neuropsychiatric Therapy

Neuropsychiatric disorders are clinical conditions that affect cognitive function and emotional stability, often resulting from damage or disease in the central nervous system (CNS). These disorders are a worldwide concern, impacting approximately 12.5% of the global population. The gut microbiota has been linked to neurological development and function, implicating its involvement in neuropsychiatric conditions. Due to their interaction with gut microbial communities, probiotics offer a natural alternative to traditional treatments such as therapeutic drugs and interventions for alleviating neuropsychiatric symptoms. Introduced by Metchnikoff in the early 1900s, probiotics are live microorganisms that provide various health benefits, including improved digestion, enhanced sleep quality, and reduced mental problems. However, concerns about their safety, particularly in immunocompromised patients, warrant further investigation; this has led to the concept of "paraprobiotics", inactivated forms of beneficial microorganisms that offer a safer alternative. This review begins by exploring different methods of inactivation, each targeting specific cellular components like DNA or proteins. The choice of inactivation method is crucial, as the health benefits may vary depending on the conditions employed for inactivation. The subsequent sections focus on the potential mechanisms of action and specific applications of probiotics and paraprobiotics in neuropsychiatric therapy. Probiotics and paraprobiotics interact with gut microbes, modulating the gut microbial composition and alleviating gut dysbiosis. The resulting neuropsychiatric benefits primarily stem from the gut-brain axis, a bidirectional communication channel involving various pathways discussed in the review. While further research is needed, probiotics and paraprobiotics are promising therapeutic agents for the management of neuropsychiatric disorders.

Feeding gut microbes to nourish the brain: unravelling the diet-microbiota-gut-brain axis

The prevalence of brain disorders, including stress-related neuropsychiatric disorders and conditions with cognitive dysfunction, is rising. Poor dietary habits contribute substantially to this accelerating trend. Conversely, healthy dietary intake supports mood and cognitive performance. Recently, the communication between the microorganisms within the gastrointestinal tract and the brain along the gut-brain axis has gained prominence as a potential tractable target to modulate brain health. The composition and function of the gut microbiota is robustly influenced by dietary factors to alter gut-brain signalling. To reflect this interconnection between diet, gut microbiota and brain functioning, we propose that a diet-microbiota-gut-brain axis exists that underpins health and well-being. In this Review, we provide a comprehensive overview of the interplay between diet and gut microbiota composition and function and the implications for cognition and emotional functioning. Important diet-induced effects on the gut microbiota for the development, prevention and maintenance of neuropsychiatric disorders are described. The diet-microbiota-gut-brain axis represents an uncharted frontier for brain health diagnostics and therapeutics across the lifespan.

Psychobiotics for Mitigation of Neuro-Degenerative Diseases: Recent Advancements

Ageing is inevitable and poses a universal challenge for all living organisms, including humans. The human body experiences rapid cell division and metabolism until approximately 25 years of age, after which the accumulation of metabolic by-products and cellular damage leads to age-related diseases. Neurodegenerative diseases are of concern due to their irreversible nature, lack of effective treatment, and impact on society and the economy. Researchers are interested in finding drugs that can effectively alleviate ageing and age-related diseases without side-effects. Psychobiotics are a novel class of probiotic organisms and prebiotic interventions that confer mental health benefits to the host when taken appropriately. Psychobiotic strains affect functions related to the central nervous system (CNS) and behaviors mediated by the Gut-Brain-Axis (GBA) through various pathways. There is an increasing interest in researchers of these microbial-based psychopharmaceuticals. Psychobiotics have been reported to reduce neuronal ageing, inflammation, oxidative stress, and cortisol levels; increase synaptic plasticity and levels of neurotransmitters and antioxidants. The present review focuses on the manifestation of elderly neurodegenerative and mental disorders, particularly Alzheimer's disease (AD), Parkinson's disease (PD), and depression, and the current status of their potential alleviation through psychobiotic interventions, highlighting their possible mechanisms of action.

Cognitive and Emotional Effect of a Multi-species Probiotic Containing Lactobacillus rhamnosus and Bifidobacterium lactis in Healthy Older Adults: A Double-Blind Randomized Placebo-Controlled Crossover Trial

As the population ages, cognitive decline becomes more common. Strategies targeting the gut-brain axis using probiotics are emerging to achieve improvements in neuropsychiatric and neurological disorders. However, the beneficial role of probiotics on brain function in healthy older adults remains unclear. Our aim was to evaluate a multi-species probiotic formulation as a therapeutic approach to reduce emotional and cognitive decline associated with aging in healthy adults. A randomized double-blind placebo-controlled crossover trial was conducted. The study involved a 10-week intervention where participants consumed the assigned probiotic product daily, followed by a 4-week washout period before the second condition started. Cognitive function was assessed using the Mini-Mental State Examination (MMSE) and the Psychological Experiments Construction Language Test Battery. At the emotional level, the Beck Depression Inventory (BDI) and the State-Trait Anxiety Inventory (STAI) were used. Thirty-three participants, recruited between July 2020 and April 2022, ingested a multispecies probiotic (Lactobacillus rhamnosus and Bifidobacterium lactis). After the intervention, noticeable enhancements were observed in cognitive function (mean difference 1.90, 95% CI 1.09 to 2.70, p < 0.005), memory (mean difference 4.60, 95% CI 2.91 to 6.29, p < 0.005) by MMSE and digit task, and depressive symptoms (mean difference 4.09, 95% CI 1.70 to 6.48, p < 0.005) by BDI. Furthermore, there were significant improvements observed in planning and problem-solving skills, selective attention, cognitive flexibility, impulsivity, and inhibitory ability. Probiotics administration improved cognitive and emotional function in older adults. Limited research supports this, requiring more scientific evidence for probiotics as an effective therapy for cognitive decline. This study has been prospectively registered at ClinicalTrials.gov (NCT04828421; 2020/July/17).

An altered gut microbiome in pre-eclampsia: cause or consequence

Hypertensive disorders of pregnancy, including pre-eclampsia, are a leading cause of serious and debilitating complications that affect both the mother and the fetus. Despite the occurrence and the health implications of these disorders there is still relatively limited evidence on the molecular underpinnings of the pathophysiology. An area that has come to the fore with regard to its influence on health and disease is the microbiome. While there are several microbiome niches on and within the body, the distal end of the gut harbors the largest of these impacting on many different systems of the body including the central nervous system, the immune system, and the reproductive system. While the role of the microbiome in hypertensive disorders, including pre-eclampsia, has not been fully elucidated some studies have indicated that several of the symptoms of these disorders are linked to an altered gut microbiome. In this review, we examine both pre-eclampsia and microbiome literature to summarize the current knowledge on whether the microbiome drives the symptoms of pre-eclampsia or if the aberrant microbiome is a consequence of this condition. Despite the paucity of studies, obvious gut microbiome changes have been noted in women with pre-eclampsia and the individual symptoms associated with the condition. Yet further research is required to fully elucidate the role of the microbiome and the significance it plays in the development of the symptoms. Regardless of this, the literature highlights the potential for a microbiome targeted intervention such as dietary changes or prebiotic and probiotics to reduce the impact of some aspects of these disorders.

