Changes of serum apo A-IV levels in a newborn with chylothorax treated with medium-chain triglyceride milk

Abstract

Chylothorax in the neonatal period is a very rare condition and its etiology remains uncertain. The pleural effusion in a patient with chylothorax contains fat absorbed from the intestine. Thus it is worthwhile analyzing the effusion to determine the content of chylomicrons formed in intestinal cells during fat absorption, though it is contaminated with plasma components to some degree. It is known that human apo A-IV [l] and B-48 [2] are specifically synthesized in the intestine. Both are major apolipoproteins of chylomicrons. Chylomicrons are formed in intestinal cells after fat absorption and then enter into blood circulation via intestinal lymphatics and the thoracic duct. However, it is not well known how these apolipoproteins participate in the formation of chylo~crons. On the other hand, MCT (medium-Ghan triglyceride) contains fatty acid molecules with a chain length varying from 6 to 12 carbon atoms. Because fatty acids with a carbon length of below 12 are absorbed almost wholly into the portal venous system [3], MCT has been used in the treatment of chylothorax [4]. In this study, we examined the changes of apo A-IV levels in serum and pleural effusion and the apo B-48/total apo B ratio in the TRL (triglyceride-rich lipoprotein) fraction of the effusion during treatment with MCT milk. In addition, we tried to elucidate the influence of the MCT absorption on the levels of apo A-IV in serum and B-48 in the pleural effusion.