Fasting serum glucose was associated with an intronic variant (MAF = 0.20; effect size 4.8%) in MTNR1B which encodes one of the melatonin receptors expressed in the retina and brain. Corroborating our findings, this variant (rs10830963) has been strongly associated with fasting glucose levels in adults [30], [31] and children [32]–[35]. Melatonin, the ligand to MTNR1B, has an inhibitory effect on insulin secretion resulting in elevated fasting glucose.
