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PubMed1970

Molecular species of mono-, di-, and triphosphoinositides of bovine brain.

The mono-, di-, and triphosphoinositides of bovine brain were isolated by chromatography on columns of DEAE-cellulose, alumina, and silicic acid. The major molecular species in each phosphoinositide class were identified and quantitatively estimated by combined thin-layer and gas-liquid chromatography of the component diglycerides, which were released by hydrolysis with a specific brain phosphodiesterase. The diglycerides were treated with pancreatic lipase, and the positional distribution of the fatty acids was determined. Over 27 molecular species were identified, and these accounted for about 95% of each phosphoinositide class, but the 1-stearate 2-arachidonate derivative contributed more than 40% of the total in each class. The other molecular species also were qualitatively and quantitatively similar in the three phosphoinositide classes. All the long-chain and polyunsaturated acids were confined to the 2-position and were preferentially paired with stearic acid in the 1-position. Oleic acid in the 2-position was about equally divided between species with palmitic and stearic acids in the 1-position. These results suggest that the mono-, di-, and triphosphoinositides of the bovine brain have similar compositions and that the various molecular species may be metabolically related.

Animals↗
PubMed1993

The role of fatty acid saturation on plasma lipids, lipoproteins, and apolipoproteins: I. Effects of whole food diets high in cocoa butter, olive oil, soybean oil, dairy butter, and milk chocolate on the plasma lipids of young men.

The present studies were conducted to evaluate the cholesterolemic effects of whole-food diets high in stearic acid. In study no. 1, normocholesterolemic young men were fed diets high in stearic acid provided by cocoa butter (CB); oleic acid provided by olive oil (OO); linoleic acid provided by soybean oil (SO); and myristic acid (and lauric acid) provided by dairy butter (B). In study no. 2, different subjects with similar baseline characteristics were fed diets high in stearic acid provided by milk chocolate (C), CB, CB+B (4:1, MIX), and myristic (and lauric) acid provided by B. Both studies used a randomized, crossover, double-blind experimental design, and experimental subjects (n = 18 for study no. 1 and n = 15 for study no. 2) in each study consumed every diet for 26 days with a 1-month wash-out period between each experimental period. The diets provided 37% of calories from fat, of which 81% was provided by the test fat. Ten ounces (280 g) C was provided daily by the C diet. In study no. 1, the B diet was hypercholesterolemic, whereas the SO diet was hypocholesterolemic, compared with the other diets. The OO and SO diets were hypocholesterolemic compared with the CB diet. Low-density lipoprotein (LDL) cholesterol levels, in general, paralleled the changes in plasma total cholesterol levels. SO significantly decreased apolipoprotein (apo) B levels compared with the other diets. Plasma very-low density lipoprotein (VLDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and apo A-I levels were unaffected by the experimental diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1978

[Concentration of free fatty acids in muscle following administration of corticotropin and hydrocortisone].

Experiments were conducted on rats; the gas chromatographic method was applied to the study of the free fatty acids content in the gastrocnemius 30 minutes after the intraperitoneal injection of adrenocorticotropic hormone (ACTH)--1 Unit per 100 g and hydrocortisone acetate--1 mg per 100 gm of body weight. It was shown that in the resting muscles ACTH increased the content of stearic acid, whereas hydrocortisone--of both stearic oleic acids. The changes in the content of other free fatty acids were insignificant. During the short-term activity the content of stearic acid in the regimen of single rhythmic contractions in the gastrocnemius of intact rats increased. In experiments with ACTH and hydrocortisone this elevation was much less and not significant. ACTH and hydrocortisone stimulated the stearic acid consumption by the muscles during the activity.

Adrenocorticotropic Hormone↗
PubMed1999

Dietary saturated fats and their food sources in relation to the risk of coronary heart disease in women.

BACKGROUND: Metabolic studies suggest that saturated fatty acids differ in their effects on blood lipids. OBJECTIVE: The objective was to examine the associations between intakes of individual saturated fatty acids and their food sources in relation to the risk of coronary heart disease (CHD). DESIGN: This was a prospective cohort study of 80082 women in the Nurses' Health Study aged 34-59 y. Subjects had no known cardiovascular disease, cancer, hypercholesterolemia, or diabetes, and completed validated food-frequency questionnaires in 1980. RESULTS: During 14 y of follow-up, we documented 939 incident cases of major CHD events. In multivariate analyses in which age, smoking, and other covariates were controlled for, intakes of short- to medium-chain saturated fatty acids (4:0-10:0) were not significantly associated with the risk of CHD. In contrast, intakes of longer-chain saturated fatty acids (12:0-18:0) were each separately associated with a small increase in risk. The multivariate RR for a 1% energy increase from stearic acid was 1.19 (95% CI: 1.02, 1.37). The ratio of polyunsaturated to saturated fat was strongly and inversely associated with CHD risk (multivariate RR for a comparison of the highest with the lowest deciles: 0.58; 95% CI: 0.41, 0.83; P for trend < 0.0001). Conversely, higher ratios of red meat to poultry and fish consumption and of high-fat to low-fat dairy consumption were associated with significantly greater risk. CONCLUSION: A distinction between stearic acid and other saturated fats does not appear to be important in dietary advice to reduce CHD risk, in part because of the high correlation between stearic acid and other saturated fatty acids in typical diets.

