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PubMed1989

Changes of linoleic acid metabolism and cellular phospholipid fatty acid composition in LLC-PK cells cultured at low magnesium concentrations.

LLC-PK cells grown on media containing normal (480 microM) or reduced magnesium levels (25, 6.3 or 2.5 microM) were used to study the effect of magnesium deficiency on linoleic acid metabolism and cellular membrane fatty acids. The fatty acid composition of the cellular phospholipids showed a significant decrease in 20:4(n-6) and 22:4(n-6) acids and a significant increase in 18:2(n-6), 18:3(n-6) and 20:3(n-6) fatty acids in magnesium-deficient cells compared to magnesium-sufficient cells. When [1-14C]linoleic acid was incubated with control (480 microM Mg2+) or magnesium deficient cells (2.6 microM Mg2+) the rate of tetraenoic acid synthesis (20:4(n-6) + 22:4(n-6) was significantly reduced in magnesium-deficient cells, indicating that the metabolic conversion of 18:2(n-6) to 20:4(n-6) is impaired in magnesium deficiency. This reduction in conversion may be due to the impairment of either the delta(5)- or the delta(6)-desaturase, or both. This study shows that magnesium deficiency perturbs essential fatty acid (EFA) metabolism and decreases the cellular membrane polyunsaturated fatty acid (PUFA) content. These alterations are likely to have adverse effects on cellular membrane properties and functions.

Animals↗
PubMed1979

The influence of linoleic acid intake on the excretion of urinary prostaglandin metabolites.

The influence of linoleic acid intake on human prostaglandin formation was investigated by gas chromatographic determination of dimethyl tetranorprostanedioate, a derivative of the major urinary end products of prostaglandin metabolism. Six healthy female volunteers were put on liquid formula diets. Each person had a linoleic acid supply of 0, 10, and 50 g per day for periods of two weeks. At the end of these periods the corresponding average amounts of tetranorprostanedioic acid in urine were 92, 175, and 326 microgram per day.

Adult↗
PubMed1994

Conjugated linoleic acid is a growth factor for rats as shown by enhanced weight gain and improved feed efficiency.

We studied the effect of conjugated linoleic acid (CLA) on rat development and growth. Primigravid female Fischer rats were fed control or CLA-supplemented (0.25% or 0.5% CLA) diets during gestation and/or lactation. Conjugated linoleic acid was incorporated into milk fat and tissue lipids proportional to the level of CLA fed and the duration of CLA feeding. Conjugated linoleic acid was incorporated into fetal and neonatal tissues; it did not affect litter size nor induce apparent abnormalities. To the contrary, feeding CLA to the dams during gestation and lactation improved the postnatal body weight gain of pups (P < 0.05), measured on d 10 of lactation. Pups that continued to receive the CLA-supplemented diet after weaning had significantly greater body weight gain and improved feed efficiency relative to control animals (P < 0.05).

Animals↗
PubMed1986

A Comparison of Oleic Acid Metabolism in the Soybean (Glycine max [L.] Merr.) Genotypes Williams and A5, a Mutant with Decreased Linoleic Acid in the Seed.

The metabolism of oleoyl coenzyme A (CoA) was examined in developing seed from two soybean (Glycine max [L.] Merr.) genotypes: Williams, a standard cultivar and A5, a mutant containing nearly twice the oleic acid (18:1) content of Williams. The in vitro rates of esterification of oleoyl-CoA to lysophosphatides by acyl-CoA: lysophosphatidylcholine acyltransferase was similar in both genotypes and lysophosphatidyl-ethanolamine was a poor substrate. Crude extracts desaturated exogenous [1-(14)C]dioleoyl phosphatidylcholine at 14% of the rate achieved with [1-(14)C]oleoyl-CoA, and 50 micromolar lysophosphatidylcholine. The desaturase enzyme also required NADH for full activity. Extracts from Williams contained 1.5-fold more oleoyl phosphatidylcholine desaturase activity, on a fresh weight basis, than did A5 and appeared to have a similar affinity for oleoyl-CoA. There was 1.2- to 1.9-fold more linoleic acid (18:2) in phosphatidylcholine from Williams than from A5, measured at two stages of development, but both genotypes had a similar distribution of fatty acids in the one and two positions. Phosphatidylethanolamine in A5 contained relatively more linoleic acid (18:2) in the one position than did Williams. The increased oleic acid (18:1) content in A5 appeared to be a result of decreased rates of 18:1 desaturation of oleoyl-phosphatidylcholine in this genotype.

