PRODUCTION AND DISPOSAL OF MEDIUM-CHAIN FATTY-ACIDS IN CHILDREN WITH MEDIUM-CHAIN ACYL-COA DEHYDROGENASE-DEFICIENCY

The effect of fasting on plasma concentrations of fatty acids has been determined in four children with medium-chain acyl-CoA dehydrogenase (MCAD) deficiency. In addition, the in vivo rate of octanoate oxidatio n was measured, using 1-C-13octanoate. In the three older children ( 1.5-11.2 years), fasting for up to 18h stimulated lipolysis, as reflec ted by the increasing concentration of free fatty acids, but with litt le rise in concentrations of medium-chain fatty acids, octanoate, deca noate and cis-4-decenoate. In an infant (0.5 year), lipolysis was grea ter and was accompanied by rising concentrations of medium-chain fatty acids. After 13.5h there was a rapid increase in the concentration of decanoate and cis-4-decenoate. The calculated in vivo rate of octanoa te oxidation was substantial in all patients studied (6.4-13.1 mu mol/ kg per h) despite very low MCAD activity in vitro. It is concluded tha t under basal conditions the in vivo oxidation rate of medium-chain fa tty acids is near normal in the four children studied with MCAD defici ency.