Noninvasive measurements of mitochondrial capacity in skeletal muscle of patients with Friedreich’s ataxia could be used to monitor disease severity and progression, according to a recent study.
In contrast, the study failed to find a link between mitochondrial capacity or muscle endurance to perceptions of fatigue.
The study, “Mitochondrial capacity, muscle endurance & low energy in friedreich ataxia,” was published in the journal Muscle & Nerve.
Fatigue in Friedreich’s ataxia is difficult to measure with tools that are not adapted to the disease. Questionnaires investigating fatigue may include factors that are typical of Friedreich’s ataxia, and not necessarily a fatigue symptom. Also, in Friedreich’s ataxia, fatigue may be more related to physical than mental factors.
Researchers at the University of Georgia figured that by using measurements of mitochondrial capacity and muscle endurance, it may be possible to assess both disease severity and the level of fatigue in patients.
The research team recruited 16 Friedreich’s ataxia patients and 10 able-bodied people as controls, and assessed mitochondrial capacity by near-infrared spectroscopy (NIRS). The method measures the recovery of oxygen consumption after electrical stimulation. In addition, muscle endurance was measured with surface mechanomyography.
Participants also completed questionnaires that aimed to assess perceptions of energy and fatigue as well as physical activity in the week prior to the study.
While no differences were seen in the mitochondrial capacity between patients and controls, patients had lower levels of endurance than controls.
There were also no differences between patients and controls in the levels of mental energy, but patients had significantly lower physical energy levels. Despite expectations, the study showed no links between mitochondrial capacity or muscle endurance and scores of energy levels or fatigue. But mitochondrial capacity and muscle endurance were seen to be correlated.
In contrast, the levels of mitochondrial capacity mirrored the levels of physical disability. This suggests that such measurements may be used to track disease severity and progression. This noninvasive approach is particularly suitable for repeated measurements.
Researchers noted that the lack of differences in mitochondrial capacity and muscle endurance between the groups may reflect that the testing was performed on forearm muscles. Most studies focus on leg muscles, which are often more affected in Friedreich’s ataxia.