Our new findings that VPA improves insulin secretion via elevated Sox5 expression, restores the T2D-associated module and increases glucose-stimulated insulin secretion in vivo raise the exciting possibility that VPA and other HDAC inhibitors could be a potential means to treat defective insulin secretion in T2D by counteracting an immature β-cell state. This evidence concerns the gene HDAC9 and type 2 diabetes mellitus.