Since 1992 it is known, that mutations in the mitochondrial (mt) genome can be the cause of diabetes. Mitochondries contain an own ring shaped genome, which stears the synthesis of 13 proteins and the necessary tRNA’sa. By now, we know already around 40 different, diabetogenic mutations of the mt-genome. Most frequently the punctual mutation (hotspot) A3243G in the tRNA Leu(UUR) is reported. This mutation alone represents a part of 1-1,5% in most studies diabetes populations. New studies (France, Japan) even reach almost 3%. The overall part of all mitochondrial forms in such an average diabetes population is not yet clear. Such data are mostly not available because the proof of an unknown damage of the mitochondrial genome often poses a difficult analytical problem. Almost always only a fraction of the mitochondries in a cell are touched. This phenomenon is called heteroplasmia. The part of concerned mitochondrial genomes varies from one tissue to another. Specifically the tissues concerned show a high percentage of mutated mt DNA, generally the post mitotic tissues have the biggest parts.
For the analyst this implies that blood is not the best sample material, better are saliva or urine sediment, but the most secure way to find as previously not known mitochondrial defect is with the use of muscle tissue.
The inherited way is maternal i.e. only concerned mothers transmit the defect to the children. All siblings of a patient with mt diabetes also have the defect.
Next to the diabetes, mitochondrial mutations trigger a range of symptoms that are not the consequence of hyperglycemia as it is the case for the classic diabetes forms. These symptoms are caused by the mitochondrial defect.
Very painful muscle weaknesses are often described after long walks as well as macula-atrophy and deafness. These symptoms appear in various combinations and different degrees of intensity.
