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PubMed2004

Two Delta9-stearic acid desaturases are required for Aspergillus nidulans growth and development.

Unsaturated fatty acids are important constituents of all cell membranes and are required for normal growth. In the filamentous fungus Aspergillus nidulans, unsaturated fatty acids and their derivatives also influence asexual (conidial) and sexual (ascospore) sporulation processes. To investigate the relationship between fatty acid metabolism and fungal development, we disrupted the A. nidulans sdeA and sdeB genes, both encoding Delta9-stearic acid desaturases responsible for the conversion of palmitic acid (16:0) and stearic acid (18:0) to palmitoleic acid (16:1) and oleic acid (18:1). The effects of sdeA deletion on development were profound, such that growth, conidial and ascospore production were all reduced at 22 and 37 degrees C. Total fatty acid content was increased over 3-fold in the DeltasdeA strain, reflected in up-regulation of the expression of the fasA gene encoding the alpha chain of the fatty acid synthase, compared to wild type. Stearic acid accumulated approximately 3-fold compared to wild type in the DeltasdeA strain, while unsaturated fatty acid production was decreased. In contrast, disruption of sdeB reduced fungal growth and conidiation at 22 degrees C, but did not affect these processes at 37 degrees C compared to wild type. Interestingly, ascospore production was increased at 37 degrees C for DeltasdeB compared to wild type. Total fatty acid content was not increased in this strain, although stearic acid accumulated 2-fold compared to wild type, and unsaturated fatty acid production was decreased. Combining the DeltasdeA and DeltasdeB alleles created a synthetic lethal strain requiring the addition of oleic acid to the medium for a modicum of growth. Taken together, our results suggest a role for sdeA in growth and development at all temperatures, while sdeB is involved in growth and development at lower temperatures.

Aspergillus nidulans↗
PubMed1966

Determination of brain gangliosides by determination of ganglioside stearic acid.

A new method is described for the determination of brain gangliosides by measuring stearic acid, the chief acid of gangliosides, in an appropriately purified brain extract. The method includes extraction of tissue with chloroform-methanol, extraction of gangliosides from the extract with 0.1 M KCl, evaporation of the aqueous phase, methanolysis, and gas-liquid chromatography of the resultant methyl esters with a double internal standard. The method depends on the simple composition of ganglioside fatty acids (80% stearic acid) and allows determination of less than 0.05 micromole of gangliosides. Interfering lipids are removed from the ganglioside extract by washing with chloroform-methanol-water. The effects of contamination with nonlipid N-acetylneuraminic acid are avoided.

Animals↗
PubMed2002

Temperature effect on a high stearic acid sunflower mutant.

Vegetable oil with elevated saturated fatty acid content may be useful for producing solid fat without hydrogenation or transesterification. Under the nutritional point of view stearic acid is preferred to other saturated fatty acids because of its neutral effect on serum cholesterol lipoproteins. Selection of a very high stearic acid sunflower (Helianthus annuus L.) line (CAS-14), with up to a 37.3% of stearic acid in the seed oil, and the relationship between the expression of this character and the growth temperature are presented. The mutant was selected from the M(2) progeny of 3000 mutagenized seeds (4 mM sodium azide mutagenesis treatment) by analysing the fatty acid composition of half-seed by gas liquid chromatography. In order to genetically fix the mutant character, plants were grown at high day/night temperatures during seed formation. We found that temperatures higher than 30/20 degrees C are required for good expression of the phenotype, the maximum stearic acid content being obtained at 39/24 degrees C. This behaviour is totally opposed to that observed in normal and previously isolated high-stearic acid sunflower lines that contain more stearic acid at low temperature. Thus, a new type of temperature regulation on the stearate desaturation must occur. This line is the sunflower mutant with the highest stearic acid content reported so far.

Fatty Acids↗
PubMed1987

Stearic acid and carcinogenesis.

