T11 Conjugated Linoleic Acid Research Articles

Cytotoxic effects of the conjugated linoleic acid isomers t10c12, c9t11-CLA and mixed form on rat hepatic stellate cells and CCl 4-induced hepatic fibrosis

Rat hepatic stellate cells (HSC-T6) were incubated for 24 h with 10–180 μM of t10c12 (98%), c9t11 (96%) and a mixed form (c9,t11:t10,c12; 41%:44%) of conjugated linoleic acid (CLA). The MTS dye reduction was measured to verify cell viability in a dose-dependent manner. Among the three CLAs, c9,t11-CLA exhibited the most intense cytotoxic effect on HSCs, the survival rate of which was reduced to 60% under 80 μM of treatment, while cell survival was slightly affected by the mixed form. Three CLA-induced cell deaths were determined by measuring DNA fragmentation using 4′,6-diamidino-2-phenylindole staining. The degrees of DNA fragmentation were the most severe in HSC treated with 80 μM of c9,t11-CLA. The mitogen-activated protein kinase/extracellular signal-regulated kinase-kinase and mitogen-activated or extracellular signal-regulated protein kinase (MEK) 1 and 2 were not activated in the t10,c12-CLA treatment. This suggests that the MEK-dependent apoptosis signal is crucial in HSC, which is induced by c9,t11 and mixed CLA. In order to evaluate the protective effect of CLA on carbon tetrachloride (CCl 4)-induced hepatic fibrosis in vivo, animals were treated with 10% CCl 4 to induce hepatic fibrosis during all experimental periods. Rats were divided into two treatment groups: (1) control diet with tap water ad libitum ( n=15) and (2) 1% CLA diet with tap water ad libitum ( n=15). In the CLA-supplemented rat livers, α-smooth muscle actin-positive cells were significantly reduced around the portal vein. In addition, collagen fibers were not detected in the CLA-treated group. These results suggest that 9c,11t-CLA influences cytotoxic effect on HSC in an MEK-dependent manner and preserving liver from fibrosis.

Influence of conjugated linoleic acid isomers on the metastasis of colon cancer cells in vitro and in vivo

This study investigated the isomer-specific effects of cis-9, trans-11 ( c9, t11) and trans-10, cis-12 ( t10, c12) conjugated linoleic acid (CLA) on the metastasis of colon cancer cells in vitro and in vivo. Cell migration was examined by a Boyden chamber assay in SW480 cells. MMP-9 activity was monitored by gelatin zymography, and MMP-9 protein and mRNA levels were determined by Western blot and RT-PCR analysis, respectively, in SW480 cells. For the experimental metastasis, BALB/c mice were injected intravenously with CT-26 cells in the tail vein. Mice were fed a diet containing either no CLA or 0.1% c9, t11 or t10, c12 CLA for 4 weeks. In experimental metastasis, the numbers of pulmonary nodules were significantly lower in mice fed CLA isomers than in mice fed a control diet ( P<.05). Results from the Boyden chamber assay revealed that c9, t11 CLA significantly inhibited cell migration ( P<.05), whereas t10, c12 CLA had no effect on cell migration. The activity of MMP-9 was significantly inhibited by c9, t11 CLA ( P<.05) but not by t10, c12 CLA. However, neither MMP-9 protein nor mRNA levels were altered by either of these CLA isomers. We have demonstrated that diets containing 0.1% c9, t11 and t10, c12 CLA were equally effective in inhibiting colon cancer cell metastasis in vivo. However, in vitro, only c9, t11 but not t10, c12 inhibited colon cancer cell migration and MMP-9 activity.

