The Role of Probiotics and Their Metabolites in the Treatment of Depression

Hyperforin-induced gut microbiota metabolite carbocysteine protects against depressive-like behaviors in mice by modulating the colonic mucus barrier

OBJECTIVE

Depression affects millions, and current treatments have limitations, necessitating new approaches. Earlier research confirms Hyperforin's ability to reduce anhedonic behaviors in mice and modulate gut microbiota. This study aims to identify specific metabolic changes induced by Hyperforin that could illuminate its impact on gut microbiome metabolism, possibly uncovering novel metabolites for developing antidepressant therapies.

METHODS

Following the chronic stress model, untargeted metabolomic analysis of fecal samples was conducted to identify metabolic changes induced by Hyperforin. Bioinformatics tools analyzed the origins of differentially expressed metabolites and their correlation with Akkermansia muciniphila and Muribaculum intestinale. The significant metabolite Carbocysteine was further investigated for its antidepressant effects using behavioral assays in a mouse model of depression. Additionally, the response of the colonic mucus barrier was evaluated using Periodic Acid-Schiff (PAS) staining, scanning electron microscopy (SEM), and enzyme-linked immunosorbent assays (ELISA).

RESULTS

Hyperforin significantly altered fecal metabolite profiles in stressed mice, with a notable shift in 239 metabolites mainly associated with co-metabolism pathways and microbiota-specific processes. Among these, Carbocysteine emerged as a key metabolite linked to beneficial bacteria Akkermansia muciniphila and Muribaculum intestinale, with its levels significantly elevated following Hyperforin treatment. Behavioral assessments indicated that Carbocysteine supplementation ameliorated depressive-like behaviors in the chronic restraint stress mouse model. It also enhanced colonic mucus production and integrity.

CONCLUSION

Our research highlights Hyperforin's role in modulating gut microbiota metabolism and identifies Carbocysteine as a potential antidepressant. These findings advance our understanding of the gut-brain axis (GBA) in depression and pave the way for developing new therapeutics.

Valeriana jatamansi jones improves depressive behavior in CUMS mice by modulating vitamin B12-related ileal homeostasis

ETHNOPHARMACOLOGICAL RELEVANCE

Valeriana jatamansi Jones (V. jatamansi) is a traditional Chinese medicine (TCM). It was recorded in Diannan Bencao, Compendium of Materia Medica and some local medical books and was described as useful in treating insomnia, distraction, poor mental health, vomiting and diarrhea.

AIM OF THE STUDY

To investigate whether the antidepressant effect of V. jatamansi may operate through modulating vitamin B12-related ileal homeostasis using a chronic unpredictable mild stress (CUMS) mouse model.

MATERIALS AND METHODS

A CUMS-induced depression model was established in mice for five weeks, after which V. jatamansi extracts were administered for three weeks. At week eight, the forced swimming test and novelty-suppressed feeding test were conducted. H&E staining assessed ileal pathology, while 16S rDNA sequencing analyzed changes in ileal microbiota. Additionally, B12 in serum, cubilin (CUBN) and amnionless (AMN) in ileal tissue, methionine synthase (MS) and homocysteine (Hcy) in the hippocampus were measured using ELISA, and the correlations between them and ileal microbiota were explored.

RESULTS

Mice in the model group exhibited significant depressive behavior. However, after treatment with V. jatamansi, immobility time and feeding latency were improved. H&E staining demonstrated the repairing effect of V. jatamansi on the ileum regarding tissue damage. The alpha and beta diversity of the ileal microbiota were regulated and converged to the normal group. Additionally, V. jatamansi modulated B12, CUBN, AMN, MS, and Hcy levels. Correlation analysis showed that there are certain correlations between a variety of microorganisms and B12-related factors.

CONCLUSION

These findings suggest that the mechanism of V. jatamansi in treating depression may be through repairing depression-associated intestinal damage. This repair process may affect the intestinal absorption and microbial production of B12. By reversing the reduction of serum B12, V. jatamansi ultimately reduces the infiltration of Hcy into the CNS.