Decreased membrane rigidity is one of the characteristics of malignant cells, resulting in part from the desaturation of stearic acid into oleic acid. In this study we investigated the influence of stearic acid on tumour cell inhibition in vitro and tumour development in vivo. Stearic acid inhibited the colony-forming ability of 4 out of 5 rat and two human tumour continuous cell lines in vitro. In contrast, the colony-forming ability of rat fibroblasts was not inhibited and that of human foetal lung fibroblasts was inhibited at a higher dose than that required to inhibit human tumour cell lines. Using a model of rat mammary carcinoma induced by nitroso-methyl urea (NMU) the subcutaneous injection of stearic acid at weekly intervals prevented tumour development in 5 to 10 rats. Using iodostearic acid twice weekly, 11 of 19 rats were alive and tumour free at week 22 whilst all of 14 animals injected with NMU alone had died of tumour by the 16th week. The ratio of stearic to oleic acids in erythrocyte membranes was significantly reduced in the tumour-bearing rats, but was normal in tumour-free animals treated with stearic or iodostearic acid. These preliminary data indicate that stearic acid inhibits tumour development in rats.

Animals↗
PubMed2001

Palmitic and stearic acids bind Ca2+ with high affinity and form nonspecific channels in black-lipid membranes. Possible relation to Ca2+-activated mitochondrial pores.

A mitochondrial hydrophobic component that forms Ca2+-induced nonspecific ion channels in black-lipid membranes (Mironova et al., 1997) has been purified and its nature elucidated. It consists of long-chain saturated fatty acids--mainly palmitic and stearic. These fatty acids, similar to the mitochondrial hydrophobic component, bind Ca2+ with high affinity in comparison with unsaturated fatty acids, saturated fatty acids with shorter aliphatic chains, phospholipids, and other lipids. Ca2+-binding is inhibited by Mg2+ but not by K+. For palmitic acid, the Kd for Ca2+ was 5 microM at pH 8.5 and 15 microM at pH 7.5, with the Bmax of 0.48 +/- 0.08 mmol/g. This corresponds to one Ca2+ ion for eight palmitic acid molecules. The data of IR spectroscopy confirm that Ca2+ does not form ionic bonds with palmitic and stearic acids under hydrophobic conditions. It has been found that in the presence of Ca2+, palmitic and stearic acids, but not unsaturated FFA induce a nonspecific permeability in black-lipid membranes. Addition of Ca2+ in order to induce the permeability transition, increases the extractable amount of palmitic and stearic acids, the effect being prevented by a phospholipase A2 inhibitor. The possible involvement of palmitic and stearic acids in the mitochondrial nonspecific permeability is discussed.

Animals↗
PubMed1994

Dietary stearic acid and thromboxane-prostacyclin biosynthesis in normal human subjects.

Ten male subjects were fed a diet rich in stearic acid while they were contained to a metabolic ward. There were three study periods: a 20-d baseline period followed by two 40-d intervention periods. The baseline diet contained 4.4% of energy from stearic acid; one intervention diet was high in stearic acid (7.3% of energy) and the other intervention diet was low in stearic acid (1.6% of energy). The energy contribution of protein, carbohydrate, and fat (16%, 54%, and 30%, respectively) was identical for the two diets. The fat content was distributed equally among saturated, monounsaturated, and polyunsaturated fatty acids. Urinary excretions of thromboxane B2, 2,3-dinor-thromboxane B2, 6-oxo-prostaglandin F1 alpha, and 2,3-dinor-6-oxo-prostaglandin F1 alpha were not significantly different during the two different intervention periods. This suggests that changes in dietary stearic acid do not affect in vivo thromboxane A2 or prostacyclin biosynthesis.

Adult↗
PubMed2006

Neuroprotective effects of stearic acid against toxicity of oxygen/glucose deprivation or glutamate on rat cortical or hippocampal slices.

