A genetic study of retinopathy in south Indian type 2 (non-insulin-dependent) diabetic patients.
Genetic marker studies in diabetic retinopathy are controversial and frequently complicated by possible independent associations of Type 1 (insulin-dependent) diabetes mellitus with the markers so far analysed. We have looked for associations of candidate genes with retinopathy in South Indian Type 2 (non-insulin-dependent) diabetic patients; patients were subdivided into those with exudative maculopathy (n = 53), proliferative retinopathy (n = 40) and patients free from diabetic retinopathy with a minimum disease duration of 15 years (n = 45). DNA was extracted from blood samples and studied by Southern blot hybridisation techniques and the following probe enzyme combinations: HLA-DQB1; Taq 1, HLA-DQA1; Taq 1, HLA-DRA; Bgl II, insulin gene hypervariable region; Pvu II and the switch region of the immunoglobulin IgM heavy chain gene (S mu); Sac I. Differences in genotype distributions between the study groups were only detected with the S mu probe which detects polymorphism of both S mu and S alpha 1 (the switch region of IgA). Two alleles of S alpha 1 were detected sized 7.4 kilobase and 6.9 kilobase. The frequency of 6.9 kilobase homozygotes was lower in proliferative retinopathy (19%) compared to patients free from diabetic retinopathy (54%, p = 0.005) and exudative maculopathy (46%, p = 0.03). This data suggests that there is a genetic predisposition to proliferative retinopathy in Type 2 (non-insulin-dependent) diabetes of South Indian origin and that this is determined by polymorphism of the heavy chain immunoglobulin genes located on chromosome 14.
Medical Unit, Royal London Hospital, Whitechapel, UK.
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Hawrami
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Mohan
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Mohan
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Hitman
D000368:Aged; D000483:Alleles; D002874:Chromosome Mapping; D003924:Diabetes Mellitus, Type 2 / Q000150:complications* / Q000235:genetics / Q000276:immunology; D003930:Diabetic Retinopathy / Q000235:genetics* / Q000276:immunology; D005260:Female; D006683:HLA-DQ Antigens / Q000235:genetics / Q000276:immunology; D059866:HLA-DQ beta-Chains; D006801:Humans; D007142:Immunoglobulin gamma-Chains / Q000235:genetics / Q000276:immunology; D007194:India; D007328:Insulin / Q000235:genetics; D008297:Male; D008875:Middle Aged; D011110:Polymorphism, Genetic / Q000235:genetics / Q000276:immunology; D012150:Polymorphism, Restriction Fragment Length
D006683:HLA-DQ Antigens; D059866:HLA-DQ beta-Chains; C053186:HLA-DQ2 antigen; C057615:HLA-DQbeta antigen; D007142:Immunoglobulin gamma-Chains; D007328:Insulin