Association Between a Melatonin Receptor 1B Genetic Polymorphism and Its Protein Expression in Gestational Diabetes Mellitus

Aims: This study was conducted to investigate the relationship between a genetic polymorphism and the expression of melatonin receptor 1B (MTNR1B) in the placenta of Han Chinese women with gestational diabetes mellitus (GDM). Methods: In this study, 215 patients with GDM and 243 healthy controls were genotyped using direct sequencing for the MTNR1B single-nucleotide polymorphism rs10830963. The expression of MTNR1B in placenta was detected by immunohistochemistry and Western blotting. The association of rs10830963 with the expression of MTNR1B, plasma glucose, and insulin levels as well as blood lipid levels was investigated. Results: The genotype and allele frequencies of rs10830963 were significantly different between women with GDM and controls ( P < .05). Fasting blood glucose, fasting insulin, and homeostasis model assessment for insulin resistance in women with GDM with the GG and GC genotypes were significantly higher than those with the CC genotype ( P < .05). The expression level of MTNR1B in placenta was significantly higher in the GDM group than in the control group ( P < .05). The expression of MTNR1B was significantly higher in all participants with the GG and GC genotypes (1.31 [0.74]) than in pregnant women with the CC genotype (0.92 [0.52], P < .05). Conclusions: The genetic polymorphism rs10830963 in MTNR1B and its protein expression levels in placenta are associated with an increased risk of developing GDM. Furthermore, rs10830963 may tag a molecular mechanism leading to insulin resistance in Han Chinese women with GDM.