PONE-D-25-06878Brain glucose and ketone metabolism in first-episode psychosis: neuroimaging and brain metabolism before and after antipsychotic treatment: the protocol for the CAST-ATP studyPLOS ONE

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Financial support for this article and the project it describes was received in the form of a philanthropic grant donated by the “Baszucki Brain Research Fund”, USA, to the Université of Sherbrooke Foundation. SCC holds the Endowed Clinical Ketotherapeutics Chair at the Université of Sherbrooke. MH holds the CAMH and UofT Meighen Family Research Chair in Psychosis Prevention. SMA is supported in part by the Discovery Fund, CAMH and the Academic Scholars Awrard from the Department of Psychiatry, University of Toronto.

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SCC has received research funding and test materials from Nestlé Health Science. He consults for Nestlé Health Science and Cerecin. OKF reports speaker fees from Lundbeck Pharma A/S, consultant work for WCG International, and serving on an advisory board for Boehringer-Ingelheim. BE is part of the Advisory Board of Boehringer Ingelheim, Lundbeck Pharma A/S; and has received lecture fees from Boehringer Ingelheim, Otsuka Pharma Scandinavia AB, and Lundbeck Pharma A/S. SMA has received honoraria from HLS therapeutics and Boehringer Ingelheim. MH has received consultant fees from Alkermes and MERCK. The other authors declare that the research will be conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Does the manuscript provide a valid rationale for the proposed study, with clearly identified and justified research questions?

The research question outlined is expected to address a valid academic problem or topic and contribute to the base of knowledge in the field.

Reviewer #1: Yes

Reviewer #2: Yes

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2. Is the protocol technically sound and planned in a manner that will lead to a meaningful outcome and allow testing the stated hypotheses?

The manuscript should describe the methods in sufficient detail to prevent undisclosed flexibility in the experimental procedure or analysis pipeline, including sufficient outcome-neutral conditions (e.g. necessary controls, absence of floor or ceiling effects) to test the proposed hypotheses and a statistical power analysis where applicable. As there may be aspects of the methodology and analysis which can only be refined once the work is undertaken, authors should outline potential assumptions and explicitly describe what aspects of the proposed analyses, if any, are exploratory.

Reviewer #1: Yes

Reviewer #2: Yes

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3. Is the methodology feasible and described in sufficient detail to allow the work to be replicable?

Descriptions of methods and materials in the protocol should be reported in sufficient detail for another researcher to reproduce all experiments and analyses. The protocol should describe the appropriate controls, sample size calculations, and replication needed to ensure that the data are robust and reproducible.

Reviewer #1: Yes

Reviewer #2: Yes

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4. Have the authors described where all data underlying the findings will be made available when the study is complete?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception, at the time of publication. 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

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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

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6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above and, if applicable, provide comments about issues authors must address before this protocol can be accepted for publication. You may also include additional comments for the author, including concerns about research or publication ethics.

You may also provide optional suggestions and comments to authors that they might find helpful in planning their study.

(Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The objectives (primary, secondary and exploratory) are outlined appropriately and the document is well written. There are a number of clarifications needed as noted below.

As per the investigators, this study is observational and will thus have no direct influence on clinical practice. It is expected that a total of n=24 participants will be needed to complete the study on the two sites combined. The investigators note this should provide ample power to define the metabolic perturbations in the brain. How is power being used here?

There are many analyses being proposed for so few patients. One needs to exercise caution on how to interpret the p-values as this is noted as a proof of concept study as per the investigators. This should be noted as a limitation.

The sample size rationale appears reasonable as there is no background data to establish it with any power. However, could some clinically meaningful effect sizes for differences be used to establish the sample size? In any case, be specific. If you need 24 subjects from the two sites is that 12 per group (AP vs. controls)? Also what about dropouts? How will they be handled in this short period if that should be an issue? This should be added as a possible limitation if such is the case.

The statistical analysis approach for this limited sample is reasonable. However, if the investigators are proposing a non parametric approach such as the Wilcoxon signed rank for paired data then one may wish to consider the IQR (interquartile range) and not only the mean and standard deviation for summary results if some data satisfies the normality assumption. There are a number of outcome measures. Specific analyses should be matched with those being proposed. The timeline in Table 1 was very helpful.

Reviewer #2: The protocol’s hypothesis that antipsychotic treatment may worsen brain glucose metabolism, while leaving ketone metabolism intact, is particularly relevant to advancing therapeutic strategies. Another strength is that this protocol is novel in that direct neuroimaging measurement of both glucose and ketone metabolism before and after antipsychotic initiation in FEB is, I believe as you stated, unprecedented.

You have clearly referenced recent metabolic psychiatry and ketogenic diet studies related to serious mental illnesses (Lines 77-89), briefly provided examples of existing PET studies (Lines 94-96) and explicitly mentioned the absence of direct measurement of brain glucose and ketone metabolism in FEP (Lines 90-92). A possible improvement would be to add a short paragraph summarizing recent PET imaging or relevant metabolic intervention studies in psychosis if they exist or are underway in clinical trials. This would strengthen the claim making the claim of novelty explicit, verifiable and contextualized clearly within existing research, but only as manuscript length allows. What has already been provided in the manuscript is sufficient. This could be reserved for subsequent publications reporting empirical results from this protocol.

