Acylcarnitine metabolism during fasting and after refeeding.

Carnitine metabolism during starvation and just after refeeding was studied by the measurement of acylcarnitine (ACR) and total carnitine (TCR) concentration in the serum and liver of mice. Starvation caused marked increases in the concentration of serum ACR, and of acid-soluble ACR in the liver. The refeeding caused the quick decrement of serum ACR with a concomitant marked increase in the level of acid-soluble TCR in the liver. Through the use of positron emission tomography in a rhesus monkey, a marked increase in [2-11C]acetyl-L-carnitine uptake in the liver was observed after the administration of glucose accompanying the decrease of serum ACR. From this study, it is clear that the mammalian liver can salvage and conserve the unused ACR when the state of energy metabolism is improved.