Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “LINOLEIC ACID”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,351 records · Page 75Linked to original sources
PubMed1992

Inhibition of 2-amino-3-methylimidazo[4,5-f]quinoline-DNA adduct formation in CDF1 mice by heat-altered derivatives of linoleic acid.

Grilled ground beef contains a number of carcinogens, including aminoimidazoazaarenes, such as 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), as well as anticarcinogenic substances, such as heat-generated derivatives of linoleic acid (CLA). In the present study, CLA was administered by gavage every other day to young adult CDF1 mice for a period of 45 days (50 microliters/48 hr for days 1-24 and 100 microliters/48 hr for days 25-45), using trioctanoin as a control. On day 46 all animals received a single oral dose (50 mg/kg) of IQ and tissues were collected 24 hr later. Tissue DNA was purified and analysed for IQ-DNA adducts by 32P-postlabelling assays. Compared with controls, CLA treatment caused a 43.1 and 31.8% inhibition of adduct formation in the livers of male and female mice, respectively. In the lung and large intestine CLA had a 74.2 and 39.4% inhibitory effect, respectively, in the female only, whereas there was no effect in the stomach or small intestine of either sex. In the kidneys of females, CLA treatment inhibited IQ-DNA adduct formation almost completely (95.2%), whereas in the kidneys of males CLA had no effect. It is concluded that CLA inhibits IQ-DNA adduct formation in certain IQ target organs (liver and lung) and non-target organs (large intestine, kidney), but is inactive in other target organs (stomach) and non-target organs (small intestine) of the CDF1 mouse.

Administration, Oral↗
PubMed1978

Linoleic acid effects on epidermal DNA synthesis and cutaneous prostaglandin levels in essential fatty acid deficiency.

An essential fatty acid (EFA) deficient state has been induced in hairless mice. The epidermal changes included hyperkeratosis, hypergranulosis and acanthosis. Epidermal DNA synthesis was increased 3-fold compared with normal diet mice. Prostaglandin E (PGE) and prostaglandin F (PGF) levels, measured by radioimmunoassay, were much reduced in the EFA deficient mice skin. 10% Linoleic acid applied topically for 2 weeks corrected the gross and histological skin abnormalities and reduced epidermal DNA synthesis to normal values. The levels of PGE and PGF were only partially corrected. Linoleic acid applied to normal diet mice increased skin levels of PGE and PGF compared with the control vehicle treated normal diet mice. These results provide further evidence for the importance of essential fatty acids in the control of epidermal proliferation and differentiation. The importance of PGE and PGF in controlling epidermal DNA synthesis in EFA deficiency is less clear.

Animals↗
PubMed1998

Linoleic acid peroxidation--the dominant lipid peroxidation process in low density lipoprotein--and its relationship to chronic diseases.

Modern separation and identification methods enable detailed insight in lipid peroxidation (LPO) processes. The following deductions can be made: (1) Cell injury activates enzymes: lipoxygenases generate lipid hydroperoxides (LOOHs), proteases liberate Fe ions--these two processes are prerequisites to produce radicals. (2) Radicals attack any activated CH2-group of polyunsaturated fatty acids (PUFAs) with about a similar probability. Since linoleic acid (LA) is the most abundant PUFA in mammals, its LPO products dominate. (3) LOOHs are easily reduced in biological surroundings to corresponding hydroxy acids (LOHs). LOHs derived from LA, hydroxyoctadecadienoic acids (HODEs), surmount other markers of LPO. HODEs are of high physiological relevance. (4) In some diseases characterized by inflammation or cell injury HODEs are present in low density lipoproteins (LDL) at 10-100 higher concentration, compared to LDL from healthy individuals.

Aging↗
PubMed2003

Linoleic acid and antioxidants protect against DNA damage and apoptosis induced by palmitic acid.

