Fatty Acid Composition of Human Serum Lipids at Birth

Abstract

Umbilical cord blood was collected immediately after birth from 55 unselected newborn infants. Fatty acid spectra of serum cholesterol esters, triglycerides, phospholipids and free fatty acids were determined by a combination of thin layer and gas liquid chromatography. Triglyceride and cholesterol concentrations were determined in total serum and in the three major lipoprotein classes. The three major fatty acids in cholesterol esters, triglycerides and free fatty acids were palmitic, oleic and linoleic acid, comprising 75 per cent of all acids. In phospholipids palmitic, stearic and arachidonic acid comprised about 75 per cent of all acids. The greatest amounts of linoleic acid were obtained in cholesterol esters (about 20 per cent) and free fatty acids (about 15 per cent), whereas arachidonic acid was most common in cholesterol esters (about 12 per cent) and phospholipids (about 18 per cent). In addition phospholipids contained 16 per cent highly unsaturated fatty acids besides linoleic and arachidonic acid. There were no sex differences within any lipid fraction. There was a striking difference in the fatty acid pattern between cord blood and adult blood. The relative content of linoleic acid was 60–70 per cent lower in cholesterol esters and phospholipids. Further, much higher relative contents of arachidonic acid were found in all serum lipids at birth. The ratio between polyunsaturated and saturated fatty acids in triglycerides and free fatty acids was the same in newborns and adults, but the ratio was lower in cholesterol esters and phospholipids at birth. There was also a positive correlation between linoleic and arachidonic acids in cholesterol esters and in triglycerides. For most of the fatty acids there were positive correlations between cholesterol esters and triglycerides. The various correlations suggest similar steps in the foetal liver metabolism and/or in the placental transfer and metabolism of different acids. There were weak positive correlations between the serum triglyceride concentration and the relative content of linoleic acid in triglycerides and of linoleic and arachidonic acid in cholesterol esters. Only very weak or no correlations were present between total serum cholesterol and the different fatty acids. The correlations between fatty acids and the very low, the low and the high density lipoproteins were similar or weaker than those between fatty acids and total serum lipids.