β1-adrenergic receptor polymorphisms and antihypertensive response to metoprolol

Objectives: Marked interpatient variability exists in blood pressure response to beta-blocker monotherapy. We tested the hypothesis that 2 common polymorphisms in the gene for beta(1)-adrenergic receptor are associated with antihypertensive response to metoprolol in patients with uncomplicated hypertension. Methods: Forty hypertensive men and women aged 35 to 65 years were studied. Baseline studies included 24-hour ambulatory blood pressure monitoring. Patients took 50 mg metoprolol twice daily with weekly titration to response or 200 mg twice daily. After a minimum of 4 weeks at stable dose, treatment phase 24-hour ambulatory blood pressure monitoring was repeated. The codon 49 and 389 genotypes for beta(1)-adrenergic receptor were determined by polymerase chain reaction with restriction fragment length polymorphism. Multilinear regression was performed to determine the impact of genotype and other variables on blood pressure response to metoprolol. Results: Patients homozygous for Arg at codon 389 had a nearly 3-fold greater reduction in daytime diastolic blood pressure (-13.3% +/- 8.4% versus -4.5% +/- 8.2%, P =.0018) compared with those who carried the variant allele. The haplotype pair (diplotype) for beta(1)-adrenergic receptor was also a significant predictor of response, with patients having the Ser49Arg389/Ser49Arg389 diplotype demonstrating a decline in blood pressure of 14.7 mm Hg versus 0.5 mm Hg in patients with the G1y49Arg389/Ser49Gly389 diplotype. In multiregression analysis, baseline daytime diastolic blood pressure, codon 389 genotype, and codon 49 genotype were significant predictors of blood pressure after treatment. Conclusions: Our data suggest that beta(1)-adrenergic receptor polymorphisms are important determinants of antihypertensive response to metoprolol. In the future, codon 49 and 389 genotypes or beta(1)-adrenergic receptor haplotypes might be used to predict the diastolic blood pressure response to metoprolol in patients with hypertension.