The influence of the gut-brain axis on anxiety and depression: A review of the literature on the use of probiotics

This review aims to argue how using probiotics can improve anxiety and depressive behaviour without adverse effects, also exploring the impact of postbiotics on it. Specifically, probiotics have drawn more attention as effective alternative treatments, considering the rising cost of antidepressant and anti-anxiety drugs and the high risk of side effects. Depression and anxiety disorders are among the most common mental illnesses in the world's population, characterised by low mood, poor general interest, and cognitive or motor dysfunction. Thus, this study analysed published literature on anxiety, depression, and probiotic supplementation from PubMed and Scopus, focusing on the last twenty years. This study focused on the effect of probiotics on mental health as they have drawn more attention because of their extensive clinical applications and positive impact on various diseases. Numerous studies have demonstrated how the gut microbiota might be critical for mood regulation and how probiotics can affect host health by regulating the gut-brain axis. By comparing the different works analysed, it was possible to identify a strategy by which they are selected and employed and, at the same time, to assess how the effect of probiotics can be optimised using postbiotics, an innovation to improve mental well-being in humans.

Fermented foods: Harnessing their potential to modulate the microbiota-gut-brain axis for mental health

Over the past two decades, whole food supplementation strategies have been leveraged to target mental health. In addition, there has been increasing attention on the ability of gut microbes, so called psychobiotics, to positively impact behaviour though the microbiota-gut-brain axis. Fermented foods offer themselves as a combined whole food microbiota modulating intervention. Indeed, they contain potentially beneficial microbes, microbial metabolites and other bioactives, which are being harnessed to target the microbiota-gut-brain axis for positive benefits. This review highlights the diverse nature of fermented foods in terms of the raw materials used and type of fermentation employed, and summarises their potential to shape composition of the gut microbiota, the gut to brain communication pathways including the immune system and, ultimately, modulate the microbiota-gut-brain axis. Throughout, we identify knowledge gaps and challenges faced in designing human studies for investigating the mental health-promoting potential of individual fermented foods or components thereof. Importantly, we also suggest solutions that can advance understanding of the therapeutic merit of fermented foods to modulate the microbiota-gut-brain axis.

Adjuvant administration of probiotic effects on sexual function in depressant women undergoing SSRIs treatment: a double-blinded randomized controlled trial

BACKGROUND

According to the Institute of Health Metrics and Evaluation's Global Health Data Exchange (2023) it is estimated that 5% of all adults will experience depressive disorder. Amongst the general loss of pleasure and interest in everyday activities that are symptoms of low mood, reduced sexual desire and sexual dysfunction can be particularly overlooked. Human sexuality is complex, but finding solutions based on scientific evidence to limit the symptoms of depressive disorder and the iatrogenic impact of antidepressant treatment to improve this outcome is an important step in promoting psychological health and general wellbeing.

OBJECTIVE

The present study aimed is to provide scientific evidence to assess the effect of oral probiotic on sexual function in women with depressive disorder treated with Selective Serotonin Reuptake Inhibitors (SSRIs) in an Iranian population.

DESIGN

This study was a double-blind randomized clinical trial. Eligible women were assigned to lactofem plus SSRIs (n = 58) or SSRIs alone (n = 54). In group A, SSRI antidepressants were prescribed together with Lactofem, and in group B, SSRI antidepressants were prescribed alone. Lactofem including Lactobacillus acidophilus 2 × 109 cfu/g, Bifidobacterium bifidus 2 × 109 cfu/g, Lactobacillus rutri 2 × 109 cfu/g, Lactobacillus fermentum 2 × 109 cfu/g; capsule weight of 500 mg bio-capsule administered orally and daily. The duration of intervention in two groups was two months. All questionnaires were completed by the patients before and after the intervention. The Female Sexual Function Index (FSFI), Hamilton Depression Rating Scale and Larson's Sexual Satisfaction Questionnaire were used to evaluate sexual function, severity of depressive disorder and sexual satisfaction, respectively.

RESULTS

Based on the results of the present study, there was a statistically significant difference in sexual satisfaction and severity of depressive disorder between the groups before and after the intervention (P < 0.05). Also, our findings showed that after eight weeks, the Lactofem plus SSRIs group showed significant improvement in FSFI domains and total scores compared to SSRIs alone group (P < 0.05).

CONCLUSIONS

The results of the present study show that taking probiotics for eight weeks may improve the severity of depressive disorder, sexual function and sexual satisfaction in depressed women treated with SSRIs.

TRIAL REGISTRATION

ClinicalTrials.govidentifier: IRCT20160524028038N14 (19/12/2022).

An updated overview on the relationship between human gut microbiome dysbiosis and psychiatric and psychological disorders

There is a lot of evidence establishing that nervous system development is related to the composition and functions of the gut microbiome. In addition, the central nervous system (CNS) controls the imbalance of the intestinal microbiota, constituting a bidirectional communication system. At present, various gut-brain crosstalk routes have been described, including immune, endocrine and neural circuits via the vagal pathway. Several empirical data have associated gut microbiota alterations (dysbiosis) with neuropsychiatric diseases, such as Alzheimer's disease, autism and Parkinson's disease, and with other psychological disorders, like anxiety and depression. Fecal microbiota transplantation (FMT) therapy has shown that the gut microbiota can transfer behavioral features to recipient animals, which provides strong evidence to establish a causal-effect relationship. Interventions, based on prebiotics, probiotics or synbiotics, have demonstrated an important influence of microbiota on neurological disorders by the synthesis of neuroactive compounds that interact with the nervous system and by the regulation of inflammatory and endocrine processes. Further research is needed to demonstrate the influence of gut microbiota dysbiosis on psychiatric and psychological disorders, and how microbiota-based interventions may be used as potential therapeutic tools.

The Relationship Between Fermented Dairy Consumption with Cognitive Function Among Older US Adults: Data from the NHANES 2011-2014

Background

The aging global population has led to an increased burden of cognitive impairment in older adults.

Objective

This study examined the relationship between fermented dairy intake and cognitive function in this population.

Methods

Yogurt, cheese, and fermented dairy consumption were assessed through two 24-hour dietary recall interviews, categorized into low, medium, and high intake groups. Multivariate linear regression was employed to examine the relationship between fermented dairy intake and cognitive tests, including the Alzheimer's Disease Word Learning Immediate Recall Test (CERAD-IRT), CERAD Delayed Recall Test (CERAD-DRT), Animal Fluency Test (AFT), Digit Symbol Substitution Test (DSST), and global cognitive z-scores, adjusting for potential confounding factors.

Results

The study comprised 2,462 participants (average age 69.34±6.75 years, 52.07% female). Among yogurt consumers, global cognition and AFT z-scores are notably higher than non-consumers. Conversely, individuals who consume cheese display significantly lower CERAD-DRT z-scores. Compared to participants not intake fermented dairy, consumers of fermented dairy show significantly higher AFT and DSST z-scores and lower CERAD-DRT z-scores. Moreover, when categorizing individuals based on their intake of fermented dairy, those with low and medium consumption show significantly higher AFT and DSST z-scores, as well as significantly lower CERAD-DRT z-scores compared to non-consumers.

