GAD2 and type 1 diabetes mellitus: In addition to the already mentioned role of GAD65 autoimmunity, a recent study has reported that a 15 amino acid peptide from the Gram-negative anaerobic bacterium Parabacteroides distasonis, a normal human gut commensal, mimics an epitope in the B-chain of insulin and behaves as a molecular trigger of T1DM pathogenesis (Girdhar et al. 2022).