delta 15,18-tetracosadienoic acid content of sphingolipids from platelets and erythrocytes of animals fed diets high in saturated or polyunsaturated fats

The effect of a Tropaeolum speciosum oil supplement on the nervonic acid content of sphingomyelin in rat tissues

The lipids of Tropaeolum speciosum (T. speciosum) are a rich source of naturally occurring nervonic acid (24:1n-9). We report that adding a T. speciosum oil supplement to a semi-purified diet significantly increased the amount of 24:1n-9 in liver and heart, but not brain, sphingomyelin (SM) of young rats. The bioavailability of 24:1n-9 from the lipids of T. speciosum was similar to that of 24:1n-9 ethyl ester in this rat bioassay.

Effects of feeding Lunaria oil rich in nervonic and erucic acids on the fatty acid compositions of sphingomyelins from erythrocytes, liver, and brain of the quaking mouse mutant

Feeding an oil from Lunaria biennis rich in 22:1n-9 and 24:1n-9 to homozygous quaking (qk.qk) mice caused a large increase in the percentage of 24:1n-9 and corresponding decreases in the percentage of 24:0 and 22:0 in sphingomyelins from liver, erythrocytes, and milk. Brain sphingomyelin from 2-wk-old qk.qk pups born to qk.qk mothers maintained on the Lunaria oil had essentially normal percentage of 24:1n-9 and 18:0, in contrast to pups born to mothers maintained on a control oil rich in 18:1n-9 whose brain sphingomyelin had a markedly reduced percentage of 24:1n-9 and an increased percentage of 18:0. After 2 wk and up to and beyond weaning, the qk.qk pups from Lunaria-fed mothers weaned on to the Lunaria diet had a markedly decreased percentage of 24:1n-9 in their brain sphingomyelin, accompanied by an increased percentage of 18:0, as compared to heterozygous quaking mice. However, the percentage of 24:1n-9 in brain sphingomyelin in qk.qk pups weaned on to the Lunaria diet continued throughout this period (2-8 wk postbirth) to be significantly higher than in qk.qk pups weaned on to the control diet. We conclude that dietary 24:1n-9 influences the fatty acid composition of brain sphingomyelin in qk.qk mice, but only via the mother in pre- or early postnatal animals. We further consider that the dietary effects may be elicited mainly in the sphingomyelin of nonmyelinated brain cells, and that the nervonic acid in myelin sphingomyelin may be formed mainly by chain elongation in oligodendrocytes from shorter chain fatty acid precursors.

The occurrence of Iso 24:0 (22-methyltricosanoic acid) fatty acid in sphingomyelin of rat tissues

The occurrence of an unusual fatty acid, iso 24:0 (22-methyltricosanoic acid), has been shown to be present in the sphingomyelin from rat liver by gas liquid chromatography-mass spectrometry. The fatty acid is also present in the sphingomyelin of rat tissues tested, except for brain and fetal serum. Supplementation of diets with L-valine elevated the content of iso 24:0 in rat liver, heart, and kidney sphingomyelin. The fatty acid appears to be present in sphingomyelin of the sera of mice, dogs, and cats, but not humans.

Dietary very long chain fatty acids directly influence the ratio of tetracosenoic (24:1) to tetracosanoic (24:0) acids of sphingomyelin in rat liver

Twenty-one groups of weanling male Wistar rats were fed semipurified diets containing 5% (w/w) of different dietary fats. After 2 wk, liver sphingomyelin (SM) fatty acid composition was determined. The ratio of 24:1 to 24:0 in liver SM varied over a tenfold range in response to dietary fat type. Step-wise multiple regression analysis indicated that dietary 24:1, 24:0, and 22:1 were the most significant factors in predicting the 24:1/24:0 ratio of liver SM. The mathematical relation between the dietary fatty acid composition and liver SM 24:1/24:0 was y = 1.88 (24:1) -1.49 (24:0) +0.21 (22:1) +0.01 (18:1) +0.26, r2 = 0.95, P < 0.0001. These results were confirmed by a second experiment in which the rats were fed olive oil-based diets supplemented with various fatty acid ethyl esters.

