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

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. 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. 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. 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. 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.