Traumatic brain injury reprograms lipid droplet metabolism shaped by aging and diet in Drosophila brain

Stacey A. Rimkus; Barry Ganetzky; David A. Wassarman

doi:10.1371/journal.pone.0332333

Peer Review History

Original SubmissionMay 27, 2025
27 May 2025 Author Response 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. https://doi.org/10.1371/journal.pone.0332333.r001
18 Jul 2025 Decision Letter - Firas Kobeissy, Editor PONE-D-25-28751Traumatic brain injury reprograms lipid droplet metabolism shaped by aging and diet in Drosophila brainPLOS ONE Dear Dr. Wassarman, 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 Sep 01 2025 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. 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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 ******** 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: The manuscript by Rimkus et al. reports a detailed investigation of brain lipid metabolism dynamics in a drosophila model of TBI. Previous investigations from this group are consistent with results obtained from other groups that investigate the fruit fly to model TBI using different injury mechanisms. The application of lipidomics is novel to fly TBI models and complements the advanced imaging techniques. The data from all fly-TBI groups is, wherever comparisons are possible, also consistent with the comparatively low-resolution knowledge obtained from mammalian models. This manuscript is well written. The authors go to great lengths in describing their results in detail which may render the manuscript somewhat cumbersome in some sections. Comments Abstract line 34-37 how do we know that TBI selectively impairs LD production as opposed to LD degradation? Introduction: line 58-59. This is an important statement and this reviewer would have appreciated higher-level references to substantiate it. A similar concern applies to reference 11, published in Heliyon. These references to somewhat nebulous review articles are in contrast to the high-quality references in the subsequent paragraphs. What is the role of proteins in the formation and maintenance of LDs and could impaired protein (e.g. apolipoproteins) synthesis result in the observed changes? Therefore, the described changes in lipid metabolism described in this manuscript are a valuable addition to the fund of knowledge about mechanism of the secondary injury after TBI. Side note: ‘cargo€s is inconsistently spelled in the discussion. Line 365 ff: the references to clinical nutrition guidelines may be correct but the causality – use of saline instead of glucose-containing solutions is inaccurate. The reasoning was primarily avoidance of hypoosmotic solutions. It may be a bit too far stretched to cite antiquated clinical nutrition guidelines (which reflect decades old and frequently obsolete clinical insights) in a cutting-edge research paper. Supporting it with a ‘narrative review’ (the least rigorous form of review ref 63) only weakens the argument. I would suggest leaving ref 62 and removing the rest of the paragraph lines 371-374. Reviewer #2: The manuscript by Rimkus et al describes changes in lipids and lipid droplets that occur after TBI, suggesting that these could contribute to the susceptibility to develop neurodegeneration later. A major issue is that although they detect a significant increase in LD number 21d after the injury, these are not detectable after further aging. Furthermore, the area of LDs is not significantly different at any of the later timepoints. Concerning the lipids, although there are also differences at 21d, later timepoints have not been analyzed and so it is unknown whether changes in the lipid composition persist that could be the basis for the increased susceptibility. Another concern is that the statement that there is abnormal trafficking of microtubule is not supported by experimental data and it is difficult to judge the effects on microtubule in figure 4A and B; although at 14d the number of LDs should be about the same in uninjured and injured flies from their data, there are more LDs in the picture of the uninjured flies and it is not clear whether the pictures are from comparable regions of the brain. The authors point out that it is an important question whether the LDs are in glia or neurons which could be easily addressed by neuronal markers. ****** 6. 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Revision 1
25 Jul 2025 Author Response Reviewer #1: The manuscript by Rimkus et al. reports a detailed investigation of brain lipid metabolism dynamics in a drosophila model of TBI. Previous investigations from this group are consistent with results obtained from other groups that investigate the fruit fly to model TBI using different injury mechanisms. The application of lipidomics is novel to fly TBI models and complements the advanced imaging techniques. The data from all fly-TBI groups is, wherever comparisons are possible, also consistent with the comparatively low-resolution knowledge obtained from mammalian models. This manuscript is well written. The authors go to great lengths in describing their results in detail which may render the manuscript somewhat cumbersome in some sections. Comments Abstract line 34-37 how do we know that TBI selectively impairs LD production as opposed to LD degradation? Although our data do not definitively distinguish whether TBI affects LD production versus degradation at 21 days post-injury, our lipidomic results – along with findings from other studies (references 32, 47, 55, and 75) – support a role for impaired LD production. Therefore, we believe the interpretation that ‘These findings suggest that TBI selectively impairs age-dependent production of new LDs without affecting the growth of existing LDs’ is accurate, while still allowing for the possibility that degradation may also be