Multiple acyl-coenzyme A dehydrogenation disorder responsive to riboflavin: substrate oxidation, flavin metabolism, and flavoenzyme activities in fibroblasts.

Multiple acyl-CoA dehydrogenation disorders result from generalized defects in intramitochondrial acyl-CoA dehydrogenation. Fibroblasts from a riboflavin-responsive multiple acyl-CoA dehydrogenation disorder patient catabolized 14C-butyrate, -octanoate, and -leucine normally after culture in riboflavin-supplemented medium (2 mg/L). After culture in riboflavin-depleted medium (< or = 1.4 micrograms/L), his cells oxidized the same substrates poorly at 20 to 33% of control (p < 0.05). Patient cells incubated in a wide range of D-[2-14C]riboflavin concentrations (3, 31.4, and 100 micrograms/L) synthesized 14C-flavin mononucleotide and 14C-flavin adenine dinucleotide (FAD) normally and had normal cytosolic 14C-flavin mononucleotide and 14C-FAD contents, which argues against defects in cellular riboflavin uptake and conversion to flavin mononucleotide and FAD. After culture in 31.4 micrograms 14C-riboflavin/L for 2 wk, 14C-FAD specific radioactivities plateaued and were similar in patient and control cells. However, culturing these uniformly labeled cells in riboflavin-depleted medium for 2 wk lowered the patient's cellular 14C-FAD content to only 23% of control levels. Similarly, after incubation in low 14C-riboflavin concentrations (4.4 micrograms/L), the patient's mitochondrial 14C-FAD content was only 51% of control after 1 h and 29% of control at 4 h. After a 4-h incubation in a high physiologic concentration of 14C-riboflavin (31.4 micrograms/L), which raised the patient's cellular 14C-FAD levels 3- to 4-fold, his mitochondrial 14C-FAD content rose to normal; control values did not change. We also investigated possible defective FAD binding to flavoenzymes essential for acyl-CoA dehydrogenation.(ABSTRACT TRUNCATED AT 250 WORDS)