ASP-57 AND ARG-52 OF THE HLA-DQ AS GENETIC-MARKERS FOR INSULIN-DEPENDENT DIABETES-MELLITUS IN SAUDIS

Objectives: To investigate the significance of Asp 57 and Arg 52 in HL A DQB- and A chains in the development of insulin-dependent diabetes m ellitus (IDDM). Design: This study was incorporated in a national stud y of the epidemiology of diabetes mellitus in the Saudi Arab populatio n where analysis for Asp 57 and Arg 52 of the HLA DQ was conducted on samples from patients suffering from IDDM. Subjects: Subjects studied were 38 patients diagnosed as IDDM using the criteria published by the World Health Organization and 37 healthy non-diabetic individuals, se lected as controls. Methods: The DNA was extracted from the buffy coat and subjected to polymerase chain reaction to amplify the DNA region encoding the HLA DQB- and A-chains. Dot blot analysis of the amplified material was carried out using allele specific oligonucleotide probes to identify the presence of Asp or non-Asp codons at position 57 and Arg and non-Arg codons at position 52 of the HLA DQB and A, respective ly. Results: The results demonstrated a significantly higher gene freq uency of non-asp at position 57 (60.5%) and of Arg 52 (46.1%) in the I DDM patients compared with the normal group. On the other hand, the ge ne frequency of Asp 57 and non-Arg 52 were higher in the normal non-di abetic individuals compared with the IDDM group, though both non-Asp 5 7 (43.2%) and Arg 52 (23.0%) were found in the normal non-diabetic con trols. Conclusion: These results suggest that the absence of aspartic acid at position 57 of the HLA DQB-chain (i.e. non-Asp 57), and the pr esence of arginine in position 52 of the HLA DQA-chain (i.e. Arg 52) c an be useful, but not confirmatory markers, for susceptibility to IDDM .