Medium-term Bedrest Whey Protein (MEP)

DLR German Aerospace Center10 enrolled

Overview

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.

Study Type

INTERVENTIONAL

Allocation

RANDOMIZED

Eligibility

Sex: MALEMin age: 20 YearsMax age: 45 YearsHealthy volunteers:

Medical Language ↔ Plain English

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

Outcomes

Primary Outcomes

Change in body composition

Time frame: Baseline, after 21 days of bed rest

Secondary Outcomes

Plasma Volume

Time frame: Baseline, after 21 days of bed rest

Maximum volume of oxygen uptake

Time frame: Baseline, after 21 days of bed rest

Isometric torque

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.

Time frame: Baseline, after 21 days of bed rest

Muscle fatigue

Time frame: Baseline, after 21 days of bed rest

Bone metabolism

Time frame: Baseline, after 2,5,14,21 days of bed rest, 1, 5, 14, 28 days after finishing bed rest

Bone mineral density + content

Time frame: Baseline, after 21 days of bed rest

Standing balance

Time frame: Baseline, after 21 days of bed rest

Locomotion

Locomotion will be assessed by Dynamic Gait Index, specific parameters are: total Score and Subscore

Time frame: Baseline, after 21 days of bed rest

Body mass

Time frame: Daily for a duration of 35 days

Intracranial pressure

Time frame: 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

Time frame: Baseline, after 2,5,14,21 days of bed rest, 1, 5 days after finishing bed rest

Fat metabolism

Time frame: Baseline, after 21 days of bed rest

Glucose metabolism

Time frame: Baseline, after 21 days of bed rest, 4 days after finishing bed rest

Nitrogen balance

Time frame: Daily for a duration of 33 days

Energy metabolism

Time frame: Baseline, after 21 days of bed rest

Glucocorticoid activity

Time frame: Baseline, after 2,3,7,8,12,13,16,17 days of bed rest, 2,3 days after finishing bed rest

Muscle metabolism

Time frame: Baseline, after 21 days of bed rest

Acid base balance

Time frame: Baseline, after 2, 14, 21 days of bed rest, 5 days after finishing bed rest

Sympathetic activity during orthostatic stress

Muscle sympathetic nerve activity is measured by MSNA recording by microneurography technique.

Time frame: Baseline, after 21 days of bed rest

Visual Orientation

Visual Orientation is assessed by 'Oriented Character Recognition Test' and Luminous Line Test. The main parameter is Score.

Time frame: Baseline, after 6,12,20 days of bed rest, 2,4 days after finishing bed rest

Plasma galanin and adrenomedullin responses during head up tilt test (orthostatic stress)

Time frame: Baseline, after 21 days of bed rest

Cartilage metabolism and -thickness

Time frame: Baseline, after 2,3,5,7,14,21 days of bed rest, 5 days after finishing bed rest

Hematopoetic system

Blood cell count, reticulocytes, Haptoglobin, Bilirubin, Ferritin, EPO, Thrombopoietin, Urinary Urobilinogen and Fecal Urobilinogen (markers of blood cell degradation)

Time frame: Baseline, after 10, 21 days of bed rest, 1, 28 days after finishing bed rest

Fat accumulation in bone marrow

Time frame: Baseline, after 10, 21 days of bed rest, 3, 28 days after finishing bed rest

Achilles tendon structure

Time frame: Baseline, after 21 days of bed rest, 2, 28 days after finishing bed rest

Headache - frequency and quality

Time frame: Baseline, daily during 21 days of bed rest

Muscle volume

Time frame: Baseline, after 20, 21 days of bed rest, 3 days after finishing bed rest

Free water and fat content in muscle

Time frame: Baseline, after 20, 21 days of bed rest, 3 days after finishing bed rest

Orthostatic tolerance

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 \[min, s\]

Time frame: Baseline, after 21 days of bed rest

Medium-term Bedrest Whey Protein (MEP)

Overview

Conditions

Interventions

Eligibility

Locations (1)

Outcomes

Primary Outcomes

Secondary Outcomes