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PubMed2003

Stearic acid absorption and its metabolizable energy value are minimally lower than those of other fatty acids in healthy men fed mixed diets.

Compared with other saturated fatty acids, stearic acid appears to have different metabolic effects with respect to its impact on risk for cardiovascular disease. These differences may in part reflect biologically important differences in absorption. This study was designed to compare the absorption and the metabolizable energy value of stearic acid with other fatty acids from mixed diets fed to healthy humans. Healthy men (n = 11) were fed four diets with multiple fat sources that contained approximately 15% of energy (en%) from protein, 46 en% from carbohydrate and 39 en% from fat with 8 en% substitution across diets of the following: trans monoenes, oleic acid, saturated fatty acids (lauric + myristic + palmitic) or stearic acid fed as triacylglycerides. Fats were incorporated into mixed diets comprised of foods typically consumed in the United States. After a 14-d adaptation period, volunteers collected all feces for 7 d. Across diets, absorption of stearic acid (94.1 +/- 0.2%) was lower (P < 0.0002) than that of palmitic acid (97.3 +/- 0.2%) and higher than generally reported. Absorption of lauric, myristic, oleic, linoleic and trans 18:1 monoenes did not differ from each other (>99%) but was higher than that of stearic and palmitic acids (P < 0.001). Metabolizable energy values were similar for all fatty acids. Although absorption of palmitic and stearic acids was affected by diet treatment, the magnitudes of the differences were small and do not appear to be biologically important, at least in terms of lipoprotein metabolism. On the basis of these results, reduced stearic acid absorption does not appear to be responsible for the differences in plasma lipoprotein responses to stearic acid relative to other saturated or unsaturated fatty acids.

Absorption↗
PubMed1997

Palmitic acid but not stearic acid inhibits NO-production in endothelial cells.

Several studies showed a diminished production of the endothelium-derived relaxing factor nitric oxide (NO) in the early stage of atherosclerosis. The inhibition of NO-production seems to be mediated by lipoproteins, especially oxidized low-density lipoproteins (ox-LDL). There is some evidence, that the interactions of lipoproteins and NO are associated with the phospholipid fraction of lipoproteins. Since fatty acids have different atherogenic properties-depending on chain length, degree of saturation and steric configuration-, we investigated the effect of fatty acids on endothelial NO-production. Human umbilical vein endothelial cells were incubated with palmitic acid and stearic acid in different concentrations in culture medium enriched with serum albumin for five hours. After that, NO-production was stimulated by calcium-ionophore A23187. NO-production was determined by a bioassay method using RFL-6 cells followed by radioimmunological determination of cGMP. NO-production stimulated by calcium-ionophore A23187(100%) was decreased by palmitic acid (10, 50, 100 microM) to 79 +/- 12%; 63 +/- 10% and 53 +/- 14%. In contrast, incubation with stearic acid (10, 50 and 100 microM) had no effect on A23187-stimulated NO-production (94 +/- 11%; 93 +/- 11%; 104 +/- 15%). Thus, palmitic acid but not stearic acid dose-dependently inhibited NO-release by endothelial cells. These different actions parallel the differing atherogenic potential of the two fatty acids.

Calcimycin↗
PubMed1992

Metabolic effects of dietary stearic acid in mice: changes in the fatty acid composition of triglycerides and phospholipids in various tissues.

