Erythrocyte sodium buffering capacity status correlates with self-reported salt intake in a population from Livingstone, Zambia

Sepiso K. Masenga; Leta Pilic; Malani Malumani; Benson M. Hamooya

doi:10.1371/journal.pone.0264650

Peer Review History

Original SubmissionSeptember 7, 2021
22 Oct 2021 Decision Letter - Jaap A. Joles, Editor Transfer Alert This paper was transferred from another journal. As a result, its full editorial history (including decision letters, peer reviews and author responses) may not be present. PONE-D-21-29014Erythrocyte sodium buffering capacity status correlates with self-reported salt intake in a population from Livingstone, ZambiaPLOS ONE Dear Dr. Masenga, 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. Two expert reviewers have carefully studied your manuscript. Fortunately, both find the topic of interest. However, a number of important concerns are raised that must all be addressed.A more accurate measure of salt consumption would considerably increase the relevance of your findings. Please submit your revised manuscript by Dec 06 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'. 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Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols. We look forward to receiving your revised manuscript. Kind regards, Jaap A. Joles, DVM, PhD 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. Please include additional information regarding the questionnaire used in the study and ensure that you have provided sufficient details that others could replicate the analyses. 3. 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Note that it is not acceptable for the authors to be the sole named individuals responsible for ensuring data access. We will update your Data Availability statement to reflect the information you provide in your cover letter. [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: Partly Reviewer #2: Yes ******** 2. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: Yes Reviewer #2: 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: No ****** 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: No Reviewer #2: No ****** 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: Masenga and colleagues want to define what factors are related to sodium buffering capacity in a population living in Zambia. To establish sodium buffering capacity they have used the erythrocyte sodium sensitivity test as developed by Oberleithner a couple of year ago. The idea that sodium can be stored in the endothelial glycocalyx and the glycocalyx of the erythrocyte may have great impact on the current concepts of sodium homeostasis and pathophysiology of salt sensitivity. As such, this paper addresses an important topic, but I have some important concerns. Major comments - Abstract o In the introduction the authors state that high sodium consumption leads to reduced sodium buffering capacity. I don’t think this statement is completely true. Data from animals and intervention studies indicate that high sodium effects can be neutralized by increasing buffering capacity, for instance, in the skin (Machnik A, Nature). Glycocalyx dimension might change after an IV sodium load, but necessarily after high sodium intake (Rorije NM, Anesthesiology) o Results. Line 39. The word ‘about’ should be removed. Please report exact numbers in the result section. o Results. Line 41. The expression ‘erythrocyte sodium sensitive’ is an unclear expression and seems more an interpretation of the results than a true finding. - Methods section o The description of the included patients is very unclear. It seems a pretty random selection of health care workers and patients visiting the hospital on a regular base. o The way sodium consumption has been estimated is not clearly described. For instance, what does an adapted version of the food frequency questionnaire exactly mean? o The ESS test that has been used for estimating sodium buffering capacity has in my view never been validated. Sodium buffering capacity can be demonstrated after tissue ashing methods or by MRI techniques. Unfortunately, no data with regard to these accepted methods are available to my understanding. - Results o Line 124. Please remove 'about'. o Line 125 reads a bit difficult. o Table 2 shows that red blood cell indices (RBC, Hb, and Ht) differ for each ESS category. Given the lack of validation of the ESS test, I wonder whether ESS is not merely another red blood cell marker than a reflection sodium buffering in glycocalyx. It seems that the results of the multiple linear analysis do not take away this concern. o Figure 1 A and B show the regression between categorical variables. This is not very informative. Reviewer #2: Masenga performed a very interesting study showing a correlation between the erythrocyte glycocalyx, ABI and self-reported salt consumption in a healthy cohort. This is of great importance and can be useful as low-cost, fast and simple tool for the prevention of hypertension and cardiovascular events which are often triggered by high salt consumption, especially in salt-sensitive individuals. However, I have some concerns: 1. A clear description of the methods is missing and should be provided 2. Also, a clear structure of the manuscript is missing (e.g. figure legends appear in the discussion section) 3. A self-reported salt consumption is a limitation. At least random sampling of 24 hour urine should be done 4. At least an estimation of the salt consumption should be given (e.g. 1 tea spoon) 5. What is the authors explanation of the fact that unemployed had the highest proportion of high ESS compared with the employed? ****** 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: Yes: Liffert Vogt Reviewer #2: Yes:** Kristina Kusche-Vihrog [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. https://doi.org/10.1371/journal.pone.0264650.r001
