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PubMed1967

Properties, composition, and structure of stearic acid-stearate monolayers on alkaline earth solutions.

Interactions between alkaline earth ions and the carboxylate ligand in a stearic acid surface film have been investigated by IR spectrophotometry and surface chemical procedures. The frequency and shape of the carboxylate absorption band and the effect of hydration and pH on band characteristics suggest that beryllium, magnesium, and calcium ions form calcium-type complexes with the stearate ligand while strontium and barium ions form both calcium-type complexes and more ionic barium-type complexes, which have lower carboxylate band maxima. Since IR band frequencies in anhydrous calcium-type complexes are directly proportional to the charge/(crystal radius) ratio, it is apparent that covalency decreases in the order: Be > Mg > Ca > Sr > Ba. The decreasing order of stability constants estimated from spectrophotometric titration data, Be > Ca > Mg > Sr > Ba, demonstrates that calcium behaves anomalously. This anomalous behavior is also apparent in the high solid-to-liquid phase transition temperature and small surface area of the calcium-carboxylate film compared to films composed of complexes with the other ions. A geometric factor related to the ionic radius and the radius of the carboxylate binding site formed by a calcium stearate lattice is proposed to explain the unique properties of calcium-carboxylate surface films. Although the beryllium complex has the highest carboxylate band frequency and stability constant, it gives an atypical "expanded" surface film. A hydrogen bonded lattice formed with a soluble beryllium monohydrate is suggested as an explanation for this film property.

Barium↗
PubMed1989

Effect of phospholipase A2 and free fatty acids on lipid-protein interactions in long- and very-long-chain fatty acyl-CoA elongation enzyme systems of brain microsomes.

The elucidation of the mechanism of phospholipase A2-induced inactivation of the condensation enzyme provided evidence concerning the important role of lipid-enzyme interactions in maintaining the condensation activity in swine cerebral microsomes. A quantitative analysis of fatty acid release by phospholipase A2 from the microsomal membrane revealed that only 5 nmol of free fatty acid per mg microsomal protein was released, including oleic acid and arachidonic acid, by treatment with 0.4 unit of phospholipase A2 per mg microsomal protein for 15 s at 23 degrees C. Under these conditions, the condensation activity for endogenous 16:0-CoA and 20:4-CoA decreased to half and that for exogenous 20:0-CoA decreased to 75%. However, the addition of free fatty acids and lysophospholipids or a mixture of them at 5-10 nmol/mg protein did not change the condensation activity for endogenous 16:0-CoA and 20:4-CoA, or for exogenous 20:0-CoA. These results indicated that phospholipase A2 inhibited the condensation activity by acting directly on phospholipids that are indispensable to maintaining the function of the condensation enzyme. The Arrhenius plot for the condensation of endogenous 16:0-CoA showed a break at around 16 degrees C, whereas no break of the plot was observed for the condensation of 20:0-CoA and 20:4-CoA. The activation energy for the condensation of 16:0-CoA and 20:4-CoA was decreased by the addition of free fatty acids such as oleic acid and stearic acid, with disappearance of the Arrhenius break for 16:0-CoA condensation, whereas the activation energy for the condensation of 20:0-CoA was not changed. These results suggest that the type of lipid-protein interaction in the condensation enzyme for 20:0-CoA is different from that for 16:0-CoA and 20:4-CoA.

3-Oxoacyl-(Acyl-Carrier-Protein) Synthase↗
PubMed1976

[Thrombogenic and atherogenic effects of dietary fats].

1. Epidemiologic studies have shown that CHD (arterial thrombosis) and venous thrombosis were closely associated with dietary saturated fat intake. 2. In vitro and in vivo studies are unanimous in that long chain saturated fatty acids, mostly-stearic acid, are thrombogenic, while linoleic acid has protective effects. 3. Stearic acid appears to modify the fatty acid composition of platelet phospholipids resulting in an increase in the aggregating and clotting capacities of platelets. 4. In coronary patients or in subjects eating saturated fats, similar modifications in platelet behaviour can be observed related to changes in platelet phospholipids. Those results appear to confirm the hypothesis that certain dietary saturated fats, in addition to induce hyperlipemia and atherosclerosis, predispose to thrombosis mostly through blood platelets.