The fatty acid patterns of triglycerides and phospholipids extracted from adipose tissue, liver, heart, kidney, spleen, and lung of 3 groups of C57BL/6 mice were determined after feeding diets rich in palmitic acid (16:0) (high palmitic: 16:0 = 45.1% of total fatty acids), stearic acid (18:0) (high stearic: 18:0 = 42.9% of total fatty acids) and oleic acid (18:1) (high oleic: 18:1 = 79.7% of total fatty acids) for 9 months. Triglyceride content of adipose, liver, heart, kidney, lung and spleen tissues was significantly enriched in palmitic acid in mice fed the high palmitic diet (range among all tissues: 19.9% +/- 0.2% to 29.0% +/- 1.9% of total fatty acids) and in oleic acid in mice fed the high oleic diet (range 56.0% +/- 1.9% to 71.6% +/- 1.2%). The stearic acid content of organ triglycerides in mice fed the high stearic diet ranged from 3.7% +/- 0.3% to 10.8% +/- 1.2%; however, the content of oleic acid on this diet (range: 57.0% +/- 1.8% to 71.4% +/- 1.7%) was similar to the one observed in mice fed the high oleic diet. In all organs, phospholipids had a significantly higher percentage of stearic acid (range: 23.5% +/- 0.9% to 51.5% +/- 6.6%) than triglycerides, regardless of diet. To evaluate the production of oleate from stearate and palmitate, 2 groups of mice were fed the high palmitic and the high stearic diets for 1 week and then injected intravenously with [1-14C]palmitate and [1-14C]stearate and the amount of labelled oleate in liver triglycerides was measured.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed2003

MpFAE3, a beta-ketoacyl-CoA synthase gene in the liverwort Marchantia polymorpha L., is preferentially involved in elongation of palmitic acid to stearic acid.

Fatty acid chain elongation is a crucial step in the biosynthesis of long chain fatty acids. An essential reaction in the elongation process is condensation of malonyl-CoA with acyl-CoA, which is catalyzed by beta-ketoacyl-CoA synthase (KCS) in plants. We have isolated and characterized the MpFAE3 gene, one of the KCS gene family in the liverwort Marchantia polymorpha. Transgenic M. polymorpha plants overexpressing MpFAE3 accumulate fatty acids 18:0, 20:0, and 22:0. In these plants, the amount of 16:0 is reduced to 50% of wild type. In a heterologous assay, transgenic methylotrophic yeast expressing the MpFAE3 gene accumulates fatty acid 18:0 and generates several longer fatty acids which are not detectable in the control, accompanied by a decrease of 16:0. These observations indicate that the MpFAE3 protein is preferentially involved in the elongation of 16:0 to 18:0 and also in the subsequent steps of 18:0 to 20:0 and 20:0 to 22:0 in M. polymorpha.

3-Oxoacyl-(Acyl-Carrier-Protein) Synthase↗
PubMed2000

Dietary docosahexaenoic acid affects stearic acid desaturation in spontaneously hypertensive rats.

Docosahexaenoic acid (DHA, 22:6n-3) is an n-3 polyunsaturated fatty acid which attenuates the development of hypertension in spontaneously hypertensive rats (SHR). The effects of DHA on delta-9-desaturase activity in hepatic microsomes and fatty acid composition were examined in young SHR. Two groups of SHR were fed either a DHA-enriched diet or a control diet for 6 wk. Desaturase activity and fatty acid composition were determined in hepatic microsomes following the dietary treatments. Delta-9-desaturase activity was decreased by 53% in DHA-fed SHR and was accompanied by an increase in 16:0 and a reduction in 16:1n-7 content in hepatic microsomes. The DHA diet also increased the levels of eicosapentaenoic acid (20:5n-3) and DHA. The n-6 fatty acid content was also affected in DHA-fed SHR as reflected by a decrease in gamma-linolenic acid (18:3n-6), arachidonic acid (20:4n-6), adrenic acid (22:4n-6), and docosapentaenoic acid (22:5n-6). A higher proportion of dihomo-gamma-linolenic acid (20:3n-6) and a lower proportion of 20:4n-6 is indicative of impaired delta-5-desaturase activity. The alterations in fatty acid composition and metabolism may contribute to the antihypertensive effect of DHA previously reported.

Animals↗
PubMed2003

Difference in effect of myristic and stearic acid on plasma HDL cholesterol within 24 h in young men.

