Genetic susceptibility to obesity and related traits in childhood and adolescence: influence of loci identified by genome-wide association studies.
OBJECTIVE
Large-scale genome-wide association (GWA) studies have thus far identified 16 loci incontrovertibly associated with obesity-related traits in adults. We examined associations of variants in these loci with anthropometric traits in children and adolescents.


METHODS
Seventeen variants representing 16 obesity susceptibility loci were genotyped in 1,252 children (mean ± SD age 9.7 ± 0.4 years) and 790 adolescents (15.5 ± 0.5 years) from the European Youth Heart Study (EYHS). We tested for association of individual variants and a genetic predisposition score (GPS-17), calculated by summing the number of effect alleles, with anthropometric traits. For 13 variants, summary statistics for associations with BMI were meta-analyzed with previously reported data (N(total) = 13,071 children and adolescents).


RESULTS
In EYHS, 15 variants showed associations or trends with anthropometric traits that were directionally consistent with earlier reports in adults. The meta-analysis showed directionally consistent associations with BMI for all 13 variants, of which 9 were significant (0.033-0.098 SD/allele; P < 0.05). The near-TMEM18 variant had the strongest effect (0.098 SD/allele P = 8.5 × 10(-11)). Effect sizes for BMI tended to be more pronounced in children and adolescents than reported earlier in adults for variants in or near SEC16B, TMEM18, and KCTD15, (0.028-0.035 SD/allele higher) and less pronounced for rs925946 in BDNF (0.028 SD/allele lower). Each additional effect allele in the GPS-17 was associated with an increase of 0.034 SD in BMI (P = 3.6 × 10(-5)), 0.039 SD, in sum of skinfolds (P = 1.7 × 10(-7)), and 0.022 SD in waist circumference (P = 1.7 × 10(-4)), which is comparable with reported results in adults (0.039 SD/allele for BMI and 0.033 SD/allele for waist circumference).


CONCLUSIONS
Most obesity susceptibility loci identified by GWA studies in adults are already associated with anthropometric traits in children/adolescents. Whereas the association of some variants may differ with age, the cumulative effect size is similar.
den Hoed
Marcel
M
Medical Research Council Epidemiology Unit, Institute of Metabolic Science, Cambridge, UK.
Ekelund
Ulf
U
Brage
Søren
S
Grontved
Anders
A
Zhao
Jing Hua
JH
Sharp
Stephen J
SJ
Ong
Ken K
KK
Wareham
Nicholas J
NJ
Loos
Ruth J F
RJ
D000293:Adolescent; D000328:Adult; D002648:Child; D002874:Chromosome Mapping; D005260:Female; D020022:Genetic Predisposition to Disease; D014644:Genetic Variation; D055106:Genome-Wide Association Study; D006801:Humans; D008297:Male; D009765:Obesity / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D012885:Skinfold Thickness; D055105:Waist Circumference; D044465:White People / Q000235:genetics