Glutamic acid decarboxylase [GAD65] and thyroid autoantibodies in Omani patients with type 2 diabetes

ABSTRACT

Autoimmunity is a common feature in type 1 diabetes mellitus [DM]. Little is known of the role of autoimmunity in type 2 diabetes. Antibodies to glutamic acid decarboxylase [GAD65] and thyroid antigens have been reported with various frequencies in diabetic patients. In this study, we investigated the prevalence and association of antibodies to GAD65, anti-thyroglobulin [A-TG-A], anti-thyroid microsomal [ATMA] antibodies, haemoglobin A[1c] [HbA[1c]] and fasting serum C-peptide in Omani patients with type 2 diabetes mellitus. We studied 100 Omani patients with type 2 diabetes for the presence of serum antibodies to GAD65, A-TG-A and ATMA by the use of commercially available kits. Results were compared with those from fifty patients with type 1 diabetes mellitus [DM] and fifty unaffected individuals who were used as controls. Results showed that type 2 DM had significantly high positivity levels [24%] of anti-GAD65 antibodies than the control group [4% - p < 0.05] though less than that found in type 1 DM [38%]. GAD65 antibodies were more commonly found in older females [> 40 years] with type 2 diabetes [p < 0.05]. A higher prevalence of ATMA was noted in both type 2 and type 1 diabetes [20 and 26% respectively] compared to the levels in the control group [8%]. There was a low prevalence and little difference in A-TG-A values among the three groups studied [9%, 14% and 4%]. Both A-TG-A and ATMA were more often expressed in older females with type 2 diabetes. HbA[1c] did not differ between groups with the duration of disease less or more than three years. When the same groups were tested for fasting serum C-pepticle, those with disease of more than three years duration had significantly higher prevalence [p < 0.05] as compared to those less than three years. This study confirms the presence and association of thyroid and GAD65 antibodies in some Omani patients with clinical diagnosis of type 2 DM