Metabolism of 3-[3H]sphingosine sphingomyelin labeled with [14C]palmitic or [14C]linoleic acid by Hep G2 cells and rat liver in vivo

The metabolism of sphingomyelin labeled with 3-[3H]sphingosine and [14C]16:0 or [14C]18:2 fatty acid was studied in cultured Hep G2 cells or macrophages and after injection into rats. In pulse-chase experiments, the loss of 3H and 14C-label was more rapid when the cells had been pulsed with 18:2 than with 16:0 sphingomyelin. At the end of 24 h chase, the labeled ceramide contained more [14C]18:2 fatty acid than [14C]16:0. In addition, the 3H-label derived from 3-[3H]sphingomyelin was recovered also as free sphingosine. After injection in vivo, more [3H]sphingosine-labeled sphingomyelin was present in the liver 3 and 24 h after injection of 16:0 than after injection of 18:2 sphingomyelin. The ratio of [3H]ceramide derived from 16:0 sphingomyelin to that derived from 18:2 sphingomyelin as percent of injected dose was 1.84 3 h after injection and 1.31 after 24 h. The ratio of 3H/14C in liver ceramide was 6.4 3 h after injection of 18:2 sphingomyelin and 3.4 after 16:0 sphingomyelin. The present results show that 3-[3H]sphingomyelin is metabolized quite extensively and that the fate of the sphingosine moiety is related to the type of fatty acid present in the phospholipid. These findings indicate that there is little or no reutilization of 18:2 ceramide for sphingomyelin formation and suggest that sphingosine derived from 18:2 sphingomyelin is channeled primarily for catabolism.

The effect of dietary zinc deficiency on the lipid composition of the rat erythrocyte membrane

The effect of dietary zinc deficiency in the rat on the lipid composition of the erythrocyte membrane was determined. Weanling male Wistar rats were fed an egg white-based diet containing less than 1.0 mg Zn/kg diet ad libitum. Control rats were either pair-fed or ad libitum-fed the basal diet supplemented with 100 mg Zn/kg diet. A zinc refed group was fed the -Zn diet until day 18 and then pair-fed the +Zn diet until day 21. The voluntary feed restriction associated with dietary zinc deficiency resulted in erythrocyte membranes that had depressed phospholipid/protein and elevated cholesterol/phospholipid ratios. Similarly, all feed restricted groups had elevated 22-carbon n-3 polyunsaturated fatty acids (PUFA) and depressed 22-carbon n-6 PUFA concentrations in alkenyl-acyl and diacyl glycerophosphoethanolamine, phosphatidylserine and phosphatidylcholine; they also had depressed 24:2n-6 levels in sphingomyelin. The relative concentrations of phospholipids in the membrane was similar between -Zn and +Zn (ad libitum) groups; however, the -Zn group had significantly less phosphatidyl-serine relative to +Zn (pair-fed) controls.

Influence of saturated and unsaturated fats on platelet fatty acids in cholesterol-fed rabbits

Feeding natural fats varying in contents of palmitate (16:0), stearate (18:0), oleate (18:1), and linoleate (18:2) to rabbits resulted in modulation of platelet phospholipid fatty acyl composition. Rabbits were fed high fat semipurified diets containing 2% corn oil (CO) + 18% CO, cocoa butter (CB) or milkfat (M) for periods of up to 300 d. Platelet phospholipid linoleate contents corresponded to diet levels with 18:2 highest in CO-fed rabbits and following the sequence CO greater than CB greater than M. Stearate was highest in CB-fed rabbits, corresponding to high 18:0 levels in CB, but palmitate levels were not affected by diet. Both CB and M-fed rabbits were higher than CO-fed rabbits in oleate. Though CO is highest in 18:2, the accepted 20:4 precursor, arachidonate was highest in M-fed rabbits. Adding cholesterol (0.2%) to the diets did not affect platelet phospholipid fatty acyl composition except to elevate 20:4 in M-fed rabbits. CO-fed rabbits showed uniquely high levels of tetracosadienoate (24:2). Fatty acyl composition data were essentially constant between 200 and 300 d on diet. Phospholipid fatty acyl unsaturation was apparently homeostatically controlled as mole percent unsaturate to saturate ratios were independent of diet. The observed homeostasis resulted in minimal diet influences on platelet membrane fluidity and ADP or collagen stimulated platelet aggregation. Platelet fluidity, determined by fluorescence polarization, was a function of oleate and linoleate contents of the cells. Cholesterol feeding generally lowered platelet fluidity and altered the dependence of fluidity on fatty acyl composition.

