Cardiohemodynamic responses and heart rate variability following an active orthostatic test among male residents of the North with different NOS3 (rs2070744) genotypes

AIM: This study explored associations between the -786T>C (rs2070744) genetic polymorphism of the NOS3 gene and the main indices of systemic hemodynamics and heart rate variability following an active orthostatic test in men living in the North.

MATERIAL AND METHODS: Eighty-three healthy men aged 33.5±1.5 yеаrs on average, who were permanent residents of the Magadan Region, comprised the sample. The participants underwent both resting and active orthostatic testing modes. Cardiovascular system variables were recorded using an automatic tonometer. Hemodynamic indices were then calculated. Short-term heart rate variability in frequency and spectral areas was simultaneously measured using the Varikard hard&soft complex unit. Genotyping was conducted using polymerase chain reaction. The sample was then divided into two groups: Group 1 consisted of homozygotes with the TT genotype (n=34), while Group 2 comprised carriers of the NOS3*C allele variant (genotypes TC+CC) associated with reduced nitric oxide production (n=49).

RESULTS: By examining the complex vasomotor, chrono- and inotropic reactions of hemodynamic and heart rate variables during the active orthostatic test, we were able to discern unique patterns in the response of the two groups under study. Men in Group 1 demonstrated an elevated cardiac output response during orthostatic changes, while maintaining consistent vascular resistance values. This was accompanied by a shift towards sympathetic autonomic activity and an increase in the very low-frequency component of heart rate variability. In Group 2, individuals with sympathetic insufficiency and increased vascular resistance during the orthostatic test showed a 35% increase in the low-frequency component of the cardiac rhythm reflecting the importance of this indicator as a stimulator of blood pressure rhythm fluctuations mediated by baroreflex mechanisms.

CONCLUSION: Our findings suggest that men lacking the NOS3*С allele variant in their genotype demonstrate more favorable responses to the active orthostatic test. This may reflect higher level of cardiovascular functional reserves. The 786T>C (rs2070744) polymorphism of the NOS3 gene can be considered as a marker of cardiohemodynamic status and autonomic regulations during functional exercise, such as an active orthostatic test.