Protective Effects of Bifidobacterium Breve MCC1274 as a Novel Therapy for Alzheimer’s Disease
, Makoto Michikawa 5,* and Cha-Gyun Jung 6,*
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors
The article thoroughly presents and summarizes the role of the B. breve MCC1274 probiotic in the prevention and treatment of Alzheimer's disease and cognitive decline. Research indicates that the probiotic reduces neuroinflammation and improves cognitive function, particularly in individuals with mild cognitive impairment, a finding supported by numerous studies, which is excellently summarized in this article. Additionally, B. breveMCC1274 helps alleviate symptoms of anxiety and depression. The language is scientific and well-structured, and the claims are convincing. The article has a low plagiarism index (15%), and the references (164) are relevant.
Additional comments on my review: the research topic is relevant because the effects of probiotic treatments on brain inflammation and neurodegenerative diseases have not been sufficiently studied, and the article offers a new approach to investigating the relationship between probiotic treatments and Alzheimer's disease, considering the changes in synaptic protein levels. The conclusions are consistent with the presented data and studies. The references are relevant. The article is thorough and very detailed, but in some cases, the methodological details are not sufficiently elaborated. For example, the detailed description of the experimental models used and their limitations is not emphasized enough. The article mentions the increase in synaptic protein levels, but what is the exact mechanism behind this? An important question is also how human clinical studies could potentially change positions on probiotic treatments, especially in Alzheimer's disease. How do probiotic treatments affect patients' central nervous system inflammation and the progression of neurodegenerative diseases based on long-term studies? I recommend the publication of the article. The tables and figures illustrate the results well.
Author Response
Thank you for allowing us to submit a revised draft of our manuscript titled (Protective effects of Bifidobacterium breveMCC1274 as a novel therapy for Alzheimer’s disease) to the Journal of Nutrients. We appreciate the time and effort you and the reviewers dedicated to providing valuable feedback on our manuscript. We are grateful to the reviewers for their insightful comments on our review. We have been able to incorporate changes to reflect all the suggestions provided by the reviewers. We have highlighted the changes within the manuscript. Here is a point-by-point response to the reviewers’ comments and concerns.
Comments from reviewer 1:
The article thoroughly presents and summarizes the role of the B. breve MCC1274 probiotic in the prevention and treatment of Alzheimer's disease and cognitive decline. Research indicates that the probiotic reduces neuroinflammation and improves cognitive function, particularly in individuals with mild cognitive impairment, a finding supported by numerous studies, which is excellently summarized in this article. Additionally, B. breveMCC1274 helps alleviate symptoms of anxiety and depression. The language is scientific and well-structured, and the claims are convincing. The article has a low plagiarism index (15%), and the references (164) are relevant.
Response:
Thank you for your positive and constructive feedback on our article.
The research topic is relevant because the effects of probiotic treatments on brain inflammation and neurodegenerative diseases have not been sufficiently studied, and the article offers a new approach to investigating the relationship between probiotic treatments and Alzheimer's disease, considering the changes in synaptic protein levels. The conclusions are consistent with the presented data and studies. The references are relevant.
The article is thorough and very detailed, but in some cases, the methodological details are not sufficiently elaborated. For example, the detailed description of the experimental models used and their limitations is not emphasized enough.