AIM: To observe the effects of stearic acid, a long-chain saturated fatty acid consisting of 18 carbon atoms, on brain (cortical or hippocampal) slices insulted by oxygen-glucose deprivation (OGD), glutamate or sodium azide (NaN3) in vitro. METHODS: The activities of hippocampal slices were monitored by population spikes recorded in the CA1 region. In vitro injury models of brain slice were induced by 10 min of OGD, 1 mmol/L glutamate or 10 mmol/L NaN3. After 30 min of pre-incubation with stearic acid (3-30 micromol/L), brain slices (cortical or hippocampal) were subjected to OGD, glutamate or NaN3, and the tissue activities were evaluated by using the 2,3,5-triphenyltetrazolium chloride method. MK886 [5 mmol/L; a noncompetitive inhibitor of proliferator-activated receptor (PPAR-alpha)] or BADGE (bisphenol A diglycidyl ether; 100 micromol/L; an antagonist of PPAR-gamma) were tested for their effects on the neuroprotection afforded by stearic acid. RESULTS: Viability of brain slices was not changed significantly after direct incubation with stearic acid. OGD, glutamate and NaN3 injury significantly decreased the viability of brain slices. Stearic acid (3-30 micromol/L) dose-dependently protected brain slices from OGD and glutamate injury but not from NaN3 injury, and its neuroprotective effect was completely abolished by BADGE. CONCLUSION: Stearic acid can protect brain slices (cortical or hippocampal) against injury induced by OGD or glutamate. Its neuroprotective effect may be mainly mediated by the activation of PPAR-gamma.

Animals↗
PubMed1997

Interaction of copper ions with stearic acid Langmuir monolayers and formation of cluster structures in monolayers and Langmuir-Blodgett films.

The interaction of copper ions with a stearic acid Langmuir monolayer resulting in an extremely high level of copper binding to the monolayer in amounts much larger than the number of stearic acid molecules in the monolayer was studied. The shape of the pressure-area isotherm changed drastically upon pH changes from 4 to 6 in the presence of copper ions in the aqueous phase (at concentrations of 10(-5) to 10(-3)(M) or upon addition of copper ions to the aqueous phase under different monolayer compressions. The copper ion concentration changes in the bulk phase, caused by binding to the monolayer, were studied by EPR at the equilibrium after intensive mixing of the bulk phase and were found to depend on pH of the aqueous phase and the extent of monolayer compression. The highest level of binding (up to 100 copper ions per stearic acid molecule, pH 5.6, initial copper concentration 5.10(-4) M) was observed at a surface pressure of about 20 mN/m; further compression of the monolayer and the respective increase in surface pressure caused the reverse growth of aqueous phase copper ion concentration. At the collapse and destruction of the monolayer, the copper ion concentration in the bulk phase was similar to that in the absence of the monolayer. The EPR spectra and SAXS diffractograms of copper-containing stearic acid monolayers confirmed the high copper content in LB films obtained. An STM study of pure stearic acid and the copper-containing monolayer LB films, transferred to graphite wafers from the water subphase surface (pH 5.4) at various copper concentrations, discovered nanosized (about 5 nM) cluster formations on the monolayer surface. The data obtained indicate that the interaction of a charged Langmuir monolayer with copper ions and formation of copper-containing nanostructures depends on monolayer compression and is determined by the arrangement, order, mobility of the monolayer stearic acid molecules and by electrostatics at the interface.

Binding Sites↗
PubMed1997

Stearic acid modifies very low density lipoprotein lipid composition and particle size differently from shorter-chain saturated fatty acids in cultured rat hepatocytes.

Stearic acid as compared to myristate, palmitate, or oleate is poorly incorporated into triacylglycerol, a major lipid component of very low density lipoprotein (VLDL). The present study investigated the effects of these fatty acids on VLDL metabolism in cultured rat hepatocytes. All fatty acids stimulated [2-3H] glycerol incorporation into VLDL lipids and secretion of [3H]-labeled VLDL by hepatocytes. However, the rate of [3H]-labeled VLDL secretion in the presence of nonlabeled stearate (12.8 +/- 0.7 pmol/mg protein/4 h) was 46, 59, and 22% of that observed for those treated with myristate, palmitate, and oleate, respectively. [1-14C]Stearate as a substrate was also less effective than other labeled fatty acids to be incorporated into VLDL lipids. Of total VLDL lipids synthesized from [1-14C] stearate, triacylglycerol accounted for 78% as compared to 88-97% of that derived from palmitate, myristate, and oleate. The amounts of apoB100 and apoB48 were the same in hepatocytes treated with or without exogenous fatty acids. Similarly, the rate of apoB synthesis from [35S] methionine was not affected by exogenous fatty acids. The treatment of cells with various saturated fatty acids increased the particle size of VLDL to different extents. The largest particles of VLDL, with a mean diameter of 79.3 +/- 11.9 nm, were seen in the cells treated with stearate, followed by those treated with palmitate and myristate (45.5 +/- 9.8 and 38.6 +/- 6.8 nm, diameter, respectively). Clearly, hepatocytes treated with stearate secrete less VLDL and produce larger VLDL particles than those treated with shorter-chain saturated fatty acids.

