Contribution of odd-numbered fatty acid oxidation to propionate production in neonates with methylmalonic and propionic acidaemias.

Newborns with disturbed propionate metabolism (propionic and methylmalonic acidaemias) accumulate during fetal life large amounts of odd-numbered long-chain fatty acids in adipose tissue (8% to 10% of total fatty acids vs 1% in normal controls) and other body lipids. During periods of acute catabolism, such as in the early days of life, mobilization and oxidation of odd-chain fatty acids from adipose tissue yield extensive amounts of toxic propionyl-CoA in the mitochondria and thus might contribute to the severe illness of the patients. Our data suggest that not only catabolism of protein but also that of adipose tissue has to be avoided in order to alleviate the neonatal illness of patients with propionic and methylmalonic acidaemias. It seems prudent to avoid prolonged fasting during the 1st year of life.