Polyunsaturated fats are the main target for lipid peroxidation and subsequent formation of mutagenic metabolites, but diets high in saturated fats are more strongly associated with adverse health effects. We show that the common saturated fatty acid, palmitic acid, is a potent inducer of DNA damage in an insulin-secreting cell line, and in primary human fibroblasts. Damage is not associated with upregulation of inducible nitric oxide synthase, but is prevented by two different antioxidants, alpha-lipoic acid and 3,3'-methoxysalenMn(III) (EUK134), which also partly prevent palmitic acid-induced apoptosis and growth inhibition. Since mutagenic metabolites can be formed from peroxidation of polyunsaturated fatty acids, co-administration of palmitic and a polyunsaturated fatty acid might be particularly harmful. Palmitic acid-induced DNA damage is instead prevented by linoleic acid, which is acting here as a protective agent against oxidative stress, rather than as a source of mutagenic metabolites. These results illustrate the complexity of the relationship of dietary fat intake to genotoxicity.

Antioxidants↗
PubMed2001

Conjugated linoleic acid and oxidative behaviour in cancer cells.

Convincing evidence from rodent models of carcinogenesis indicates that cis-9,trans-11 (c9t11) conjugated linoleic acid (CLA) is a potent naturally occurring anti-carcinogen in the human diet. CLA has been reported to alter the fatty acid composition of biological tissues in a manner that increases their oxidative stability. However, recent information suggests that an antioxidant role for CLA does not seem plausible. Given the knowledge that c9t11 CLA is present in a wide range of meat and dairy food products, our studies have begun to investigate mechanisms by which CLA-enriched milk fat exerts its anti-carcinogenic effects. An oxidative mechanism appears to be involved in its growth-suppressive effects, since supplementation of growth culture medium with CLA (17-71.5 microM) made breast cancer cells more susceptible to lipid peroxidation. Studies have indicated that cancer cells may become enriched in CLA during growth in culture. This may make intracellular lipids more susceptible to ordinary levels of oxidative stress, to the point of producing a cytotoxic effect.

Animals↗
PubMed2005

Combined effects of dietary protein type and fat level on the body fat-reducing activity of conjugated linoleic acid (CLA) in rats.

The interaction of dietary protein type and fat level on the body fat-reducing activity of conjugated linoleic acid (CLA) was studied in male rats fed diets containing casein (CAS) or soy protein (SOY) as a protein source with low fat (LF, 6.0% soybean oil) or high fat (HF, 13.0% soybean oil) combinations for 4 weeks. CLA was added at the 1.0% level to all diets. The weight of perirenal adipose tissue tended to be lower in the SOY groups than in the corresponding CAS groups, and the difference between the LF diets was significant. The weight of epididymal adipose tissue showed a similar but insignificant trend. The weight of brown adipose tissue was heaviest on the SOY-HF diet and lowest on two CAS diets, the SOY-LF diet being intermediate. The concentration of serum leptin was lowest on the SOY-LF diet and was significantly lower than that of the corresponding CAS group, but this difference disappeared when the dietary fat level increased. The serum cholesterol-lowering activity of SOY in relation to CAS was reproduced even when CLA was given. Thus the body fat-reducing activity of CLA was most marked when rats were fed the SOY-LF diet. Although the CAS-HF diet increased body fat deposition, the magnitude of the reduction by lowering dietary fat level was more marked than in the case of SOY. These results indicate a complicated interaction of dietary manipulations with the body fat-reducing effect of CLA, but the combination of CLA with the SOY-LF diet appears to be an appropriate approach.

Adipose Tissue↗
PubMed2001

Conjugated linoleic acid supplementation in humans: effects on fatty acid and glycerol kinetics.

