[Effect of genetic polymorphisms on change in body mass index and obesity status during childhood].

Objective: The present study aimed to prospectively validate whether the single nucleotide polymorphisms (SNPs) in obesity-related genes were associated with change in body mass index (BMI) and obesity status during childhood. Methods: Based on the Beijing Child and Adolescent Metabolic Syndrome study (BCAMS), which was initiated between April and October in 2004, we conducted a follow-up study among 1 624 children aged 6 to 11 years old with genetic data in December 2010. A total of 777 children (246 obese and 531 non-obese) were reassessed for BMI. Z-score of BMI was used to standardize for age and sex. The changes in BMI Z-score during follow up were calcnlated SNPs were genotyped by quantitative Real-time PCR (rs9939609, rs6499640, rs7138803, rs1805081, rs17782313, rs6265, rs10938397, rs6235, rs29941, rs2844479, rs10913469 and rs4788102). Overweight and obesity were diagnosed by the age-and sex-specific BMI cutoffs recommended by the International Obesity Task Force. A multilocus genetic risk score for BMI was calculated as the simple sum of alleles of all the SNPs associated with BMI. Linear regression models and logistic regression models were performed to assess the associations of change in BMI Z-score and obese status with genotypes (assuming an additive model), respectively. Results: During 6 years of follow-up, 158 previously obese children remained obese as they aged into adolescence, and 88 transiently obese children were not obese during the second survey, 58 children were newly identified obese, and the other 473 children remained their non-obese state. BMI Z-score increased from 1.41±0.05 at baseline to 1.57±0.06 at follow up.The genotypes of the SNPs except rs6499640(P=0.033) and rs6265(P=0.041) were in Hardy-Weinberg equilibrium in each group (P>0.05). Each additional copy of the rs9939609 A allele was significantly associated with an increase in BMI Z-score (β=0.205, P=0.014) during follow up. Per C allele of rs17782313 was associated with an increase in BMI Z-score at baseline (β=0.268, P=0.003). As the non-obese reference, a significantly relative risk of obesity at follow up was observed for children carrying rs9939609 A-allele versus the T-allele carriers (OR=2.37, 95%CI: 1.45-3.88, P=0.001). Rs17782313 C-allele was significantly increase the risk of obesity only at baseline (OR=1.79, 95%CI: 1.24-2.60, P=0.002). Rs1805081 A-allele was significantly associated with durative of obesity (OR=1.45, 95%CI: 1.04-2.03, P=0.028). Each unit higher genetic risk score was associated with increases risk of 0.18 times (OR=1.18, 95%CI: 1.05-1.33) in childhood transient obesity, and 0.22 times (OR=1.22, 95% CI: 1.06-1.42) in incident obesity at follow-up. But it was not significantly associated with persisted obesity during 6 years of follow-up (OR=1.09, 95% CI: 0.99-1.20). Conclusion: We confirmed that the change of BMI and obesity status in children was affected by different genetic factors. Individual who carries more risk alleles in obesity-related genes may increase the susceptibility to obesity.