Thigh Cuffs to Prevent the Deconditioning Induced by 5 Days of Dry Immersion

Study Overview
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Brief Summary
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The objective of the study is to investigate whether thigh cuffs help to prevent and/or reduce the deconditioning induced by 5 days of dry immersion and in particular the fluid shift and its related ophthalmological disorders. During a randomized 5 day dry-immersion study in 20 healthy male adults the two following aims will be undertaken: Ten scientific protocols will assess the changes in the cerebral, ocular, cardiovascular, metabolism, cognitive, muscle and bone systems. In the above mentioned systems, the potential beneficial effects of the countermeasure protocol will also be investigated.

Detailed Description
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Space flights have shown the possibilities and limitations of human adaptation to space. For the last 50 years, results showed that the space environment and microgravity in particular, cause changes that may affect the performance of astronauts. These physiological changes are now better known: prolonged exposure to a weightlessness environment can lead to significant loss of bone, muscle mass, strength, cardiovascular and sensory-motor deconditioning, immune, hormonal and metabolism changes. Nevertheless, more recent missions have revealed a new suite of physiological adaptations and consequences of space flight. Indeed, astronauts exposed to prolonged weightlessness experience hyperopic shifts and structural alteration in the eye (e.g., choroidal folds and optic disc edema). This condition was defined by NASA as Spaceflight-Associated Neuro-ocular Syndrome (SANS). Some of these vision changes remain unresolved for years after flight. This phenomenon has most likely existed since the beginning of human space flight, but is just recently being recognized as a major consequence of adaptation to microgravity. Changes in vision and eye structure are thought to be the result of prolonged exposure to space flight-induced headward fluid shifts and elevated intracranial pressure. Loss of the hydrostatic pressure gradient during spaceflight leads to this redistribution of body fluids toward the head. To prepare for future manned missions beyond the low Earth Orbit, the mechanisms underlying SANS syndrome have to be investigated and countermeasures designed to reverse or prevent SANS are required. Venoconstrictive thigh cuffs (VTCs) represent one possible countermeasure to mitigate a headward fluid shift. The Russian Space Agency uses VTCs (bracelets) to sequester fluid in the lower limbs and mitigate the subjective sensation of head congestion during space-flight. Moreover, experiments on 6-month Mir missions demonstrated that bracelets reduced jugular vein cross-sectional area in cosmonauts by 12% to 20%. However, it is unknown how VTCs (including bracelets) affect ocular physiologic features. The space agencies are actively engaged in studying the initiation and progression of SANS syndrome through studies on the International Space Station and on the ground. Indeed, considering the limited number of flight opportunities, the difficulties related to the performance of in-flight experiments (operational constraints for astronauts, limited capabilities of in-flight biomedical devices), ground-based experiments simulating the effects of weightlessness are used to better understand the mechanisms of physiological adaptation, design and validate the countermeasures. Different methods are used to simulate microgravity on Earth. However, two separate approaches, -6° head-down bed rest (HDBR) and dry immersion (DI) have provided possibilities for long-term exposures with findings closest to those seen with a weightless state. They produce changes in body composition (including body fluid redistribution), cardiovascular and skeletal muscle characteristics that resemble the effects of microgravity. The common physiological denominator is the combination of a cephalad shift of body fluids and reduced physical activity. Unlike bed rest, dry immersion provides a unique opportunity to study the physiological effects of the lack of a supporting structure for the body. Dry immersion means immersing into the thermoneutral water covered with special elastic free floating waterproof fabric. The subject, surrounded by film and free suspended in the water mass, remains dry. During horizontal immersion, pressure forces are distributed nearly equally around the entire surface of the body (only the head and neck are not entirely supported by water). The absence of mechanical support of specific zones during immersion creates a state akin to weightlessness that is called supportlessness. Physiological changes under DI develop more rapidly and are more profound than under HDBR. This advanced ground-based model is extremely suited to test countermeasures for microgravity-induced deconditioning and physical inactivity-related pathologies. The present study is organized in this context by the French space agency (CNES) to assess on twenty healthy male volunteers the effects of thigh cuffs to prevent the deconditioning induced by 5 days of dry immersion and in particular the fluid shift and its related ophthalmological disorders. Using an integrated approach, the CNES has selected ten scientific protocols to assess the changes in the different physiological fields and the potential beneficial effects of the countermeasure to prevent and/or reduce these changes.