Conclusions

Our study suggests that moderate consumption of fermented dairy products is associated with better executive function and verbal fluency in the elderly.

Probiotics supplementation and brain-derived neurotrophic factor (BDNF): a systematic review and meta-analysis of randomized controlled trials

BACKGROUND AND AIMS

An emerging body of evidence has demonstrated the beneficial effects of probiotics on various mental health conditions. In this systematic review and meta-analysis, we sought to examine the effects of probiotics supplementation on brain-derived neurotrophic factor (BDNF) in adults.

METHODS

PubMed, Scopus, ISI Web of Science, and the Cochrane Library were searched, from database inception to April 2021, for eligible randomized controlled trials (RCTs). We pooled mean differences and standard deviations from RCTs using random-effect models.

RESULTS

Overall, meta-analysis of 11 trials (n = 648 participants) showed no significant changes in serum level of BDNF following probiotics. However, subgroup analysis revealed that probiotics increased BDNF levels in individuals suffering from neurological disorders (n = 214 participants; WMD = 3.08 ng/mL, 95% CI: 1.83, 4.34; P = 0.001; I2 = 7.5%; P-heterogeneity 0.34), or depression (n = 268 participants; WMD = 0.77 ng/mL, 95% CI: 0.07, 1.47; P = 0.032; I2 = 88.4%; P-heterogeneity < 0.001). Furthermore, a significant increase in BDNF levels was found in studies that administered the mixture of Lactobacillus and Bifidobacterium genera, and were conducted in Asia .

CONCLUSION

Our main findings suggest that probiotics may be effective in elevating BDNF levels in patients with depression and neurological disorders, and a mixed of Lactobacillus and Bifidobacterium appear to show greater efficacy than the single genus supplement. The low quality of evidence reduces clinical advocacy, and indicates that more large-scale, high-quality, RCTs are needed to facilitate reliable conclusions.

Effectiveness of Fish Roe, Snow Fungus, and Yeast Supplementation for Cognitive Function: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial

The brain is one of the most critical organs in the human body, regulating functions such as thinking, memory, learning, and perception. Studies have indicated that fish roe, snow fungus, and yeast may have the potential to modulate cognitive, memory, and emotional functions. However, more relevant clinical research in this area still needs to be conducted. This study explored the cognition-enhancing potential of a formula beverage including fish roe, snow fungus, and yeast. Sixty-four subjects were divided into a placebo group (n = 32) and a formula-drink group (n = 32), who consumed the product for 8 weeks. Cognitive tests were administered and analyzed at weeks 0, 4, and 8. After 4 and 8 weeks, there was a significant increase in the number of memory cards, and the response times among those who consumed the formula beverage were significantly faster than those in the placebo group. The subjects remembered the old items better and were more impressed with similar items based on the week effect. There was a significant increase in the cue effect of happy facial expressions after the subjects consumed the formula beverage for 8 weeks. In addition, there was a significant decrease in anxiety and fatigue, and improved quality of life. This formula beverage is a promising option that could be used to prevent further cognitive decline in adults with subjective cognitive complaints.

Effects of human probiotics on memory and psychological and physical measures in community-dwelling older adults with normal and mildly impaired cognition: results of a bi-center, double-blind, randomized, and placebo-controlled clinical trial (CleverAge biota)

Objectives

This study presents results of our randomized clinical trial studying the effect of human probiotics on memory and psychological and physical measures following our study protocol registered at clinicaltrials.gov NCT05051501 and described in detail in our previous paper.

Methods

Community dwelling participants aged between 55 and 80  years were randomly assigned to receive a single dose of 10⁶ colony-forming units of human Streptococcus thermophilus GH, Streptococcus salivarius GH NEXARS, Lactobacilus plantarum GH, and Pediococcus pentosaceus GH or placebo. A cross-over design allowed each group to receive probiotics and placebo for 3  months each in reverse order. A small subset of participants was examined online due to the COVID-19 pandemic. After 6  months a small number of volunteers were additionally assessed after 2  months without any intervention. Primary outcome measures included changes in cognitive functions assessed using brief tests and a neuropsychological battery and changes in mood assessed using validated questionnaires. Secondary outcome measures included changes in self-report and subjective measures using depression and anxiety questionnaires, seven visual analog scales of subjective feelings (memory, digestion, etc.), and physical performance.

Results

At baseline, the probiotic-placebo group A (n = 40, age 69 ± 7 years, education 16 ± 3 years, 63% females, body mass index 28.5 ± 6, subjective memory complaint in 43%) did not differ from the placebo-probiotic group B (n = 32) in any of the sociodemographic characteristics and evaluated measures including cognitive status. At follow-up visits after 3, 6, and 8  months, no cross-sectional differences in any of the measures were found between the groups except worse sentence recall of the ALBA test after 3  months of probiotic use. Score changes were not observed for all cognitive tests but one in any group between visits 1 and 3 and between visits 3 and 6. The only change was observed for the TMT B test after the first three months but no change was observed after the second three months.

Conclusion

The treatment with human probiotics and prebiotics did not improve cognitive, affective, or physical measures in community-dwelling individuals with normal or mildly impaired cognitive functions.

Clinical trial registration

clinicaltrials.gov, identifier NCT05051501.

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.

Gut Microbiota and Aging: Traditional Chinese Medicine and Modern Medicine

The changing composition of gut microbiota, much like aging, accompanies people throughout their lives, and the inextricable relationship between both has recently attracted extensive attention as well. Modern medical research has revealed that a series of changes in gut microbiota are involved in the aging process of organisms, which may be because gut microbiota modulates aging-related changes related to innate immunity and cognitive function. At present, there is no definite and effective method to delay aging. However, Nobel laureate Tu Youyou's research on artemisinin has inspired researchers to study the importance of Traditional Chinese Medicine (TCM). TCM, as an ancient alternative medicine, has unique advantages in preventive health care and in treating diseases as it already has formed an independent understanding of the aging system. TCM practitioners believe that the mechanism of aging is mainly deficiency, and pathological states such as blood stasis, qi stagnation and phlegm coagulation can exacerbate the process of aging, which involves a series of organs, including the brain, kidney, heart, liver and spleen. Our current understanding of aging has led us to realise that TCM can indeed make some beneficial changes, such as the improvement of cognitive impairment. However, due to the multi-component and multi-target nature of TCM, the exploration of its mechanism of action has become extremely complex. While analysing the relationship between gut microbiota and aging, this review explores the similarities and differences in treatment methods and mechanisms between TCM and Modern Medicine, in order to explore a new approach that combines TCM and Modern Medicine to regulate gut microbiota, improve immunity and delay aging.