Influence of slaughter season and muscle type on fatty acid composition, conjugated linoleic acid isomeric distribution and nutritional quality of intramuscular fat in Arouquesa-PDO veal

The effects of the slaughter season and muscle type on lipid and conjugated linoleic acid (CLA) contents, fatty acid composition and isomeric profile of CLA in Arouquesa veal, from calves reared according to the specifications of the protected designation of origin (PDO), were assessed. Arouquesa purebred calves ( n = 31) were raised in a traditional production system, slaughtered in early autumn (October) or late spring (June), and the longissimus dorsi and semitendinosus muscles were sampled for analysis. Arouquesa-PDO veal only showed seasonal differences in the levels of some minor fatty acids (16:1c9, 17:1c9, 18:1t, 18:3 n − 3, 20:0 and 22:4 n − 6) and CLA isomers (t12,t14, t9,t11 and c11,t13). Furthermore, significant interactions between the slaughter season and muscle type were obtained for several fatty acids and CLA isomers, total lipids and CLA, and the PUFA/SFA ratio. In both seasons, veal-PDO depicts values of pasture-fed cattle. From a human nutritional perspective, veal-PDO in both slaughter seasons has relatively high CLA contents and percentages of the c9,t11 CLA isomer, which is favourable, while the n − 6/ n − 3 ratios are within the recommended values for the human diet. In conclusion, the results suggest that intramuscular fat in Arouquesa-PDO veal has high nutritional value throughout the year.

Rumenic Acid Significantly Reduces Plasma Levels of LDL and Small Dense LDL Cholesterol in Hamsters Fed a Cholesterol‐ and Lipid‐Enriched Semi‐Purified Diet

Conjugated linoleic acids (CLAs) consist of a series of positional and geometrical isomers of linoleic acid. CLA have been reported to beneficially affect cardiovascular risk factors in animal models. In order to assess the role of individual CLA isomers on lipoprotein cholesterol concentration, 30 hamsters were fed for 12 weeks an hyperlipidic diet containing pure cis-9,trans-11 CLA (c9,t11) or pure trans-10, cis-12 CLA (t10,c12) isomers given alone or as a mixture. Plasma total cholesterol, LDL and HDL cholesterol concentrations were significantly lower in the c9,t11 CLA isomer fed hamsters relative to the Control group, with the most substantially effect on LDL cholesterol (-56%; P < 0.05). Plasma triacylglycerol concentrations did not differ significantly regarding those two groups. Plasma cholesterol parameters showed a tendency to decrease in the t10,c12 CLA isomer and CLA mixture fed hamsters compared with the Control group, but differences were not significant. For the first time, the atherogenic fraction of small dense LDL was investigated. Plasma small dense LDL cholesterol concentration was lower in the c9,t11 CLA relative to Control, while the t10,c12 and CLA mixture groups showed only a non significant tendency to decrease. Taken together, these data indicate that feeding rumenic acid (c9,t11 CLA) may beneficially affect lipoprotein profile in hamster fed a cholesterol- and lipid-enriched semi-purified diet, when t10,c12 CLA isomer or CLA mixture would be less active.

Individual and combined effects of docosahexaenoic acid, stearic acid, trans‐vaccenic acid, and c9,t11‐conjugated linoleic acid on hepatic gene expression

Dietary long-chain fatty acids (LCFA), polyunsaturated fatty acids (PUFA) and their combinations alter metabolism by modulating expression of fatty acid synthase (FAS), carnitine palmitoyltransferase-1a (CPT-1a), and acyl-CoA oxidase (ACO). The effects of LCFA and PUFA on mRNA expression were determined in H4IIE rat hepatoma cells incubated with docosahexaenoic acid (DHA), c9, t11-conjugated linoleic acid (CLA), trans-vaccenic acid (TVA), and stearic acid (SA) or their combinations. Treatments were: 200 μM of individual fatty acids DHA, CLA, SA, or TVA; Replacement of 100 μM DHA with either 100 μM CLA or 100 μM SA; 100 μM CLA replaced by 100 μM TVA (final fatty acid concentration of 200 μM); 200 μM of DHA or CLA supplemented with 200μM of CLA, SA, or TVA. When CLA replaced DHA, FAS mRNA decreased by 53.7% (P< 0.05). Replacement of DHA with SA resulted in a 74.9% decrease (P< .05) in FAS mRNA. When 200 μM CLA was supplemented with 200 μM DHA or with 200 μM TVA, FAS mRNA decreased (P< 0.05) by 62.4% and 48.6% respectively. When CLA was replaced with TVA, CTP-1a mRNA tended (P= 0.05) to decrease by 47.5%. When CLA was supplemented with DHA there was a tendency (P< 0.10) for a 40.2% decrease in CPT-1a mRNA. Fatty acid concentration and mixture had no effect on ACO mRNA. The data suggest that individual and combined LCFA/PUFA exert different potencies on expression of genes for fatty acid metabolism in liver.

