Satagopan Uthra

Prevalence of Diabetic Retinopathy in India : Sankara Nethralaya Diabetic Retinopathy Epidemiology and Molecular Genetics Study Report 2

OBJECTIVE The aim of the study was to estimate the prevalence of diabetic retinopathy in an urban Indian population older than 40 years. DESIGN A population-based cross-sectional study. PARTICIPANTS Five thousand nine hundred ninety-nine subjects residing in Chennai, India, were enumerated. METHODS A multistage random sampling, based on socioeconomic criteria, was followed. Identified subjects with diabetes mellitus (based on the World Health Organization criteria) underwent detailed examination at the base hospital. The fundi of all patients were photographed using 45 degrees , 4-field stereoscopic digital photography. The diagnosis of diabetic retinopathy was based on Kleins classification of the Early Treatment Diabetic Retinopathy Study scale. MAIN OUTCOME MEASURES These included age- and gender-adjusted prevalence of diabetes and diabetic retinopathy, and correlation of prevalence with history-based risk factors. RESULTS The age- and gender-adjusted prevalence rate of diabetes in an urban Chennai population was 28.2% (95% confidence interval [CI], 27.0-29.3), and the prevalence of diabetic retinopathy in general population was 3.5% (95% CI, 3.49-3.54). The prevalence of diabetic retinopathy in the population with diabetes mellitus was 18.0% (95% CI, 16.0-20.1). History-based variables that were significantly associated with increased risk of diabetic retinopathy included gender (men at greater risk; odds ratio [OR], 1.41; 95% CI, 1.04-1.91); use of insulin (OR, 3.52; 95% CI, 2.05-6.02); longer duration of diabetes (>15 years; OR, 6.43; 95% CI, 3.18-12.90); and subjects with known diabetes mellitus (OR, 2.98; 95% CI, 1.72-5.17). Differences in the socioeconomic status did not influence the occurrence of diabetic retinopathy. CONCLUSIONS The prevalence of diabetic retinopathy was 18% in an urban population with diabetes mellitus in India. The duration of diabetes is the strongest predictor for diabetic retinopathy. FINANCIAL DISCLOSURE(S) The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Sankara Nethralaya—Diabetic Retinopathy Epidemiology and Molecular Genetic Study (SN—DREAMS 1): Study Design and Research Methodology

Purpose: To describe the methodology of the Sankara Nethralaya—Diabetic Retinopathy Epidemiology and Molecular Genetic Study (SN—DREAMS 1), an ongoing population-based study to estimate the prevalence of diabetes and diabetic retinopathy in urban Chennai, Tamil Nadu, South India, and also to elucidate the clinical, anthropometric, biochemical and genetic risk factors associated with diabetic retinopathy. Methods: In this ongoing study, we anticipate recruiting a total of 5830 participants. Eligible patients, over the age of 40 years, are enumerated using the multistage random sampling method. Demographic data, socioeconomic status, physical activity, risk of sleep apnea, dietary habits, and anthropometric measurements are collected. A detailed medical and ocular history and a comprehensive eye examination, including stereo fundus photographs, are taken at the base hospital. Biochemical investigations (total serum cholesterol, high-density lipoproteins, serum triglycerides, hemoglobin, glycosylated hemoglobin HbA1c) and genetic studies of eligible subjects are conducted. A computerized database is created for the records. Conclusion: The study is expected to result in an estimate of the prevalence of diabetes and diabetic retinopathy and a better understanding of biochemical and genetic risk factors associated with diabetic retinopathy in an urban South Indian population. Worldwide, the prevalence of diabetes mellitus, in particular type II diabetes, is rising at an alarming rate. The World Health Organization (WHO) and International Diabetes Federation (IDF) have predicted that the number of cases of adult-onset diabetes would more than double by 2030 from the present level of 171 million to 366 million—an increase of 214%.1 In developed countries, this increase in diabetic population would be around 42% and in developing countries, particularly in India, it is even higher; i.e. 150%.1 In India, the prevalence of diabetes mellitus in the urban population is around 12.1%, as reported by the national urban diabetes study2 conducted in six major cities. Studies have shown the prevalence of diabetes to be higher among the high-income groups (25.5%) as compared to low-income groups (12.6%).345 The assessment of socioeconomic status was based on income,67 education,27 occupation2 or caste6—which are not representative of the actual socioeconomic status. In the present study, however, the sample was stratified on socioeconomic scoring. This scoring was calculated on the basis of several parameters such as the residence being rented or owned, the number of rooms in the house, the highest educational status, the highest salary, the highest occupation, material possessions (cycle, TV, audio, car, etc.) and house/land value. To the best of our knowledge, this kind of comprehensive socioeconomic scoring has not been done before for prevalence studies on diabetic retinopathy in the general population.