Recent studies with mouse adipocytes have shown that dietary conjugated linoleic acid (CLA) may reduce body fat by increasing lipolysis. The present study examined the effect of CLA supplementation on fatty acid and glycerol kinetics in six healthy, adult women who were participating in a controlled metabolic ward study. These women were fed six CLA capsules per day (3.9 g/d) for 64 d following a baseline period of 30 d. The subjects were confined to a metabolic suite for the entire 94-d study, where diet and activity were controlled and held constant. The rate of appearance (Ra) of glycerol, which indicates lipolytic rates, was similar at baseline and after 4 wk of CLA supplementation at rest (1.87 +/- 0.21 and 2.00 +/- 0.39 micromol/kg/min, respectively) and during exercise (7.12 +/- 0.74 and 6.40 +/- 0.99 micromol/kg/min, respectively). Likewise, the Ra of free fatty acids (FFA) was not significantly different after 4 wk of dietary CLA at rest (2.72 +/- 0.06 and 2.74 +/- 0.12 micromol/kg/min, respectively) or during exercise (6.99 +/- 0.40 and 5.88 +/- 0.29 micromol/kg/min, respectively). CLA supplementation also had no effect on the percentage of FFA released from lipolysis that were re-esterified. The apparent rate of FFA re-esterification was 65.2 +/- 4.2% at rest and 32.1 +/- 3.44% during exercise. Four weeks of CLA supplementation had no significant effect on fatty acid or glycerol metabolism in healthy, weight-stable, adult women.

Adult↗
PubMed2002

Effect of dietary conjugated linoleic acids on the distribution of fatty acids in serum lipoprotein fractions and different tissues of growing pigs.

The effect of conjugated linoleic acid (CLA) on blood lipids [total cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL) and triacylglycerols (TAG)] and the fatty acid distribution of the lipoprotein fractions, backfat, muscle fat, and liver lipids were examined in an experiment with two groups of 40 pigs [Pietrain x (Landrace x Large White)] each. The 20 female and 20 male castrated pigs of each group were fed with isoenergetic and isonitrogenous diets supplemented with either 20 g/kg rapeseed oil (control) or 20 g/kg CLA-TAG. The CLA preparation contained 54.2% pure CLA consisting of approximately two-thirds cis,trans/trans,cis-isomers and one-third trans,trans-isomers. The fatty acids of lipoproteins, backfat, muscle lipids and liver lipids were analysed by gas chromatograph (GC). CLA supplementation did not significantly influence blood lipids and the LDL to HDL ratio. In the CLA-fed pigs the very low-density lipoprotein (VLDL) contained higher saturated fatty acid (SFA) concentrations at the cost of the monounsaturated fatty acids (MUFA). The percentage of polyunsaturated fatty acids (PUFA) remained unchanged. The highest CLA content was analysed in VLDL (4.00%) followed by LDL (2.78%) and HDL (1.45%). The ratio of cis,cis to trans,trans isomers increased from VLDL over LDL to HDL. The content of SFA, probably in backfat and muscle lipids, increased whereas the part of MUFA decreased as a result of reduced Delta9-desaturase activity. The percentage of PUFA (without CLA) was higher in backfat of the control group in accordance with the dietary PUFA supply. This shift in the fatty acid distribution was not observed in the liver lipids. In all the three tissues analysed, the CLA-fed pigs had a significantly increased CLA content: the highest increase was in the backfat (5.65%), followed by liver lipids (2.41%), and muscle lipids (1.47%). An isomer-specific accumulation was observed for cis,cis-CLA isomers in muscle, and for trans,trans-CLA isomers in backfat. We conclude that CLA supplementation results in a higher SFA content in backfat and muscle lipids but not in liver lipids. There is a discrimination of the trans-10, cis-12 isomer and the trans,trans isomers in the formation of the cell membranes.

Adipose Tissue↗
PubMed1999

Dietary conjugated linoleic acids alter serum IGF-I and IGF binding protein concentrations and reduce bone formation in rats fed (n-6) or (n-3) fatty acids.

A study was designed to examine the effects of dietary conjugated linoleic acid (CLA) on serum concentrations of insulin-like growth factor-I (IGF-I) and IGF binding proteins (IGFBP) and the relationship of these factors to bone metabolism. Weanling male rats were fed AIN-93G diet containing 70 g/kg of added fat for 42 days. Treatments included 0 g/kg or 10 g/kg of CLA and soybean oil (SBO) or menhaden oil + safflower oil (MSO) following a 2 x 2 factorial design. Serum IGFBP was influenced by dietary polyunsaturated fatty acid (PUFA) type ((n-6) and (n-3)) and CLA (p = 0.01 for 38-43 kDa bands corresponding to IGFBP-3). CLA increased IGFBP level in rats fed SBO (p = 0.05) but reduced it in those fed MSO (p = 0.01). Rats fed MSO had the highest serum IGFBP-3 level. Both (n-3) fatty acids and CLA lowered ex vivo prostaglandin E2 production in bone organ culture. In tibia, rats given CLA had reduced mineral apposition rate (3.69 vs. 2.79 microm/day) and bone formation rate (BFR) (0.96 vs. 0.65 microm3/microm2/day); however, the BFR tended to be higher with MSO. Dietary lipid treatments did not affect serum intact osteocalcin or bone mineral content. These results showed that dietary PUFA type and CLA modulate local factors that regulate bone metabolism.

