Effect of reproductive states on lipid mobilization and linoleic acid metabolism in mammary glands

Effects of pregnancy and lactation on lipid metabolism in mouse mammary fat pads and nonmammary adipose tissues have been studied. In order to address the question whether the influence of hormonal milieu on lipid metabolism in mammary epithelial cells during pregnancy and lactation is the same as in fat cells, we have studied the mobilization of lipids and metabolism of fatty acids in the intact mammary glands, parenchyma-free mammary fat pads and in the perimetrial fat tissues of virgin, pregnant and lactating mice. Compared to parenchyma-free mammary fat pads, the perimetrial adipose tissues accumulated 5-fold higher levels of triglycerides during pregnancy. Mammary fat cells maintained overall lipid levels during pregnancy and lactation (16–20 μg/fat pad). In contrast, lactation depleted total lipid stores from 108 ± 5 to 24 ± 4.5 μg/fat pad in perimetrial fat pads. Results of comparative analysis of fatty acid composition of mammary fat pads, with and without epithelial tissue, from virgin and lactating mice showed stimulation of 18∶2ω6 metabolism leading to 130% increase in the ratio 20∶4ω6 to 18∶2ω6 in the epithelial compartment. Pregnancy and lactation resulted in the elevation of 20∶4ω6 levels probably due to a 4-fold increase in Δ5 desaturase activity and a decrease in oxidative degradation of 18∶2ω6. These results suggest that, unlike other adipose tissues, the metabolic pathways in mammary fat cells are not dedicated to sequestration and accumulation of dietary lipids during pregnancy. Lactation favors mammary epithelial cell-stimulated production of precursors of eicosanoids which are known to have agonist-like effect on mammary epithelial cells.     

On the membrane phospholipids and their acyl group profiles of adrenal gland

The phospholipid composition and their acyl group profiles from subcellular fractions of guinea pig adrenal gland and the same fractions from the cortex and medulla of the bovine gland were compared. The phospholipids of guinea pig adrenal were enriched in diacyl-glycerophosphocholines (GPC) which comprised over 50% of the total phospholipids, but the proportions of ethanolamine and choline plasmalogens, sphingomyelin and diacyl-glycerophosphoserine (GPS) were lower in guinea pig adrenals as compared to the bovine adrenals. In the bovine adrenal, sphingomyelin and diacyl-GPS were enriched in the medulla, whereas diacyl-glycerophosphoinositol (GPI) were enriched in the cortex. Although lysolecithin was present (up to 4.5%) in the bovine adrenal, only trace amounts of this lipid were detected in the guinea pig adrenal. Characteristic acyl group profiles were found associated with each type of the phosphoglycerides in adrenal membranes. However, acyl group profiles of the phosphoglycerides were not greatly different either between the bovine and guinea pig adrenal or with respect to the type of subcellular membranes isolated. Diacyl-GPC were enriched in 16∶0 and 18∶1, but also contained considerable amounts of 18∶0, 18∶2 and 20∶4. Diacyl-GPE were enriched in 18∶0, 18∶1 and 20∶4, while diacyl-GPI, diacyl-GPS, as well as alkenylacyl-GPE, were enriched in 20∶4. The lysolecithin from bovine adrenal membranes contained mainly 16∶0, 18∶0 and 18∶1 with only trace amounts of the polyunsaturated fatty acids. Other polyunsaturated fatty acids, such as 22∶4 and 22∶6, are apparently not prominent in the phosphoglycerides from either the bovine or the guinea pig adrenal gland.     

Fatty acid composition at the 2-position of ether-linked and diacyl ethanolamine and choline phosphoglycerides of human brain tumors

