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Roles of Diet-Associated Gut Microbial Metabolites on Brain Health: Cell-to-Cell Interactions between Gut Bacteria and the Central Nervous System.
Kim, CS
Advances in nutrition (Bethesda, Md.). 2024;(1):100136
Abstract
Gut microbiota have crucial effects on brain function via the gut-brain axis. Growing evidence suggests that this interaction is mediated by signaling molecules derived from dietary components metabolized by the intestinal microbiota. Although recent studies have provided a substantial understanding of the cell-specific effects of gut microbial molecules in gut microbiome-brain research, further validation is needed. This review presents recent findings on gut microbiota-derived dietary metabolites that enter the systemic circulation and influence the cell-to-cell interactions between gut microbes and cells in the central nervous system (CNS), particularly microglia, astrocytes, and neuronal cells, ultimately affecting cognitive function, mood, and behavior. Specifically, this review highlights the roles of metabolites produced by the gut microbiota via dietary component transformation, including short-chain fatty acids, tryptophan metabolites, and bile acid metabolites, in promoting the function and maturation of brain cells and suppressing inflammatory signals in the CNS. We also discuss future directions for gut microbiome-brain research, focusing on diet-induced microbial metabolite-based therapies as possible novel approaches to mental health treatment.
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Effectiveness of low-intensity atorvastatin 5 mg and ezetimibe 10 mg combination therapy compared with moderate-intensity atorvastatin 10 mg monotherapy: A randomized, double-blinded, multi-center, phase III study.
Lee, SA, Hong, SJ, Sung, JH, Kim, KS, Kim, SH, Cho, JM, Chun, SW, Lee, SR, Kim, CS, Kim, TN, et al
Medicine. 2023;(47):e36122
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Abstract
BACKGROUND We compared the efficacy and safety of low-intensity atorvastatin and ezetimibe combination therapy with moderate-intensity atorvastatin monotherapy in patients requiring cholesterol-lowering therapy. METHODS At 19 centers in Korea, 290 patients were randomized to 4 groups: atorvastatin 5 mg and ezetimibe 10 mg (A5E), ezetimibe 10 mg (E), atorvastatin 5 mg (A5), and atorvastatin 10 mg (A10). Clinical and laboratory examinations were performed at baseline, and at 4-week and 8-week follow-ups. The primary endpoint was percentage change from baseline in low-density lipoprotein (LDL) cholesterol levels at the 8-week follow-up. Secondary endpoints included percentage changes from baseline in additional lipid parameters. RESULTS Baseline characteristics were similar among the study groups. At the 8-week follow-up, percentage changes in LDL cholesterol levels were significantly greater in the A5E group (49.2%) than in the E (18.7%), A5 (27.9%), and A10 (36.4%) groups. Similar findings were observed regarding the percentage changes in total cholesterol, non-high-density lipoprotein cholesterol, and apolipoprotein B levels. Triglyceride levels were also significantly decreased in the A5E group than in the E group, whereas high-density lipoprotein levels substantially increased in the A5E group than in the E group. In patients with low- and intermediate-cardiovascular risk, 93.3% achieved the target LDL cholesterol levels in the A5E group, 40.0% in the E group, 66.7% in the A5 group, and 92.9% in the A10 group. In addition, 31.4% of patients in the A5E group, 8.1% in E, 9.7% in A5, and 7.3% in the A10 group reached the target levels of both LDL cholesterol < 70 mg/dL and reduction of LDL ≥ 50% from baseline. CONCLUSIONS The addition of ezetimibe to low-intensity atorvastatin had a greater effect on lowering LDL cholesterol than moderate-intensity atorvastatin alone, offering an effective treatment option for cholesterol management, especially in patients with low and intermediate risks.
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Efficacy and safety of enavogliflozin versus dapagliflozin added to metformin plus gemigliptin treatment in patients with type 2 diabetes: A double-blind, randomized, comparator-active study: ENHANCE-D study.