Animals↗
PubMed2004

Melatonin uptake and growth prevention in rat hepatoma 7288CTC in response to dietary melatonin: melatonin receptor-mediated inhibition of tumor linoleic acid metabolism to the growth signaling molecule 13-hydroxyoctadecadienoic acid and the potential role of phytomelatonin.

Both physiological and pharmacological levels of the pineal hormone melatonin exhibit substantial anticancer activity in tissue-isolated rat hepatoma 7288CTC via melatonin receptor-mediated blockade of tumor uptake of linoleic acid (LA) and its metabolism to the mitogenic signaling molecule 13-hydroxyoctadecadienoic acid (13-HODE). Melatonin is also present in significant amounts in edible plants and is supplied in nutritional supplements. We confirmed the presence of significant quantities of melatonin in 20 varieties of edible plants. In pinealectomized tumor-free rats, 3 weeks of ingestion of either 5 or 50 microg/day of melatonin contained in a semi-purified diet resulted in a dose-dependent elevation in steady-state plasma melatonin levels within the nocturnal physiological range. In pineal-intact tumor-bearing rats, the daily intake of 5 microg/day of melatonin for 3 weeks resulted in an enhanced amplitude and duration of the nocturnal melatonin levels within physiological circulating limits. The nocturnal melatonin amplitude in rats ingesting 500 ng of melatonin/day remained within the physiological range. A dose-related increase in tumor concentrations of melatonin occurred in animals ingesting melatonin from the diet. Perfusion of tumors in situ with physiological, nocturnal blood levels of melatonin resulted in a mean 31% uptake and retention of the melatonin. Chronic ingestion of 50 ng, 500 ng or 5 microg of melatonin/day supplied in a semi-purified 5% corn oil diet led to a significant dose-dependent reduction in the rates of tumor total fatty acid uptake, LA uptake, 13-HODE production and tumor growth. The co-ingestion of melatonin receptor antagonist S20928 completely blocked the effects and prevented the intra-tumoral accumulation of melatonin. Melatonin receptor-mediated suppression of tumor growth, LA uptake and metabolism, and stimulation of tumor melatonin uptake and retention in response to the dietary intake of phytomelatonin from edible plants or melatonin from nutritional supplements, could play an important role in cancer growth prevention.

Animals↗
PubMed2000

Biosynthesis of conjugated linoleic acid in humans.

This paper deals with the reanalysis of serum lipids from previous studies in which deuterated fatty acids were administered to a single person. Samples were reanalyzed to determine if the deuterated fatty acids were converted to deuterium-labeled conjugated linoleic acid (CLA, 9c,11t-18:2) or other CLA isomers. We found 11-trans-octadecenoate (fed as the triglyceride) was converted (delta9 desaturase) to CLA, at a CLA enrichment of ca. 30%. The 11-cis-octadecenoate isomer was also converted to 9c,11c-18:2, but at <10% the concentration of the 11t-18:1 isomer. No evidence (within our limits of detection) for conversion of 10-cis- or 10-trans-octadecenoate to the 10,12-CLA isomers (delta12 desaturase) was found. No evidence for the conversion of 9-cis,12-cis-octadecadienoate to CLA (via isomerase enzyme) was found. Although these data come from four single human subject studies, data from some 30 similar human studies have convinced us that the existence of a metabolic pathway in one subject may be extrapolated to the normal adult population.

