Introduction: Left ventricular hypertrophy in response to endurance training is a common feature in athletes. Twin studies, as well as association studies have shown that genetic factors play a role in the determination of the so called athlete`s heart (1). In two recent studies, variants of the gene encoding the Beta-1 adrenoceptor (B1AR) has been associated with enlargement of the left ventricle in two different cohorts of sedentary subjects (2,3). The aim of our study was to investigate the role of B1AR and Beta-2 adrenoceptor (B2AR) genetic polymorphisms for the development of left ventricular hypertrophy in endurance athletes. Methods: We studied a cohort of 198 male Caucasian athletes involved in different endurance sports with a training history of at least 5 years (Tab. 1). Left ventricular mass was determined using M-mode echocardiography. Left ventricular mass index (LVMI) was calculated using Devereux`s formula with correction for the body surface area. Subjects were typed for five polymorphisms in the B1AR and B2AR genes: Ser49Gly, Arg389Gly in the B1AR gene and Arg16Gly, Glu27Gln and Arg19Cys in the B2AR gene, respectively. Results: Genotype distributions for all polymorphisms were in Hardy-Weinberg equilibrium. No association was seen between LVM or LVMI and the three investigated polymorphisms in the B2AR gene (p-values from 0,177 to 0,983). In addition we found no significant association for the Arg389Gly polymorphism and LVM or LVMI (p = 0.093 and 0.232, respectively). A significant association was found for Ser49Gly genotype and LVM (p=0.036, Tab.2). Further analysis revealed a higher LVMI in carriers of the Gly-Allele compared to subjects homozygote for the Ser-Allele (LVMI 154g/m-2 vs. 145g/m-2, p=0.014, Tab. 3). Discussion/Conclusion: The mechanism of a possible association of left ventricular size and mass with the Ser49GlyADRB1 polymorphism is unknown at present. Data shown by Stanton and co-workers (2) showed a relation between left ventricular mass and this particular polymorphism in patients with renal failure. Thus far we have no data, that this polymorphism is associated with the development of the so called "athletes heart". Our data from a large sample of highly trained endurance athletes showed an association of Gly-carrier-status of the Ser49GlyADRB1 polymorphism with echocardiographic measures of left ventricular mass. Tab. 3: Mann-Whitney-Test for Gly-carrier-status of the Ser49GlyADRB1-Polymorphism In summary, we found evidence that a Single Nucleotide Polymorphism (Ser49Gly) located in the B1AR gene, may play a role in the development of left ventricular hypertrophy in highly trained endurance athletes.
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