[ survey on the presence of anti-GAD in type 1 diabetic patients and their first-degree relatives in comparison with healthy individuals]

ABSTRACT

Glutamic acid decarboxylase [GAD] catalyzes the conversion of glutamic acid to gamma-aminobutyric acid [GABA]. GAD65 isozyme is present in the pancreatic beta-cells. In the prediabetes period and during the beta-cell destruction, GAD is released as an autoantigen and anti-GAD autoantibodies appear in serum. Islet Cell Autoantibodies[ICAs] including anti-GAD are detectable in serum of diabetic patients up to 10 years before appearance of diabetes symptoms. This is an important predictive marker for diagnosis of prediabetic patients, especially in the first-degree relatives of diabetic patients for genetic factors. Anti-GAD is an important marker for detection of beta-cells destruction. The patients with high titers of anti-GAD have a worse disease prognosis and are in greater need of insulin injections. This survey is a case-control study aimed at detection of anti-GAD presence in sera of type 1 diabetic patients and their first-degree relatives and comparison with healthy individuals. Fifty type 1 diabetic patients with mean age of 12.24 +/- 6.2 years and mean disease duration of 34.5 +/- 8.4 months, 35 first-degree relatives and 50 normal individuals without familial diabetes were included in the study; all the individuals were chosen by a random sampling method. The values of fasting blood sugar were determined in first-degree relatives and controls and all were found to be normal. The values of anti-GAD were determined by ELISA method. Median values of anti-GAD in cases and controls were 28, [range 5-2700] ng/ml and 2, [0-10] ng/ml, respectively. The anti-GAD titers were significantly higher in patients than in normal individuals and relatives together [p<0.0001]. Median value of anti-GAD in first-degree relatives was 7, [0-950] ng/ml. There was a significant statistical difference between anti-GAD titers in first-degree relatives and controls, [p<0.01]. There was a significant difference between mean value of age and diabetes duration in anti-GAD positive and anti-GAD negative patients, [p<0.05]. There was a negative correlation between anti-GAD and age, diabetes duration, disease beginning age of patients, [r=-0.155,-0.158,-0.036], respectively. By increasing of anti-GAD in diabetic patients and their first-degree relatives it may be concluded that measurement of anti-GAD is an important and beneficial tool for detection and diagnosis of prediabetic and diabetic patients