Muscle Mass During Space Exploration
The investigators will test the following hypotheses:
- Bedrest will blunt the anabolic response to a mixed nutrient meal, facilitating a loss of muscle mass and functional capacity that is only partially restored during rehabilitation.
- Enriching daily meals with leucine will promote protein synthesis and maintain the anabolic response to mixed nutrient meal ingestion. This will preserve lean muscle mass and function during bedrest and facilitate the recovery of functional and metabolic capacity during rehabilitation.
|Study Design:||Allocation: Randomized
Endpoint Classification: Efficacy Study
Intervention Model: Parallel Assignment
Masking: Double Blind (Subject, Investigator)
Primary Purpose: Basic Science
|Official Title:||An Integrated Low-Volume Nutritional Countermeasure to Maintain Muscle Mass and Function During Space Exploration|
- Muscle protein synthesis [ Time Frame: 4 yrs ] [ Designated as safety issue: No ]
|Study Start Date:||August 2009|
|Estimated Study Completion Date:||July 2014|
|Estimated Primary Completion Date:||April 2013 (Final data collection date for primary outcome measure)|
Dietary Supplement: Leucine
3-4g Leucine added to daily meals
|Placebo Comparator: Placebo||
Dietary Supplement: Leucine
Powered amino acid
Other Name: Alanine
Our long-term goal is to identify, prevent and remedy defects in the metabolic pathway that contribute to the loss of muscle mass and function during exposure to microgravity. Demographic data indicate that the average age of shuttle crew members has increased from 40.7 yrs in 1995 to 46.7 yrs in 2007 with an increasing number of astronauts over 50 yrs of age. We contend that the loss of muscle mass and function during spaceflight is facilitated by an age-associated, progressive impairment in the ability to mount an anabolic response to standard mixed nutrient meals. We propose that enriching daily meals with a low-volume leucine supplement will reduce the deleterious effects of microgravity on skeletal muscle and facilitate recovery during rehabilitation.
We will employ our established 14 day bed rest protocol to model the skeletal muscle unloading that occurs during microgravity. We will also examine recovery of muscle mass and functional capacity during a 7 day rehabilitation period. We will study 2 groups: CON (Bedrest/Recovery + Placebo; n=15), LEU (Bedrest/Recovery + Leucine; n=15). We will assess a) markers of translation initiation, b) muscle protein synthesis, c) muscle mass and body composition and d) strength and aerobic capacity.
|United States, Texas|
|The University of Texas Medical Branch|
|Galveston, Texas, United States, 77555|
|Principal Investigator:||Douglas Paddon-Jones, PhD||The University of Texas Medical Branch at Galveston|