Official Title
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Effects of Thigh Cuffs to Prevent the Deconditioning Induced by 5 Days of Dry Immersion Used as a Ground-based Model to Study the Effects of Weightlessness

Conditions
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Weightlessness, Weightlessness; Adverse Effect

Intervention / Treatment
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* Other: Dry immersion Control Group
* Other: Thigh cuffs intervention


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Healthy male volunteer (see below the description of medical tests and laboratory analysis performed at the selection visit), Age 20 to 45, No overweight nor excessive thinness with BMI (weight Kg/ height m2) between 20 and 26, Height between 158 and 185 cm, No personal nor family past record of chronic or acute disease or psychological disturbances which could affect the physiological data and/or create a risk for the subject during the experiment, Fitness level assessment: if age < 35 years: 35 ml/min/kg < VO2max < 60ml/min/kg if age > 35 years: 30 ml/min/kg < VO2max < 60ml/min/kg Walking between 7000 - 8000 steps/day, Active and free from any orthopedic (in particular no vertebral fracture, scoliosis or herniated disc) musculoskeletal and cardiovascular disorders, Non smokers, No alcohol, no drug dependence and no medical treatment, No antibiotic treatment in the 2 previous months before the beginning of the study, Covered by a Social Security system, Have signed the information consent, Free of any engagement during the study. Exclusion Criteria: - Past record of orthostatic intolerance, Cardiac rhythm disorders, Chronic back pains, Vertebral fracture, scoliosis or herniated disc, Glaucoma, HTA, History of migraines, History of hiatus hernia or gastro-esophageal reflux, History of thyroid dysfunction, renal stones, diabetes, History of head trauma, Past records of thrombophlebitis, family history of thrombosis or positive response in thrombosis screening procedure (anti thrombin III, S-protein, C-protein, factor V Leiden mutation and the mutation 20210 of the prothrombin gene), Individuals exhibiting mutations involved in hereditary hemochromatosis (HAMP, HFE, HFE2, SCL40A1 and TRF2), Abnormal result for lower limbs echo-doppler, History or active claustrophobia, History of genetic muscle and bone diseases of any kind, Bone mineral density: T-score ≤ -1.5 on the hip, Osteosynthesis material, presence of metallic implants or any other contra-indication for MRI, Poor tolerance to blood sampling, Having given blood (more than 8ml/kg) in a period of 8 weeks or less before the start of the experiment, Antibiotic treatment in the 2 previous months before the beginning of the study, Vegetarian or vegan, History of food allergy, Positive reaction to any of the following tests: HVA IgM (hepatitis A), HBs antigen (hepatitis B), anti-HVC antibodies (hepatitis C), anti-HIV1+2 antibodies, Subject already participating or in the exclusion period of a clinical research, Refusal to give permission to contact his general practitioner, Incarcerated persons, Subject who, in the judgment of the investigator, is likely to be non-compliant during the study, or unable to cooperate because of a language problem or poor mental development, Subject who has received more than 4500 Euros within 12 months for being a research subject. Subject under guardianship or trusteeship.

Ages Eligible for Study
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Minimum Age: 20 Years
Maximum Age: 45 Years

Sexes Eligible for Study
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Male