Adult↗
PubMed1996

Release of individual fatty acids from human adipose tissue in vivo after an overnight fast.

The objective of this study was to investigate the mobilization of individual fatty acids from human subcutaneous adipose tissue in vivo. Concentrations of individual non-esterified fatty acids were measured in arterialized plasma and in the venous drainage from subcutaneous abdominal adipose tissue in eight normal subjects, after an overnight fast, and for the subsequent 6 h. Whilst the veno-arterial concentration difference for non-esterified fatty acids increased over this period, the relative proportions of different fatty acids remained constant. There was a close relationship between veno-arterial difference and arterialized concentration for the different fatty acids. The arterialized concentration of stearic acid consistently lay above the regression line drawn for unsaturated fatty acids (P = 0.001), probably reflecting lower clearance of stearic acid. The release of individual fatty acids was compared with their prevalence in adipose tissue triacylglycerol in biopsies taken from six subjects. Relative release decreased with increasing chain length, and for a given chain length increased with increasing unsaturation, in agreement with animal studies (P < 0.001 for differences in relative mobilization according to these two factors). The results suggest that the systemic plasma concentration of individual non-esterified fatty acids is determined by their release from adipose tissue, but that the relationship between release and systemic concentration for stearic acid is different from that for other fatty acids. The results confirm, in humans, differences in relative mobilization found previously in animal studies.

Adipose Tissue↗
PubMed2002

[Study on the photofluorescence of Eu(III) and long chain fatty acid complexes].

The complexes having the compositions of Eu(L1)(3)2H2O,Eu(L1)3phen,Eu(L2)(3)2H2O,Eu(L2)3phen (phen = 1,10-phenathroline,L1 = Dodecanoic acid, L2 = Stearic acid) were synthesized and characterized by elemental analysis and FTIR spectra. Their fluorescence spectra, UV spectra and TEM (Transmission Electron Microscope) have been investigated. The results show that the 5D0-7F1 and 5D0-7F2 transition of Eu(III) are observed in the emission spectrum of the particles at room temperature. As good photoluminescent materials, they may be useful in the regions of EL (Electroluminescence) or macromolecule composite materials doped with rare earth.

Chelating Agents↗
PubMed2003

[Structure identification of jujuboside E].

AIM: To study the chemical constituents of the seeds of Ziziphus jujuba Mill var. spinosa (Bunge) Hu ex. H.F. Chou. METHODS: To separate the constituents by using various kinds of chromatography methods and identify their structures on the basis of spectral analysis. RESULTS: Seven compounds were isolated. Their structures were established as jujuboside E (1), jujuboside B (2), jujuboside A (3), betulic acid (4), stearic acid (5), sucrose (6) and inosine (7). CONCLUSION: Compound 1 is a new compound named jujuboside E. Compounds 5, 6, 7 were isolated for the first time from this plant.

Inosine↗
PubMed2002

Uptake of long-chain fatty acids in HepG2 cells involves caveolae: analysis of a novel pathway.

We investigated the role of caveolae in uptake and intracellular trafficking of long chain fatty acids (LCFA) in HepG2 human hepatoma cells. The uptake of [(3)H]oleic acid and [(3)H]stearic acid into HepG2 cells was measured by radioactive assays and internalization of the non-metabolizable fluorescent fatty acid 12-(N-methyl)-N-[(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino] (12-NBD) stearate into single HepG2 cells was semi-quantitatively assessed by laser scanning microscopy. The initial rate of [(3)H]oleic acid uptake (V(0)) in HepG2 cells exhibited saturable transport kinetics with increasing concentrations of free oleic acid (V(max) 854 +/- 46 pmol mg protein(-1) min(-1), K(m) 100 +/- 14 nmol/l). While inhibition of clathrin coated pits did not influence LCFA uptake in HepG2, inhibition of caveolae formation by filipin III, cyclodextrin, and caveolin-1 antisense oligonucleotides resulted in reduction of [(3)H]oleic acid uptake by 54%, 45%, and 23%, respectively. Furthermore, filipin III inhibited the uptake of [(3)H]stearic acid and its fluorescent derivative 12-NBD stearate by 44% and 50%, respectively. Transfection studies with alpha-caveolin-1/cyanofluorescent protein chimeras showed significant colocalization of caveolae and internalized 12-NBD stearate. In conclusion, these data suggest a significant role for caveolae mediated uptake and intracellular trafficking of LCFA in HepG2 cells.

