PTPRD and schizophrenia: Nevertheless, some candidate genes associated with T2D and schizophrenia have been proposed, including phosphatidylinositol 3-kinase regulatory subunit alpha (PIK31), an upstream activator of protein kinase B (AKT) signaling; calcium-dependent mediators such as protein kinase C alpha (PRKCA) and protein kinase, DNA-activated, catalytic subunit (PRKAC); non-receptor type 11 protein tyrosine phosphatase (PTPN11) [33], which is involved in adipokine signaling; protein tyrosine phosphatase receptor type D (PTPRD) [34]; and low-density lipoprotein receptor-related protein (LRP4) [35].