GAD1 and type 2 diabetes mellitus: On the other hand, a positive family history of type 1 diabetes increases the risk to develop type 2 diabetes [24], and is associated with earlier onset of type 2 diabetes, positivity for GAD antibodies (GADA), a more severe insulin deficiency, higher frequency of the HLA-DQB1*03:02/X genotype, which predisposes to type 1 diabetes, and lower frequencies of hypertension and cardiovascular disease, as well as lower BMI and C-peptide levels [25–27].