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PubMed1980

Uptake and metabolism of fatty acids by dispersed adult rat heart myocytes. I. Kinetics of homologous fatty acids.

An adult rat heart myocyte preparation was used to study the uptake and metabolism of the 1-(14)C-labeled free fatty acids decanoate, laurate, myristate, palmitate, and oleate at 37 degrees C in the absence of serum albumin. The rate of total uptake consisted of both a nonsaturable and a saturable component. The nonsaturable component corresponded to the fatty acid accumulating in the free fatty acid fraction, and the rate of this accumulation increased logarithmically as a function of chain length. The saturable component corresponded to that portion of fatty acid converted to the only detectable metabolic products: CO2, triglyceride, and polar lipid. The Km for this process was about 1 microM and was independent of chain length. The Vmax for the saturable component varied only slightly with chain length, from 20 +/- 1 nmol/h-mg of cell protein for decanoate to 47 +/- 18 nmol/h-mg of cell protein for palmitate. The relative product distribution did vary with chain length, however, ranging from primarily carbon dioxide for decanoate to approximately equal quantities of carbon dioxide, triglyceride, and polar lipid for palmitate. Two internal pools of free fatty acid are postulated: a minor pool that equilibrates rapidly with external fatty acid and serves as the precursor for fatty acid activation, and a major pool containing most of the accumulated free acid. These two pools are interconvertible. The data support a simple diffusion or membrane-partitioning process for the accumulation of fatty acid in the second pool. The data presented in this paper are not sufficient to distinguish between a simple diffusion or a carrier-mediated process for uptake into the first pool. The saturation kinetics observed appear to represent a metabolic step such as fatty acid activation, rather than a transport carrier. Evidence of toxicity at a higher concentration of the longer chain fatty acids limits the concentration range that can be studied in the absence of albumin. Decanoate did not appear to be toxic at concentrations up to 300 microM, but laurate at 10 microM and myristate at 5 microM appeared to uncouple respiratory control.

Animals↗
PubMed1993

Modification of spleen phospholipid fatty acid composition by dietary fish oil and by n-3 fatty acid ethyl esters.

We have compared the effects of diets containing purified ethyl esters of either eicosapentaenoic acid, docosahexaenoic acid, or a mixture of both of these compounds, with diets containing either purified fish oil or beef tallow on spleen phospholipid fatty acid composition. Autoimmune mice, the (NZB x NZW)F1 strain, were fed with experimental diets for 14 weeks, after which spleen phospholipids were extracted and separated into classes by HPLC, and the alkenylacyl, alkylacyl, and diacyl subclasses of glycerylphosphatidylethanolamine and glycerylphosphatidylcholine were resolved as their benzoyl esters by HPLC. Fatty acids were analyzed by capillary gas-liquid chromatography of their methyl esters. Each of the marine lipid diets suppressed n-6 fatty acids and elevated n-3 fatty acids in all phospholipids. The eicosapentaenoic acid ethyl ester diets led to high levels of eicosapentaenoic acid and docosapentaenoic acid (C22:5n-3), but little or no increase in docosahexaenoic acid. The docosahexaenoic acid ethyl ester diets elevated docosahexaenoic acid, docosapentaenoic acid, and eicosapentaenoic acid in all phospholipids, indicating that extensive retroconversion of 22 carbon n-3 fatty acids had occurred. These results document changes in the fatty acid composition of mammalian phospholipids that are induced by dietary fish oil triglycerides and by dietary long chain n-3 fatty acid ethyl esters.

Animals↗
PubMed1985

Metabolism of linoleic acid and other essential fatty acids in the epidermis of the rat.

Essential fatty acids are absolutely necessary for maintaining the proper condition of the water barrier (stratum compactum) in the skin. Even direct topical application of linoleic acid or any other Z,Z-(n-6, n-9)-fatty acid to the skin restores the barrier in essential fatty acid-deficient animals. In order to investigate the mechanism by which these polyunsaturated fatty acids exert their activity, radioactively labelled fatty acids were applied to the skin of the live animal and the epidermal lipids were analysed after 1-4 days. Much radioactivity was incorporated into two peculiar lipids, viz. acyl ceramide and acyl acid, which are characteristic of the barrier, in which linoleate was esterified to the end-position of very-long-chain (C30-34) unsaturated omega-hydroxy fatty acids. Strong evidence was obtained which showed that these lipids carry linoleate into the barrier layer where it is converted, probably by lipoxygenase(s), into a series of peroxidated lipids. The lipoxygenase inhibitor, eicosatetraynoic acid, prevents both oxygenation of the polyunsaturated fatty acid and the formation of a healthy skin. This peroxidation may supply the mediators which induce the proper differentiation of the epidermal cells into an effective stratum compactum and a horny layer.