The acyl composition of ethanolamine and choline phosphoglycerides from a series of human brain tumors was determined and compared to that of normal human gray matter. Six glioblastomas, one astrocytoma, one oligodendroglioma, and one meningioma were analyzed. The total fatty acid composition of ethanolamine phosphoglycerides generally had a higher percentage of 18∶1, 18∶2ω6, and 22∶5ω3 and a lower percentage of 22∶6ω3 than that of normal gray matter. Choline phosphoglycerides from the tumors also contained a higher than normal percentage of 18∶2ω6. Separate analysis of the acyl groups at the 2 position of the diacyl and ether-linked components of the phosphoglycerides revealed that the diacyl component of ethanolamine phosphoglyceride from the tumors had lower than normal amount of 22∶6ω3 and a higher than normal amount of 18∶1 and 18∶2ω6. The acyl composition of ether-linked ethanolamine phosphoglycerides genearally contained a higher percentage of 20∶4ω6 and a lower percentage of 18∶1 compared to the corresponding fraction from normal gray matter. The astrocytoma analyzed had fatty acid profiles similar to those of the control with the exception of a greater 18∶2ω6 content. These data demonstrate that the composition of the acyl moiety at the 2 position of diacyl and ether-linked phosphoglycerides of brain tumors differs from the corresponding component from normal gray matter and that the ether-linked ethanolamine phosphoglycerides provide an important pool of polyunsaturated fatty acids from brain tumor phospholipids.     

Lipid composition of yoshida ascites hepatoma and of livers and blood plasma from host and normal rats

The lipid composition of Yoshida ascites hepatoma cells was analyzed together with that of ascitic plasma and of livers and blood plasma from host and normal rats. In comparison to normal livers, host livers showed no significant differences in the content of the various lipid classes, but contained a higher percentage of palmitic acid and a lower proportion of arachidonic acid in the major phospholipid classes. In addition, tumor growth induced a marked hypertriglyceridemia in host animals; changes in the concentration of other plasma lipid classes were not statistically significant. The ascitic plasma contained small amounts of lipids mainly constituted by cholesteryl esters and phospholipids. Yoshida hepatoma cells contained less phospholipids in comparison to both host and normal liver, while the increased level of triglycerides and the decrease of free fatty acids were not statistically significant. Hepatoma cells showed appreciable amounts of ether-linked lipids associated in part to neutral lipids (as glyceryl ether diesters) and, in part, to ethanolamine and choline phosphoglycerides. The alkyl groups in GEDE as well as in ethanolamine and choline phosphoglycerides were mainly constituted by C_16∶0 and C_18∶0 followed by C_18∶1. The alk-1-enyl groups in ethanolamine and choline phosphoglycerides were C_16∶0 and C_18∶0 with only a minor proportion of C_18∶1. In comparison to both host and normal liver, Yoshida hepatoma cells showed significant changes in the fatty acid composition of neutral lipids and phospholipids. Some of the major changes consisted of an increase of monoenoic acids associated with a decrease of arachidonic and docosahexaenoic acids in phosphatidylethanolamine, phosphatidylcholine, and phosphatidylinositol.     

Alterations in fatty acid composition of tissue phospholipids in the developing retinal dystrophic rat

Alterations in lipid composition occur in the retinal pigment epithelium and photoreceptor cells of the Royal College of Surgeons (RCS) dystrophic rat, a model for inherited retinal degeneration. With respect to lipid composition of nonretinal tissues, the developmental timing of lipid alterations and the incidence of dystrophy are unknown. We determined the fatty acid composition in choline phosphoglycerides (ChoGpl) and ethanolamine phosphoglycerides (EtnGpl) in the brain, liver, and retina from dystrophic RCS rats and from their nondystrophic congenics (controls) at the ages of 3 and 6 wk. At 3 wk, the fatty acid compositions were specific to individual phospholipid classes without any difference between dystrophic and nondystrophic tissues. In plasma phospholipids, there was an age-related increase in the relative contents of monounsaturated and n-3 polyunsaturated fatty acids, with only minor differences between dystrophic and nondystrophic rats. At 6 wk, the fatty acid compositions in ChoGpl and EtnGpl from dystrophic brain and retina were significantly different from those of nondystrophics. The effect of strain on developmental changes in brain fatty acid composition was significant for 18∶0 and 22∶6n−3 in EtnGpl and for 16∶0, 18∶0, 18∶1n−9, and 20∶4n−6 in ChoGpl. The brain ChoGpl fatty acid composition in nondystrophic rats was similar at 6 wk to that of normal rats, and there were almost no postweaning changes in the dystrophics. In retinal phospholipids, the effect of dystrophy was to increase the 20∶4n−6 content in EtnGpl and to decrease 22∶6n−3 in ChoGpl. The 18∶2n−6 and 22∶6n−3 contents in dystrophic liver ChoGpl were also significantly affected, while no difference was observed in the EtnGpl fraction. The dystrophy affected the phospholipid fatty acid developmental changes in a tissue- and class-specific manner. Fatty acid metabolism could be selectively altered in neural and nonneural tissues of developing dystrophic RCS rats.     