Animals↗
PubMed1995

Positional distribution of stearic acid and oleic acid in a triacylglycerol and dietary calcium concentration determines the apparent absorption of these fatty acids in rats.

In this study the effect of the positional distribution of stearic acid (18:0) and oleic acid (18:1) in a triacylglycerol on absorption of fat, energy and nutrients was investigated in young rats. In addition the effect of dietary calcium on these variables was studied. Forty rats were fed purified diets containing either a fat blend high in 2-oleoyl-distearate or a fat blend high in 1-oleoyl-distearate. Both diets were given at low (0.3 g/100 g) and high (1.0 g/100 g) dietary calcium concentrations. Total fat absorption, expressed as the percentage of fat intake, was significantly lower in rats fed 2-oleoyl-distearate compared with 1-oleoyl-distearate at both dietary calcium concentrations. When expressed as absolute figures, the lower fat absorption in rats fed 2-oleoyl-distearate compared with 1-oleoyl-distearate only reached statistical significance at the high dietary calcium concentration. The reduced absorption of total fat was mainly caused by the lower absorption of stearic acid. The percentage of, but not absolute, absorption of oleic acid and energy were lower in rats fed 2-oleoyl-distearate. Absolute and percentage of calcium absorption were lower in rats fed 2-oleoyl-distearate compared with 1-oleoyl-distearate. Absolute and percentage of magnesium absorption were not significantly affected by the positional distribution of stearic acid and oleic acid in the triacylglycerol, but were decreased at a high dietary calcium concentration. We concluded that the lowered stearic acid absorption from 2-oleoyl-distearate compared with 1-oleoyl-distearate might have been due to the greater formation of insoluble calcium and magnesium soaps in the intestine.

Absorption↗
PubMed1978

Incorporation of stearic acid into brain lipids in the developing brain: blood-brain relationships during development.

The blood-brain relationship for stearic acid varies during development. Subcutaneously injected [1-14C]-stearic acid is taken up by brain. Age-related changes in the metabolism of stearic acid have been determined in mouse brain from birth to maturity. Total lipid radioactivity reaches a maximum at 18 days of age and decreases afterwards until adulthood. However, specific radioactivity presents the highest value at 1 day of age and declines from then on. At any age, the injected acid is taken up and partly metabolized in the brain, either by elongation or by degradation in situ and resynthesis of new fatty acids; it is also desaturated, and the oleic acid thus formed is eventually elongated. The labeled stearic acid is incorporated into brain lipids with a different pattern according to the age of the injected animal.

Age Factors↗
PubMed2006

Effect of molecular sieves on lipase-catalyzed esterification of rutin with stearic acid.

Rutin was acylated with stearic acid in the esterification reaction catalyzed by immobilized Candida antarctica lipase B (Novozym 435) in tert-amyl alcohol with and without molecular sieves. The lipophilic rutin stearate was synthesized by this method, which had a potential use in food, cosmetics, and pharmacy. The structure of rutin stearate was characterized by spectral methods of 1H NMR and 13C NMR, Fourier transform infrared, and UV-vis. The results suggested that the regioselectivity of the lipase-catalyzed esterification of rutin was specific at the C(4''')-position of the rhamnose moiety. It was found that the addition of molecular sieves increased both the reaction rate and the yield. The time effect of adding molecular sieves in the reaction system on the conversion of rutin stearate was further examined. Instead of adding molecular sieves at the beginning of the reaction, the addition of molecular sieves at 5, 18, 24, 31, and 44 h after the beginning of the reaction was also applied. The final conversion for the case to add molecular sieves at 24 h after the beginning of reaction was the highest, with the conversion yield about 46%.

