But the mitochondria within each cell have their own set of DNA. This set comes from our mothers, with no contribution at all from our fathers. But like our other DNA, this DNA sometimes has mutations, and mutations may be passed down maternally.
Some of the mutations in mitochondrial DNA cause diabetes. Diabetes caused by the most common mitochondrial mutation tends to be caused by gradual deterioration of beta cells and therefore a gradual inability to make insulin. It is not autoimmune, and it is not usually accompanied by insulin resistance. The diabetes is most often diagnosed in teens, young adults, or middle aged adults; less often in the elderly and rarely in young children. Of people with the mutation, half are diagnosed with diabetes by the age of 38, and 80% are diagnosed by the age of 60.
Roughly 1% of all cases of diabetes are believed to be caused by mitochondrial mutations. Because hearing loss is often caused by the same mitochondrial mutations that cause diabetes, hearing loss that comes before a diabetes diagnosis, hearing loss and diabetes in a young adult is a good reason to suspect mitochondrial diabetes. Another good reason to suspect mitochondrial diabetes is a family in which there is a mitochondrial pattern of inheritance- all or most of the siblings born to the same mother developing diabetes and/or hearing loss, the mother and her siblings, the maternal grandmother and her siblings. Macular disease in the eye is usually mild enough that it doesn't cause problems, but if it is there at all, it should also raise a red flag.
Mitochondrial mutation related diabetes is associated with a lot of health issues that a person might want to know he was at risk for; it's also NOT associated with some of the health issues associated with type 2 diabetes (ie hypertension) or type 1 diabetes (autoimmune thyroid disease).