Journal Article↗
PubMed1983

Effect of variations in fat and linoleic acid intake on the calcium, magnesium and iron balance of young men.

In one study a group of 10 young adult male volunteers were given two experimental diets, differing in fat content. In a second study another group of 12 such volunteers received two experimental diets differing in linoleic acid content. The retention of calcium, magnesium and iron was measured during the dietary periods, each lasting 1 month. Decreasing the fat intake from 42 to 22 energy % did not result in statistically significant changes of the mineral balance. An increase in linoleic acid intake from 4 to 16 energy % (at a constant level of fat intake of 42 energy %) caused a decrease in the iron balance from 3.3 to 2.3 mg/day (p less than 0.01), while the calcium and magnesium retention did not change significantly. During the high linoleic acid dietary period haemoglobin levels decreased from 9.6 to 9.1 mmol/1 and packed cell volume from 0.48 to 0.46 1/1 (p less than 0.001). This effect of linoleic acid on iron utilization needs further investigation.

Adult↗
PubMed2005

Effect of diets containing linoleic acid- or oleic acid-rich oils on ruminal fermentation and nutrient digestibility, and performance and fatty acid composition of adipose and muscle tissues of finishing cattle.

Two trials were conducted to determine the effect of linoleic acid- or oleic acid-rich safflower oil on ruminal fermentation, nutrient digestion, feedlot performance, carcass characteristics, and fatty acid composition of adipose and muscle tissues of beef cattle. In both trials, cattle were fed a finishing diet based on barley grain, wheat silage, and alfalfa hay. Oils were fed at 5% of dietary DM. In a metabolism trial, four ruminally and duodenally cannulated Angus crossbred steers were subjected to linoleic acid-rich oil or oleic acid-rich oil in a crossover design with covariate periods (no oil supplementation). In a finishing trial, 16 individually fed Angus crossbred steers and heifers (eight per diet) received linoleic acid- or oleic acid-rich oils during the last 86 d of a 116-d feeding period. Ruminal pH, ammonia concentration, protozoal counts, major VFA concentrations, acetate-to-propionate ratio, polysaccharide-degrading activities, microbial N flow to the duodenum, and the efficiency of microbial N synthesis in the rumen were not affected (P = 0.18 to 0.96) by type of oil. Type of oil had no effect on total-tract apparent digestion of nutrients (P = 0.46 to 0.98). Ruminal true nutrient digestibilities did not differ between oils (P = 0.15 to 0.99), except that the linoleic acid-rich oil decreased (P = 0.05) NDF digestibility. Dry matter intake, ADG, G:F, and carcass characteristics did not differ (P = 0.11 to 0.84) between the two oils. Overall, the difference in dietary fatty acids provided to the cattle produced few changes in tissue fatty acids. Weight percentages of c9t11 CLA were unaltered by the addition of linoleic acid to the diet compared with oleic acid, probably as a result of low vaccenic acid production in the rumen, as the pathway of biohydrogenation was apparently primarily through the t10 pathway.

Adipose Tissue↗
PubMed2001

Distribution of conjugated linoleic acid and metabolites in different lipid fractions in the rat liver.