Distinct prefrontal cortex alterations in confirmed and suspected depression individuals with different perceived stress during an emotional autobiographical memory task: One fNIRS investigation

BACKGROUND

Previous research showed that perceived stress was strongly linked to depression, little is known about the underlying neurological mechanism of different depression subtypes with different perceived stress, and there is currently no classification of stress-based subtypes of depression. This study aimed at using fNIRS to uncover the neuromechanism of confirmed and suspected depression with different perceived stress, hence providing neurobiological evidence for the classification of stress-based depression subtypes. It is a significant target for effective depression treatment.

METHOD

The study included 551 young adults: 256 healthy control individuals, 62 confirmed depression patients, and 233 suspected depression participants. A 53-channel fNIRS imaging system was used to gather the average oxyhemoglobin level in the PFC during EAMT.

RESULTS

Compared with HC, confirmed and suspected depression group show significant lower hemodynamic activation in right frontal lobe of frame under high loss of control. Confirmed depression with high sense of tension had higher activation than with high loss of control in right dlPFC, while for suspected depression, the activation with high sense of tension was lower than with high loss of control in left broca's area (BA) and front polar cortex (FPC).

CONCLUSION

All perceived stresses were not equal in their impacts on different depression types. The confirmed and suspected depression were two different depression subtypes sharing distinct activation pattern under different perceived stress in PFC, which may be an important target for stress-linked psychopathology. Depression can be further classified precisely based on stress. fNIRS can provide neuroimaging evidence for classification of stress-based depression subtypes.

Glucose metabolism impairment in major depressive disorder

Major depressive disorder (MDD) is a common mental disorder with chronic tendencies that seriously affect regular work, life, and study. However, its exact pathogenesis remains unclear. Patients with MDD experience systemic and localized impairments in glucose metabolism throughout the disease course, disrupting various processes such as glucose uptake, glycoprotein transport, glycolysis, the tricarboxylic acid cycle (TCA), and oxidative phosphorylation (OXPHOS). These impairments may result from mechanisms including insulin resistance, hyperglycemia-induced damage, oxidative stress, astrocyte abnormalities, and mitochondrial dysfunction, leading to insufficient energy supply, altered synaptic plasticity, neuronal cell death, and functional and structural damage to reward networks. These mechanical changes contribute to the pathogenesis of MDD and severely interfere with the prognosis. Herein, we summarized the impairment of glucose metabolism and its pathophysiological mechanisms in patients with MDD. In addition, we briefly discussed potential pharmacological interventions for glucose metabolism to alleviate MDD, including glucagon-like peptide-1 receptor agonists, metformin, topical insulin, liraglutide, and pioglitazone, to encourage the development of new therapeutics.

Role of Probiotics in Depression: Connecting Dots of Gut-Brain-Axis Through Hypothalamic-Pituitary Adrenal Axis and Tryptophan/Kynurenic Pathway involving Indoleamine-2,3-dioxygenase

Depression is one of the most disabling mental disorders worldwide and characterized by symptoms including worthlessness, anhedonia, sleep, and appetite disturbances. Recently, studies have suggested that tryptophan (Trp) metabolism plays a key role in depressed mood through serotonin and kynurenine pathway involving enzyme tryptophan 5-monooxygenase (TPH) and indoleamine-2,3-dioxygenase (IDO) respectively. Moreover, during neuroinflammation, IDO is activated by proinflammatory cytokines and affects neurogenesis, cognition, disturbed hypothalamic-pituitary-adrenal (HPA) axis, and gut homeostasis by altering the gut bacteria and its metabolites like Trp derivatives. Furthermore, over the decades, researchers have focused on understanding communication between the human microbiome, especially gut microbiota, and mental health, called gut-brain-axis (GBA), particularly through Trp metabolism. Supplementation of probiotics in depression has gained attention from researchers and clinicians. However, there is limited information about probiotics supplementation on depression involving enzyme IDO and kynurenine pathway metabolites. This review discussed the potential role of probiotics in depression through the tryptophan/kynurenine pathway.

