The effects of 2-bromopalmitate on the fatty acid composition in differentiating adipocytes of red sea bream (Pagrus major)

To determine whether external factors affect the adipogenic function of fish adipocytes, the effects of 2-bromopalmitate (a PPAR agonist) on the fatty acid composition in differentiating adipocytes of red sea bream were investigated in vitro. In the presence of 2-bromopalmitate, the red sea bream adipocytes were differentiated and the effects on the fatty acid composition and the adipogenic gene expression were analyzed. With the level of 2-bromopalmitate, the content of 16:1n-7, a delta-9 desaturation product, increased in association with the increase in a stearoyl CoA desaturase (SCD) gene expression level while the triglyceride accumulation was not affected. Subsequently, the effects on the bioconversion of the n-3 and n-6 fatty acids, which are main series of dietary essential fatty acids, were examined. In the presence of 300 μM of 18:3n-3 or 18:2n-6, red sea bream stromal-vascular cells accumulated the lipid in the cytoplasm within 3 days by the fatty acid uptake with the increase of corresponding fatty acid contents. Furthermore, in both the 18:3n-3 and 18:2n-6 stored cells, the products of delta-6 desaturation (18:4n-3 and 18:3n-6, respectively) and C_18–20 elongation (20:3n-3 and 20:2n-6, respectively) were detected. However, neither the delta-6 desatutration nor C_18–20 elongation of 18:3n-3 and 18:2n-6 were enhanced by 2-bromopalmitate treatment. In conclusion, the results indicate that the adipocyte function in fish, e.g. adipogenic gene expression and fatty acid composition, can be modified by external factors and a main effect of 2-bromopalmitate is the increase in the content of delta-9 desaturation product by stimulating the SCD gene expression.     

The fatty acid composition of the serum phospholipids of children with sickle cell disease in Nigeria

The purpose of this study was to determine the fatty acid composition of the serum phospholipids of children with sickle cell disease (SCD) in Nigeria and to compare the relative fluidity of the acyl chains of the serum phospholipids of controls versus the subjects with SCD. It is widely accepted that the fatty acid composition of an individual's serum phospholipids reflects that of their tissue phospholipids. An alteration in the fatty acid composition of membrane phospholipids could affect critical membrane-dependent enzymes and processes (e.g., ion and solute transport, hormone-receptor interactions, signal transduction pathways). We found a significant reduction in the content of polyunsaturated n-3 fatty acids in the phospholipids of subjects with SCD which could result in a reduction of the fluidity of their tissue membranes. Specifically, there was a 40-50% reduction in the proportion of total n-3 fatty acids in subjects with SCD. On the basis of calculated melting points and double bond indices of the acyl chains of the serum phospholipids, the phospholipids of the children with SCD are less fluid relative to those of their healthy counterparts. In addition, we determined that linoleic acid, arachidonic acid, and stearic acid were the major determinants of the fluidity of the acyl chains of the serum phospholipids of the healthy controls and children with SCD.     

Changes in molecular species profiles of glycosylphosphatidylinositol anchor precursors in early stages of biosynthesis

Glycosylphosphatidylinositol (GPI) anchor is a major lipidation in posttranslational modification. GPI anchor precursors are biosynthesized from endogenous phosphatidylinositols (PIs) and attached to proteins in the endoplasmic reticulum. Endogenous PIs are characterized by domination of diacyl species and the presence of polyunsaturated fatty acyl chain, such as 18:0-20:4, at the sn-2 position. In contrast, the features of mammalian glycosylphosphatidylinositol-anchored proteins (GPI-APs) are domination of alkyl/acyl PI species and the presence of saturated fatty acyl chains at the sn-2 position, the latter being consistent with association with lipid rafts. Recent studies showed that saturated fatty acyl chain at sn-2 is introduced by fatty acid remodeling that occurs in GPI-APs. To gain insight into the former feature, we analyzed the molecular species of several different GPI precursors derived from various mammalian mutant cell lines. Here, we show that the PI species profile greatly changed in the precursor glucosamine (GlcN)-acyl-PI and became very similar to that of GPI-APs before fatty acid remodeling. They had alkyl (or alkenyl)/acyl types with unsaturated acyl chain as the major PI species. Therefore, a specific feature of the PI moieties of mature GPI-APs, domination of alkyl (or alkenyl)/acyl type species over diacyl types, is established at the stage of GlcN-acyl-PI.     

