The effect of hydration status on plasma FGF21 concentrations in humans: A subanalysis of a randomised crossover trial

Harriet A. Carroll; Yung-Chih Chen; Iain Templeman; Lewis J. James; James A. Betts; William V. Trim

doi:10.1371/journal.pone.0235557

Peer Review History

Original SubmissionMarch 9, 2020
7 Apr 2020 Decision Letter - Jo Edward Lewis, 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-20-06810 The effect of hydration status on plasma FGF21 concentrations in humans PLOS ONE Dear Dr Carroll, 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. We would appreciate receiving your revised manuscript by 5th May 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, Jo Edward Lewis, Ph.D Academic Editor PLOS ONE Journal Requirements: When submitting your revision, we need you to address these additional requirements. 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 1. In your Methods section, please provide additional information about the participant recruitment method and the demographic details of your participants. Please ensure you have provided sufficient details to replicate the analyses such as: a) the recruitment date range (month and year), b) a description of any inclusion/exclusion criteria that were applied to participant recruitment, c) a table of relevant demographic details, d) a statement as to whether your sample can be considered representative of a larger population, e) a description of how participants were recruited, and f) descriptions of where participants were recruited and where the research took place. 2. Please provide additional details regarding participant consent. In the ethics statement in the Methods and online submission information, please specify whether trial participants consented to the use of samples in additional analyses (not included by the original trial). If not, please specify whether you obtained separate ethics approval for this analysis. 3. Thank you for including the following funding information within the acknowledgements section; "This work was supported by the Economic and Social Research Council (grant no.: ES/J50015X/1) and the European Hydration Institute Graduate Research Grant. " We note that you have provided funding information that is not currently declared in your Funding Statement. However, funding information should not appear in the Acknowledgments section or other areas of your manuscript. We will only publish funding information present in the Funding Statement section of the online submission form. Please remove any funding-related text from the manuscript and let us know how you would like to update your Funding Statement. Currently, your Funding Statement reads as follows: "HAC is funded by the Economic and Social Research Council (grant no.: ES/J50015X/1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript." Additional Editor Comments (if provided): 7/04/2020 Dear Dr Carroll, PONE-D-20-06810 The effect of hydration status on plasma FGF21 concentrations in humans Many thanks for sending us your manuscript. It has now been reviewed by two experts in the field and by one of our Editors, and I am pleased to tell you that we found it potentially suitable for publication. You will see however that the referees have raised a number of points that still require your consideration. I would therefore like to offer you the opportunity to revise this manuscript taking these comments into account. You should explain the changes that you have made in response to the referees’ comments in a covering letter. Please also make the changes suggested by our editorial staff to bring your manuscript into line with house style – this will speed subsequent processing of your paper if it is accepted. Please submit an electronic version of your revised paper within 28 days of receipt of this letter. If new experiments have been requested which will be impossible to complete within this time, we will consider an appeal to extend this deadline. Please contact the Editorial Office if you have any queries. As I am sure you will appreciate, I am unable as yet to make any final commitment regarding acceptance of this manuscript. Yours sincerely, Dr Jo Edward Lewis [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 ******** 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: 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 ****** 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: An important study with broadly interesting results regarding FGF21 involvement in fluid balance in humans. A few minor points. On line 75/76 authors state that PF-05231023 reduces blood pressure, but the manuscript they cite shows the reverse. On line 78 the Song reference is stated to have used rats, but the species used in this study were mice. Regarding the hypothesis in the introduction, wouldn't it be more logical to expect that heat induced water loss from sweat would suppress secretion of a diuretic factor from the liver? Major point: Would correcting FGF21 levels for plasma volume depletion affect these results? (i.e. to albumin or whatever is standard). Reviewer #2: This work by Carroll and colleagues explores the effect of hydration on circulating levels of the endocrine factor FGF21 in humans. Previous work in rodents has suggested that FGF21 could regulate thirst and the authors examined whether plasma FGF21 levels were physiologically altered by hydration status. These data are important for the field and warrant publication, but a few minor issues need to be addressed beforehand. 