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PubMedDate not supplied

Conjugated linoleic acid: a functional food?

Scientific interest in conjugated linoleic acid (CLA) started in 1987 when Michael Pariza's team of Wisconsin University observed its inhibitory effects on chemically induced skin tumors in mice. Numerous studies have since examined CLA's role in cancer, immune function, oxidative stress, atherosclerosis, lipid and fatty acids metabolism, bone formation and composition, obesity, and diabetes. Still it's not clear yet either through which mechanisms CLA produces its numerous metabolic effects. We now know that CLA contents in cow milk fat can be enriched through dry fractionation, but this knowledge doesn't allow sufficient certainty to qualify this nutrient, as a functional food, capable of increasing well being and reducing the risk of disease.

Animals↗
PubMed2006

Inhibition of phospholipase A(2) activity by conjugated linoleic acids in human macrophages.

The objective of this study was to assess the effect of conjugated linoleic acid isomers (CLAs) on the expression and activity of phospholipases A(2) (PLA(2)) in human macrophages. Macrophages were incubated with 30 microM cis-9, trans-11 and trans-10, cis-12 CLAs for 48 h. After incubation, the total activity of phospholipases as well as the expression of mRNA for cytosolic (cPLA(2)) and secretory (sPLA(2)) phospholipases and activity of sPLA(2) were measured. Both CLA isomers reduced the total activity of PLA(2) (by 30.2%, P < 0.01 for cis-9, trans-11 CLA and by 30%, P < 0.001 for trans-10, cis-12 CLA). Trans-10, cis-12 CLA isomer downregulated the expression of mRNA of sPLA(2) and decreased the enzymatic activity of this enzyme (by 23%, P = 0.02) in macrophages. Conjugated linoleic acid isomers can significantly reduce the activity of PLA(2) in macrophages and downregulate sPLA(2) expression. The consequence of this effect may be reduction of releasing the arachidonic acid (AA) from the cellular membranes of macrophages.

Down-Regulation↗
PubMed2004

Perspective on the safety and effectiveness of conjugated linoleic acid.

The amount of scientific literature on conjugated linoleic acid (CLA) is growing at a phenomenal rate. Animal studies and clinical trials indicate the possibility that CLA could be useful in improving human health in a number of areas, eg, controlling body fat gain and enhancing immunity while also reducing inflammation and other adverse effects typically associated with immune enhancement. The background of this growing research field and mechanistic insights from animal and cell culture experiments are briefly reviewed. Experimental and clinical data relating to the safety and effectiveness of CLA in humans are presented and discussed.

Adipose Tissue↗
PubMed2005

Preparation of mono- and diacylglycerols by enzymatic esterification of glycerol with conjugated linoleic acid in hexane.

Esterification of glycerol with conjugated linoleic acid (CLA) was carried out in hexane. Lipase from Rhizomucor miehei provided a high degree of esterification (80%) in 8 h at 50 degrees C when used at 15% (w/w) in a system containing a 1:2 molar ratio of glycerol to free fatty acids. Esterification levels >80% were obtained in 8 h at 40 degrees C with 15% (w/w) lipase from Candida antarctica at the same molar ratio of reactants. The extent of esterification of CLA was >90% after 4 h of reaction at 50 degrees C with a 5% (w/w) loading of either R. miehei or C. antarctica lipase, together with a 1:1 molar ratio of substrates. Both enzymes incorporated the original CLA as acylglycerol residues in primarily 1,3-diacylglycerol and 1-monoacylglycerol. The CLA-rich acylglycerols can be employed as emulsifiers or as substitutes for natural fats and oils.

Chromatography, High Pressure Liquid↗
PubMed2003

Effects of isomers of conjugated linoleic acid on porcine adipocyte growth and differentiation.