The effect of pH and polyunsaturated C18 fatty acid source on the production of vaccenic acid and conjugated linoleic acids in ruminal cultures incubated with docosahexaenoic acid

Previously, combining docosahexaenoic acid (DHA) with linoleic acid in rumen cultures enhanced vaccenic acid (VA) and conjugated linoleic acid (CLA) accumulations. The objective of this experiment was to examine the effect of two pH levels and two polyunsaturated C18 fatty acid (FA) sources on VA and CLA accumulations in rumen cultures incubated with DHA. High pH culture treatments consisted of 10 mg DHA + 20 mg linoleic acid (LOH), or 10 mg DHA + 20 mg linolenic acid (LNH). Low pH culture treatments consisted of 10 mg DHA + 20 mg linoleic acid (LOL), or 10 mg DHA + 20 mg linolenic acid (LNL). Treatments were incubated in triplicate in 125 ml flasks containing 500 mg finely ground TMR, 10 ml strained ruminal fluid, 40 ml media, and 2 ml reducing solution. Ruminal fluid was collected from fermenters fed high forage (pH 6.7) or high grain diets (pH 5.4). A 5-ml sample of culture contents was taken at 0 and 24 h for fatty acid analysis by gas liquid chromatography. After 24 h of incubation, VA was the predominant trans C18:1 FA isomer in the high pH cultures and its concentration was greater with LOH (20.9 mg/culture) than with LNH (9.3 mg/culture). Similarly, t10 C18:1 was the predominant trans C18:1 FA isomer in the low pH cultures and its concentration was greater with LOL (12.8 mg/culture) than with LNL (4.5 mg/culture). The c9 t11 CLA (0.74 mg/culture) and tt CLA (0.67 mg/culture) were the predominant CLA isomers in the LOH cultures, while t10 c12 CLA (1.47 mg/culture) and tt CLA (1.27 mg/culture) were the predominant CLA isomers in the LOL cultures. The t11 t13 CLA increased in linolenic acid cultures, particularly when linolenic acid incubated under low pH condition (0.95 mg/culture). Additions of linolenic acid to rumen cultures caused a dramatic increase in the concentration of t11 c15 C18:2 (9.84 and 8.45 mg/culture, for treatments LNH and LNL, respectively). The concentrations of VA and c9 t11 CLA in rumen cultures were greatest when DHA was incubated with linoleic acid at high pH. In contrast, t10 C18:1 replaced VA and c9 t11 CLA disappeared when linoleic and linolenic acids were incubated under the low pH condition. This study shows that the best approach to increase ruminal VA production, and potentially c9 t11 CLA levels in ruminant food products, is by combining a DHA source (such as fish oil or algae) and linoleic acid source under high ruminal pH condition.

Intestinal Bifidobacteria That Produce trans-9, trans-11 Conjugated Linoleic Acid: A Fatty Acid With Antiproliferative Activity Against Human Colon SW480 and HT-29 Cancer Cells

