Low mitochondrial content

Mitochondria are found in most cells, and their main job is to generate chemical energy. Disorders of mitochondrial function are implicated in a number of diseases, including mental disorders and heart problems, as well as being involved in the ageing process. Since ME/CFS is characterised by a profound, generalised, post-exertional loss of muscle power, it seems reasonable to suggest that mitochondrial dysfunction may be involved.

The most recent mitochondrial study from the Neuromuscular Centre in Nijmegen compares skeletal muscle biopsies from 16 people with ME/CFS plus symptoms of muscle pain and/or exercise intolerance to those of 11 healthy controls. The group also measured mitochondrial respiratory chain complex (RCC) activity – an indication of mitochondrial function – by comparing biopsy data from the ME/ CFS patients with two groups of patients with genetically confirmed mitochondrial disorders (22 people with chronic progressive external ophthalmoplegia, and 27 with an A3243G mutation in skeletal muscle).

The researchers found that citrate synthase activity (a marker of mitochondrial content) was decreased in ME/CFS compared to healthy people. However, the activity of the RCC enzymes (and hence energy production) of ME/CFS patients was not at the low levels found in patients with mitochondrial disorders who generally have deficiencies in the RCCs as part of their illness. Furthermore, the energy (ATP) production rate was within the normal range in all ME/CFS patients, whereas it was decreased greatly in three quarters of the patients with mitochondrial disorders.

The fact that mitochondrial function was unaffected in the skeletal muscle of ME/ CFS patients, but that mitochondrial content was notably decreased does not support the concept of “primary mitochondrial dysfunction” in ME/CFS, as the authors point out. However, they speculate that “low mitochondrial content might be a perpetuating factor for complaints such as fatigue, myalgia and exercise intolerance” in the illness.

Reference: Mitochondrial enzymes discriminate between mitochondrial disorders and chronic fatigue syndrome. Smits B et al. Mitochondrion 2011 Sep; 11(5): 735-8.

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