Removal of the normal head-to-foot gravity vector and chronic weightlessness during spaceflight might induce cardiovascular and metabolic adaptations related to changes in arterial pressure and reduction in physical activity. We tested hypotheses that stiffness of arteries located above the heart would be increased postflight, and that blood biomarkers inflight would be consistent with changes in vascular function. Possible sex differences in responses were explored in four male and four female astronauts who lived on the International Space Station for 6 mo. Carotid artery distensibility coefficient (P = 0.005) and beta-stiffness index (P = 0.006) reflected 17-30% increases in arterial stiffness when measured within 38 h of return to Earth compared with preflight. Spaceflight-by-sex interaction effects were found with greater changes in beta-stiffness index in women (P = 0.017), but greater changes in pulse wave transit time in men (P = 0.006). Several blood biomarkers were changed from preflight to inflight, including an increase in an index of insulin resistance (P < 0.001) with a spaceflight-by-sex term suggesting greater change in men (P = 0.034). Spaceflight-by-sex interactions for renin (P = 0.016) and aldosterone (P = 0.010) indicated greater increases in women than men. Six-month spaceflight caused increased arterial stiffness. Altered hydrostatic arterial pressure gradients as well as changes in insulin resistance and other biomarkers might have contributed to alterations in arterial properties, including sex differences between male and female astronauts.
Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/26747504
Research Containing: c-reactive protein
Bone marrow fat accumulation after 60 days of bed rest persisted 1 year after activities were resumed along with hemopoietic stimulation: the Women International Space Simulation for Exploration study
Immobility in bed and decreased mobility cause adaptations to most human body systems. The effect of immobility on fat accumulation in hemopoietic bone marrow has never been measured prospectively. The reversibility of marrow fat accumulation and the effects on hemopoiesis are not known. In the present study, 24 healthy women (age: 25–40 yr) underwent −6° head-down bed rest for 60 days. We used MRI to noninvasively measure the lumbar vertebral fat fraction at various time points. We also measured hemoglobin, erythropoietin, reticulocytes, leukocytes, platelet count, peripheral fat mass, leptin, cortisol, and C-reactive protein during bed rest and for 1 yr after bed rest ended. Compared with baseline, the mean (± SE) fat fraction was increased after 60 days of bed rest (+2.5 ± 1.1%, P < 0.05); the increase persisted 1 yr after the resumption of regular activities (+2.3 ± 0.8%, P < 0.05). Mean hemoglobin levels were significantly decreased 6 days after bed rest ended (−1.36 ± 0.20 g/dl, P < 0.05) but had recovered at 1 yr, with significantly lower mean circulating erythropoietin levels (−3.8 ± 1.2 mU/ml, P < 0.05). Mean numbers of neutrophils and lymphocytes remained significantly elevated at 1 yr (+617 ± 218 neutrophils/μl and +498 ± 112 lymphocytes/μl, both P < 0.05). These results constitute direct evidence that bed rest irreversibly accelerated fat accumulation in hemopoietic bone marrow. The 2.5% increase in fat fraction after 60 days of bed rest was 25-fold larger than expected from historical ambulatory controls. Sixty days of bed rest accelerated by 4 yr the normal bone marrow involution. Bed rest and marrow adiposity were associated with hemopoietic stimulation. One year after subjects returned to normal activities, hemoglobin levels were maintained, with 43% lower circulating erythropoietin levels, and leukocytes remained significantly elevated across lineages. Lack of mobility alters hemopoiesis, possibly through marrow fat accumulation, with potentially wide-ranging clinical consequences.
Related URLs:
http://jap.physiology.org/jap/107/2/540.full.pdf
Cardiac Health for Astronauts: Coronary Calcification Scores and CRP as Criteria for Selection and Retention
Due to the limited treatment and return capabilities of most space vehicles, an in-flight cardiac event could result in significant mission impact or even failure. The current literature supports including electron-beam computed tomography (EBCT) and highly selective C-reactive protein (hsCRP) for diagnosis of coronary artery disease (CAD) in asymptomatic, low-pretest probability cohorts. This paper will examine the issues surrounding adding these tests to astronaut retention and selection algorithms. An evidenced-based literature review was performed and consensus obtained from subject-matter experts to create novel cardiac screening algorithms for astronaut applicants and the current astronaut corps. The main focus of this paper is to derive an evidenced-based approach for improving the diagnosis of significant CAD using EBCT and hsCRP testing. The recommended initial astronaut selection and long-duration mission assignment screening algorithms use EBCT-derived calcium scores and serum hsCRP levels to screen for CAD and predict individual cardiac risk. The current medical evidence is compelling for the international space medicine community to consider: 1.) Astronaut candidates with a coronary artery calcium score > 0 should be disqualified from initial selection; 2.) Astronauts with a coronary artery calcium score > 100 should be disqualified from selection for long-duration missions; 3.) Elevated hsCRP is a reliable risk factor for helping predict future cardiac events that should warrant primary prevention but not necessarily medical disqualification.
Related URLs:
http://www.ingentaconnect.com/content/asma/asem/2006/00000077/00000004/art00001