Kim, KS, Han, KA, Kim, TN, Park, CY, Park, JH, Kim, SY, Kim, YH, Song, KH, Kang, ES, Kim, CS, et al
Diabetes & metabolism. 2023;(4):101440
Abstract
AIMS: This study evaluated the efficacy and safety of enavogliflozin, a novel sodium-glucose cotransporter 2 inhibitor, versus dapagliflozin in Korean patients with type 2 diabetes mellitus (T2DM) inadequately controlled with metformin and gemigliptin. METHODS In this multicenter, double-blind, randomized study, patients with inadequate response to metformin (≥ 1000 mg/day) plus gemigliptin (50 mg/day) were randomized to receive enavogliflozin 0.3 mg/day (n = 134) or dapagliflozin 10 mg/day (n = 136) in addition to the metformin plus gemigliptin therapy. The primary endpoint was change in HbA1c from baseline to week 24. RESULTS Both treatments significantly reduced HbA1c at week 24 (-0.92% in enavogliflozin group, -0.86% in dapagliflozin group). The enavogliflozin and dapagliflozin groups did not differ in terms of changes in HbA1c (between-group difference: -0.06%, 95% confidence interval [CI]: -0.19, 0.06) and fasting plasma glucose (between-group difference: -3.49 mg/dl [-8.08;1.10]). An increase in urine glucose-creatinine ratio was significantly greater in the enavogliflozin group than in the dapagliflozin group (60.2 g/g versus 43.5 g/g, P < 0.0001). The incidence of treatment-emergent adverse events was similar between the groups (21.64% versus 23.53%). CONCLUSIONS Enavogliflozin, added to metformin plus gemigliptin, was well tolerated and as effective as dapagliflozin in the treatment of patients with T2DM.
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Probiotic supplementation has sex-dependent effects on immune responses in association with the gut microbiota in community-dwelling older adults: a randomized, double-blind, placebo-controlled, multicenter trial.
Kim, CS, Jung, MH, Choi, EY, Shin, DM
Nutrition research and practice. 2023;(5):883-898
Abstract
BACKGROUND/OBJECTIVES Probiotics have been suggested as potent modulators of age-related disorders in immunological functions, yet little is known about sex-dependent effects of probiotic supplements. Therefore, we aimed to investigate sex-dependent effects of probiotics on profiles of the gut microbiota and peripheral immune cells in healthy older adults. SUBJECTS/METHODS In a randomized, double-blind, placebo-controlled, multicenter trial, healthy elderly individuals ≥ 65 yrs old were administered probiotic capsules (or placebo) for 12 wk. Gut microbiota was analyzed using 16S rRNA gene sequencing and bioinformatic analyses. Peripheral immune cells were profiled using flow cytometry for lymphocytes (natural killer, B, CD4+ T, and CD8+ T cells), dendritic cells, monocytes, and their subpopulations. RESULTS Compared with placebo, phylum Firmicutes was significantly reduced in the probiotic group in women, but not in men. At the genus level, sex-specific responses included reductions in the relative abundances of pro-inflammatory gut microbes, including Catabacter and unclassified_Coriobacteriales, and Burkholderia and unclassified Enterobacteriaceae, in men and women, respectively. Peripheral immune cell profiling analysis revealed that in men, probiotics significantly reduced the proportions of dendritic cells and CD14+ CD16- monocytes; however, these effects were not observed in women. In contrast, the proportion of total CD4+ T cells was significantly reduced in women in the probiotic group. Additionally, serum lipopolysaccharide-binding protein levels showed a decreasing tendency that were positively associated with changes in gut bacteria, including Catabacter (ρ = 0.678, P < 0.05) and Burkholderia (ρ = 0.673, P < 0.05) in men and women, respectively. CONCLUSIONS These results suggest that probiotic supplementation may reduce the incidence of inflammation-related diseases by regulating the profiles of the gut microbiota and peripheral immune cells in healthy elders in a sex-specific manner.
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Gut microbiota indole-3-propionic acid mediates neuroprotective effect of probiotic consumption in healthy elderly: A randomized, double-blind, placebo-controlled, multicenter trial and in vitro study.
