The Use of Glutamic Acid Decarboxylase (GAD) and Gamma-Amino Butyric Acid (GABA) in the Treatment of Type I Diabetes

The primary defect in autoimmune Type I Diabetes Mellitus (T1DM) involves the infiltration of the pancreatic islet cells by T-lymphocytes, macrophages, and other immune cells, and consequent loss of beta cells. At the onset of T1DM more than 70% of the beta cells are destroyed, whereas the residual beta cells most likely represent the only reservoir for the potential regeneration of the islet beta cell mass. A series of immunological abnormalities have been reported in those with T1DM including, but not limited to, the production of autoantibodies (i.e., glutamic acid decarboxylase (GAD-65), tyrosine phosphatase-related islet antigen 2 (IA2), Zinc Transporter 8 (ZnT8A), or insulin (IAA) as well as alterations in the capacity of regulatory T cells (Treg) to suppress the action of effector T cells (Teff); the latter population thought as playing a key role in the immune destructive process. Therefore, a vast majority of studies attempting to prevent or reverse the disease have focused on immune suppression. While some of these studies have shown limited promise, many has side effects which were significant enough that one must question the value of short term benefits associated with utilizing these drugs. GABA is a naturally occurring substance in physiology and has the potential to locally reduce inflammation and protect pancreatic beta cells from auto-immune destruction. GABA, synthesized from glutamate by GAD, is a well known neurotransmitter in the CNS and acts mainly through the GABAA receptor (GABAAR). GABA is locally produced by the pancreatic beta cells. GABAARs are also expressed in various immune cells, including T-cells, peripheral blood mononuclear cells, and are known to exert immune-inhibitory effects. BABA appears to play multiple roles in the pancreas. GABA promotes beta-cell growth and survival, and GABA can also act on the GABA(A) receptors in the pancreatic alpha cells, in so doing suppressing glucagon secretion, and GABA suppresses inflammation and increases regulatory T-cell numbers. Based on the aforementioned information, we envisage that administering GABA to those with new onset T1DM may preserve or increase residual insulin production, suppress glucagon release, and decrease inflammation surrounding the pancreas. With this, GABA may prolong the beta-cell life after diagnosis. Combining with GAD-alum injections, which aim to halt the autoimmune attack by inducing tolerance thereby saving residual insulin production, may improve glycemic control even more and significantly decrease the risk of hypoglycemia and long-term complications in the future.