Conjugated linoleic acids (CLAs) decrease fat deposition in mammals, including pigs. To determine mechanisms for CLA effects on adipocyte growth, porcine stromal-vascular cells (preadipocytes) were isolated and plated in medium containing 10% fetal bovine serum. After 24 h, differentiation factors (insulin + hydrocortisone + transferrin) were added. Oleic acid (200 microM) was added to some plates as a positive control. One of two isomers of CLA (50 microM cis 9, trans 11 or >50 microM trans 10, cis 12), or a mixture of the two isomers (25 microM each) was added to other plates. The cell number increased 7+ times in 7 days after initiation of differentiation, and was not different among treatment groups. By 7 days, Oil Red O-stained material (OROSM), expressed per cell, increased 10+ times in control cells and 64 times in oleic acid-treated cells. Addition of either isomer of CLA or the mixture caused OROSM/cell to increase 10+ times at 2 days, with no further increase at later times. In CLA-treated cells there was no increase in peroxisome proliferator-activated receptor gamma (PPARgamma) or lipoprotein lipase mRNA concentrations. The increased OROSM/cell may represent triacylglycerol synthesis from medium CLA using existing biosynthetic capacity or provision of a limiting ligand for PPARgamma already present. The results are different from those observed with rodent-derived clonal cells (3T3-L1 cells), wherein proliferation and differentiation are inhibited by CLAs, and the active isomer is trans 10, cis 12-CLA. The results suggest distinctions between clonal and primary preadipocytes, or species differences.

Adipocytes↗
PubMed2001

Olive oil prevents the adverse effects of dietary conjugated linoleic acid on chick hatchability and egg quality.

Dietary conjugated linoleic acid (CLA) decreases yolk 18:1(n-9), induces chick embryonic mortality and alters egg quality. A study was conducted to determine whether olive oil would prevent these adverse effects of CLA. Hens (15 per treatment) were fed diets containing 0.5 g corn oil/100 g (CO), 0.5 g CLA/100 g (CLA), 0.5 g corn oil plus 10 g olive oil/100 g (CO + OO) or 0.5 g CLA plus 10 g olive oil/100 g (CLA + OO). After 74 d of feeding, hens were placed on CO for 10 d. Hens were artificially inseminated weekly. For hatchability studies, fertile eggs were collected daily, stored at 15 degrees C for 24 h and then incubated. After 6 d of feeding, embryonic mortality rates were 15, 100, 8 and 16% in the CO, CLA, CO + OO and CLA + OO groups, respectively. When CLA-fed hens were fed the CO diet, hatchability improved to that of the CO group within 7 d. For fatty acid analysis, three eggs were obtained at the 7 d of feeding. Relative CLA levels of yolk from CO-, CLA-, CO + OO- and CLA + OO-fed hens were 0.11 +/- 0.01, 1.91 +/- 0.16, 0.08 +/- 0.04 and 0.69 +/- 0.07 g/100 g fatty acids, respectively. The ratios of 16:0/16:1(n-7) and 18:0/18:1(n-9) of yolk from CLA-fed hens were approximately 1- and approximately 1.5-fold greater, respectively, compared with those fed CO. OO prevented CLA-induced increases in 16:0 and 18:0 and the decrease in 18:1(n-9) in yolk. Fertile eggs were stored at 4 degrees C for 2 or 10 wk and analyzed for pH or mineral levels. Dietary CLA caused abnormal pH changes of albumen and yolk when eggs were stored at 4 degrees C. The pH of yolk and albumen from CO-fed hens after 10 wk of storage was 6.12 +/- 0.12 and 9.06 +/- 0.03, respectively, versus 7.89 +/- 0.25 and 8.32 +/- 0.16, respectively, in eggs from CLA-fed hens. OO prevented CLA-induced abnormal changes in the pH of albumen and yolks. Eggs from CLA-fed hens had greater iron, calcium and zinc concentrations and lower magnesium, sodium and chloride concentrations in albumen relative to those from hens fed CO. OO prevented CLA-induced mineral exchange between yolk and albumen, presumably by reducing the yolk saturated fatty acids, which are believed to disrupt the vitelline membrane during cold storage. This study suggests that the adverse effects of CLA may be due to the increased level of saturated fatty acids. However, because the addition of olive oil also lowered egg CLA content, the direct role of egg CLA on egg hatchability and quality cannot be ruled out.

Animal Feed↗
PubMed1999

Conjugated linoleic acid in canadian dairy and beef products.

Conjugated linoleic acid (CLA) is a dietary fatty acid produced by ruminant animals and exhibits promising beneficial health effects. CLA has been identified as having anticancer, antiatherogenic, and body fat reducing effects. There are no published data on the CLA content of Canadian beef and dairy products. The purpose of this study was to assess the level and type of CLA isomers found in commercial beef and dairy products. Under the present experimental conditions only the Delta9c,11t-18:2 isomer was detected. Other minor isomers, which may be present, were not determined by the method used in this study. Levels of CLA ranged between 1.2 and 6.2 mg/g of fat or 0.001-4.3 mg/g or mg/mL of sample. On the basis of a usual serving size, levels of CLA ranged between 0.03 and 81.0 mg per serving. It is concluded that the Delta9c,11t-18:2 isomer is present in dairy and beef products and levels when expressed per gram of fat are not significantly different among products.