Kim, CS, Jung, S, Hwang, GS, Shin, DM
Clinical nutrition (Edinburgh, Scotland). 2023;(6):1025-1033
Abstract
BACKGROUND & AIMS The beneficial effects of probiotic consumption on age-related decline in cerebral function have been previously reported in the literature; however, the mechanistic link between gut and brain interactions has not yet been fully elucidated. Therefore, this study aimed to identify the role of gut microbiota-derived metabolites in gut-brain interactions via blood metabolomic profiling analysis in clinical trials and in vitro mechanistic studies. METHODS A randomized, double-blind, placebo-controlled, multicenter clinical trial was conducted in 63 healthy elderly individuals (≥65 years of age). Participants were administered either placebo (placebo group, N = 31) or probiotic capsules (Bifidobacterium bifidum BGN4 and Bifidobacterium longum BORI; probiotics group, N = 32) for 12 weeks. Global and targeted metabolomic profiling analyses of their blood samples were then performed using 1H nuclear magnetic resonance and liquid chromatography-mass spectrometry methods, both at baseline and at the end of the trial. Gut microbial analysis was conducted using the 16S ribosomal ribonucleic acid gene sequencing method. Subsequently, microglial BV2 cells were treated in vitro with indole-3-propionic acid (IPA) following lipopolysaccharide stimulation, and neuronal SH-SY5Y cells were treated with conditioned media from the BV2 cells. Finally, the levels of pro-inflammatory cytokines in BV2 cells and neurotrophins in SH-SY5Y cells were quantified using a real-time polymerase chain reaction or enzyme-linked immunosorbent assay. RESULTS The metabolomic profiling analyses showed that probiotic consumption significantly altered the levels of metabolites involved in tryptophan metabolism (P < 0.01). Among these metabolites, gut microbiota-produced IPA had a 1.91-fold increase in the probiotics group (P < 0.05) and showed a significant relation to gut bacterial profiles (P < 0.01). Elevated IPA levels were also positively associated with the level of serum brain-derived neurotropic factor (BDNF) in the probiotics group (r = 0.28, P < 0.05), showing an inverse trend compared to the placebo group. In addition, in vitro treatment with IPA (5 μM) significantly reduced the concentration of proinflammatory TNF-α in activated microglia (P < 0.05), and neuronal cells cultured with conditioned media from IPA-treated microglia showed a significant increase in BDNF and nerve growth factor production (P < 0.05). CONCLUSIONS These results show that gut microbiota-produced IPA plays a role in protecting the microglia from inflammation, thus promoting neuronal function. Therefore, this suggests that IPA is a significant mediator linking the interaction between the gut and the brain in the elderly with probiotic supplementation.
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Effect of chewing gum on anxiety in women undergoing elective cesarean section: a randomized controlled study.
Bang, YJ, Lee, EK, Kang, R, Kim, AH, Kim, CS, Sim, WS, Choi, SJ, Oh, SY, Roh, CR, Ko, JS
Annals of palliative medicine. 2023;(3):529-537
Abstract
BACKGROUND Preoperative anxiety is a common problem in pregnant women undergoing elective cesarean section. We aimed to determine the anxiolytic effects of chewing gum in pregnant women undergoing elective cesarean section under regional anesthesia. METHODS This was a single-center, prospective, randomized controlled trial. Sixty-six women were randomly assigned to either the control group (n=33) or gum group (n=33) in a 1:1 ratio. In the gum group, the participants chewed xylitol gum for at least 10 min/h, regardless of fasting. Gum chewing was started at 5 pm a day before surgery and continued till the participant entered the operation room. In the control group, participants were requested to follow fasting guidelines without further instruction. The primary outcome was preoperative anxiety measured using the Amsterdam Preoperative Anxiety and Information Scale (APAIS) immediately before surgery. RESULTS The APAIS score immediately before surgery showed no significant difference between the control and the gum group (19.2±5.8 vs. 19.1±4.1, P>0.99). There were no statistically significant differences in the eight items related to anxiety: unfitness, concentration difficulty, hunger, thirst, dry mouth, fatigue, headache, and nausea. However, the pain score during the procedure of combined spinal epidural anesthesia was significantly lower in the chewing gum group [4 (IQR, 3-5.5)] than in the control group [5 (IQR, 3-7), P=0.045]. CONCLUSIONS Preoperative gum chewing did not reduce anxiety levels measured immediately before entering the operating room in the participants undergoing elective cesarean section. TRIAL REGISTRATION Clinical Trial Registry of Korea: https://cris.nih.go.kr/cris/index.jsp and identifier: KCT0006602; date of registration: September 27, 2021; principal investigator's name: RyungA Kang.