: Bifidobacterium breve species of human intestinal origin have the ability to synthesize cis-9, trans-11 (c9, t11) conjugated linoleic acid (CLA) from free linoleic acid. In this study, the ability of Bifidobacterium species to isomerize C18 polyunsaturated fatty acids was investigated, and the antiproliferative activities of the two main microbially produced CLA isomers were assessed. Linoleic acid was converted principally to c9, t11 CLA and lesser amounts of t9, t11 CLA, whereas c9, t11 CLA was converted mainly to t9, t11 CLA. Likewise, t10, c12 CLA was converted principally to t9, t11 CLA, which was incorporated into the bacterial cell membranes. To examine the antiproliferative effect of the two main CLA isomers formed, SW480 and HT-29 human colon cancer cells were cultured in the presence of c9, t11 CLA and t9, t11 CLA. The t9, t11 CLA had a more potent antiproliferative effect than c9, t11 CLA. It is tempting to suggest that the ability of Bifidobacterium to produce such bioactive metabolites may be associated with the beneficial effects of bifidobacteria present in the human gastrointestinal tract.

Cytokine-induced monocyte adhesion to endothelial cells involves platelet-activating factor: Suppression by conjugated linoleic acid

Monocyte–endothelium interaction is key to many acute and chronic inflammatory diseases. We have investigated the factors regulating monocyte attachment to cytokine-activated human umbilical vein endothelial cells (HUVEC) and the modulatory effect of the polyunsaturated fatty acid (PUFA), conjugated linoleic acid (CLA) in this process. Both TNF-α and IL-1β induced HUVEC platelet-activating factor (PAF) production and PAF was required for subsequent firm THP-1 monocyte adhesion since it was inhibited by both PAF receptor antagonists (BN-52021 or CV-6209) and a PAF synthesis inhibitor (sanguinarine). CLA inhibited the binding of both THP-1 and isolated human peripheral blood monocytes to HUVEC by up to 40% with the CLA t10,c12 isomer suppressing adhesion dose-dependently. Investigation into the mechanism involved demonstrated that with IL-1β, VCAM-1 and ICAM-1 levels and pro-inflammatory cytokine expression were largely unaffected by CLA. Through the use of PAF receptor antagonists and PAF synthesis inhibitors, CLA was shown to inhibit cytokine-induced binding by suppressing PAF production. Direct assay of PAF levels confirmed this result. We conclude that endothelial-generated PAF plays a central role in cytokine-induced monocyte adherence to endothelium and that the anti-inflammatory action of PUFAs such as CLA in suppressing monocyte–endothelial interaction is mediated through attenuation of pro-inflammatory phospholipids such as PAF.

Conjugated linoleic acid and human health‐related outcomes

Summary There has been increasing interest in health benefits of conjugated linoleic acid (CLA) based on findings with laboratory animals. Some human studies have also suggested health benefits of CLA, but because of the mixes used these could not be readily associated with a particular isomer of CLA. A recent study examined the separate effects of near‐pure cis‐9,trans‐11 CLA (c9,t11 CLA) or trans‐10,cis‐12 CLA (t10,c12 CLA) on health‐related outcomes in healthy young males. The CLA isomers were provided in capsules and at three doses (up to about 2.5 g/day) each for 8 weeks. Both c9,t11 and t10,c12 CLA were incorporated in a dose–response fashion into blood lipids and cells. At the doses and durations used, neither isomer of CLA affected bodyweight, body mass index or body composition, insulin sensitivity, immune function or markers of inflammation. However, at the doses and durations used, c9,t11 and t10,c12 CLA had opposing effects on blood lipid concentrations. Altered dairy cow‐feeding practices were used to produce c9,t11 CLA‐rich milk and, from this ultra heat‐treated milk, cheese and butter were produced. The milk and the dairy products made from it had ninefold higher contents of c9,t11 CLA, higher contents of n‐3 fatty acids and lower contents of total fat and of saturated fatty acids. They also contained much higher contents of trans‐vaccenic acid (tVA). The modified dairy products were used in a 6‐week controlled dietary intervention study in healthy middle‐aged males. c9,t11 CLA and tVA were incorporated from dairy products into blood lipids and cells. Consumption of the CLA‐rich (and tVA‐rich) dairy products did not affect bodyweight or body mass index, insulin sensitivity or inflammatory markers. However, there were some detrimental effects on blood lipids. These effects may be due to tVA rather than to c9,t11 CLA, as they are consistent with the effects of trans fatty acids and not consistent with the effects of c9,t11 CLA identified in the earlier study with c9,t11 CLA in capsules.

