Heart muscle from infants who died unexpectedly and who showed fatty changes in the liver at necropsy was analysed for long chain and medium chain acylcoenzyme A dehydrogenase activities by using the natural electron acceptor. In two of the seven cases investigated a deficiency in acylcoenzyme A dehydrogenase activity was found. In one case the deficiency was in medium chain acylcoenzyme A dehydrogenase activity and in the other long chain acylcoenzyme A dehydrogenase activity.
These findings emphasise the importance of investigating fatty acid oxidation in infants who have died unexpectedly.
A fatal case of medium-chain acyl-coenzyme A dehydrogenase deficiency is described in a patient who presented with hypoglycaemia and a gross non-ketotic dicarboxylic aciduria. Cultured skin fibroblasts released 14CO2 from [1-14C] octanoic acid at half the normal rate. Prenatal diagnosis was undertaken in a subsequent pregnancy in which cultured amniotic fluid cells revealed a marked reduction in octanoate oxidation indicative of an affected fetus. The pregnancy was terminated and the diagnosis was confirmed by enzyme analysis of skin fibroblasts taken from the fetus. The high residual octanoate oxidation by affected fibroblasts together with the absence of any characteristic abnormality of amniotic fluid organic acids are a potential limitation to the reliability of this type of prenatal diagnosis.
We have measured the rate of oxidation of [1(-14)C]octanoate in cultured amniotic fluid (AF) cells at various passages and in AF cell lines with different clonal morphology. It is possible that both the passage number and the cell type may influence the outcome of prenatal diagnosis of fatty acid oxidation defects using this technique. We found that there was no significant difference between the three major AF cell types (epithelial, large epithelial, and fibroblast) when analysed at identical passage number but there was a significant reduction in octanoate oxidation in all cell types with increasing passage. For reliable prenatal diagnosis, cell lines of similar low passage number should be used.
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