New-Onset Diabetes Mellitus after COVID-19: Combined Effects of SARS-CoV-2 Variants, Molecular Mimicry, and m6A RNA Methylation

Round 1

Reviewer 1 Report

1.       This is an excellent review about the association between SARS-CoV-2 infection and the development of diabetes mellitus, and provides updated information on the possible molecular mechanisms involved. However, I kindly suggest that the authors re-organize the text so that the reader can more easily understand this information. For example: On line 116, the authors mention that “Different molecular mechanisms have been proposed to explain NODAC”.  From lines 116 to 139 the authors described relevant information regarding the role of m6A methylation.  However, the authors continued analyzing more information on m6A again on lines 289 to 320.  I kindly suggest the authors to merge all information regarding m6A and create a section including such data.

I propose the following structure for this review:

1.       Introduction

2.       Molecular mechanisms involved in NODAC development

2.1. Alterations of m6A RNA methylation patterns

2.1.1.       Alterations in immune cells from diabetic patients 

2.1.2.       Alterations in beta cells from diabetic patients

2.1.3.       Alterations in m6A methylation induced by mRNA vaccines*

2.2. Diabetes mellitus: beta pancreatic cell destruction and dysfunction

2.3. Direct SARS-CoV-2 invasion of beta cells

2.4. Autoimmune responses induced by SARS-CoV-2

2.4.1.       Molecular mimicry

2.4.2.       Cytokine storm

2.5. Alterations by different SARS-CoV-2 variants

3.       Concluding remarks

 * It is now well recognized that SARS-CoV-2 infection can trigger many autoimmune disorders, including T1DM and T2DM. However, the dominant paradigm regarding COVID-19 vaccines is that they are safe and effective. I strongly suggest to include more information on the possibility that these vaccines can also induce diabetes in susceptible individuals. On line 16-17 the authors wrote: “ It  has been reported that COVID-19 mRNA vaccination can induce T1DM in some individuals with a genetic predisposition [34], even in adults [35].

“ We previously  reported  that  m6A  levels  were  significantly  lower  in  individuals  infected with SARS-CoV-2 variants delta and omicron compared to other variants and uninfected individuals [39]”.

Ref. 39 is from a previous work by these authors. This work is particularly interesting because the authors found that “individuals with complete vaccination schemes showed significantly lower m6A levels than unvaccinated individuals (p = 2.6 X10 ^-4), and differences in methylation levels across variants in unvaccinated individuals were significant (p = 3.068 X10^-3).  Importantly, we show that the variation in m6A levels across variants, in particular the low levels in delta and omicron, could not be explained by vaccination status alone. While changes in DNA methylation levels have been reported after influenza vaccination [27,28], there is no information regarding RNA methylation after vaccination. Potential vaccination-mediated m6A is intriguing and deserves further investigation. 

2.       Question: Since the authors informed us (lines 126 and 127) that “depletion of m6A methylation levels in beta cells induced cell cycle arrest, decreased beta cell proliferation, and impaired insulin degranulation and secretion”,

              Is it possible that mRNA vaccines could induce an autoimmune response and cause T1DM by mediating a  decrease in m6A levels?

Same suggestions

Author Response

We would like to thank the reviewers for their constructive criticism and valuable suggestions. Modifications suggested by Reviewer 1 are highlighted in blue, and those from Reviewer 2 are highlighted in yellow within the document.

Reviewer 1 (The answer is at the end)

This is an excellent review about the association between SARS-CoV-2 infection and the development of diabetes mellitus, and provides updated information on the possible molecular mechanisms involved. However, I kindly suggest that the authors re-organize the text so that the reader can more easily understand this information. For example: On line 116, the authors mention that “Different molecular mechanisms have been proposed to explain NODAC”. From lines 116 to 139 the authors described relevant information regarding the role of m6A methylation. However, the authors continued analyzing more information on m6A again on lines 289 to 320. I kindly suggest the authors to merge all information regarding m6A and create a section including such data. 

I propose the following structure for this review:

1. Introduction. 2. Molecular mechanisms involved in NODAC development. 2.1. Alterations of m6A RNA methylation patterns. 2.1.1. Alterations in immune cells from diabetic patients. 2.1.2. Alterations in beta cells from diabetic patients. 2.1.3. Alterations in m6A methylation induced by mRNA vaccines*. 2.2. Diabetes mellitus: beta pancreatic cell destruction and dysfunction. 2.3. Direct SARS-CoV-2 invasion of beta cells. 2.4. Autoimmune responses induced by SARS-CoV-2. 2.4.1. Molecular mimicry. 2.4.2. Cytokine storm. 2.5. Alterations in m6A methylation by different SARS-CoV-2 variants. 3. Concluding remarks.

