Posted by jayaram in A number of diseases result from abnormalities in lipid metabolism. They are due to genetic defects affecting one of the enzymes necessary for their catabolism.
Acyl CoA dehydrogenase deficiency:
The most common genetic defect in lipid metabolism is an acyl CoA dehydrogenase deficiency. There are four different isoenzymes of acyl CoA dehydrogenase and each acts on fatty acids of different chain lengths. The most common deficiencies are the long and medium –chain specific enzymes. Mitochondrial beta-oxidation of fatty acids proceeds in these patients until encountering the step that is catalyzed by the defective acyl CoA dehydrogenase isoenzymes. The catabolic process stops at this point. The accumulated fatty acids are converted to dicarboxylic acid due to omega oxidation. The chain length of the dicarboxylic acid formed depends on the acyl CoA dehydrogenase that is deficient. Accumulation of dicarboxylic acid in the plasma produces dicarboxylic academia and metabolic acidosis. It often leads to death in childhood.
SIDS:
SIDS refers to sudden infant death syndrome, which causes unexpected death in healthy infants. It is due to a deficiency of medium chain acyl CoA dehydrogenase. Glucose is the principal source of energy, soon after feeding babies. After a few hours, glucose level goes down and utilization of fatty acids occurs simultaneously to meet the energy needs. A blockade in beta-oxidation caused by a deficiency of medium chain acyl CoA dehydrogenase causes the sudden death in infants.
Methylmalonic academia:
Two types of Methylmalonic academia are produced due to deficiency of vitamin B12 and due to defect in the enzyme methylmalonyl CoA mutase. In either case, there is an accumulation of methymalonic acid in the body, followed by its excretion in urine. It causes severe metabolic acidosis, damage to the central nervous system and retards the normal growth. It is often in the early years of life.