Correlation Between Invariable Blood Proteins and Heart Rate Variability in Long-Duration Space Flights

The article analyzes how long-duration space missions’ effect on the heart rate variability parameters and invariable blood proteins. The results are discussed taking into correlation between them. Seven Russian cosmonauts took part in the research during their missions to the International Space Station. Samples of dry blood drops were collected as part of the space experiment ''OMICs-DBS'', electrocardiogram samples were collected as part of the space experiment "Cardiovector". We have established a linear relationship between the concentrations of the following proteins: complement C1q subcomponent subunit A (encoded by the C1QA gene), complement C1r subcomponent (encoded by the C1R gene), fibrinogen gamma chain (encoded by the FGG gene),galectin-3 (encoded by the LGALS3 gene), interstitial collagenase or matrix metalloproteinase-1 (encoded by the MMP-1 gene), pigment epithelium-derived factor (encoded by the PEDF gene) and frequency-domain heart rate variability (HRV) parameters at some stages of space flight. Three proteins were associated with of total power parameters, and either positively correlated with the low-frequency (LF) domain as in the case of the C1QA (complement C1q subcomponent subunit A) or negatively - LGALS3, MMP-1 (galectin-3, matrix metalloproteinase-1) correlated with the high-frequency domain (HF). One of the proteins, the PEDF (pigment epithelium-derived factor), positively correlated with the HF, which correspondingly reflected the effect of vagal modulation on the SA node. The Complement C1r subcomponent had positive correlations with both HF and LF. The FGG (fibrinogen gamma chain) was negatively correlated with both individual components of the frequency-domain (HF, ms2 and LF ms2) also its total power. We assume that such statistical relationships reflect the tension of regulatory mechanisms, which is consistent with classical studies of autonomic regulation in space flight.