 * It is now well recognized that SARS-CoV-2 infection can trigger many autoimmune disorders, including T1DM and T2DM. However, the dominant paradigm regarding COVID-19 vaccines is that they are safe and effective. I strongly suggest to include more information on the possibility that these vaccines can also induce diabetes in susceptible individuals. On line 16-17 the authors wrote: “ It  has been reported that COVID-19 mRNA vaccination can induce T1DM in some individuals with a genetic predisposition [34], even in adults [35].

“ We previously  reported  that  m6A  levels  were  significantly  lower  in  individuals  infected with SARS-CoV-2 variants delta and omicron compared to other variants and uninfected individuals [39]”.

Ref. 39 is from a previous work by these authors. This work is particularly interesting because the authors found that “individuals with complete vaccination schemes showed significantly lower m6A levels than unvaccinated individuals (p = 2.6 X10 ^-4), and differences in methylation levels across variants in unvaccinated individuals were significant (p = 3.068 X10^-3).  Importantly, we show that the variation in m6A levels across variants, in particular the low levels in delta and omicron, could not be explained by vaccination status alone. While changes in DNA methylation levels have been reported after influenza vaccination [27,28], there is no information regarding RNA methylation after vaccination. Potential vaccination-mediated m6A is intriguing and deserves further investigation.

Question: Since the authors informed us (lines 126 and 127) that “depletion of m6A methylation levels in beta cells induced cell cycle arrest, decreased beta cell proliferation, and impaired insulin degranulation and secretion”. Is it possible that mRNA vaccines could induce an autoimmune response and cause T1DM by mediating a decrease in m6A levels?

We thank the reviewer for helping reorganize the content of the document.  The manuscript was reorganized as suggested by the reviewer, and included the subsection 2.1.3 (Alterations in m6A methylation induced by mRNA vaccines), the reviewer made a very interesting point about the possible influence of COVID vaccines on the development of autoimmune diseases in susceptible individuals. We included more information on the subject.

The possibility that mRNA vaccines could induce an autoimmune response (and cause T1DM) by mediating a decrease in m6A levels exists, and (definitively) more studies are needed.  

Reviewer 2 Report

This is a clear, comprehensive, well-written paper summarizing the latest findings regarding the possible mechanisms involved in the development of diabetes mellitus in the post-COVID-19 era, with a focus on the particular impact of SARS-CoV-2 variants on molecular mimicry, the role of viral m6A RNA methylation, and potential associations between these factors. The points are clearly presented and the conclusions are correct. I agree with the authors that a better understanding of the associations between these mechanisms is important to clinicians and researchers due to more effective treatment strategies, improved patient care, and future research efforts.  Unusually, there are no cited previous works of the authors in the review paper. If it does not hinder publication, I suggest that the work be accepted in its present form.

Minor point:

1.      Page 2, line 55: CoV-2 instead C0V-2

2.      Page 2: lines 91 and 94: instead of the year 2022, reference numbers 21 and 22 should be added in parentheses.

3.      Add the full name of the abbreviation METTL3 and 14 (methyltransferase-like 3 or 14), WTAP (Wilms' tumor 1-associated protein), FTO...

Minor point:

1.      Page 2, line 55: CoV-2 instead C0V-2

2.      Page 2: lines 91 and 94: instead of the year 2022, reference numbers 21 and 22 should be added in parentheses.

3.      Add the full name of the abbreviation METTL3 and 14 (methyltransferase-like 3 or 14), WTAP (Wilms' tumor 1-associated protein), FTO...

Author Response

We would like to thank the reviewers for their constructive criticism and valuable suggestions. Modifications suggested by Reviewer 1 are highlighted in blue, and those from Reviewer 2 are highlighted in yellow within the document.

Reviewer 2

This is a clear, comprehensive, well-written paper summarizing the latest findings regarding the possible mechanisms involved in the development of diabetes mellitus in the post-COVID-19 era, with a focus on the particular impact of SARS-CoV-2 variants on molecular mimicry, the role of viral m6A RNA methylation, and potential associations between these factors. The points are clearly presented and the conclusions are correct. I agree with the authors that a better understanding of the associations between these mechanisms is important to clinicians and researchers due to more effective treatment strategies, improved patient care, and future research efforts.  Unusually, there are no cited previous works of the authors in the review paper. If it does not hinder publication, I suggest that the work be accepted in its present form.

Minor point:

1. Page 2, line 55: CoV-2 instead C0V-2. CoV-2 was corrected, thank you.
2. Page 2: lines 91 and 94: instead of the year 2022, reference numbers 21 and 22 should be added in parentheses. Involuntary mistake, thank you for pointing it out.
3. Add the full name of the abbreviation METTL3 and 14 (methyltransferase-like 3 or 14), WTAP (Wilms' tumor 1-associated protein), FTO... Fat mass and obesity-associated protein, alkB homolog 5. We added full names of ALL genes and proteins in the document, and corrected gene/protein nomenclature. Thank you.
   

Round 2

Reviewer 1 Report

All suggestions were satisfactorily addressed. 

The authors have made the corrections to the proposed suggestions, so I have no problem with the article being published. 

Thank you very much and congratulations for this excellent work!