1) It would be worthwhile to include in the introduction and discussion that FGF21 has been shown to increase fluid intake primarily under potentially hypermetabolic conditions. It has been proposed that this increase in fluid intake in response to FGF21 is actually due to increases in food intake (i.e., prandial thirst) (BonDurant and Potthoff; PMID: 29727594). 2) FGF21 does not increase fluid intake under conditions of high sucrose (von Holstein-Rathlou et al.; PMID: 26724858). This citation was also omitted on the sweet taste reference. 3) A potential issue is how FGF21 levels were measured. The authors need to provide more information about this electrochemiluminescence assay. What part of FGF21 does this assay measure. As the authors may know, FGF21 is cleaved and inactivated on the C-terminus. Thus, did the authors measure total or “active” FGF21? These issues should also be addressed in the discussion as potential limitation of the results. ****** 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: Matthew Gillum Reviewer #2: 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.] 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. https://doi.org/10.1371/journal.pone.0235557.r001
Revision 1
16 May 2020 Author Response [Editor comment] 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 [Author response] We have checked the style requirements and believe we have met the criteria. [Editor comment] 1. In your Methods section, please provide additional information about the participant recruitment method and the demographic details of your participants. Please ensure you have provided sufficient details to replicate the analyses such as: a) the recruitment date range (month and year), b) a description of any inclusion/exclusion criteria that were applied to participant recruitment, c) a table of relevant demographic details, d) a statement as to whether your sample can be considered representative of a larger population, e) a description of how participants were recruited, and f) descriptions of where participants were recruited and where the research took place. [Author response] We have added subsections to our methods, the first of which is “Participants”. Within this section we have included the information requested: “Participants Participants were recruited using posters at the University of Bath (South West England), which is where the research was conducted, between June 2016 and January 2017. The inclusion criteria required participants to be healthy and not taking prescribed medication or supplements, with the exception of hormonal contraceptives. Therefore, our exclusion criteria were: age < 18 y or ≥ 60 y, self-reported metabolic disease (no body mass restrictions, except self-reported weight loss > 5 kg in previous 6 mo), drug dependence, and pregnancy/breastfeeding. We recruited sixteen healthy adults who successfully participated in the study after giving fully informed consent (Table 1). Participants were not offered any incentive to participate, beyond their individualised feedback; considering this, the affluence of the city of Bath, and our inclusion criteria focused on healthy adults, our sample is representative of healthy middle-class younger adults (both men and women), interested in their health.” (lines 124-129) Additionally, we have included a table with key participant characteristics: age, sex weight, BMI. [Editor comment] 2. Please provide additional details regarding participant consent. In the ethics statement in the Methods and online submission information, please specify whether trial participants consented to the use of samples in additional analyses (not included by the original trial). If not, please specify whether you obtained separate ethics approval for this analysis. [Author response] We obtained fully informed consent to conduct all the necessary procedures on participants, such as cannulation and taking a pre-specified amount of blood. Participants consented for their samples to be used for relevant analyses, but we had not specified exactly what these analyses would be. Therefore, FGF21 analyses were consensually covered and did not require further approval or consent. As FGF21 was unplanned, it was not included on our trial registration unlike the main analytes, such as glucose and insulin. We have added the following to the manuscript: “All participants gave fully informed consent to undergo the protocol and for their samples and data to be used as appropriate for the project.” (lines 121-122) [Editor comment] 3. Thank you for including the following funding information within the acknowledgements section; "This work was supported by the Economic and Social Research Council (grant no.: ES/J50015X/1) and the European Hydration Institute Graduate Research Grant. " We note that you have provided funding information that is not currently declared in your Funding Statement. However, funding information should not appear in the Acknowledgments section or other areas of your manuscript. We will only publish funding information present in the Funding Statement section of the online submission form. Please remove any funding-related text from the manuscript and let us know how you would like to update your Funding Statement. Currently, your Funding Statement reads as follows: "HAC is funded by the Economic and Social Research Council (grant no.: ES/J50015X/1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript." [Author response] We