Abstract
A series of in vivo experiments is described in which [1-13C]phytanic acid was given as an oral substrate to a healthy subject and two patients showing an impairment in phytanic acid degradation, one with Refsum's disease and one with Chondrodysplasia punctata. After intake of the substrate by the control in a dose of 20 mg/kg body weight, the production of 13CO2 was measured in exhaled breath air and the concomitant formation of labeled 2-hydroxyphytanic acid and of pristanic acid was demonstrated by plasma analysis. After application of a substrate dose of 1 mg/kg body weight to the control, no substantial amounts of 13CO2 were measured, whereas time-dependent analysis of labeled 2-hydroxyphytanic acid in plasma yielded a concentration curve superimposed upon the baseline value (0.2 mol/L) of the unlabeled substance. Phytanic acid accumulated in plasma from the Refsum's disease patient [649 mol/L, controls > 1 y (n = 100): <10 mol/L], whereas the pristanic acid concentration was within the control range [1.4 mol/L, controls > 1 y (n = 100): <3 mol/L]. Low amounts of 2-hydroxyphytanic acid were found normally present [0.04 mol/L, controls > 1 y (n = 11): <0.2 mol/L], and formation of labeled 2− hydroxyphytanic acid could not be demonstrated after ingestion of [1-13C]phytanic acid in a dose of 1 mg/kg body weight. In addition to phytanic acid accumulation (232 mol/L), the Chondrodysplasia punctata patient showed an elevated 2-hydroxyphytanic acid plasma concentration (0.4 mol/L), whereas the plasma pristanic acid level was in the control range (0.7 mol/L). Oral administration of [1-13C]phytanic acid (1 mg/kg body weight) to this patient resulted in a plasma concentration/time profile of labeled 2-hydroxyphytanic acid similar to that of the control. These findings demonstrate that α-hydroxylation of phytanic acid is a physiologic process and indicate that Refsum's disease and Chondrodysplasia punctata patients have a different ability to convert phytanic acid into 2-hydroxyphytanic acid.
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Ten Brink, H., Schor, D., Kok, R. et al. In Vivo Study of Phytanic Acid α-Oxidation in Classic Refsum's Disease and Chondrodysplasia Punctata. Pediatr Res 32, 566–570 (1992). https://doi.org/10.1203/00006450-199211000-00016
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DOI: https://doi.org/10.1203/00006450-199211000-00016