Adult β-cell mass expansion in response to increased insulin demand, such as that generated by insulin resistance, may take
place based on preexisting β-cells—by enhanced β-cell replication and/or increased individual β-cell size—or new β-cells could
be generated from other cell sources, such as neogenesis from ductal cells or transdifferentiation from acinar cells or α-cells.
In diabetic patients, β-cell mass reduction can result from increased apoptotic cell death, and recently β-cell dedifferentiation
and conversion into other endocrine non–β-cells of the islets has been described in diabetic mice.