Biological Transport↗
PubMed1999

Biophysical perturbations induced by ethylazinphos in lipid membranes.

Perturbations induced by ethylazinphos on the physical organization of dipalmitoylphosphatidylcholine (DPPC) and DPPC/cholesterol membranes were studied by differential scanning calorimetry (DSC) and fluorescence polarization of 2-, 6-, 12-(9-anthroyloxy) stearic acids and 16-(9-anthroyloxy) palmitic acid. Ethylazinphos (50 and 100 microM) increases the fluorescence polarization of the probes, either in the gel or in the fluid phase of DPPC bilayers, and this concentration dependent effect decreases from the surface to the bilayer core. Additionally, the insecticide displaces the phase transition to a lower temperature range and broadens the transition profile of DPPC. A shifting and broadening of the phase transition is also observed by DSC. Furthermore at insecticide/lipid molar ratios higher than 1/7, DSC thermograms, in addition to the normal transition centered at 41 degrees C, also display a new phase transition centered at 45.5 degrees C. The enthalpy of this new transition increases with insecticide concentration, with a corresponding decrease of the main transition enthalpy. Ethylazinphos in DPPC bilayers with low cholesterol (< or = 20 mol%) perturbs the membrane organization as described above for pure DPPC. However, cholesterol concentrations higher than 20 mol% prevent insecticide interaction, as revealed by fluorescence polarization and DSC data. Apparently, cholesterol significantly modulates insecticide interaction by competition for similar distribution domains in the membrane. The present results strongly support our previous hypothesis that ethylazinphos locates in the cooperativity region, i.e. the region of C1-C9 atoms of the acyl chains, and extends to the lipid-water interface, where it increases lipid packing order sensed across all the thickness of the bilayer. Additionally, and, on the basis of DSC data, a lateral regionalization of ethylazinphos is here tentatively suggested.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2003

Synthesis and analysis of symmetrical and nonsymmetrical disaturated/monounsaturated triacylglycerols.

Symmetrical disaturated triacylglycerols of the structure SUS, where S is stearic acid (18:0) and U is an unsaturated fatty acid, either oleic (O; 9cis-18:1), linoleic (L; 9cis,12cis-18:2), or linolenic (Ln; 9cis,12cis,15cis-18:3), are important components providing functionality to interesterified fat blends and structurally modified oils. Nonsymmetrical triacylglycerols of the structure SSU can significantly change melting point and solid fat content profiles. To characterize the physical properties of pure and symmetrical and nonsymmetrical triacylglycerol mixtures, the same reaction sequence has been used to prepare multigram quantities of triacylglycerols SUS and SSU. Tristearin was converted to a mixture of mono-, di-, and triacylglycerols, and the 1,3- and 1,2-diacylglycerol fraction was isolated by silica column chromatography. The 1,3-diacylglycerols were removed by crystallization from acetone and esterified with the appropriate fatty acid to form the symmetrical triacylglycerols with >99% SUS structure. The more difficult to obtain 1,2-diacylglycerols were prepared by esterification of the enriched 1,2-diacylglycerol fraction (80-86% 1,2-diacylglycerols) remaining after removal of much of the 1,3-isomer by crystallization, but silver resin or silver nitrate impregnated silica gel chromatography was required to isolate the nonsymmetrical triacylglycerols. SSL and SSLn were prepared in purities of >98% by this procedure, but not SSO. Silver ion HPLC was found to be as accurate as, and more rapid than, lipolysis/gas chromatography for the determination of the isomeric purities of the synthesized triacylglycerols.

Acetone↗
PubMed2006

Sum-frequency spectroscopy analysis of two-component langmuir monolayers and the associated interfacial water structure.

