PTPA and type 1 diabetes mellitus: However, although several investigators have observed a decrease only in the expression of PP2A in T2DM mice brains (Schubert et al., 2003; Li et al., 2012a), we (Planel et al., 2007b), and others (Clodfelder-Miller et al., 2006; Qu et al., 2011; Jung et al., 2013), have reported that PP2A activity is inhibited in both T1DM and T2DM animal models.