The acyl and Alk-1-enyl groups of the major phosphoglycerides from ox brain myelin and mouse brain microsomal,mitochondrial and myelin fractions

The major phosphoglycerides from ox brain myelin and mouse brain microsomal, mitochondrial and myelin fractions were separated by preparative thin layer chromatography. Alk-1-enyl groups from the alk-1-enyl acyl glycerophosphorylethanolamines were reacted with 1,3-propanediol to form the 1,3-dioxolane derivatives. Acyl groups were converted to the methyl ester derivatives and the acyl groups from alk-1-enyl acyl glycerophosphorylethanolamines and diacyl glycerophosphorylethanolamines were also determined separately. The acyl and alk-1-enyl group compositions of the phosphoglycerides from microsomal and mitochondrial fractions were quite similar. The ethanolamine and serine phosphoglycerides contained large amounts of 18∶0, 18∶1, 20∶4 and 22∶6 acyl groups. The choline phosphoglycerides had small amounts of polyunsaturated acyl groups and large amounts of 16∶0, 18∶1 and 18∶0 acyl groups. The mitochondrial cardiolipins contained unusual amounts of several acyl groups including 18∶1, 52%; 18∶2, 6%; and 16.1, 4%. A large portion of the mouse brain 18∶2 is in that fraction. The myelin phosphoglycerides were deficient in saturated and 22∶6 groups and markedly enriched in 18∶1 and 20∶1 groups when compared with the corresponding microsomal or mitochondrial phosphoglycerides. Presented in part at the AOCS Meetings, New York, October 1968 and San Francisco, April 1969.     

Effects of acute administration of chlorinated water on liver lipids

An acute administration of chlorinated water to rats caused “fatty liver” and indicated a more than 2-fold increase in liver triacylglycerols at 2 days after administration. The acyl group composition of triacylglycerols and phospholipids in both liver mitochondria and liver whole homogenate were also altered by the chlorine treatment. Among the phospholipid acyl groups, there was an increase in the proportion of 20∶4 but a decrease in most other polyunsaturated acyl groups. The acyl group changes were more obvious with phosphatidylcholines than with phosphatidylethanolamines. Other phospholipids, including cardiolipin in the mitochondrial membranes, were not greatly altered. Both morphological and biochemical changes were maximum at 2 days after the treatment and were fully recovered after 10 days. The disturbance of a number of enzymatic processes in the liver membranes may account for a large part of the changes observed.     

Fatty acid interrelationships in plasma,liver, muscle and adipose tissues of cattle fed safflower oil protected from ruminal hydrogenation

Steers were given diets containing formaldehyde-treated casein-safflower oil supplements, in which the constituent 18∶2 was protected from ruminal hydrogenation. A similar group was given unsupplemented diets. The fatty acid compositions of plasma, liver, muscle and adipose tissue lipids were determined in both groups of cattle after 0, 2, 4 and 8 weeks of experimentation. The proportion of 18∶2 in the triglycerides was markedly increased on feeding the supplement and the rate of incorporation into the plasma triglycerides was higher than that in the triglycerides of muscle and adipose tissue. Associated with this increase there were compensatory decreases in the proportions of 16∶0 and 18∶1 but no consistent change in the proportion of 18∶0. The proportion of 18∶2 in the plasma phospholipids and cholesteryl esters was initially much higher than in the triglycerides and this was further increased by feeding the safflower oil supplement. A linear relationship existed between the proportion of 18∶2 in the phospholipids and cholesteryl esters of plasma. The supplement also caused substantial increases in the proportion of 18∶2, both in phospholipids from liver and muscle and in cholesteryl esters from liver, and there were compensatory decreases in the proportions of other unsaturated fatty acids, e.g., 18∶1, 18∶3, 22∶6. These studies demonstrate that when ruminal hydrogenation was circumvented by feeding formaldehyde-treated casein-safflower oil particles, the linoleic acid was absorbed and the pattern of incorporation into plasma and tissue lipids was similar to that in nonruminants.     

