Countermeasure Evaluation
Conditions
Brief summary
The human being has shown that he can live and work in the space environment, but due to the lack of essential mechanical load on muscle and bone, the fluid-shift as well as alterations in the acid-base balance (mainly on account of nutritional factors), the exposure to microgravity results in a gradual degradation of muscle, bone and cartilage, deconditioning of the cardiovascular system and metabolic changes. Countermeasures to prevent all the deconditioning of the physiological systems are not yet fully effective and require further investigation. A commonly utilized model of simulating the physiological effects of microgravity on the human organism on ground is the 6° head-down-tilt bed rest. In the present study the model has been used to study potential countermeasures to spaceflight-associated deconditioning. One of the most constrictive changes appearing during space flight as well as during bed rest, are disuse-induced muscle losses. These are associated with a decrease in muscle protein synthesis, rather then an increase in muscle protein breakdown. Besides an effective training countermeasure, nutritional countermeasures gain respect in this context: supplementing conventional diets with whey protein or essential amino acids has been shown to increase muscle protein synthesis. Due to these anabolic properties whey protein seems promising to counteract disuse-induced muscle wasting. Drawbacks of a high protein intake are calciuric effects, ascribed to the proton-release when metabolizing sulfur-containing amino acids. The so called 'low grade metabolic acidosis' has also shown to activate osteoclastic bone resorption and muscle protein degradation. Therefore, to maximize the anabolic potential of a whey protein supplementation, the acidogenic properties need to be compensated. As previous works suggest, a shift of acid base balance into the acid direction and the resulting changes in bone and protein turnover may be hindered by supplementing alkaline mineral salts. In this regard, a mid-term bed rest study was performed in order to investigate the effect of a combined whey protein (0.6 g/kg body weight/day) and potassium bicarbonate (90 mmol/day) supplementation as a potential countermeasure to multiple physiological and metabolic alterations on the human body resulting from real and simulated microgravity.
Interventions
DIETARY_SUPPLEMENTWhey Protein + Potassium bicarbonate
0.6 mmol WP/kg body weight + 90 mmol KHCO3 during bed rest
OTHERControl
Bed rest without dietary supplement
Sponsors
European Space Agency
University Hospital, Clermont-Ferrand
Institut Pluridisciplinaire Hubert Curien, Strasbourg, France
Charite University, Berlin, Germany
University of Milan
Université de Nice Sophia Antipolis
University of Ottawa
Manchester Metropolitan University
University of Toronto
Medical University of Graz
University of Cologne
Radboud University Medical Center
University Hospital, Lille
Leiden University Medical Center
DLR German Aerospace Center
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
TREATMENT
Masking
NONE
Eligibility
Sex/Gender
MALE
Age
20 Years to 45 Years
Healthy volunteers
Yes
Inclusion criteria
* Healthy males, 20 -45 years * BMI: 20 - 25 kg/m2 * Height: 158 - 190 cm * Weight: 65 - 85 kg * maximum relative oxygen uptake: 30 - 60 ml/min/kg * non-smokers * successful medical and psychological screening * Willingness to participate in the entire study * signed informed consent * social insurance * Clear criminal background check
Exclusion criteria
* Abuse of drugs, medicine or alcohol * Vegetarians, Vegans * Migraines * History of mental illness * Claustrophobia * History of: thyroid dysfunction, renal stones, diabetes, allergies, hypertension, hypocalcaemia, uric acidaemia, lipidaemia, hyperhomocysteinaemia * Rheumatism * Muscle-, Cartilage- or Joint Injuries * Gastro-esophageal reflux disease, renal function disorder, Hiatus hernia * Chronic back pain * Bone diseases * Herniated discs * Achilles tendon injuries * Cruciate ligament rupture or any other severe knee injury * BMD more than 1.5 SD \< t-score * History of orthostatic intolerance or vestibular disorders * Anaemia * Vitamin D Deficiency * Positive response in thrombosis screening * Use of metallic implants, osteosynthesis material * Porphyria, Blood dyscrasia * HIV, Hepatitis * Increased Inner Eye pressure * Intolerance to local anesthetics * Participation in another study up to three month before study onset
