Specific variations in the mitochondria DNA genome correlate with an increased likelihood of symptoms in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), according to a study titled “Mitochondrial DNA variants correlate with symptoms in myalgic encephalomyelitis/chronic fatigue syndrome,” published in the Journal of Translational Medicine.
ME/CFS is a rare acquired complex disease characterized by a variety of symptoms, including marked fatigue, headaches, pain, muscle weakness, vision abnormalities, numbness of the extremities (paresthesia), and sleep disorder. The disease’s underlying cause, however, remains unknown, but a significant number of affected people had a previous viral infection, usually a flu-like or upper respiratory illness (of note, ME can occur after a non-viral illness or trauma such as chemical exposure).
Previous studies suggested that dysfunctional mitochondria occur in ME/CFS, but few have investigated how variations in patients’ mitochondria genome associate with health status and/or symptoms. A team of researchers tackled this lack, studying the mitochondrial genomes of a cohort of ME/CFS patients and matched controls of predominantly European origin.
The team focused on the mitochondria genome haplogroup (a genetic population sharing a common ancestor on the patrilineal or matrilineal line), single nucleotide polymorphisms (SNPs, natural variations within the genome), or heteroplasmy of mitochondrial DNA (i.e., the presence of more than one type of mitochondrial genome).
In total, the team analyzed the mitochondria genome of 193 ME/CFS patients and 196 age- and gender-matched controls (samples collected by the Chronic Fatigue Initiative). After sequencing the mitochondrial DNA, researchers searched for possible correlations of mitochondria genome sequence with health status and symptoms/disease severity as determined by the Short Form-36 and DePaul Symptom questionnaires. Importantly, by sequencing the entire mitochondrial genome of patients, researchers could exclude the presence of other genetic mitochondrial disorders.
Researchers found that the extent of heteroplasmy was low in all study subjects, and that there was no association between mitochondria DNA SNPs and ME/CFS patients versus healthy controls. However, they observed a significant correlation between certain haplogroups (J, U and H) with individual symptoms of joint pain, bloating and dead/heavy feeling after exercise, and symptom severity (the same association was also observed for eight SNPs in ME/CFS patients).
In conclusion, results indicated that ME/CFS individuals of a certain haplogroup or carrying specific SNPs in mitochondrial DNA are more likely to suffer from neurological, inflammatory, and/or gastrointestinal symptoms.