Animals↗
PubMed2000

Dietary conjugated linoleic acid consumption during pregnancy and lactation influences growth and tissue composition in weaned pigs.

We evaluated the effects of conjugated linoleic acid (CLA) on growth performance, tissue fatty acid composition and ex vivo lipogenic enzyme activity in piglets (n = 40) reared on sows fed diets supplemented with CLA or linoleic acid (LA). Weaned offspring of both sow groups were offered either a CLA- or LA-enriched starter diet for 35 d. The starter diets were formulated to contain 2 g CLA (containing 58.9 g CLA/100 g total fatty acids) or LA per 100 g feed. All piglets were slaughtered at 70 d of age and tissue samples of the back fat, omental fat and longissimus dorsi were collected. Irrespective of the dietary fat supplied in the starter period, piglets reared on the CLA sows had greater final body and warm carcass weights (P: < 0.01), and greater feed intake (P: = 0.02) than piglets reared on the LA sows. The dietary effect on the fatty acid composition was similar for the adipose and muscle tissues. Compared with the LA-enriched diets, CLA increased the level of total saturated fatty acids (P: < 0.05), whereas that of monounsaturated fatty acids was decreased (P: < 0.05). Dietary CLA increased glucose-6-phosphate dehydrogenase (P: < 0.01) and malic enzyme activities (P: < 0.06) in the fat tissues, but did not affect fatty acid synthase activity. The shift toward a higher deposition of saturated fatty acids and a lower deposition of monounsaturated fatty acids is the result of down-regulation of Delta9-desaturase activity that was induced by CLA rather than an altered rate of de novo synthesis.

Adipose Tissue↗
PubMed1985

Incorporation of 14C into tissue lipids after oral administration of [1-14C]linoleic acid in rats fed different levels of essential fatty acids.

Rats from an inbred Sprague-Dawley strain were fed purified diets with a low (0.3% of the total energy), normal (3%) or high (10%) content of essential fatty acids (EFA) for several generations. Thirty- to 34-d-old male rats of at least the sixth generation to be fed these diets were given a single intragastric dose of [1-14C]linoleic acid in olive oil, and the respiratory CO2, urine and feces were collected for 20 h. The 14C activity was determined in the respiratory CO2, urine and feces as well as in total lipids and lipid classes of the whole animal and in nine tissue groups. The content of total lipids and lipid classes was similar in all groups. The rats in the low EFA group retained significantly more radioactivity (51%) in the tissues than the rats fed the normal EFA (34%) or the high EFA (27%) diets. In all groups most of the radioactivity was found in the skeletal muscles, skin, liver and white fat, but the retention was greater in the low EFA group than in the other groups, except in the white and brown fat. In the carcass and most tissues, the proportion of the retained 14C activity recovered in the phospholipids increased with decreasing EFA level in the diet, whereas in the triglycerides the opposite was found. Expressed as percent of administered dose, the total retention of radioactivity in the phospholipids was 31, 13 and 8% in the low, normal and high EFA group, respectively, while the retention in the triglycerides was about the same in all groups (17-18%).

Animals↗
PubMed2005

Paraoxonase-1 and linoleic acid oxidation in familial hypercholesterolemia.

Serum paraoxonase-1 (PON1) is a high-density lipoprotein-associated enzyme that can inhibit low-density lipoprotein (LDL) oxidation in vitro. The role of PON1 in vivo still remains to be clarified. We investigated the effect of PON1 genotype (-107C > T and 192Q > R), concentration, paraoxonase activity, and arylesterase activity on the early phase of lipid peroxidation in plasma samples of 110 patients with heterozygous familial hypercholesterolemia. The degree of lipid oxidation was assessed by quantitation of oxidized-linoleic acid (the most abundant fatty acid present in LDL) using high performance liquid chromatography. We found a significant inverse correlation between paraoxonase activity and the oxidized-linoleic acid concentration (r = -0.22, P = 0.03), independent of baseline linoleic acid levels. These findings support an anti-oxidative role for PON1 in patients with FH, and thus may give insight into the functioning of PON1 in vivo.