Mitochondrial lipids in Bufo arenarum full-grown oocytes

Both the content and composition of polar and neutral lipids from the mitochondrial fraction of ovarian full-grown Bufo arenarum oocytes were analysed in the present study. Triacylglycerols (TAG) represent 33% of the total lipids, followed by phosphatidylcholine (PC), free fatty acids (FFA) and phosphatidylethanolamine (PE). Diphosphatidylglycerol (DPG) or cardiolipin, a specific component of the inner mitochondrial membrane, represents about 4% of the total lipid content. Palmitic (16:0) and arachidonic (20:4n6) acids are the most abundant fatty acids in PC and PE, respectively. DPG is enriched in fatty acids with carbon chain lengths of 18, the principal component being linoleic acid. In phosphatidylinositol (PI), 20:4n6 and stearic acid (18:0) represent about 72 mol% of the total acyl group level. The main fatty acids in TAG are linoleic (18:2), oleic (18:1), and palmitic acids. The fatty acid composition of FFA and diacylglycerols (DAG) is similar, 16:0 being the most abundant acyl group. PE is the most unsaturated lipid and sphingomyelin (SM) has the lowest unsaturation index.     

The aging human orbitofrontal cortex: decreasing polyunsaturated fatty acid composition and associated increases in lipogenic gene expression and stearoyl-CoA desaturase activity

Orbitofrontal cortex (OFC, Brodmann area 10) gray matter volume reductions and selective reductions in docosahexaenoic acid (DHA, 22:6n-3) are observed in adult patients with major depressive disorder (MDD). OFC gray matter volume also decreases with advancing age in healthy subjects. To examine if OFC gray matter DHA composition decreases during normal aging, we determined age-related changes in OFC gray matter fatty acid composition by gas chromatography in subjects aged 29-80 years (n=30). We additionally determined elongase (HELO1), delta-5 desaturase (FASD1), delta-6 desaturase (FASD2), peroxisomal (PEX19), and stearoyl-CoA desaturase (SCD) mRNA expression in the same tissues. Increasing age was associated with a progressive decline in polyunsaturated fatty acid (PUFA) composition, including DHA and arachidonic acid (AA, 20:4n-6), and transient, apparently compensatory, elevations in elongase and desaturase gene expression. The age-related reduction in PUFA composition was inversely correlated with SCD expression and activity resulting in elevations in monounsaturated fatty acid composition. These dynamic age-related changes in OFC gray matter fatty acid composition and biosynthetic gene expression may contribute to the progressive decline in OFC gray matter volume found with advancing age. The implications of age-related reductions in OFC PUFA composition for affective dysregulation in the elderly are discussed.     

Influence of saturated long-chain N-acylethanolamines on lipid composition and heart contractility of isolated rat heart under ischemia-reperfusion

