The Arg389Gly beta1-adrenoceptor gene polymorphism determines contractile response to catecholamines

Area of Science:

• Cardiovascular Genetics
• Pharmacogenomics
• Human Physiology

Background:

• The beta1-adrenoceptor (beta1AR) gene harbors the Arg389Gly polymorphism, with the Arg variant showing increased in vitro agonist responsiveness.
• Previous in vitro and in vivo studies on the functional relevance of this polymorphism have yielded conflicting results.
• Understanding the in vivo functional consequences of beta1AR gene variants is crucial for personalized medicine.

Purpose of the Study:

• To investigate the in vivo functional significance of the Arg389Gly beta1-adrenoceptor polymorphism in healthy male volunteers.
• To compare the cardiac response to dobutamine stress echocardiography across different beta1AR genotypes.
• To determine if the Arg389Gly polymorphism affects heart rate, blood pressure, and myocardial contractility.

Main Methods:

• Genotyping for the beta1AR Arg389Gly polymorphism using PCR, restriction analysis, and DNA sequencing.
• Administration of a modified dobutamine stress echocardiography protocol to assess cardiac function.
• Comparison of heart rate, blood pressure, fractional shortening, and pressure-dimension ratio among genotype groups.

Main Results:

• Homozygous Arg389 individuals exhibited significantly greater increases in fractional shortening compared to Gly389 carriers upon dobutamine administration.
• Enhanced systolic blood pressure response to dobutamine was observed in Arg389 homozygotes; heart rate response did not differ.
• Analysis of pressure-dimension ratio indicated that the observed beta1AR-mediated effects are primarily due to increased myocardial inotropy.

Conclusions:

• The Arg389Gly beta1AR polymorphism is functionally relevant in vivo.
• This polymorphism significantly influences human contractile responsiveness to catecholamines.
• The findings support the role of beta1AR genotype in modulating cardiovascular response to adrenergic stimulation.