Adult↗
PubMed2000

Some polyphenols inhibit the formation of pentyl radical and octanoic acid radical in the reaction mixture of linoleic acid hydroperoxide with ferrous ions.

Effects of some polyphenols and their related compounds (chlorogenic acid, caffeic acid, quinic acid, ferulic acid, gallic acid, D-(+)-catechin, D-(-)-catechin, 4-hydroxy-3-methoxybenzoic acid, salicylic acid, L-dopa, dopamine, L-adrenaline, L-noradrenaline, o-dihydroxybenzene, m-dihydroxybenzene, and p-dihydroxybenzene) on the formation of 13-hydroperoxide octadecadienoic (13-HPODE) acid-derived radicals (pentyl radical and octanoic acid radical) were examined. The ESR spin trapping showed that chlorogenic acid, caffeic acid, gallic acid, D-(+)-catechin, D-(-)-catechin, L-dopa, dopamine, L-adrenaline, L-noradrenaline, and o-dihydroxybenzene inhibited the overall formation of 13-HPODE acid-derived radicals in the reaction mixture of 13-HPODE with ferrous ions. The ESR peak heights of alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (4-POBN)/13-HPODE-derived radical adducts decreased to 46+/-4% (chlorogenic acid), 54+/-2% (caffeic acid), 49+/-2% (gallic acid), 55+/-1% [D-(+)-catechin], 60+/-3% [D-(-)-catechin], 42+/-1% (L-dopa), 30+/-2% (dopamine), 49+/-2% (L-adrenaline), 24+/-2% (L-noradrenaline), and 54+/-5% (o-dihydroxybenzene) of the control, respectively. The high performance liquid chromatography-electron spin resonance (HPLC-ESR) and high performance liquid chromatography-electron spin resonance-mass spectrometries (HPLC-ESR-MS) showed that caffeic acid inhibited the formation of octanoic acid radical and pentyl radical to 42+/-2% and 52+/-7% of the control, respectively. On the other hand, the polyphenols and their related compounds had few inhibitory effects on the radical formation in the presence of EDTA. Visible absorbance measurement revealed that all the polyphenols exhibiting the inhibitory effect chelate ferrous ions. Above results indicated that the chelation of ferrous ion is essential to the inhibitory effects of the polyphenols.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

[Effect of diets with various contents of linoleic acid on the prostaglandin system in the rat kidney].

Effect of diets containing various amount of linoleic acid on formation of prostaglandins in kidney as well as excretion of the substances with urine were studied in 45 normotensive rats of Wistar-Kyoto strain. Distinct alterations were observed in the kidney prostaglandin system, which directly or via other hormonal systems (renin-angiotensin, antidiuretic hormone of hypophysis) caused the corresponding shifts in the water-electrolyte balance.

Animals↗
PubMedDate not supplied

[Effect of lipoxygenase derivatives of linoleic acid on functional activity of neutrophils].

The effect of lipoxygenase derivatives of 13-hydroperoxylinoleic acid (13-HPODE) and 13-hydroxylinoleic acid (13-HODE) on zymosan-induced chemiluminescence of rat neutrophils in vitro was evaluated. It was found that both derivatives inhibit functional activity of neutrophils. The extent of inhibition was changed by preincubation of neutrophils with arachidonic or linoleic acid. On the other hand, in experiments with dogs it was shown that the extent of such inhibition considerably increases after ischemia and reperfusion of myocardium. Thus we assume that the ratio of lipoxygenase derivatives of arachidonic and linoleic acid play the regulative role in functional activity of neutrophils. It was concluded, that lipoxygenase derivatives of linoleic acid inhibited the neutrophils functional activity.

Animals↗
PubMed1980

The reactivity of isolated blood vessels of salt-loaded rats fed low or high linoleic acid diets.

Vessel reactivity was studied on isolated arterial vessels of salt-loaded rats fed a linoleic acid (LA)-rich or a LA-deficient diet. The results showed that an LA-rich diet decreased arterial reactivity to prostaglandins (especially to PGE2) and an LA-deficient diet increased the sensitivity to angiotensin II. These differences were not so obvious with PGA2 and norepinephrine. The results provide evidence that dietary linoleic acid exerts an effect on the responsiveness of the vessels to vasoactive stimuli.

