Possible Modifying Effect of Hemoglobin A1c on Genetic Susceptibility to Severe Diabetic Retinopathy in Patients With Type 2 Diabetes

Younger Age and Albuminuria are Associated with Proliferative Diabetic Retinopathy and Diabetic Macular Edema in the South Indian GeNetics of DiAbeTic Retinopathy (SIGNATR) Study

Purpose: The purpose of the South Indian GeNetics of DiAbeTic Retinopathy (SIGNATR) Study is to identify non-genetic and genetic risk factors associated with diabetic retinopathy (DR). This report examines the non-genetic risk factors for DR in South Indian patients.Methods: Participants with South Indian ancestry and type 2 diabetes (T2D) were included from two sources: the Sankara Nethralaya Diabetic Retinopathy and Molecular Genetics Study (SN-DREAMS) and prospective recruitment at Sankara Nethralaya affiliates. Fundus photography and optical coherence tomography (OCT) were obtained on participants. Fundus images were graded for DR severity and OCTs were graded for center-involved diabetic macular edema (ciDME). Multivariate analyses were performed using stepwise logistic regression to assess effects of the demographic and clinical factors on proliferative DR (PDR) and DME.Results: Among the 2941 participants with DR grading, participants with PDR were more likely to be younger [odds ratio (OR)=0.95], men (OR = 1.83), have a longer duration of diabetes (OR = 1.10), have a higher hemoglobin A1c (OR = 1.12), have albuminuria (OR = 5.83), have hypertension (OR = 1.69), have a higher HDL (OR = 1.02) and a lower total cholesterol (OR = 0.99) (all p < 0.05). Among the 483 participants with gradable OCT scans, participants who had ciDME were more likely to be younger (OR = 0.97), men (OR = 2.80), have a longer duration of diabetes (OR = 1.06), have lower triglycerides (OR = 0.99), and have albuminuria (OR = 3.12) (all p < 0.05).Conclusions: Younger age, male sex, longer duration of diabetes, higher HbA1c, and presence of albuminuria were identified as risk factors for PDR and DME in a South Indian population with T2D.

Potential underlying genetic associations between keratoconus and diabetes mellitus

Background Keratoconus (KC) is the most common ectatic corneal disease, characterized by significantly localized thinning of the corneal stroma. Genetic, environmental, hormonal, and metabolic factors contribute to the pathogenesis of KC. Additionally, multiple comorbidities, such as diabetes mellitus, may affect the risk of KC. Main Body Patients with diabetes mellitus (DM) have been reported to have lower risk of developing KC by way of increased endogenous collagen crosslinking in response to chronic hyperglycemia. However, this remains a debated topic as other studies have suggested either a positive association or no association between DM and KC. To gain further insight into the underlying genetic components of these two diseases, we reviewed candidate genes associated with KC and central corneal thickness in the literature. We then explored how these genes may be regulated similarly or differentially under hyperglycemic conditions and the role they play in the systemic complications associated with DM. Conclusion Our comprehensive review of potential genetic factors underlying KC and DM provides a direction for future studies to further determine the genetic etiology of KC and how it is influenced by systemic diseases such as diabetes.

Harboyan syndrome: novel SLC4A11 mutation, clinical manifestations, and outcome of corneal transplantation

Harboyan syndrome or corneal dystrophy and progressive deafness (MIM #217400) is characterized by congenital hereditary endothelial dystrophy (CHED) and progressive, sensorineural hearing loss. Mutations in SLC4A11 are responsible for this rare genetic syndrome. Eight patients from seven unrelated families affected with Harboyan Syndrome with mean follow-up of 12.0 ± 0.9 years were thoroughly investigated for the ocular, hearing, and kidney function abnormalities and the outcome of penetrating keratoplasty (PK). Mutation analysis of SLC4A11 was performed. All patients presented with bilateral cloudy corneas since birth. Sensorineural hearing loss was detected in all patients. Seven patients (11 eyes) underwent PK with the median age at surgery of 10.1 years (7.1-22.9). The overall corneal graft survival rate after primary PK was 72.7% (8/11 eyes). The mean graft survival time was 94.6 months (95% CI 83.1-126.0). All patients had unremarkable kidney function. The c.2264G>A (p.Arg755Gln) mutation in SCL4A11 was detected in most patients (87.5%). All unrelated Karen tribe patients had p.Arg755Gln mutation, suggestive of founder effect. We found the allele frequency of this variant in the Karen population to be 0.01. The c.2263C>T (p.Arg755Trp) mutation was found in one patient with mild phenotype and the novel truncating protein mutation c.2127delG (p.Gly710fsx*25) in SCL4A11 was identified in two Thai sisters. Visual outcome and graft survival after PK were satisfactory. Our study shows that all studied patients with SLC4A11 mutations had CHED and sensorineural hearing loss, and SLC4A11 mutations were not related to the onset and severity of hearing loss or outcome of keratoplasty.