[Effects of Vitamin B12 on Behaviors, Brain Monoamine Neurotransmitters, and Brain-Derived Neurotrophic Factor in Depressive Rats]

Objective

To investigate the behavioral changes and monoamine neurotransmitter levels in a rat model of chronic unpredictable mild stress (CUMS)-induced depression and explore the potential effects of Vitamin B12 (VitB12) on CUMS model rats and the underlying mechanisms.

Methods

A total of 72 Sprague-Dawley (SD) rats were randomly assigned to 3 groups, a control group, a CUMS group (subjected to three weeks of CUMS), and a CUMS + VitB12 group (CUMS rats receiving microinjections of VitB12 in the neck). The body mass of the rats was measured, and behavioral assessments were conducted using the sucrose preference test, open field test, and forced swimming test. High-performance liquid chromatography (HPLC) was used to analyze the levels of monoamine neurotransmitters, including 5-hydroxytryptamine (5-HT), norepinephrine (NE), and dopamine (DA), in each group of rats. Hematoxylin-eosin (HE) staining was performed to observe pathological changes in hippocampal neurons. Western blot was performed to detect the expression of signal pathway-related proteins, including brain-derived neurotrophic factor (BDNF), tropomyosin receptor kinase B (TrkB), and cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB) in the hippocampal tissue.

Results

Starting from week 5, rats in the CUMS group exhibited lower average body mass compared to the control group, while the CUMS + VitB12 group showed a significant increase in body mass compared to the CUMS group (P < 0.05). At weeks 3 and 6, sucrose preference of rats in the CUMS group was significantly lower than that in the control group (P < 0.001). At week 3, sucrose consumption in the CUMS + VitB12 group was significantly higher than that in the CUMS group (P < 0.01), with a more pronounced increase observed in week 6 (P < 0.001). Starting from week 4, the CUMS group showed reduced scores in grid crossing, grooming, and rearing activities in the open field test compared to the control group, indicating reduced locomotor activity and exploratory behavior (P < 0.001). The CUMS + VitB12 group showed improved behavioral performance compared to the CUMS group (P < 0.01, P < 0.001). In the forced swimming test at weeks 3 and 6, the immobility time of rats in the CUMS group was significantly longer than that in the control group (P < 0.01). At week 6, the immobility time of rats in the CUMS + VitB12 group was significantly shorter compared to that of the CUMS group (P < 0.01). HPLC results showed that the levels of 5-HT, NE, and DA in the cerebral cortex of rats in the CUMS group were significantly lower than those in the control group (P < 0.01, P < 0.001), while these neurotransmitter levels were significantly higher in the CUMS + VitB12 group compared to those in the CUMS group (P < 0.05, P < 0.01). HE staining results showed that the number of hippocampal cells in the CUMS group was significantly reduced, with shrunken nuclei, while the CUMS + VitB12 group showed an increased number of neurons with intact morphology compared to the CUMS group (P < 0.05). Western blot analysis showed that the expression levels of BDNF, TrkB, and CREB proteins in the hippocampus were significantly lower in rats in the CUMS group than those in the control group (P < 0.05), while the expression levels of BDNF, TrkB, and phosphorylated CREB (p-CREB) were significantly higher in the CUMS + VitB12 group compared to the CUMS group (P < 0.05).

Conclusion

In CUMS rats, the levels of monoamine neurotransmitters (5-HT, NE, and DA) in the cerebral cortex of the brain are decreased, accompanied by a decrease in neuronal cells, which results in anxiety- and depression-like behaviors. VitB12 can upregulate the levels of these neurotransmitters, ameliorate the cytopathological conditions, and regulate the BDNF/TrkB/p-CREB signaling pathway, thereby alleviating depressive symptoms.

