Validation of a Genome-Wide Polygenic Score for Coronary Artery Disease in South Asians.

BACKGROUND: Genome-wide polygenic scores (GPS) integrate information from many common DNA variants into a single number. Because rates of coronary artery disease (CAD) are substantially higher among South Asians, a GPS to identify high-risk individuals may be particularly useful in this population. OBJECTIVES: This analysis used summary statistics from a prior genome-wide association study to derive a new GPSCAD for South Asians. METHODS: This GPSCAD was validated in 7,244 South Asian UK Biobank participants and tested in 491 individuals from a case-control study in Bangladesh. Next, a static ancestry and GPSCAD reference distribution was built using whole-genome sequencing from 1,522 Indian individuals, and a framework was tested for projecting individuals onto this static ancestry and GPSCAD reference distribution using 1,800 CAD cases and 1,163 control subjects newly recruited in India. RESULTS: The GPSCAD, containing 6,630,150 common DNA variants, had an odds ratio (OR) per SD of 1.58 in South Asian UK Biobank participants and 1.60 in the Bangladeshi study (p < 0.001 for each). Next, individuals of the Indian case-control study were projected onto static reference distributions, observing an OR/SD of 1.66 (p < 0.001). Compared with the middle quintile, risk for CAD was most pronounced for those in the top 5% of the GPSCAD distribution-ORs of 4.16, 2.46, and 3.22 in the South Asian UK Biobank, Bangladeshi, and Indian studies, respectively (p < 0.05 for each). CONCLUSIONS: The new GPSCAD has been developed and tested using 3 distinct South Asian studies, and provides a generalizable framework for ancestry-specific GPS assessment.

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 ß (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-ß, 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.

Anemia and diabetic retinopathy in type 2 diabetes mellitus.

OBJECTIVES: To estimate the prevalence of anemia in persons with type 2 diabetes mellitus and its role as a risk factor for the presence and the severity of diabetic retinopathy, in a population based study. METHODS: In all 5999 subjects from the general population aged > or =40 years were enumerated for the study. A total of 1414 persons identified with diabetes underwent comprehensive eye examination, and stereoscopic digital fundus photography was used for diabetic retinopathy grading. All patients underwent hemoglobin estimation for detection of anemia. Univariate and multivariate analyses were done to determine the independent risk factors for anemia. RESULTS: The prevalence of anemia (Hb <12 g/dl in women and <13 g/dl in men) was 12.3%. Between 40 and 49 years of age, prevalence of anemia was higher in women than in men (26.4 % vs 10.3%). Men with anemia, and not women, had 2 times the risk of developing diabetic retinopathy. Multivariate analysis revealed independent predictors for anemia: age group more than 69 years OR 2.49 (95% CI 1.44-4.30), duration of diabetes of more than 5 years OR 1.56 (1.09-2.69) and the presence of diabetic retinopathy OR 1.82 (95% CI 1.22-2.69). CONCLUSION: Every tenth individual in a population of diabetes mellitus could be anemic. Identifying and treating anemia would make a great impact in managing microvascular complications such as diabetic retinopathy.

Protein kinase C beta (PRKCB1) and pigment epithelium derived factor (PEDF) gene polymorphisms and diabetic retinopathy in a south Indian cohort.

PURPOSE: Polymorphisms in protein kinase C beta (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.

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.

Identification of a novel splice-site mutation in the Lebercilin (LCA5) gene causing Leber congenital amaurosis.

PURPOSE: Leber congenital amaurosis (LCA) is one of the most common causes of hereditary blindness in infants. To date, mutations in 13 known genes and at two other loci have been implicated in LCA causation. An examination of the known genes highlights several processes which, when defective, cause LCA, including photoreceptor development and maintenance, phototransduction, vitamin A metabolism, and protein trafficking. In addition, it has been known for some time that defects in sensory cilia can cause syndromes involving hereditary blindness. More recently evidence has come to light that non-syndromic LCA can also be a "ciliopathy." METHODS: Here we present a homozygosity mapping analysis in a consanguineous sibship that led to the identification of a mutation in the recently discovered LCA5 gene. Homozygosity mapping was done using Affymetrix 10K Xba I Gene Chip and a 24.5cM region on chromosome 6 (6q12- q16.3) was identified to be significantly homozygous. The LCA5 gene on this region was sequenced and cDNA sequencing also done to characterize the mutation. RESULTS: A c.955G>A missense mutation in the last base of exon 6 causing disruption of the splice donor site was identified in both the affected sibs. Since there is a second consensus splice donor sequence 5 bp into the adjacent intron, this mutation results in a transcript with a 5 bp insertion of intronic sequence, leading to a frameshift and premature truncation. CONCLUSIONS: We report a missense mutation functionally altering the splice donor site and leading to a truncated protein. This is the second report of LCA5 mutations causing LCA. It may also be significant that one affected child died at eleven months of age due to asphyxia during sleep. To date the only phenotype unambiguously associated with mutations in this gene is LCA. However the LCA5 gene is known to be expressed in nasopharynx, trachea and lungs and was originally identified in the proteome of bronchial epithelium ciliary axonemes. The cause of death in this child may therefore imply that LCA5 mutations can in fact cause a wider spectrum of phenotypes including respiratory disease.

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.

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.