Abstract

Aims/Background—An A to G substitution at base pair 3243 in the mitochondrial tRNA ^Leu(UUR) gene (mt3243) is commonly associated with maternally inherited diabetes and deafness, and other diseases. It is possible that cell free mitochondrial DNA exists in serum and plasma from these patients, and these samples might be a source of material for the detection of such mutations.

Methods—Sixteen patients with type 2 diabetes mellitus and 25 healthy subjects were tested for the 3243 mutation by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) analysis. Plasma and serum from the 41 subjects were tested blind, without knowledge of the final diagnosis.

Results—PCR amplification of the mtRNA ^Leu(UUR) region in mitochondrial DNA (mtDNA) in serum samples revealed the presence of mtDNA in all samples. After ApaI digestion of the amplified DNA fragments, mt3243 was detected in the serum and plasma samples of the seven patients with diabetes who had previously been found to have this mutation in their leucocyte DNA. None of the serum/plasma samples from the healthy subjects or those patients negative for mt3243 in their leucocytes had this mutation (p < 0.001). In addition, the degree of heteroplasmy of mt3243 appeared to be higher in serum and plasma samples than in leucocytes among mt3243 carriers (p < 0.05).

Conclusions—Therefore, mtDNA and associated mutations are present and detectable in serum and plasma. Plasma and serum might be alternative sources for the molecular diagnosis of mt3243 associated diabetes mellitus, as well as other mitochondrial mediated diseases.