Minor diplotypes of FMO3 might protect children and adolescents from obesity and insulin resistance

In order to assess whether flavin-containing monooxygenase-3 (FMO3) might be involved in early cardiovascular risk, we assessed adiposity and traditional metabolic variables in children/adolescents grouped according to their genotypes in two FMO3 exonic polymorphisms, rs2266782 (E158K) and rs2266780 (E308G), which are in linkage disequilibrium and have been associated with decreased FMO3 activity. Among 776 children/adolescents (10.8 ± 2.2 years) recruited from the general population (452) and from our obesity outpatient clinic (324), the 68 carrying either the 158K-308G/158K-308E or the 158K-308G/158K-308G diplotype had lower mean z-BMI and prevalence of obesity compared to their 708 peers carrying any of the other diplotypes (0.39 vs 0.80, p = 0.01; OR = 0.39[0.17-0.87], p = 0.018, respectively), and to the sub-sample of 303 children carrying the major diplotype (158E-308E/158E-308E) (0.39 vs 0.87, p = 0.008; OR = 0.35[0.16-0.81], p = 0.014, respectively). They also had lower z-BMI-adjusted lnHOMA-IR compared to all the other children (0.75 vs 0.97, p = 0.001) and those carrying the major diplotype, (0.75 vs 0.98, p = 0.03), as well as lower z-BMI-adjusted iln-triglycerides compared to all the other children (3.98 vs 4.17, p = 0.037). These associations provide the first evidence that FMO3 may be involved in early body weight, insulin sensitivity, and lipid regulation in humans.