GAD1 and type 2 diabetes mellitus: Furthermore, the representative “T2DM cohorts” tested positive for one or more auto-antibodies, including glutamate decarboxylase (GAD), islet cytoplasmic antibodies (ICA), insulinoma-associated protein 2 (IA-2A), or zinc transporter 8 (ZnT8) [77,78,79,80,81,82].