Intramitochondrial fatty acid metabolism: riboflavin deficiency and energy production.

Inborn errors of fatty acid beta-oxidation have contributed significantly to our understanding of intracellular fatty acid metabolism. The first intramitochondrial step in beta-oxidation of fatty acyl-CoA of different chain lengths is catalyzed by the three chain length specific acyl-CoA dehydrogenases. Inherited deficiency of these enzymes has been reported. Some are riboflavin responsive. The first step of fatty acid oxidation is reviewed with specific emphasis on beta-oxidation in newborn infants, rendered riboflavin deficient by phototherapy. Given that medium chain fatty acids are not stored as triacylglycerols and undergo rapid beta-oxidation, they have been proposed as superior substrates compared with long chain triglycerides in times of metabolic stress. This review also examines medium chain triglycerides as an alternate energy source. When medium chain triglycerides were fed as 50% of total energy, glucose sparing was present with little loss of energy as dicarboxylic acids.