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Marine Biological Macromolecules and Chemically Modified Macromolecules; Potential Anticoagulants.
Chandika, P, Tennakoon, P, Kim, TH, Kim, SC, Je, JY, Kim, JI, Lee, B, Ryu, B, Kang, HW, Kim, HW, et al
Marine drugs. 2022;(10)
Abstract
Coagulation is a potential defense mechanism that involves activating a series of zymogens to convert soluble fibrinogen to insoluble fibrin clots to prevent bleeding and hemorrhagic complications. To prevent the extra formation and diffusion of clots, the counterbalance inhibitory mechanism is activated at levels of the coagulation pathway. Contrariwise, this system can evade normal control due to either inherited or acquired defects or aging which leads to unusual clots formation. The abnormal formations and deposition of excess fibrin trigger serious arterial and cardiovascular diseases. Although heparin and heparin-based anticoagulants are a widely prescribed class of anticoagulants, the clinical use of heparin has limitations due to the unpredictable anticoagulation, risk of bleeding, and other complications. Hence, significant interest has been established over the years to investigate alternative therapeutic anticoagulants from natural sources, especially from marine sources with good safety and potency due to their unique chemical structure and biological activity. This review summarizes the coagulation cascade and potential macromolecular anticoagulants derived from marine flora and fauna.
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Consumption of 85% cocoa dark chocolate improves mood in association with gut microbial changes in healthy adults: a randomized controlled trial.
Shin, JH, Kim, CS, Cha, L, Kim, S, Lee, S, Chae, S, Chun, WY, Shin, DM
The Journal of nutritional biochemistry. 2022;99:108854
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Plain language summary
Disturbances in a person’s mood interrupts their personal well-being and the ability to participate in social interactions, leading to physical health problems such as chronic diseases. The role of diet as a mood regulator has received a great deal of interest. Certain dietary components have been shown to reduce anxiety and depression and improve quality of life. The aim of this study was to investigate the effects of dark chocolate intake on mood in everyday life, with special emphasis on the gut-brain axis. This study is a randomized controlled trial. Participants who met the criteria for eligibility were randomly assigned to one of three groups: (1) control group (CON, n=14); 2) 85% cocoa chocolate group (DC85, n=18); and 3) 70% cocoa chocolate group (DC70, n=16). Results show that daily intake of dark chocolate significantly reduced negative affect in the DC85, but not in the DC70. Furthermore, gut microbial diversity was significantly higher in DC85 than the CON. Authors conclude that dark chocolate has prebiotic effects by restructuring the diversity and composition of the gut microbiome, which may in turn improve mood via the gut-brain axis.
Expert Review
Conflicts of interest:
None
Take Home Message:
- To highlight the potential benefits of high cocoa content dark chocolate in relation to mental states
- To promote more awareness of how dietary habits may impact emotional wellbeing
- To emphasise the importance of microbiota and the gut-brain axis regarding dietary habits.
Evidence Category:
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X
A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)
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B: Systematic reviews including RCTs of limited number
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C: Non-randomized trials, observational studies, narrative reviews
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D: Case-reports, evidence-based clinical findings
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E: Opinion piece, other
Summary Review:
Background
The authors highlight that dark chocolate has been continually identified for its effects on mood. However, there is a dearth of evidence concerning the emotional impact of daily consumption of dark chocolate. Hence, the impact of dark chocolate consumption on daily mood, focusing on the gut-brain axis, is being investigated in this study.
