Late to reply
And no, cardiolipin with 4 units of linoleic acid (18:2) is the most common form of cardiolipin in the human body. It is particularly concentrated in the heart.
The proof that 18:2 is absolutely necessary in a healthy human heart is found by examining the case of Barth's Syndrome, which is a genetic disorder that causes Heart Cardiolipin to be altered -- Barth syndrome - Wikipedia
Studies like this show the alteration, in which there is a loss of cardiolipin with 18:2, in favour of cardiolipin with 18:1 -- Bloodspot Assay Using HPLC–Tandem Mass Spectrometry for Detection of Barth Syndrome | Clinical Chemistry
The result are all the diseases of the heart and subsequent functionality in the humans born with this defect, which is very much fatal.
Dave Valentine (author of 'Human Longevity') has this to say:
The major molecular species of CL in cardiac cells is (18:2)4-CL, in which linoleic acid (18:2) occupies all four acyl positions. In Barth’s syndrome the trend is that the 18:2 chains are replaced with more saturated fatty acids, including 18:1.The risks that are mentioned are very clear -- Influence of cardiolipin remodeling on mitochondrial respiratory function in the heart
Studies of Barth’s syndrome establish the essential role of cardiolipin in energy transduction in human mitochondria. CL is primarily located in the inner membrane but is distributed in both leaflets
The universality, localization, amounts, and structure of CL suggest multiple beneficial roles, including formation of supramolecular complexes enhancing energy efficiency as well as appropriate membrane motion and permeability.
These benefits are balanced against risks associated with membrane integrity and oxidative stability.
That last study shows that excess Delta-6 desaturase activity, presumably causing more unsaturated fatty acids in the heart, is directly harmful. That is, once you get cardiolipin that is unsaturated beyond the 2 double bonds in 18:2, peroxidative stress outweighs any benefit of better energetics.
This is very clearly a case of the body having to balance the fast and furious needs of a very active tissue like the Heart, while trying to minimise the downsides. It is clear that without these PUFA on cardiolipin, the heart fails to function, and it is clear that more than the required unsaturation causes damage over time.
Balance is key.
Are you wary of mitolipin for this reason? Or am I making the wrong connection?