PONE-D-21-03589

Effect of zinc deficiency on chronic kidney disease progression: A retrospective cohort study

PLOS ONE

Dear Dr. Kanda,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please respond to the additional editor comments as well as the reviewer's comments.

Please submit your revised manuscript by Apr 18 2021 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

• A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols

We look forward to receiving your revised manuscript.

Kind regards,

Kojiro Nagai

Academic Editor

PLOS ONE

Journal Requirements:

When submitting your revision, we need you to address these additional requirements.

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at

https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and

https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf

2. We note that you have indicated that data from this study are available upon request. PLOS only allows data to be available upon request if there are legal or ethical restrictions on sharing data publicly. For information on unacceptable data access restrictions, please see http://journals.plos.org/plosone/s/data-availability#loc-unacceptable-data-access-restrictions.

In your revised cover letter, please address the following prompts:

a) If there are ethical or legal restrictions on sharing a de-identified data set, please explain them in detail (e.g., data contain potentially identifying or sensitive patient information) and who has imposed them (e.g., an ethics committee). Please also provide contact information for a data access committee, ethics committee, or other institutional body to which data requests may be sent.

b) If there are no restrictions, please upload the minimal anonymized data set necessary to replicate your study findings as either Supporting Information files or to a stable, public repository and provide us with the relevant URLs, DOIs, or accession numbers. Please see http://www.bmj.com/content/340/bmj.c181.long for guidelines on how to de-identify and prepare clinical data for publication. For a list of acceptable repositories, please see http://journals.plos.org/plosone/s/data-availability#loc-recommended-repositories.

We will update your Data Availability statement on your behalf to reflect the information you provide.

Additional Editor Comments:

The authors investigated the relationship between Zn deficiency and the progression of CKD.

I understand the novelty of this study. However, I wonder if the risk of Zn deficiency was overestimated, because there seems to be no quantitative evaluation of proteinuria in this study, which is one of the well-known risk factors for CKD progression. Therefore, I suggest to add the analysis of one more Cox proportional hazards model adjusted for age, male, BMI, DM, cardiovascular disease, ln(eGFR), ln(CRP), serum albumin levels, hemoglobin levels (deletion of dipstick proteinuria from model 3), because I guess that the simple estimation of proteinuria in this study may affect the results.

In addition, there are many factors to influence the progression of CKD such as the intake of immunosuppressant drugs and the management of hypertension and diabetes during the observational period. It is better to add those data. If they are not available, it should be noted in the limitation of this study.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: General comments

This manuscript reported the effect of zinc deficiency on the decline in kidney function in CKD patients from single-center, retrospective cohort study. This study contains some novel information, however, there are some concerns that should be discussed.

Comments

1. Was dietary guidance, such as cocoa, given to the low zinc group?

2. Were there any cases in which the changes in zinc level could be followed? If there were any cases, did changes in zinc level affect the prognosis?

3. The authors need to evaluate the bias of measuring zinc levels. Is the timing of the zinc measurement outpatient? Or during hospitalization for some event?

4. Is the association between zinc levels and hypoalbuminemia due to proteinuria or due to low nutrition?

Reviewer #2: The authors retrospectively examined the association between Zn levels and the hard outcome of ESKD or death using historical electronic medical records. The results suggest that low Zn is a significant risk and a poor prognosis, especially in the hypoalbuminemic group. This study is thought to be suggestive in terms of clinical management and nutrition of CKD patients. However, there are several points of concern that we would like to mention below.

Comments to the author

1) The low Zn group has significantly worse nephrotic syndrome, hypoalbuminemia, dyslipidemia, impaired renal function, and anemia. In fact, in Fig. 3, the significance of the results was reduced when ln(CRP), serum albumin, hemoglobin levels and dipstick proteinuria were added to the correction, suggesting that these factors may be associated with prognosis. Based on this, the authors conducted a propensity score-matched analysis. The authors need to provide the reason why they selected the baseline characteristics [age, sex, BMI, DM, cardiovascular disease, ln(eGFR), ln(CRP), serum albumin levels, hemoglobin levels, dipstick proteinuria, and use of angiotensin II receptor blockers (ARBs) or angiotensin-converting enzyme (ACE) inhibitors] for adjustment in regression models and calculation of propensity score.　If there were unmeasured confounders such as use of ESA, please state in the limitation section.

2) As with RAS inhibitors, diuretics, which have a significant impact on renal function trends, should be added as a correction factor.

3) Since hypoalbuminemia due to nephrotic syndrome can lead to both decreased Zn and decreased renal function, the possibility that hypoalbuminemia is a bystander cannot be denied. For greater reliability, it is better that urine protein quantification would be included in the analysis. If urine protein quantification is not sufficiently available, this should be noted in the limitation.

4) As the authors mentioned in the DISCUSSION, the most important point is whether Zn supplementation is effective or not. How many of the patients in this study were newly started on zinc during the observation period? What is the relationship between new initiation of zinc and prognosis?

Reviewer #3: Tokuyama et al. reported a retrospective cohort study that clarified zinc deficiency as a risk of CKD progression in patients with CKD, in which authors used cox proportional hazards models and propensity score-matched analysis. In addition, authors showed the association between serum zinc levels and albumin levels, and concluded hypoalbuminemia affected the relationship between zinc and outcomes. This study and statistical analysis were well designed, and clearly showed the effect of zinc deficiency on CKD progression.

Major comment

(1) In figure 6, authors presented the effect of zinc deficiency on outcome in low-albumin patients and high-albumin patients in which concluded no association between zinc deficiency and outcome in high albumin patients. However, it is not clear why there is the difference of zinc-associated outcome between both groups. Authors should describe the possible mechanisms or hypothesis that zinc deficiency affect the outcome in low-albumin groups.

(2) A title is “Effect of zinc deficiency on chronic kidney disease progression”. If there is no association of zinc deficiency and outcome in CKD patients with high albumin group, a title may mention the effect of hypoalbuminemia on the relationship between zinc deficiency and outcome.

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

Attachments

Attachment

Submitted filename: comment to PONE-D-21-03589.docx

Effect of zinc deficiency on chronic kidney disease progression and effect modification by hypoalbuminemia

PONE-D-21-03589R1

Dear Dr. Kanda,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Kojiro Nagai

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

Reviewer #3: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Partly

Reviewer #3: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: (No Response)

Reviewer #3: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: In this manuscript, the authors revised their manuscript in accordance with our review. This manuscript fulfilled our suggestion.

Reviewer #2: (No Response)

Reviewer #3: The manuscript has been revised accordingly, and I have no further comments to be addressed for the revized manuscript.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

Reviewer #3: No