have removed this from the manuscript and would appreciate it being added to our funding statement. Apologies for the mix-up. Reviewers' comments [Reviewer comment] Reviewer #1: An important study with broadly interesting results regarding FGF21 involvement in fluid balance in humans. A few minor points. On line 75/76 authors state that PF-05231023 reduces blood pressure, but the manuscript they cite shows the reverse. On line 78 the Song reference is stated to have used rats, but the species used in this study were mice. [Author response] Thank you for highlighting these errors, we have amended as appropriate (changes in red): “though recent work has shown PF-05231023 infusion in humans with obesity and hypertriglyceridaemia to reduce blood pressure, corroborating findings in rodents.” (lines 94-95) “Whilst Song et al.3 found FGF21 to be unaffected after water deprivation in smice…” (line 98) [Reviewer comment] Regarding the hypothesis in the introduction, wouldn't it be more logical to expect that heat induced water loss from sweat would suppress secretion of a diuretic factor from the liver? [Author response] Thank you for this insight. Since there was no causal human work to go from, our hypothesis was built on reverse causality from the findings of previous research. However, your hypothesis fits the causal direction of our study design better and makes logical sense. We have therefore amended our hypothesis and discussion as follows (changes in red): “Due to the findings of previous research showing FGF21 appears to induce dehydration (e.g. increased urination), we hypothesised that hypohydration (HYPO) would lead to a decrease in fasted plasma FGF21 concentrations compared to when participants were rehydrated (RE), due to water losses suppressing secretory diuretic hormones.” (lines 110-112) “Contrary to our hypothesis, hypohydration did not decrease fasted plasma FGF21 concentrations.” (line 219) Major point: [Reviewer comment] Would correcting FGF21 levels for plasma volume depletion affect these results? (i.e. to albumin or whatever is standard). [Author response] We agree that correcting for plasma volume would be interesting, and as such we did measure plasma volume using haematocrit and haemoglobin. However, we made a methodological error in standardising posture properly during the study, which meant our plasma volume data were not reliable. We outlined this in our original manuscript of the main study findings (doi: 10.1152/japplphysiol.00771.2018) as well as providing the (unreliable) data with an explanatory note in our published data for others to scrutinise (https://researchdata.bath.ac.uk/id/eprint/547). Whilst mechanistically interesting to correct for plasma volume, uncorrected data still provide valid results as most studies do not measure plasma volume. Nonetheless, we do appreciate these would have been valuable data to have had. [Reviewer comment] Reviewer #2: This work by Carroll and colleagues explores the effect of hydration on circulating levels of the endocrine factor FGF21 in humans. Previous work in rodents has suggested that FGF21 could regulate thirst and the authors examined whether plasma FGF21 levels were physiologically altered by hydration status. These data are important for the field and warrant publication, but a few minor issues need to be addressed beforehand. [Author response] We appreciate your overall positive review and hope we have addressed the issues you raised below. [Reviewer comment] 1) It would be worthwhile to include in the introduction and discussion that FGF21 has been shown to increase fluid intake primarily under potentially hypermetabolic conditions. It has been proposed that this increase in fluid intake in response to FGF21 is actually due to increases in food intake (i.e., prandial thirst) (BonDurant and Potthoff; PMID: 29727594). [Author response] Thank you for this article and idea. Since understanding the interaction between energy expenditure, food, and thirst was not the aim of the study, we have acknowledged this theory in our discussion only, as follows: “In relation to metabolic states, FGF21 may respond specifically to hypermetabolic conditions whereby total energy expenditure has increase resulting in an increase in energy intake. This in turn drives thirst and therefore drinking behaviour [25]. Thus an increase in thirst and drinking behaviours may be a result of elevations in FGF21 (which increases energy expenditure in mice [26]). Our data provide support for this pathway as hydration status itself did not alter thirst or biomarkers of hydration status.” (lines 249-254) [Reviewer comment] 2) FGF21 does not increase fluid intake under conditions of high sucrose (von Holstein-Rathlou et al.; PMID: 26724858). This citation was also omitted on the sweet taste reference. [Author response] Apologies for not including this; we have added the citation to the introduction regarding sweet taste (line 64). However, we are unsure of the link to our manuscript and fluid intake under high sucrose conditions. [Reviewer comment] 3) A potential issue is how FGF21 levels were measured. The authors need to provide more information about this electrochemiluminescence assay. What part of FGF21 does this assay measure. As the authors may know, FGF21 is cleaved and inactivated on the C-terminus. Thus, did the authors measure total or “active” FGF21? These issues should also be addressed in the discussion as potential limitation of the results. [Author