BACKGROUND: There is increasing evidence that postprandial triacylglycerol (TAG)-rich lipoproteins (TRL) may be related to atherogenic risk. Little is known about the acute effect of individual dietary saturated fatty acids on plasma lipids and lipoproteins. OBJECTIVE: To investigate the effect of two prevalent dietary saturated fatty acids, stearic and myristic acid on postprandial and 24 h fasting plasma lipoprotein TAG and cholesterol concentrations. DESIGN: Ten young healthy men were served two meals (1.2 g fat/kg body weight) containing fat enriched in either stearic acid (S) (shea butter) or myristic acid (M) (produced by inter-esterification) in a randomised, cross-over study. The meals were given in the morning after 12 h of fasting and again after 8 h (in the afternoon). The S and M containing meals were given at different days separated by a washout period. Blood samples were taken before the meal and 2,4,6,8, and 24 h after the first meal. RESULTS: The M meal resulted in a higher postprandial HDL TAG response than S (P=0.03 I), (diet x time interaction), while no differences were observed in other lipid fractions. Twenty-four hours after the M meal fasting, HDL cholesterol was higher (P=0.05) and HDL TAG lower (P<0.001) than at baseline. CONCLUSIONS: Intake of individual dietary SFA may affect fasting HDL cholesterol within 24 h. Thus after this short period HDL cholesterol concentration was higher after myristic acid than stearic acid. Myristic acid resulted in a higher increase in postprandial HDL TAG than stearic acid.

Adult↗
PubMed1983

Measles-virus-persistent infection in BGM cells. Modification of the incorporation of [3H]arachidonic acid and [14C]stearic acid into lipids.

In BGM cells chronically infected with measles virus, although the composition of the phospholipids is unaltered, the fatty acid composition is modified. Uninfected, lytic and persistently infected cells were labelled with [3H]arachidonic acid and [14C]stearic acid and their metabolic fate analysed. No difference in the total incorporation was observed in the different systems. However, the [14C]stearic acid and [3H]arachidonic acid were incorporated up to 2-fold and 13-fold respectively greater into the neutral lipid of persistently infected compared with that of uninfected cells. Both radioactive fatty acids were specifically accumulated in the triacylglycerol and non-esterified fatty acids fractions. Lytically infected cells were similar to uninfected cells. Although there was no significant difference in the incorporation of radioactivity into the total phospholipid in either system, there was a large decrease in [3H]arachidonic acid incorporated into phosphatidylethanolamine and to a lesser extent phosphatidylcholine and phosphatidylinositol in persistently infected cells. [14C]Stearic acid incorporation was also reduced in phosphatidylcholine and phosphatidylethanolamine fractions of persistently infected cells.

Animals↗
PubMedDate not supplied

Charge-transfer chromatographic study on the interaction of amino acids with ethoxylated stearic acid surfactants.

The interaction of amino acids with ethoxylated stearic acid nonionic surfactants was studied by charge-transfer reversed-phase thin-layer chromatography and the relative strength of interaction was calculated. In the majority of cases the surfactant has a negligible effect on the hydrophobicity of amino acids. Only the binding of Asn, Cys, Gln, Leu, Lys, Met, Nle, Phe, Ser, Trp and Tyr to the surfactants was observed, however, the strength of interaction was fairly low. Stepwise regression analysis proved that the electronic parameters of the amino acids have the highest impact on the strength of interaction. This finding supports the hypothesis that the binding of ethoxylated stearic acid nonionic surfactants to proteins involves more than one amino acid residues and that the hydrophilic forces have a considerable impact on the interaction.

Amino Acids↗
PubMed2000

Studies on the cyclosporin A loaded stearic acid nanoparticles.

