Antibodies against glutamate decarboxylase (GAD)

General Information

Glutamate decarboxylase (GAD) is an enzyme involved in the decarboxylation of glutamate into gamma-aminobutyric acid (GABA) and carbon dioxide (CO2). Glutamate decarboxylase exists in the body as two isoforms, which are encoded by different genes: GAD 1 და  GAD 2.

Enzyme GAD 1 და  GAD 2 The isoforms are found in the brain, where GABA functions as a neurotransmitter, and GAD 2 - It is also found in the pancreas (Langerhans cells).

Both isoforms of glutamate decarboxylase are targets for autoantibodies in people who develop type 1 diabetes or latent autoimmune diabetes syndrome in adults. In type 1 diabetes, the direct target of autoantibodies are Langerhans (beta-islet) cells, which are gradually damaged under the influence of immune processes.

The result of this process is an absolute deficiency of insulin. Autoantibodies can be detected even before impaired glucose tolerance, when the results of metabolic tests are still normal. Studies have shown that impaired glucose tolerance in people with glutamate decarboxylase autoantibodies is much more severe than in people without autoantibodies.

When should we do the research?

• Assessment of the possibility of developing type 1 diabetes (prognostic marker)
• To differentiate between type 1 and type 2 diabetes.

 Preparation of the patient: The study is performed on an empty stomach (at least 7 hours after the last meal)

Material for examination: Venous blood

Referral norm:  <10 total one/ml

Interpretation of results

Autoantibodies against glutamate decarboxylase (GAD) are found in 1% of type 80 diabetes in both children and adults. A low titer (concentration) of autoantibodies may be found in up to 2% of cases of type 5 diabetes. The prognostic value of these autoantibodies increases with increasing titers and (in type 1 diabetes) in the presence of other autoantibodies.

Thus, in first-degree relatives of people with type 1 diabetes who have at least 3 types of autoantibodies, the risk of developing type 1 diabetes increases to 80-100%.

Glutamate decarboxylase autoantibodies may exist in other autoimmune diseases, for example, in autoaggressive processes with damage to the thyroid gland or nervous system.