Gut Microbiome-Brain Alliance: A Landscape View into Mental and Gastrointestinal Health and Disorders

Gut microbiota includes a vast collection of microorganisms residing within the gastrointestinal tract. It is broadly recognized that the gut and brain are in constant bidirectional communication, of which gut microbiota and its metabolic production are a major component, and form the so-called gut microbiome-brain axis. Disturbances of microbiota homeostasis caused by imbalance in their functional composition and metabolic activities, known as dysbiosis, cause dysregulation of these pathways and trigger changes in the blood-brain barrier permeability, thereby causing pathological malfunctions, including neurological and functional gastrointestinal disorders. In turn, the brain can affect the structure and function of gut microbiota through the autonomic nervous system by regulating gut motility, intestinal transit and secretion, and gut permeability. Here, we examine data from the CAS Content Collection, the largest collection of published scientific information, and analyze the publication landscape of recent research. We review the advances in knowledge related to the human gut microbiome, its complexity and functionality, its communication with the central nervous system, and the effect of the gut microbiome-brain axis on mental and gut health. We discuss correlations between gut microbiota composition and various diseases, specifically gastrointestinal and mental disorders. We also explore gut microbiota metabolites with regard to their impact on the brain and gut function and associated diseases. Finally, we assess clinical applications of gut-microbiota-related substances and metabolites with their development pipelines. We hope this review can serve as a useful resource in understanding the current knowledge on this emerging field in an effort to further solving of the remaining challenges and fulfilling its potential.

Probiotics as functional foods: How probiotics can alleviate the symptoms of neurological disabilities

Neurological disorders are diseases of the central nervous system with progressive loss of nervous tissue. One of the most difficult problems associated with neurological disorders is that there is no clear treatment for these diseases. In this review, the physiopathology of some neurodegenerative diseases, etiological causes, drugs used and their side effects, and finally the role of probiotics in controlling the symptoms of these neurodegenerative diseases are presented. Recently, researchers have focused more on the microbiome and the gut-brain axis, which may play a critical role in maintaining brain health. Probiotics are among the most important bacteria that have positive effects on the balance of homeostasis via influencing the microbiome. Other important functions of probiotics in alleviating symptoms of neurological disorders include anti-inflammatory properties, short-chain fatty acid production, and the production of various neurotransmitters. The effects of probiotics on the control of abnormalities seen in neurological disorders led to probiotics being referred to as "psychobiotic. Given the important role of the gut-brain axis and the imbalance of the gut microbiome in the etiology and symptoms of neurological disorders, probiotics could be considered safe agents that positively affect the balance of the microbiome as complementary treatment options for neurological disorders.

Gut microbes and host behavior: The forgotten members of the gut-microbiome

The gut microbiota refers to an entire population of microorganisms that colonize the gut. This community includes viruses, prokaryotes (bacteria and archaea), and eukaryotes (fungi and parasites). Multiple studies in the last decades described the significant involvement of gut bacteria in gut-brain axis communication; however, the involvement of other members of the gut microbiota has been neglected. Recent studies found that these 'forgotten' members of the gut microbiota may also have a role in gut-brain communication, although it is still unclear whether they have a direct effect on the brain or if their effects are mediated by gut bacteria. Here, we provide concrete suggestions for future research to tease out mechanisms of the microbiota-gut-brain axis. This article is part of the Special Issue on "Microbiome & the Brain: Mechanisms & Maladies".

Probiotic supplementation improved cognitive function in cognitively impaired and healthy older adults: a systematic review of recent trials

INTRODUCTION

Recent evidence suggests that there is clear association between microbiota and cognitive functioning, which is known as microbiome-gut-brain axis. Probiotic bacteria consumption can alter human microbiota; therefore, probiotic supplementation might affect the gut microbiota dynamics and influence cognitive function.

METHODS

Three electronic databases including PubMed, ProQuest, and EBSCOHost databases were utilized. Manual hand search of article was also done. We selected randomized controlled trial articles that measure cognitive function (as the primary outcome) after intervention with probiotic supplementation on older adult population with AD, MCI, or healthy condition. The following terms and its variant were used: "probiotic," "cognitive function," "mild cognitive impairment," "dementia," and "Alzheimer's disease."

RESULT

Nine of 10 included studies (AD, MCI, or healthy cognition population) showed cognitive function was improved significantly after probiotic supplementation, compared to control group. One study that included severe AD did not show significant changes.

CONCLUSION

Most studies involving AD, MCI, or healthy older adults showed cognitive improvement in subjects treated with probiotics for 12-24 weeks.

Health Benefits of Consuming Foods with Bacterial Probiotics, Postbiotics, and Their Metabolites: A Review

Over the years, probiotics have been extensively studied within the medical, pharmaceutical, and food fields, as it has been revealed that these microorganisms can provide health benefits from their consumption. Bacterial probiotics comprise species derived from lactic acid bacteria (LAB) (genus Lactobacillus, Leuconostoc, and Streptococcus), the genus Bifidobacterium, and strains of Bacillus and Escherichia coli, among others. The consumption of probiotic products is increasing due to the current situation derived from the pandemic caused by COVID-19. Foods with bacterial probiotics and postbiotics are premised on being healthier than those not incorporated with them. This review aims to present a bibliographic compilation related to the incorporation of bacterial probiotics in food and to demonstrate through in vitro and in vivo studies or clinical trials the health benefits obtained with their metabolites and the consumption of foods with bacterial probiotics/postbiotics. The health benefits that have been reported include effects on the digestive tract, metabolism, antioxidant, anti-inflammatory, anticancer, and psychobiotic properties, among others. Therefore, developing food products with bacterial probiotics and postbiotics is a great opportunity for research in food science, medicine, and nutrition, as well as in the food industry.

Probiotic Bifidobacterium longum BB68S Improves Cognitive Functions in Healthy Older Adults: A Randomized, Double-Blind, Placebo-Controlled Trial

Probiotics could improve cognitive functions in patients with neurological disorders such as Alzheimer’s disease, but the effects on cognitive function in healthy older adults without cognitive impairment need further study. The purpose of this study was to investigate the effect of Bifidobacterium longum BB68S (BB68S) on cognitive functions among healthy older adults without cognitive impairment. A randomized, double-blind, placebo-controlled trial was conducted with 60 healthy older adults without cognitive impairment who were divided into probiotic or placebo groups and required to consume either a sachet of probiotic (BB68S, 5 × 1010 CFU/sachet) or placebo once daily for 8 weeks. The Montreal Cognitive Assessment (MoCA) was used as an inclusion screening tool to screen elderly participants with healthy cognitive function in our study, and the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) was used to assess cognitive function in subjects before and after intervention as an assessment tool. BB68S significantly improved subjects’ cognitive functions (total RBANS score increased by 18.89 points after intervention, p < 0.0001), especially immediate memory, visuospatial/constructional, attention, and delayed memory domains. BB68S intervention increased the relative abundances of beneficial bacteria Lachnospira, Bifidobacterium, Dorea, and Cellulosilyticum, while decreasing those of bacteria related to cognition impairment, such as Collinsella, Parabacteroides, Tyzzerella, Bilophila, unclassified_c_Negativicutes, Epulopiscium, Porphyromonas, and Granulicatella. In conclusion, BB68S could improve cognitive functions in healthy elderly adults without cognitive impairment, along with having beneficial regulatory effects on their gut microbiota. This study supports probiotics as a strategy to promote healthy aging and advances cognitive aging research.

