Background It was reported previously that at an early stage of the Huntington’s disease (HD), patients had lower body mass index, without change in intake of calories, than matched controls. This suggested that HD is associated with a metabolic problem, and shed new light on the role of mitochondrial DNA (mtDNA) in HD. However, despite many years of intensive research, the role of mtDNA in HD remains unknown.

Aims The aim of this study is to compare the ratio of the number of copies of mtDNA to nuclear DNA (nDNA) in leukocytes of patients with HD and normal subjects. Furthermore we aimed to evaluate the relationship between the change in the level of mtDNA and various factors which were proposed as indicators of the progress and severity of the disease (e.g. characteristics of disease disturbances, CAG repeat number, age of onset). We assumed that understanding of the role of mtDNA copy number in the pathogenesis of HD could be important for development of new biological maker(s).

Methods DNA was isolated from leucocytes of blood collected from a group of patients and a control group in different ages, sexes, and at different levels of severity of the disease. The quantitative PCR with SYBR Green was used to determine the mtDNA copy number per cell by using the estimation of the threshold cycle number of 16S rDNA, a chosen mitochondrial gene, and a gene coding for β-globin (a nuclear gene). The data were analysed statistically with regard to factors predicting progress and severity of the disease.

Results Our results show that the average number of copies of mtDNA in healthy subjects has a high volatility. The average level of mtDNA was lower in patients relative to controls. Correlations with different factors predicting progress and severity of the disease were assessed.

Conclusions We suggest that the level of mtDNA could be useful in predicting the course of the disease, along with other factors.

This project is funded by National Research Centre, Poland, No UMO-2011/03/B/NZ2/01422.