>>>> Thank you for your suggestion. The experimental models used, and their limitations were added in the manuscript in lines No 678-685, 695-699, 702-705, 712-716, 718-722, and 732-736 (mice received intracerebroventricular injections of Aβ 1–42 solution which contained a mixture of monomeric and oligomer forms of Aβ, resulting in a significant reduction in alternation behavior during the Y-maze test compared to control mice, which indicated im-paired working memory. Living, heat-killed, or sonicated B. breve MCC1274 were orally administered to the mice daily by gavage 1 × 109 organisms in 0.2 ml, starting 2 days before Aβ injection. Daily probiotic administration notably improved this working memory impairment. However, the main limitation of this study is uses mice which may not fully replicate human AD pathology or the complexity of cognitive impairments This study used syn-thetic Aβ proteins (Aβ25–35 and Aβ1–42), which may not fully represent the complexity of the natural amyloid pathology seen in AD patients, especially regarding the presence of other pathological features like tau tangles. In this study, three-month-old AppNL−G−F mice were assigned randomly into the vehicle and probiotic groups: the vehicle group (n = 26) received saline, and the probiotic group (n = 26) was supplemented with B. breve MCC1274 (1×109 cfu/5.56 mg/200 µl saline/mouse) via oral gavage five times/week for four months. However, the main limitation of this study is the limited exploration of mechanisms; although the study mentions the reduction of Aβ and microglial activation, the precise mechanisms by which B. breve MCC1274 affects these processes such as gut-brain axis interactions or immune modulation are not fully explored, which limits understanding of how the probiotic exerts its effects. The transgenic mice used in the experiments were aged 13 months. The mice were administered B. breve MCC1274 (1 × 109 cfu/mouse/day) via oral gavage five times per week for four months (n = 17). Another group of mice that received saline was considered the control group (n = 16). However, the main limitation of this study is behavior testing, they only used NOR test for cognition. They have not conducted comprehensive or diverse behavioral tests to assess all aspects of cognitive function and memory. In addition to no Long-Term Follow-up to assess whether the improvements in memory are sustained over time or if any adverse effects emerge after prolonged probiotic use.
The article mentions the increase in synaptic protein levels, but what is the exact mechanism behind this?
>>>> Thank you for your suggestion. The exact mechanism behind the synaptic improvement is unknown, however, these studies referred this improvement to amyloid and chronic stress reduction. Which have been added to lines 636-639, 642-645, and 649-651. While the study does not directly explore the molecular pathways involved in synaptic improvement, it suggests that the reduction of Aβ and microglial activation, along with the modulation of inflammation, are central to the observed improvements in synaptic health and memory function. In this study, B. breve MCC1274 activates the AKT/GSK3β pathway, which reduces tau phosphorylation and lowers PS1 protein levels in the hippocampus. This results in decreased production of soluble AB42, leading to a reduction in neuroinflammation. Ultimately, this may help improve synaptic function. B. breve MCC1274 administration decreased chronic stress in this study. This decrease in chronic stress may contribute to inhibiting tau hyperphosphorylation and enhancing synaptic density.
An important question is also how human clinical studies could potentially change positions on probiotic treatments, especially in Alzheimer's disease.
>>>> Human clinical studies could play a crucial role in transforming the potential of probiotics as a treatment for AD by providing direct evidence of their effectiveness in humans. While animal studies suggest promising results, clinical trials would determine the appropriate dosage, treatment duration, and long-term safety, identifying any side effects. These studies would also clarify how probiotics influence mechanisms like Aβ accumulation, neuroinflammation, and synaptic health in humans. Additionally, clinical trials could lead to more personalized treatment approaches, comparing the effectiveness of probiotics with existing AD therapies and confirming cognitive improvements. Ultimately, positive results from well-conducted human studies could pave the way for regulatory approval, making probiotics a recognized, safe, and accessible therapy for AD.
How do probiotic treatments affect patients' central nervous system inflammation and the progression of neurodegenerative diseases based on long-term studies?
>>>> Recent studies involving patients with neurodegenerative diseases have typically lasted between 8 to 24 weeks, which is not considered a long-term duration. However, preliminary data from these studies indicate that the probiotic B. breve may have beneficial effects on neurodegenerative diseases. Long-term studies could provide further evidence that B. breve helps reduce neuroinflammation and slows the progression of neurodegenerative diseases by influencing the gut-brain axis and immune responses. B. breve may promote a healthy gut microbiota, which can lower systemic inflammation and prevent the chronic neuroinflammation associated with conditions such as AD and PD. It may also decrease microglial activation and inflammatory cytokines, thereby protecting neurons and synapses from damage. Additionally, B. breve could enhance neuroprotective factors like brain-derived neurotrophic factor, which supports neuronal survival and cognitive function.
Reviewer 2 Report
Comments and Suggestions for Authors
Dear Authors,
The manuscript "Protective Effects of Bifidobacterium breve MCC1274 as a Novel Therapy for Alzheimer’s Disease" addresses a critical and timely subject. Alzheimer’s disease (AD), the most prevalent form of dementia, significantly impacts daily life through memory impairment and currently lacks effective treatments to modify its progression.
