Rare MTNR1B variants impairing melatonin receptor 1B function contribute to type 2 diabetes.
Level 4 - case-series / case-control
Case-control genetic association study combined with functional laboratory assays
PubMed 22286214 · doi:10.1038/ng.1053
What was done
Exon resequencing of MTNR1B was performed in 7,632 European participants (2,186 with type 2 diabetes). Functional effects of 40 identified nonsynonymous variants were evaluated in vitro for melatonin binding and signaling. Four complete loss-of-function variants were subsequently genotyped in an additional 11,854 individuals (total 8,153 cases and 10,100 controls).
What was found
The 40 nonsynonymous variants were associated with type 2 diabetes (OR = 3.31, 95% CI = 1.78-6.18, P = 1.64 × 10⁻⁴). In functional assays, 14 variants were non-functional and 4 showed complete loss of binding and signaling. Very rare partial- or total-loss-of-function variants contributed strongly to diabetes risk (OR = 5.67, 95% CI = 2.17-14.82, P = 4.09 × 10⁻⁴), whereas neutral variants did not. In the replication cohort of 8,153 cases and 10,100 controls, the four complete loss-of-function variants remained significantly associated with diabetes (OR = 3.88, 95% CI = 1.49-10.07, P = 5.37 × 10⁻³).
Why it matters
This study demonstrates that rare coding variants directly impairing melatonin receptor 1B function confer substantial risk for type 2 diabetes, establishing a direct functional mechanism.
Limits
The study was restricted to European cohorts, limiting generalizability. Due to the extreme rarity of the variants (minor allele frequency <0.1%), individual variant effect estimates had wide confidence intervals. Non-genetic factors such as sleep patterns and lifestyle were not described in the abstract.
Cited by
- supports Genome-wide association studies identified mutations in the melatonin receptor associated with obesity and type 2 diabetes risk.