The gut microbiota is an emerging target for improving brain health during ageing

The gut microbiota plays crucial roles in maintaining the health and homeostasis of its host throughout lifespan, including through its ability to impact brain function and regulate behaviour during ageing. Studies have shown that there are disparate rates of biologic ageing despite equivalencies in chronologic age, including in the development of neurodegenerative diseases, which suggests that environmental factors may play an important role in determining health outcomes in ageing. Recent evidence demonstrates that the gut microbiota may be a potential novel target to ameliorate symptoms of brain ageing and promote healthy cognition. This review highlights the current knowledge around the relationships between the gut microbiota and host brain ageing, including potential contributions to age-related neurodegenerative diseases. Furthermore, we assess key areas for which gut microbiota-based strategies may present as opportunities for intervention.

Effects of probiotic supplementation on cognitive function in elderly: A systematic review and Meta-analysis

OBJECTIVES

Probiotic supplementation has been linked to changes in cognitive function via the gut-brain axis (GBA). However, the current literature lacks a comprehensive review regarding this matter in the elderly population.

METHOD

Electronic databases including Medline (PubMed), Scopus, Embase, Web of Science, and Google Scholar were comprehensively searched for identifying studies that assessed the effects of probiotics on the cognitive function of the elderly published until July 2020. Articles were critically reviewed and if met the inclusion criteria, entered the study.

RESULTS

Among a total of 1374 studies, 10 were eligible for meta-analysis. No significant alteration was found in the cognition of the elderly (SMD=-0.04; 95% CI [- 1.07,0.98]; P = 0.93). There was a nonsignificant increase in the level of brain-derived neurotrophic factor (SMD = 0.58; 95% CI [-1.40,2.56]; P = 0.56) and a nonsignificant reduction in malondialdehyde levels (SMD=-0.44; 95% CI [-1.07,0.19]; P = 0.17). Levels of total antioxidant capacity (SMD = 39.93; 95% CI [2.92,76.95]; P = 0.03) and total glutathione (SMD = 61.51; 95% CI [12.39,110.62]; P = 0.01) significantly increased. A significant reduction was also noted in total cholesterol levels (SMD=-4.23; 95% CI [-8.32, -0.14]; P = 0.04).

CONCLUSION

Our study did not support the hypothesis of the positive effect of probiotics on cognitive function in the elderly population; which might be due to the heterogeneity across the studies.

Investigation of memory-enhancing effects of Streptococcus thermophilus EG007 in mice and elucidating molecular and metagenomic characteristics using nanopore sequencing

Over the past decades, accumulating evidences have highlighted the gut microbiota as a key player in the brain functioning via microbiota–gut–brain axis, and accordingly, the beneficial role of several probiotic strains in cognitive ability also have been actively investigated. However, the majority of the research have demonstrated the effects against age-related cognitive decline or neurological disease. To this end, we aimed to investigate lactic acid bacteria strains having beneficial effects on the cognitive function of healthy young mice and elucidate underlying characteristics by carrying out nanopore sequencing-based genomics and metagenomics analysis. 8-week consumption of Streptococcus thermophilus EG007 demonstrated marked enhancements in behavior tests assessing short-term spatial and non-spatial learning and memory. It was revealed that EG007 possessed genes encoding various metabolites beneficial for a health condition in many aspects, including gamma-aminobutyric acid producing system, a neurotransmitter associated with mood and stress response. Also, by utilizing 16S–23S rRNA operon as a taxonomic marker, we identified more accurate species-level compositional changes in gut microbiota, which was increase of certain species, previously reported to have associations with mental health or down-regulation of inflammation or infection-related species. Moreover, correlation analysis revealed that the EG007-mediated altered microbiota had a significant correlation with the memory traits.

Psychobiotics: the Influence of Gut Microbiota on the Gut-Brain Axis in Neurological Disorders

Nervous system disorders are one of the common problems that affect many people around the world every year. Regarding the beneficial effects of the probiotics on the gut and the gut-brain axis, their application along with current medications has been the subject of intense interest. Psychobiotics are a probiotic strain capable to affect the gut-brain axis. The effective role of Psychobiotics in several neurological disorders is documented. Consumption of the Psychobiotics containing nutrients has positive effects on the improvement of microbiota as well as alleviation of some symptoms of central nervous system (CNS) disorders. In the present study, the effects of probiotic strains on some CNS disorders in terms of controlling the disease symptoms were reviewed. Finding suggests that Psychobiotics can efficiently alleviate the symptoms of several CNS disorders such as autism spectrum disorders, Parkinson’s disease, multiple sclerosis, insomnia, depression, diabetic neuropathy, and anorexia nervosa. It can be concluded that functional foods containing psychotropic strains can help to improve mental health.

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.

Examining the cognitive benefits of probiotic supplementation in physically active older adults: A randomized clinical trial

The prevalence of dementia is projected to increase with the growing older adult population and prevention strategies are urgently needed. Two promising interventions include physical activity (PA) and probiotic supplementation, with initial findings suggesting their combined use may confer greater cognitive benefits than either intervention alone. However, no study has yet examined the effects of probiotic supplementation on cognitive function in healthy, physically active older adults. The present study used archival data from a randomized clinical trial including 127 physically active, middle-aged to older adults (avg age 64.3 years) with self-reported PA levels meeting or exceeding recommendations to investigate the effects of probiotic supplementation (Lactobacillus rhamnosus GG; L.GG) on cognitive outcomes. Repeated measures ANOVAs showed no significant changes in cognitive performance from baseline to follow up as an effect of L.GG consumption. These results suggest that probiotic supplementation may not improve cognitive function in persons already engaged in high levels of PA. Future research should include prospective studies to determine whether long-term use of probiotic supplementation may help prevent cognitive decline. Novelty: • Initial research shows promising cognitive benefits of combined physical activity and probiotics consumption. • L.GG did not lead to acute cognitive improvements for older adults already meeting physical activity guidelines. • Prospective studies examining prevention of cognitive decline with probiotics in healthy and clinical samples are much needed.

Clinical and Preclinical Studies of Fermented Foods and Their Effects on Alzheimer’s Disease

The focus on managing Alzheimer’s disease (AD) is shifting towards prevention through lifestyle modification instead of treatments since the currently available treatment options are only capable of providing symptomatic relief marginally and result in various side effects. Numerous studies have reported that the intake of fermented foods resulted in the successful management of AD. Food fermentation is a biochemical process where the microorganisms metabolize the constituents of raw food materials, giving vastly different organoleptic properties and additional nutritional value, and improved biosafety effects in the final products. The consumption of fermented foods is associated with a wide array of nutraceutical benefits, including anti-oxidative, anti-inflammatory, neuroprotective, anti-apoptotic, anti-cancer, anti-fungal, anti-bacterial, immunomodulatory, and hypocholesterolemic properties. Due to their promising health benefits, fermented food products have a great prospect for commercialization in the food industry. This paper reviews the memory and cognitive enhancement and neuroprotective potential of fermented food products on AD, the recently commercialized fermented food products in the health and food industries, and their limitations. The literature reviewed here demonstrates a growing demand for fermented food products as alternative therapeutic options for the prevention and management of AD.

