PhD Program in Space Life Science Muscle Performance in Long-Term Spaceflight: Challenges Facing the U.S. Space Program Michael B. Reid, Ph.D. Department.

PhD Program in Space Life Science

Muscle Performance in Long-Term Spaceflight: Challenges Facing the U.S. Space Program

Michael B. Reid, Ph.D.Department of PhysiologyUniversity of Kentucky Medical Center


NASA’s Mandate for the Future:Into The Cosmos

“We do not know where this journey will end, yet we know this: Human beings are headed

into the cosmos.” - President George W. Bush January, 2004


The NASA Response:Vision for the Future

The Vision for Space Exploration Manned spaceflight Complete the ISS by 2010 Return to the moon by 2020 Prepare for Mars mission

Courtesy of NASA


The NASA Vision:

Long-Duration Missions

NASA’s plans for long-duration missions1. ISS

2. Establish as lunar base for technical development for equipment and instrumentation

3. Mars probes

4. Mars

Courtesy of NASA

Mars Probe

Lunar Base

Mars

ISS


The NASA Concern:

Maintaining Crew Health in Space

Aspects of long-term space flight Harsh environment Confined space Life support issues Adaptation to 0 Gz

Courtesy of NASA


National Space Biomedical Research Institute (NSBRI)

Formed in 1997 NSBRI research seeks

solutions to health concerns facing astronauts on long missions. Patients on Earth suffering from similar conditions will benefit from these advances.

www.nsbri.org

12 consortium institutions ~270 investigators 7 research areas including:

Cardiovascular Alterations Human Factors and

Performance Musculoskeletal Alterations Neurobehavioral and

Psychosocial Factors Radiation Effects Sensorimotor Adaptation Smart Medical Systems

and Technology


Muscle Research in Microgravity

Human Studies In Flight Challenge: transport

exercise equipment to ISS and keep it functioning

Treadmill Cycle ergometer Body mass measurement

device Standardized force used

to measure inertial changes

Calculates changes in body mass while in orbit

Body mass measurement device

Treadmill Cycle ergometer

Courtesy of NASA


Muscle Research in MicrogravityHuman Muscle Ultrastructure Electron micrographs of

longitudinal sections of slow muscle fibers obtained from soleus muscles of an astronaut before (A) and after (B) a 17-day spaceflight

Structural changes of post flight muscle fiber: Skeletal structure Z-line streaming Loss of thin filaments Increases accumulation of

lipid droplets Changes in mitochondrial

morphology

Reproduced from Fitts RH, et al. Physiology of a microgravity environment; invited review: microgravity and skeletal muscle. J Appl Physiol 89:823-839, 2000.


Muscle Research in Microgravity:Human Muscle Endurance Effect of space flight on limb

muscle endurance in Sprague-Dawley rats

Muscle endurance is compromised 6 days after flight

Loss in muscle strength overtime

Reproduced from Caiozzo V.J., et al. Effect of spaceflight on skeletal muscle: mechanical properties and myosin isoform content of a slow muscle. J Appl Physiol 76:1764-1773, 1994.


Muscle Research in Microgravity:Human Muscle Weakness Loss in muscle strength

over time Comparison of mean

percent changes in planar and dorsal flexion isokinetic strengths (0-180°/s) between 110 (▲) and 237 (●) days of exposure to microgravity.

Progressive adaptation of microgravity differs depending on muscle groups

Reproduced from Greenleaf JE, et al. Exercise-training protocols for astronauts in microgravity. J Appl Physiol 67: 2191–2204, 1989.


Muscle Research in Microgravity:Rodent Studies In Flight

Study of non-human species in space (i.e. rats) Rodent chambers

Unable to display images


Muscle Research in Microgravity:Fiber Atrophy in Rats vs. Men Percent change in

fiber cross-sectional area preflight compared with post flight for slow type I and fast II fibers from the rat soleus (Sol), medial gastrocnemius (MG), and tibialis anterior (TA) and from the human vastus lateralis (VL), Sol, and gastrocnemius

Reproduced from Fitts, et al. J Appl Physiol 89: 823-839, 2000.


Muscle Research in Microgravity:Limitations of the Approach

Few subjects or animals available Many restrictions on access

time restraints cooperation

Technical limits in-flight In-flight studies useful for proof-of-

concept only, not systematic research.