Adult↗
PubMed1997

Coagulation and fibrinolysis factors in healthy subjects consuming high stearic or trans fatty acid diets.

The effects of stearic acid (C18:0) and trans fatty acids on variables related to coagulation and fibrinolysis were studied in 80 healthy humans average age 29 +/- 9 years. All subjects consumed a baseline diet high in saturated fatty acids, mainly from dairy fat for 5 weeks. After this baseline diet they were allocated either to a diet high (8.7% of energy, En%) in trans fatty acids from partially hydrogenated vegetable oil (40 subjects) or a diet high (9.3 En%) in stearic acid (40 subjects) for 5 weeks. All diets contained 32.2-33.9 En% fat, 14.6-15.8 En% saturated plus trans fatty acids, 12.2-12.5 En% cis-monounsaturated and 2.9-3.5 En% polyunsaturated fatty acids and 216-250 mg/10 MJ cholesterol. The fats were mixed into solid foods and almost all daily food was provided. In comparison with the baseline dairy fat diet no change was observed in the concentrations of plasma fibrin degradation products and D-dimers. Also the factor VII coagulant activity (F VII:C), tissue type plasminogen activity (tPA) and plasminogen activator inhibitor activity (PAI-1) were not affected by the experimental diets. Small increase in plasma fibrinogen concentration during the stearic acid diet was statistically significant (from 3.49 to 3.63 g/l: p = 0.041), but probably without any biological significance. Both diets increased plasma level of lipoprotein Lp(a). It can be concluded that as far as coagulation and fibrinolysis are concerned there is no need to differentiate between stearic acid or trans monoenoic fatty acids.

Adult↗
PubMed1988

Lack of interaction of rhodopsin chromophore with membrane lipids. An electron-electron double resonance study using 14N:15N pairs.

Electron-electron double resonance (ELDOR) has been applied to the study of specific interactions of 15N-spin-labeled stearic acid with the retinal chromophore of a rhodopsin analogue containing a 14N spin-labeled retinal. Both the 5 and 16 spin-labeled stearic acids were incorporated into the lipid bilayer of rod outer segment membranes containing the spin-labeled pigment. No interaction between the 15N and 14N spin-labels was observed in rhodopsin or the metarhodopsin II state with either of these labeled stearic acids. Therefore in this system the ring portion of the chromophore must be highly sequestered from the phospholipid bilayer in both the rhodopsin and metarhodopsin II forms.

Animals↗
PubMed1991

Potential for enhancing the nutritional properties of milk fat.

Milk fat has been identified as a hypercholesterolemic fat because it contains cholesterol and is primarily saturated. However, different types of dietary saturated fats do not have equivalent effects on plasma cholesterol levels relevant to ingestion of polyunsaturated fats. Research suggests that the hypercholesterolemic effect of saturated fats in human diets is largely due to 12, 14, and 16 carbon chain length fatty acids. Evidence also suggests that stearic acid (C18:0) is as effective as oleic acid (C18:ln-9) in lowering plasma cholesterol levels when either replaces palmitic acid (C16:0) in the diet of men. Milk fat has a unique fatty acid profile with approximately 10% short- and medium-chain length saturated fatty acids (less than 12 carbons) and 35% of total fatty acids from stearic and oleic acids. The contribution of milk products to fat and cholesterol intake in the typical American diet is less than that provided by other animal products. This paper will review the recommendations of the National Cholesterol Education Program, the effects of milk fat ingestion on blood cholesterol, and the rationale and feasibility of three approaches to modifying the lipid composition of milk fat.

Animals↗
PubMed1987

Fatty acid composition of subcutaneous adipose tissue in mother-infant pairs.