Biotin-responsive immunoregulatory dysfunction in multiple carboxylase deficiency

The immunoregulatory system has recently been shown to require prostaglandins (PG) for its activation in man. We report here an impairment of immunoregulatory function, due to defective PGE monocytic production, in a 12-month-old boy with multiple carboxylase deficiency (MCD). The abnormal immune-response was corrected in vitro by adding PGE to the medium. Moreover, PGE deficiency and immunoregulatory dysfunction responded to biotin administration in vivo. It is suggested that the PGE deficiency in MCD could result from an impaired activity of a biotin enzyme, acetyl CoA carboxylase, since the product of this enzyme reaction, malonyl CoA, is required for prostaglandin synthesis.

Effect of cholesterol supplementation of diets of thyroidectomized dogs on the fatty acid composition of erythrocyte phospholipids and plasma phosphatidylcholine

Thyroidectomized foxhounds were fed: (a) a control diet, (b) the control diet supplemented with 15% beef tallow or cottonseed oil, with or without added cholesterol, or (c) the control diet supplemented with beef tallow (15%), safflower oil (1.5%) and cholesterol. After 23 weeks on the diet, the content of the individual phospholipids of the erythrocytes was not altered appreciably. However, supplementing either the saturated (beef tallow) or polyunsaturated (cottonseed oil) diets with cholesterol produced similar changes in the fatty acid compositions of the phospholipid classes. Most consistently, there were increases in the percentages on 18:2 omega 6 and 20:3 omega 6 and decreases in the percentages of 20:4 omega 6 and 22:4 omega 6. Cholesterol supplementation of the diets similarly affected the fatty acid composition of phosphatidylcholine isolated from the platelet-free plasma of these animals.

Preparation of radiolabled tetracosa mono- and dienoic acid methyl esters from rat erythrocyte lipids by thin layer chromatography

An easy method of obtaining pure fatty acid methyl esters (FAME) of tetracosa mono- and dienoic acids (24:1, 24:2) using thin layer chromatography (TLC) is described. The total lipids isolated from rat erythrocytes were treated with methanolic-NaOH. Sphingomyelin was unaffected by this treatment and was separated from FAME of glycerolipids and cholesterol by TLC. FAME of sphingomyelin were then prepared by acid methanolysis. These esters migrated into 2 distinct bands on TLC. The slow moving band contained FAME of 16:0, 16:1, 18:0, 18:1, 19:0 and 20:0 wheras the fast moving band contained FAME of 22:0, 23:0, 24:0, 24:1 and 24:2. After AgNO3-TLC, the FAME of the fast moving band separated into 3 species; esters of saturated acids, 24:1 and 24:2, respectively. With erythrocyte lipids of rats fed a fat-free diet and injected with 14C-18:1, this method yielded 14C-24:1. From rats injected with 14C-18:2 and maintained on a corn oil diet, 14C-24:2 was obtained.

Effects of diets high in saturated fat and cholesterol on the lipid composition of canine platelets

The phospholipid composition of platelets from dogs on various experimental diets was determined. Thyroidectomized foxhounds were fed a control diet or the control diet supplemented with (1) beef tallow, (2) beef tallow and cholesterol, or (3) beef tallow, cholesterol, and safflower oil for 23 weeks prior to isolation of platelets. Platelets from animals fed the control diet contained 36.7% phosphatidylcholine (PC), 22.8% phosphatidylethanolamine (PE), 18.4% sphingomyelin (Sph), 11.8% phosphatidylserine (PS), 6.3% phosphatidylinositol (PI), and 2.2% lysophosphatidylcholine. The PE was 77.6% in the plasmalogen form. No highly significant changes in the phospholipid class composition resulted from the experimental diets. Cholesterol supplementation of the diets, however, caused consistent alterations in the fatty acid compositions of the platelet phospholipids including increases in the percentages of 18:1 omega 9 (oleic acid), 18:2 omega 6 (linoleic acid), and 20:3 omega 6 (homo-gamma linolenic acid) and a decrease in the percentage of 20:4 omega 6 (arachidonic acid). Addition of safflower oil to the tallow-cholesterol diet partially reversed these effects. These cholesterol-induced alterations in fatty acid composition could be due to exchange with plasma lipids, de novo synthesis, or altered platelet metabolism. The mechanism remains to be determined.