Revision 1
7 Jan 2022 Author Response 1st December, 2021 To the Editor in Chief Dear Editor, Ref: Re-submission of revised research article The above matter refers. We thank the reviewers for their constructive and positive review of our manuscript. We revised the manuscript in accordance with the various review comments (indicated in bold) and hope that it is now acceptable for publication. I am pleased to resubmit a revised version of our manuscript. Details of the changes are shown in the “track changes” version of the manuscript. Responses to the reviewers Reviewer #1: Masenga and colleagues want to define what factors are related to sodium buffering capacity in a population living in Zambia. To establish sodium buffering capacity, they have used the erythrocyte sodium sensitivity test as developed by Oberleithner a couple of year ago. The idea that sodium can be stored in the endothelial glycocalyx and the glycocalyx of the erythrocyte may have great impact on the current concepts of sodium homeostasis and pathophysiology of salt sensitivity. As such, this paper addresses an important topic, but I have some important concerns. Major comments - Abstract In the introduction the authors state that high sodium consumption leads to reduced sodium buffering capacity. I don’t think this statement is completely true. Data from animals and intervention studies indicate that high sodium effects can be neutralized by increasing buffering capacity, for instance, in the skin (Machnik A, Nature). Glycocalyx dimension might change after an IV sodium load, but necessarily after high sodium intake (Rorije NM, Anesthesiology) Response: We agree with the reviewer that this statement is misleading. We have corrected it to imply only that there is a possible relationship between salt intake and sodium buffering capacity and CVD which is supported by literature. We appreciate this comment. Results. Line 39. The word ‘about’ should be removed. Please report exact numbers in the result section. Response: We have removed as suggested. Thank you Results. Line 41. The expression ‘erythrocyte sodium sensitive’ is an unclear expression and seems more an interpretation of the results than a true finding. Response: Thank you for the suggestion. We have modified appropriately and reported only the finding. Methods section The description of the included patients is very unclear. It seems a pretty random selection of health care workers and patients visiting the hospital on a regular base. Response: We agree very much with the reviewer that the population under study was not described clearly. We have clarified this by adding some descriptive details. The population consisted of health care workers attending to routine medical checkups. We excluded any participants who were ill at the time of study. The way sodium consumption has been estimated is not clearly described. For instance, what does an adapted version of the food frequency questionnaire exactly mean? Response: We have now elaborated in detail how salt consumption was assessed in the structured questionnaire. In addition, as requested by another reviewer, we have additionally sampled a quarter of the total participants and estimated their dietary salt intake using 24-hour urine samples to validate perceived salt intake. We found a positive correlation and our data is further supported by prior research. The ESS test that has been used for estimating sodium buffering capacity has in my view never been validated. Sodium buffering capacity can be demonstrated after tissue ashing methods or by MRI techniques. Unfortunately, no data with regard to these accepted methods are available to my understanding. Response: We agree that ESS is not validated to estimate sodium buffering capacity in our population and we have therefore been very cautious on our interpretation of data. We have added this limitation in the limitation section of the discussion. Results Line 124. Please remove 'about'. Response: We have removed ‘about’ as suggested. Thank you. Line 125 reads a bit difficult. Response: We have re-written this sentence to read clearly. Thank you. Table 2 shows that red blood cell indices (RBC, Hb, and Ht) differ for each ESS category. Given the lack of validation of the ESS test, I wonder whether ESS is not merely another red blood cell marker than a reflection sodium buffering in glycocalyx. It seems that the results of the multiple linear analysis do not take away this concern. Response: Much appreciated for this suggestion. Our understanding of ESS test is that since the buffering capacity of red blood cells mirror that of the glycocalyx, a reduction in RBC count would mean a reduction in the buffering of sodium. This is expected as shown in the linear regression results