Association of the rs10830963 polymorphism in melatonin receptor type 1B (MTNR1B) with metabolic response after weight loss secondary to a hypocaloric diet based in Mediterranean style

Background & aims: Some genetic variants within MTNR1B were related with fasting glucose levels or the increased prevalence of diabetes mellitus and obesity. The aims of the present investigation were to determine the influence of rs10830963 MTNR1B variant in relation to body weight loss, insulin resistance and adipokine levels in response to a hypocaloric diet with Mediterranean pattern. Methods: A Caucasian population of 80 obese patients was studied before and after 12 weeks on a hypocaloric diet. Body weight, fat mass, waist circumference, blood pressure, fasting blood glucose, C-reactive protein (CRP), insulin concentration, insulin resistance (HOMA-IR), lipoprotein levels and adipocytokines levels (leptin, adiponectin and resistin) were measured. Genotype of MTNR1B gene single nucleotide polymorphism (rs10830963) was evaluated. Results: In total, 44 patients (55%) had the genotype CC, 27 patients CG (33.8%) and 9 patients GG (11.2%). With the dietary intervention body mass index, weight, fat mass, systolic blood pressure, leptin levels and waist circumference decreased in both groups. There were no significant differences between gender groups on the reported effects in each genotype group. However, the improvement of anthropometric parameters was higher in subjects with CC genotype than (GC + GG) genotype. After dietary intervention and in males with CC genotype, insulin levels (-5.3 +/- 4.8 Ul/L vs 1.2 +/- 4.1 UI/L; p < 0.05) and HOMA-IR (-1.4 +/- 2.1 units vs 0.4 +/- 2.0 units; p < 0.05) decreased. In the group of females with CC genotype, insulin levels (-3.5 +/- 2.1 Ul/L vs. -1.4 +/- 2.2 Ul/L: p < 0.05) and HOMA-IR (-1.4 +/- 1.2 units vs. -0.1 +/- 1.3 units: p < 0.05) decreased, too. However, these parameters remained unchanged in (GC + GG) group. Fasting glucose levels were higher in patients in (GC + GG). Conclusions: This study showed the association of rs10830963 MTNR1B single nucleotide polymorphism with body weight loss and changes in fasting insulin levels and HOMA-IR in obese subjects. (C) 2017 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.