The role of carnitine in fatty acid oxidation

Carnitine is a substance that plays an important role in the fat metabolism.
As explained in the page about fat metabolism, carnitine is needed to transport the longer fatty acids (C10 and more) into the mitochondrion where they can be oxidized for energy.
Besides that carnitine also plays an important role in the evacuation of fatty acids from the mitochondria that cannot be metabolised due to MCAD deficiency.

An activated fatty acid (acyl-CoA) is bound to carnitine to form acylcarnitine (the CoA is removed). This acylcarnitine can then be transported into the inside of the mitochondrion using 3 other biochemical processes that are not further discussed here.
The inside of the mitochondrion is called the matrix.
Once the acylcarnitine is inside the matrix, the carnitine is released and the fatty acid is again bound to a CoA. The resulting acyl-CoA can then be oxidized using beta-oxidation.
The carnitine can leave the matrix and can be bound to the next acyl-CoA to transport it inside the mitochondrion.

In patients with MCAD deficiency the beta-oxidation is not (properly) functioning. The medium chain acyl-CoA's can not be further processed and start to accumulate in the matrix. This substance is toxic if it remains there in large quantities.

Carnitine plays also an important role in removing these toxic substances. Carnitine can bind again with them and the resulting acylcarnitine can be excreted via the kidneys with the urine.

Patients with MCAD deficiency have in their urine (but also in their blood) a lot of so called octanoylcarnitine. These are acylcarnitines of length C8 (medium-chains). Also the level of acylcarnitines with lengths C6 and C10 can be elevated.
Normally carnitine is reused for the transport of other longer fatty acids into the mitochondria. But in patients with MCAD deficiency a lot of the carnitine is lost via urinary excretion. So these patients will often have a shortage of carnitine in their blood.
The carnitine levels in the blood can be restored by taking oral supplements (see the section about treatment for more information).

Read more about what happens when fasting >

References
The information on this website is a summary of information that is publicly available on other websites as well as information from books for sale on the internet and in public book stores.
The content of this website is not validated by doctors, scientists or geneticists.

This page was last modified on 6 March 2011