TCF7L2 and diabetes mellitus: Our functional characterization of “T-3” in hiPSC-derived astrocytes revealed a role in the regulation of the expression of genes involved in diabetes and insulin signaling pathways (Fig. 3), results which suggest that in the CNS TCF7L2, in addition to its role in the liver [32–34], pancreas [35, 36], and gut [37], might also contribute to metabolic regulation.