Conjugated linoleic acid (CLA) is known to provide certain health benefits in experimental animal models. The major CLA isomer in food is c 9,t11-CLA. A primary objective of this study was to investigate the uptake of c 9,t11-CLA and its downstream metabolites into various lipid fractions in the liver of rats fed either a high or low CLA diet (containing 0.1 or 0.8 g CLA/100 g diet, respectively). As expected, the levels of all conjugated diene (CD) fatty acids (CD 18:2 + CD 18:3 + CD 20:3 + CD 20:4) were elevated about 8-fold in the high CLA diet group. However, there was no change in the distribution of CLA and CLA metabolites into various lipid fractions due to CLA intake. Unlike linoleic acid or gamma-linolenic acid, which were distributed mainly in phospholipids, CD 18:2, CD 18:3, and CD 20:3 were incorporated primarily in neutral lipid. Furthermore, the incorporation of all nonconjugated unsaturated fatty acids was not perturbed by CLA. Regardless of the level of CLA in the diet, CD 20:4 was predominantly enriched in phosphatidylserine and phosphatidylinositol. In contrast, arachidonic acid was primarily enriched in phosphatidylcholine and less so in phosphatidylethanolamine. The above findings may have potential implication regarding the role of CLA in modulating eicosanoid metabolism.

Animal Feed↗
PubMed1999

Rapid reversed-phase high-performance liquid chromatographic determination of the regiospecificity of lipoxygenase products on linoleic acid.

A new reversed-phase high-performance liquid chromatography method for the separation of regioisomeric products from lipoxygenase acting on linoleic acid was studied. The addition of salts to the mobile phase improved the retention and separation behaviour of 13-hydroperoxy-9,11-octadecadienoic acid and 9-hydroperoxy-10,12-octadecadienoic acid with respect to the results obtained with other mobile phases reported in the literature. The effect of the pH and ionic strength of the buffer on the retention times, capacity factor and separation factor of these lipoxygenase products were also studied. The pH optimum coincided with the pKa of linoleic acid (close to 7 depending on the fatty acid concentration). Phosphate concentrations close to 100 mM considerably reduced the retention times and led to better separation of the mixture of both products. Finally, this method was applied to the identification and separation of two linoleic acid hydroxides (13-hydroxy-9,11-octadecadienoic acid and 9-hydroxy-10,12-octadecadienoic acid) obtained by the reduction of their corresponding hydroperoxides.

Buffers↗
PubMed2001

Identification of a Saccharomyces cerevisiae gene that is required for G1 arrest in response to the lipid oxidation product linoleic acid hydroperoxide.

Reactive oxygen species cause damage to all of the major cellular constituents, including peroxidation of lipids. Previous studies have revealed that oxidative stress, including exposure to oxidation products, affects the progression of cells through the cell division cycle. This study examined the effect of linoleic acid hydroperoxide, a lipid peroxidation product, on the yeast cell cycle. Treatment with this peroxide led to accumulation of unbudded cells in asynchronous populations, together with a budding and replication delay in synchronous ones. This observed modulation of G1 progression could be distinguished from the lethal effects of the treatment and may have been due to a checkpoint mechanism, analogous to that known to be involved in effecting cell cycle arrest in response to DNA damage. By examining several mutants sensitive to linoleic acid hydroperoxide, the YNL099c open reading frame was found to be required for the arrest. This gene (designated OCA1) encodes a putative protein tyrosine phosphatase of previously unknown function. Cells lacking OCA1 did not accumulate in G1 on treatment with linoleic acid hydroperoxide, nor did they show a budding, replication, or Start delay in synchronous cultures. Although not essential for adaptation or immediate cellular survival, OCA1 was required for growth in the presence of linoleic acid hydroperoxide, thus indicating that it may function in linking growth, stress responses, and the cell cycle. Identification of OCA1 establishes cell cycle arrest as an actively regulated response to oxidative stress and will enable further elucidation of oxidative stress-responsive signaling pathways in yeast.

Amino Acid Sequence↗
PubMedDate not supplied

[Free radical oxidation of biological membrane lipids. IV. iron salts in peroxidation catalysis of linoleic acid].

