SLC37A4 and disorder of glycogen metabolism: Type I glycogen storage disease (GSD-I), also known as von Gierke disease, was originally considered a group of four disorders that correlated to the loss of four different protein activities: GSD-1a, the glucose-6-phosphatase-α (G6Pase-α or G6PC) activity; GSD-Ib, the glucose-6-phosphate transporter (G6PT or SLC37A4) activity; GSD-Ic, a putative phosphate transporter activity; and GSD-Id, a putative glucose transporter activity (Chou et al., 2002; Chou et al., 2010a; Chou et al., 2010b; Chou et al., 2015).