1141646904 Influence of conjugated linoleic acid (CLA) on proliferation and cytokine synthesis in maternal, fetal and decidual lymphocytes after stimulation with allergens

Background: Fetal programming is the notion that adverse environmental conditions in utero can cause short term survival adaptations that may have long‐term consequences, such as chronic disease in subsequent lifetime. Recently, some authors reported that the increase of allergy prevalence in childhood may be linked with fetal immune development. In this regard, literature survey inspired to study the influence of two conjugated linoleic acid (CLA)‐isomers (c9,t11 and t10,c12) on parameters of the immune system in pregnancy.Methods: Lymphocytes from allergic and non‐allergic mothers, cord blood of their newborns, and the decidual layer of term placentae were isolated and cultured for 2 days and supplemented or not with relevant allergens, c9,t11 CLA, t10,c12 CLA or linoleic acid, respectively. Expression of CD69 (activation marker) and CD71 (transferrin receptor; proliferation marker) on B and T lymphocytes and T helper cell type 1 (Th1) and Th2 cytokines in culture supernatant were analyzed.Results: Both CLA isomers led to an increase of the IFN‐γ/IL‐10 ratio in supernatants of peripheral maternal and cord blood cells from allergic patients and non‐allergic‐control. CLA supplementation decreased IL‐10 secretion of peripheral maternal and decidual lymphocytes and the portion of CD71+ maternal B cells. Linoleic acid induced a similar effect.Conclusion: An immunological effect of CLA on maternal and fetal lymphocyte responses could be demonstrated. It would be expected that further investigations could reveal differences in effects of CLA and linoleic acid.

Fatty acid composition of liver, adipose tissue, spleen, and heart of mice fed diets containing t10, c12-, and c9, t11-conjugated linoleic acid

Conjugated linoleic acid (CLA) isomers have unique effects on tissue lipids. Here we investigated the influence of individual CLA isomers on the lipid weight and fatty acid composition of lipid metabolizing (i.e. liver and retroperitoneal adipose) and lipid sensitive (i.e. spleen and heart) tissues. Female mice (8 week old; n=6/group) were fed either a control or one of the two CLA isomer supplemented (0.5%) diets for 8 weeks. The cis-9, trans-11-CLA diet reduced the 18:1n -9 wt% by 20–50% in liver, adipose tissue, and spleen, reduced the spleen n-3 polyunsaturated fatty acid (PUFA) by 90%, and increased the n-6 PUFA wt% by 20–50% in all tissues except heart. The trans-10, cis-12-CLA reduced both the n-6 and n-3 PUFA wt% in liver (>50%), reduced the heart n-3 PUFA wt% by 25%, and increased the wt% of spleen n-3 PUFA by 700%. The functional consequences of such changes in tissue fatty acid composition need to be investigated.

Effects of fatty acids on skeletal muscle cell differentiationin vitro

Previous studies have shown stimulatory effects of linoleic acid (LA, C18:2) on differentiation of rat muscle cells in culture (Allen et al. 1985), but there appears to be little investigation of the effects of other fatty acids. The present study therefore compared the effects of different fatty acids on muscle cell differentiation in vitro. L6 myoblasts were cultured (Dulbecco's Modified Eagles Medium + 10 % fetal calf serum) in six-well plates until 80 % confluent (day 0). Cells were then either harvested or the medium switched to differentiation medium (Dulbecco's Modified Eagles Medium+2 % horse serum), supplemented with fatty acid or drug treatments. Cells were harvested on days 0-5 and assayed for creatine kinase (CK), protein and DNA contents, to give a measure of differentiation (CK/DNA). Initial studies indicated a stimulatory effect of the cis9,trans11 (c9,t11) isomer of conjugated linoleic acid (CLA) relative to control. By contrast, the trans10,cis12 (t10,c12) isomer of CLA inhibited differentiation. Further experiments indicated that inhibition of differentiation by the t10,c12 CLA isomer was dose-dependent (up to 200 microm) and may be via increased cell proliferation. LA and c9,t11 CLA stimulated differentiation at low concentrations (up to 50 microm), but inhibited differentiation at high concentrations (200 microm). In contrast, oleic acid stimulated differentiation at all concentrations, whereas the saturated fatty acid, palmitic acid, had no effect. The mechanism appeared not to involve either peroxisome proliferator-activated receptors alpha or gamma. The data suggest that only unsaturated fatty acids have an effect and the presence or absence of a cis-9 double bond may be important.