The heart contractility and changes of lipid composition of isolated rat heart (n = 26) under total ischemia and ischemia-reperfusion was studied. The effect of N-stearoyl-ethanolamine under these conditions was investigated. N-stearoyl-ethanolamine leads to remodelling of fatty acyl chain composition of myocardial phospholipids: to drastic fall of polyunsaturated fatty acyl chains (18:2w6, 20:3w6, 20:4w6, 22:5w3, 22:5w6, 22:6w3 and 22:6w6) and enhancement of 18:0. This can be caused by N-stearoyl-ethanolamine-induced suppression of polyunsaturated fatty acids synthesis. Naturally occurring minor lipids--N-acyl phosphatidylethanolamine and its derivative N-acylethanolamine were detected in isolated rat heart under ischemia-reperfusion. It is notable that approximately 12% of total N-acylethanolamines were composed by anandamide. Treatment of N-acyl phosphatidylethanolamine by phospholipase D with subsequent fatty acyl chain analysis demonstrates that fatty acid composition of both N-acyl chains of N-acyl phosphatidylethanolamine and free N-acylethanolamine are similar and their main fatty acyl chains are 16:0, 18:0 and 20:4w6. It was shown that exogenous N-stearoyl-ethanolamine did not alter the levels of endogenous N-acyl phosphatidylethanolamine and N-acylethanolamine, but caused the decrease of lyso-phosphatidylcholine and phosphatidylglycerol levels. The rate of heart contractility and heart relaxation was found to increase during the early period of reperfusion. N-stearoyl-ethanolamine prevents this alteration and exerts a negative inotropic effect. It is concluded that membrane protective properties of N-stearoyl-ethanolamine at least partly depend on its ability to inhibit decrease amount of arachidonic and docosahexaenoic acids, to modulate the fatty acyl chains of cardiac phospholipids and to decrease the level of lyso-phosphatidylcholine.     

Essential fatty acid status of neonates born to Inuit mothers: comparison with Caucasian neonates and effect of diet.

Fatty acid compositions were determined of phospholipids isolated from venous cord plasma and from the walls of umbilical arteries and veins, collected from healthy, a terme, Inuit and Caucasian (Dutch) neonates. The Inuit fatty acid profiles were characterized by a lower essential fatty acid (EFA) status, with higher levels of monounsaturated fatty acids, of Mead acid [20:3(n-9)] and its direct elongation product, and with lower amounts of the longer chain (greater than or equal to 20 carbon atoms), highly unsaturated (greater than or equal to 4 double bonds) fatty acids of both the (n-3) and (n-6) families. Levels of linoleic- and dihomo-gamma-linolenic acids were higher in Inuit as compared to Caucasian neonates, which suggests a low activity of the delta-5-desaturase in the Inuit. Within the Inuit group, a higher intake of marine food was associated with a better neonatal (n-3) status. Although the differences between Inuit and Caucasian neonates may be of genetic rather than of dietary origin, the results imply that dietary long-chain (n-3) or (n-6) fatty acids may be particularly important during pregnancy in Inuit mothers. Further studies are indicated with respect to the EFA content of the habitual Inuit diet and levels of delta-5-desaturase activity in the Inuit.     

Ontogenic development of the fatty acyl chain composition of the turkey (Meleagris gallopavo) pectoralis superficialis muscle membranes: an allometric approach

The growth-associated development of the m. pectoralis superficialis (MPS) phospholipid (PL) and triacylglycerol (TAG) fatty acyl (FA) chain composition was determined in BUT8 meat-type turkeys. Samples (3 d, 8, 12, 16 and 20 wk) of each 6 males were analysed by lipid fractionation and subsequent gas chromatography. Results were interpreted on an allometric basis. The MPS mass increased linearly (MPS weight = 0.2787 BW- 123.67; R2 = 0.9935, P<0.001, n = 30). In the total phospholipids 62-63% unsaturated fatty acids were found irrespective of the diet. A negative allometric alteration was found for the total saturated acyl chains (B = -0.012), while a positive value for the calculated unsaturation index (B = 0.026) was obtained. Within the PUFA chains, the n3- n6 balance was markedly changed, on the favour of the n3 fatty acyl chains, namely competitive allometric trends were found for the total n3 (B = 0.087) and n6 (B = 0.032) fatty acid groups. The alterations of the TAG FA chain composition were diet-dependent. The serum creatine kinase activity increased by over one class of magnitude during the trial. The allometric approach was found to be powerful in the characterization of the basic, non diet-dependent ontogenic alterations of the phospholipid fatty acyl chain composition.     

