Human Pancreatic Islets React to Glucolipotoxicity by Secreting Pyruvate and Citrate

Round 1

Reviewer 1 Report

Main problem is the data presentation, inconsistency or lack of explanation why different data sets are used in different analysis, repeated lack of explanation of abbrevations. Attached are my comments.

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

The authors investigated the effect of glucolipotoxicity on cellular metabolite in human pancreatic beta cells and INS-1 cells. And they also demonstrated that glucolipotoxicity induced the increase of pyruvate/citrate/lipid secretion through the downregulation of mitochondrial OGDM while it induced the decrease of insulin secretion/contents.

However, additional experiments are required:

1) effects of OGDM overexpression on insulin, pyruvate, citrate or lipid secretion in high glucose and/or palmitate –treated INS-1 cells.

2) effects of OGDM overexpression on the expression levels of PDH, pPDH, IDH2, ACLY, ACC or FASN in high glucose and/or palmitate –treated INS-1 cells.

3) effects of OGDM siRNA (knock-down) on insulin, pyruvate, citrate or lipid secretion in normal condition of INS-1 cells.

4) Please change tables 2 and 3 to supplementary data. Instead, please make a new figures of the main data in tables 2 and 3 (e.g. pyruvate, citrate, etc.)

Minor editing of English language required

Author Response

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Reviewer 3 Report

Perrier and colleagues present an interesting study exploring the impact of glucolipotoxic conditions on pancreatic beta-cell metabolism. Whilst others have published in this area, typically using rodent cell lines; this study additionally explores this question in human islets exposed to these conditions, and also in T2D islets. This significantly improves the importance of these findings. The experimental approach was sound (aside from the comment below), and the conclusions drawn reasonable. The final summary figure was helpful.

The authors suggest that the glucolipotoxic conditions cause a reduction in cell viability in the INS cells. No viability proxy was assessed in human islets, but it is likely that there would be some loss of cells here also. Given that the supernatant in which these cells have been cultured for 48h is used for metabolomic analysis, can the authors be sure that the increased levels of metabolites observed are not simply due to the increased number of lysed cells in these samples?

Minor issues:

Pg 4: Please include antibody dilutions for all antibodies used.

Tables: The metabolic information provided in the tables in this study is somewhat overwhelming. I would suggest presenting the information in this format in the supplementary tables, but then to find a more reader friendly way to summarise these data within the main figures.

P16 line 395. The authors state that cell numbers were reduced by glucolipotoxic conditions. It was not made clear whether any measure of cell viability was collected to inform these conclusions (e.g. trypan blue). Differences in cell number between conditions may not reflect changes in viability.

Sup Fig 6c: Can the authors please include information on the number of independent replicates conducted to generate these data.

Author Response

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Reviewer 4 Report

Perrier et al. examined the impact of glucolipotoxicity on pancreatic islets, with a specific emphasis on mitochondria function. The study highlights a novel metabolomics method and provides some new information on the metabolic alterations of beta cells in response to the diet-induced stress condition. Although the conclusion is confirmatory, it provides some new evidence. I commend the authors for sophisticated statistical analysis of their profiling results and a well-written manuscript.

I have some minor points to improve the manuscript:

1. The authors should consider replacing the title.
2. Line 85 typo “inc”.
3. Line 625 typo “TD2”.
4. I felt like these tables were hard to read. It might be better to considering add up or down arrow indicators to the table to help the readers.

Author Response

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Round 2

Reviewer 2 Report

The authors investigated the effect of glucolipotoxicity on cellular metabolite in human pancreatic beta cells and INS-1 cells. And they also demonstrated that glucolipotoxicity induced the increase of pyruvate/citrate/lipid secretion through the downregulation of mitochondrial OGDM while it induced the decrease of insulin secretion/contents. Although this study lacks mechanistic studies on the role of OGDM in pancreatic beta cells, this study focuses on the analyses of exometabolome using human pancreatic islets. And the manuscript was revised to the reviewer's suggestion.

Author Response

The authors appreciate that the corrections made to the manuscript satisfy the reviewer. Thank you very much for your consideration