I appreciate that one of the exclusion criteria is “psychosis induced by drug use or withdrawal” and I like that you state clearly a psychiatrist will make that determination through review of patient file, psychiatric interview and first eligibility visit by a researcher team member. I think that this may still be difficult to determine. Will any standardized structured interviews or special clinical instruments be used to help determine this? Will you rely on or conduct toxicology screenings to rule out recent drug use. How will it be determined in cases of chronic drug use leading up to first psychosis? It may help other researchers using this protocol to have that level of detail from your work.

The Aarhus site explicitly mentions having access to MRS to measure GABA. Given the significant metabolic relevance of glutamate, and emerging evidence suggesting substantial glutamatergic reductions with other metabolic interventions (e.g., ketogenic diets), I suggest considering measuring brain glutamate levels via MRS at sites with available equipment. Or possibly peripheral biomarkers reflecting glutamatergic metabolism could also be explored, if feasible. Including glutamate measurements would allow valuable comparison with metabolic changes seen in other interventions and disorders, potentially clarifying how antipsychotic initiation uniquely affects glutamate metabolism in first-episode psychosis. I do recognize, however, that funding or logistical constraints may not allow for such an expansion; I suggest this merely because it could provide interesting insights.

In regards to secondary and exploratory objectives, these are well aligned. I wonder if the use of a standardized quality of life measure as used in other metabolic psychiatry studies would be well-aligned and enrich the interpretation of the primary outcomes.

Given that sleep disturbances are both common in first episode psychosis and frequently affected (either positively or negatively) by antipsychotic treatment, sleep disruption could represent a confounding variable as you are studying metabolism in this population. I am wondering if explicitly clarifying how you will evaluate this in your statistical analysis plan would strengthen the protocol. Or a mention of whether or how you intend to account analytically for variations in sleep disruption (as measured by the Epworth Sleepiness Scale).

Wilcoxon is clearly justified in the text and appropriate given the sample size and repeated-measures design. Correlational analysis is appropriate, straightforward and adequately described. I particularly like the proposed use of Federated Learning (as described in lines 287-289) as an ethical and statistical choice in studying this vulnerable population across international sites.

Overall this protocol is very well done, methodologically sound, extremely clean and professional. That said, I found just a few minor punctuation and formatting points.

Line 95: "… aripiprazole and ziprasidone are reported be associated …" Correction: should be "are reported to be associated" (missing the word "to").

Lines 164-165: "The exception will be aripiprazole if it taken at less than 2.5 mg/day…" Correction: should be "if it is taken…" (missing the word "is").

Line 249: "Side effects of AP will be measured by the (i) Side Effect Rating Scale (SERS-UKU), and the Barnes Akathysia Scale (BAS)." Correction: No comma needed before "and" here since only two items are listed. Better phrasing: "...measured by the Side Effect Rating Scale (SERS-UKU) and the Barnes Akathisia Scale (BAS)."

Line 357: "Academic Scholars Awrard" Correction: should be "Academic Scholars Award" (typo).

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Reviewer #1: No

Reviewer #2: Yes:  Nicole Laurent

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Brain glucose and ketone metabolism in first-episode psychosis: neuroimaging and brain metabolism before and after antipsychotic treatment: the protocol for the CAST-ATP study

PONE-D-25-06878R1

Dear Dr. Hahn,

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.

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Kind regards,

Colin Johnson, Ph.D.

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Does the manuscript provide a valid rationale for the proposed study, with clearly identified and justified research questions?

The research question outlined is expected to address a valid academic problem or topic and contribute to the base of knowledge in the field.

Reviewer #1: Yes

Reviewer #2: Yes

**********

2. Is the protocol technically sound and planned in a manner that will lead to a meaningful outcome and allow testing the stated hypotheses?

The manuscript should describe the methods in sufficient detail to prevent undisclosed flexibility in the experimental procedure or analysis pipeline, including sufficient outcome-neutral conditions (e.g. necessary controls, absence of floor or ceiling effects) to test the proposed hypotheses and a statistical power analysis where applicable. As there may be aspects of the methodology and analysis which can only be refined once the work is undertaken, authors should outline potential assumptions and explicitly describe what aspects of the proposed analyses, if any, are exploratory.

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Is the methodology feasible and described in sufficient detail to allow the work to be replicable?

Descriptions of methods and materials in the protocol should be reported in sufficient detail for another researcher to reproduce all experiments and analyses. The protocol should describe the appropriate controls, sample size calculations, and replication needed to ensure that the data are robust and reproducible.

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Have the authors described where all data underlying the findings will be made available when the study is complete?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception, at the time of publication. 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 and, if applicable, provide comments about issues authors must address before this protocol can be accepted for publication. You may also include additional comments for the author, including concerns about research or publication ethics.

You may also provide optional suggestions and comments to authors that they might find helpful in planning their study.

(Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: All comments have been addressed adequately with the revisions included as needed.

As an exploratory/feasibility investigation, this will suffice.

Reviewer #2: This protocol is ready for publication. It has been well thought out and is thorough. I have no concerns it will not allow testing the stated hypotheses. It is technically sound and planned in a manner that will lead to meaningful outcomes. The writing is clear, presented in an intelligible fashion and written in standard English.

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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: Yes:  Nicole Laurent

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