Sum-frequency spectroscopy (SFS) in the CH and OH stretching regions was employed to obtain structural information about Langmuir monolayers on the H(2)O subphase of the model lipid dioctadecyldimethylammonium bromide (DOMA) and of the neutral surfactant methyl stearate (SME) and their mixtures and about the interfacial water structure underneath the films. These results were compared with the sum-frequency spectra of the interface between Langmuir monolayers of stearic acid and stearic acid-DOMA monolayers and water to prove that the uncompensated headgroup charge of DOMA at the interface is the reason for structuring of interfacial water close to the studied monomolecular films. Sum-frequency spectra on D(2)O subphase were also studied to account for the interference between the CH and OH spectral signatures because of the coherent nature of the SFS signals. Interfacial water structure proved to be a determining factor in the behavior of the mixed lipid monolayers. A mixing induced amplification in the surface potential DeltaV observed in our previous work was explained with total increase of the dipole moment for the mixed films, bigger than the arithmetic average for DOMA and SME monolayers alone. The increase is due to the better packing of the molecules in the mixed films and to the decrease in the interfacial water dipole moment arising from a more disordered water structure underneath the mixed monolayers.

Membranes, Artificial↗
PubMed2001

Calcium supplementation of chocolate: effect on cocoa butter digestibility and blood lipids in humans.

BACKGROUND: The digestibility of cocoa butter was reported in animal but not human studies to be low (60-70% and 89-94%, respectively). These differences could be due to the much higher ratio of calcium to fat (by wt) in the diet of rats (0.04-0.18) than in that of humans (0.01). OBJECTIVE: We investigated whether supplementation of chocolate with 0.9% calcium (by wt), as an integral part of a Western diet, reduces absorption of cocoa butter and hence the digestible energy value of chocolate. We also assessed the effect of calcium supplementation on the blood lipid profile. DESIGN: Ten men were fed control diets containing 98-101 g chocolate/d with or without a 0.9%-Ca supplement (0.9 g Ca/d) for 2 periods of 2 wk each. The study was conducted with use of a randomized, double-blind crossover design under free-living conditions but with strict control of food intake. RESULTS: Calcium supplementation of chocolate increased fecal fat 2-fold (from 4.4 to 8.4 g/d; P < 0.0001) and reduced the absorption of cocoa butter by 13.0%. This was due mainly to an increase in the excretion of palmitic and stearic acids (3.4 g/d), which reduced the absorbable energy value of the chocolate by approximately 9%. This supplementation also reduced plasma LDL cholesterol by 15% (P < 0.02); HDL cholesterol was unchanged. CONCLUSIONS: Calcium supplementation can be used as a means of reducing the absorbable energy value of chocolate. Supplementation with 2.25% CaCO3 had no effect on the taste of chocolate, was well tolerated by the subjects, and reduced LDL cholesterol in a short-term study.

Adult↗
PubMed1995

Differential effects of interferon-gamma and -beta on fatty acid turnover, lipid bilayer fluidity and TNF-alpha release in murine macrophage J774.2 cells.

The effects of interferon (IFN)-gamma and IFN-beta on the incorporation of 14C-linoleic acid into J774.2 cell membrane phospholipids were examined. Interferon-gamma induced a statistically significant increase in incorporation of 14C-linoleic acid into all the major phospholipid classes. In contrast, IFN-beta induced a slightly reduced incorporation of this fatty acid into the phospholipids. Neither IFN-gamma nor IFN-beta had any effect on the incorporation of the saturated fatty acid 14C-stearic acid into the cellular phospholipids. Interferon-gamma had no effect on the metabolism of 14C-linoleic acid in the fibroblast cell line L929. Macrophage membrane fluidity was assessed by spin-label ESR spectroscopy after incubation with either IFN-gamma or IFN-beta. Interferon-gamma significantly increased membrane fluidity whereas IFN-beta significantly decreased the fluidity. The findings of this study reveal that IFN-gamma might act on the enzymes controlling the labelling of the sn2 position of phospholipids (linoleic acid) but not the sn1 position (stearic acid), and this increases the polyunsaturated fatty acid content of macrophage membranes. This increase in polyunsaturation is reflected in the increased membrane fluidity. We also conclude that IFN-beta and IFN-gamma have different mechanisms of action on macrophage membrane lipid metabolism.