The fatty acid composition of microsamples from 10 AGA term, 8 SGA term, 7 AGA preterm and 4 SGA preterm, 2-4 day old infants and their mothers were analyzed. In AGA preterm newborns the mean percent of palmitic and stearic acid was lower and the mean percent of linoleic acid was higher than in AGA term infants indicating that there is an increase in fatty acids derived by synthesis from glucose throughout gestation. SGA infants had relative amounts of palmitic and stearic acid similar to what was found in AGA term infants. This indicates that the enzymes involved in synthesis of fatty acids from glucose are intact in intrauterine growth retardation (IUGR). The absolute amount of adipose tissue and fatty acids, however, is smaller in SGA infants due to a reduced availability of glucose in IUGR gestation. No differences were found in the fatty acid composition of subcutaneous adipose tissue from the mothers in the 4 groups. All mothers had a lower mean percent of palmitic and stearic acid and a higher mean percent of oleic and linoleic acid than their infants, ensuring a transplacental gradient to the fetus of this latter essential fatty acid. The fatty acid composition of plasma free fatty acids generally reflected the composition of the subcutaneous adipose tissue in the infants.

Adipose Tissue↗
PubMed2001

Autoxidation products of normal and genetically modified canola oil varieties determined using liquid chromatography with mass spectrometric detection.

Normal, high stearic acid and high lauric acid canola oil varieties were heated in the presence of air to allow autoxidation to occur. After the reaction, the oils were analyzed using a non-aqueous reversed-phase high-performance liquid chromatographic separation followed by detection using atmospheric pressure chemical ionization mass spectrometry. Oxidized products were separated and identified. The major autoxidation products which remained intact were epoxides and hydroperoxides. Two classes of epoxy triacylglycerols (TAGs) were formed. One class with the epoxy group replacing a site of unsaturation and one class adjacent to a site of unsaturation, as was previously reported for model TAGs. Intact oxidation products resulted mostly from oxidation of oleic acid, while oxidation products of linoleic and linolenic acid chains decomposed to yield chain-shortened species. Both neutral and polar chain-shortened products were observed. Polar chain-shortened decomposition products eluted at very short retention times and required a different chromatographic gradient to separate the molecules. This class of molecules was tentatively identified as core aldehydes. The high stearic acid canola oil yielded more intact oxidation products containing stearic acid, as expected. The high lauric acid oil produced intact oxidation products which contained lauric acid.

Chromatography, Liquid↗
PubMed1998

Postprandial lipaemia and haemostatic factors.

Factor VII activity (FVIIc), a reported risk factor for fatal coronary heart disease, increases transiently after a fat-rich meal. The response shows dose-response characteristics and peak FVIIc and triglyceride concentrations above fasting levels tend to be positively associated. The mechanism is incompletely understood, but appears to require factor IX and the presence in plasma of lipoprotein products of lipolytic activity. Factor XII is not apparently essential. The increase in FVIIc is due to raised activated factor VII (FVIIa) activity, but is not associated with increased thrombin production or changes in fibrinolytic activity. The response of FVIIa appears independent of the proportions of saturated, monounsaturated and polyunsaturated fatty acids in the dietary fat, although dietary stearic acid may be less effective than myristic acid. However, in one study in which deliberate efforts were made to force an increase in plasma free stearic acid, its plasma level was positively associated with postprandial FVIIc. Because FVIIa initiates the thrombotic response to rupture of an atheromatous plaque, a raised postprandial level may represent a transient rise in the likelihood of a clinically significant coronary thrombosis.

Animals↗
PubMed1998

Differential regulation of neurofibromin and p120 GTPase-activating protein by nutritionally relevant fatty acids.

Arachidonic acid, phosphatidic acid, and other lipids inhibit the catalytic fragment of neurofibromin more potently than that of p120 guanosine triphosphatase-activating protein (GAP). The effects of fatty acids other than arachidonic acid on full-length neurofibromin and p120 GAP, to our knowledge, have not been studied. In this study, we analyzed the effects of eight nutritionally relevant fatty acids on guanosine triphosphatase (GTPase) stimulatory activity of full-length neurofibromin and p120 GAP. The fatty acids tested were saturated stearic acid, monounsaturated oleic acid, and three n-6 and three n-3 polyunsaturated fatty acids. Analysis was performed by Ras immunoprecipitation GTPase assay. The full-length p120 GAP expressed in insect Sf9 cells and immunoaffinity-purified full-length neurofibromin were used. In contrast to neurofibromin, which was readily inhibited by stearic and oleic acid, p120 GAP was only weakly inhibited even at high concentrations (> 80 microM). Neurofibromin was also two- to threefold more sensitive to inhibition by other fatty acids tested. A chimeric protein in which the neurofibromin catalytic domain was fused to the NH2-terminal sequences of p120 GAP was used to determine that differential sensitivity to fatty acid inhibition maps to the catalytic domain of the proteins. These results indicate that nutritionally relevant fatty acids can modulate the GTPase function of c-Ha-Ras protein by inhibiting GTPase stimulatory activity of two Ras regulators, full-length neurofibromin and p120 GAP, at physiologically relevant concentrations in vitro.