The probiotic Bifidobacterium breve MCC1274 (B. breve MCC1274) demonstrates promising potential to enhance cognitive functions, prevent memory decline, reduce amyloid-β accumulation and tau phosphorylation, mitigate microglial activation, and increase synaptic protein levels.
This review provides a comprehensive analysis of B. breve MCC1274’s potential in preventing and treating AD, highlights its broader health benefits, and explores future research directions for this innovative probiotic therapy.
Please find below the key issues identified in your manuscript, along with recommended revisions to enhance clarity and impact:
Section 1: Alzheimer's Disease
The introduction provides a detailed background on AD, its clinical features, and pathophysiology. It is well-written and sets the stage for the study's rationale. However, integrating a more direct link to the role of probiotics could enhance the narrative flow.
Critique:
· Clarity: The text delves into extensive detail on AD pathology, which, while informative, risks overshadowing the main focus of the manuscript. Condense this section to maintain relevance.
· Linkage: The transition to probiotics as a solution appears abrupt. Consider a bridging paragraph to connect AD pathology with gut microbiota involvement.
Section 2: Role of Gut Microbiota in Neurodegenerative Diseases
This section is comprehensive, detailing the gut-brain axis and its implications for neurodegenerative diseases. The description of gut-derived metabolites like SCFAs and their neuroprotective properties is compelling.
Critique:
· Focus: The section occasionally diverges into generalized discussions on gut microbiota's role in various conditions, diluting the focus on AD. Streamline content to emphasize AD-specific mechanisms.
· References: Ensure citations are up-to-date, particularly for emerging studies on microbiota-based therapies.
Section 3: Gut-Brain Axis
The discussion of the gut-brain axis is clear and effectively highlights its bidirectional nature. The integration of neural, immune, and endocrine pathways adds depth to the argument.
Critique:
· Novelty: While informative, the section reiterates well-known concepts without offering novel insights. Consider focusing on unique aspects of B. breve MCC1274 interactions within this axis.
· Integration: Explicitly tie the gut-brain axis to the subsequent discussion of B. breve MCC1274 effects on AD.
Section 4: Probiotic Properties of B. breve MCC1274
The characterization of B. breve MCC1274 is thorough, outlining its biochemical properties, safety profile, and preclinical efficacy.
Critique:
· Impact: While detailed, the section could benefit from emphasizing the unique advantages of this strain over other probiotics.
· Data Presentation: Including a comparative table summarizing the effects of B. breve MCC1274 versus other strains could improve clarity.
Section 5: Mechanisms of Action
This section is the manuscript's core, meticulously explaining how B. breve MCC1274 modulates neuroinflammation, oxidative stress, and synaptic function.
Critique:
· Mechanistic Depth: The proposed mechanisms, though compelling, are sometimes speculative. Strengthen the argument with additional experimental evidence where possible.
· Visual Aids: Incorporating schematic diagrams could help elucidate complex pathways.
Section 6: Cognitive and Behavioral Effects
The findings on B. breve MCC1274's impact on cognition and behavior are promising, with clear connections to preclinical and clinical outcomes.
Critique:
· Quantitative Analysis: Include more statistical details to substantiate claims of cognitive improvement.
· Comparative Context: Discuss how these effects compare to existing AD treatments or other probiotics.
Section 7: Comparison with Other Probiotics
The comparative evaluation effectively positions B. breve MCC1274 in the broader context of probiotic research.
Critique:
· Comparative Metrics: The section lacks detailed metrics or criteria for comparison. Add more rigorous parameters to strengthen comparisons.
· Broader Implications: Expand on the translational potential of findings to human applications.
Conclusion and Future Directions
The conclusion aptly summarizes the findings and emphasizes the need for further research.
Critique:
· Specificity: The recommendations for future research are too general. Specify key areas, such as clinical trials or mechanistic studies, to guide subsequent investigations.
· Practical Applications: Highlight the potential implications for clinical practice or dietary supplementation.
Author Response
The manuscript "Protective Effects of Bifidobacterium breve MCC1274 as a Novel Therapy for Alzheimer’s Disease" addresses a critical and timely subject. Alzheimer’s disease (AD), the most prevalent form of dementia, significantly impacts daily life through memory impairment and currently lacks effective treatments to modify its progression.