Angiotensin II↗
PubMedDate not supplied

[The dynamics of the secretion of linoleic acid as a component of the lipid classes with milk and their metabolism in the body of cows].

The paper is devoted to the questions of metabolism of the lipid classes and essential fatty acids in the ruminant organism and secretion of those acids with milk. The lipid classes, such as triacylglyceroles, phospholipides and cholesterol ethers, containing linoleic acid and others acids of that family, their function, structure, quantity and transport in the organism are characterized. The physiological lactation standards (duration, breed, season and diurnal variations) are described more exactly. The author's own and literature data concerning secretion of lipid classes, containing linoleic acid, on lactation periods (in the period of colostrum secretion and in all periods of milk secretion), lipid transport, transformation and metabolism in the digestive tract and the liver are discussed. The correlation of lipid classes and corresponding fatty acid composition in the forage, milk, colostrum and plasma of arterial and venous blood, obtained from ruminants, is characterized.

Animals↗
PubMed1992

Intratumoral gamma-linoleic acid therapy of human gliomas.

In vitro and in vivo studies have shown that gamma-linoleic acid (GLA), arachidonic acid (AA) and eicosapentaenoic acid (EPA) can selectively kill tumor cells. In a clinical trial, the effectiveness of intratumoral administration of GLA in patients with gliomas was studied. Of the 6 patients treated, all showed substantial response to GLA as documented by computerized tomography. There were no acute side-effects due to the therapy. This report demonstrates that intratumoral administration of GLA is a possible approach to the treatment of human glial tumors.

Adolescent↗
PubMed1995

Similar metabolites formed from beta-carotene by human gastric mucosal homogenates, lipoxygenase, or linoleic acid hydroperoxide.

To determine the basis for the formation of excentric cleavage products of beta-carotene (beta-C) after incubation with human gastric mucosal homogenates, we have studied the effect of lipoxygenase in beta-C metabolism. beta-C was incubated with human gastric mucosal homogenates, soybean lipoxygenase with linoleic acid, or the lipoxygenase primary product, 13(S)-hydroperoxycis,trans-9,11-octadecadienoic acid (13-LOOH). The beta-C metabolites, beta-apo-14', -12', -10', and -8'-carotenals, beta-apo-13-carotenone, retinoic acid, and retinal were detected and quantified by HPLC after a 30-min incubation with 1.8 microM beta-C. The products from the lipoxygenase plus linoleic acid incubation and from the lipoxygenase primary product, 13-LOOH, with beta-C were exactly the same as the products from a human gastric mucosal homogenate incubation. Significantly larger amounts of the same beta-C metabolites were formed when beta-C was incubated with gastric mucosal homogenates and lipoxygenase together. Furthermore, nordihydroguaiaretic acid (NDGA), a specific lipoxygenase inhibitor, was found to significantly inhibit the formation of beta-apo-carotenoids and retinoids produced by gastric mucosal homogenates incubated with beta-C. The similarity of the beta-C metabolites when beta-C was incubated with human gastric mucosal homogenate, lipoxygenase plus linoleic acid, or 13-LOOH and the inhibition of beta-C metabolite production by NDGA in gastric tissue incubation with beta-C suggest that lipoxygenase is involved in beta-C metabolism in gastric mucosa. The activity of 13-LOOH in our hands would indicate that an enzyme-linked process is occurring in gastric tissue producing fatty acid hydroperoxides, and that the hydroperoxide, or a radical species derived from it, is able to carry out the oxidation of beta-C independently of the enzyme.

Biotransformation↗
PubMed2000

Short communication: concentration of conjugated linoleic acid from milk fat with a continuous supercritical fluid processing system.

A continuous pilot-scale supercritical carbon dioxide system was utilized for the concentration of conjugated linoleic acids (cis-9, trans-11 C18:2) from anhydrous milk fat, which was separated into five fractions (S1 to S5) in the pressure and temperature range of 2.4 to 24.1 MPa (350 to 3500 psi) and 40 to 60 degrees C, respectively. The highest concentration of CLA attained showed an increase of about 89% and occurred in the raffinate fraction (S1) when the solvent to feed ratio was 65. This was followed by a gradual decrease in the concentration of this fatty acid from S2 to S5. This study shows the feasibility of selectively enhancing the CLA concentration in one of the fractions of milk fat with a benign solvent in a one-step process. Other unique attributes of the CLA-rich fraction are also listed.

Animals↗