Probiotics: The Next Dietary Strategy against Brain Aging

Owing to their long history of safe use, probiotic microorganisms, typically from the genus Lactobacillus, have long been recognized, especially in traditional and fermented food industries. Although conventionally used for dairy, meat, and vegetable fermentation, the use of probiotics in health foods, supplements, and nutraceuticals has gradually increased. Over the past two decades, the importance of probiotics in improving gut health and immunity as well as alleviating metabolic diseases has been recognized. The new concept of a gut-heart-brain axis has led to the development of various innovations and strategies related to the introduction of probiotics in food and diet. Probiotics influence gut microbiota profiles, inflammation, and disorders and directly impact brain neurotransmitter pathways. As brain health often declines with age, the concept of probiotics being beneficial for the aging brain has also gained much momentum and emphasis in both research and product development. In this review, the concept of the aging brain, different in vivo aging models, and various aging-related benefits of probiotics are discussed.

The Therapeutic Role of Exercise and Probiotics in Stressful Brain Conditions

Oxidative stress has been recognized as a contributing factor in aging and in the progression of multiple neurological disorders such as Parkinson’s disease, Alzheimer’s dementia, ischemic stroke, and head and spinal cord injury. The increased production of reactive oxygen species (ROS) has been associated with mitochondrial dysfunction, altered metal homeostasis, and compromised brain antioxidant defence. All these changes have been reported to directly affect synaptic activity and neurotransmission in neurons, leading to cognitive dysfunction. In this context two non-invasive strategies could be employed in an attempt to improve the aforementioned stressful brain status. In this regard, it has been shown that exercise could increase the resistance against oxidative stress, thus providing enhanced neuroprotection. Indeed, there is evidence suggesting that regular physical exercise diminishes BBB permeability as it reinforces antioxidative capacity, reduces oxidative stress, and has anti-inflammatory effects. However, the differential effects of different types of exercise (aerobic exhausted exercise, anaerobic exercise, or the combination of both types) and the duration of physical activity will be also addressed in this review as likely determinants of therapeutic efficacy. The second proposed strategy is related to the use of probiotics, which can also reduce some biomarkers of oxidative stress and inflammatory cytokines, although their underlying mechanisms of action remain unclear. Moreover, various probiotics produce neuroactive molecules that directly or indirectly impact signalling in the brain. In this review, we will discuss how physical activity can be incorporated as a component of therapeutic strategies in oxidative stress-based neurological disorders along with the augmentation of probiotics intake.

Effect of fermented foods on some neurological diseases, microbiota, behaviors: mini review

Fermented foods are among the traditional foods consumed for centuries. In recent years, awareness of fermented foods has been increasing due to their positive health benefits. Fermented foods contain beneficial microorganisms. Fermented foods, such as kefir, kimchi, sauerkraut, and yoghurt, contain Lactic acid bacteria (LAB), such as Lactobacilli, Bifidobacteria, and their primary metabolites (lactic acid). Although studies on the effect of consumption of fermented foods on diabetes, cardiovascular, obesity, gastrointestinal diseases on chronic diseases have been conducted, more studies are needed regarding the relationship between neurological diseases and microbiota. There are still unexplored mechanisms in the relationship between the brain and intestine. In this review, we answer how the consumption of fermented foods affects the brain and behavior of Alzheimer's disease, Parkinson's disease, multiple sclerosis disease, stroke, and gut microbiota.

Association Between Consumption of Fermented Food and Food-Derived Prebiotics With Cognitive Performance, Depressive, and Anxiety Symptoms in Psychiatrically Healthy Medical Students Under Psychological Stress: A Prospective Cohort Study

Background

Gut microbiota-based therapeutic strategies, such as probiotic and prebiotic preparations, may benefit mental health. However, commonly consumed fermented and prebiotic-containing foods have not been well-tested. The aim of the present study was to determine whether consumption of fermented food and food-derived prebiotics is associated with cognitive performance, depressive, and anxiety symptoms in psychiatrically healthy medical students under psychological stress.

Methods

The study protocol with data analysis plan was prospectively registered. Food consumption was evaluated with a 7-day dietary record. Cognitive performance was modeled with academic examination performance in relation to subject knowledge. Pre-exam depressive and anxiety symptoms were assessed with the Patient Health Questionnaire-9 and Generalized Anxiety Disorder-7, respectively.

Results

In total, 372 medical students (22.7 ± 1.1 years of age, 66% female) completed the study. No relationship was observed between cognitive performance under stress and either fermented food (adjusted β 0.02, 95% CI −0.07–0.11, p = 0.63) or food-derived prebiotics consumption (adjusted β −0.00, 95% CI −0.09–0.09, p = 0.99). High intake of fermented food was associated with more severe depressive (adjusted β 0.11, 95% CI 0.01–0.20, p = 0.032) and anxiety symptoms under stress (adjusted β 0.13, 95% CI 0.04–0.22, p = 0.0065); however, no such link was observed for food-derived prebiotics (adjusted β 0.03, 95% CI −0.07–0.13, p = 0.50 and −0.01, 95% CI −0.11–0.08, p = 0.83, for depression and anxiety, respectively).

Conclusions

Under psychological stress in medical students, consumption of fermented food and food-derived prebiotics appears to be not associated with cognitive performance. High intake of fermented food, but not food-derived prebiotics, may be associated with severity of depressive and anxiety symptoms. The safety of fermented food in this regard therefore requires further clarification.

Effect of Probiotics on Psychiatric Symptoms and Central Nervous System Functions in Human Health and Disease: A Systematic Review and Meta-Analysis

Background: The gut microbiota impacts on central nervous system (CNS) function via the microbiota–gut–brain axis. Thus, therapeutics targeting the gut microbiota such as probiotics have the potential for improving mental health. This meta-analysis synthesizes the evidence regarding the impacts of probiotics on psychological well-being, psychiatric symptoms and CNS functioning. Methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were applied for executing this review using the databases PubMed, Web of Science and Cochrane Library. The data were summarized at qualitative and quantitative level. Results: Fifty-four randomized placebo-controlled studies were included, of which 30 were eligible for meta-analysis. If investigated, the probiotics mostly exerted effects on CNS function. Most probiotics did not affect mood, stress, anxiety, depression and psychiatric distress when compared to placebo at the qualitative level. At quantitative level, depression and psychiatric distress improved slightly in the probiotic condition (depression: mean difference −0.37 (95% CI: −0.55, −0.20); p ≤ 0.0001; psychiatric distress: mean difference −0.33 (95% CI: −0.53, −0.13); p = 0.001). Conclusions: To date it is unclear to which extent and in which specific areas next generation probiotics selected and developed for their ability to improve psychiatric condition and potentially other CNS functions are promising.

Novel Pharmacological Approaches to the Treatment of Depression

Major depressive disorder is one of the most prevalent mental health disorders. Monoamine-based antidepressants were the first drugs developed to treat major depressive disorder. More recently, ketamine and other analogues were introduced as fast-acting antidepressants. Unfortunately, currently available therapeutics are inadequate; lack of efficacy, adverse effects, and risks leave patients with limited treatment options. Efforts are now focused on understanding the etiology of depression and identifying novel targets for pharmacological treatment. In this review, we discuss promising novel pharmacological targets for the treatment of major depressive disorder. Targeting receptors including N-methyl-D-aspartate receptors, peroxisome proliferator-activated receptors, G-protein-coupled receptor 39, metabotropic glutamate receptors, galanin and opioid receptors has potential antidepressant effects. Compounds targeting biological processes: inflammation, the hypothalamic-pituitary-adrenal axis, the cholesterol biosynthesis pathway, and gut microbiota have also shown therapeutic potential. Additionally, natural products including plants, herbs, and fatty acids improved depressive symptoms and behaviors. In this review, a brief history of clinically available antidepressants will be provided, with a primary focus on novel pharmaceutical approaches with promising antidepressant effects in preclinical and clinical studies.