Design outcomes
Primary
| Measure | Time frame |
|---|---|
| Change in body composition | Baseline, after 21 days of bed rest |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Headache - frequency and quality | Baseline, daily during 21 days of bed rest | — |
| Hematopoetic system | Baseline, after 10, 21 days of bed rest, 1, 28 days after finishing bed rest | Blood cell count, reticulocytes, Haptoglobin, Bilirubin, Ferritin, EPO, Thrombopoietin, Urinary Urobilinogen and Fecal Urobilinogen (markers of blood cell degradation) |
| Fat accumulation in bone marrow | Baseline, after 10, 21 days of bed rest, 3, 28 days after finishing bed rest | — |
| Sympathetic activity during orthostatic stress | Baseline, after 21 days of bed rest | Muscle sympathetic nerve activity is measured by MSNA recording by microneurography technique. |
| Visual Orientation | Baseline, after 6,12,20 days of bed rest, 2,4 days after finishing bed rest | Visual Orientation is assessed by 'Oriented Character Recognition Test' and Luminous Line Test. The main parameter is Score. |
| Plasma galanin and adrenomedullin responses during head up tilt test (orthostatic stress) | Baseline, after 21 days of bed rest | — |
| Plasma Volume | Baseline, after 21 days of bed rest | — |
| Maximum volume of oxygen uptake | Baseline, after 21 days of bed rest | — |
| Isometric torque | Baseline, after 21 days of bed rest | During a an Isometric Maximum Voluntary Contraction Test on the knee extensors & flexors, the plantarflexors and dorsiflexors, the elbow extensors & flexors the Isometric Torque will be measured in Nm. |
| Muscle fatigue | Baseline, after 21 days of bed rest | — |
| Bone metabolism | Baseline, after 2,5,14,21 days of bed rest, 1, 5, 14, 28 days after finishing bed rest | — |
| Bone mineral density + content | Baseline, after 21 days of bed rest | — |
| Standing balance | Baseline, after 21 days of bed rest | — |
| Locomotion | Baseline, after 21 days of bed rest | Locomotion will be assessed by Dynamic Gait Index, specific parameters are: total Score and Subscore |
| Achilles tendon structure | Baseline, after 21 days of bed rest, 2, 28 days after finishing bed rest | — |
| Intracranial pressure | Baseline, after 1,4, 7,10,13,14,15,16,17,18,19,20,21 days of bed rest,1,2,4 days after finishing bed rest | — |
| Monitoring of Vitamin K status | Baseline, after 2,5,14,21 days of bed rest, 1, 5 days after finishing bed rest | — |
| Fat metabolism | Baseline, after 21 days of bed rest | — |
| Glucose metabolism | Baseline, after 21 days of bed rest, 4 days after finishing bed rest | — |
| Nitrogen balance | Daily for a duration of 33 days | — |
| Energy metabolism | Baseline, after 21 days of bed rest | — |
| Glucocorticoid activity | Baseline, after 2,3,7,8,12,13,16,17 days of bed rest, 2,3 days after finishing bed rest | — |
| Muscle metabolism | Baseline, after 21 days of bed rest | — |
| Acid base balance | Baseline, after 2, 14, 21 days of bed rest, 5 days after finishing bed rest | — |
| Cartilage metabolism and -thickness | Baseline, after 2,3,5,7,14,21 days of bed rest, 5 days after finishing bed rest | — |
| Muscle volume | Baseline, after 20, 21 days of bed rest, 3 days after finishing bed rest | — |
| Free water and fat content in muscle | Baseline, after 20, 21 days of bed rest, 3 days after finishing bed rest | — |
| Orthostatic tolerance | Baseline, after 21 days of bed rest | Orthostatic tolerance will be assessed by Head up tilt test. The following parameters are assessed to measure orthostatic tolerance: beat-to-beat heart rate \[bpm\], beat-to-beat blood pressure \[bpm\] time to presyncope \[min, s\] |
| Body mass | Daily for a duration of 35 days | — |
Countries
Germany
Outcome results
None listed