Courtesy of NASA


Ground-Based Research Models:The NASA KC-135 “Vomit Comet”

Ground-based model Location: Ellington Field

(Texas) Used to make selected

types of measurements

Courtesy of NASA


Ground-Based Research Models:Limitations of the Vomit Comet

Flies over the Gulf of Mexico in a parabolic curve

20-sec exposures Limited access Nausea! The diagram to the right

shows a flight plan for the KC-135 during typical zero-g maneuvers

Courtesy of NASA


Ground-Based Research Models:

Bedrest Studies Used to measure human

response to countermeasures

Healthy volunteers 4-8 weeks or more in bed Measure muscle function

and learn how muscle is adapting Courtesy of NASA



Exercise and Atrophy in Bedrest Resistance exercise of

volunteers in bed rest Fiber diameter changes slowly

over 60 days Resistance exercise is protective

against loss of muscle function Graph to right: Quadriceps

femoris cross sectional area (CSA) during bed rest for the right (filled symbols) and left (open symbols) leg, for RVE (n=9, triangles and solid line) and Ctrl (n=9, circles and dashed lines)

Graph reproduced from Mulder, et al. Eur J Appl Physiol 97: 706-715, 2006


Ground-Based Research Models:Muscle Catabolism in Bedrest MRI data, cross section of human

thigh before and after bed rest Muscles atrophy is seen clearly in a

bed rest study

Reprinted with permission of John Wiley & Sons, Inc. Ubiquitin ligase gene expression in healthy volunteers with 20-day bedrest. Muscle Nerve 34(4):463-469, 2006. © 2006 Wiley Periodicals, Inc.


Ground-Based Research Models:Muscle Catabolism in Bedrest Ubiquitin – molecular

tag Communicates with

muscle to breakdown protein via 26S proteasome

High amounts of Ubiquitin after bed rest indicate more muscle protein that is tagged for breakdown/loss of muscle mass




Muscle Catabolism in Bedrest

Changes in gene expression related to muscle metabolism

MuRf-1 and atrogin-1: muscle specific E3 proteins that target ubiquitin to proteins that will be degraded

Both are elevated in catabolic state (starvation)



Ground-Based Research Models: Limitations to Bedrest Studies

Subject recruitment Expense Logistics

Courtesy of NASA


Ground-Based Research Models:Hindlimb Unloading in Rodents Animal studies are used as an

alternative to bedrest projects Hindlimb suspension model used for

conditioning antigravity muscles of rodents

Height of hindlimbs are adjusted and do not apply force to antigravity muscles

Rodent muscles adapt to conditions just as human muscles adapt in various models

Unloading induced muscle atrophy mimics microgravity


Ground-Based Research Models:Atrophy and Oxidative Stress in Unloaded Soleus

Oxidant dysregulation and atrophy in unloaded soleus muscle: time course of increases in oxidant activity (fluorescence emissions) and decreases in soleus weight (muscle weight) during 1–12 days of hindlimb unloading.

Rapid loss of muscle mass (day 1-2); rate of decline of muscle levels out around day 5-6

Graph reproduced from: Arbogast, et al., J Appl Physiol 102: 956-964, 2007.


Measurement of free radical activity in cytoplasm of soleus cell Cells have oxidant activity –

reactive oxygen species (ROS), Nitric Oxide and its derivatives

Rapid increase in fluorescence indicates an increase in oxidant activity

Oxidant activity remains elevated during the entire atrophic activity during unloading

Rapid changes in oxidant activity and muscle mass are coincidental

Ground-Based Research Models:Atrophy and Oxidative Stress in Unloaded Soleus

Graph reproduced from: Arbogast, et al., J Appl Physiol 102: 956-964, 2007.



Antioxidant Properties of Bowman-Birk Inhibitor Concentrate (BBIC)

BBIC is made from soybeans and is a serine protease inhibitor

Antioxidant effects Control: no hindlimb

unloading Unloaded: increase in

oxidant activity Unloaded + BBIC: decrease

in oxidant activity with BBIC

Graphs reproduced from: Arbogast, et al., J Appl Physiol 102: 956-964, 2007.


Superoxide reduces cytochrome c

BBIC cuts the signal in half – significant depression in superoxide activity.



Antioxidant Properties of Bowman-Birk Inhibitor Concentrate (BBIC)



BBIC Inhibits Atrophy and Weakness in Unloaded Soleus

3 days of conditioning Unloaded mice fed

BBIC had a drop in muscle cross section and muscle weight

BBIC preserves muscle mass in the absence of exercise training



Relative to control muscles, soleus force is depressed at stimulation frequencies of 50–300 Hz after unloading. BBIC supplementation partially prevents this decrement (unloaded + BBIC).

Graphs reproduced from: Arbogast, et al., J Appl Physiol, 102: 956-964, 2007.