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Parallel Assignment
Interventional Model Description: A monocentric open parallel randomized and controlled study.
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Dry immersion Control Group<br>5 days of dry-immersion | Other: Dry immersion Control Group<br>* Subjects are immersed up to the neck for 5 days in a specially designed bath filled with tap water.<br>|
| Experimental: Thigh Cuffs intervention<br>5 days of dry-immersion with thigh cuffs | Other: Thigh cuffs intervention<br>* Subjects are immersed up to the neck for 5 days in a specially designed bath filled with tap water. During the 5 days of dry immersion, the subjects will wear the thigh cuffs daily for 10 hours during the day (8 am to 6 pm). Thigh cuffs are strips of fabric with inserts of elastic fabric. Different sizes exist to adapt to different thighs. Each cuff has five tightening positions (from 1 to 5) and they will be tightened at the upper third of the thighs to create an occlusion pressure of about 30 mmHg.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in optic nerve sheath diameter (ONSD) considered as an indirect marker for intracranial pressure (ICP) estimation | The optic nerve sheath diameter (ONSD) variations will be measured by echography. | Baseline and five days of dry-immersion | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in the optic nerve fibers thickness | Thickness of the optic nerve fibers will be measured by Optical Coherence Tomography (OCT) | Baseline and five days of dry-immersion | 
| Change in cerebral structures and in venous circulation of the brain by MRI | Visualization of cerebral structures and intracranial venous system will be performed by MRI coupled with injection of gadolinium | Baseline and five days of dry-immersion | 
| Change in cerebral perfusion | Cerebral perfusion will be assessed by HMPAO scintigraphy | Baseline and five days of dry-immersion | 
| Change in intraocular pressure. | Intra ocular pressure (IOP) will be measured by applanation tonometry | Baseline and five days of dry-immersion | 
| Change in orthostatic tolerance | Orthostatic tolerance will be assessed during a Lower Body Negative Pressure test (LBNP test) | Baseline and five days of dry-immersion | 
| Change in body fluid compartments by bioelectrical impedance analysis | Extracellular, intracellular and total body water will be estimated by bioimpedance | Baseline and during five days of dry-immersion | 
| Change in circadian rhythms of blood pressure | Continuous 24-h recording of blood pressure will be performed by SOMNOtouch™ NIBP system designed for ambulatory continuous measurements | Baseline and during the five days of the dry-immersion period | 
| Measurement of the fluid shift towards the cephalic region by ultrasound | The hemodynamic and morphologic consequences of the fluid shift on the cephalic organs (thyroid, eyes), cephalic blood vessels (jugular vein, carotid, femoral, middle cerebral vein) will be investigated by ultrasound | The first day to quantify the short term effect and the fourth day of dry-immersion to quantify the long term effect of fluid shift | 
| Change of whole-body and skeletal muscle metabolic flexibility (i.e. capacity to adapt fuel oxidation to fuel availability) | Whole-body metabolic flexibility will be measured through the changes in respiratory quotient (RQ) from fasting state to postprandial state induced by high-carbohydrate standard meal, Skeletal muscle metabolic flexibility will be assessed in primary cell culture (cell isolation from biopsies of the vastus lateralis muscle). | Baseline and 4 days of dry-immersion | 
| Change in expression pattern of atrophic and phenotypic modifiers in skeletal muscle | Vastus Lateralis needle biopsies will be performed before and at the end of the 5 days of dry-immersion. The expression pattern of many proteins implied in the regulation of skeletal muscle homeostasis will be studied using biochemical technics.The contractile proteome will be investigated by analyzing the phenotype expression of myosin isoforms (heavy-MHC and light-MLC chains), regulatory proteins, i.e. troponin (TnI,TnC and TnT) and tropomyosin isoforms, main proteins implied in the sarcoplasmic reticulum function i.e. Ca-ATPase SERCA and Ca leakage channel RyR (primary antibodies from Sigma, Cell Signalling, Millipore). | Baseline and 5 days of dry-immersion | 
| Change in muscle transcriptome profile | Vastus Lateralis needle biopsies will be performed before and at the end of the 5 days of dry-immersion. The muscle gene expression will be analyzed by microarray technology | Baseline and 5 days of dry-immersion | 
| Measurement of muscle contractile properties using skinned fibers | Vastus Lateralis needle biopsies will be performed before and at the end of the 5 days of dry-immersion. Skinned fibers will be prepared by processing in skinning solution. Maximal tension and calcium affinity of single skinned fibers will be assessed using tensiometry. | Baseline and 5 days of dry-immersion | 
| Measurement of fat cell invasion into skeletal muscle | Vastus Lateralis needle biopsies will be performed before and at the end of the 5 days of dry-immersion. The expression of markers related to adipocytes structure and function (PPAR-γ, CEBP-α,CEBP-δ, lipoprotein lipase, ACLP, adipsin, leptin, adiponectin, FABP4, UCP1, IL6, IL15, CD36, GLUT4)will be quantified by RT-qPCR and western blotting. Additionally, the CD34+CD15+CD56- specific adipogenic progenitors of skeletal muscle will be quantified by RT-qPCR and western blotting. | Baseline and 5 days of dry-immersion | 
| Change in the balance of bone remodeling markers | Concentration of bone formation markers [bone-specific Alkaline Phosphatase (bAP), procollagen type I N-terminal propeptide (P1NP), total osteocalcin, uncarboxylated and carboxylated osteocalcin] and of bone resorption markers [C-terminal cross-linked telopeptide of type I collagen (CTx)] will be analyzed by automated chemiluminescence immunoassay or by enzyme-immunoassay kits. | Baseline, during and after 5 days of dry-immersion | 
| Change in the composition of the intervertebral disc (IVD). | The concentration of glycosaminoglycan (GAG) and water in the IVD will be measured by MRI with spectroscopy (MRS) | Baseline and 5 days of dry-immersion | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Simulated Microgravity, Weightlessness, Countermeasure, Dry immersion, Supportlessness