Animals↗
PubMed1965

LIVER LIPIDS OF CHOLINE-DEFICIENT RATS.

1. Four-week-old male and female rats were given choline-deficient diets for 2 weeks. Deficient animals gained nearly as much weight as normal controls of the same sex. 2. The amounts of triglyceride and esterified cholesterol in liver lipids were increased threefold or more by the deficiency. The amounts of the major phosphatides and of unesterified cholesterol were unaffected. 3. In males, deficiency significantly increased the proportion of stearic acid in triglycerides, and, in females, the proportion of arachidonic acid was significantly decreased. 4. In the phospholipids of male rats, choline deficiency produced decreases in the amounts of linoleic acid and arachidonic acid and increased the amount of stearic acid. In the phospholipids of female rats, choline deficiency decreased the amount of arachidonic acid and increased that of linoleic acid. 5. The liver phospholipids of normal male rats had higher proportions of palmitic acid and lower proportions of stearic acid than were found in normal females. These sex differences became statistically insignificant in deficient animals.

Animals↗
PubMed2006

Phase behaviour of stearic acid-stearonitrile mixtures. A thermodynamic study in bulk and at the air-water interface.

The solid-liquid phase behaviour of stearic acid (SA) and stearonitrile (SN) in binary mixtures was investigated by differential scanning calorimetry (DSC), and the formation of SA-SN mixed monolayers at the air-water interface was followed by surface pressure-area (pi-A) measurements and by Brewster angle microscope (BAM) observation. The solid-liquid phase diagram is a eutectic type phase diagram, with the eutectic composition 0.90<X(SN)<0.95 and T(eut)=40.9 degrees C. The DSC results also suggest that the two components are immiscible in the solid phase but form a liquid mixture with positive deviations to the ideal behaviour. At the air-water interface, the two components form liquid condensed monolayers in the entire range of compositions, at low surface pressures, while solid mixed monolayers only form at high surface pressures for X(SN)<0.8. Thermodynamic analysis indicates that SA and SN are miscible in the liquid condensed phase, with negative deviations from the ideal behaviour. The variation of the collapse surface pressure of mixed monolayers also indicates miscibility at the air-water interface.

Air↗
PubMed1982

Propionyl-Coa induced synthesis of even-chain-length fatty acids by fatty acid synthetase from Brevibacterium ammoniagenes.

The product distribution of Brevibacterium ammoniagenes fatty acid synthetase has been investigated using propionyl-CoA instead of acetyl-CoA as the primer. The synthetase produces not only an odd-numbered fatty acid (heptadecanoic acid) but also even-numbered fatty acids (stearic and oleic acids) in the presence of propionyl-CoA. The amounts of heptadecanoic, stearic and oleic acids increased with increasing concentration of propionyl-CoA. However, the formation of heptadecenoic acid (C17:1) was not observed under any conditions tested. The failure of C17:1 synthesis suggested that the enzyme component catalyzing the beta, gamma-dehydration, which is responsible for the synthesis of unsaturated fatty acids, has a high degree of chain length specificity. Under standard assay conditions, stearic acid predominated and heptadecanoic and oleic acids were found in lesser amounts. Mass spectrometric analyses of fatty acids synthesized either from [2H]propionyl-CoA or in 2H2O revealed that propionyl-CoA is utilized as the priming substrate for the synthesis of heptadecanoic acid and that an acetyl residues, which is formed by the decarboxylation of malonyl-CoA, served as the priming substrate for the syntheses of stearic and oleic acids. No evidence was obtained for the direct decarboxylation of malonyl-CoA to acetyl-CoA in this reaction. It is concluded that the decarboxylation of the malonyl moiety bound to the synthetase occurs efficiently only in the course of fatty acid synthesis. A hypothetical scheme is presented to explain the propionyl-CoA-dependent decarboxylation of the malonyl moiety.

Acetyl Coenzyme A↗
PubMed2003

Chemical and enzymatic transacylation of amide-linked FA of buttermilk gangliosides.