Association of probiotics, prebiotics, synbiotics or yogurt supplement with prevalence and all-cause mortality of depression: NHANES 2005-2016

BACKGROUND

A growing body of studies revealed that enteric dysbacteriosis could result in depression via the "gut-microbiota-brain axis" (GMBA). Whether probiotics, prebiotics, and synbiotics supplements could lessen the risk of depression is a topic attracting attention. This research was conducted to evaluate the relationship between probiotics, prebiotics, synbiotics, or yogurt supplements and depression with large cross-sectional data.

METHODS

All data in our research was sourced from the National Health and Nutrition Examination Survey (NHANES) (2005-2016). Probiotics, prebiotics, synbiotics, and yogurt supplements were identified using Food Frequency Questionnaire (FFQ) and Dietary Supplement Use 30-Day (DSQ). We employed the Patient Health Questionnaire (PHQ-9) for evaluating depression. Logistic regression and the Kaplan-Meier curve were performed to examine the correlation between the supplements and depression, as well as mortality.

RESULTS

A total of 17,745 adult participants were selected. The participants who supplemented probiotics, prebiotics, synbiotics, or yogurt products in the last 30 days showed a significantly lower depression rate compared with those who didn't. Specifically, the supplements could alleviate depressive symptoms including sad, anhedonia, sleep problems, fatigue, appetite changes, and psychomotor changes. This association was more prominent in specific populations such as the population aged 40-60 years, male, whites. The supplements also show more significant effects on increasing survival rates in patients with mild depression.

LIMITATION

Cross-sectional analysis reveals correlative but not causative association.

CONCLUSION

Based on the analysis of NHANES data, our research highlights the positive effect the supplements have on preventing depression, relieving depressive symptoms and increasing survival rates. This effect varied across populations.

Beyond metabolic messengers: Bile acids and TGR5 as pharmacotherapeutic intervention for psychiatric disorders

Psychiatric disorders pose a significant global health challenge, exacerbated by the COVID-19 pandemic and insufficiently addressed by the current treatments. This review explores the emerging role of bile acids and the TGR5 receptor in the pathophysiology of psychiatric conditions, emphasizing their signaling within the gut-brain axis. We detail the synthesis and systemic functions of bile acids, their transformation by gut microbiota, and their impact across various neuropsychiatric disorders, including major depressive disorder, general anxiety disorder, schizophrenia, autism spectrum disorder, and bipolar disorder. The review highlights how dysbiosis and altered bile acid metabolism contribute to the development and exacerbation of these neuropsychiatric disorders through mechanisms involving inflammation, oxidative stress, and neurotransmitter dysregulation. Importantly, we detail both pharmacological and non-pharmacological interventions that modulate TGR5 signaling, offering potential breakthroughs in treatment strategies. These include dietary adjustments to enhance beneficial bile acids production and the use of specific TGR5 agonists that have shown promise in preclinical and clinical settings for their regulatory effects on critical pathways such as cAMP-PKA, NRF2-mediated antioxidant responses, and neuroinflammation. By integrating findings from the dynamics of gut microbiota, bile acids metabolism, and TGR5 receptor related signaling events, this review underscores cutting-edge therapeutic approaches poised to revolutionize the management and treatment of psychiatric disorders.

The Role of Probiotics in Skin Care: Advances, Challenges, and Future Needs

The skin, being the largest organ in the human body, plays a pivotal role in safeguarding the body against invasive pathogens. Therefore, it is essential to reinforce and protect this vital organ. Current research supports the impact of probiotics on skin health and their ability to alleviate various skin disorders. However, the effectiveness and probable side effects of probiotics in skin care remain a subject of debate, necessitating further investigation and analysis. Hence, this study aims to highlight existing gaps and future needs in the current research on probiotics in skin care and pave the way for future investigations. Therefore, we scrutinized the effects of oral (fermented foods and dietary supplements) and non-oral/topical probiotics on skin care, and the mechanism of probiotics that affect skin health. The results of most studies showed that fermented foods containing probiotics, particularly dairy products, positively impact skin health. The research results regarding the efficacy of probiotic supplements and live strains in treating skin disorders show promising potential. However, safety evaluations are crucial, to identify any potential adverse effects. While research has identified numerous potential mechanisms by which probiotics may influence skin health, a complete understanding of their precise mode of action remains elusive. However, it seems that probiotics can exert their positive effects through the gut-skin and gut-skin-brain axis on the human body. Therefore, following the identification of safe probiotics, additional studies should be carried out to establish optimal dosages, potential side effects, suitable regulatory guidelines, and validation methods.

