Intraretinal Microvascular Abnormalities and Venous Beading Have Different Genetic Profiles in Caucasian Patients with Non-Proliferative Diabetic Retinopathy

Round 1

Reviewer 1 Report

The manuscript by Pearce et al., studied the genetic profiles of patients with non-proliferative diabetic retinopathy verus diabetic patients with no retinopathy. Given the increasing prevalence of diabetic retinopathy and no universal effective drug, the study is important for the field. However, I have following concerns: 

1) The title does not reflect that study is focused on Caucasians population and 3 pathways. 

2) Choice of selecting VEGF alone is not justified as anti-VEGF drugs are already in market and shown to not perform universally; therefore, it would have make sense to look for other factors such as angiopoitin-TIE2. 

3) Duration of diabetes is significantly higher in NPDR and IRMA groups compared to no DR. Would this will affect your results? None of the genes was significantly different in VB vs no DR group; these groups are most close in duration of diabetes? I think this is something worth considering. m

 

Author Response

Please see the attachment

Response to Reviewer 1’s comments

 

• The title does not reflect that study is focused on Caucasians population and 3 pathways.

 

Thank you for the suggestion, we have added Caucasian to the title. Our study is not pathway specific.

 

• Choice of selecting VEGF alone is not justified as anti-VEGF drugs are already in market and shown to not perform universally; therefore, it would have make sense to look for other factors such as angiopoitin-TIE2.

 

Thank you for the comment. The study was not to examine responses to treatment but to identify differences in the genetic predisposition of patients with VB and IRMA. No changes were made.

 

• Duration of diabetes is significantly higher in NPDR and IRMA groups compared to no DR. Would this will affect your results? None of the genes was significantly different in VB vs no DR group; these groups are most close in duration of diabetes? I think this is something worth considering.

 

The concern of the reviewer is well understood. The control group can develop these features in the future, which would make our findings more significant. Furthermore, the main purpose of the study is to focus on the differences between VB and IRMA. No changes were made.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors have presented a prospective case-control study of several selected SNPs of interest and compared between No DR vs NPDR as well as venous beading (VB) vs No DR and intraretinal microvascular abnormalities (IRMA) vs No DR. Based on these SNP testings, the authors concluded that patients with VB and IRMA have different genetic profiles from each other and from the No DR group. Although VB and IRMA are lumped together under “Severe NPDR”, these two retinal lesions might have different etiologies and different rates or progression. The genetic profile finding in the current study adds more strength to the authors’ hypothesis. Interestingly, the same group has previously reported that VB did not respond to anti-VEGF therapy unlike IRMA. This is a hypothesis driven study that is novel in its approach, and draws attention to different pathophysiological mechanisms for VB and IRMA.

 

COMMENTS:

1.     The major strength of this paper is the fundus imaging and grading of these images by independent readers for proper phenotyping of DR patients. Although the ultrawide field images were not taken for the NO DR Control group, it is still reasonably a good control group as there might be only a few patients who might have some peripheral lesions. 

2.     One of the weaknesses of the study is the CONTROL group that comprised of patients with NO DR and presence of diabetes for at least 5 years. As many of these patients may develop features of NPDR or VB or IRMA later by 10-15 years or more, this group seems to be not the ideal selection. Ideally, this NO DR group should have at least >15 years of diabetes without any signs of DR.

3.     Although the authors have studied the SNPs for candidate genes that might be of interest to pathophysiology of DR, the list misses some important cytokines like IL-6, TNFa and others that have been reported by others.

4. It is interesting that duration of diabetes and HbA1C levels were not significantly associated with VB or IRMA. The authors might expand on this finding in the Discussion as these two risk factors are well known for their association with NPDR as shown by many landmark studies.

Author Response

Please see the attachment

 

1 .           One of the weaknesses of the study is the CONTROL group that comprised of patients with NO DR and presence of diabetes for at least 5 years. As many of these patients may develop features of NPDR or VB or IRMA later by 10-15 years or more, this group seems to be not the ideal selection. Ideally, this NO DR group should have at least >15 years of diabetes without any signs of DR.

 

We agree that a longer duration of diabetes in the control group would be preferable. However, as the control group were older than the NPDR, the findings would only become more significant, as described in Table 1 and in line 181. No changes were made.

 

2. Although the authors have studied the SNPs for candidate genes that might be of interest to pathophysiology of DR, the list misses some important cytokines like IL-6, TNFa and others that have been reported by others.

 

TNFa and IL-6  may well be relevant for DR. Our initial review did not find consistent associations with DR, hence they were not included. It may be of interest to evaluate in the future. No changes were made.

 

3. It is interesting that duration of diabetes and HbA1C levels were not significantly associated with VB or IRMA. The authors might expand on this finding in the Discussion as these two risk factors are well known for their association with NPDR as shown by many landmark studies.

 

As shown in table 1, the HbA1c levels were higher in those with VB and IRMA compared to controls, and had a longer duration of diabetes. The reviewer might have confused with there were no significant difference between VB and IRMA. No changes were made.

 

Author Response File: Author Response.pdf

Reviewer 3 Report

This study investigates the genetic profile of diabetic patients with and without non-proliferative diabetic retinopathy (NPDR)with respect to microvascular pathology and venous beading. The authors hypothesize that genetic predispositions may contribute to differing DR phenotypes.  The manuscript in largely well written and provides new information on genetic variation in single gene polymorphisms associated with NPDR retinopathy vs no DR.

There are some questions and problems that should be addressed in order to increase ease of reading and clarity.

1.  The manuscript has very many abbreviations. It is very difficult to keep up with all of them. DH (deep haemorrhages) comes up once on page 2 along with VB and IRMA and reappears on page 6.  Suggest an alphabetic list of abbreviations be installed after the abstract .

2.  Three genes are not discussed (CFH, C5, VDR). A brief explanation on why SNPs of these genes were investigated would be informative..

3. Line 208. '...VB and IRMA..'

3.  Line 208

Author Response

Please see the attachment

 

1. The manuscript has very many abbreviations. It is very difficult to keep up with all of them. DH (deep haemorrhages) comes up once on page 2 along with VB and IRMA and reappears on page 6. Suggest an alphabetic list of abbreviations be installed after the abstract.

 

Thank you for the suggestion, we have added a list of abbreviations

 

2. Three genes are not discussed (CFH, C5, VDR). A brief explanation on why SNPs of these genes were investigated would be informative.

 

An explanation for the investigation of Complement was included in the discussion. We have added an explanation for VDR’s inclusion, line 219, as well as a sentence explaining that no associations were found with CFH, C5 and VDR, line 203

 

3. Line 208. '...VB and IRMA..'

 

Corrected the typo, thank you for finding it

 

4. Line 208

 

not sure what this means, this is where the typo above was corrected

 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Authors addressed my concerns