The Effects of Exercise Versus Inactivity on People With Mitochondrial Muscle Disease

Mitochondrial myopathies are caused by mutant mitochondrial DNA, genetic defects in parts of
the mitochondrial DNA. These defects can include missing or deleted DNA that typically codes
for certain proteins involved in energy production. These mutations cause individual
mitochondria and the body on a whole to produce energy less efficiently. Because muscle
cells require extensive energy to function properly, they are particularly impaired by
mitochondrial dysfunction. The onset of most mitochondrial myopathies occurs before the age
of 20. Initially a person may experience muscle weakness and fatigue during physical
activity. Other symptoms may include limited eye mobility, heart arrhythmias, slurred
speech, swallowing difficulties, and impaired movement.

There is no cure yet for mitochondrial myopathies, nor is there any adequate treatment to
stall disease progression. Exercise, known to boost the production and function of
mitochondria in healthy people, may reduce symptoms in people with mitochondrial myopathies
by increasing the number and function of normal mitochondria in an individual muscle cell.
The purpose of this study is to determine the effects of exercise training versus inactivity
on the expression of normal and mutant mitochondrial DNA and on mitochondrial production
within muscle cells in people with mitochondrial myopathies. The study will also assess how
cell function, physical endurance, heart function, and quality of life are affected by
exercise training and inactivity.

Participants in this 2-year study will first undergo physiological exercise testing,
magnetic resonance imaging (MRI) of heart and skeletal muscles, a needle biopsy of muscle,
and a questionnaire on quality of life. Participants will then be randomly assigned to
partake in regular exercise training or no training for 6 months. After 6 months, all
participants will undergo repeat testing of initial evaluations. Participants who had been
in the exercising group will then switch to no exercise training for 6 months, and
participants who had been in the non-exercising group will switch to regular exercise
training for 6 months. The second 6-month period will also be followed by repeat testing of
initial evaluations. Participants will then be encouraged to continue exercise training for
an additional 1 year, with retesting at the end of the second year. Each of the four
evaluations will take about 15 hours over 5 days.

Inclusion Criteria:

- Diagnosis of mitochondrial myopathy

- Single-large scale deletions of mitochondrial DNA

- Point mutations in mitochondrial DNA

Exclusion Criteria:

- Symptoms or electrocardiogram-generated signs of coronary artery disease

- Symptoms of congestive heart failure; peripheral vascular disease; or lung, kidney,
or liver disease

- History of alcohol or substance abuse

- Metal implants or related devices that contraindicate MRI

- Current use of or require any medications that have significant systemic
cardiovascular effects

- Diabetes

- Obesity (body mass index [BMI] greater than 30)

- Resting systolic blood pressure greater than 140 mmHg and/or diastolic blood pressure
greater than 90 mmHg at three different times