ANTI-GAD AUTOANTIBODY LEVELS IN TYPE II DIABETES PATIENTS AND THEIR FIRST DEGREE RELATIVES

Glutamic Acid Decarboxylase(GAD) catalyses the conversion of glutamic acid to Gama amino Butyric Acid(GABA) which is one of the major inhibitory neurotransmitters in central nervous system. GAD has two isoforms with molecular weights of 65 Kda(GAD 65) and 67 Kda (GAD 67). GAD 65 gene is located on chromosome 10 and expressed in β-cells of pancrease. The presence of high concentrations of Anti-GAD Antibodies(GADA) in serum of patients with IDDM is evident. Evaluation of GADA levels in individuals with NIDDM and their first degree relatives can also be used as a predictor of late insuline dependency. High concentrations of glucose induce the production of GAD 65 in β-cells which is associated with an increase in GAD 65 gene expression. It has been shown that patients with NIDDM may produce higher levels of GADA and after short period of time developing IDDM. In the present study anti-GAD levels were determined and compared in 50 type II Iranian diabetic patients, in 32 of their first degree relatives and in 56 healthy subjects. The evaluation of GADA levels were carried out by the use of ELISA method. The mean level of anti-GAD in the healthy subjects was 6.64±7.01ng/ml, in the patients was 10.76±13.59ng/ml and in their first degree relatives was 19.71±32.1ng/ml. In regard to the cut off, 18% of patients had seropositive anti-GAD and 21.9% of their first degree relatives had seropositive anti-GAD but all of the healthy subjects had seronegative anti-GAD. The frequencies of anti-GAD positivity in patients and their first degree relatives compared with that of healthy subjects were significantly higher(P<0.001 and P=0.001 respectively). It can be concluded that the determination of anti-GAD in healthy subjects and their first degree relatives of type II diabetic patients can be used to predict the development of diabetes and insuline dependency.