In vitro metabolism of palmitic acid and glucose in the developing tissue of the rhesus monkey

Fetal, newborn, and adult tissues of rhesus monkeys metabolize glucose-U-14C and palmitate-1-14C to lipids and 14CO2 in vitro. During growth and development, differences in substrate utilization are detected. In the lung, phospholipid synthesis with the use of either substrate increases as development proceeds. In the brain, lipid synthesis diminishes after birth, though glucose utilization and 14CO2 production from glucose-U-14C increase. The metabolism of liver lipids varies with age, the term fetus and newborn infant converting less palmitate to lipids than the young fetus or the adult animal. Most of the radioactivity of palmitate is found in the 16C fatty acid fraction of the various lipids. In the newborn infant, the catabolism of glucose-U-14C or palmitate-1-14C increases in the brain and lung while palmitate curtails glucose utilization in these tissues. Since palmitate has been shown to cross the rhesus monkey placenta in vitro and in vivo, to curtail glucose utilization, and to be incorporated into fetal lipids, the present data indicate that fatty acids of either maternal or fetal origin can, along with glucose, be utilized for the formation of fetal lipids. In fetal tissues, the conversion of palmitate to carbon dioxide is small. Therefore, a limited but steady flow of fatty acids of maternal origin may account for a large proportion of total fetal tissue lipid deposition. The data indicate that, while glucose metabolism is essential to the primate fetus, lipid synthesis from fatty acids may be more important than it is presently considered.