SNCA and Parkinson disease: However, a study by Xie et al. reported that 1-acetyl-6,7-dihydroxyl-1,2,3,4-tetrahydroisoquinoline (ADTIQ) levels were elevated in both STZ-induced diabetic rats and transgenic α-synuclein gene PD mice model and this elevation was directly related to the accumulation of α-synuclein.