Acylcarnitines in fibroblasts of patients with long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency and other fatty acid oxidation disorders

Mitochondrial fatty acid oxidation disorders cause hypoglycaemia, hepatic d ysfunction, myopathy, cardiomyopathy and encephalopathy. Despite their reco gnition for more than 15 years, diagnosis and treatment remain difficult. T o help design rational diagnostic and therapeutic strategies, we studied th e pathophysiology of accumulating metabolites in a whole-cell system. Acylc arnitines were quantified in cells and media of cultured fibroblasts after incubation with L-carnitine and fatty acids. Following incubation with palm itate, long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD)-deficient fibrobl asts compared with controls showed elevation of hydroxypalmitoyl- and palmi toylcarnitine and reduction of C-10- and shorter acylcarnitines, and follow ing incubation with linoleate an increase in C-14:2-, C-18:2- and hydroxy-C -18:2-acylcarnitines and reduction in C-10:1-acylcarnitines. Hydroxyacylcar nitines remained more intracellular compared to corresponding saturated acy lcarnitines. Incubation with decanoate and octanoate showed absence of hydr oxylated acylcarnitines and correction of secondary metabolic disturbances, suggesting that optimal treatment should include medium-chain triglyceride s of these chain lengths. Fibroblasts of patients with other fatty acid oxi dation disorders showed distinct elevations of disease-specific acylcarniti nes. This acylcarnitine analysis allows the diagnosis of LCHAD deficiency a nd its differentiation from other fatty acid oxidation disorders, which can pose difficulties in vivo. The strategy has allowed in-depth analysis with different substrates, providing suggestions for the rational design of tre atment trials.