The goal of this work was to alter the composition of amide-linked FA of bovine buttermilk gangliosides, particularly the disialoganglioside GD3, to adjust lipid sources to special food specifications and pharmacological or cosmetic applications. The chemical transacylation of amide-linked FA of buttermilk gangliosides with free arachidic acid (20:0) by a combination of basic hydrolysis and diethylphosphorylcyanide/triethylamine-catalyzed reacylation was compared to an enzymatic sphingolipid ceramide N-deacylase (EC 3.5.1.23)-catalyzed FA exchange by GC analysis and nano electrospray ionization-MS. The buttermilk predominantly contained the disialoganglioside GD3 and the monosialoganglioside GM3. The heterogeneity of FA that are incorporated into gangliosides, mainly palmitic acid (29.4 wt%), stearic acid (16.9 wt%), oleic acid (17.8 wt%), and myristic acid (8.5 wt%), was effectively altered by both transesterification techniques. Arachidic acid, which was not integrated into the initial buttermilk gangliosides, was transacylated to total gangliosides with 23.2 wt% (GD3, 6.7 wt%) by the chemical process and with 8.7 wt% (GD3, 13.8 wt%) when catalyzed enzymatically. Mainly behenic acid and lignoceric acid of GD3 were exchanged chemically, and stearic acid was exchanged by the enzymatic process. This observation might depend on hydrolytic sensitivities of amide-linked very long chain saturated FA or specific enzyme subtrate affinities, respectively. Results of chemical hydrolysis indicated there was a risk of sialic acid decomposition and unspecific degradations. Regarding specificity and avoidance of critical agents, the enzymatic transesterification is recommended for industrial-scale production of consumer goods.

Acylation↗
PubMed1993

The role of fatty acid saturation on plasma lipids, lipoproteins, and apolipoproteins: II. The plasma total and low-density lipoprotein cholesterol response of individual fatty acids.

Regression analyses were performed on individual data from our two previous clinical investigations to establish the cholesterolemic effects of individual fatty acids. Our principal objective was to determine the effects of stearic acid on plasma total cholesterol (TC) and low-density lipoprotein (LDL) cholesterol levels. Our second objective was to determine the variation in the cholesterolemic response of individuals to changes (delta) in the major dietary fatty acids. The best-fitting linear regression equations relating delta TC and delta LDL (mg/dL) were as follows: delta TC = 2.3 delta C14:0 + 3.0 delta C16:0 - 0.8 delta C18:0 - 1.0 delta polyunsaturated fatty acids (PUFA) and delta LDL = 2.6 delta C14:0 + 2.9 delta C16:0 - 0.5 delta C18:0 - 0.7 delta PUFA, where delta fatty acid = change in intake expressed as percent of calories. Based on these equations, in which stearic acid has a significant, negative regression coefficient, and the other regression models analyzed, it appears that stearic acid has an independent cholesterol-lowering effect. Using the equation we developed, 75% of the actual cholesterolemic responses were within +/- 10 mg/dL of the predicted response. In summary, we have developed a predictive equation (similar to those developed by both Keys and Hegsted) to estimate changes in plasma TC and LDL cholesterol levels of young men in response to changes in dietary fatty acids. However, our predictive equation separates stearic acid from the other long-chain saturated fatty acids (SFA) and indicates that it has an independent cholesterol-lowering effect. Thus, stearic acid is a unique long-chain SFA because of its effect on plasma cholesterol level.

Apolipoproteins↗
PubMed1965

Incorporation of 14C-labelled fatty acids into the mammary-gland lipids of the lactating rabbit.

1. [1-(14)C]Stearic acid, [9-(14)C]stearic acid, [9-(14)C]palmitic acid and [9-(14)C]decanoic acid were fed to lactating rabbits, and the fatty acids of the mammary gland were separated and partially degraded. 2. Most of the (14)C recovered was located in the acids fed. Stearic acid was least efficiently absorbed; decanoic acid was the most extensively metabolized. 3. Resynthesis after degradation to C(2) units led to uniform alternate labelling in the C(2)-C(10) acids, whereas C(12)-C(18) acids had excess of (14)C at the carboxyl end. 4. Acids formed by beta-oxidation down to C(12), but not below, were also present in the mammary-gland lipids. Desaturation of the administered acids was a very minor reaction.

Animals↗