Stearic acid nanoparticles were prepared in this study by melt-homogenization to investigate the possibility of them as a new kind of drug carrier system. Some physicochemical properties of stearic acid nanoparticles were studied and morphology examined by transmission electron microscope. Cyclosporin A as a model drug was then encapsulated into stearic acid nanoparticles. Following the establishment of high performance liquid chromatography assay for cyclosporin A analysis in stearic acid nanoparticles or blood samples, the encapsulation ratio of cyclosporin A to stearic acid nanoparticles was estimated and pharmacokinetics as well as bioavailability of cyclosporin A stearic acid nanoparticles after oral administration to Wistar rats were studied, using the Sandimmun Neoral(R) (an available microemulsion system of cyclosporin A) as a reference. The mean diameter of cyclosporin A stearic acid nanoparticles was 316.1 nm, while the encapsulation ratio of cyclosporin A to stearic acid nanoparticles reached to 88.36%. It was demonstrated by IR spectra and differential scanning calorimetry that there was no chemical reaction occurred between the cyclosporin A and stearic acid. The relative bioavailability of cyclosporin A stearic acid nanoparticles over reference was nearly 80%, and the time to reach maximum concentration (T(max)) of cyclosporin A after oral administration of cyclosporin A stearic acid nanoparticles was delayed significantly than the reference, suggesting an obvious sustained release effect. The stearic acid nanoparticles might be a very potential drug carrier.

Administration, Oral↗
PubMed1989

UVB irradiation and distribution of arachidonic acid (20:4) and stearic acid (18:0) in human keratinocytes.

Human keratinocytes (NCTC 2544) in culture were labeled with either 14C-arachidonic acid or 14C-stearic acid and then exposed to UVB irradiation (9 or 90 mJ/cm2). Exposure of the keratinocytes to UVB irradiation resulted in considerable rearrangement of the membrane fatty acids. Following UVB irradiation the percentage amounts of 14C-arachidonic acid and 14C-stearic acid were significantly decreased in phospholipids, in phosphatidylethanolamine and in phosphatidylcholine. The liberation of stearic acid from phospholipids was accompanied by accumulation of radiolabel into the culture medium, but in 14C-arachidonic acid-labeled cells the amount of radiolabel in the culture medium was not changed following UVB irradiation despite liberation of arachidonic acid from phospholipids. It seems evident that, following UVB irradiation, the rate of reincorporation of liberated 14C-arachidonic acid, a polyunsaturated fatty acid, is higher and thus different from that of a saturated fatty acid, 14C-stearic acid. The present study suggests that exposure of keratinocytes to UVB irradiation is followed by liberation of both saturated and unsaturated fatty acids and also considerable reacylation of the unsaturated fatty acids.

Arachidonic Acid↗
PubMed1997

Arachidonic acid modulates [14C]stearic acid incorporation into phosphatidylinositol, in human neuroblastoma cells.

In the human neuroblastoma cell line SK-N-BE(2), arachidonic acid (AA), supplied in the medium at micromolar concentrations, markedly enhanced [14C]stearic acid (SA) (but not [14C]palmitic acid or [14C]oleic acid) incorporation into phosphatidylinositol (PtdIns). AA failed to stimulate [14C]SA incorporation into PtdIns precursors, namely phosphatidic acid and cytidinediphosphodiacylglycerol: furthermore, enhanced [14C]SA incorporation, brought about by exogenously administered AA, was not restricted to PtdIns tetraenoic species. When cells were pulsed for 1 h with [14C]SA (either in the presence or absence of AA) and then reincubated in AA- and [14C]SA-free medium, a marked loss of radioactivity from PtdIns was observed, that however was restricted to molecular species other than tetraenoic. These results are discussed in the light of possible mechanisms through which PtdIns achieves the 1-stearoyl-2-arachidonoyl configuration.

Arachidonic Acid↗
PubMed1985

Digestion and absorption of lipids and bile acids in sheep fed stearic acid, oleic acid, or tristearin.