The probiotic Bifidobacterium breve MCC1274 (B. breve MCC1274) demonstrates promising potential to enhance cognitive functions, prevent memory decline, reduce amyloid-β accumulation and tau phosphorylation, mitigate microglial activation, and increase synaptic protein levels.
This review provides a comprehensive analysis of B. breve MCC1274’s potential in preventing and treating AD, highlights its broader health benefits, and explores future research directions for this innovative probiotic therapy.Please find below the key issues identified in your manuscript, along with recommended revisions to enhance clarity and impact:
Comment 1:
Section 1: Alzheimer's DiseaseThe introduction provides a detailed background on AD, its clinical features, and pathophysiology. It is well-written and sets the stage for the study's rationale. However, integrating a more direct link to the role of probiotics could enhance the narrative flow.
Critique:
Clarity: The text delves into extensive detail on AD pathology, which, while informative, risks overshadowing the main focus of the manuscript. Condense this section to maintain relevance.
Linkage: The transition to probiotics as a solution appears abrupt. Consider a bridging paragraph to connect AD pathology with gut microbiota involvement.
Response 1:
Thank you for your valuable feedback and constructive critique. The bridging paragraph to connect AD pathology with gut microbiota involvement was added in lines 104-114 (Recent research has highlighted the significant role of gut microbiota in modulating brain function and its potential involvement in the pathophysiology of AD. The gut-brain axis, a bidirectional communication pathway between the central nervous system (CNS) and the gut, has been increasingly recognized as a critical factor in neuroinflammation and neurodegeneration observed in AD. Imbalances in the gut microbiota, known as dysbiosis, have been linked to heightened neuroinflammatory responses and cognitive decline. Given the emerging evidence supporting the influence of gut health on brain function, probiotics, beneficial bacteria that can help restore microbiome balance, are being explored as a promising therapeutic avenue to mitigate AD-related pathology. This shift in focus towards microbiome modulation offers a novel perspective on the prevention and treatment of AD, complementing traditional approaches).
Comment 2:
Section 2: Role of Gut Microbiota in Neurodegenerative Diseases
This section is comprehensive, detailing the gut-brain axis and its implications for neurodegenerative diseases. The description of gut-derived metabolites like SCFAs and their neuroprotective properties is compelling.
Critique:
Focus: The section occasionally diverges into generalized discussions on gut microbiota's role in various conditions, diluting the focus on AD. Streamline content to emphasize AD-specific mechanisms.
References: Ensure citations are up-to-date, particularly for emerging studies on microbiota-based therapies.
Response 2:
Thank you for your positive comment. This section outlines the general role of microbiota in inflammation, the blood-brain barrier, Aβ degrading enzymes, as well as behavior and cognitive function, all of which are crucial factors in the development of Alzheimer's disease. Additionally, newly published papers from 2024 and 2025 are cited in line 172, references 41-45.
Comment 3:
Section 3: Gut-Brain Axis
The discussion of the gut-brain axis is clear and effectively highlights its bidirectional nature. The integration of neural, immune, and endocrine pathways adds depth to the argument.
Critique:
Novelty: While informative, the section reiterates well-known concepts without offering novel insights. Consider focusing on unique aspects of B. breve MCC1274 interactions within this axis.
Integration: Explicitly tie the gut-brain axis to the subsequent discussion of B. breve MCC1274 effects on AD.
Response 3:
Thank you for your comment. In this section, we provided a general overview of the gut-brain axis and subsequently throughout the review, we discussed in detail how these probiotic influence immune pathways by affecting neuroinflammation. We also highlighted how these bacteria could reduce anxiety and depression scores in patients with schizophrenia by modulating the hypothalamic-pituitary-adrenal axis. Additionally, we noted that B. breve MCC1274 has been shown to partially reverse cognitive dysfunction in Aβ-injected mice, they refereed that certain structural components of probiotics may influence the neuronal immune response through vagus nerve stimulation.
Comment 4:
Section 4: Probiotic Properties of B. breve MCC1274
The characterization of B. breve MCC1274 is thorough, outlining its biochemical properties, safety profile, and preclinical efficacy.
Critique:
Impact: While detailed, the section could benefit from emphasizing the unique advantages of this strain over other probiotics.
Data Presentation: Including a comparative table summarizing the effects of B. breve MCC1274 versus other strains could improve clarity.