Deuterium↗
PubMed2006

Effect of silage type and concentrate level on conjugated linoleic acids, trans-C18:1 isomers and fat content in milk from dairy cows.

The objective of the study was to examine how the fatty acid composition of milk especially concentrations of conjugated linoleic acids (CLA) and trans-C18:1 isomers and milk fat percentage were affected by silage type and concentrate level. Forty dairy cows were blocked and randomly assigned to one of four diets in a 2 x 2 factorial arrangement of treatments and a six week experimental period. Treatments were total mixed rations with maize (M) or grass (G) silage differing in polyunsaturated fatty acid (PUFA) profile and starch content, combined with a high (H) or a low (L) level of concentrate (with or without grain). Treatments had no significant effect on milk, protein and lactose yield, but energy corrected milk yield, milk fat percentage and fat yield was lower and protein percentage higher for maize compared with grass silage diets. Overall, maize silage diets resulted in higher concentrations of CLA isomers compared with grass silage diets, but there was a significant interaction between silage type and concentrate level for concentrations of cis9,trans11-CLA; trans10,cis12-CLA; trans11-C18:1 and trans10-C18:1. A high level of concentrate increased trans10,cis12-CLA and trans10-C18:1 and reduced cis9,trans11-CLA and trans11-C18:1 when maize but not grass silage was provided. The results suggest that high levels of concentrate (grain) do not significantly alter the pattern of PUFA biohydrogenation in the rumen, the concentration of CLA and trans-C18:1 isomers in milk or cause milk fat depression unless combined with forage naturally high in starch and C18:2n-6 such as maize silage.

Animal Nutritional Physiological Phenomena↗
PubMed2003

Isomeric distribution of conjugated linoleic acids (CLA) in the tissues of layer hens fed a CLA diet.

The isomeric distribution of conjugated linoleic acids (CLA) in the tissue lipids of hens in relation to that in the diet was examined. Silver-ion high-performance liquid chromatography was used to quantify individual CLA isomers in total tissue lipids, phospholipids, and triacylglycerols. It was found that the deposition of CLA isomers in hen tissues was selective. All tissues including serum, liver, heart, kidney, abdominal fat, and leg and breast muscles had lesser amounts of total cis/trans isomers ranging from 75.87 to 89.13% of total CLA, which was in contrast to the value of 92% of total CLA in the dietary lipids. Total trans/trans isomers in all tissue lipids ranging from 6.11 to 18.02% of total CLA were greater than that in the diet (4.19%). Among the individual trans/trans isomers, all tissues except for adipose tissue and brain incorporated greater amounts of t-12,t-14-18:2, t-11,t-13-18:2,t-10,t-12-18:2, t-9,t-11-18:2, and t-18,t-10-18:2 compared with the values of the diet. Within the cis/trans group, lesser amounts of c-10,t-12/t-10,c-12-18:2 were found to incorporate into all tissues compared with the value of the diet. Serum and liver had higher percentages of c-9,t-11/t-9,c-11, whereas the other tissues had similar levels of this isomer compared with that of the diet. It was also observed that supplementation of CLA in the diet of layer hens decreased the concentration of docosahexaenoic acid (22:6n-3) in all of the tissue lipids. It is concluded that dietary CLA can transfer to the tissue but that incorporation of CLA isomers into the tissue is selective in hens.

Animals↗
PubMed2004

Analysis of conjugated linoleic acid and trans 18:1 isomers in synthetic and animal products.