One Giant Leap from Mouse to Man: The Microbiota-Gut-Brain Axis in Mood Disorders and Translational Challenges Moving towards Human Clinical Trials

The microbiota–gut–brain axis is a bidirectional communication pathway that enables the gut microbiota to communicate with the brain through direct and indirect signaling pathways to influence brain physiology, function, and even behavior. Research has shown that probiotics can improve several aspects of health by changing the environment within the gut, and several lines of evidence now indicate a beneficial effect of probiotics on mental and brain health. Such evidence has prompted the arrival of a new term to the world of biotics research: psychobiotics, defined as any exogenous influence whose effect on mental health is bacterially mediated. Several taxonomic changes in the gut microbiota have been reported in neurodevelopmental disorders, mood disorders such as anxiety and depression, and neurodegenerative disorders such as Alzheimer’s disease. While clinical evidence supporting the role of the gut microbiota in mental and brain health, and indeed demonstrating the beneficial effects of probiotics is rapidly accumulating, most of the evidence to date has emerged from preclinical studies employing different animal models. The purpose of this review is to focus on the role of probiotics and the microbiota–gut–brain axis in relation to mood disorders and to review the current translational challenges from preclinical to clinical research.

The Effect of Pro-/Synbiotic Supplementation on Brain-Derived Neurotrophic Factor: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

There is a growing interest in supplementation with pro-/synbiotics for brain and mental health. Animal studies have reported that pro-/synbiotic administration can increase brain-derived neurotrophic factor (BDNF), a key regulator...

The Relationship between Gut Microbiome and Cognition in Older Australians

Ageing is associated with changes in biological processes, including reductions in cognitive functions and gut microbiome diversity. However, not much is known about the relationship between cognition and the microbiome with increasing age. Therefore, we examined the relationship between the gut microbiome and cognition in 69 healthy participants aged 60–75 years. The gut microbiome was analysed with the 16S rRNA sequencing method. The cognitive assessment included the Cognitive Drug Research computerised assessment battery, which produced five cognitive factors corresponding to ‘Quality of Episodic Secondary Memory’, ‘Quality of Working Memory’, ‘Continuity of Attention, ‘Speed of Memory’ and ‘Power of Concentration’. Multiple linear regression showed that the bacterial family Carnobacteriaceae explained 9% of the variance in predicting Quality of Episodic Secondary Memory. Alcaligenaceae and Clostridiaceae explained 15% of the variance in predicting Quality of Working Memory; Bacteroidaceae, Barnesiellaceae, Rikenellaceae and Gemellaceae explained 11% of the variance in Power of Concentration. The present study provides specific evidence of a relationship between specific families of bacteria and different domains of cognition.

Dairy Lactic Acid Bacteria and Their Potential Function in Dietetics: The Food-Gut-Health Axis

Fermented dairy products are the good source of different species of live lactic acid bacteria (LAB), which are beneficial microbes well characterized for their health-promoting potential. Traditionally, dietary intake of fermented dairy foods has been related to different health-promoting benefits including antimicrobial activity and modulation of the immune system, among others. In recent years, emerging evidence suggests a contribution of dairy LAB in the prophylaxis and therapy of non-communicable diseases. Live bacterial cells or their metabolites can directly impact physiological responses and/or act as signalling molecules mediating more complex communications. This review provides up-to-date knowledge on the interactions between LAB isolated from dairy products (dairy LAB) and human health by discussing the concept of the food–gut-health axis. In particular, some bioactivities and probiotic potentials of dairy LAB have been provided on their involvement in the gut–brain axis and non-communicable diseases mainly focusing on their potential in the treatment of obesity, cardiovascular diseases, diabetes mellitus, inflammatory bowel diseases, and cancer.

Microbiota shaping — the effects of probiotics, prebiotics, and fecal microbiota transplant on cognitive functions: A systematic review

BACKGROUND

Dementia is a chronic progressive neurological disease affecting millions of people worldwide, and represents a relevant economic burden for healthcare systems. Although its pathogenesis is still unknown, recent findings have reported that a dysregulated gut-brain axis communication, a fundamental relationship mediated by several host and microbial molecules, is associated with cognitive disorders. In addition, gut microbiota manipulation reduces neuroinflammation, improving cognitive function by restoring the functional gut-brain axis.

AIM

To better define the effects of probiotics, prebiotics, synbiotics, and fecal microbiota transplant (FMT) on cognitive function.

METHODS

We performed a literature search of human randomized clinical trials to examine the effects of the administration of probiotics, prebiotics, synbiotics, or FMT on cognition outcomes in healthy or sick people of every age, sex, and nationality. We systematically searched Embase, Medline/PubMed, Cochrane Library, central and clinicaltrials.gov databases with a combination of comprehensive terms related to cognition and gut microbiota manipulation. Then we carefully reviewed and synthesized the data by type of study design and setting, characteristics of the studied population, kind of intervention (strain type or mixture type, dosage, and frequency of administration), control treatment, inclusion and exclusion criteria, follow-up duration, and cognitive or memory outcomes.

RESULTS

After examining the titles and abstracts, the initial literature screening identified 995 articles, but we added 23 papers in our systematic review. The analyses of these selected studies highlighted that both probiotic supplementation and FMT improved cognitive function regardless of the type and posology of administration and the adopted cognitive tests and questionnaires. We found that most of the studies conducted in healthy people showed a significant positive effect of the intervention on at least one of the performed cognitive tests. Regarding unhealthy subjects, while FMT and especially probiotic administration had multiple beneficial effects on different cognitive functions, supplementation with prebiotics did not provide any cognitive improvement.

CONCLUSION

Probiotic supplementation and FMT may represent a promising strategy to restore gut eubiosis and enhance the cognitive functions of healthy people and patients with neurological disorders.

The effect of interventions targeting gut microbiota on depressive symptoms: a systematic review and meta-analysis

BACKGROUND

Despite their popularity, the efficacy of interventions targeting gut microbiota to improve depressive symptoms is unknown. Our objective is to summarize the effect of microbiome-targeting interventions on depressive symptoms.

METHODS

We conducted a systematic review and meta-analysis. We searched MEDLINE, Embase, PsycINFO, Database of Abstracts of Reviews of Effects, Cochrane Database of Systematic Reviews and the Cochrane Controlled Register of Trials from inception to Mar. 5, 2021. We included studies that evaluated probiotic, prebiotic, synbiotic, paraprobiotic or fecal microbiota transplant interventions in an adult population (age ≥ 18 yr) with an inactive or placebo comparator (defined by the absence of active intervention). Studies must have measured depressive symptoms with a validated scale, and used a randomized controlled trial study design. We conducted a random effects meta-analysis of change scores, using standardized mean difference as the measure of effect.

