Content of phospholipids in human diets studied by the duplicate-portion technique

1. The phospholipid intake by eight healthy women was studied by the duplicate-portiontechnique, i.e. chemical analyses of duplicates of the food consumed. Their intake of phospholipids was 1·5–2·5 mmol lipid-phosphorus/d, which correspondsto 0·023–0·059 mmol lipid-P/g dietary fat and 0·24–0·45 mmol lipid-P/MJ respectively.2. Choline phosphoglyceride constituted 480–700 mmol/mol and ethanolamine phosphoglyceride 170–240 mmol/mol total lipid-P. Most of the choline in nature occurs as choline phospholipids, the intake of which ranged between 0·91–1·85 mmol/d or 0·15–0·33 mmol/MJ.3. Palmitate, stearate, oleate, and linoleate were the four major fatty acids both in choline phosphoglyceride and ethanolamine phosphoglyceride. Significant amounts of highly unsaturated, C20 and C22 fatty acids were also observed. It was calculated that 13–33 mg/g total dietary fatty acids was consumed as phospholipids. Together with bile phospholipids, dietary phospholipids and their degradation products may be important in the digestion and absorption processes.

Lipid composition and metabolism in liver and brain of vitamin B12-deficient rat sucklings

1. Rat sucklings (18-d-old) bred from vitamin B12-deprived dams were compared with vitamin B12-suplemented dams’offspring, which were considered normal rat sucklings.2. The vitamin B12-deficient rat sucklings had lower body-weight, liver weight and brain weight.3. Vitamin B12 deficiency was also evident from the tenfold lower concentrations of vitamin B12 in liver and cerebellum.4. The concentration of liver lipid was markedly increased in vitamin B12-deficient rats; triacylglycerol accounted for most of the increase. In brain the lipid concentration was slightly decreased (P < 0.05).5. The methylation of ethanolamine phosphoglyceride to choline phosphoglyceride was reduced in both liver and brain in vitamin B12-deficient rats, as measured after the administration of [14C]ethanolamine. A slight decrease in choline phosphoglyceride concentration could be a consequence of this finding. The composition of phospholipids was otherwise normal.6. Odd-chain fatty acids (pentadecanoate and heptadecanoate) accumulated in both liver and brain of the vitamin B12-deficient rat sucklings and constituted approximately 1% of total fatty acid.7. The biosynthesis of fatty acid and cholesterol from intraperitoneally-injected 3H2O and [14C]propionate was unchanged in vitamin B12 deficiency.

Stimulation of renal phospholipid formation during potassium depletion.

Potassium depletion induces increased membrane phospholipid formation and renal growth in rats. To determine the mechanism by which potassium depletion augments phospholipid formation, the metabolism of radioactive choline, a precursor of choline-containing phospholipids, was studied in renal slices. Cortical and medullary tissue from potassium-depleted and control animals accumulated extracellular choline and sequentially converted it to phosphorylcholine, cytidine diphosphocholine (CDP-choline), and choline phosphoglyceride, thereby demonstrating that renal cells can utilize the Kennedy pathway for phospholipid synthesis. [14C]Choline uptake into intracellular fluid was increased in cortical slices from potassium-depleted animals. The apparent Km and Vmax of the kinase reaction which converts entering [14C]choline to [14C]phosphorylcholine were unchanged during potassium depletion. The rate of [14C]phosphorylcholine conversion to [14C]CDP-choline was also unchanged. In contrast, the Vmax of [14C]choline phosphoglyceride formation from [14C]CDP-choline was increased, whereas the apparent Km for this reaction was unchanged. These results indicate that increased renal choline phosphoglyceride formation during potassium depletion can occur via the Kennedy pathway and appears to be mediated by increases in choline uptake and the rate of CDP-choline incorporation into phospholipid, the first and last steps of the pathway.

AN ANALYSIS OF THE LIPIDS OF GRYLLUS BIMACULATUS (DEGEER) (INSEGTA, ORTHOPTERA)

The lipids of the cricket Gryllus bimaculatus (DeGeer) have been analyzed by thin-layer and gas–liquid chromatography. Choline phosphoglyceride (54.2%) and ethanolamine phosphoglyceride (35.4%) comprised most of the phospholipids. Smaller amounts of sphingomyelin and an unidentified acidic phospholipid were found. Linoieic acid made up roughly 50% of the fatty acids in each phospholipid class.