GRB14 and type 2 diabetes mellitus: Genes with the largest expression differences between twins with T2D and co-twins without T2D (P < 0.05, same direction in ≥ 15/19 twin pairs and absolute difference ≥ 20%) are presented in Fig. 3A and include genes with known functions in muscle and/or glucose/lipid metabolism such as ANGPTL4, NR4A2 (NURR1), and GRB14 [26–28].