Objectives
- To evaluate the correlation between the effect on emotional state after consuming dark chocolate and the gut microbiota in healthy adults
- To identify alterations in the composition and diversity of the microorganisms in the gastrointestinal tract on account of dark chocolate intake.
Study Design
A randomised controlled trial was performed at Seoul National University from July to December 2017, This involved. consumption of two types of dark chocolate (70% and 85% cocoa content). Subjects in the treatment groups were blinded although investigators and the control cohort were unblinded.
Participants
117 individuals were screened. However, 48 healthy males and females aged 20-30 years were eligible at baseline.
Interventions
- Subjects (n=16): Consumed 30g/day of 70% cocoa chocolate for 3 weeks
- Participants (n=18): Consumed 30g/day of 85% cocoa chocolate for 3 weeks
- Participants (n=14): The control group consumed no chocolate for 3 weeks.
Main Health Outcomes Measured
- Mood states were quantified via the Positive and Negative Affect Schedule in tandem with Microbiota analysis pre- and post-experiment
- Body composition analysis and dietary assessment were also conducted pre- and post-intervention
- Faecal 16S rRNA sequencing analysis of bacterial genomic DNA was conducted for the cohort who consumed 85% cocoa chocolate and the control arm to evaluate the association between the mood-altering effects of dark chocolate and the gut microbiota
- Statistical tests were performed based on intention-to-treat analysis. The Chi-squared test, Kruskal-Wallis test, one-way ANOVA, unpaired t-test and Mann-Whitney U test were employed for inter-group analysis. Spearman's correlation analysis was used to assess the association between gut microbiota composition and mood scores and P<.05 was considered statistically significant.
Results
- Daily intake of dark chocolate substantially diminished negative emotional states in the cohort consuming 85% cocoa content, but not in the 70% cocoa treatment arm
- Gut microbial diversity was substantially greater in the 85% cacao cohort than the control group (P<.05)
- Blautia obeum levels were significantly elevated and Faecalibacterium prausnitzii levels were decreased in the 85% cacao cohort than the control arm (P<.05).
- Furthermore, it was observed that changes in negative affect scores were inversely correlated with diversity and relative abundance of Blautia obeum (P<.05).
Conclusions
The observations suggest that consumption of dark chocolate with a higher cocoa content may induce prebiotic effects due to its capacity to restructure the diversity and composition of the gut microbiota. Furthermore, consuming dark chocolate with a higher cocoa might exert a positive effect on negative emotional states through the gut-brain axis.
Clinical practice applications:
- To inform practitioners of the benefits of 30g/day high (85%) cocoa chocolate consumption and its potential positive impact on mood through the gut-brain axis
- To educate clients regarding the potential benefits of daily high cocoa content chocolate consumption and its possible favourable effect on emotional states associated with gut microbiota.
Considerations for future research:
- More extensive research could investigate interventions of a longer period
- Further studies could evaluate if any difference exists between cocoa and cacao consumption and emotional states via the gut-brain axis, and the strength of any associations
- Interventions could investigate which strains of bacteria that high cocoa content dark chocolate may affect.
Abstract
Dark chocolate has long been recognized for its mood-altering properties; however, the evidence regarding the emotional effects of daily dark chocolate intake is limited. Therefore, we aimed to investigate the effects of dark chocolate intake on mood in everyday life, with special emphasis on the gut-brain axis. Two different dark chocolates (85% and 70% cocoa content) were tested in this study. In a randomized controlled trial, healthy adults (20-30 y) consumed either 30 g/d of 85% cocoa chocolate (DC85, n=18); 70% cocoa chocolate (DC70, n=16); or no chocolate (control group, CON; n=14); for 3 weeks. Mood states were measured using the Positive and Negative Affect Schedule (PANAS). Daily consumption of dark chocolate significantly reduced negative affect in DC85, but not in DC70. To assess the association between the mood-altering effects of dark chocolate and the gut microbiota, we performed fecal 16S rRNA sequencing analysis for the DC85 and CON groups. Gut microbial diversity was significantly higher in DC85 than CON (P<.05). Blautia obeum levels were significantly elevated and Faecalibacterium prausnitzii levels were reduced in DC85 compared to CON (P<.05). Furthermore, we found that the observed changes in negative affect scores were negatively correlated with diversity and relative abundance of Blautia obeum (P<.05). These findings indicate that dark chocolate exerts prebiotic effects, as evidenced by its ability to restructure the diversity and abundance of intestinal bacteria; thus, it may improve negative emotional states via the gut-brain axis.