Extraction, purification, structural characterization, and bioactivities of Ginkgo biloba leave polysaccharides: A review

Ginkgo biloba, a deciduous tree from the Ginkgoaceae family, is widely cultivated globally. In China, it predominantly grows in the eastern and southern regions. The leaves can be harvested multiple times throughout the growing season, presenting a significant resource potential. Ginkgo biloba leaves are considered as a living fossil with both medicinal and edible properties in traditional Chinese medicine. Polysaccharides, the primary bioactive compounds in these leaves, exhibit numerous biological activities, including antioxidant, antitumor, anti-inflammatory, immunoregulatory activity, antidepressant effects, hepatoprotective, hypoglycemic activity and hair-growth promoting effect. This review highlights the advancements in the extraction separation purification, structural elucidation, and functional analysis of polysaccharides derived from Ginkgo biloba leaves over the past decade, aiming to provide valuable insights for future development and commercialization of Ginkgo biloba leave polysaccharides.

Novel odd-chain cyclopropane fatty acids: detection in a mammalian lipidome and uptake by hepatosplanchnic tissues

Microbe-produced molecules (xenometabolites) found in foods or produced by gut microbiota are increasingly implicated in microbe-microbe and microbe-host communication. Xenolipids, in particular, are a class of metabolites for which the full catalog remains to be elaborated in mammalian systems. We and others have observed that cis-3,4-methylene-heptanoylcarnitine is a lipid derivative that is one of the most abundant medium-chain acylcarnitines in human blood, hypothesized to be a product of incomplete β-oxidation of one or more "odd-chain" long-chain cyclopropane fatty acids (CpFAs). We deduced two possible candidates, cis-11,12-methylene-pentadecanoic acid (cis-11,12-MPD) and cis-13,14-methylene-heptadecanoic acid (cis-13,14-MHD). Authentic standards were synthesized: cis-11-pentadecenoic acid and cis-13-heptadecenoic acid were generated (using Jones reagent) from cis-11-pentadecene-1-ol and cis-13-heptadecene-1-ol, respectively, and these were converted to CpFAs via a reaction involving diiodomethane. Using these standards in mass spectrometry analyses, we determined the presence/absence of cis-11,12-MPD and cis-13,14-MHD in archived piglet biospecimens. Both CpFAs were detected in rectal contents of sow and soy-fed piglets. Archived mass spectra were analyzed post hoc from a second independent study that used tissue-specific catheterization to monitor net metabolite flux in growing pigs. This confirmed the presence of both CpFAs in plasma and revealed a significant net uptake of the odd-chain CpFAs across the splanchnic tissue bed and liver. The results confirm that the novel xenolipids cis-11,12-MPD and cis-13,14-MHD can be components of the mammalian lipidome and are viable candidate precursors of cis-3,4-methylene-heptanoylcarnitine produced from partial β-oxidation in liver or other tissues.

Strain-specific effects of probiotics on depression and anxiety: a meta-analysis

INTRODUCTION

Depression and anxiety are pervasive mental health disorders with substantial global burdens. Probiotics, live microorganisms known for their health benefits, have emerged as a potential therapeutic intervention for these conditions. This systematic review and meta-analysis aim to evaluate the strain-specific effects of probiotics on relieving depressive and anxiety symptoms while elucidating underlying mechanisms.