T10,c12 conjugated linoleic acid induces compensatory growth after immune challenge

Previous work demonstrated that feeding commercial preparations of conjugated linoleic acid (CLA) [a 50:50 mixture of c9,t11 and t10,c12 CLA (cCLA)] partially overcame lipopolysaccharide (LPS)-induced growth depression. The objective of this study was to determine which CLA isomer was responsible for the reduction of LPS-induced growth depression. Dietary cCLA supplementation for 3 weeks protected mice from LPS-induced weight loss 24 h after injection compared to mice fed isocaloric and isonitrogenous control diets supplemented with either corn oil (CO) or a mixture of CO and olive oil. Dietary c9,t11 or t10,c12 CLA led to body weight loss intermediate to controls and cCLA. After LPS-induced weight loss, the t10,c12 CLA fed mice regained weight faster than the control or c9,t11 CLA fed mice. Dietary t10,c12 CLA and cCLA reduced plasma tumor necrosis factor 2 h after LPS stimulation. While neither c9,t11 nor t10,c12 CLA isomers alone protected from immune-induced weight loss, the t10,c12 CLA isomer induced compensatory gain.

The effects of t10,c12 CLA isomer compared with c9,t11 CLA isomer on lipid metabolism and body composition in hamsters

The objective of the present study was to examine the effects of two different isomers of conjugated linoleic acid (CLA), c9,t11 CLA and t10,c12 CLA, compared with linoleic acid (LA) used as control, on body composition, lipoprotein profile, hepatic lipids and fecal fat content in hamsters. Animals were assigned to the three diet groups ( n=15) during 28 days. The diet was composed of 2% of the experimental fat, and throughout the experimental protocol, the hamsters experienced similar food intake. No significant differences were noted in body weight gain among the three diet groups. However, the t10,c12 CLA-fed animals showed higher low-density lipoprotein cholesterol (LDL-C) concentrations (0.9±0.1 mmol/L) than those who ingested either LA (0.6±0.1 mmol/L) or c9,t11 CLA isomer (0.7±0.1 mmol/L), although the t10,c12 CLA consumption decreased hepatic cholesterol and triglycerides and increased fecal fat content compared with the other two groups. Under the present experimental conditions, the dietary c9,t11 CLA isomer showed no positive beneficial effect on plasma lipids. Furthermore, the t10,c12 CLA isomer induced undesirable higher LDL-C, although it reduced hepatic lipids and fat digestibility in hamsters.

Effects of the individual isomers cis‐9,trans‐11 vs. trans‐10,cis‐12 of conjugated linoleic acid (CLA) on inflammation parameters in moderately overweight subjects with LDL‐phenotype B

