Loss of β-Cell Identity Occurs in Type 2 Diabetes and Is Associated With Islet Amyloid Deposits

Loss of pancreatic islet beta-cell mass and beta-cell dysfunction are central in the development of type 2 diabetes (T2DM). We recently showed that mature human insulin-containing beta-cells can convert into glucagon-containing alpha-cells ex vivo. This loss of beta-cell identity was characterized by the presence of beta-cell transcription factors (Nkx6.1, Pdx1) in glucagon(+) cells. Here, we investigated whether the loss of beta-cell identity also occurs in vivo, and whether it is related to the presence of (pre)diabetes in humans and nonhuman primates. We observed an eight times increased frequency of insulin(+) cells coexpressing glucagon in donors with diabetes. Up to 5% of the cells that were Nkx6.1(+) but insulin(-) coexpressed glucagon, which represents a five times increased frequency compared with the control group. This increase in bihormonal and Nkx6.1(+)glucagon(+)insulin(-) cells was also found in islets of diabetic macaques. The higher proportion of bihormonal cells and Nkx6.1(+)glucagon(+)insulin(-) cells in macaques and humans with diabetes was correlated with the presence and extent of islet amyloidosis. These data indicate that the loss of beta-cell identity occurs in T2DM and could contribute to the decrease of functional beta-cell mass. Maintenance of beta-cell identity is a potential novel strategy to preserve beta-cell function in diabetes.