Thyroid control over biomembranes: VI. Lipids in liver mitochondria and microsomes of hypothyroid rats

The lipids of liver mitochondria prepared from normal rats and from rats made hypothyroid by thyroidectomy and injection with¹³¹INa contained similar amounts, per mg protein, of total lipids, phospholipids, neutral lipids and lipid phosphorus. Hypothyroidism caused a doubling of the relative amounts of mitochondrial cardiolipins (CL; to 20.5% of the phospholipid P) and an accompanying trend (although statistically not significant) toward decreased amounts of both phosphatidylcholines (PC) and phosphatidylserines (PS), with phosphatidylethanolamines (PE) remaining unchanged. The pattern of elevated 18∶2 fatty acyl content and depleted 20∶4 acyl groups of the mitochondrial phospholipids of hypothyroid preparations was reflected to varying degrees in the resolved phospholipids, with PC showing greater degrees of abnormality than PE, and CL showing none. Hypothyroidism produced the same abnormal pattern of fatty acyl distributions in liver microsomal total lipids as was found in the mitochondria. Hypothyroid rats, when killed 6 hr after injection of [1-¹⁴C] labeled linoleate, showed the following abnormalities: the liver incorporated less label into lipids, and converted 18∶2 not exclusively to 20∶4 (as normals do) but instead incorporated the label mainly into saturated fatty acids. These data, together with the known decrease in β-oxidation, suggest that hypothyroidism involves possible defective step(s) in the conversion of 18∶2 to 20∶4. These studies were initiated during a leave at the University of California, Los Angeles.     

In vitro incorporation of elongated fatty acyl products into lipid classes in the housefly,Musca domestica L. and the American cockroach,Periplaneta americana (L.)

Thein vitro incorporation of elongated fatty acyl products into various lipid classes was studied in the American cockroach,Periplaneta americana (L.) and the houseflyMusca domestica L. Stearoyl-CoA (18∶0-CoA) and linoleoyl-CoA (18∶2-CoA) were each elongated in microsomal preparations from abdominal epidermal tissue of the adult cockroach. Incorporation of radioactive tracer into different lipid classes was determined by thin-layer chromatography (TLC). In the American cockroach, 40–45% of the total radioactive label was incorporated into the free fatty acid fraction, with smaller amounts in the triglyceride (12–31%) and phospholipid (12–19%) fractions. Of the elongated products analyzed by radio-high performance liquid chromatography (HPLC), 53–60% was found in the free fatty acid fraction. In the housefly, the substrates 18∶0-CoA and 18∶1-CoA were used to determine into which lipids the elongated products would become incorporated. The saturated fatty acyl elongated products were found mainly in the free fatty acid (41%), triglyceride (23%), and acyl-CoA (17%) fractions. The monounsaturated fatty acyl elongated products were found in the triglyceride (44%), free fatty acid (11%), acyl-CoA (35%) and phospholipid (10%) fractions in three-day-old males. In three-day-old females, the elongated products were found in the triglyceride (45%), free fatty acid (28%), acyl-CoA (11%) and phospholipid (15%) fractions. From these data, it is not possible to determine the identity of the substrate for the conversion of the elongated fatty acyl products to the corresponding hydrocarbon (Hy). In the cockroach, incubations with 18∶0-CoA and with 18∶2-CoA resulted in small incorporations into 25∶0 Hy and into 27∶2 Hy, respectively. In the housefly, incubations with 18∶1-CoA resulted in a very small production of 27∶1 Hy in mature males and 23∶1 Hy in mature female houseflies. These data support the idea that the preparation of subcellular fractions results in an uncoupling of fatty acid chain elongation from the conversion of the fatty acid to the corresponding hydrocarbon in both insects.     

Membrane lipid profile of an edible basidiomycete <Emphasis Type="Italic">Lentinula edodes</Emphasis> during growth and cell differentiation

