GAD2 and type 1 diabetes mellitus: Also, when comparing the metabolome of anti-GAD65 antibody positive and anti-GAD65 antibody negative T1D patients (52 positive versus 49 negative), metabolites related to tryptophan metabolism were found to be significantly different, including 3-hydroxyanthranilic acid, L-phenylalanine, and L-kynurenine, as they were found to be reduced in patients with anti-GAD65 autoantibodies compared to patients with negative anti-GAD65 antibodies.