The validity of Nernst law for oxidative-reductive pair Fe3+:Fe2+ and absence of reproducible potential for pure solution of linoleic acid is shown. The value of Eo is calculated. It is found by comparing ORP values and spectrophotometrically measured concentrations of hydroperoxides that: 1) the rate of accumulation of hydroperoxides is determined by the initial concentration bivalent ferrum salt and seems not to depend on the kinetics of further change of ORP in the system; 2) during oxidation of linoleic acid the stationary concentration of Fe3+:Fe2+=40:1 is established which is independent of the initial concentration of ferrum ions; 3) ORP zone necessary for maximum rate of catalysis of free radical oxidation of linoleic acid in methanol lies in a more positive region than normal ORP of the pair Fe3+:Fe2+.

Catalysis↗
PubMed2004

Prolonged feeding of mice with conjugated linoleic acid increases hepatic fatty acid synthesis relative to oxidation.

Feeding mice conjugated linoleic acid (9 cis,11 trans/9 trans,11 cis-and 10 trans,12 cis-CLA in equal amounts) resulted in triacylglycerol accumulation in the liver. The objective of this study was to examine whether this steatosis is associated with changes in hepatic fatty acid synthesis and oxidation. Therefore, we measured the activities of key enzymes of fatty acid synthesis, i.e., acetyl-CoA carboxylase and fatty acid synthase and of fatty acid oxidation, i.e., 3-hydroxy-acyl-CoA dehydrogenase and citrate synthase in livers of mice fed a diet with 0.5% (w/w) CLA. CLA (a 1:1 mixture of the 10 trans, 12 cis and 9 cis, 11 trans isomers of octadecadenoic acid) was administered for 3 and 12 weeks with high-oleic sunflower oil fed as control. The proportion of body fat was significantly lower on the CLA than on the control diet and this effect was already significant after 3 weeks. The specific activites of 3-hydroxy-acyl-CoA dehydrogenase and citrate synthase were unaffected by CLA both after 3 and 12 weeks. The specific activity of fatty acid synthase was nonsignificantly raised (by 12%) after 3 weeks on the CLA diet but had increased significantly (by 34%) after 12 weeks of feeding. The specific activity of acetyl-CoA carboxylase had also increased both after 3 weeks (by 53%) and 12 weeks (by 23%) on the CLA diet, but this effect did not reach statistical significance. Due to CLA-induced hepatomegaly, the overall capacity for both fatty acid oxidation and synthesis-as evidenced by the total hepatic activities of 3-hydroxy-acyl-CoA dehydrogenase, citrate synthase, acetyl-CoA carboxylase, and fatty acid synthase-was significantly greater in the CLA-fed group after 12 weeks, although the overall capacity for fatty acid synthesis had increased more than that for fatty acid oxidation. Thus, this study indicates that prolonged, but not short-term, feeding mice with CLA increased hepatic fatty acid synthesis relative to oxidation, despite the decrease in body fat and the increase in liver weight seen earlier. It is concluded that the observed CLA-induced changes in hepatic fatty acid synthesis and oxidation are the result, rather than the cause, of the lowering of body fat.

Animals↗
PubMed2002

Conjugation of the linoleic acid oxidation product, 13-oxooctadeca-9,11-dienoic acid, a bioactive endogenous substrate for mammalian glutathione transferase.