The basidiomycetous mushroom Lentinula edodes (Shiitake) exhibits a unique process of cell differentiation termed “fruiting-body formation”. To clarify the relationship between membrane lipids and fruiting-body formation in this fungus, we investigated variations in levels of phospholipids, cerebrosides, fatty acyl residues in the major phospholipids, and fatty acyl and sphingoid base residues in cerebrosides during vegetative growth and fruiting-body formation. PC, PE, and PS were the primary phospholipids in the cells of L. edodes. After a shift in growth temperature of L. edodes mycelia has been shifted from 25 to 18°C, the proportion of unsaturated FA (UFA), such as linoleic acid (18∶2) and oleic acid (18∶1), increased. In contrast, during fruiting-body formation induced by the temperature downshift to 18°C, 18∶2 of PC in the primordia and fruiting bodies decreased, and the UFA of PF and 18∶1 of PC increased compared with the proportions in mycelia growing at 18°C. These results showed that the proportions of fatty acyl residues in PC and PE differed during fruiting-body formation in L. edodes. Moreover, the amount of cerebrosides in primordia increased compared with those in mycelia and fruiting bodies and, in these differentiating tissues, the proportion of 2-hydroxypentadecanoic acid increased whereas that of 2-hydroxyoctadecanoic acid decreased compared with that in the mycelia. However, the proportion of sphingoid base residues in cerebrosides did not change during fruiting-body formation in L. edodes.     

Composition of phospholipids of white muscle of six tuna species

A comparative study of the phospholipids of white muscle of six of the comercially utilized tuna species, including quantitative analyses of phospholipid classes and studies of the acyl composition of the major components. Plasmalogen compounds also were identified and quantified. Choline and ethanolamine glycerophospholipids were the most abundant classes in all the samples, as well as the only molecules containing plasmalogens (16∶0, 18∶0, and 18∶1 alkenyl ether chains). The patterns of fatty acid distribution within each of the phospholipid classes showed general similarities in the species analyzed. However, ratios between certain saturated and polyunsaturated fatty acids in different phospholipid classes showed remarkable diffences. The high content of n−3 polyunsaturated fatty acids in the principal phospholipids, such as the plasmalogens, and taking into account the fatty acids possible importance in human nutrition, indicates that the white muscle of tuna species may be a potentially important dietary item.     

Isolated brain capillary endothelia: Influence of various levels of essential fatty acids on the acyl group composition of glycerophospholipids

On day seven of gestation, Wistar rats were assigned to a high essential fatty acid (EFA), low EFA, or a fat free diet. The same diets were continued during lactation. On weaning, the offspring were fed the same diets as their mother. Rats were killed at 222 days, brain capillary endothelia isolated, and total lipids extracted from the purified capillaries. The composition of the constituent fatty acids of ethanolamine glycerophospholipid (EGP), choline glycerophospholipid (CGP), and the alk-1-eny EGP composition from each diet is reported. A decrease in dietary EFA led to reduced proportions of total saturated acyl groups in EGP with no change observed in the total saturated acyl groups from CGP, and an increase in monoenoic fatty acids, particularly 18∶1n−9 for each phospholipid class. The proportions of 20∶4n−6 in alk-1-enyl EGP were reduced in fat-free fed animals. In addition, the relationship between 20∶3n−9 and 20∶4n−6 fatty acids in brain capillary endothelia were markedly increased with a reduction in dietary fat. Low EFA and fat deficient animals showed a tendency to sequester 22∶6n−3.     

Fatty acid composition of subcellular particles from sheep platelets and topological distribution of phosphatidylethanolamine fatty acids in the plasma membrane

The fatty acid composition of individual phospholipids in subcellular fractions of sheep platelets and the asymmetrical distribution of phosphatidylethanolamine (PE) fatty acyl chains across the plasma membrane were examined. The main fatty acids of total lipid extracts were oleic (18∶1; 32–41%), linoleic (18∶2, 10–17%), stearic (18∶0; 13–15%), palmitic (16∶0; 11–15%) and arachidonic (20∶4; 8–12%) acids, with a saturated/unsaturated ratio of about 0.4. Each phospholipid class had a distinct fatty acid pattern. Sphingomyelin (SM) showed the highest degree of saturation (50%), with large proportions of behenic (22∶0), 18∶0 and 16∶0 acids. The main fatty acid in PE, phosphatidylserine (PS) and phosphatidylcholine (PC) was 18∶1n−9. Our findings suggest that fatty acids are asymmetrically distributed between thecholineversus the non-choline phospholipids, and also between plasma membranes and intracellular membranes. The transbilayer distribution of PE fatty acids in plasma membranes from non-stimulated sheep platelets was investigated using trinitrobenzenesulfonic acid (TNBS). A significant degree of asymmetry was found, which is a new observation in a non-polar cell. The PE molecules from the inner monolayer contained higher amounts of 18∶2 and significantly less 18∶1 and 20∶5 than those found in the outer monolayer, although no major differences were detected in the transbilayer distribution of total unsaturatedversus saturated PE acyl chains.     