response] Thank you for raising this relevant issue of which form (total or active) of FGF21 was targeted by the assay used in this study. The FGF21 assay performed here was a commercially available electrochemiluminescence assay produced and supplied by Mesoscale Diagnostics (MSD). We contacted MSD in order to answer your query. MSD informed us that it has, unfortunately, not been tested in-house by MSD as to which form of FGF21 is targeted by this human assay. However, the calibrator used in this assay is full length human FGF21 expressed in E.coli with a predicted molecular mass of 20 kDa. Thus it is likely, though not guaranteed, that we measured total FGF21. We have added in the manuscript the following to account for the ambiguity: “Additionally, the kit we used to analyse FGF21 does not specify whether total or active FGF21 is measured; considering its calibration using full-length FGF21 with a predicted molecular mass of 20 kDa, it is most likely we measured active FGF21, which has been shown to the primary circulating form of FGF21 [27].” (lines 272-275) 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. [Author response] We have done this and believe our figure meets PLoS ONE specifications. Attachments Attachment Submitted filename: Response to reviewers.docx https://doi.org/10.1371/journal.pone.0235557.r002
10 Jun 2020 Decision Letter - Jo Edward Lewis, Editor PONE-D-20-06810R1 The effect of hydration status on plasma FGF21 concentrations in humans PLOS ONE Dear Dr. Carroll, 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 submit your revised manuscript by Jul 25 2020 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, Jo Edward Lewis, Ph.D Academic Editor PLOS ONE [Note: HTML markup is below. Please do not edit.] 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 #3: (No Response) ******** 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 #3: Yes ****** 3. Has the statistical analysis been performed appropriately and rigorously? 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 #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 #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 #3: Interesting sub analyis, although with some limitations The present is a crossover RCT: this should be added in the title,. I would write; a sub analysis of a crossover RCT Methods: tables should be put at end and not in the text Methods: sample size calculation was not performed for this rct: this should be put in limitation. Moreover this sub analysis was not prespecificed and also this should be added in limitation section ****** 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 #3: Yes: Fabrizio D'Ascenzo [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.0235557.r003
Revision 2
13 Jun 2020 Author Response [Reviewer comment] Interesting sub analyis, although with some limitations. The present is a crossover RCT: this should be added in the title,. I would write; a sub analysis of a crossover RCT [Author response] Thank you for this helpful comment. We have changed the title to “The effect of hydration status on plasma FGF21 concentrations in humans: A subanalysis of a randomised crossover trial”. [Reviewer comment] Methods: tables should be put at end and not in the text [Author response] We followed PLoS author guidelines and inserted tables immediately after the paragraph they were first cited. [Reviewer comment] Methods: sample size calculation was not performed for this rct: this should be put in limitation. [Author response] Lines 264-270 discussed that the study was powered for glycaemia not FGF21. We have added the following to this paragraph to emphasise the point: “It may be that there is a small but meaningful response, which we may not have been able to detect due to lack of statistical power for FGF21 as the outcome” (line 266) [Reviewer comment] Moreover this sub analysis was not prespecificed and also this should be added in limitation section [Author response] We hope it was clear this was not a pre-specified outcome in our introduction, but have reiterated this point in our discussion: “Nonetheless, future work should investigate the postprandial FGF21 response according to hydration status; this is particularly important considering our present analysis was decided post hoc and therefore not pre-specified in our research plan or trial registration.” (lines 256-258) Additional edit: Since resubmitting the manuscript, the first author has changed institutional affiliation, and this has been amended on the title page. Attachments Attachment Submitted filename: Response to reviewers_June.docx https://doi.org/10.1371/journal.pone.0235557.r004
18 Jun 2020 Decision Letter - Jo Edward Lewis, Editor The effect of hydration status on plasma FGF21 concentrations in humans: A subanalysis of a randomised crossover trial PONE-D-20-06810R2 Dear Dr. Carroll, 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, Jo Edward Lewis, Ph.D Academic Editor PLOS ONE Additional Editor Comments (optional): Reviewers' comments: https://doi.org/10.1371/journal.pone.0235557.r005
Formally Accepted
23 Jul 2020 Acceptance Letter - Jo Edward Lewis, Editor PONE-D-20-06810R2 The effect of hydration status on plasma FGF21 concentrations in humans: A subanalysis of a randomised crossover trial Dear Dr. Carroll: 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. Jo Edward Lewis Academic Editor PLOS ONE https://doi.org/10.1371/journal.pone.0235557.r006

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