The oxidation of linoleic acid leads to the generation of several products with biological activity, including 13-oxooctadeca-9,11-dienoic acid (13-OXO), a bioactive 2,4-dienone that has been linked to cell differentiation. In the current work, the conjugation of 13-OXO by human glutathione transferases (GSTs) of the alpha (A1-1, A4-4), mu (M1-1, M2-2) and pi (the allelic variants P1-1/ile, and P1-1/val) classes, and a rat theta (rT2-2) class enzyme has been evaluated. The kinetics and stereoselectivity of the production of the 13-OXO-glutathione conjugate (13-OXO-SG) have been examined. In contrast to many xenobiotic substrates, the endogenous substrate 13-OXO does not exhibit an appreciable non-enzymatic rate of conjugation under physiological conditions. Therefore, the GST-catalyzed conjugation takes on greater significance as it provides the only realistic means for formation of 13-OXO-SG in most biological systems. Alpha class enzymes are most efficient at catalyzing the formation of 13-OXO-SG with kcat/Km values of 8.9 mM(-1) s(-1) for GST A1-1 and 2.14 mM(-1) s(-1) for GST A4-4. In comparison, enzymes from the mu and pi classes exhibit specificity constants from 0.4 to 0.8 mM(-1) s(-1). Conjugation of 13-OXO with glutathione at C-9 of the substrate can yield a pair of diastereomers that can be resolved by chiral HPLC. GSTs from the mu and pi classes are the most stereoselective enzymes and there is no apparent relationship between catalytic efficiency and stereoselectivity. The role of GST in the metabolic disposition of the bioactive oxidation products of linoleic acid has implications for the regulation of normal cellular functions by these versatile enzymes.

Animals↗
PubMed1989

Augmentation of donor-specific transfusion and cyclosporine effects with dietary linoleic acid.

Increased prostaglandin production is a possible mechanism for the immunosuppressive effects of both cyclosporine and blood transfusions. Therefore, dietary supplementation with linoleic acid, a prostaglandin precursor, combined with either modality could act synergistically. Intraabdominal cardiac allografts were performed from Buffalo rat donors to Lewis recipients. Transplant recipients received a single donor-specific transfusion, low-dose cyclosporine (CsA, 1 mg/kd/d x 7 days), dietary supplementation with linoleic acid (LA, 16% of total calories) or a combination of the three modalities. CsA, DST or LA alone significantly prolonged allograft survival. Both CsA and LA acted synergistically with DST in further prolongation of survival--however, animals receiving all three modalities achieved 100% long-term survival. Augmentation of transfusion- and cyclosporine-induced immunosuppression with dietary prostaglandin precursor is possible.

Animals↗
PubMed1991

Linoleic acid lowers LDL cholesterol without a proportionate displacement of saturated fatty acid.

We tested the specificity of the plasma cholesterol-lowering effect of linoleic acid in a comparison of linoleate-rich and saturated fatty acid-rich foods. Twelve mildly hypercholesterolemic men and women ate the two diets for three weeks each in a random cross-over design, after a two-week baseline period. A linoleic acid-rich supplement was added to the baseline diet so that the saturated and monounsaturated fatty acid content did not change significantly. Despite the consequent increase in total fat intake, the linoleate-rich diet (23 per cent energy from polyunsaturated fatty acids) significantly lowered plasma total and low-density lipoprotein (LDL) cholesterol (-8 per cent and -14 per cent respectively), while high-density lipoprotein (HDL) cholesterol rose 8 per cent. The direction of these changes was similar in all 12 subjects. Compared with a supplement that raised dietary saturated fatty acids to 30 per cent energy, the linoleate acid-rich diet gave lower total cholesterol (-14 per cent), LDL cholesterol (-18 per cent) and HDL cholesterol (-12 per cent) concentrations. Linoleic acid lowers LDL cholesterol even when saturated fatty acids are not significantly displaced and substantially more when there is such displacement.

Adult↗
PubMed1986

Influence of the linoleic acid content of the diet on tumor growth in transplantable rat tumor models.

Diets high (17.7 cal%) and low (3.3 cal%) in linoleic acid were given to groups of Brown Norway female rats before and after inoculation of syngeneic tumor models with different characteristics, with regard to tumor spread, malignancy, immunogenicity, growth rate, rat strain, and histopathological features. Despite the differences in characteristics, in most tumor models, tumor growth was identical in both experimental groups. However, in 2 tumor models, an adrenal cortical carcinoma and a myeloid leukemia, differences in growth were noted. In rats given the diet low in linoleic acid, growth of the cortical carcinoma was significantly increased, whereas the opposite effect was seen in rats with myeloid leukemia.

Animals↗