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De Abreu, Amirova, et al: Multi-System Deconditioning in 3-Day Dry Immersion without Daily Raise (microgravity simulation study)

Discussion in 'Health News and Research unrelated to ME/CFS' started by WillowJ, Nov 10, 2018.

  1. WillowJ

    WillowJ Senior Member (Voting Rights)

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    Multi-System Deconditioning in 3-Day Dry Immersion without Daily Raise

    Abstract:
    Dry immersion (DI) is a Russian-developed, ground-based model to study the physiological effects of microgravity. It accurately reproduces environmental conditions of weightlessness, such as enhanced physical inactivity, suppression of hydrostatic pressure and supportlessness.

    We aimed to study the integrative physiological responses to a 3-day strict DI protocol in 12 healthy men, and to assess the extent of multi-system deconditioning. We recorded general clinical data, biological data and evaluated body fluid changes.

    Cardiovascular deconditioning was evaluated using orthostatic tolerance tests (Lower Body Negative Pressure + tilt and progressive tilt). Metabolic state was tested with oral glucose tolerance test. Muscular deconditioning was assessed via muscle tone measurement.

    Results: Orthostatic tolerance time dropped from 27 ± 1 to 9 ± 2 min after DI. Significant impairment in glucose tolerance was observed. Net insulin response increased by 72 ± 23% on the third day of DI compared to baseline. Global leg muscle tone was approximately 10% reduced under immersion.

    Day-night changes in temperature, heart rate and blood pressure were preserved on the third day of DI. Day-night variations of urinary K+diminished, beginning at the second day of immersion, while 24-h K+ excretion remained stable throughout. Urinary cortisol and melatonin metabolite increased with DI, although within normal limits. A positive correlation was observed between lumbar pain intensity, estimated on the second day of DI, and mean 24-h urinary cortisol under DI.

    In conclusion
    , DI represents an accurate and rapid model of gravitational deconditioning. The extent of glucose tolerance impairment may be linked to constant enhanced muscle inactivity. Muscle tone reduction may reflect the reaction of postural muscles to withdrawal of support. Relatively modest increases in cortisol suggest that DI induces a moderate stress effect.

    In prospect
    , this advanced ground-based model is extremely suited to test countermeasures for microgravity-induced deconditioning and physical inactivity-related pathologies.


    Steven De Abreu1†, Liubov Amirova1,2†, Ronan Murphy3, Robert Wallace3, Laura Twomey3, Guillemette Gauquelin-Koch4, Veronique Raverot5, Françoise Larcher6, Marc-Antoine Custaud1,7* and Nastassia Navasiolava7
    • 1Mitovasc, UMR Institut National de la Santé et de la Recherche Médicale 1083, Centre National de la Recherche Scientifique 6015, Université d'Angers, Angers, France
    • 2Russian Federation State Research Center, Institute of Biomedical Problems, Russian Academy of Sciences, Moscow, Russia
    • 3Center for Preventive Medicine, School of Health and Human Performance, Dublin City University, Dublin, Ireland
    • 4Centre National d'Etudes Spatiales, Paris, France
    • 5Hospices Civils de Lyon, Lyon, France
    • 6Laboratoire de Biochimie, Centre Hospitalier Universitaire d'Angers, Angers, France
    • 7Centre de Recherche Clinique, Centre Hospitalier Universitaire d'Angers, Angers, France
    Front. Physiol., 13 October 2017 | https://doi.org/10.3389/fphys.2017.00799

    Full text available
     
    Trish likes this.
  2. WillowJ

    WillowJ Senior Member (Voting Rights)

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  3. WillowJ

    WillowJ Senior Member (Voting Rights)

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    Be sure to expand that second quote
     
  4. WillowJ

    WillowJ Senior Member (Voting Rights)

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    “Muscle tone variations under DI are shown in Figure 7. Global leg muscle tone, proxy measured by “frequency” parameter, was decreased by approximately 10% under immersion. This decrease was immediate (seen 6 h following the onset of DI) ...

    “Six hours following the end of DI, muscle tone was completely restored.”
     
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  5. WillowJ

    WillowJ Senior Member (Voting Rights)

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    “Data are detailed in Table 2. Plasma electrolytes showed modest changes without clinical relevance.

    “Blood count remained unchanged except for a modest but highly significant decrease in RBC volume, accompanied by slight increase in MCHC on R+1 vs. B-3.

    “Blood GGT, ALAT, ASAT, alkaline phosphatase, total bilirubin, prothrombin time and serum albumin were not modified on R+1 vs. B-3. CRP levels were unaltered by DI.”
     
  6. WillowJ

    WillowJ Senior Member (Voting Rights)

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    “Seventy-five percent of our subjects were intolerant to orthostasis on R0 after 3 days of strict DI. In comparison with literature data using chi-square test, orthostatic intolerance rate after strict bed rest without countermeasures does not differ significantly from our findings...

    “However, the reported rate of orthostatic intolerance following non-strict DI seems much less-approximately 15 to 40% of subjects for 1 to 7 days of DI....

    “The main differentiator of our DI was the maintenance of supine position throughout. Our data suggest that daily short periods out of the water tank in sitting or standing positions represent a powerful countermeasure against orthostatic intolerance induced by DI. Periodic short gravitational stimuli appear to be effective countermeasures, maintaining gravitational tolerance....

    “Thus, a daily short period of orthostatic stress is sufficient to reduce the risk of orthostatic intolerance after simulated weightlessness. Daily short term gravitational load might also promote the preservation of baroreflex sensitivity and autonomic balance.”
     
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  7. WillowJ

    WillowJ Senior Member (Voting Rights)

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    “The negative metabolic effects of DI are mainly related to increased inactivity. DI rapidly impaired glucose metabolism and lipid profile, inducing a decrease in insulin sensitivity and dyslipidemia.”
     

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