Placental Fatty Acid Transfer Research Articles

Placental transfer of fatty acids

Placental transfer of fatty acids

In vitro palmitate and glucose metabolism in the postmature fetus

Fetuses from term and postmature rabbits were obtained and their livers incubated with palmitate-1-14C in room air. The net incorporation of the fatty acids into ketone bodies, lipids, and CO2 was measured at fixed and variable concentrations of cold glucose. Data from postmature liver show that lipid synthesis is decreased, 14CO2 production is increased, and ketone body formation is unchanged when compared with data from the term liver. The addition of cold glucose to a constant concentration of palmitate-1-14C causes a slight increase in lipid synthesis in the postmature liver, in contrast to a decrease in the term liver. The experimental results indicate that liver lipid synthesis and glucose utilization are diminished in the postmature preparation. This suggests that the postmature fetal liver responds to the decreased availability of free fatty acid from the placenta and to the increasing hypoxia by metabolic adaptations resembling those observed during fasting and tissue hypoxia. These changes are somewhat similar to those observed in the neonate before the onset of breast-feeding. Fetal metabolism is, therefore, responsive to changes in placental transfer of fatty acids and to postmaturity.

Lipid metabolism and mobilization in the guinea pig during pregnancy.

The liver of the foetal guinea pig accumulates a large quantity of triacyglycerol late in gestation at the same time that adipose-tissue mass grows at its maximum rate and foetal adipose-tissue lipoprotein lipase activity and sensitivity to lipolytic hormones has substantially declined. The fatty acid for triacyglycerol synthesis is not synthesized in the foetal liver and it is unlikely that it originates from any of the foetal tissues. Before the accumulation of hepatic triacyglycerol the concentration of free fatty acids increases in both the umbilical vein and the maternal inferior vena cava. This occurs at a time when the triacyglycerol lipase activity in maternal adipose tissue is elevated and the rate of lipolysis, but not of fatty acid esterification, is higher than earlier in gestation or than in the non-pregnant state. It is proposed that the increase in lipolysis in maternal adipose tissue, brought about by an increase in circulating lipolytic hormones, mobilizes fatty acid, which passes to the foetus and is partly stored as hepatic triacylglycerol. The foetal liver effectively removes both long-and short-chain fatty acids from umbilical-vein blood. The rate of placental fatty acid transfer is more than adequate to account for the triacylglycerol accumulation.