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Escherichia coli small molecule metabolism at the host-microorganism interface.
Gatsios, A, Kim, CS, Crawford, JM
Nature chemical biology. 2021;(10):1016-1026
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Abstract
Escherichia coli are a common component of the human microbiota, and isolates exhibit probiotic, commensal and pathogenic roles in the host. E. coli members often use diverse small molecule chemistry to regulate intrabacterial, intermicrobial and host-bacterial interactions. While E. coli are considered to be a well-studied model organism in biology, much of their chemical arsenal has only more recently been defined, and much remains to be explored. Here we describe chemical signaling systems in E. coli in the context of the broader field of metabolism at the host-bacteria interface and the role of this signaling in disease modulation.
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Probiotic Supplementation Improves Cognitive Function and Mood with Changes in Gut Microbiota in Community-Dwelling Older Adults: A Randomized, Double-Blind, Placebo-Controlled, Multicenter Trial.
Kim, CS, Cha, L, Sim, M, Jung, S, Chun, WY, Baik, HW, Shin, DM
The journals of gerontology. Series A, Biological sciences and medical sciences. 2021;76(1):32-40
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Plain language summary
Aging is characterized by progressive decline in biological functions of the organism. Diet is one of the critical lifestyle factors for physical and mental well-being throughout the life span, including later life. The aim of this study was to investigate the effects of probiotics consumption on intestinal and brain health in elders over the age of 65. This study is a randomised, double-blind, placebo-controlled, multicentre trial. All participants, study coordinators, and researchers were blinded throughout the entire study. Sixty-three participants were randomized, with 31 and 32 subjects in the placebo and probiotics group, respectively. Results demonstrate that probiotics have system-wide effects on the gut–brain axis in healthy community-dwelling older adults by promoting cognitive and mental health and changing the gut microbial composition. Authors conclude that their findings provide evidence that probiotics have health-promoting properties as part of a healthy diet in the general population of independently living older adults.
Abstract
Probiotics have been proposed to ameliorate cognitive impairment and depressive disorder via the gut-brain axis in patients and experimental animal models. However, the beneficial role of probiotics in brain functions of healthy older adults remains unclear. Therefore, a randomized, double-blind, and placebo-controlled multicenter trial was conducted to determine the effects of probiotics on cognition and mood in community-dwelling older adults. Sixty-three healthy elders (≥65 years) consumed either placebo or probiotics containing Bifidobacterium bifidum BGN4 and Bifidobacterium longum BORI for 12 weeks. The gut microbiota was analyzed using 16S rRNA sequencing and bioinformatics. Brain functions were measured using the Consortium to Establish a Registry for Alzheimer's disease, Satisfaction with life scale, stress questionnaire, Geriatric depression scale, and Positive affect and negative affect schedule. Blood brain-derived neurotrophic factor (BDNF) was determined using enzyme-linked immunosorbent assay. Relative abundance of inflammation-causing gut bacteria was significantly reduced at Week 12 in the probiotics group (p < .05). The probiotics group showed greater improvement in mental flexibility test and stress score than the placebo group (p < .05). Contrary to placebo, probiotics significantly increased serum BDNF level (p < .05). Notably, the gut microbes significantly shifted by probiotics (Eubacterium and Clostridiales) showed significant negative correlation with serum BDNF level only in the probiotics group (RS = -0.37, RS = -0.39, p < .05). In conclusion, probiotics promote mental flexibility and alleviate stress in healthy older adults, along with causing changes in gut microbiota. These results provide evidence supporting health-promoting properties of probiotics as a part of healthy diet in the older adults.