Animals↗
PubMed1990

Modulation of the release of 9-hydroxy-octadecadienoic acid and other fatty acid derived mediators from guinea-pig pulmonary macrophages.

Non-stimulated guinea-pig pulmonary macrophages (PM) convert arachidonic acid to thromboxane B2 and 12-hydroxy-heptadecatrienoic acid, whereas linoleic acid is metabolized to two hydroxy compounds, i.e. 9-hydroxy- and 13-hydroxy-octadecadienoic acid. Coincubation of PM with immune serum (2% v/v) resulted in a profound reduction of the release of these products. This effect seemed to be due to an inhibitory action on cyclooxygenase activity. Control serum also possessed inhibitory properties towards the release of fatty acid metabolites, possibly due to an effect on phospholipase activity. Because of the radical scavenging properties of 9-hydroxy-octadecadienoic acid, the modulation of the release of this product may be an important determinant in macrophage function.

Animals↗
PubMed2006

Mutagenesis of rat acyl-CoA synthetase 4 indicates amino acids that contribute to fatty acid binding.

Although each of the five mammalian long-chain acyl-CoA synthetases (ACSL) can bind saturated and unsaturated fatty acids ranging from 12 to 22 carbons, ACSL4 prefers longer chain polyunsaturated fatty acids. In order to gain a better understanding of ACSL4 fatty acid binding, we based a mutagenesis approach on sequence alignments related to ttLC-FACS crystallized from Thermus thermophilus HB8. Four residues selected for mutagenesis corresponded to residues in ttLC-FACS that comprise the fatty acid binding pocket; the fifth residue aligned with a region thought to be involved in fatty acid selectivity of the Escherichia coli acyl-CoA synthetase, FadD. Changing an amino acid at the entry of the putative fatty acid binding pocket, G401L, resulted in an inactive enzyme. Mutating a residue near the pocket entry, L399M, did not significantly alter enzyme activity, but mutating a residue at the hydrophobic terminus of the pocket, S291Y, altered ACSL4's preference for 20:5 and 22:6 and increased its apparent K(m) for ATP. Mutating a site in a region previously identified as important for fatty acid binding also altered activation of 20:4 and 20:5. These studies suggested that the preference of ACSL4 for long-chain polyunsaturated fatty acids can be modified by altering specific amino acid residues.

Amino Acid Sequence↗
PubMed1983

The effect of aromatic CoA esters on fatty acid synthetase: biosynthesis of omega-phenyl fatty acids.

Aromatic carboxylic acids ingested by, or formed in, the body can be converted to the CoA derivatives but the possible metabolic fate of these thioesters has not been investigated extensively. We have examined the effects of two such thioesters, benzoyl-CoA and phenylacetyl-CoA, on the mammalian fatty acid synthetase. Benzoyl-CoA inhibited the enzyme, apparently by competing with acetyl-CoA and malonyl-CoA for substrate binding sites. Phenylacetyl-CoA, on the other hand, could replace acetyl-CoA as a primer for the fatty acid synthetase reaction; the product was almost exclusively omega-phenyldodecanoic acid. The Km of the synthetase for phenylacetyl-CoA was considerably higher than that for acetyl-CoA and the rate of synthesis of omega-phenyldodecanoic acid was only 16% of that of palmitic acid. Experiments in which the rate of synthesis and release of omega-phenyl moieties from the synthetase was compared with that of n-aliphatic moieties indicated that the rate limiting step was the initiation of chain growth from phenylacetyl-CoA; release of the synthesized acyl moieties by chain terminating thioesterases was equally rapid in the case of omega-phenyl and n-aliphatic acids. Possible metabolic consequences of the effects of these aromatic CoA esters on lipogenesis are discussed.

