Is the common variant rs10830963 in the Melatonin Receptor 1B gene influencing the associations between depressive symptoms and glycemic traits?

BackgroundPrevious studies have identified a bidirectional association between depression and type 2 diabetes (T2D). It has been suggested that these disorders may share common underlying biological determinants. Because the... [ view full abstract ]

Background
Previous studies have identified a bidirectional association between depression and type 2 diabetes (T2D). It has been suggested that these disorders may share common underlying biological determinants. Because the neurohormone melatonin, which plays a key role in circadian regulation, has been implicated in both depression and T2D, we examined if a common variant rs10830963 in the Melatonin Receptor 1B (MTNR1B) gene influenced the association between depressive symptoms and glycemic traits.
Methods
The Prevalence, Prediction and Prevention of Diabetes (PPP-Botnia) is a population-based study of 5,208 participants aged 18 to 78 years residing in Western Finland; 5,177 of whom underwent an oral glucose tolerance test (OGTT). Of them, 5,040 answered a questionnaire (Mental Health Inventory on depressive symptoms), and 4,905 participants were genotyped for the rs10830963. The Helsinki Birth Cohort Study (HBCS) with 1,576 individuals was used for replication. HBCS had identical phenotypes and participants were genotyped for the rs10830963.
Results
In the discovery cohort depressive symptoms were associated with fasting insulin and 30 min glucose during the OGTT, Homeostasis-Model-Assessment-Insulin-Resistance, Insulin-Sensitivity-Index and Disposition-Index in a genotype-dependent manner in insulin-resistant individuals. The same associations remained significant in insulin-resistant individuals who got tested during the dark season. In the replication cohort depressive symptoms were not associated with glycemic traits in a genotype-dependent manner in insulin-resistant individuals. However, depressive symptoms were associated with Insulin-Sensitivity-Index and AUC and 120 min insulin in a genotype-dependent manner in insulin-resistant individuals who got tested during the dark season.
Conclusions
Our findings support the view that the melatonergic system contributes to the known comorbidity between depression and T2D.