PONE-D-19-24289

The Effects of Omega-3 Fatty Acids on Proteinuria among Patients with Diabetes: A Meta-analysis of Randomized Controlled Trials

PLOS ONE

Dear Dr. Chewcharat,

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.

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Tomislav Bulum, MD, PhD

Academic Editor

PLOS ONE

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2. We noticed you have some minor occurrence of overlapping text with the following previous publication(s), which needs to be addressed:

- Hu, Jing, Zuoliang Liu, and Hao Zhang. "Omega-3 fatty acid supplementation as an adjunctive therapy in the treatment of chronic kidney disease: a meta-analysis." Clinics 72.1 (2017): 58-64.

- https://www.ahajournals.org/doi/pdf/10.1161/jaha.117.006020?download=true

 The text that needs to be addressed involves some sentences  of the Introduction.

In your revision ensure you cite all your sources (including your own works), and quote or rephrase any duplicated text outside the methods section. Further consideration is dependent on these concerns being addressed.

3. Please include your tables as part of your main manuscript and remove the individual files. Please note that supplementary tables (should remain/ be uploaded) as separate "supporting information" files

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Reviewers' comments:

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

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

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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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

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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

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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: Well done. The author had performed a good meta analysis to answer an important clinical question. Being a meta-analysis , I understand that some of the data eg the use of ACE-I/ARB were not available

Reviewer #2: Title: usually term ‘proteinuria among patients with diabetes’ denotes diabetic nephropathy.

Abstract: No issue except for conclusion. Please refer.

Introduction: The introduction states the gaps in knowledge which justifies a new metaAnalyses .

However, in the 2nd paragraph in reference to the line ‘ However, the effects of omega-3 fatty acids on kidney function still remain controversial particularly in diabetic kidney disease.’ I do not think word 'controversial' is right here. n-3 FAs are perceived to have a role in mediating inflammation, dyslipidemia etc. A more appropriate term would be 'lack of consensus’.

1st Line/Last paragraph/ 1st pp of introduction. The aim of this meta-analysis was to evaluate the benefits of omega-3 fatty acid supplementation in reducing proteinuria in diabetic patients by using all available evidence from the published literature. Isn’t ‘benefits’ pre-conclusive???

Methods: no issue

Results:

2nd line/ 1st paragraphs.. A total of 1277 potentially relevant citations were identified and screened. Seventy citations were evaluated in details, of which 10 trials (refs) with 344 participants…..

Issue- [ref] not stated.

Risk of bias section.. my comment—are the same studies ticking for high risk of bias as per overall risk? Randomization process? Deviation from intended intervention? Missing data?

Subgroup analyses..please quote patient numbers for each group. Also 2nd paragraph/ last line ..should be ‘are’ instead of ‘were’.

Discussion:

There is considerable room for improvement. I would like to detail some points which should be considered:

The major limitation of meta-analyses should be acknowledged. This is it cannot be used to derive explanations for mechanistic pathways or even derive a hypothesis. Further, the construct of this meta-Analyses depends on studies that are poor in design, small in patient numbers and lacking data on more robust biomarkers relating to inflammation [CRP], microalbuminemia status and blood urea levels. There is no point referencing animal studies. There are many studies with CKD population to provide enough inputs as to limitations in these n-3 fatty acid feeding trials.

In addition in reference to Table 1 which describes the selected studies:

There is heterogeneity in treatment based on dose and components of n-3 PUFAs [EPA, DHA or EPA+DHA..an either-and situation]. Further there is also heterogeneity of control treatment. Placebo [not stated] or oleic acid or linoleic acid. The control and treatments DO NOT match. This should be discussed.

Secondly, in these trials the background diets of the patients are not described. As we all know, once a patient is counseled a protein diet [1st line of management to treat proteinuria], then this affects urine protein status. The 2nd aspect is tighter blood glucose control which as its effect on proteinuria, eGFR and HbA1C.

The discussion should raise all the above points.

Conclusion: There is an issue with this statement- ‘omega-3 fatty acids could ameliorate proteinuria among type 2 DM patients who received omega-3 supplementation for at least 24 weeks without adverse effects on HbA1C and serum LDL-cholesterol.’

This conclusion cannot be supported from the evidence reported:

• Overall diabetic patients [NIDDM+IDDM] proteinuria- not significant; eGFR- not significant

• NIDDM- proteinuria- yes ; eGFR- not significant

• IDDM- proteinuria- not significant; eGFR- not significant

• In a meta-regression analysis, the change in proteinuria was not associated with change in GFR (- 0.01 (-0.09, 0.07); p-value = 0.69) and the change in proteinuria was not associated with combined dose of EPA and DHA (0.03 (-0.17, 0.24); p-value = 0.73).