Effects of lipids on the transport activity of the reconstituted glucose transport system from rat adipocyte

The glucose transport system, isolated from rat adipocyte membrane fractions, was reconstituted into phospholipid vesicles. Vesicles composed of crude egg yolk phospholipids, containing primarily phosphatidylcholine (PC) and phosphatidylethanolamine (PE), demonstrated specific d-glucose uptake. Purified vesicles made of PC and PE also supported such activity but PC or PE by themselves did not. The modulation of this uptake activity has been studied by systematically altering the lipid composition of the reconstituted system with respect to: (1) polar headgroups; (2) acyl chains, and (3) charge. Addition of small amounts (20 mol%) of PS, phosphatidylinositol (PI), cholesterol, or sphingomyelin significantly reduced glucose transport activity. A similar effect was seen with the charged lipid, phosphatidic acid. In the case of PS, this effect was independent of the acyl chain composition. Polar headgroup modification of PE, however, did not appreciably affect transport activity. Free fatty acids, on the other hand, increased or decreased activity based on the degree of saturation and charge. These results indicate that glucose transport activity is sensitive to specific alterations in both the polar headgroup and acyl chain composition of the surrounding membrane lipids.     

SYNAPTOSOMAL PLASMA MEMBRANES. ACYL GROUP COMPOSITION OF PHOSPHOGLYCERIDES and (Na++ K+)-ATPase ACTIVITY DURING FATTY ACID DEFICIENCY

Abstract— Essential fatty acid deficiency was induced in mice after feeding a fatty acid deficient diet for 6 months. Activity of the (Na⁺+ K⁺)-ATPase in the total brain homogenates and in isolated synaptosomal plasma membranes was significantly higher ( P & lt; 0 05) in the deficient mice than the controls. Analysis of the acyl group composition of phosphoglycerides in brain as well as in the synaptosomal plasma membranes showed that mice fed the deficient diet had increased levels of 20:3(n-9) and 22:3(n-9) and decreased levels of 20:4(n-6) and 22:4(n-6). However, acyl group changes varied among individual phosphoglycerides and were most obvious in the two species of ethanolamine phosphoglycerides. A decrease in 22:6(n-3) level was also observed in some phosphoglycerides of the synaptosomal plasma membranes especially the diacyl- sn -glycerophosphorylserine. In this experiment, a new solvent system for chromatographic separation of the diacyl- sn -glycerophosphorylserine and diacyl- sn -glycerophosphorylinositol was reported. The separation technique was suitable for analysis of acyl group composition of individual phosphoglycerides by gas-liquid chromatography. The results were consislent with a positive correlation of the non-polar acyl groups of brain membranes with the active ion transport activity. The increase in enzymic activity during deficient state may be the result of a biological adaptation due to structural alteration of the brain membranes.     

Fatty acid remodelling of phosphatidylinositol under conditions of de novo synthesis in rat liver microsomes

Phosphatidylinositol (PI) is initially synthesized in mammalian cells with a fatty acid composition similar to that of its precursor, primarily monounsaturated forms of cytidine diphosphodiglyceride (CDP-DAG). However, at the steady state, over 80% of PI exists in the 1-stearoyl, 2-arachidonoyl form. The fatty acid remodelling of PI is due to a number of deacylation/reacylation mechanisms. In the preceding paper we demonstrated that de novo synthesized PI is rapidly deacylated and subsequently reacylated. In this report we present further evidence that cycles of deacylation and reacylation are involved in the remodelling of PI. Incubation of microsomes with CDP-DAG of different fatty acid composition results in quantitative and qualitative differences in lysoPI formation. Additionally, analyses of the resulting lysoPI and PI species reveal that multiple species of fatty acids are incorporated into the 1-position of both PI and lysoPI. Addition of acylation cofactors (fatty acyl CoAs or ATP plus CoA) potentiate reacylation in this system. The addition of stearoyl or myristoyl CoA during de novo synthesis of PI results in the incorporation of these added fatty acids into the I-positive of PI. In addition, some evidence is presented that multiple mechanisms for remodelling of the 1-position of PI may be active in the microsomes, including ATP- and CoA-dependent acylation, ATP-independent, CoA-dependent acylation and CoA-independent mechanisms. Finally, the disappearance of only a subset of lysoPI species upon the addition of acylation cofactors suggests that the reacylation step exhibits some substrate specificity.     

