PTPN1 and Parkinson disease: Other biomarkers including hepatocyte nuclear factor 4 alpha (HNF4A), PTBP1 and PTPN1 have been implicated in glucose metabolism and insulin regulation, biological processes that have been extensively associated with the pathogenesis of PD (Knoch et al., 2006; Santiago and Potashkin, 2013b, 2015a).