AKT1 and type 1 diabetes mellitus: In contrast, in T1DM, β-cell destruction by autoreactive immune cells causes reduced β-cell mass; in T2DM, diabetogenic insults result in major changes in pathways (PI3K-AKT/PKB, Ras/Raf/ERK, cell cycle regulators) that impair the ability of β-cells to proliferate.