Variations in the obesity genes FTO, TMEM18 and NRXN3 influence the vulnerability of children to weight gain induced by short sleep duration

OBJECTIVE: Shorter sleep duration predisposes to obesity, but the mechanisms whereby sleep deprivation affects body weight are poorly understood. We tested whether this association is modulated by the obesity genes FTO, TMEM18 and NRXN3. SUBJECTS: Body mass index (BMI), waist circumference, visceral fat (abdominal ultrasound), homeostasis model assessment for insulin resistance (HOMA-IR), systolic blood pressure (SBP) and sleep time per 24 h were assessed in 297 asymptomatic children (151 boys, 146 girls; age range 5-9 years; BMI s.d. score range -2.0-4.0). Associations between sleep duration and the abovementioned outcomes were tested for three common single-nucleotide polymorphisms (SNPs), namely FTO (rs9939609), TMEM 18 (rs4854344) and NRXN3 (rs10146997), as well as for their combination. RESULTS: TT homozygotes (but not A* carriers) for the FTO SNP, exhibited nominal associations between decreasing sleep duration and increasing BMI, waist circumference, visceral fat and HOMA-IR (all P<0.05). Similar associations were observed in children with risk alleles (but not in those without risk alleles) for the TMEM18 and NRXN3 SNPs (P<0.05 to P<0.0001). The three SNPs had additive effects on the negative associations between sleep and, respectively, BMI (P<0.001), waist (P<0.005), visceral fat (P<0.001), HOMA-IR (P=0.010) and SBP (P<0.0005). The combined effects on obesity measures and SBP remained significant after correction for multiple testing. On an average, 2 h of sleep less per night was associated with an increase in BMI of 1.0 s.d. (95% confidence interval 0.5-1.6 s.d.) and with 8.0 cm (95% confidence interval 3.6-12.2 cm) more waist circumference in genetically susceptible children. CONCLUSION: By age 7, common variations in FTO, TMEM18 and NRXN3 influence the vulnerability to metabolic complications of sleep deprivation. Further genetic studies are warranted to replicate these findings in other populations. International Journal of Obesity (2013) 37, 182-187; doi:10.1038/ijo.2012.27; published online 6 March 2012