Acetyl Coenzyme A↗
PubMed2006

Identification of bifunctional delta12/omega3 fatty acid desaturases for improving the ratio of omega3 to omega6 fatty acids in microbes and plants.

We report the identification of bifunctional Delta12/omega3 desaturases from Fusarium moniliforme, Fusarium graminearum, and Magnaporthe grisea. The bifunctional activity of these desaturases distinguishes them from all known Delta12 or omega3 fatty acid desaturases. The omega3 desaturase activity of these enzymes also shows a broad omega6 fatty acid substrate specificity by their ability to convert linoleic acid (LA), gamma-linolenic acid, di-homo-gamma-linolenic acid, and arachidonic acid to the omega3 fatty acids, alpha-linolenic acid (ALA), stearidonic acid, eicosatetraenoic acid, and eicosapentaenoic acid (EPA), respectively. Phylogenetic analysis suggests that omega3 desaturases arose by independent gene duplication events from a Delta12 desaturase ancestor. Expression of F. moniliforme Delta12/omega3 desaturase resulted in high ALA content in both Yarrowia lipolytica, an oleaginous yeast naturally deficient in omega3 desaturation, and soybean. In soybean, seed-specific expression resulted in 70.9 weight percent of total fatty acid (%TFA) ALA in a transformed seed compared with 10.9%TFA in a null segregant seed and 53.2%TFA in the current best source of ALA, linseed oil. The ALA/LA ratio in transformed seed was 22.3, a 110- and 7-fold improvement over the null segregant seed and linseed oil, respectively. Thus, these desaturases have potential for producing nutritionally desirable omega3 long-chain polyunsaturated fatty acids, such as EPA, with a significantly improved ratio of omega3/omega6 long-chain polyunsaturated fatty acids in both oilseeds and oleaginous microbes.

Bacteria↗
PubMed1999

Variability in the trans fatty acid content of foods within a food category: implications for estimation of dietary trans fatty acid intakes.

OBJECTIVE: Currently, the published information on trans fatty acid composition of foods is incomplete and of questionable accuracy. Detailed fatty acid analysis of over 200 foods was undertaken for the purpose of determining the variability in trans fatty acid content among foods within a product category, and the significance of this variability to the estimation of trans fatty acids intakes from analysis of dietary intake data. METHODS: The analysis of food fatty acids used gas-liquid chromatography with 100 m capillary columns and standardized methodologies for food sampling, fat extraction, separation and quantification of trans fatty acid isomers. For the purposes of this report, trans refers to all non-naturally occurring isomers including trans, cis-trans, geometric and positional isomers. RESULTS: The results show that the amount of trans fatty acids varies considerably among foods within a category, reflecting differences in the fats and oils used in the manufacturing or preparation process. For example, the range of trans fatty acids in 17 brands of crackers was 23 to 51% total fatty acids, representing differences of from 1 to 13 g trans fatty acids per 100 g cracker. The large errors that may arise in estimates of the trans fatty acid intake of an individual are illustrated by analyses of the potential trans fatty acid intake in a sample diet, for each food as calculated using the minimum and maximum values for trans fatty acids within a given category. The results of these analyses show estimates of trans fatty acid intake from a low of 1.4 to 25.4 g a day for the same diet. CONCLUSION: This study shows that the wide variability in trans fatty acid content of different foods may result in large errors in the estimation of trans fatty acid intake of individuals and, potentially, groups.

Canada↗
PubMed1991

Bile acid and phospholipid fatty acid composition in bile of patients with cholesterol and pigment gallstones.

It has been previously reported that patients with cholesterol gallstones have increased biliary deoxycholate and arachidonate content as compared with normal subjects without gallstones. Increased biliary deoxycholate and arachidonate content might be a primary factor in the pathogenesis of cholesterol gallstones or merely an epiphenomenon due to the presence of gallstones. We therefore compared biliary bile acid composition in 46 patients with cholesterol gallstones and 22 patients with pigment stones. In addition, biliary phospholipid fatty acid composition was determined in 44 of these patients (30 cholesterol and 14 pigment stone patients). No significant differences were detected. In particular, the percentage deoxycholic acid (mean +/- SD: 20.3 +/- 8.8% and 21.5 +/- 10.9% respectively) and the percentage arachidonic acid (4.4 +/- 2.0% and 4.5 +/- 2.2%, respectively) were very similar. A significant correlation between age and biliary cholesterol saturation index was found only for the group of patients with pigment stones (R = 0.52, p less than 0.02). In conclusion, the present study does not support a primary role for increased biliary deoxycholic acid or arachidonic acid in the pathogenesis of cholesterol gallstones.

