HSPA5 and type 2 diabetes mellitus: In addition, restoration of PITPNA expression in islets of six individual T2D human donors (T2D-OE) resulted in the downregulation of steady-state levels of CHOP, PDI, and BiP/GRP78 (Supplementary Fig. 6b) as well as restoration of proinsulin expression (Supplementary Fig. 6c).