Sheep were fed diets containing 7.5% added stearic acid, oleic acid, or tristearin for 21 days. In addition, 50 microCi/kg cerium-141 was included for the last 10 days on experimental diets as an unabsorbed reference substance. In the rumen dietary triglycerides were approximately 50% hydrolyzed, and hydrogenation resulted in saturation of the free fatty acid fraction. Some net synthesis of phospholipids, presumably microbial phospholipids, occurred in the rumen. In the intestine immediately distal to the pylorus, extensive secretion of bile acids, cholesterol, phospholipids, triglycerides, free fatty acids, and lipase occurred. This resulted in doubling of fatty acid fluxes through the duodenum. These endogenous secretions were reabsorbed rapidly however, with the major site of lipid and bile acid absorption in the region .6 to 4 m distal to the pylorus. Additional but less absorption occurred in the more distal segments of the small intestine. Overall absorption of stearic acid, oleic acid, and tristearin supplements was in the range 60 to 70%, and no differences were apparent between fats. Unsaturated fatty acids were over 90% absorbed as compared with 55 to 65% for saturated fatty acids. No significant effect of any of the supplements was observed on ruminal total volatile fatty acids, ratios of volatile fatty acids, or on overall cellulose or caloric digestion.

Abomasum↗
PubMed1992

The metabolism of tetradecylthiopropionic acid, a 4-thia stearic acid, in the rat. In vivo and in vitro studies.

The metabolism of [1-14C]tetradecylthiopropionic acid (TTP), a 4-thia stearic acid, and its sulphoxide, [1-14C]texadecylsulphoxypropionic acid (TTP-SO), has been studied in intact rats, in isolated rat hepatocytes, and in rat liver mitochondria. Two pathways of oxidation (beta-oxidation and omega-oxidation) have been demonstrated. TTP is incorporated, in vivo, into tissue triacylglycerol and phospholipids, it is oxidized to CO2, and it is excreted in urine, mainly as carboxypropylsulphoxypropionic acid and a little as carboxymethylsulphoxypropionic acid. TTP-SO is metabolized, in vivo, more rapidly to the same two omega-oxidation products. In hepatocytes TTP is incorporated into triacylglycerol and phospholipids even more rapidly than stearic acid. It is recovered mainly in the 1-position of phosphatidylcholine. Some is oxidized to CO2 and acid-soluble products. TTP-SO is mainly omega-oxidized to the same metabolites as are found in urine. A small fraction is incorporated into phospholipids or oxidized to CO2. In isolated mitochondria [1-14C]TTP is converted into 14CO2, radioactive malonic semialdehyde, and addition products of malonic semialdehyde. In the presence of phenylhydrazine, malonic semialdehyde phenylhydrazone is the dominating product. In soluble extracts of mitochondria [1-14C]malonic semialdehyde is oxidized directly to 14CO2 in the presence of CoA and NAD+, probably by the (methyl)malonic acid semialdehyde dehydrogenase (EC 1.2.1.27).

Animals↗
PubMed2006

Eicosapentaenoic acid and 3,10 dithia stearic acid inhibit the desaturation of trans-vaccenic acid into cis-9, trans-11-conjugated linoleic acid through different pathways in Caco-2 and T84 cells.

Stearoyl-CoA desaturase (SCD) is a key enzyme that determines the composition and metabolic fate of ingested fatty acids, in particular the conversion of trans-vaccenic acid (TVA) to conjugated linoleic acid (CLA). The present study addressed the hypothesis that intestinal TVA absorption and biotransformation into CLA can be modulated by EPA and 3,10-dithia stearic acid (DSA) via altered SCD mRNA levels and desaturation indices (cis-9, trans-11-CLA:TVA and oleic acid:stearic acid ratios) in Caco-2 and T84 cells, two well-established in vitro models of the human intestinal epithelium. The study determined the effect of acute (3 h with 0.3 mm-EPA or 0.3 mm-DSA) and acute-on-chronic (1 week with 0.03 mm-EPA or -DSA, followed by respectively, 0.3 mm-EPA or -DSA for 3 h) treatments. In both cell lines, acute EPA treatment did not alter SCD desaturation indices, whereas the acute-on-chronic treatment affected these surrogate markers of SCD activity. This was associated with reduced sterol regulatory-element binding protein-1c and SCD mRNA levels. In contrast, acute and acute-on-chronic DSA treatments significantly reduced SCD desaturation indices without affecting SCD mRNA levels in Caco-2 cells. The present study on intestinal cells shows that the conversion rate of TVA to c9, t11-CLA is affected by other fatty acids present in the diet such as EPA, confirming previous observations in hepatic and mammary cell models.

