The deficient degradation of synthetic 2- and 3-methyl-branched fatty acids in fibroblasts from patients with peroxisomal disorders.

The oxidation of pristanic and phytanic acids by human skin fibroblasts was compared to that of their synthetic analogues, 2-methylpalmitic and 3-methylmargaric acids. The synthetic compounds and natural substrates were degraded at comparable rates in control and X-linked adrenoleukodystrophy fibroblasts. The alpha-decarboxylation of 3-methylmargaric acid, similarly to that of phytanic acid, was affected in Refsum disease and Zellweger syndrome, but not in X-linked adrenoleukodystrophy. The beta-oxidation of 2-methylpalmitic acid, similarly to that of pristanic acid, was deficient in fibroblasts derived from patients suffering from Zellweger syndrome, confirming the importance of peroxisomes in the breakdown of 2-methyl-branched fatty acids. No deficiency was observed in fibroblasts from X-linked adrenoleukodystrophy patients. The 1-14C-labelled 2- and 3-methyl-branched fatty acids, which are easier to synthesize that the natural analogues, are therefore valuable tools for the diagnosis of human peroxisomal disorders.