August 12 : A new study has found that genetic variants in mitochondria are directly linked to metabolic markers for type 2 diabetes.

Mitochondria are energy-producing structures harbouring DNA that are inherited only from the mother.

As part of the study Dr. Theodore Kurtz and colleagues compared two different rat strains which possessed virtually identical nuclear genomes but different mitochondrial genomes. This eliminated any complicating effects due to environmental factors or variation in the nuclear genome. Any differences observed between the two rat strains could be attributed to variation in the mitochondria.

The study found that the two strains exhibited significant differences related to energy metabolism and storage.

One rat strain exhibited impaired glucose tolerance, reduced muscle glycogen synthesis, decreased skeletal muscle ATP (energy) levels, and decreased activity of an energy-producing enzyme called cytochrome c oxidase, when compared to the second rat strain. These metabolic characteristics are typical of diabetic individuals.

The researchers then obtained DNA sequences from mitochondria of both rat strains, and found DNA variants in genes that encode for proteins involved in energy production.

Thus, for the first time, they were able to directly link inherited variation in the mitochondrial genome to metabolic markers for type 2 diabetes.

“Our study highlights the role of mitochondrial DNA variation in common genetic diseases,” Dr. Kurtz said.

The findings of the study were published online in Genome Research.