Immune-modulating effects of CLA have been reported in animals, but results are inconsistent. In humans, CLA has shown no effects or only minor effects on immune function. The objective of this study was to evaluate the immune-modulating effects of 3 g cis-9,trans-11 (c9,t11) vs. trans-10,cis-12 (t10,c12) CLA isomers in a population with a high risk of coronary heart disease characterized by moderate overweight (body-mass index, 25-32.5 kg/m2) in combination with LDL-phenotype B (> or = 35% small LDL cholesterol, density > or = 1.040 g/mL). After a run-in period of 1 wk, 42 men and women were randomly allocated to the c9,t11 CLA group, the t10,c12 CLA group, or the placebo group. Effects of 13 wk of consumption of 3 g of CLA isomers on cytokine production by ex vivo lipopolysaccharide (LPS)-stimulated peripheral blood mononuclear cells (PBMC) and whole blood, and on plasma C-reactive protein (CRP) concentrations were evaluated. To generate hypotheses for future studies, protein expression patterns of 42 cytokines, chemokines, and growth factors were evaluated with an antibody array in pooled, nonstimulated, fasting plasma samples. LPS induced interleukin (IL)-6, IL-8, and tumor necrosis factor-alpha production by PBMC, and whole blood as well as plasma CRP concentrations were not significantly changed by the c9,t11 and the t10,c12 CLA isomers. The cytokine expression profile in nonstimulated plasma suggested that both CLA isomers induced a specific inflammatory signature, in which the c9,t11 CLA group showed more activity in terms of numbers of proteins regulated. We conclude that daily consumption of 3 g of c9,t11 or t10,c12 CLA isomer did not affect LPS-stimulated cytokine production by PBMC or whole blood and plasma CRP levels. Inflammatory signatures in fasting, nonstimulated plasma as determined by an antibody array may indicate enhanced immune function by both CLA isomers.

Incorporation ofcis-9,trans-11 conjugated linoleic acid and vaccenic acid (trans-11 18:1) into plasma and leucocyte lipids in healthy men consuming dairy products naturally enriched in these fatty acids

The present study investigated whether consuming dairy products naturally enriched in cis-9, trans-11 (c9,t11) conjugated linoleic acid (CLA) by modification of cattle feed increases the concentration of this isomer in plasma and cellular lipids in healthy men. The study had a double-blind cross-over design. Subjects aged 34-60 years consumed dairy products available from food retailers for 1 week and then either control (0.17 g c9,t11 CLA/d; 0.31 g trans-vaccenic acid (tVA)/d) or CLA-enriched (1.43 g c9,t11 CLA/d; 4.71 g tVA/d) dairy products for 6 weeks. After 7 weeks washout, this was repeated with the alternate products. c9,t11 CLA concentration in plasma lipids was lower after consuming the control products, which may reflect the two-fold greater c9,t11 CLA content of the commercial products. Consuming the CLA-enriched dairy products increased the c9,t11 CLA concentration in plasma phosphatidylcholine (PC) (38 %; P = 0.035), triacylglycerol (TAG) (22 %; P < 0.0001) and cholesteryl esters (205 %; P < 0.0001), and in peripheral blood mononuclear cells (PBMC) (238 %; P < 0.0001), while tVA concentration was greater in plasma PC (65 %; P = 0.035), TAG (98 %; P = 0.001) and PBMC (84 %; P = 0.004). Overall, the present study shows that consumption of naturally enriched dairy products in amounts similar to habitual intakes of these foods increased the c9,t11 CLA content of plasma and cellular lipids.

Incorporation of cis-9, trans-11 or trans-10, cis-12 conjugated linoleic acid into human erythrocytes in vivo

The purpose of this study was to determine the incorporation into erythrocytes of cis (c)-9, trans (t)-11 conjugated linoleic acid (CLA) and t10,c12 CLA consumed as supplements highly enriched in these isomers. Healthy men (31 ± 8 years) consumed 1, 2, and 4 capsules containing approximately 80 g/100 g of either c9,t11 CLA or t10,c12 CLA for sequential 8-week periods. Fatty acid concentrations in erythrocyte total lipids were determined at baseline and after consumption of the highest dose. The increase in c9,t11 CLA concentration (0.31 g/100 g) was significantly greater than that in t10,c12 CLA (0.19 g/100 g). This was associated with minor changes in concentrations of some fatty acids of chain length greater than 20 carbons. These data suggest selective assimilation of individual CLA isomers into erythrocyte lipids and partial substitution for specific saturated and polyunsaturated fatty acids.

