Effect of Oral Administration of Lactiplantibacillus plantarum SNK12 on Temporary Stress in Adults: A Randomized, Placebo-Controlled, Double-Blind, Parallel-Group Study

Round 1

Reviewer 1 Report

The authors have adressed an interesting and chaklenging topic - the effect of probiotics on the stress-ralated phenomena in humans. The authrs show that administration of a probiotic preparation of L. plantarum SNK12 reduced the stress indiators in the test groups compared the controls.

While the results are interesting, the authors should address certain points to help an uninitiated reader to properly understand the study.

1. As an editorial point, the up to date bacterial taxonomy should be used. The former Lactobacills plantarum is now Lactiplantibacillus plantarum.

2. The authors should also justify their experimental design. Since the everyday life of volunteers cannot be standardized, and there is always the possibility that the controls for some reason were subjected to more stress that the test goup during the administration and the follow up. Therefore , one coulf think that a cross over design would have been more approppriate.

3. The authors mention both in the Abstract and in the Introduction that Uchida-Kraepelin test was used to assess the stress load. Howevdr, the use of this test is not described in the Materials and Methods. As mosgt microbiologists and probably also gastroenterologists are not familiar with this test, the purpose and stage of its use should be addressed.

4. Both low and high dose of SNK12 was tested. Can the authors indicate any dose response or an optimal dose for the reduction of stress response reduction?

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Article is well written; however, some modifications are required.

1. Throughout the manuscript, name of bacteria will be in italics.

2. Background history of research and knowledge gap are necessary to mention in introduction.

3. In discussion part, mentioned biochemical mechanisms are needed to describe by schematic diagram. It will help reader for better understanding. 

4. Conclusion section will be separate heading. Further scope and limitation of present research are needed to mention.

5. Protocols, mentioned in sections 2.5-2.9 are needed to mention by references.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

This is a novel study on the effect of L. plantarum on temporary stress. The objective and experimental design were made clear. The results and discussions have high scientific merit. Thus I recommend this paper to be published with minor spelling checks eg. Table 4 and 5 the word 'Means' was spelled incorrectly.

Author Response

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Reviewer 4 Report

In the present paper, Takumi Watanabe and colleagues investigated in a randomized, placebo-controlled, double-blind, parallel-group study, the efficacy of Lactobacillus plantarum SNK12 (SNK) ingestion against stress in healthy adults. The authors concluded that SNK ingestion could relieve stress (negative feelings, anxiety, tension, embarrassment, confusion, anger, and hostility) resulting from the temporary load caused by work and study.  

Overall, I think that the paper could be of interest for readers and researchers, in general, on a current topic of research.

I make some suggestions for improve the quality of the manuscript.

1) Have you analyzed the nutritional status of patients included in this analysis? Please explain. The authors, if possible, should incorporate in tables the dietary pattern of the patients included in the present study (e. Mediterranean-style diet, Plants-based diet, Nordic dietary pattern, etc.); in this way, I feel that the readers can better understand the results obtained in the present clinical study.

2) “Oriental diet” is particularly abundant in isoflavones. So, the positive effects on stress observed in the present study could be related to these phytochemicals, particularly in women. Please discuss this aspect in the manuscript considering for your convenience these references (D’Anna R. et al. Menopause. 2009, 16, 301-306; Squadrito F. et al. J. Clin. Endocrinol. Metab. 2013, 98, 3366-3374; Ma L. et al. Circulation. 2020, 141, 1127-1137; Marini, H.R. Nutrients, 2022, 14, 1550; Kang I. et al. Nutr Res Pract. 2022, 16 (Suppl 1): S147-S159; Leonard L.M. et al. Nutrients. 2022, 14(3): 553; Ceccarelli I. et al. Neurosci Biobehav Rev. 2022, 132: 648-663.).

3) Please better define and discuss the power analysis of study.

4) Does the authors plan to assess microbioma composition in this population? Please make a comment in the discussion section of manuscript.

5) In light of the results here obtained, please to discuss on the possible application of nutraceutics and/or antioxidants/antinflammatory and/or paraprobiotics compounds (as SNK) that, in combination with healthy diet and physical activity could provide a possible further strategy to ameliorate stress symptoms in healthy adults.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Responses from Authors are satisfactory. I am suggesting to accept the manuscript.

Reviewer 4 Report

Thank you for addressing my comments well. I have no further remarks.

 

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.