Response 4:
Thank you for your suggestion. Table 4 on page 21 for the comparison between B. breve MCC 1274 and other probiotics strains based on their effects on AD progression, Aβ deposition, and neuroinflammation.
Comment 5:
Section 5: Mechanisms of Action
This section is the manuscript's core, meticulously explaining how B. breve MCC1274 modulates neuroinflammation, oxidative stress, and synaptic function.
Critique:
Mechanistic Depth: The proposed mechanisms, though compelling, are sometimes speculative. Strengthen the argument with additional experimental evidence where possible.
Visual Aids: Incorporating schematic diagrams could help elucidate complex pathways.
Response 5 :
Thank you for your suggestion. B. breve MCC 1274 is a new strain of bacteria and in this review, we have covered all studies that have been done using this probiotic. Figure 1 on page 9 is a schematic diagram elucidating the beneficial pathways of B. breve MCC1274 on AppNL−G−F and WT mice.
Comment 6:
Section 6: Cognitive and Behavioral Effects
The findings on B. breve MCC1274's impact on cognition and behavior are promising, with clear connections to preclinical and clinical outcomes.
Critique:
Quantitative Analysis: Include more statistical details to substantiate claims of cognitive improvement.
Comparative Context: Discuss how these effects compare to existing AD treatments or other probiotics.
Response 6:
Statistical analysis tests which have been used for each study added in lines 717-718, 726-727, 741-742, 748-750, 758-760, 776-778, 779-801. Also, the effects of this probiotic compared to existing AD treatments or other probiotics have been added to lines 760-770 (As discussed, B. breve MCC1274 may have cognitive benefits comparable to or exceeding some AD treatments. It can potentially prevent cognitive decline in both AD model mice and MCI subjects while offering a safer side effect profile. However other treatments like cholinesterase inhibitors and memantine mainly provide symptomatic relief that can demonstrably improve cognitive function in individuals experiencing dementia, particularly in the early to moderate stages of AD with several side effects, although the improvement may be modest and not completely halt disease progression. Whereas B. breve MCC1274 may address underlying mechanisms and potentially slow disease progression. In addition, other probiotics such as Lactobacillus species and Bifidobacterium bifidum have also shown cognitive benefits, but their specific mechanisms and efficacy may vary). More details about the effect of other bacteria on cognitive function are mentioned in the comparison between this probiotic and others.
Comment 7:
Section 7: Comparison with Other Probiotics
The comparative evaluation effectively positions B. breve MCC1274 in the broader context of probiotic research.
Critique:
Comparative Metrics: The section lacks detailed metrics or criteria for comparison. Add more rigorous parameters to strengthen comparisons.
Broader Implications: Expand on the translational potential of findings to human applications.
Response 7:
Thank you for your suggestion. In this review, we are focusing on the effect of probiotics on brain health, AD progression, Aβ deposition, and neuroinflammation, and these points were mentioned in the comparison. Regarding human application we have added (While B. breve MCC1274 has demonstrated its effectiveness in improving cognition in subjects with MCI in several studies, other probiotics such as Lactobacillus fermentum, Lactobacillus plantarum, Bifidobacterium lactis, Lactobacillus acidophilus, Bifidobacterium bifidum, Bifidobacterium longum, Lactobacillus reuteri, Lactobacillus GG AT strain 53103, yogurt drinks containing Lactobacillus casei, Bifidobacterium infantis, and Lactobacillus rhamnosus do not appear to influence cognitive development in human [169-173]. In contrast, Lactobacillus plantarum p8 has been shown to significantly enhance social-emotional cognition in women and improve recognition memory in men following probiotic intervention compared to a placebo [174]. Additionally, multispecies probiotics containing Lactobacillus rhamnosus and Bifidobacterium lactis have been associated with improved cognitive function (mean difference of 1.90, 95% CI 1.09 to 2.70, p < 0.005), enhanced memory (mean difference of 4.60, 95% CI 2.91 to 6.29, p < 0.005) as measured by the MMSE and digit tasks, and a reduction in depressive symptoms (mean difference of 4.09, 95% CI 1.70 to 6.48, p < 0.005) according to the Beck Depression Inventory [175]) in lines 854-867.
