Origin of cis-9, trans-11- and trans-9, trans-11-octadecadienoic Acids in the Depot Fat of Primates Fed a Diet Rich in Lard and Corn Oil and Implications for the Human Diet

Dietary supplementation with conjugated linoleic acid increased its concentration in human peripheral blood mononuclear cells, but did not alter their function

The purpose of this study was to examine if conjugated linoleic acid (CLA) supplementation of diets would alter fatty acid (FA) composition and function of peripheral blood mononuclear cells (PBMC). Seventeen women, 20-41 yr, participated in a 93-d study conducted at the Metabolic Research Unit. The same diet (19, 30, and 51% energy from protein, fat, and carbohydrate, respectively) was fed to all subjects throughout the study. Seven subjects (control group) supplemented their diet with six daily capsules (1 g each) of placebo oil (sunflower) for 93 d. For the other 10 subjects (CLA group), the supplement was changed to an equivalent amount of Tonalin capsules for the last 63 d of the study. Tonalin provided 3.9 g/d of a mixture of CLA isomers (trans-10,cis-12, 22.6%; cis-11,trans-13, 23.6%; cis-9,trans-11, 17.6%; trans-8,cis-10, 16.6%; other isomers 19.6%), and 2.1 g/d of other FA. PBMC isolated on study days 30 and 90 were used to assess intracellular cytokines by flow cytometry, secreted cytokines, and eicosanoid by enzyme-linked immonosorbent assay, and FA composition by gas-liquid chromatography. After supplementation, total CLA concentration increased from 0.012 to 0.97% (P < 0.0001) in PBMC lipids, but it did not significantly alter the concentration of other FA. CLA supplementation did not alter the in vitro secretion of prostaglandin E2, leukotriene B4, interleukin-1beta (IL-1beta), or tumor necrosis factor alpha (TNFalpha) by PBMC simulated with lipopolysaccharide, and the secretion of IL-2 by PBMC stimulated with phytohemagglutinin. Nor did it alter the percentage T cells producing IL-2, interferon gamma, and percentage of monocytes producing TNFalpha. The intracellular concentration of these cytokines was also not altered. None of the variables tested changed in the control group. Our results show that CLA supplementation increased its concentration in PBMC lipids, but did not alter their functions.

Intestinal microorganisms do not supply associated gnotobiotic rats with conjugated linoleic acid

Conjugated linoleic acid (CLA) is produced from linoleic acid (LA) by bacteria in the rumen of herbivores. CLA enters the human diet mainly via milk fat and fatty beef; it acts as an effective anticarcinogen and exhibits other important physiological effects. The objective of the current study was to investigate the capability of a LA-conjugating bacterial community isolated from a human volunteer and associated with germ-free rats to supply the host with CLA. Gnotobiotic rats were fed a diet enriched with esterified LA in the form of sunflower-seed oil. The control group was fed the same diet and remained germ-free. Bacterial cell counts, in vitro LA-conjugation activities, and CLA concentration in feces and in the contents of various intestinal segments were determined. After 10 wk, various tissues were analyzed for CLA concentrations. LA-conjugation activity was found only in feces, cecum and colon content samples from associated rats, but CLA accumulation in various body tissues did not differ significantly between the two groups. The ratio of CLA to LA in feces and in cecal and colonic contents did not differ between groups, indicating that the microorganisms in the cecum and the colon do not synthesize substantial amounts of CLA in vivo and therefore, do not contribute to the CLA supplementation of the host.

Effects of conjugated linoleic acid isomers on the hepatic microsomal desaturation activities in vitro

The influence of individual conjugated linoleic acid (CLA) isomers on the delta6 desaturation of linoleic and alpha-linolenic acids and on the delta9 desaturation of stearic acid was investigated in vitro, using rat liver microsomes. The delta6 desaturation of 18:2n-6 was decreased from 23 to 38% when the ratio of 9cis,11trans-18:2 to 18:2n-6 increased from 0.5 to 2. The compound 10trans,12cis-18:2 exhibited a similar effect only at the highest concentration. The delta6 desaturation of alpha-linolenic acid was slightly affected by the presence of CLA isomers. The sole isomer to induce an inhibitory effect on the delta9 desaturation of stearic acid was 10trans,12cis-18:2.

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.