METHODS

EMBASE, Cochrane CENTRAL and PubMed/Medline were systematically queried to identify studies released until May 15, 2024. Randomized Controlled Trials (RCTs) that employed standardized assessment tools for depression and anxiety namely Beck Depression Inventory (BDI), Hamilton Depression Rating Scale (HAMD), Depression Anxiety Stress Scales (DASS), or Montgomery-Asberg Depression Rating Scale (MADRS) were included.

RESULTS

12 RCTs involving 707 participants were included. Seven RCTs utilizing the BDI questionnaire demonstrated a significant decrease in depressive symptoms favoring probiotics containing strains such as Lactobacillus acidophilus, Lactobacillus paracasei, Lactobacillus casei, Lactobacillus plantarum, Lactobacillus salivarius, Bifidobacterium bifidum, Bifidobacterium lactis, Bifidobacterium breve, and Bifidobacterium longum (MD: -2.69, CI95%: -4.22/-1.16, p value: 0.00). Conversely, RCTs using HAMD showed a non-significant reduction in depressive symptoms (MD: -1.40, CI95%: -3.29/0.48, p value: 0.14). RCTs employing DASS and MADRS scales also showed no significant differences.

CONCLUSION

This meta-analysis offers valuable insights into the strain-specific effects of probiotics containing Lactobacillus and Bifidobacterium species on depressive and anxiety symptoms. While our findings suggest a significant reduction in depressive symptoms based on the BDI scale favoring probiotics, the lack of significant effects observed on the HAMD, DASS, and MADRS scales underscores the complexity inherent in these conditions. It is imperative to acknowledge the mixed results across different measurement scales, indicating the need for cautious interpretation. Therefore, we advocate for a nuanced understanding of probiotics' impacts on various dimensions of mood, emphasizing the necessity for further research.

Gut-Brain Axis: Role of Microbiome, Metabolomics, Hormones, and Stress in Mental Health Disorders

The influence of gut microbiome, metabolites, omics, hormones, and stress on general and mental health is increasingly being recognized. Ancient cultures recognized the importance of diet and gut health on the overall health of an individual. Western science and modern scientific methods are beginning to unravel the foundations and mechanisms behind some of the ancient beliefs and customs. The gut microbiome, an organ itself, is now thought to influence almost all other organs, ranging from the brain to the reproductive systems. Gut microbiome, metabolites, hormones, and biological sex also influence a myriad of health conditions that range from mental health disorders, obesity, gastrointestinal disorders, and cardiovascular diseases to reproductive health. Here, we review the history and current understanding of the gut-brain axis bidirectional talk in various mental health disorders with special emphasis on anxiety and depressive disorders, whose prevalence has increased by over 50% in the past three decades with COVID-19 pandemic being the biggest risk factor in the last few years. The vagal nerve is an important contributor to this bidirectional talk, but other pathways also contribute, and most remain understudied. Probiotics containing Lactobacillus and Bifidobacterium species seem to have the most impact on improvement in mental health symptoms, but the challenge appears to be maintaining sustained levels, especially since neither Lactobacillus nor Bifidobacterium can permanently colonize the gut. Ancient endogenous retroviral DNA in the human genome is also linked to several psychiatric disorders, including depression. These discoveries reveal the complex and intricately intertwined nature of gut health with mental health disorders.

Probiotics and the microbiota-gut-brain axis in neurodegeneration: Beneficial effects and mechanistic insights

