Cardiolipin

Overview
Cardiolipin (bisphosphatidyl glycerol) is an important component of the inner mitochondrial membrane, where it constitutes about 20% of the total lipid.

Function and structure
It is typically present in metabolically active cells of the heart and skeletal muscle, in the membranes of their mitochondria, mostly in the inner membrane, and consists roughly 20% of its lipids. It has also been observed in certain bacterial membranes.

It serves as an insulator and stabilizes the activity of protein complexes important to the electron transport chain. It also "glues" them together.

Cardiolipin is a "double" phospholipid because it has four fatty acid tails, instead of the usual two.

Barth syndrome
Barth syndrome is a rare genetic disorder that was recognised in the 1970's to cause infantile death. It has a mutation in the gene coding for tafazzin, an enzyme involved in the biosynthesis of cardiolipin. Girls heterozygous for the trait are unaffected. Sufferers of this condition have mitochondria that are abnormal, and they cannot sustain adequate production of ATP. Cardiomyopathy and general weakness is common to these patients. Cardiolipin treats the symptoms of BTHS and prevents infections.

Diabetes
Heart disease hits people with diabetes twice as often as people without diabetes. In those with diabetes, cardiovascular complications occur at an earlier age and often result in premature death, making heart disease the major killer of diabetic people. Cardiolipin has recently been found to be deficient in the heart at the earliest stages of diabetes, possibly due to a lipid-digesting enzyme that becomes more active in diabetic heart muscle.

Antiphospholipid syndrome
Patients with anti-cardiolipin antibodies (Antiphospholipid syndrome) can have recurrent thrombotic events even early in their mid-late teen years. These events can occur in vessels where thrombosis may be relatively uncommon, such as the hepatic or renal veins. These antibodies are usually picked up in young women with recurrent spontaneous abortions. In anti-cardiolipin mediated autoimmune disease there is a dependency on the apolipoprotein H for recognition.

Syphilis
Cardiolipin from a cow heart is used as an antigen in the Wassermann test for syphilis. Anti-cardiolipin antibodies can also be increased in numerous other conditions, including malaria and tuberculosis, so this test is not specific.