Caco-2 Cells↗
PubMed1994

Biosynthesis of gangliosides containing C18:1 and C20:1 [3-14C]sphingosine after administrating [1-14C]palmitic acid and [1-14C]stearic acid to rat cerebellar granule cells in culture.

The biosynthesis of ganglioside molecular species containing sphingosine of different structure was investigated by administrating rat cerebellar granule cells in culture with [1-14C]palmitic and [1-14C]stearic acids which are the precursors for sphingosine biosynthesis. The incorporation of radioactivity into the sphingosine of the ganglioside species containing C20:1 sphingosine after administrating [1-14C]stearic acid was low in comparison with the incorporation of radioactivity into the sphingosine of ganglioside species containing C18:1 sphingosine after administration of [1-14C]palmitic acid, but the ratio between the radioactivity incorporated in the C20:1 and the C18:1 sphingosine of C20 and C18 ganglioside species progressively increased when the cell culture was prolonged. Ceramide-containing radioactive sphingosine was found after palmitic or stearic acid administration. Ceramide-containing C20:1 sphingosine found after adding stearic acid was about 5% of that synthesized starting from palmitic acid and containing C18:1 sphingosine. Free radioactive C18:1 and C20:1 sphingosine were found after adding radioactive palmitic or stearic acid. This is representative of a catabolic process occurring after biosynthesis of the complex sphingolipid starting from the radioactive precursor. In fact it has been proved that only saturated sphingosines are used for the synthesis of complex sphingolipids, the introduction of the double bond at position four of the sphingoid chain occurring at the level of ceramide [Rother, J., van Echten, G., Schwarzmann, G. & Sandhoff, K. (1992) Biochem. Biophys. Res. Commun. 189, 14-20]. Saturated sphingosines were not present. The lack of free C20:0 sphingosine confirms the hypothesis that the C20:0 sphingosine synthesis and the process (C20:0 sphingosine-->C20:0 ceramide-->C20:1 ceramide) occur in the correct quantity for the synthesis of C20:1 gangliosides. Moreover, we found only traces of free C20:1 sphingosine, at days 8 and 15 of cell culture when the biosynthesis of complex C20:1 gangliosides and the related catabolic processes occur to a higher extent, thus excluding the idea that a large amount of C20:0 sphingosine can be acylated to C20:0 ceramide and dehydrogenated to C20:1 ceramide which, being not used for ganglioside biosynthesis, is immediately catabolised to C20:1 sphingosine.

Animals↗
PubMed2002

Mapping the Fas locus controlling stearic acid content in soybean.

Increasing the stearic acid content to improve soybean [ Glycine max (L) Merr] oil quality is a desirable breeding objective for food-processing applications. Although a saturated fatty acid, stearic acid has been shown to reduce total levels of blood cholesterol and offers the potential for the production of solid fat products (such as margarine) without hydrogenation. This would result in the reduction of the level of trans fat in food products and alleviate some current health concerns. A segregating F(2) population was developed from the cross between Dare, a normal stearic acid content cultivar, and FAM94-41, a high stearic acid content line. This population was used to assess linkage between the Fas locus and simple sequence repeat (SSR) markers. Three SSR markers, Satt070, Satt474 and Satt556, were identified to be associated with stearic acid (P < 0.0001, r(2) > 0.61). A linkage map consisting of the three SSR markers and the Fas locus was then constructed in map order, Fas, Satt070, Satt474 and Satt556, with a LOD score of 3.0. Identification of these markers may be useful in molecular marker-assisted breeding programs targeting modifications in soybean fatty acids.

Chromatography, Gas↗