Influence of maternal educational level on the association between the rs3809508 neuromedin B gene polymorphism and the risk of obesity in the HELENA study
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OBJECTIVE: Neuromedin B (NMB) is a bombesin-like peptide, which inhibits food intake and modulates stress-related behaviour. An NMB gene polymorphism (P73T) has been earlier associated with obesity and abnormal eating behaviour in adults. METHODS: The association between four NMB polymorphisms and obesity-related phenotypes was investigated in the Healthy Lifestyle in Europe by Nutrition in Adolescence cross-sectional study (n=1144, 12-17-year-old European adolescents). This population was genotyped for the NMB rs1107179, rs17598561, rs3809508 and rs1051168 (P73T) polymorphisms. Obesity was defined according to Cole et al. (BMJ 2000; 320:1240-1243) criteria; eating behaviour was assessed by the Eating Behaviour and Weight Problems Inventory for Children (EWI-C) and the food choices and preferences questionnaires. Familial socioeconomic status (SES) was assessed through the parents' educational level. RESULTS: Only the genotype distribution of rs3809508 differed according to obesity status, as the TT genotype was more frequent in obese than in non-obese adolescents (8.6% vs 3.1%, P=0.05; adjusted odds ratio for obesity (95% confidence interval): 2.85 (1.11-7.31), P=0.03). Moreover, TT subjects had higher body mass index (22.8+/-4.4 kg m(-2) vs 21.3+/-3.7 kg m(-2), P=0.02), waist circumference (75.8+/-9.7 cm vs 72.2+/-9.3 cm, P=0.006), waist-to-hip ratio (0.84+/-0.14 vs 0.79+/-0.07, P<0.0001) and waist-to-height ratio (0.47+/-0.06 vs 0.44+/-0.55, P=0.002) than C allele carriers. The effects of this single nucleotide polymorphism on all anthropometric values were influenced by the maternal SES, in that a low maternal educational level aggravated the phenotype of adolescents carrying the TT genotype (interactions: P<0.02). No association with EWI-C scores was found, although sweet craving was a more frequent cause of between-meal food intake in TT subjects than in C allele carriers (24.3% vs 9.2%, P=0.01). CONCLUSION: In European adolescents, the TT genotype of the NMB rs3809508 polymorphism was associated with a higher risk of obesity. Moreover, the effects of this polymorphism on anthropometric values were influenced by the maternal educational level.
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