Association of VEGF Gene Polymorphisms with Diabetic Retinopathy in a South Indian Cohort

Background: Polymorphisms in vascular endothelial growth factor (VEGF) gene have been associated with diabetic retinopathy (DR) in various populations. A promoter polymorphism and a 3′UTR variation are studied for association with DR. Materials and Methods: Type 2 diabetic patients with and without retinopathy were recruited. The −634C/G and 936C/T polymorphisms were genotyped by direct sequencing and their frequencies were analyzed using relevant statistical tests. Results: No significant association was observed between genotypes, alleles and haplotypes of −634C/G and 936C/T polymorphisms and DR or its severity. However, C(−634)G genotype was found to increase the risk for DR in patients with microalbuminuria (OR: 8.9, 95% CI: 1.4, 58.3). Conclusion: Our study broadly suggests lack of association of VEGF gene polymorphisms with DR.

Low frequency of myocilin mutations in Indian primary open-angle glaucoma patients.

Glaucoma is one of the major causes of blindness in the Indian population. Mutations in the myocilin (MYOC) gene have been reported in different populations. However, reports on MYOC mutations in Indian primary open‐angle glaucoma (POAG) patients and juvenile open‐angle glaucoma (JOAG) patients are sparse. We therefore screened 100 unrelated POAG/JOAG patients for MYOC mutations. Patients with POAG/JOAG were clinically diagnosed. Genomic DNA from such patients was collected and studied for MYOC mutations by direct sequencing. Nucleotide variations were compared with unrelated healthy controls by restriction enzyme digestion. Secondary structure prediction for the sequence variants was performed by Chou–Fasman method. A novel mutation in exon 1 (144 G→Α) resulting in Gln48His substitution was observed in 2% of the patients. Four other polymorphisms were also observed. The novel mutation was seen in four other affected family members of a JOAG patient. The novel mutation was found to alter the secondary structure in the glycosaminoglycan initiation site of the protein. MYOC mutations were found in 2% of the population studied. MYOC gene may not be playing a significant role in causing POAG in the Indian population.

Intron 4 VNTR of Endothelial Nitric Oxide Synthase (eNOS) Gene and Diabetic Retinopathy in Type 2 Patients in Southern India

A 27-bp variable number tandem repeat (VNTR) in intron 4 of endothelial nitric oxide synthase (eNOS) gene has been associated with the risk for developing diabetic retinopathy (DR) in various ethnic populations. Hundred and eighty seven patients with retinopathy (cases; DR+) and 188 patients without retinopathy (controls: DR−) from southern India who had type 2 diabetes mellitus (T2DM) for more than 10 years, were included in the study. We could neither find significant allelic association with clinical severity of DR nor with macular edema. Our results suggest lack of association of intron 4 VNTR of eNOS gene with DR in southern India.

Diabetic retinopathy: Validation study of ALR2, RAGE, iNOS and TNFB gene variants in a south Indian cohort

Purpose: We previously reported the association of the Z-2 allele of the promoter dinucleotide repeat in the Aldose reductase (ALR2) gene, the (CCTTT)15 allele in the promoter of inductible nitric oxide synthase (iNOS) gene, and the (GT)13 promoter polymorphism in the tumor necrosis factor β (TNFB) gene with an increased risk for diabetic retinopathy (DR), and the Gly82Ser polymorphism in the receptor for advanced glycation end products (RAGE) gene and the (GT)9 allele of the TNFB gene with low-risk for DR in a hospital-based self-reported type 2 diabetes mellitus (T2DM) patients. We have repeated the study in a population-based south Indian cohort to validate the same variations in these genes. Materials and Methods: Type 2 diabetic patients with and without retinopathy (DR+ and DR− respectively) were recruited. (CA)n repeat, Gly82Ser, (CCTTT)n repeat and (GT)n repeat in ALR2, RAGE, iNOS and TNFB genes respectively were genotyped and their frequencies were analyzed using the relevant statistical tests. Results: Different allelic associations were observed in the present study as compared to our previous reports. Z+2 allele of ALR2, 13-repeat genotype of iNOS, 15-repeat genotype of TNF-β, genes were associated with susceptibility to DR. Gly82Ser polymorphisms of the RAGE gene were not associated with DR in the present study. Conclusion: The present data show a difference in the association of variations in ALR2, iNOS and TNFB genes with DR, when compared to our previous reports; this could be attributed to differences between the study populations of the past and present report.