Arachidonic Acid↗
PubMed2005

Lead exposure and (n-3) fatty acid deficiency during rat neonatal development alter liver, plasma, and brain polyunsaturated fatty acid composition.

Lead (Pb) exposure has been reported to increase arachidonic (AA) and docosahexaenoic (DHA) acids. To determine whether Pb effects on fatty acid composition are influenced by dietary (n-3) fatty acid restriction, weanling female rats were fed either an (n-3)-adequate or -deficient diet to maturity and mated. At parturition, dams in each group were subdivided to receive either 0.2% Pb or Na-acetate in their drinking water during lactation only. Pups were analyzed for fatty acid content in liver, plasma, and brain at either 3 or 11 wk. The (n-3)-deficient diets markedly decreased total (n-3) fatty acids, and increased total (n-6) fatty acids including both AA and docosapentaenoic (n-6) in each compartment (P < 0.05). The main effects of Pb were in the livers of weanling rats where there was a 56% loss in total fatty acid concentration concurrent with increased relative percentages of AA and DHA. Thus, because there was a greater percentage of liver nonessential fatty acid lost relative to the essential fatty acids (EFA), there was no net change in AA concentration. There was a diet x Pb interaction for a decrease in liver DHA concentration evident only in the (n-3)-adequate group. There were also diet x Pb interactions in plasma at 11 wk and in brain at 3 wk. These data are consistent with the hypothesis of a Pb-induced increase in fatty acid catabolism, perhaps as a source of energy.

Animals↗
PubMed1996

The Canadian Society for Nutritional Sciences 1995 Young Scientist Award Lecture. Recent studies on the synthesis, beta-oxidation, and deficiency of linoleate and alpha-linolenate: are essential fatty acids more aptly named indispensable or conditionally dispensable fatty acids?

Recent research on the synthesis, beta-oxidation, and deficiency of linoleate and alpha-linolenate raises questions about whether the term essential fatty acid is outdated. Linoleate and alpha-linolenate can be synthesized from their respective 16-carbon precursors, which are present in the human diet; whether the rate of conversion and dietary supply of the precursors are sufficient depends on the actual requirement for linoleate and alpha-linolenate. Pure deficiency of linoleate (diet excluding linoleate but including alpha-linolenate and oleate) has not been studied until recently, so it is unclear whether the recommended linoleate intake at 2% of energy, as based on classical essential fatty acid deficiency studies, is appropriate or too high. Despite marked whole-body depletion of linoleate and poor conservation of linoleate stores, pure linoleate deficiency has little effect on growth in rats, suggesting its requirement may be less than 2% of energy. Whole-body fatty acid balance studies indicate that the main route of linoleate and alpha-linolenate metabolism is oxidation, which increases sufficiently that accumulation of dietary linoleate and alpha-linolenate may actually be prevented in undernutrition and fasting refeeding. Part of the oxidized carbon from linoleate and alpha-linolenate is recycled and used for de novo synthesis of "non-essential" fatty acids and cholesterol, which in the brain of the suckling rat, can exceed conversion to longer chain polyunsaturates by as much as 10- to 40-fold. Given the capability to synthesize linoleate and alpha-linolenate, the imprecise knowledge of true linoleate requirement, and the absence of clear symptoms of their deficiency in healthy adults, it might be advantageous to consider using the terms indispensable and conditionally dispensable to clarify the conditional nature of the dietary requirement for linoleate and alpha-linolenate.

Animals↗
PubMed2004

Rumen odd and branched chain fatty acids in relation to in vitro rumen volatile fatty acid productions and dietary characteristics of incubated substrates.