Animals↗
PubMed1975

The relation between lipid mobility and the specific hormone binding of thyroid membranes.

1. The specific binding of thyroid-stimulating hormone to isolated human thyroid membranes was examined under a variety of conditions. 2. In phosphate-saline buffer (in the presence of 0.14 M-NaCl) on increasing the temperature the binding of the hormone is increased, the plots of bound/free hormone against temperature showing a distinct break around 30 degrees C. 3. Detailed analysis showed that the increased binding is associated with an increase in the number of binding sites. 4. The motional characteristics of three membrane-bound fluorescent probes, 2-(9-anthroyl)palmitic acid, 12-(9-anthryl)stearic acid and N-1-naphthyl-N-phenylamine, were also examined as a function of temperature by measuring both fluorescence polarizations and lifetimes. 5. The results indicated that the 'fluidity' of membrane lipids also increased with temperature. The temperature-dependence of this property also shows a change at about 30 degrees C. 6. Bivalent cations decreased both membrane fluidity and hormone binding. 7. Similar correlations were found between the binding of adrenocorticotrophic hormone and the fluidity of the plasma membranes obtained from adrenal-cortical cells, with the discontinuity occurring in this case at 23 degrees C. 8. The possibility of lipid mobility being important in controlling hormone-receptor function is discussed.

Anthracenes↗
PubMed2003

Achievement of dietary fatty acid intakes in long-term controlled intervention studies: approach and methodology.

OBJECTIVE: To describe the calculations and approaches used to design experimental diets of differing saturated fatty acid (SFA) and monounsaturated fatty acid (MUFA) compositions for use in a long-term dietary intervention study, and to evaluate the degree to which the dietary targets were met. DESIGN, SETTING AND SUBJECTS: Fifty-one students living in a university hall of residence consumed a reference (SFA) diet for 8 weeks followed by either a moderate MUFA (MM) diet or a high MUFA (HM) diet for 16 weeks. The three diets were designed to differ only in their proportions of SFA and MUFA, while keeping total fat, polyunsaturated fatty acids (PUFA), trans-fatty acids, and the ratio of palmitic to stearic acid, and n-6 to n-3 PUFA, unchanged. RESULTS: Using habitual diet records and a standardised database for food fatty acid compositions, a sequential process of theoretical fat substitutions enabled suitable fat sources for use in the three diets to be identified, and experimental margarines for baking, spreading and the manufacture of snack foods to be designed. The dietary intervention was largely successful in achieving the fatty acid targets of the three diets, although unintended differences between the original target and the analysed fatty acid composition of the experimental margarines resulted in a lower than anticipated MUFA intake on the HM diet, and a lower ratio of palmitic to stearic acid compared with the reference or MM diet. CONCLUSIONS: This study has revealed important theoretical considerations that should be taken into account when designing diets of specific fatty acid composition, as well as practical issues of implementation.

Adult↗
PubMed1978

Distribution of radioactivity in myelin lipids following subcutaneous injection of [14C]stearate.

Blood fatty acids are an important parameter for the synthesis of brain myelin as exogenous stearic acid is needed: after subcutaneous injection to 18-day-old mice this labelled stearic acid is transported into brain myelin and incorporated into its lipids. However the acid is partly metabolized in the brain by elongation (thus providing very long chain fatty acids, mainly lignoceric acid) or by degradation to acetate units (utilized for synthesis of medium chain fatty acids as palmitic acid, and cholesterol). These metabolites are further incorporated into myelin lipids. The myelin lipid radioactivity increases up to 3 days; most of the activity is found in phospholipids; their fatty acids are labelled in saturated as well as in polyunsaturated homologues but sphingolipids, especially cerebrosides, contain also large amounts of radioactivity (which is mainly found in very long chain fatty acids, almost all in lignoceric acid). The occurrence of unesterified fatty acids must be pointed out, these molecules unlike other lipids, are found in constant amount (expressed in radioactivity per mg myelin lipid).

Animals↗
PubMed2001

Identification of a mammalian long chain fatty acyl elongase regulated by sterol regulatory element-binding proteins.

