Does the MTNR1B rs10830963 G allele worsen glucose handling during late circadian schedules?

The genetic variant rs10830963 in the MTNR1B gene plays a critical role in linking circadian rhythms with metabolic health by directly altering how pancreatic cells respond to melatonin.

Molecular and cellular mechanisms

• Receptor overexpression: The rs10830963 G allele creates an active NEUROD1 transcription factor binding site within an enhancer region, driving elevated expression of the Gi-coupled MTNR1B receptor on pancreatic $\beta$-cells.
• Inhibited insulin release: Heightened melatonin signaling via this pathway directly blocks cAMP formation, which normally amplifies glucose-stimulated insulin release. This cellular inhibition blunts and delays first-phase insulin secretion, consistently elevating fasting plasma glucose by approximately 0.07 mmol/L per G allele.

Circadian alignment and clinical implications

• Impact of late eating: Consuming meals during late circadian schedules—when endogenous melatonin levels are naturally elevated—selectively impairs glucose handling in G-allele carriers, leading to a significantly higher postprandial glucose area under the curve (AUC).
• Melatonin sensitivity: Controlled laboratory trials demonstrate that melatonin exposure reduces first-phase insulin secretion by approximately 40% and increases glucose AUC specifically in carriers of the risk allele compared to non-carriers.

Bottom line

• Bottom line: Carriers of the MTNR1B rs10830963 G allele possess a genetically driven sensitivity to melatonin-mediated insulin suppression; avoiding food intake during high-melatonin windows (such as late-night eating) is a crucial, mechanism-aligned strategy to optimize glucose tolerance.