GLP1R and diabetes mellitus: While basic research efforts to better understand the intricate mechanisms regulating GLP-1 receptor function are being aided by advancements in GPCR molecular and structural biology (see review by Willard and Sloop in this issue of Experimental Diabetes Research), the field awaits determination of a high resolution crystal structure of a class B1 GPCR for use as a template to facilitate rational drug design for these difficult targets.