Association of specific LDL receptor gene mutations with differential plasma lipoprotein response to simvastatin in young French Canadians with heterozygous familial hypercholesterolemia.

In familial hypercholesterolemia (FH), the efficacy of the inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase shows considerable interindividual variation, and several genetic and environmental factors can contribute to explaining this variability. A randomized, double-blind, placebo-controlled clinical trial with simvastatin, an HMG-CoA reductase inhibitor, was conducted in 63 children and adolescents with heterozygous FH. The patients were grouped according to known LDL receptor genotype. After 6 weeks of treatment with 20 mg/d simvastatin, the mean reduction in plasma LDL cholesterol in patients with the W66G mutation (n=14) was 31%, whereas in the deletion>15 kb (n=23) and the C646Y mutation groups (n=10), it was 38% and 42%, respectively (P<0.05). After treatment with simvastatin, HDL cholesterol levels were increased in all groups, and triglyceride concentrations were significantly reduced. Multiple regression analyses suggested that 42% of the variation of the LDL cholesterol response to simvastatin can be attributed to variation in the mutant LDL receptor locus, apolipoprotein E genotype, and body mass index, while 35% of the variation in HDL cholesterol response was explained by sex and baseline HDL cholesterol. These results show that simvastatin was an effective and well-tolerated therapy for FH in the pediatric population for all LDL receptor gene mutations. Moreover, the nature of LDL receptor gene mutations and other genetic and constitutional factors play a significant role in predicting the efficacy of simvastatin in the treatment of FH in children and adolescents.