Incorporation of arachidonic,dihomogamma linolenic and eicosapentaenoic acids into cultured V79 cells

The uptake and distribution of three common dietary polyunsaturated fatty acids was studied using Chinese hamster lung fibroblasts (V79 cells). Treatment of V79 cells with arachidonic (20∶4), eicosapentaenoic (20∶5) and dihomogammalinolenic (20.3) acids for 24 hr produced a marked uptake of 20∶3 and 20∶4, both of which were assimilated to a considerably greater degree than 20∶5. All polyunsaturated fatty acids were incorporated primarily into phospholipids; however, there were considerable differences in their distribution into individual phospholipid species. Although 20∶4 was incorporated primarily into phosphatidylcholine, 20∶3 entered largely into phosphatidylethanolamine and phosphatidylglycerol, and 20∶5 was distributed about equally between phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol. A marked conversion of 20∶3 to 20∶4 was found after 24 hr and, in several phospholipids, there was as much derived-radiolabeled 20∶4 as there was radiolabeled 20∶3. There was little evidence of 20∶4 and 20∶5 metabolism. V79 cells undergo substantial changes in phospholipid fatty acid composition following supplementation with these polyunsaturated fatty acids; however, these fatty acids are assimilated to different degrees and their distribution among cellular phospholipids is distinct, suggesting incorporation via independent mechanisms.     

Differences in the phospholipid,cholesterol, and fatty acyl composition of 3T3 and SV3T3 plasma membranes

An analysis of the phospholipid, cholesterol, and phospholipid fatty acyl composition of isolated plasma membranes of 3T3 and SV3T3 mouse embryo cells has been performed. The results show that the plasma membrane of SV3T3 cells contain relatively less phosphatidylethanolamine and sphingomyelin and more cholesterol than 3T3 plasma membranes. The fatty acyl composition of individual phospholipid classes as determined by gas liquid chromatography also showed differences between 3T3 and SV3T3 plasma membranes. The plasma membranes of SV40 transformed 3T3 cells contain: (a) a higher percentage of 18∶1 and less 20∶3 and 20∶4 in phosphatidylethanolamine; (b) a higher percentage of 18∶1 in phosphatidylserine; and (c) a higher percentage of 18∶2 and 20∶4 in phosphatidylinositol.     

Effect of low intake of n−3 fatty acids during development on brain phospholipid fatty acid composition and exploratory behavior in rats

The effect of dietary restriction of n−3 fatty acids during development on brain phospholipid fatty acid composition and exploratory behavior has been studied in male Sprague Dawley rats. Female rats were fed semipurified diets containing either 5.5% safflower oil or 6% soybean oil for 6 wk prior to mating and throughout gestation and lactation. Control rats were maintained on laboratory chow. The male pups were weaned to the diets of the dams except for one group which was switched from safflower to soybean oil at weaning. Behavioral studies and brain phospholipid analyses were conducted at 16–18 wk of age. Rats fed safflower oil showed significantly lower levels of 22∶6n−3 in phospholipids of synaptic membranes and myelin than rats fed soybean oil or chow. The decrease in 22∶6n−3 was compensated for by an increase in 22∶5n−6, the total content of polyunsaturated fatty acids remaining approximately constant. The brain phospholipid fatty acid composition of rats switched from safflower to soybean oil at weaning was similar to that of rats fed soybean oil throughout the experiment. There was no difference in spontaneous locomotor activity among the different dietary groups. However, rats raised on safflower oil displayed a significantly lower exploratory activity (horizontal movements and rearings) in a novel environment than rats fed soybean oil or chow. In contrast to the brain phospholipid fatty acid composition, there was no recovery of exploratory behavior in rats raised on safflower oil and switched to soybean oil at weaning suggesting a specific requirement of n−3 fatty acids during development.     

