Associations of Uncoupling Protein 2 Ala55Val and Uncoupling Protein 3-55C/T Polymorphisms with Heart Rate Variability in Young Oarsmen-a Pilot Study

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Background: Human heredity is known to determine about 50% of heart rate variability (HRV) based on a twin study; however, genetic polymorphisms causing increased HRV in athletes are not known. Objectives: This article is aimed at studying the associations of uncoupling protein 2 (UCP2) Ala55Val (rs660339) and UCP3-55C/T (rs1800849) polymorphisms with heart rate variability (HRV) in trained oarsmen. Methods: HRV indices (standard deviations of NN intervals (SDNN), root mean square of successive differences (RMSSD), HF, LF, VLF), stroke index and cardiac index of the young oarsmen (age 17.6 ± 1.6 years old, n = 23) were determined by impedance cardiography method in the supine and standing positions. The maximum oxygen consumption (VO2max) was examined with a rower ergometer by means of a gas analyzer. Polymorphisms of the UCP2 Ala55Val and the UCP3-55T/C were genotyped by polymerase chain reaction (PCR) method and length analysis of restriction products. Results: It was found that both polymorphisms were not associated with VO2max. The UCP2 Val/Val genotype compared to the combined variant (Ala/Ala + Ala/Val) containing the 55 Ala allele, as well as the UCP3 T/T genotype compared to the combined variant (C/T + C/C) containing the -55C allele were associated with low HR and increased HRV: SDNN, RMSSD and HF vagal indices in the supine position. Moreover, the athletes with the UCP3-55T/T genotype had a pronounced increase in heart rate (ANOVA, P < 0.001) and a decrease in stroke index (ANOVA, P = 0.005) in response to active orthostasis compared to C/T and C/C genotypes. Conclusions: The UCP2 Val/Val and the UCP3 T/T genotypes may be genetic markers of increased HRV in the highly trained athletes, suggesting an influence of these UCP2/UCP3 polymorphisms on autonomic cardiovascular regulation.