involved. Introduction: line 58-59. This is an important statement and this reviewer would have appreciated higher-level references to substantiate it. A similar concern applies to reference 11, published in Heliyon. These references to somewhat nebulous review articles are in contrast to the high-quality references in the subsequent paragraphs. The reviewer makes a good point. To address this, for TBI, we cited primary research articles and review articles that highlight mitochondrial dysfunction, oxidative stress, and neuroinflammation as early contributors to TBI outcomes (references 9-18). For neurodegenerative disorders, we cited reviews discussing roles of these same mechanisms in Alzheimer’s, Parkinson’s, and Huntington’s diseases (references 19-27). What is the role of proteins in the formation and maintenance of LDs and could impaired protein (e.g. apolipoproteins) synthesis result in the observed changes? Proteins, including apolipoproteins, are critical for formation and maintenance of LDs and contribute to TBI-induced changes. As noted in lines 116-121, our GWAS data implicate several LD-related proteins in early mortality after TBI; however, the current data are insufficient to propose specific protein-level mechanisms. Therefore, the described changes in lipid metabolism described in this manuscript are a valuable addition to the fund of knowledge about mechanism of the secondary injury after TBI. Side note: ‘cargo€s is inconsistently spelled in the discussion. Cargos was changed to cargoes on page 14. Line 365 ff: the references to clinical nutrition guidelines may be correct but the causality – use of saline instead of glucose-containing solutions is inaccurate. The reasoning was primarily avoidance of hypoosmotic solutions. It may be a bit too far stretched to cite antiquated clinical nutrition guidelines (which reflect decades old and frequently obsolete clinical insights) in a cutting-edge research paper. Supporting it with a ‘narrative review’ (the least rigorous form of review ref 63) only weakens the argument. I would suggest leaving ref 62 and removing the rest of the paragraph lines 371-374. We appreciate the insights of the reviewer and have followed their suggestion of deleting lines 371-374 and the accompanying citations. Reviewer #2: The manuscript by Rimkus et al describes changes in lipids and lipid droplets that occur after TBI, suggesting that these could contribute to the susceptibility to develop neurodegeneration later. A major issue is that although they detect a significant increase in LD number 21d after the injury, these are not detectable after further aging. Furthermore, the area of LDs is not significantly different at any of the later timepoints. At 21 days, LD number increased in uninjured but not injured flies. As noted in lines 381-397, this may reflect other phenotypes that emerge around this time in uninjured flies (references 32, 47, 55, and 75). A significant difference in LD area was not only observed at 21 days but also 35 days (Figure 3C). Concerning the lipids, although there are also differences at 21d, later timepoints have not been analyzed and so it is unknown whether changes in the lipid composition persist that could be the basis for the increased susceptibility. We agree that additional time points would have helped determined whether changes in lipid composition persist. However, due to the high cost of lipidomic analysis, we were limited in the number of time points that could be included. Another concern is that the statement that there is abnormal trafficking of microtubule is not supported by experimental data and it is difficult to judge the effects on microtubule in figure 4A and B; although at 14d the number of LDs should be about the same in uninjured and injured flies from their data, there are more LDs in the picture of the uninjured flies and it is not clear whether the pictures are from comparable regions of the brain. We agree that the images in Figures 4A and B do not clearly support the text due to differences in microtubule orientation. To address this, we replaced Figure 4B with one that matches the orientation of Figure 4A. The authors point out that it is an important question whether the LDs are in glia or neurons which could be easily addressed by neuronal markers. It is possible to determine whether LDs are located in glia or neurons by labeling neuronal or glial cell membranes and performing 3D reconstruction. We plan to pursue this in future studies, but it is beyond the scope of the current manuscript. https://doi.org/10.1371/journal.pone.0332333.r003
29 Aug 2025 Decision Letter - Firas Kobeissy, Editor Traumatic brain injury reprograms lipid droplet metabolism shaped by aging and diet in Drosophila brain PONE-D-25-28751R1 Dear Dr. Wassarman, 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 will be generated when your article is formally accepted. Please note, if your institution has a publishing partnership with PLOS and your article meets the relevant criteria, all or part of your publication costs will be covered. 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Reviewer #1: Yes 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 #1: Yes 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 #1: Yes 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 #1: I still consider the Heliyon reference as 'weak' and think that clinical references do not always strengthen lab bench work in IMOs. Reviewer #2: The authors have added another figure to address my concerns that the previous picture did not clearly show what they described. The other critiques have also been addressed sufficiently to justify publication. ****** 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 ******** https://doi.org/10.1371/journal.pone.0332333.r004
Formally Accepted
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