The fatty acid and aldehyde composition of the major phospholipids of mouse brain

Phospholipid classes were separated from mouse brain lipid extracts by preparative thin-layer chromatography (TLC). Methyl esters were prepared from the intact phospholipids by direct transesterification at room temperature in the presence of silica gel by using 0.5m NaOH-methanol in order to prevent interference by aldehydes or derivatives. Dimethyl acetal derivatives of phosphoglyceride alkenyl ethers (alkenyl moiety with a double bond in 1,2-position relative to oxygen linkage) were prepared, using 5% concentrated HCl in methanol, followed by preparative TLC for isolation. The major phospholipids present were ethanolamine phosphoglycerides (EPG) 39.8%, choline phosphoglycerides (CPG) 39.7%, serine phosphoglycerides (SPG) 15.0%, and sphingomyelin (Sph) 5.4%. One-fifth of the total phospholipids (PL) were in the form of plasmalogens, mainly EPG. Choline and serine plasmalogens were present in trace quantities. The major aldehyde components of the plasmalogens were 16∶0, 18∶0, and 18∶1. The EPG were rich in long-chain poly-unsaturated fatty acids, including 28.8% of 22∶6 and 17.0% of 20∶4, but contained only 7.2% of 16∶0. In contrast, the CPG contained 39.6% of 16∶0, and 31.0% of 18∶1 with a small content of polyunsaturated fatty acids. The SPG exhibited a still different pattern containing 38.2% of 18∶0, 23.2% of 18∶1, 24.3% of 22∶6, 2.9% of 16∶0, and 3.8% of 20∶4. Presented in part at the AOCS Meeting, New Orleans, May 1967.     

Enhancement of G protein-coupled signaling by DHA phospholipids

The effect of phospholipid acyl chain and cholesterol composition on G protein-coupled signaling was studied in native rod outer segment (ROS) disk and reconstituted membranes by measuring several steps in the visual transduction pathway. The cholesterol content of disk membranes was varied from 4 to 38 mol% cholesterol with methyl-β-cyclodextrin. The visual signal transduction system [rhodopsin, G protein (G_t), and phosphodiesterase (PDE)] was reconstituted with membranes containing various levels of phospholipid acyl chain unsaturation, with and without cholesterol. ROS membranes from rats raised on n−3 fatty acid-deficient and-adequate diets were also studied. The ability of rhodopsin to form the active metarhodopsin II conformation and bind G_t was diminished by a reduction in the level of DHA (22∶6n−3) acyl chains or an increase in membrane cholesterol. DHA acyl chain containing phospholipids minimized the inhibitory effects of cholesterol on the rate of rhodopsin-G_t coupling. The activity of PDE, which is a measure of the integrated signal response, was reduced in membranes lacking or deficient in DHA acyl chains. PDE activity in membranes containing docosapentaenoic acid (DPA, 22∶5n−6) acyl chains, which replace DHA in n−3 fatty acid deficiency, was 50% lower than in DHA-containing membranes. Our results indicate that efficient and rapid propagation of G protein-coupled signaling is optimized by DHA phospholipid acyl chains.     

New findings in the fatty acid composition of individual platelet phospholipids in man after dietary fish oil supplementation

Nine healthy male volunteers were given 15 Max EPA fish oil capsules providing 2.67 g of eicosapentaenoic acid (EPA, 20∶5ω3) and 1.72 g of docosahexaenoic acid (DHA, 22∶6ω3) daily for 3 wk. Measurements were taken at baseline, at the end of the fish-oil period, and at 2 and 6 wk postsupplementation. The effect of fish oil on plasma lipids and the fatty acid composition of individual platelet phospholipids was studied. In general, the proportions of 20∶5ω3 and 22∶6ω3 in platelet phosphoglycerides were substantially increased mainly at the expense of arachidonic acid (AA, 20∶4ω6). A large and significant increase in the relative EPA content of phosphatidylcholine (PC) (P<0.001) and phosphatidylethanolamine (PE) (P<0.001) was noted at the end of the 3 wk supplementation. We have also shown for the first time a small but significant (P<0.001) incorporation of EPA in phosphatidylserine (PS). Incorporation of DHA was also detected in PC, PE and PS, whereas the relative AA content of these phospholipids was significantly reduced. Fish oil supplementation led to a significant increase of 22∶5ω3 in PS and decreases of 20∶3ω6 in PC and 22∶4ω6 in PE. Postsupplementation measurements showed a gradual return of all fatty acids to baseline levels. The fatty acid composition of the phosphatidylinositol (PI) fraction remained unchanged throughout the trial period. We conclude that in humans ω3 fatty acids are incorporated into platelet membrane phospholipid subclasses with a high degree of specificity.