A new conjugated linoleic acid isomer, 7 trans, 9 cis-octadecadienoic acid, in cow milk, cheese, beef and human milk and adipose tissue

The identity of a previously unrecognized conjugated linoleic acid (CLA) isomer, 7 trans, 9 cis-octadecadienoic acid (18:2) was confirmed in milk, cheese, beef, human milk, and human adipose tissue. The 7 trans, 9 cis-18:2 isomer was resolved chromatographically as the methyl ester by silver ion-high-performance liquid chromatography (Ag+-HPLC); it eluted after the major 9 cis, 11 trans-18:2 isomer (rumenic acid) in the natural products analyzed. In the biological matrices investigated by Ag+-HPLC, the 7 trans, 9 cis-18:2 peak was generally due to the most abundant minor CLA isomer, ranging in concentration from 3 to 16% of total CLA. By gas chromatography (GC) with long polar capillary columns, the methyl ester of 7 trans, 9 cis-18:2 was shown to elute near the leading edge of the major 9 cis, 11 trans-18:2 peak, while the 4,4-dimethyloxazoline (DMOX) derivative permitted partial resolution of these two CLA isomers. The DMOX derivative of this new CLA isomer was analyzed by gas chromatography-electron ionization mass spectrometry (GC-EIMS). The double bond positions were at delta7 and delta9 as indicated by the characteristic mass spectral fragment ions at m/z 168, 180, 194, and 206, and their allylic cleavages at m/z 154 and 234. The cis/trans double-bond configuration was established by GC-direct deposition-Fourier transform infrared as evidenced from the doublet at 988 and 949 cm(-1) and absorptions at 3020 and 3002 cm(-1). The 7 trans, 9 cis-18:2 configuration was established by GC-EIMS for the DMOX derivative of the natural products examined, and by comparison to a similar product obtained from treatment of a mixture of methyl 8-hydroxy- and 11-hydroxyoctadec-9 cis enoates with BF3 in methanol.

Distributions of conjugated linoleic acid (CLA) isomers in tissue lipid classes of pigs fed a commercial CLA mixture determined by gas chromatography and silver ion-high-performance liquid chromatography

Pigs were fed a commercial conjugated linoleic acid (CLA) mixture, prepared by alkali isomerization of sunflower oil, at 2% of the basal diet, from 61.5 to 106 kg live weight, and were compared to pigs fed the same basal diet with 2% added sunflower oil. The total lipids from liver, heart, inner back fat, and omental fat of pigs fed the CLA diet were analyzed for the incorporation of CLA isomers into all the tissue lipid classes. A total of 10 lipid classes were isolated by three-directional thin-layer chromatography and analyzed by gas chromatography (GC) on long capillary columns and by silver-ion high-performance liquid chromatography (Ag+-HPLC); cholesterol was determined spectrophotometrically. Only trace amounts (<0.1%; by GC) of the 9,11-18:2 cis/trans and trans,trans isomers were observed in pigs fed the control diet. Ten and twelve CLA isomers in the diet and in pig tissue lipids were separated by GC and Ag+- HPLC, respectively. The relative concentration of all the CLA isomers in the different lipid classes ranged from 1 to 6% of the total fatty acids. The four major cis/trans isomers (18.9% 11 cis,13 trans-18:2; 26.3% 10 trans,12 cis-18:2; 20.4% 9 cis,11 trans-18:2; and 16.1% 8 trans, 10 cis-18:2) constituted 82% of the total CLA isomers in the dietary CLA mixture, and smaller amounts of the corresponding cis,cis (7.4%) and trans,trans (10.1%) isomers were present. The distribution of CLA isomers in inner back fat and in omental fat of the pigs was similar to that found in the diet. The liver triacylglycerols (TAG), free fatty acids (FFA), and cholesteryl esters showed a similar pattern to that found in the diet. The major liver phospholipids showed a marked increase of 9 cis,11 trans-18:2, ranging from 36 to 54%, compared to that present in the diet. However, liver diphosphatidylglycerol (DPG) showed a high incorporation of the 11 cis,13 trans-18:2 isomer (43%). All heart lipid classes, except TAG, showed a high content of 11 cis,13 trans-18:2, which was in marked contrast to results in the liver. The relative proportion of 11 cis,13 trans-18:2 ranged from 30% in the FFA to 77% in DPG. The second major isomer in all heart lipids was 9 cis,11 trans-18:2. In both liver and heart lipids the relative proportions of both 10 trans,12 cis-18:2 and 8 trans, 10 cis-18:2 were significantly lower compared to that found in the diet. The FFA in liver and heart showed the highest content of trans,trans isomers (31 to 36%) among all the lipid classes. The preferential accumulation of the 11 cis,13 trans-18:2 into cardiac lipids, and in particular the major phospholipid in the inner mitochondrial membrane, DPG, in both heart and liver, appears unique and may be of concern. The levels of 11 cis,13 trans-18:2 naturally found in foods have not been established.