Abdominal adiposity is associated with fatty acid desaturase activity in boys: Implications for C-reactive protein and insulin resistance

Fatty acid composition, which is altered in patients with abdominal obesity, is influenced not only by dietary intake but also by the desaturating enzymes stearoyl-CoA desaturase (SCD), delta-6 desaturase (D6D) and delta-5 desaturase (D5D). We investigated desaturase activities and their associations with metabolic risk factors, C-reactive protein levels (CRP) and insulin resistance in Japanese children. There were 237 school children in this study; 115 were boys. The fatty acid composition of plasma phospholipids was analyzed, and the following desaturase activities were estimated: SCD (16:1n-7/16:0 and 18:1n-9/18:0), D6D (20:3n-6/18:2n-6) and D5D (20:4n-6/20:3n-6). D6D and D5D activities, but not SCD activity, were significantly associated with triglyceride levels, high-density lipoprotein cholesterol levels and insulin resistance in both sexes, and with CRP levels in boys. In addition, increased abdominal adiposity was significantly associated with increased D6D activity, and decreased D5D activity and insulin resistance in both sexes, and with increased CRP levels in boys. The n-6 polyunsaturated fatty acid desaturation pathway may be associated with metabolic risk factors, insulin resistance and increased inflammation in children with abdominal obesity, especially in boys.     

Dietary protein and fatty acid composition of liver lipids in the rat

In order to compare the effects of different sources of dietary protein on the fatty acid composition of phosphatidylcholines (PC), phosphatidylethanolamines (PE), phosphatidylinositols (PI), cholesteryl esters and triacylglycerols, male rats were fed for a 4-week period on cholesterol-free, or cholesterol-containing, diets based on casein, or soybean protein and olive oil. The most conspicuous difference observed was the occurrence of significantly higher levels of 5,8,11-eicosatrienoic acid, 20:3 (n - 9), in the different lipid classes of casein-fed, compared with soybean protein-fed, animals. In the PI fraction of livers from the groups of rats fed casein diet, this fatty acid amounted to between 9.9 and 13.3% by weight of the total fatty acids. Phospholipids from livers of casein-fed rats contained increased levels of oleic acid, 18:1 (n - 9) (in PC and PE) and reduced levels of stearic acid (18:0). Moreover, in this group of rats PI contained a reduced level of arachidonic acid, 20:4 (n - 6). A casein-related decrease in the linoleic acid, 18:2 (n - 6), content of PC and PE was observed only in the rats fed on cholesterol-free diet. Effects on the fatty acid composition were also observed in the triacyglycerol and cholesteryl ester fractions, in which the rats fed casein diet showed higher levels of palmitoleic acid, 16:1 (n - 7) (cholesterol-supplemented diet) and lower values for linoleic acid, than the soybean protein-fed rats.     

Synthesis and polymorphic phase behaviour of polyunsaturated phosphatidylcholines and phosphatidylethanolamines

