Research of the Plasma Protein Profile in Comparison with the Biochemical Parameters of Blood of Volunteers in a 21-Day Head Down Bed Rest

Study of changes in the proteome of extracellular body fluids under conditions of simulated weightlessness of medium duration (21 days) remains relevant for clarifying the physiological mechanisms of homeostasis regulation and is important for gravitational physiology and medicine. Plasma samples of 8 healthy volunteers participating in head down bed rest (HDBR –6°) experiment were studied using semi-quantitative proteomics methods. Each volunteer participated both in the control session and in the session with physical training for negative changes prevention. By the end of HDBR, significant changes in the concentration of proteins involved in platelet degranulation, blood coagulation, fibrinolysis, proteolysis regulation, complement activation, and the immune response were detected in both sessions. The following changes in biochemical parameters of carbohydrate metabolism and regulation of circulating blood volume were shown: a significant increase in renin concentration and a tendency to an increase in aldosterone; an increase in fasting insulin concentration and a tendency to an increase in the insulin resistance index. Physical training did not have a significant effect on biochemical parameters, except for the representation of cholesterol fractions, un which a significant decrease in the concentration of high-density lipoprotein cholesterol observed in HDBR became statistically insignificant in session with physical training. However, the protein composition in blood plasma of volunteers in the prophylaxis session changed less compared to HDBR. Physical training resulted in increase in the concentration of proteins involved in the normalization of carbohydrate and lipid metabolism, such as a macrophage stimulating protein and phosphatidylinositol-glycan-specific phospholipase D, which indicates the effectiveness of preventive measures.