The chemistry of conjugated fatty acids, specifically octadecadienoic acids (18:2; commonly referred to as conjugated linoleic acid, or CLA), has provided many challenges to lipid analysts because of their unique physical properties and the many possible positional and geometric isomers. After the acid-labile properties of CLAs during analytic procedures were overcome, it became evident that natural products, specifically dairy fats, contain one dominant (c9,t11-CLA), 3 intermediate (t7,c9-, t9,c11-, and t11,c13-CLA), and up to 20 more minor CLA isomers. The best analytic techniques to date include a combination of gas chromatography that uses 100-m highly polar capillary columns, silver ion-HPLC, and a combination of silver ion-thin-layer chromatography and gas chromatography to analyze the CLA and trans 18:1 isomers, because some of them serve as precursors of CLA in biological systems. These analytic techniques have assisted commercial suppliers to prepare pure CLA isomers and have permitted the evaluation of individual CLA isomers for their nutritional and biological activity in animal and human systems. It is increasingly evident that different CLA isomers have distinctly different physiologic and biochemical properties. These techniques are essential to evaluate dairy fats for their CLA content, to design experimental diets to increase the amount of CLA in dairy fats, and to determine the CLA profile in these CLA-enriched dairy fats. These improved techniques are used to evaluate the CLA profile in pork products from pigs fed different commercial CLA mixtures.

Animals↗
PubMed2003

The impact of fortification with conjugated linoleic acid (CLA) on the quality of fluid milk.

The effects of added conjugated linoleic acid (CLA) on the sensory, chemical, and physical characteristics of 2% total fat (wt/wt) fluid milk were studied. Milks with 2% (wt/wt) total fat (2% CLA, 1% CLA 1% milkfat, 2% milkfat) were made by the addition of cream or CLA triglyceride oil into skim milk followed by HTST pasteurization and homogenization. The effects of adding vitamin E (200 ppm) and rosemary extract (0.1% wt/wt based on fat content) were investigated to prevent lipid oxidation. HTST pasteurization resulted in a significant decrease of the cis-9/trans-11 isomer and other minor CLA isomers. The cis-9/trans-11 isomer concentration remained stable through 2 wk of refrigerated storage. A significant loss of both the cis-9/trans-11 and the cis-10/trans-12 isomers occurred after 3 wk of refrigerated storage. The loss was attributed to lipase activity from excessive microbial growth. No differences were found in hexanal or other common indicators of lipid oxidation between milks with or without added CLA (P > 0.05). Descriptive sensory analysis revealed that milks with 1 or 2% CLA exhibited low intensities of a "grassy/vegetable oil" flavor, not present in control milks. The antioxidant treatments were deemed to be ineffective, under the storage conditions of this study, and did not produce significant differences from the control samples (P > 0.05). CLA-Fortified milk had significantly lower L* and b* values compared with 2% milkfat milk. No significant differences existed in viscosity. Consumer acceptability scores (n = 100) were lower (P < 0.05) for CLA-fortified milks compared to control milks, but the addition of chocolate flavor increased acceptability (P < 0.05).

Adolescent↗
PubMed2000

Dietary oxidized linoleic acid enhances liver cholesterol biosynthesis and secretion in rats.

Based on studies showing that excretion of cholesterol is elevated in rats fed oxidized linoleic acid, we hypothesized that cholesterol metabolism is enhanced under such oxidative stress. Liver cholesterol biosynthesis and secretion and fecal cholesterol excretion were studied in rats fed for 4 weeks diets containing 10% oxidized linoleic acid. Incubation of liver slices with 1-(14)C acetate and intraperitoneal injection of 5-(3)H-mevalonate showed the occurrence of enhanced hepatic cholesterol biosynthesis and elevated liver cholesterol secretion in animals subjected to oxidative stress. In addition, impaired liver cholesterol uptake was suggested. Higher levels of excreted cholesterol observed in the experimental animals were accompanied by augmented levels of liver phospholipids, primarily phosphatidylcholine, which most likely increased to enable the excessive cholesterol excretion. This study thus demonstrates that ingestion of oxidized lipids causes profound alterations in cholesterol metabolism.

Journal Article↗
PubMed1986

Effects of linoleic acid and cations on the activity of a novel high-molecular weight protease, ingensin, from human placenta.

A linoleic acid-sensitive protease, ingensin, was purified to homogeneity from human placenta. The physical properties of the placental ingensin were found to be very similar to those of skeletal muscle ingensin [Ishiura et al. (1985) FEBS Lett. 189, 119-123]. The purified ingensin was activated by linoleic acid and SDS. The linoleic acid-activated form was inhibited preferentially by divalent cations, whereas the SDS-activated form was inhibited by monovalent cations instead.

Cations↗