A series of phosphatidylcholines and phosphatidylethanolamines was synthesized containing two acyl chains of the following polyunsaturated fatty acids: linoleic acid (18:2), linolenic acid (18:3), arachidonic acid (20:4) and docosahexaenoic acid (22:6). In addition two phospholipids with mixed acid composition were synthesized: 16:0/18:1_c phosphatidylcholine and 16:0/18:1_c phosphatidylethanolamine. The structural properties of these lipids in aqueous dispersions in the absence and in the presence of equimolar cholesterol were studied using ³¹P-NMR, freeze fracturing and differential scanning calorimetry (DSC).The phosphatidylcholines adopt a bilayer configuration above 0°C. Incorporation of 50 mol% of cholesterol in polyunsaturated species induces a transition at elevated temperatures into structures with ³¹P-NMR characteristics typical of non-bilayer organizations. When the acyl chains contain three or more double bonds, this non-bilayer organization is most likely the hexagonal H_II phase, 16:0/15:1_c phosphatidylethanolamine shows a bilayer to hexagonal transition temperature of 75°C. The polyunsaturated phosphatidylethanolamines exhibit a bilayer to hexagonal transition temperature below 0°C which decreases with increasing unsaturation and which is lowered by approximately 10°C upon incorporation of 50 mol% of cholesterol. Finally, it was found that small amounts of polyunsaturated fatty acyl chains in a phosphatidylethanolamine disproportionally lower its bilayer to hexagonal transition temperature.     

Phosphatidylcholine fluidity and structure affect lecithin:cholesterol acyltransferase activity

The purpose of this study was to test the hypothesis that lipid fluidity regulates lecithin:cholesterol acyltransferase (LCAT) activity. Phosphatidylcholine (PC) species were synthesized that varied in fluidity by changing the number, type (cis vs. trans), or position of the double bonds in 18 or 20 carbon sn-2 fatty acyl chains and recombined with [(3)H]cholesterol and apolipoprotein A-I to form recombinant high density lipoprotein (rHDL) substrate particles. The activity of purified human plasma LCAT decreased with PC sn-2 fatty acyl chains containing trans versus cis double bonds and as double bonds were moved towards the methyl terminus of the sn-2 fatty acyl chain. The decrease in LCAT activity was significantly correlated with a decrease in rHDL fluidity (measured by diphenylhexatriene fluorescence polarization) for PC species containing 18 carbon (r(2) = 0.61, n = 18) and 20 carbon (r(2) = 0.93, n = 5) sn-2 fatty acyl chains. rHDL were also made containing 10% of the 18 carbon sn-2 fatty acyl chain PC species and 90% of an inert PC ether matrix (sn-1 18:1, sn-2 16:0 PC ether) to normalize rHDL fluidity. Even though fluidity was similar among the PC ether-containing rHDL, the order of PC reactivity with LCAT was significantly correlated (r(2) = 0.71) with that of 100% PC rHDL containing the same 18 carbon sn-2 fatty acyl chain species, suggesting that PC structure in the active site of LCAT determines reactivity in the absence of measurable differences in bilayer fluidity. We conclude that PC fluidity and structure are major regulators of LCAT activity when fatty acyl chain length is constant.     

Role of collagen tripeptide fragment GER on activation of adhesion and modification of fatty acid composition in membrane phospholipids of CHO-K1 cells

It has been found that the multiply repeated tripeptide fragment GER (Gly-Glu-Arg) from different collagen types stimulates the nonspecific adhesion of CHO-K1 cells. Activation of cell adhesion is accompanied by modifications to the fatty acid composition in the phospholipids of the cell membrane. Cell incubation with the synthetic GER peptide increases the unsaturation index of phosphatidylcholin (PC), phosphatidylethanolamine (PEA), and phosphatidylinositol (PI). Arachidonic (C20:4ω6) acid is mainly contributed to the increased index of PI. Not only arachidonic acid but other unsaturated fatty acids, such as docosatetraenoic (C22:4ω6), docosapentaenoic (C22:5ω3), and docosahexaenoic (C22:6ω3), are responsible for the increased index of PC and PEA. In addition, the elevation of the relative content of polyenoic fatty acids in PI is concomitant with a reduced amount of monoenoic fatty acids, mainly due to decline in the oleic (C18:1) acid level. The role of GER peptide in (1) the activation of cell adhesion as a regulator of active or inactive states of integrin receptors; (2) modification of fatty acid composition in major classes of phospholipids as a modulator of the fluidity in annular lipid zones surrounding to the adhesive molecules is discussed.