Comment 8:
Conclusion and Future Directions
The conclusion aptly summarizes the findings and emphasizes the need for further research.
Critique:
Specificity: The recommendations for future research are too general. Specify key areas, such as clinical trials or mechanistic studies, to guide subsequent investigations.
Practical Applications: Highlight the potential implications for clinical practice or dietary supplementation.
Response 8:
Thank you for your comment. We have rewritten the future direction in lines 873-879 (The key areas for future research include investigating the effectiveness, safety, and optimal usage of B. breve MCC1274 in AD patients and those at risk, exploring the underlying mechanisms by which B. breve MCC1274 influences brain health and AD pathophysiology, examining combinations with pharmacological agents, dietary interventions, and other probiotics to enhance the benefits of B. breve MCC1274, developing tailored interventions based on individual microbiome and genetic profiles to maximize therapeutic outcomes).
Reviewer 3 Report
Comments and Suggestions for Authors
Authors presents a review that has differnt problems:
- Search methodic is not presented
- The idea that microbiote has a direct influence on brain health is speculative, most of the mansucript are on animals, but microbiome distribution and action are completly different from humans, as well as Alzhaimer disease model, they are just model, but often so far from human condition.
-Influence on overall health and particularly on cognitive and brain health by microbiome could cause but mre likely a consequence of non optimal gut health, due, for example to intolerance that causes stress and inflammation; for that is speculative to affirm that certainly microbiome is the cause or the consequence
- The main assessments are based on study on mice to much different from human
It could be seen globally as first step, but better analyzed, and stated that it is only a preliminar step
Author Response
Comment 1:
Search methodic is not presented.
Response 1:
Thank you for your comment. As this is a review article, the focus is on synthesizing existing literature rather than presenting a new search methodology. While we did not detail the search process as in primary research, we have referenced key studies transparently. However, to collect the studies a search of the databases, Web of Science, PubMed, and Google Scholar has been used.
Comment 2:
The idea that microbiote has a direct influence on brain health is speculative, most of the mansucript are on animals, but microbiome distribution and action are completly different from humans, as well as Alzhaimer disease model, they are just model, but often so far from human condition.
Response 2:
Thank you for your comment. While it is true that much of the evidence on the microbiome's influence on brain health comes from animal studies, these studies provide valuable insights into potential mechanisms of the gut-brain axis, such as inflammation and neurodegeneration, which may be relevant to humans. Despite limitations due to differences in microbiome composition and disease models, these findings lay the groundwork for future research. As the field progresses, there is a growing emphasis on human-specific studies, and some recent research explores the microbiome-brain link in humans. We agree that more human-focused data are needed to confirm and expand on the promising results from animal models and bridge the gap between species-specific research.
Comment 3:
Influence on overall health and particularly on cognitive and brain health by microbiome could cause but mre likely a consequence of non optimal gut health, due, for example to intolerance that causes stress and inflammation; for that is speculative to affirm that certainly microbiome is the cause or the consequence.
Response 3:
Thank you for your comment. You raise a valid point about the bidirectional relationship between the microbiome and health. Dysbiosis or suboptimal gut health, such as intolerance or inflammation, could indeed be a consequence of factors affecting both the microbiome and brain health, complicating the question of whether the microbiome is a cause or result of cognitive decline. While the causal relationship remains speculative, emerging evidence suggests that microbiome alterations may influence inflammation and stress, which can impact brain function. Future research, particularly longitudinal studies and controlled trials is needed to clarify whether microbiome changes precede or result from cognitive decline. We appreciate your insights and agree that understanding these dynamics is essential for advancing the gut-brain connection.
Comment 4:
The main assessments are based on study on mice to much different from human.
It could be seen globally as first step, but better analyzed, and stated that it is only a preliminar step.
Response 4:
Thank you for your comment. While it is true that many of the studies on the microbiome and brain health are based on animal models, particularly mice, it is important to note that some studies have also been conducted on humans. We agree that the findings from animal studies should be considered as a preliminary step, and we have framed them as such in our review. However, we also highlight the importance of recent human studies that support the emerging evidence and stress the need for further research to confirm these findings and better understand their relevance to human health.
Round 2
Reviewer 3 Report
Comments and Suggestions for Authors
The authors' answer did not satisfied my concerns, the main problems still remains.
