Against this background, it is intriguing that Tuomi et al. showed that a common (about 30%) human type 2 diabetes (T2D) risk variant of the melatonin receptor 1B gene affects insulin release [13]; this study demonstrated that melatonin treatment inhibits insulin secretion, with at-risk carriers exhibiting higher glucose levels. This evidence concerns the gene MTNR1B and type 2 diabetes mellitus.