Unusual fatty acids in the depot fat of the Canadian beaver (Castor canadensis)

Unusual fatty acids in the adipose tissue of the Canadian beaver were analysed by argentation thin-layer chromatography, gas-liquid chromatography and gas chromatography-mass spectrometry of several adducts and spectroscopic measurements. The total proportion of trans-octadecenoic fatty acids and the distribution of double bonds in these acids resembled those of ruminant fats. Because trans-11-18:1 was the main trans-18:1 isomer of beaver fat and a conjugated diene cis-9, trans-11-18:2 was also detected, it can be deduced that linoleic acid (cis-9, cis-12-18:2) is biohydrogenated in the beaver. The ideas that microbial processes intervene before normal absorption and fatty acid metabolism of the beaver is also supported by the larger amounts of anteiso odd-chain fatty acids with respect to the corresponding iso acids in the beaver depots. In addition, the distribution of double bonds in the cis-octadecenoic acids was wide, as it is in the depot fats of ruminants.

Survey of the conjugated linoleic acid contents of dairy products

The objective of this research was to determine the content of conjugated linoleic acid, an anticarcinogen, in dairy products. Fifteen cheeses, three fermented dairy products (other than cheeses), and four fluid milk products (two brands for each product) were included in the survey. Total lipids, fatty acids, protein, moisture, and titratable acidity were also measured to determine the relationship between the content of these constituents and conjugated linoleic acid content. The conjugated linoleic acid content of cheeses ranged from 3.59 to 7.96 mg/g of lipid. Blue, Brie, Edam, and Swiss cheeses had significantly higher conjugated linoleic acid content than the other cheeses. Sharp Cheddar cheeses tended to have higher conjugated linoleic acid content than the medium Cheddar cheeses, but the increase was not significant. The conjugated linoleic acid content of the other fermented dairy products ranged from 3.82 to 4.66 mg/g of lipid, and cultured buttermilk had the highest content. The conjugated linoleic acid contents of four fluid milks ranged from 3.38 to 6.39 mg/g of lipid and were not significantly different from one another. Multiple linear regressions of conjugated linoleic acid content and the total fatty acid content indicated a relationship between conjugated linoleic acid content and the content of precursors and intermediates of conjugated linoleic acid formation, including linoleic and oleic acids.

Confirmation by gas chromatography/mass spectrometry of two unusual trans-3-monoethylenic fatty acids from the Nova Scotian seaweeds Palmaria palmata and Chondrus crispus

The structures of two unusual fatty acids, the known trans-3-hexadecenoic acid and a novel trans-3-tetradecenoic acid, both isolated from the Nova Scotian seaweeds Palmaria palmata and Chondrus crispus, were positively identified. After the extraction of the total fatty acids by saponification, followed by methylation, the monoenoic trans fractions were isolated by thin-layer chromatography on silica gel impregnated with silver nitrate. The monoenoic trans fractions were derivatized with 2-amino-2-methyl-propanol prior to analysis by gas chromatography/mass spectrometry. The mass spectra showed prominent [M + 1]+ ions but lacked the 12 amu interval useful for identifying the double bond position. Hence, alternative diagnostic peaks were used to confirm the position of the double bond in these two fatty acids. As the trans-3-hexadecenoic acid is found in the photosynthetic tissue of all plants, it may also be present in ruminant fats and, presumably, in human adipose tissue.

A method for the measurement of a diene-conjugated derivative of linoleic acid, 18:2(9,11), in serum phospholipid, and possible origins

A method is described for the measurement of a diene-conjugated derivative of linoleic acid, 18:2(9,11), in the phospholipid fraction of serum. The method is based on enzymatic hydrolysis, solid-phase sample preparation, and high-performance liquid chromatography (HPLC). Phospholipid esterified 18:2(9,11) can be detected in serum from normal individuals, and a provisional normal range is provided. The possible origins of 18:2(9,11) and the potential application of this method to the measurement of free radical damage to linoleic acid in vivo is discussed.