Reviewer #3: Comments:

This manuscript aims to investigate the effects of omega-3 long- chain polyunsaturated fatty acids on proteinuria, eGFR and metabolic biomarkers in diabetic patients. This is a meta-analysis including 10 RCTs with 344 participants, and the authors report that Omega-3 supplementation for 24 weeks or longer could help alleviated proteinuria in patients with type 2 diabetes.

There are some questions should be addressed:

1. Introduction:

(1) Please provide the related references in the paragraph 2.

2. Methods:

(1) Data extraction and quality assessment: how about other serum lipids and glucose control biomarkers, such as the HDL, total cholesterol or fasting glucose?

(2) The results form fixed-effects models should also be presented.

3. Results:

(1) In the flow chart (Figure1), a total of 1277 articles are screened for retrieval, and 179 excluded. However,1089 included in the next stage (missing 9 articles), please check the number carefully.

(2) In table 1, mean age of patients ranged from 33 to 67.4 years old. The duration of follow up spanned from 6 weeks to 52 weeks. It is inconsistent with that in the results section, please check.

(3) Please provide the related tables and figures about the effect of omega-3 fatty acids on eGFR, serum lipids and glucose control.

(4) Why choose 24 weeks as a cut of duration of intervention in subgroup? Please explain. If possible, please provide the results using meta-regression analysis.

(5) Page 13, Paragraph 4: the results were not found in the table 4. Please provide.

(6) Please provide Figure 5.

(7) Each table or figure should be cited in the manuscript. Please check.

(8) Please improve the resolution and clarity of figures.

(9) The authors should provide the mean (SD) of the study outcomes for each treatment group in the figures or tables. It is inappropriate to present MD only.

4. Discussion:

(1) The first paragraph: It is inappropriate to present the result with “this is the first meta-analysis to…among diabetic patients in all aspects.”, because in 2009, Miller et al. conducted a similar meta-analysis.

(2) Please discuss the result that omega-3 fatty acids could help ameliorate serum triglyceride among type 1 DM who received omega-3 supplementation less than 24 weeks.

(3) If possible, to evaluate the optimal dosage of Omega-3 fatty acids for prevention of the study outcomes.

(4) Please further discuss the possible mechanism for effect of omega-3 supplementation on the different diabetes types.

(5) The authors first stated: “the observed effects of omega-3 fatty acids supplementation on proteinuria are not likely the result of blood pressure or renal perfusion effects only because we did not observe simultaneous changes in GFR. Hence, the effect of omega-3 fatty acids in ameliorating proteinuria may be beyond hemodynamic parameters”, while in the followed text, stated: “We found that omega-3 fatty acids did not provide any effects on GFR decline. This could be explained by low sample size as well as short period of follow-up.” Is it reasonable?

5. Please indicate the full names the first time you use the abbreviations in the text.

6. There are some spelling and grammatical errors that should be checked carefully and corrected throughout the manuscript.

[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 to be viewed.]

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 us at figures@plos.org. Please note that Supporting Information files do not need this step.

PONE-D-19-24289R1

The Effects of Omega-3 Fatty Acids on Diabetic Nephropathy: A Meta-analysis of Randomized Controlled Trials

PLOS ONE

Dear Dr. Chewcharat,

Thank you for submitting your revised 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.

We would appreciate receiving your revised manuscript by 20 January 2020. When you are 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.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter.

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

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). This letter should be uploaded as separate file and labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. This file should be uploaded as separate file and labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. This file should be uploaded as separate file and labeled 'Manuscript'.

Please note while forming your response, if your article is accepted, you may have the opportunity to make the peer review history publicly available. The record will include editor decision letters (with reviews) and your responses to reviewer comments. If eligible, we will contact you to opt in or out.

We look forward to receiving your revised manuscript.

Kind regards,

Tomislav Bulum

Academic Editor

PLOS ONE

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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 #2: All comments have been addressed

Reviewer #3: All comments have been addressed

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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 #2: Partly

Reviewer #3: Yes

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

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 #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 #2: Yes

Reviewer #3: Yes

**********

6. Review Comments to the Author

Reviewer #2: Dear Authors,

These details are required:

[1] Table 1 should provide eGFR data

[2] Check reference citation...eg. No.4 is it WE Mitch?? should be.

Reviewer #3: The authors have answered all the questions. However, they still should make a further discussion for the following question in the revised manuscript.

1. The reference 37 is not a meta-analysis, and did not support the related discussion. Please check the order of the references.

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Reviewer #2: Yes: Tilakavati Karupaiah

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 to be viewed.]

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The Effects of Omega-3 Fatty Acids on Diabetic Nephropathy: A Meta-analysis of Randomized Controlled Trials

PONE-D-19-24289R2

Dear Dr. Chewcharat,

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

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Tomislav Bulum

Academic Editor

PLOS ONE