About Mitochondrial Disease

A mitochondrial disease is caused by a fault or faults in mitochondria.OK. So what are mitochondria?

Firstly it is pronounced 'my-toe-con-dree-a'
Secondly 'mitochondria' is the plural of 'mitochondrion'

WHAT DO MITOCHONDRIA DO?
As you know, the cells, which make up our body, need energy to work and that energy comes from the food we eat. Mitochondria are minute bodies inside the cell which play a crucial part in converting food into energy. Converting food into energy is known as metabolism. A long, complicated chain of chemical reactions converts the nutrients into a substance called ATP . The cell then uses ATP as the 'fuel' to power the work it has to do. Cells which need a lot of energy, like muscle cells, need a lot of ATP and, therefore, a lot of mitochondria.

WHAT CAN GO WRONG?
You've heard of DNA , the long strings of chemicals, carried in the nucleus of the cell. DNA has been likened to a 'blueprint'.It is a set of instructions which orders everything the cell does. Mitochondria have their own DNA . They are almost cells within a cell. Mitochondrial DNA is known as mtDNA .

There is considerably less DNA in a mitochondrion than there is in the nucleus of its 'host' cell but, nonetheless it is an important set of instructions to the mitochondrion. If there is an error in it, the mitochondrion may not work the way it should and this can affect the health of the whole cell if it does not get enough energy.
In addition to being deprived of sufficient energy there is also the problem of foods not being completely metabolised . The by-products of incompletely metabolised foods can build up and act like poisons interfering with other chemical reactions in the cell making the energy shortage even worse. Some act as 'free radicals' and can cause additional damage to the mitochondria exacerbating the problem. There may also be the problem of lactic acidosis . In normal cell function a small amount of energy is released by the conversion of glucose to pyruvate. More energy is then released when this pyruvate is converted by the mitochondria to water and carbon dioxide. However, if the mitochondria are not working properly, this pyruvate is ,instead, converted to lactic acid. Excessive lactic acid creates the condition known as 'lactic acidosis'. (However, it should be noted that there are several other causes of high lactic acid so the presence of high lactic acid is not, by itself, necessarily indicative of mitochondrial disease.)

ERRORS IN mtDNA
In some cases a vital part of mtDNA is missing. This is known as a deletion. In other cases it may be that the wrong chemical is at a particular point in the mtDNA . This is known as a point mutation . Imagine working to a set of instructions when one or more lines are missing(deletions) or totally misprinted (point mutations).

The mitochondria live in a complex inter-relationship with their 'host' cell. Sometimes a fault in the DNA in the cell nucleus may be responsible for the mitochondria not working properly. The specialist will be concerned to find out whether the fault lies in mtDNA or in the main cell DNA .

Either way, if not enough mitochondria are doing their job, the cell will be short of energy and disability will be the result.