Neurodegenerative diseases (NDs) are a group of heterogeneous disorders with a high socioeconomic burden. Although pharmacotherapy is currently the principal therapeutic approach for the management of NDs, mounting evidence supports the notion that the protracted application of available drugs would abate their dopaminergic outcomes in the long run. The therapeutic application of microbiome-based modalities has received escalating attention in biomedical works. In-depth investigations of the bidirectional communication between the microbiome in the gut and the brain offer a multitude of targets for the treatment of NDs or maximizing the patient's quality of life. Probiotic administration is a well-known microbial-oriented approach to modulate the gut microbiota and potentially influence the process of neurodegeneration. Of note, there is a strong need for further investigation to map out the mechanistic prospects for the gut-brain axis and the clinical efficacy of probiotics. In this review, we discuss the importance of microbiome modulation and hemostasis via probiotics, prebiotics, postbiotics and synbiotics in ameliorating pathological neurodegenerative events. Also, we meticulously describe the underlying mechanism of action of probiotics and their metabolites on the gut-brain axis in different NDs. We suppose that the present work will provide a functional direction for the use of probiotic-based modalities in promoting current practical treatments for the management of neurodegenerative-related diseases.

Human Gut Microbiota for Diagnosis and Treatment of Depression

Nowadays, depressive disorder is spreading rapidly all over the world. Therefore, attention to the studies of the pathogenesis of the disease in order to find novel ways of early diagnosis and treatment is increasing among the scientific and medical communities. Special attention is drawn to a biomarker and therapeutic strategy through the microbiota-gut-brain axis. It is known that the symbiotic interactions between the gut microbes and the host can affect mental health. The review analyzes the mechanisms and ways of action of the gut microbiota on the pathophysiology of depression. The possibility of using knowledge about the taxonomic composition and metabolic profile of the microbiota of patients with depression to select gene compositions (metagenomic signature) as biomarkers of the disease is evaluated. The use of in silico technologies (machine learning) for the diagnosis of depression based on the biomarkers of the gut microbiota is given. Alternative approaches to the treatment of depression are being considered by balancing the microbial composition through dietary modifications and the use of additives, namely probiotics, postbiotics (including vesicles) and prebiotics as psychobiotics, and fecal transplantation. The bacterium Faecalibacterium prausnitzii is under consideration as a promising new-generation probiotic and auxiliary diagnostic biomarker of depression. The analysis conducted in this review may be useful for clinical practice and pharmacology.

A Narrative Review on the Advance of Probiotics to Metabiotics

Recently, the term metabiotics has emerged as a new concept of probiotics. This concept entails combining existing probiotic components with metabolic by-products improve specific physiological functionalities. Representative ingredients of these metabiotics include short-chain fatty acids (SCFAs), bacteriocins, polysaccharides, and peptides. The new concept is highly regarded as it complements the side effects of existing probiotics and is safe and easy to administer. Known health functions of metabiotics are mainly immune regulation, anti-inflammatory, anticancer, and brain-neurological health. Research has been actively conducted on the health benefits related to the composition of intestinal microorganisms. Among them, the focus has been on brain neurological health, which requires extensive research. This study showed that neurological disorders, such as depression, anxiety, autism spectrum disorder, Alzheimer's disease, and Parkinson's disease, can be treated and prevented according to the gut-brain axis theory by changing the intestinal microflora. In addition, various studies are being conducted on the immunomodulatory and anticancer effects of substances related to metabiotics of the microbiome. In particular, its efficacy is expected to be confirmed through human studies on various cancers. Therefore, developing various health functional effects of the next-generation probiotics such as metabiotics to prevent or treatment of various diseases is anticipated.

Exploring the Influence of Gut-Brain Axis Modulation on Cognitive Health: A Comprehensive Review of Prebiotics, Probiotics, and Symbiotics

Recent research exploring the relationship between the gut and the brain suggests that the condition of the gut microbiota can influence cognitive health. A well-balanced gut microbiota may help reduce inflammation, which is linked to neurodegenerative conditions. Prebiotics, probiotics, and symbiotics are nutritional supplements and functional food components associated with gastrointestinal well-being. The bidirectional communication of the gut-brain axis is essential for maintaining homeostasis, with pre-, pro-, and symbiotics potentially affecting various cognitive functions such as attention, perception, and memory. Numerous studies have consistently shown that incorporating pre-, pro-, and symbiotics into a healthy diet can lead to improvements in cognitive functions and mood. Maintaining a healthy gut microbiota can support optimal cognitive function, which is crucial for disease prevention in our fast-paced, Westernized society. Our results indicate cognitive benefits in healthy older individuals with probiotic supplementation but not in healthy older individuals who have good and adequate levels of physical activity. Additionally, it appears that there are cognitive benefits in patients with mild cognitive impairment and Alzheimer's disease, while mixed results seem to arise in younger and healthier individuals. However, it is important to acknowledge that individual responses may vary, and the use of these dietary supplements should be tailored to each individual's unique health circumstances and needs.

