Intermediates of unsaturated fatty acid oxidation are incorporated in triglycerides but not in phospholipids in tissues from patients with mitochondrial beta-oxidation defects

The fatty acid composition was determined of liver, skeletal muscle and hea rt obtained post mortem from patients with medium-chain acyl-CoA dehydrogen ase deficiency (MCADD), multiple acyl-CoA dehydrogenase deficiency (MADD) a nd very long-chain acyl-CoA dehydrogenase deficiency (VLCADD). Increased am ounts of 4-decenoic acid 10:1(n-6), 5-dodecenoic acid 12:1(n-7), 5-tetradec enoic acid 14:1(n-9), 5,8-tetradecadienoic acid 14:2(n-6) and 7,10-hexadeca dienoic acid 16:2(n-6)-intermediates of unsaturated fatty acid oxidation-we re found. Fractionation into different lipid classes showed that these fatt y acids were exclusively present in the triglyceride fraction. They could n ot be detected in the free fatty acid fraction or in the phospholipid fract ion. Our results suggest that intermediates of unsaturated fatty acid oxida tion that accumulate as a consequence of MCADD, MADD and VLCADD are transpo rted to the endoplasmic reticulum for esterification into neutral glyceroli pids. The pattern of accumulation is characteristic for each disease, which makes fatty acid analysis of total lipid of post-mortem tissues a useful t ool in the detection of mitochondrial fatty acid oxidation defects in patie nts who died unexpected, for example with sudden infant death syndrome.