Proliferative retinopathy in a patient with diabetes mellitus and idiopathic haemochromatosis

Glaucoma-TrEl: A web-based interactive database to build evidence-based hypotheses on the role of trace elements in glaucoma

Objective

Glaucoma is a chronic neurological disease that is associated with high intraocular pressure (IOP), causes gradual damage to retinal ganglion cells, and often culminates in vision loss. Recent research suggests that glaucoma is a complex multifactorial disease in which multiple interlinked genes and pathways play a role during onset and development. Also, differential availability of trace elements seems to play a role in glaucoma pathophysiology, although their mechanism of action is unknown. The aim of this work is to disseminate a web-based repository on interactions between trace elements and protein-coding genes linked to glaucoma pathophysiology.

Results

In this study, we present Glaucoma-TrEl, a web database containing information about interactions between trace elements and protein-coding genes that are linked to glaucoma. In the database, we include interactions between 437 unique genes and eight trace elements. Our analysis found a large number of interactions between trace elements and protein-coding genes mutated or linked to the pathophysiology of glaucoma. We associated genes interacting with multiple trace elements to pathways known to play a role in glaucoma. The web-based platform provides an easy-to-use and interactive tool, which serves as an information hub facilitating future research work on trace elements in glaucoma.

Diabetic macular oedema: under-represented in the genetic analysis of diabetic retinopathy

Diabetic retinopathy, a complication of both type 1 and type 2 diabetes, is a complex disease and is one of the leading causes of blindness in adults worldwide. It can be divided into distinct subclasses, one of which is diabetic macular oedema. Diabetic macular oedema can occur at any time in diabetic retinopathy and is the most common cause of vision loss in patients with type 2 diabetes. The purpose of this review is to summarize the large number of genetic association studies that have been performed in cohorts of patients with type 2 diabetes and published in English-language journals up to February 2017. Many of these studies have produced positive associations with gene polymorphisms and diabetic retinopathy. However, this review highlights that within this large body of work, studies specifically addressing a genetic association with diabetic macular oedema, although present, are vastly under-represented. We also highlight that many of the studies have small patient numbers and that meta-analyses often inappropriately combine patient data sets. We conclude that there will continue to be conflicting results and no meaningful findings will be achieved if the historical approach of combining all diabetic retinopathy disease states within patient cohorts continues in future studies. This review also identifies several genes that would be interesting to analyse in large, well-defined cohorts of patients with diabetic macular oedema in future candidate gene association studies.

Iron Overload Accelerates the Progression of Diabetic Retinopathy in Association with Increased Retinal Renin Expression

Diabetic retinopathy (DR) is a leading cause of blindness among working-age adults. Increased iron accumulation is associated with several degenerative diseases. However, there are no reports on the status of retinal iron or its implications in the pathogenesis of DR. In the present study, we found that retinas of type-1 and type-2 mouse models of diabetes have increased iron accumulation compared to non-diabetic retinas. We found similar iron accumulation in postmortem retinal samples from human diabetic patients. Further, we induced diabetes in HFE knockout (KO) mice model of genetic iron overload to understand the role of iron in the pathogenesis of DR. We found increased neuronal cell death, vascular alterations and loss of retinal barrier integrity in diabetic HFE KO mice compared to diabetic wildtype mice. Diabetic HFE KO mouse retinas also exhibited increased expression of inflammation and oxidative stress markers. Severity in the pathogenesis of DR in HFE KO mice was accompanied by increase in retinal renin expression mediated by G-protein-coupled succinate receptor GPR91. In light of previous reports implicating retinal renin-angiotensin system in DR pathogenesis, our results reveal a novel relationship between diabetes, iron and renin-angiotensin system, thereby unraveling new therapeutic targets for the treatment of DR.

A hemochromatosis-causing mutation C282Y is a risk factor for proliferative diabetic retinopathy in Caucasians with type 2 diabetes

Iron metabolism might be involved in the pathogenesis of type 2 diabetes and in the pathogenesis of diabetic retinopathy. C282Y and H63D mutations in the hemochromatosis (HFE) gene are associated with increased serum iron levels and consequently with hereditary hemochromatosis. In the present study, we searched for a relationship between C282Y and H63D gene mutations and the development of proliferative diabetic retinopathy in Caucasians with type 2 diabetes. For this purpose, 90 subjects with type 2 diabetes with proliferative diabetic retinopathy (PDR) were compared to 133 diabetic subjects without PDR. There was a significantly higher frequency of the C282Y heterozygotes in patients with PDR compared to subjects without it (OR=3.0, 95% CI=1.2-8.0; p=0.02), whereas no association was demonstrated between PDR and H63D genotypes (OR=1.1, 95% CI=0.6-2.2; p=0.7). Logistic regression analysis revealed that the C282Y mutation was a significant independent risk factor for the development of PDR (OR=6.1, 95% CI=1.2-30.5; p=0.027). These data suggest that heterozygosity for C282Y might be a novel risk factor for PDR in Caucasians with type 2 diabetes.