HDAC9 and type 2 diabetes mellitus: Specifically, the expression of HDAC7, a class IIa HDAC, is increased in pancreatic islets from patients with T2D (Daneshpajooh et al., 2017) and over-expression of Hdac7 in rat islets and clonal β-cells reduces insulin content and increases apoptosis, leading to impaired GSIS of β-cells (Daneshpajooh et al., 2017).