RESULTS

Sixty-two studies formed the final data set, with 50 included in the meta-analysis. Probiotic, prebiotic, and synbiotic interventions on depressive symptoms showed statistically significant benefits. In the single studies evaluating each of fecal microbiota transplant and paraprobiotic interventions, neither showed a statistically significant benefit.

INTERPRETATION

Despite promising findings of benefit of probiotic, prebiotic and synbiotic interventions for depressive symptoms in study populations, there is not yet strong enough evidence to favour inclusion of these interventions in treatment guidelines for depression. Critical questions about species administered, dosage and timing relative to other antidepressant medications remain to be answered.

STUDY REGISTRATION

PROSPERO no. 143178.

Vitamin K in COVID-19—Potential Anti-COVID-19 Properties of Fermented Milk Fortified with Bee Honey as a Natural Source of Vitamin K and Probiotics

Vitamin K deficiency is evident in severe and fatal COVID-19 patients. It is associated with the cytokine storm, thrombotic complications, multiple organ damage, and high mortality, suggesting a key role of vitamin K in the pathology of COVID-19. To support this view, we summarized findings reported from machine learning studies, molecular simulation, and human studies on the association between vitamin K and SARS-CoV-2. We also investigated the literature for the association between vitamin K antagonists (VKA) and the prognosis of COVID-19. In addition, we speculated that fermented milk fortified with bee honey as a natural source of vitamin K and probiotics may protect against COVID-19 and its severity. The results reported by several studies emphasize vitamin K deficiency in COVID-19 and related complications. However, the literature on the role of VKA and other oral anticoagulants in COVID-19 is controversial: some studies report reductions in (intensive care unit admission, mechanical ventilation, and mortality), others report no effect on mortality, while some studies report higher mortality among patients on chronic oral anticoagulants, including VKA. Supplementing fermented milk with honey increases milk peptides, bacterial vitamin K production, and compounds that act as potent antioxidants: phenols, sulforaphane, and metabolites of lactobacilli. Lactobacilli are probiotic bacteria that are suggested to interfere with various aspects of COVID-19 infection ranging from receptor binding to metabolic pathways involved in disease prognosis. Thus, fermented milk that contains natural honey may be a dietary manipulation capable of correcting nutritional and immune deficiencies that predispose to and aggravate COVID-19. Empirical studies are warranted to investigate the benefits of these compounds.

Probiotics: Potential novel therapeutics for microbiota-gut-brain axis dysfunction across gender and lifespan

Probiotics are live microorganisms, which when administered in adequate amounts, present a health benefit for the host. While the beneficial effects of probiotics on gastrointestinal function are generally well recognized, new animal research and clinical studies have found that alterations in gut microbial communities can have a broad range of effects throughout the body. Non-intestinal sites impacted include the immune, endocrine, cardiovascular and the central nervous system (CNS). In particular, there has been a growing interest and appreciation about the role that gut microbiota may play in affecting CNS-related function through the 'microbiota-gut-brain axis'. Emerging evidence suggests potential therapeutic benefits of probiotics in several CNS conditions, such as anxiety, depression, autism spectrum disorders and Parkinson's disease. There may also be some gender-specific variances in terms of probiotic mediated effects, with the gut microbiota shaping and being concurrently molded by the hormonal environment governing differences between the sexes. Probiotics may influence the ability of the gut microbiome to affect a variety of biological processes in the host, including neurotransmitter activity, vagal neurotransmission, generation of neuroactive metabolites and inflammatory response mediators. Some of these may engage in cross talk with host sex hormones, such as estrogens, which could be of relevance in relation to their effects on stress response and cognitive health. This raises the possibility of gender-specific variation with regards to the biological action of probiotics, including that on the endocrine and central nervous systems. In this review we aim to describe the current understanding in relation to the role and use of probiotics in microbiota-gut-brain axis-related dysfunction. Furthermore, we will address the conceptualization and classification of probiotics in the context of gender and lifespan as well as how restoring gut microbiota composition by clinical or dietary intervention can help in supporting health outcomes other than those related to the gastrointestinal tract. We also evaluate how these new learnings may impact industrial effort in probiotic research and the discovery and development of novel and more personalized, condition-specific, beneficial probiotic therapeutic agents.

Efficacy and Safety of Sesame Oil Cake Extract on Memory Function Improvement: A 12-Week, Randomized, Double-Blind, Placebo-Controlled Pilot Study

The goal of treatment for mild cognitive impairment (MCI) is to reduce the existing clinical symptoms, delay the progression of cognitive impairment and prevent the progression to Alzheimer’s disease (AD). At present, there is no effective drug therapy for AD treatment. However, early intake of dietary supplements may be effective in alleviating and delaying the MCI. This study aims to evaluate the effects of sesame oil cake extract (SOCE) supplementation on cognitive function in aged 60 years or older adults with memory impairment. A total of 70 subjects received either SOCE (n = 35) or placebo (n = 35) for 12 weeks based on random 1:1 assignment to these two groups. Cognitive function was evaluated by a computerized neurocognitive function test (CNT), and changes in the concentrations of plasma amyloid β (Aβ) proteins and urine 8-OHdG (8-hydroxy-2′-deoxyguanosine) were investigated before and after the experiment. Verbal learning test index items of the CNT improved markedly in the SOCE group compared to the placebo group (p < 0.05). Furthermore, plasma amyloid-β (1–40) and amyloid-β (1–42) levels in the SOCE group decreased significantly compared to that in the placebo group (p < 0.05). There was no statistically significant difference in urine 8-OHdG between the two groups (p > 0.05). Collectively, intake of SOCE for 12 weeks appears to have a beneficial effect on the verbal memory abilities and plasma β-amyloid levels of older adults with memory impairment.

Gut Microbiota, Probiotic Interventions, and Cognitive Function in the Elderly: A Review of Current Knowledge

Changes in the composition and proportions of the gut microbiota may be associated with numerous diseases, including cognitive impairment. Over the recent years, the growing interest in this relation is observed, but there are still many unknowns, especially in the elderly. To the best of our knowledge, this is the first work that synthesizes and critically evaluates existing evidence on the possible association between human gut microbiota and cognitive function in the elderly. For this purpose, comprehensive literature searches were conducted using the electronic databases PubMed, Google Scholar, and ScienceDirect. The gut microbiota of cognitively healthy and impaired elderly people may differ in the diversity and abundance of individual taxes, but specific taxes cannot be identified. However, some tendencies to changing the Firmicutes/Bacteroidetes ratio can be identified. Currently, clinical trials involving probiotics, prebiotics, and synbiotics supplementation have shown that there are premises for the claim that these factors can improve cognitive functions, however there is no single intervention beneficial to the elderly population. More reliable evidence from large-scale, long-period RCT is needed. Despite proposing several potential mechanisms of the gut microbiota's influence on the cognitive function impairment, prospective research on this topic is extremely difficult to conduct due to numerous confounding factors that may affect the gut microbiota. Heterogeneity of research outcomes impairs insight into these relations.