12- and 15-hydroxyeicosatetraenoic acid are excreted in the urine of peroxisome-deficient patients: evidence for peroxisomal metabolism in vivo

To determine the importance of peroxisomes and mitochondria in hydroxyeicosatetraenoic acid (HETE) oxidation in vivo, urinary excretion of 12- and 15-HETE was measured in eight patients with a peroxisome deficiency disorder (Zellweger syndrome) showing normal mitochondrial beta-oxidation capacity, in three patients with a defect of mitochondrial long-chain fatty acid oxidation (long-chain acyl-CoA dehydrogenase deficiency), and in eight healthy subjects. 12- and 15-HETE were identified and quantified by gas chromatography/negative ion chemical ionization-mass spectrometry and specific RIA. The free compounds were found exclusively in the urine of peroxisome-deficient subjects (12-HETE: median 26 pg/mL, range 17-36 pg/mL; 15-HETE: median 40 pg/mL, range 29-61 pg/mL), whereas both compounds were below the detection limit (< 0.5 pg/mL) in the urine of patients with defective mitochondrial long-chain fatty acid oxidation and normal subjects (p < 0.002). These results implicate that peroxisomes are the main cellular organelle responsible for HETE oxidation in vivo. Analysis of HETE excretion in urine represents an additional new specific diagnostic tool in patients with Zellweger syndrome.