Diabetic retinopathy and IGF-1 gene polymorphic cytosine-adenine repeats in a Southern Indian cohort.

Background/Aims: Growth factors have been implicated in the pathogenesis of diabetic retinopathy (DR). IGF-1 is known to trigger a critical cascade of molecular events that initiate retinal angiogenesis. Increased vitreous IGF-1 levels have been correlated with the severity of ischemia-associated diabetic retinal neovascularization. In the present study, a cytosine-adenine (CA)n repeat in the promoter of the IGF-1 gene is studied for association with DR. Methods: A total of 127 patients with retinopathy (cases: DR+) and 81 patients without retinopathy (controls: DR–) who had type 2 diabetes were recruited for the study. Patients underwent detailed clinical examination and DR was graded based on stereoscopic digital fundus photographs. Frequencies of alleles and genotypes between the two groups were analyzed for significance using relevant statistical tests. (CA)17 and (CA)18 repeats were the more frequent alleles. Results: The frequency of the 18-repeat genotype was significantly higher in DR+ patients when compared to DR– patients and found to confer a 2.4 times (95% CI: 1.2–5.0) and 2.8 times (95% CI: 1.1–7.5) higher risk for developing DR and proliferative DR, respectively, when compared to <18-repeat genotypes. Conclusions: Our study suggests that the 18-repeat genotype is a susceptibility genotype for DR and its clinical severity in a Southern Indian cohort.

RPE65 gene: multiplex PCR and mutation screening in patients from India with retinal degenerative diseases

We used multiplex PCR followed by sequencing to screen for mutations in the 14 exons of theRPE65 gene in early-hildhood-onset autosomal recessive retinitis pigmentosa (arRP) and Leber’s congenital amaurosis (LCA) patients. The RPE65 protein is believed to play an important role in the metabolism of vitamin A in the visual cycle and mutations identified in the gene could have implications for vitamin A-based therapeutic intervention. We were able to identify a homozygous mutation (AAT → AAG) in exon 9 in an arRP patient and a heterozygous missense transversion (AAT → AAG) also in exon 9 of an LCA patient. We also identified a polymorphism in exon 10 (GAG → GAA) in an arRP as well as an LCA patient. Mutation screening would be greatly facilitated by multiplex PCR which could cut down costs, labour and time involved. The nucleotide changes observed in this study could bede novo. Though a larger study has been undertaken, from the preliminary results it appears that in India theRPE65 gene seems to be less involved in causation of LCA.

Genetics of Diabetic Retinopathy

Abstract Diabetic retinopathy (DR), a microvascular complication of diabetes in the retina, is one of the leading causes of adult blindness worldwide. Complex interplay of environmental and genetic factors has been known to contribute to its pathology. Variations in several genes have been found to be associated with risk for developing DR in different populations worldwide, which is discussed in this article. Identification of genetic variations underlining the disease would immensely lead to recognition of presymptomatic diabetic individuals susceptible to develop DR and help in planning appropriate clinical management and genetic counseling of patients.

Protein Kinase C β (PRKCB1) and pigment epithelium derived factor (PEDF) gene polymorphisms and Diabetic Retinopathy in a south Indian cohort

Purpose: Polymorphisms in protein kinase C β (PRKCB1) and pigment epithelium derived factor (PEDF) genes have been associated with diabetic nephropathy and retinopathy respectively. Association of promoter polymorphisms–1504C/T and–1440G/T in PRKCB1 gene and sequence variations in exon 4 of PEDF gene are studied with diabetic retinopathy (DR) in a south Indian population based cohort. Methods: Type 2 diabetic patients with and without retinopathy (DR+ and DR- respectively) were recruited. The promoter region of PRKCB1 gene and exon 4 of PEDF genes were sequenced by polymerase chain reaction based direct sequencing and their frequencies were analyzed using relevant statistical tests. Results: The genotype and alleles of the two promoter polymorphisms of PRKCB1 gene were uniformly distributed among DR+ and DR- and hence were not associated with the disease. The haplotypes were also not significantly associated with DR. A T130T polymorphism observed in the PEDF gene showed modest association with absence of diabetic retinopathy. Conclusion: Our results suggest lack of association of PRKCB1 gene promoter polymorphisms and moderate protective association of PEDF gene polymorphism with DR in the south Indian population.