Dynamic Changes of Heart Failure Biomarkers in Response to Parabolic Flight.

BACKGROUND: we aimed at investigating the influence of weightlessness and hypergravity by means of parabolic flight on the levels of the heart failure biomarkers H-FABP, sST2, IL-33, GDF-15, suPAR and Fetuin-A. METHODS: 14 healthy volunteers (males: eight; mean age: 28.9) undergoing 31 short-term phases of weightlessness and hypergravity were included. At different time points (baseline, 1 h/24 h after parabolic flight), venous blood was drawn and analyzed by the use of ELISA. RESULTS: sST2 evidenced a significant decrease 24 h after parabolic flight (baseline vs. 24, p = 0.009; 1 h vs. 24 h, p = 0.004). A similar finding was observed for GDF-15 (baseline vs. 24 h, p = 0.002; 1 h vs. 24 h, p = 0.025). The suPAR showed a significant decrease 24 h after parabolic flight (baseline vs. 24 h, p = 0.1726; 1 h vs. 24 h, p = 0.009). Fetuin-A showed a significant increase at 1 h and 24 h after parabolic flight (baseline vs. 24 h, p = 0.007; 1 h vs. 24 h, p = 0.04). H-FABP and IL-33 showed no significant differences at all time points. CONCLUSION: Our results suggest a reduction in cardiac stress induced by exposure to gravitational changes. Moreover, our findings indicate an influence of gravitational changes on proliferative processes and calcium homeostasis.

Next-generation sequencing analysis of circulating micro-RNA expression in response to parabolic flight as a spaceflight analogue.

Understanding physiologic reactions to weightlessness is an indispensable requirement for safe human space missions. This study aims to analyse changes in the expression of circulating miRNAs following exposure to gravitational changes. Eight healthy volunteers (age: 24.5 years, male: 4, female: 4) were included. Each subject underwent 31 short-term phases of weightlessness and hypergravity induced by parabolic flight as a spaceflight analogue. At baseline, 1 and 24 h after parabolic flight, venous blood was withdrawn. Analysis of circulating miRNAs in serum was conducted by means of next generation sequencing. In total, 213 miRNAs were robustly detected (TPM > 5) by small RNA sequencing in all 24 samples. Four miRNAs evidenced a significant change in expression after adjusting for multiple testing. Only miR-223-3p showed a consistent significant decrease 24 h after parabolic flight compared to baseline values and values at 1 h after parabolic flight. miR-941 and miR-24-3p showed a significant decrease 24 h after parabolic flight compared to 1 h after parabolic flight but not to baseline values. miR-486-5p showed a significant increase 24 h after parabolic flight compared to 1 h after parabolic flight but not to baseline values. A target network analysis identified genes of the p53 signaling pathway and the cell cycle highly enriched among the targets of the four microRNAs. Our findings suggest cellular adaption to gravitational changes at the post-transcriptional level. Based on our results, we suggest a change in cell cycle regulation as potential explanation for adaptational changes observed in space missions.

Comprehensive Analysis of Macrocirculation and Microcirculation in Microgravity During Parabolic Flights.

BACKGROUND: Profound knowledge about cardiovascular physiology in the setting of microgravity can help in the course of preparations for human space missions. So far, influences of microgravity on the cardiovascular system have been demonstrated, particularly pertaining to venous fluid shifts. Yet, little is known about the mechanisms of these adaptations on continuous macrocirculatory level and regarding the microcirculation. METHODS: Twelve healthy volunteers were subjected to alternating microgravity and hypergravity in the course of parabolic flight maneuvers. Under these conditions, as well as in normal gravity, the sublingual microcirculation was assessed by intravital sidestream dark field microscopy. Furthermore, hemodynamic parameters such as heart rate, blood pressure, and cardiac output were recorded by beat-to-beat analysis. In these settings, data acquisition was performed in seated and in supine postures. RESULTS: Systolic [median 116 mmHg (102; 129) interquartile range (IQR) vs. 125 mmHg (109; 136) IQR, p = 0.01] as well as diastolic [median 72 mmHg (61; 79) IQR vs. 80 mmHg (69; 89) IQR, p = 0.003] blood pressure was reduced, and cardiac output [median 6.9 l/min (6.5; 8.8) IQR vs. 6.8 l/min (6.2; 8.5) IQR, p = 0.0002] increased in weightlessness compared to normal gravitation phases in the seated but not in the supine posture. However, microcirculation represented by perfused proportion of vessels and by total vessel density was unaffected in acute weightlessness. CONCLUSION: Profound changes of the macrocirculation were found in seated postures, but not in supine postures. However, microcirculation remained stable in all postures.

Exposure to acute normobaric hypoxia results in adaptions of both the macro- and microcirculatory system.

Although acute hypoxia is of utmost pathophysiologic relevance in health and disease, studies on its effects on both the macro- and microcirculation are scarce. Herein, we provide a comprehensive analysis of the effects of acute normobaric hypoxia on human macro- and microcirculation. 20 healthy participants were enrolled in this study. Hypoxia was induced in a normobaric hypoxia chamber by decreasing the partial pressure of oxygen in inhaled air stepwisely (pO2; 21.25 kPa (0 k), 16.42 kPa (2 k), 12.63 kPa (4 k) and 9.64 kPa (6 k)). Macrocirculatory effects were assessed by cardiac output measurements, microcirculatory changes were investigated by sidestream dark-field imaging in the sublingual capillary bed and videocapillaroscopy at the nailfold. Exposure to hypoxia resulted in a decrease of systemic vascular resistance (p < 0.0001) and diastolic blood pressure (p = 0.014). Concomitantly, we observed an increase in heart rate (p < 0.0001) and an increase of cardiac output (p < 0.0001). In the sublingual microcirculation, exposure to hypoxia resulted in an increase of total vessel density, proportion of perfused vessels and perfused vessel density. Furthermore, we observed an increase in peripheral capillary density. Exposure to acute hypoxia results in vasodilatation of resistance arteries, as well as recruitment of microvessels of the central and peripheral microcirculation. The observed macro- and microcirculatory effects are most likely a result from compensatory mechanisms to ensure adequate tissue oxygenation.

Blood parameter analysis after short term exposure to weightlessness in parabolic flight.

BACKGROUND: Parabolic flights offer a unique platform for human experiments in short-term weightlessness. It is generally known that human organ systems react to changes of gravity. Yet, little is known about alterations of blood parameters under these conditions with special emphasis on blood rheology. OBJECTIVE: We investigated the alterations of distinct blood parameters after exposure to weightlessness. METHODS: 14 healthy volunteers underwent short-term phases of weightlessness induced by parabolic flight. At different time points (baseline, t2:1 hour after landing, and t3:24 hours after baseline), venous blood was drawn and analyzed. RESULTS: Analysis of red blood count revealed significant decreases of hemoglobin and hematocrit post flight. While total white blood counts were unaltered, differential subset analysis revealed significant decreases of eosinophil granulocytes and monocytes. Cortisole levels were unchanged and lacked physiologic circadian decrease. Parameters of renal function were found significantly improved (GFR (ml/min/1,73m2): Baseline: 105 [89;109], t2:117 [98;125], t3:110 [102;119]; p = 0.0013. In the sense of mild myocytolysis, levels of myoglobin were significantly elevated post-flight with fast recovery to baseline levels. CONCLUSIONS: In the current analysis, significant alterations of blood parameters after exposure to weightlessness could be detected. These results contribute to the understanding of physiologic adaptations of the human body to weightlessness.