Analysis of Methylglyoxal Concentration in a Group of Patients with Newly Diagnosed Prediabetes

Round 1

Reviewer 1 Report (Previous Reviewer 1)

Comments and Suggestions for Authors

In my opinion, the authors made the necessary corrections in the text of the manuscript according to my recommendations, the manuscript has been improved, so I believe that now can be considered for the publication.

Reviewer 2 Report (Previous Reviewer 2)

Comments and Suggestions for Authors

No comments

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In the manuscript, the authors are interested in methylglyoxal analysis as possible early predictor of cardiovascular complications or as a suitable marker of statins treatment in group of prediabetic patients. Although the idea of this study is interesting, useful and can have clinical message, I have fundamental comments to this study:

-          First of all, I have fundamental comments about group of patients, their characterisition, the number of participants, the criteria on the basis of which they were selected. I think, in the method, section it is necessary to clarife the criteria and parameters according to which the participants were selected into the groups. What was a prediabetic marker? Was is non-fasting glucose or was oGTT done? Further, according to which „fatty liver“ was evaluated? The authors must add these information.

-          I also have a fundamental comment about non-existing differences in lipid parameters as the authors mention. A third of patients used statins and even one used fibrate. This is consistent with the fact that prediabetes is often associated with dyslipidemia, even before the manifestation of hyperglycemia or impaired glucose tolerance. So the authors' statement that the groups did not differ in lipid parameters is not correct, the patients are treated for dyslipidemia.  In my opinion, the patients using statins must be removed and more suitable participants should be added to this group and this group of patients should be a separate group. Although the authors mention it in the limitation of the study, the number of participants is really small and the groups are numerically imbalanced between themselves (in my opinion, the minimum number in each group should be 40). A group of diabetic patients type 2 would also be appropriate and useful.

-          In addition, as regards formal deficiencies in Tables 1 and 2: the numbers should contain a decimal point; AlT expression should be replaced by ALT expression; HDL and LDL should be HDL-C and LDL-C; TC would be a better term for total cholesterol.  

-          Further, in my opinion, the result section should be added by other correlation of MGO with fasting glucose, Tg or with some markers of „fatty liver“, which would suitably complement than presenting significant correlation with HbA1c. Even if they were not significant.

-          A modern and sofisticated analytical method were used to determine MGO concentrations. It is a great pity that the authors did not measure the levels of other dicarbonyls such as glyoxal or 3-deoxyglucosone or MG-H1 adducts. The results would be complex and the devise used would be able to do it.

-          Further, in my opinion, the conclusion should be better and widely expressed based on study results.

-          Finally, I recommend the authors have English language proofreading done.

With regards to fundamental comments I cannot recommend this manuscript to the publication in Biomedicine journal in this version, as it is. However, the results of this study can be useful and could have a clinical message. Therefore I encourage the authors to add, recalculate and rework the study results and in my opinion after major revision the manuscript can be possible consider to the publication in this journal.

Comments on the Quality of English Language

I recommend the authors have English language proofreading done.

Author Response

Dear Editors / Dear Reviewers

Thank you very much for your comments and deep analysis. Below you can find our answers and clarification. The corrections are in yellow within the text. 

Reviewer 1

“ In the manuscript, the authors are interested in methylglyoxal analysis as possible early predictor of cardiovascular complications or as a suitable marker of statins treatment in group of prediabetic patients. Although the idea of this study is interesting, useful and can have clinical message, I have fundamental comments to this study:

-          First of all, I have fundamental comments about group of patients, their characterisition, the number of participants, the criteria on the basis of which they were selected. I think, in the method, section it is necessary to clarife the criteria and parameters according to which the participants were selected into the groups. What was a prediabetic marker? Was is non-fasting glucose or was oGTT done? Further, according to which „fatty liver“ was evaluated? The authors must add these information.

Answer:

- Dear Reviewer in the Materials and Method section we precise that “Frozen serum samples from patients with newly diagnosed IFG and/or IGT, diagnosis based on European Association for the Study of Diabetes (EASD) criteria [17],…”  We are very sorry but it is not used to copy the criteria "point by point" from the guidelines into the manuscript,  but rather reference the Diagnostic guidelines based on the available documents. The reference no 17 provides the name of the basic document. However, as we do not want to disturb you from checking them, below we put them but it does not seem to be necessary to copy them into the main text in our opinion.