The effect of conjugated linoleic acid on the viability and metabolism of human osteoblast-like cells

Studies in experimental animals and murine osteoblast cells in culture have produced conflicting findings on the effect of conjugated linoleic acid (CLA) on bone formation. The present study investigated the influence of CLA on viability and metabolism of two human osteoblast-like cell lines (SaOS2 and MG63). Both cell lines were exposed to increasing concentrations (0–50 μM) of CLA either as pure cis (c) 9: trans (t) 11 and t10:c12 CLA isomers or a blend of isomers, or linoleic acid (C18:2). Cell cytotoxicity and degree of DNA fragmentation were unaffected by any fatty acid treatment. PGE 2 biosynthesis by both cell lines was variably reduced by CLA isomer blend and t10:c12 CLA, but not c9:t11 CLA. Alkaline phosphatase activity was variably increased by all CLA treatments. These results suggest a lack of cytotoxic effect of CLA on human osteoblast-like cells and tentatively suggest a possible beneficial effect on bone formation in humans.

Occurrence of conjugated linoleic acid in longissimus dorsi muscle of water buffalo ( Bubalus bubalis) and zebu-type cattle raised under savannah conditions

Lipid extracts from longissimus dorsi muscles of 64 water buffaloes and 68 zebu-type cattle were used to quantify the amount (mg/g of lipids) of total conjugated linoleic acid (CLA), CLA isomers c9, t11 and t10, c12 and linoleic acid (LA), according to species (buffaloes and cattle), age (slaughter groups at 7, 17, 19 or 24 months of age) and gender (bulls and steers). The effects of gender and age were significant ( P < 0.05) but marginal. Comparisons of lipid extracts from buffaloes vs. cattle showed that total CLA (1.83 vs. 1.47 mg/g), CLA c9, t11 (1.27 vs. 1.01 mg/g) and CLA t10, c12 (0.56 vs. 0.47 mg/g) isomers as well as the CLA/LA ratio (0.10 vs. 0.07) were higher ( P < 0.05) in buffalo lipids. Considering the sparingly low lipid concentrations (<2 g/100 g of fresh muscle) none of the meat species should be considered a significant source of CLA.

Effects of cis-9,trans-11 conjugated linoleic acid supplementation on insulin sensitivity, lipid peroxidation, and proinflammatory markers in obese men

We recently showed that trans-10,cis-12 (t10,c12) conjugated linoleic acid (CLA) causes insulin resistance in obese men. However, metabolic effects of the c9,t11 CLA isomer are still unknown in obese men. Because c9,t11 CLA is the predominant CLA isomer in foods and is included in dietary weight-loss products, it is important to conduct randomized controlled studies that use c9,t11 CLA preparations. We investigated the effects of c9,t11 CLA supplementation on insulin sensitivity, body composition, and lipid peroxidation in a group at high risk for cardiovascular disease. In a randomized, double-blind, placebo-controlled study, 25 abdominally obese men received 3 g c9,t11 CLA/d or placebo (olive oil). Before and after 3 mo of supplementation, we assessed insulin sensitivity (hyperinsulinemic euglycemic clamp), lipid metabolism, body composition, and urinary 8-iso-prostaglandin F(2alpha) (a major F(2)-isoprostane) and 15-keto-dihydro-prostaglandin F(2alpha), markers of in vivo oxidative stress and inflammation, respectively. All subjects completed the study. Compared with placebo, c9,t11 CLA decreased insulin sensitivity by 15% (P < 0.05) and increased 8-iso-prostaglandin F(2alpha) and 15-keto-dihydro-prostaglandin F(2alpha) excretion by 50% (P < 0.01) and 15% (P < 0.05), respectively. The decreased insulin sensitivity was independent of changes in serum lipids, glycemia, body mass index, and body fat but was abolished after adjustment for changes in 8-iso-prostaglandin F(2alpha) concentrations. There were no differences between groups in body composition. A CLA preparation containing the purified c9,t11 CLA isomer increased insulin resistance and lipid peroxidation compared with placebo in obese men. Because c9,t11 CLA occurs in commercial supplements as well as in the diet, the present results should be confirmed in larger studies that also include women.