Fatty acids are synthesized de novo from acetyl-CoA and malonyl-CoA through a series of reactions mediated by acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS). In rodents, the principal fatty acid produced by FAS is palmitic acid (16:0). Sterol regulatory element-binding proteins (SREBPs) enhance the transcription of many genes responsible for fatty acid synthesis. In transgenic mice that overexpress SREBPs in liver, the rate of fatty acid synthesis is markedly increased, owing to the activation of these biosynthetic genes, which include ATP citrate lyase, ACC, FAS, and stearoyl-CoA desaturase. The fatty acids that accumulate in livers of SREBP transgenic mice are 18 carbons rather than 16 carbons in length, suggesting that the enzymes required for the elongation of palmitic to stearic acid may be induced. Here, we report the cDNA cloning of a murine long chain fatty acyl elongase (LCE) that was identified initially by oligonucleotide array analysis of mRNA from SREBP transgenic mouse livers. LCE mRNA is highly expressed in liver and adipose tissue. The cDNA encodes a protein of 267 amino acids that shares sequence identity with previously identified very long chain fatty acid elongases. Cells that overexpress LCE show enhanced addition of 2-carbon units to C12-C16 fatty acids. We provide evidence that LCE catalyzes the rate-limiting condensing step in this reaction. The current studies suggest that mouse LCE expression is increased by SREBPs and that the enzyme is a component of the elusive mammalian elongation system that converts palmitic to stearic acid.

Acetyltransferases↗
PubMed1992

Differential modulation of a sodium conductance in skeletal muscle by intracellular and extracellular fatty acids.

Voltage-activated sodium channels of cultured skeletal muscle show diametrically divergent responses to intracellular vs. extracellular exposure to free fatty acids. Intracellular exposure to 1-20 microM arachidonic acid increased the magnitude of voltage-activated sodium currents, but not potassium currents, in whole cell recordings of human primary muscle cells and in the C2C12 mouse cell line. Oleic and stearic acids also stimulated increased sodium currents. In contrast, extracellular exposure to 5-10 microM arachidonic acid reversibly inhibited inward currents. Externally applied oleic acid was a less effective inhibitor, and stearic acid (up to 20 microM) produced no inhibition. The difference in sodium current responses to intracellular vs. extracellular exposure indicates that fatty acids can modulate skeletal muscle sodium channel function by at least two different pathways.

Arachidonic Acid↗
PubMed1987

Metabolism in humans of cis-12,trans-15-octadecadienoic acid relative to palmitic, stearic, oleic and linoleic acids.

Mixtures of triglycerides containing deuterium-labeled hexadecanoic acid (16:0), octadecanoic acid (18:0), cis-9-octadecenoic acid (9c-18:1), cis-9,cis-12-octadecadienoic acid (9c, 12c-18:2) and cis-12,trans-15-octadecadienoic acid (12c,15t-18:2) were fed to two young-adult males. Plasma lipid classes were isolated from samples collected periodically over 48 hr. Incorporation and turnover of the deuterium-labeled fats in plasma lipids were followed by gas chromatography-mass spectrometry (GC-MS) analysis of the methyl ester derivatives. Absorption of the deuterated fats was followed by GC-MS analysis of chylomicron triglycerides isolated by ultracentrifugation. Results were the following: (i) endogenous fat contributed about 40% of the total fat incorporated into chylomicron triglycerides; (ii) elongation, desaturation and chain-shortened products from the deuterated fats were not detected; (iii) the polyunsaturated isomer 12c,15t-18:2 was metabolically more similar to saturated and 9c-18:1 fatty acids than to 9c,12c-18:2; (iv) relative incorporation of 9c,12c-18:2 into phospholipids did not increase proportionally with an increase of 9c,12c-18:2 in the mixture of deuterated fats fed; (v) absorption of 16:0, 18:0, 9c-18:1, 9c,12c-18:2 and 12c,15t-18:2 were similar; and (vi) data for the 1- and 2-acyl positions of phosphatidylcholine and for cholesteryl ester fractions reflected the known high specificity of phosphatidylcholine acyltransferase and lecithin:cholesteryl acyltransferase for 9c,12c-18:2. These results illustrate that incorporation of dietary fatty acids into human plasma lipid classes is selectively controlled and that incorporation of dietary 9c,12c-18:2 is limited. These results suggest that nutritional benefits of diets high in 9c,12c-18:2 may be of little value to normal subjects and that the 12c,15t-18:2 isomer in hydrogenated fat is not a nutritional liability at the present dietary level.

Adult↗
PubMed1973

Food particles as a site for biohydrogenation of unsaturated fatty acids in the rumen.

On incubation of linoleic acid with strained rumen contents from sheep, it was observed that conversion of linoleic acid into C(18:1)trans-11 monoenoic acid and subsequently into stearic acid was largely associated with the food-particle fraction. The bacteria, protozoa and cell-free supernatant together contributed less than 30% to the overall change in the added C(18:2) fatty acid.

Animals↗