IFG:      only FG : 100-125 mg%

IGT:      only 2 h glu level : 140-199 mg% in OGTT with 75 glu

IFG and IGT:     both: FG and 2 h glu level criteria met

If the patient met one or both criteria, he or she had the diagnosis pre-DM. Patients who did not meet the criteria were found as healthy.

The fatty liver was diagnosed only on the basis of the ultrasound examination- results from the patient’s record. We add this information to the main text Material and Method section.

More information was summarized in the text as follows: “In addition, in order to characterize the groups and assess the potential impact of other factors on the concentration of MGO, data from the interview, physical examination and the results of basic laboratory tests, which were previously collected in the study in which these people participated, were used [18].”

This is because as we mention in the article we analyzed samples that were collected previously for the other study ( ref no 18) and then frozen for future, additional analysis after the Bioethics Committee agreement. Figure S1 gives also more information about the basic characteristics and was added as Supplementary Materials.

 

“-          I also have a fundamental comment about non-existing differences in lipid parameters as the authors mention. A third of patients used statins and even one used fibrate. This is consistent with the fact that prediabetes is often associated with dyslipidemia, even before the manifestation of hyperglycemia or impaired glucose tolerance. So the authors’ statement that the groups did not differ in lipid parameters is not correct, the patients are treated for dyslipidemia.  In my opinion, the patients using statins must be removed and more suitable participants should be added to this group and this group of patients should be a separate group. Although the authors mention it in the limitation of the study, the number of participants is really small and the groups are numerically imbalanced between themselves (in my opinion, the minimum number in each group should be 40). A group of diabetic patients type 2 would also be appropriate and useful.”

Answer:

• The patients did not differ "biochemically" in terms of the levels of lipids' components- this is just the fact. How this was achieved is another matter that we stressed in the text. Because, like you, we believe that the use of statins could have an impact on the further fate of a patient with prediabetes, we came up with the idea that the use of statins could have influenced further results, i.e. MGO levels. In the limitation, we discussed this issue. We mentioned also in the Discussion that:

“We suggest that such an observation should cover: i) a larger group of participants, ii) pre- and post-statin MGO concentration assessment…”

- The fact that the groups we analyzed are small, results from the nature of the study, which is a basic one. To plan large studies, preliminary analyses are always performed to show whether further research is warranted. In the text, we clearly indicated the nature of the study. Despite common knowledge about the role and construction of basic research, below we allow ourselves to quote a website with an example of knowledge on this subject

https://www.nngroup.com/articles/summary-quant-sample-sizes/

Please also find that: “Basic research is experimental or theoretical work undertaken primarily to acquire new knowledge of the underlying foundations of phenomena and observable facts, without any particular application or use in view. Basic research analyzes properties, structures, and relationships with a view to formulating and testing hypotheses, theories or laws. The results of basic research have no direct or immediate commercial benefits, but are usually published in scientific journals or circulated to interested parties(..)”

[https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Glossary:Basic_research].

 We showed in our study a correlation between the HbA1c level and the concentration of MGO (methylglyoxal) which is similar to the other studies. So the group was not too small to find statistical significance when it was even if the group/s were small.

- The study was dedicated to pre-DM, not DM. Data about MGO in diabetes are more widely available which is why we focused on pre-DM.

 

 

“-          In addition, as regards formal deficiencies in Tables 1 and 2: the numbers should contain a decimal point; AlT expression should be replaced by ALT expression; HDL and LDL should be HDL-C and LDL-C; TC would be a better term for total cholesterol.  “

Answer:

Has been corrected in text and table.

The first point is not clear to us- do you mean that we have to replace commas with dots?

“-          Further, in my opinion, the result section should be added by other correlation of MGO with fasting glucose, Tg or with some markers of „fatty liver“, which would suitably complement than presenting significant correlation with HbA1c. Even if they were not significant.”

Answer:

The articles have a limited number of supplements. Statistically non-significant information is not customarily added to the text, especially if it does not relate to essential results. We put the information about HbA1c just to show that our small, basic study confirms the known fact that this parameter is connected with MGO. We prepared it for you and hopefully, you can find it as the additional attachment to this letter. If in the Editor's opinion, it should be added to the manuscript we will attach the extra Figures to the text.