A first aim of this batch in vitro experiment (21 h) was to use changes in odd and branched chain fatty acid (OBCFA) patterns to suggest shifts in microbial populations, associated with four types of incubated whole dairy cow diets. Principal component analysis suggested higher dietary starch increased the proportion of C15:0 and C17:0, whereas increased neutral detergent fibre content was positively related to anteiso C15:0 concentrations, which is in agreement with the importance of these fatty acids in respectively amylolytic and cellulolytic bacteria. A second aim of the experiment was to relate rumen volatile fatty acid proportions to OBCFA by principal component regression and to compare these relations with predictions based on diet proximate composition. The R2 values achieved for the regressions between acetate, propionate and butyrate, and OBCFA were 79.6%, 86.6% and 84.9% respectively. Moreover, in the current study, predictions of the rumen fermentation pattern showed higher R2 (p < 0.01) when based on OBCFA compared with proximate feed composition. If relations persist in vivo, there could be scope for milk OBCFA to predict the supply of specific rumen nutrients.

Animal Feed↗
PubMed1998

Use of deuterium oxide to measure de novo fatty acid synthesis in normal subjects consuming different dietary fatty acid composition1.

The effect of dietary linoleic (C18:2n-6) and palmitic acids (C16:0) on rate of hepatic de novo fatty acid synthesis was assessed in normal subjects. The diet was formulated to provide combinations of high and low levels of C18:2n-6 and C16:0. After 21 days of diet treatment, plasma triacylglycerol level and incorporation of deuterium into the plasma very low density lipoprotein triacylglycerol (VLDL-TG) pool over 24 hours was measured. Plasma triacylglycerol levels were within the normal range. Increasing dietary intake of linoleic acid decreased plasma triacylglycerol level when subjects consumed a low level of dietary palmitic acid. The relative and net amount of de novo synthesized fatty acid in the plasma VLDL-TG pool was not influenced by the diet treatments. A relationship between plasma triacylglycerol level and rate of hepatic de novo fatty acid synthesis was observed.

Adult↗
PubMedDate not supplied

Fatty acid oxidation capacity and fatty acid-binding protein content of different cell types isolated from rat heart.

Heart tissue contains appreciable amounts of fatty acid-binding protein (FABP). FABP is thought to play a crucial role in the transport of fatty acids from the cellular membrane to the intracellular site of oxidation and also, in case of endothelial cells, in the transfer of fatty acids from the vascular to the interstitial compartment through the endothelial cytoplasm. The present study was designed to delineate a possible quantitative relationship between the capacity of different cell types in the heart to oxidize fatty acids and the presence of FABP. Palmitate oxidation capacity, measured in homogenates of cells isolated from adult rat hearts, was 2 nmol/min per mg tissue protein in freshly isolated cardiomyocytes (CMC), but only 0.09 and 0.31 nmol/min per mg tissue protein in cultivated endothelial (CEC) and fibroblast-like cells (CFLC), respectively. Palmitate oxidation rates were closely related to the cytochrome C oxidase activity and, hence, to the mitochondrial density in the cells under investigation. In CMC the content of cytosolic H-FABP (H-FABPc) was about 4.5 micrograms/mg tissue protein. However, in CEC and CFLC the FABP content was less than 0.01 and 0.004 micrograms/mg tissue protein, respectively, corresponding to at maximum 0.2% of the FABP content of CMC. These findings indicate a marked difference between CMC and non-myocytal cells in the heart regarding their capacity to oxidize fatty acids, and a marked disproportion between the fatty acid oxidation capacity and immunochemically determined FABP content in both CEC and CFLC. The functional implication of these observations remains to be elucidated.

Animals↗
PubMed1985

Selective killing of human cancer cells by polyunsaturated fatty acids.

Polyunsaturated fatty acids killed incubated human breast, lung and prostate cancer cells at concentrations which had no adverse effects on normal human fibroblasts or on normal animal cell lines. The most consistent and selective effects were obtained with fatty acids containing 3, 4 and 5 double bonds. When human cancer cells and normal human fibroblasts were co-cultured in the absence of polyunsaturated fatty acids, the malignant cells overgrew the normal ones. When eicosapentaenoic acid (EPA, 20:5n-3), gamma-linolenic acid (GLA, 18:3n-6) or arachidonic acid (AA, 20:4n-6) were added to the co-cultures, the normal cells outgrew the malignant ones. These observations suggest that treatment of malignancy with polyunsaturated fatty acids may have considerable potential while being associated with a high level of safety.

Animals↗