Accumulation of Free 3-Hydroxy Fatty Acids in the Culture Media of Fibroblasts from Patients Deficient in Long-Chain l-3-Hydroxyacyl-CoA Dehydrogenase: A Useful Diagnostic Aid

BACKGROUNDThe diagnosis of long-chain L-3-hydroxy-acyl-coenzyme A dehydrogenase (LCHAD) deficiency frequently requires the study of cultured fibroblasts. We developed such a test that does not require disruption and loss of the cells.METHODSWe measured free 3-hydroxy fatty acids (3-OHFAs) in media of skin fibroblasts cultures from 11 patients with a genetic deficiency of LCHAD and the associated disorder of mitochondrial trifunctional protein (MTFP). Fibroblasts were cultured for 24 h with 100 micromol/L nonisotopic palmitate added. 3-OHFAs were measured by selected-ion monitoring, stable-isotope dilution gas chromatography-mass spectrometry with [(13)C]-labeled internal standards.RESULTS3-OH-hexadecanoic and 3-OH-tetradecanoic FAs were increased 14- and 11-fold, respectively, in all patients with LCHAD or MTFP deficiency when compared with control fibroblast cell lines after overnight incubation with palmitate. 3-OH-dodecanoic FA demonstrated a modest, fivefold increase in LCHAD-deficient cells. The concentrations of all 3-OHFAs were similar whether or not the medium samples were hydrolyzed to release conjugated species such as acylcarnitines, suggesting that 3-OHFAs accumulate in the media as free FAs.CONCLUSIONSMeasurement of 3-OHFA excretion from LCHAD- or MTFP-deficient cell lines can be used as a diagnostic tool. Free FAs are the predominant form of these abnormal metabolic intermediates in culture media.