and table 2. But truly, this does not take away the possibility that ESS may just be another red blood cell marker, a concern raised by the reviewer. However, we have now provided supplementary data (S2 table) that was based on additional analysis where we have included estimated salt intake in the multiple linear analysis and this takes away the concern of the red cell indices; they did not remain significantly associated with ESS when actual estimated salt intake was included in the model. Thank you for this suggestion. Figure 1 A and B show the regression between categorical variables. This is not very informative. Response: Thank you for the suggestion. We have removed the two figures on gender nd employment Reviewer #2: Masenga performed a very interesting study showing a correlation between the erythrocyte glycocalyx, ABI and self-reported salt consumption in a healthy cohort. This is of great importance and can be useful as low-cost, fast and simple tool for the prevention of hypertension and cardiovascular events which are often triggered by high salt consumption, especially in salt-sensitive individuals. However, I have some concerns: 1. A clear description of the methods is missing and should be provided Response: We have expanded the methods section to accurately elaborate the methods to ensure that they are reproducible. We appreciate the concern and fill that the methods section is now clearly described. We are happy to receive further specific advice if necessary. 2. Also, a clear structure of the manuscript is missing (e.g. figure legends appear in the discussion section) Response: This is very true for most journals. However, we noticed that journal requirement for plos one do not prohibit this. We have adhered to the specific journal requirements. It appears that it is a journal requirement to add figure legends immediately after the figure caption and title. We thank you for this concern. 3. A self-reported salt consumption is a limitation. At least random sampling of 24-hour urine should be done Response: We have managed to perform random sampling of 24-hour urine to estimate actual salt intake and have included this in our results. See Fig 2 also. 4. At least an estimation of the salt consumption should be given (e.g. 1 tea spoon) Response: We have now provided information on salt consumption in g/day based on 24-hour urine samples. This suggestion is appreciated. 5. What is the authors explanation of the fact that unemployed had the highest proportion of high ESS compared with the employed? Response: This finding was interesting and would be important to explain further as suggested here. However, It was beyond the scope of our study to explain this finding that the unemployed had the highest proportion of high ESS compared with the employed. Moreover, since this finding was not significant on multilinear regression. We thought it not necessary to discuss further as this would divert focus on the main findings. We hope to look at this more in detail in future studies focused on sociodemographic factors. We sincerely thank you again for the suggestions which have remarkably improved our manuscript. We look forward to hearing from you at your earliest convenience. Yours sincerely, Dr. Sepiso K. Masenga Attachments Attachment Submitted filename: Response to reviewers.pdf https://doi.org/10.1371/journal.pone.0264650.r002
15 Feb 2022 Decision Letter - Jaap A. Joles, Editor Erythrocyte sodium buffering capacity status correlates with self-reported salt intake in a population from Livingstone, Zambia PONE-D-21-29014R1 Dear Dr. Masenga, 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, Jaap A. Joles, DVM, PhD Academic Editor PLOS ONE Additional Editor Comments (optional): The reviewers comments have been adequately addressed. Unfortunately Reviewer #1 did not respond to my invitation but I am satisfied with your response. 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 ******** 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: Yes ****** 3. Has the statistical analysis been performed appropriately and rigorously? Reviewer #2: 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 ****** 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 ****** 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 #2: After expanding the methods section and the addition of information about the cohort and salt consumption, my concerns are addressed. ****** 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 #2: Yes:** Kristina Kusche-Vihrog https://doi.org/10.1371/journal.pone.0264650.r003
Formally Accepted
21 Feb 2022 Acceptance Letter - Jaap A. Joles, Editor PONE-D-21-29014R1 Erythrocyte sodium buffering capacity status correlates with self-reported salt intake in a population from Livingstone, Zambia Dear Dr. Masenga: I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department. If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. 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. If we can help with anything else, please email us at plosone@plos.org. Thank you for submitting your work to PLOS ONE and supporting open access. Kind regards, PLOS ONE Editorial Office Staff on behalf of Dr. Jaap A. Joles Academic Editor PLOS ONE https://doi.org/10.1371/journal.pone.0264650.r004

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