“-          A modern and sofisticated analytical method were used to determine MGO concentrations. It is a great pity that the authors did not measure the levels of other dicarbonyls such as glyoxal or 3-deoxyglucosone or MG-H1 adducts. The results would be complex and the devise used would be able to do it.”

Answer:

We are very sorry the budget is limited for MGO in this study. Yes we agree,  it is a pity.

“-          Further, in my opinion, the conclusion should be better and widely expressed based on study results.”

The Conclusion section, as recommended by the journal, is intended to be a concise summary of the results. The main problem analyzed in our study was the concentration of MGO in the group of patients with pre-DM vs healthy. An additional observation resulting from the results of the basic characteristics analysis was the fact that statins were taken only by patients with pre-diabetes. Only this fact could, in our opinion, influence the surprising result of no differences in MGO concentration between the two groups. However, since, as you note yourself, the lipid levels were probably lower in pre-DM due to the use of statins, the conclusion of whether these drugs modify the MGO concentration is only possible if the study was of an interventional nature, i.e. when we examine the MGO concentration before and after the administration of statins in groups that do not differ among themselves. For this reason, we cannot develop this thread in any other, stronger, way in the Conclusion... although it is very important. However, we referred to it in the discussion, not in the conclusion.

Summarized: the main topic was the differences between the groups regards the MGO concentration thus the conclusion should concentrate on it...also because nothing more was found. We only add the information about HbA1c, but it is not surprising and the fact is known.

 

“-          Finally, I recommend the authors have English language proofreading done.”

Answer:

The Translation Quality Certificate from the authorized language center was sent to the editor's office.

We remain hopeful that our explanations and additions will be sufficient for publication.

Reviewer 2 Report

Comments and Suggestions for Authors

[1]. The language needs editing

[2]. The study seems grossly underpowered - sample size calculation or attained power seem to be needed

[3]. The correlation MGO vs A1c is moderate at most (R2=0.25)

[4]. Introduction: prediabetes leads often - but not always - to type 2 diabetes.

Comments on the Quality of English Language

A study needing a linguistic overhaul.

Author Response

Thank you very much for your comments. Below you can find our answers and clarification. The corrections are in yellow within the text.

Comments and Suggestions for Authors

“[1]. The language needs editing”

Answer:

The Translation Quality Certificate from the authorized language center was sent to the editor's office.

 

“[2]. The study seems grossly underpowered - sample size calculation or attained power seem to be needed”

Answer:

For statistically insignificant results, it is not customary to perform a power analysis of the test. No power analysis is performed for correlations.

The fact that the groups we analyzed are small, results from the nature of the study, which is a basic one. To plan large studies, preliminary analyses are always performed to show whether further research is warranted. In the text, we clearly indicated the nature of the study. Despite common knowledge about the role and construction of basic research, below we allow ourselves to quote a website with an example of knowledge on this subject.

https://www.nngroup.com/articles/summary-quant-sample-sizes/

Please also find that: “Basic research is experimental or theoretical work undertaken primarily to acquire new knowledge of the underlying foundations of phenomena and observable facts, without any particular application or use in view. Basic research analyzes properties, structures, and relationships with a view to formulating and testing hypotheses, theories or laws. The results of basic research have no direct or immediate commercial benefits, but are usually published in scientific journals or circulated to interested parties(..)”

[https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Glossary:Basic_research].

 We showed in our study a correlation between the HbA1c level and the concentration of MGO (methylglyoxal) which is similar to the other studies. So the group was not too small to find statistical significance when it was even if the group/s were small.

“[3]. The correlation MGO vs A1c is moderate at most (R2=0.25)”

Answer:

The correlation is moderate in value but is statistically significant, which is why it was included.

“[4]. Introduction: prediabetes leads often - but not always - to type 2 diabetes.”

Answer:

Yes, we totally agree that is why we start the manuscript with the sentence: “ Prediabetes (pre-DM) can lead to diabetes mellitus….” – not: Prediabetes leads to….

We remain hopeful that our explanations and additions will be sufficient for publication.

 

 

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

According to my recommendations, the authors made the necessary additions and corrections in whole manuscript.

Reviewer 2 Report

Comments and Suggestions for Authors

The Authors' responses do not satisfy this Reviewer - they stand firm in the same way of presenting their work