Muscle Mass During Space Exploration
| Status: | Completed |
|---|---|
| Conditions: | Orthopedic |
| Therapuetic Areas: | Orthopedics / Podiatry |
| Healthy: | No |
| Age Range: | 45 - 60 |
| Updated: | 12/6/2017 |
| Start Date: | August 2009 |
| End Date: | April 2015 |
An Integrated Low-Volume Nutritional Countermeasure to Maintain Muscle Mass and Function During Space Exploration
The investigators will test the following hypotheses:
1. 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.
2. 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.
1. 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.
2. 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.
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.
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.
Inclusion Criteria:
1. Age between 45-60
2. Ability to sign informed consent
Exclusion Criteria:
1. Subjects with cardiac abnormalities considered exclusionary by the study physicians
2. Subjects with uncontrolled metabolic disease
3. A GFR <65 mL/min/1.73m2 or evidence of kidney disease or failure
4. Subjects with vascular disease or risk factors of peripheral atherosclerosis
5. Any history of hypo- or hyper-coagulation disorders. (e.g., Coumadin use or history of
DVT or PE)
6. Subjects with chronically elevated systolic pressure >150 or a diastolic blood
pressure > 100
7. Subjects with implanted electronic devices (e.g., pacemakers, electronic infusion
pumps, stimulators)
8. Subjects with recently (6 months) treated cancer other than basal cell carcinoma
9. Any subject currently on a weight-loss diet or a body mass index > 30 kg/m2
10. Inability to abstain from smoking for duration of study
11. A history of > 20 pack per year smoking
12. Any subject that is HIV-seropositive or has active hepatitis
13. Recent anabolic or corticosteroids use (within 3 months)
14. Subjects with hemoglobin or hematocrit lower than accepted lab values
15. Agitation/aggression disorder
16. History of stroke with motor disability
17. A recent history (<12 months) of GI bleed
18. Any other condition or event considered exclusionary by the PI and faculty physician
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