Data Suggests Positive Impact of Endurance Training in HD Patients

Data published in the Orphanet Journal of Rare Diseases suggests that endurance training could have a positive impact in Huntington’s disease (HD) patients, much like it has in anyone else.

Sandro Manuel Mueller of the Department of Neurology at the University Hospital Zurich in Switzerland and a team of Swiss researchers have found that such training could potentially assist in delaying muscular dysfunction in patients. The study, “Effects of endurance training on skeletal muscle mitochondrial function in Huntington disease patients” suggests that abnormal functioning of mitochondria in the skeletal muscle may be a pathogenic factor in HD.

HD, a neurodegenerative disease, is the result of an unstable cytosine-adenine-guanine (CAG) repeat expansion in the Huntingtin gene, which leads to the production of a mutant form of the huntingtin protein. It is characterized by a combination of motor, cognitive and psychiatric issues that typically present in a person’s 3rd or 4th decade of life.

Current treatment options are limited to the relief of symptoms, but at present, there is no treatment to prevent or attenuate disease progression.

In the study, 13 HD patients and 11 healthy controls completed 26 weeks of endurance training. Muscle biopsies were obtained from M. vastus lateralis before and after the training phase, and mitochondrial respiratory chain complex activities, mitochondrial respiratory capacity, capillarization, and muscle fiber type distribution were determined from the samples.

Because physical activity has been proven to improve mitochondrial function in healthy subjects, it was assumed that endurance training could also increase peak oxygen uptake and provide benefit, improving coordination, gait and motor symptoms experienced by HD patients. It was hypothesized by the study’s investigators that while HD patients have impaired mitochondrial function in the skeletal muscle, endurance exercise could improve it to a similar extent as in healthy controls.

Throughout the endurance training intervention, an increase in mass-specific mitochondrial respiratory capacity was very apparent in HD patients. Overall capillary-to-fiber ratio increased in HD patients by 8.4% and in healthy controls by 6.4% during the endurance training intervention.

When comparing the two, skeletal muscle mitochondria of HD patients are as responsive to an endurance training stimulus as in healthy controls. Additionally, an increase in mass-specific mitochondrial respiratory capacity was present in HD patients during the endurance training intervention. While it appears endurance training is a safe and practical option to enhance indices of energy metabolism in skeletal muscle of HD patients, further evidence of the benefits of exercise in the skeletal muscle of HD patients is still necessary.

With more research, however, it is possible that endurance training could represent a promising therapeutic approach to delay the onset, and potentially the progression, of muscular dysfunction in this indication.

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