Acylation↗
PubMed2005

Influence of stearic acid on postprandial lipemia and hemostatic function.

It has been suggested that fats rich in stearic acid may result in exaggerated postprandial lipemia and have adverse effects on hemostatic function. The effects of test meals containing different saturated and monounsaturated FA were compared in healthy subjects in a series of studies to investigate this hypothesis. Stearic acid, when present as cocoa butter, resulted in similar postprandial lipemia and factor VII activation compared with a meal containing high-oleic sunflower oil. Stearic acid when presented as shea butter or as randomized stearate-rich TAG resulted in decreased postprandial lipemia and decreased postprandial activation of factor VII. Stearic acid-rich test meals did not result in impaired fibrinolytic activity compared with either a low-fat meal or a meal high in oleate. The difference in responses between the different stearic acid-rich fats appears to be due to varying solid fat contents of the fats at 37 degrees C.

Adult↗
PubMed1986

Microsomal desaturation of stearic acid in relation to lymphocyte activation.

The conversion of stearic acid to oleic acid (delta 9-desaturase) was followed in mouse thymocytes stimulated by either concanavalin A or concanavalin A + interleukin-2 resulting in different rates of cell proliferation. To estimate the plasma membrane turnover of oleic acid as compared to that of a saturated fatty acid, double-label experiments ([14C]oleic acid, [3H]palmitic acid) were performed. Following an inhibition delta 9-desaturase was found to be activated from the fourth hour of stimulation. In the early period of cell activation this process proved to be independent of protein synthesis, whereas in the stage of proliferation it was dependent on it. Increased membrane fluidity in the first 30 min of activation is not likely due to enrichment of oleic acid. Cell proliferation and microsomal desaturation seem to be coupled and an increasing amount of oleic acid is at least one of the factors resulting in increased fluidity of the surface membrane of proliferating cells.

Animals↗
PubMed1993

Influence of linoleic acid on desaturation and uptake of deuterium-labeled palmitic and stearic acids in humans.

Objectives of this study were to investigate the desaturation of stearic acid (18:0) and palmitic acid (16:0), to determine if differences in their metabolism provide a reasonable explantation for differences in their effect on serum cholesterol levels, and to investigate the affect of linoleic acid on delta 9-desaturase products in man. Deuterium-labeled 16:0 and 18:0 were used to follow the metabolism of these fatty acids in young adult male subjects that were pre-fed diets containing two different levels of linoleic acid. Results indicate that absorption of 16:0 and 18:0 was similar when all components of the mixture used to formulate the deuterated fat mixture were kept above the melting point of tristearin. The percent of 18:0 desaturated to 9c-18:1 was higher than the percent of 16:0 desaturated to 9c-16:1 (9.2% vs. 3.9%). The subject-to-subject variability suggests that differences in ability to desaturate saturated fatty acids may be related to the variability observed in response of serum cholesterol levels to dietary saturated fatty acids. Data for the distribution of 16:0 and 18:0 between triacylglycerol and phosphatidylcholine (PC) was markedly different. Based on PC data, phospholipid acyltransferase selectivity was about 2-fold higher for 18:0 than for 16:0. A 2-fold difference in the linoleic acid content of the pre-fed diets had little influence on desaturation or distribution of 16:0 and 18:0 between plasma lipid classes. A deuterium isotope effect was estimated to reduce delta 9-desaturase enzyme activity by 30-50%.

Adult↗
PubMed2000

[The study of the microwave reaction of stearic acid and pentyl amine].

In this study, the microwave reaction of stearic acid and pentyl amine was investigated by FTIR spectroscopy. The results indicated that after mixing the two reactants together, pentyl ammonium stearate was created and it formed acid-salt structure with the stearic acid remained. The results also demonstrated that under microwave radiation, the pentyl ammonium stearate could be not only decomposed, but also dehydrated to form stearic pentyl amide. It suggested that the microwave radiation was an ideal technique to make this chemical reaction much faster and much more thorough.

Amines↗