Tocopherol in inborn errors of intermediary metabolism.

Red blood cell tocopherol was measured in a group of 92 children with inborn errors of intermediary metabolism to evaluate the peroxidative damage in different mitochondrial and cytosolic defects, and to consider the need for treatment or vitamin supplementation. Tocopherol was determined by HPLC with UV detection. Results were expressed in nanomoles red blood cell tocopherol per gram protein. Significant differences (Mann-Whitney; P < 0.001) were found between tocopherol levels in untreated patients: 19 with mitochondrial defects versus 23 with cytosolic enzyme or transport defects, and versus 58 age-matched reference values. In conclusion, mitochondrial enzyme deficiencies, either amino and organic acidurias or defects of energy metabolism, seem to produce an excess of free radicals with the consequent utilization of tocopherol as antioxidant. This is not apparent in the cytosolic enzyme defects studied, whose tocopherol levels are in the normal range. Treatment with tocopherol completely corrects the deficient antioxidant status.