Gas Chromatography-Mass Spectrometry Profiling of Volatile Metabolites Produced by Some Bacillus spp. and Evaluation of Their Antibacterial and Antibiotic Activities

Bacillus species produce different classes of antimicrobial and antioxidant substances: peptides or proteins with different structural compositions and molecular masses and a broad range of volatile organic compounds (VOCs), some of which may serve as biomarkers for microorganism identification. The aim of this study is the identification of biologically active compounds synthesized by five Bacillus species using gas chromatography coupled to mass spectrometry (GC-MS). The current study profoundly enhances the knowledge of antibacterial and antioxidant metabolites ensuring the unambiguous identification of VOCs produced by some Bacillus species, which were isolated from vegetable samples of potato, carrot, and tomato. Phylogenetic and biochemical studies were used to identify the bacterial isolates after culturing. Phylogenetic analysis proved that five bacterial isolates BSS12, BSS13, BSS16, BSS21, and BSS25 showed 99% nucleotide sequence similarities with Bacillus safensis AS-08, Bacillus cereus WAB2133, Bacillus acidiproducens NiuFun, Bacillus toyonesis FORT 102, and Bacillus thuringiensis F3, respectively. The crude extract was prepared from bacterial isolates to assess the antibiotic resistance potency and the antimicrobial potential against various targeted multidrug-resistant strains, including yeast strains such as Candida albicans, Candida krusei, and bacterial strains of Enterococcus hirae, Escherichia coli, Klebsiella aerogenes, Klebsiella pneumoniae, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus group B, Streptococcus mutans, Shigella sonnei, Salmonella enteritidis, Serratia marcescens, Pseudomonas aeruginosa, and Proteus vulgaris. GC-MS analysis of bacterial strains found that VOCs from Bacillus species come in a variety of chemical forms, such as ketones, alcohols, terpenoids, alkenes, etc. Overall, 69 volatile organic compounds were identified from five Bacillus species, and all five were found to share different chemical classes of volatile organic components, which have a variety of pharmacological applications. However, eight antibacterial compounds with different concentrations were commonly found in all five species: acetoin, acetic acid, butanoic acid, 2-methyl-, oxime-, methoxy-phenyl, phenol, 1,2-benzenedicarboxylic acid, bis(2-methylpropyl) ester, nonanoic acid, and hexadecanoic acid, methyl. The present study has demonstrated that bacterial isolates BSS25, BSS21, and BSS16 display potent inhibitory effects against Candida albicans, while BSS25, BSS21, and BSS13 exhibit the ability to restrain the growth and activity of Candida krusei. Notably, BSS25 and BSS21 are the only isolates that demonstrate substantial inhibitory activity against Klebsiella aerogenes. This disparity in inhibitory effects could be attributed to the higher concentrations of acetoin in BSS25 and BSS21, whereas BSS16 and BSS13 have relatively elevated levels of butanoic acid, 2-methyl-. Certainly, the presence of acetoin and butanoic acid, 2-methyl-, contributes to the enhanced antibacterial potential of these bacterial strains, in conjunction with other organic volatile compounds and peptides, among other factors. The biology and physiology of Bacillus can be better understood using these results, which can also be used to create novel biotechnological procedures and applications. Moreover, because of its exceptional ability to synthesize and produce a variety of different antibacterial compounds, Bacillus species can serve as natural and universal carriers for antibiotic compounds in the form of probiotic cultures and strains to fight different pathogens, including mycobacteria.