BBIC Inhibits Atrophy and Weakness in Unloaded Soleus


Muscle fatigue occurs during Extravehicular Activity (EVAs)

Story Musgrave - longest serving astronaut MS in Physiology,

University of Kentucky Focus: glove design

and the problems associated with it

Muscle Fatigue During EVA:Other Concerns at JSC

JSC

Story Musgrave

Hubble Space Telescope

Mission Control


Space Suit: Glove Design

Courtesy of NASA

Pressurization stiffens glove Finger dexterity is reduced Causes hand and forearm

fatigue Can limit EVA performance


N-Acetylcysteine (NAC) as a Countermeasure:Isometric Handgrip Exercise Experiment: Isometric handgrip

exercise + Antioxidant N-Acetylcysteine (NAC) as a countermeasure

Evaluate astronauts ability to do work using an Ergometer

Measure changes in handgrip performance in crew members over time

Can we quantitate fatigue effectively? Is NAC an effective countermeasure?

Ergometer


N-Acetylcysteine (NAC) as a Countermeasure:Isometric Handgrip Exercise Can we quantitate fatigue

effectively? Yes Is NAC an effective

countermeasure? Yes Matuszczak Y, Farid M, Jones J,

Lansdowne S, Smith MA, Taylor AA, and Reid MB. Effects of N-acetylcysteine on gluatathione oxidation and fatigue during handgrip exercise. Muscle Nerve 32:633-638, 2005.

Ergometer


N-Acetylcysteine (NAC) as a Countermeasure:Isometric Handgrip Exercise Oxidized glutathione

measured in red blood cells – index of oxidative stress

Right hand exercise Conclusion:

NAC prevents increase of oxidized glutathione during exercise and recovery

NAC works to preserve glutathione homeostasis and blunt oxidative stress

Pre-Med. End-Ex. RecoveryR

BC

GSS

G, m

ol

0

5

10

15

20

25

30

35

Placebo NAC

* *


N-Acetylcysteine (NAC) as a Countermeasure:Isometric Handgrip Exercise Successful handgrip repetitions 3 different control runs

3-7 days apart Endurance increases with

NAC

Sessions

Su

cces

sfu

l R

epet

itio

ns

(% C

1)

0

20

40

60

80

100

120

140

C1 C2 C3 NAC

* *


N-Acetylcysteine (NAC) as Countermeasure:Ongoing Research

Example of a flyer to attract volunteers to test if NAC capsules are a useful countermeasure for the astronaut core


Ground-Based Applications:Space Flight vs. Cachexia Similarities between the clinical

effects of space flight and cachexia among people on earth

Nutritional or pharmacological treatment is needed

Mosby's dictionary of complementary and alternative medicineAuthor: Wayne B Jonas Publisher: Mosby, ©2005.


Similarities in Space Flight vs. Cachexia

Muscle atrophy Regulated by ubiquitin

conjugation Contractile dysfunction

Loss in force / cross-section Muscles are smaller and do

not function as well Oxidative stress

Mediated by reactive oxygen species (ROS)



NAC as Clinical Therapy:Ongoing Research

Pilot study: heart failure patients Test NAC in these patients to

lessen fatigue that decreases mobility, quality of live, increases illness


Comment from the Audience

Many heart failure patients have muscle weakness and it is one of the major problems in moving around. It is a

systemic disease and involves muscle recovery.


Current Model:ROS as Mediators of Muscle Weakness 2 factors that act on a

simplified muscle cell Mechanical unloading and

inflammatory cytokines to increase production of ROS

ROS alter gene expression, increase production of regulatory proteins and stimulate ubiquitin conjugation.

Protein loss – smaller muscles

Muscle weakness is the final result.

Unable to display image of Astronaut Ed Lu being carried by the crowd because he is too weak to walk after he returns following 6 months on the ISS


Unable to display image


NSBRI Muscle Team Long-Term Goal:Countermeasures Effective in Space and on Earth

NSBRI’s goal: Earth based

benefits for people with chronic disease plus astronauts

Mosby's dictionary of complementary and alternative medicineAuthor: Wayne B Jonas Publisher: Mosby, ©2005.Courtesy of NASA

Courtesy of NASA


Acknowledgments

Supported by theNational Institutes of Health &

National Space Biomedical Research Institute

PhD Program in Space Life Science Muscle Performance in Long-Term Spaceflight: Challenges Facing the U.S. Space Program Michael B. Reid, Ph.D. Department.

Documents

phd program

space program michael

skeletal muscle

limb muscle endurance

gz courtesy of nasa

technology slide

muscle strength overtime

mars courtesy of nasa