Conjugated Linoleic Acid Mix Research Articles

Improving obesity and lipid metabolism using conjugated linoleic acid

Conjugated linoleic acid (CLA) can prevent fatty acid accumulation induced by a high-fructose diet and improve lipid metabolism disorders in patients. We aimed to investigate the effect of CLA on obesity and lipid metabolism and its possible mechanism. Eight-month-old male BKS.Cg-Dock7m +/+ Leprdb /JNju (db/db) mice (n=12) were fed a CLA mix composed of equivalent c9, t11-CLA and t10, c12-CLA for 1 month. The effect of CLA on body weight, water and food intake, and triglyceride (TG) and total cholesterol (TC) levels was investigated. PPARα, PPARγ and CD36 expression was determined by quantitative PCR and western blotting. Additionally, the expression of these three genes was studied in HepG2 cells treated with CLA and linoleic acid. CLA treatment notably reduced the dietary and water intake of db/db mice, effectively reduced body weight, and decreased serum TG and TC levels (p<0.05). Increased expression of PPARα (p<0.05) and decreased expression of CD36 (p<0.001) were observed in the liver of mice that were fed CLA. CLA increased PPARα expression (p<0.001) and decreased PPARγ (p<0.001) and CD36 expression (p<0.01) in HepG2 cells. Our results showed that CLA can improve lipid metabolism in obese mice through upregulation of PPARα expression and downregulation of CD36 expression.

Effects of Dietary Supplementation of Conjugated Linoleic Acids and Their Inclusion in Semen Extenders on Bovine Sperm Quality.

Simple SummarySuboptimal fertility in males accounts for about two-thirds of infertility cases, thus being of serious concern for the dairy industry, where optimal fertility is fundamental for farm profitability. Although genetic defects responsible for subfertility have been identified, the role of seminal compounds on fertility remain unclear. Feeding rumen-protected isomers of conjugated linoleic acid (CLA) to dairy cows reportedly enhances circulating insulin-like growth factor I (IGF-I) levels. In breeding bulls, the IGF-I concentration in seminal plasma has been positively correlated with fertility rates. Therefore, the objective of the study was to evaluate the effect of dietary CLA supplementation and of their inclusion to the semen extender on bovine semen quality and freezability.Isomers of conjugated linoleic acid (CLA) enhances circulating insulin-like growth factor I (IGF-I) levels. Furthermore, fertility rate of breeding bulls is positively correlated to seminal plasma IGF-I concentration. Our objective was to evaluate the effect of dietary CLA supplementation and inclusion to the semen extender on bovine semen quality and freezability. Fourteen bulls, randomly assigned to control (CTL) and CLA (50 g/day) groups, were supplemented for 10 weeks. Samples were collected at Weeks −2 (before supplementation), 0, 4, 6 (during supplementation), 10, and 11 (after supplementation). Blood and seminal plasma were analyzed for IGF-I; the ejaculates were frozen in the following subgroups: CTL (no addition to semen extender), CLA c9, t11 (50 µM), CLA c9, t11 (100 µM), CLA t10, c12 (50 µM), CLA t10, c12 (100 µM), and CLA mix (50 µM each of CLA c9, t11 and CLA t10, c12). Sperm motility, morphology, viability, mitochondrial membrane potential, and reactive oxidative species were assessed. CLA supplementation decreased ejaculates’ total volume, increased sperm concentration, beat cross frequency, and decreased oxidative stress; it also increased plasma and seminal plasma IGF-I levels compared to the CTL. The inclusion of CLA c9, t11 100 µM and CLA mixture in the extender increased live spermatozoa percentage post-thawing compared to other groups. Our results show a beneficial effect of CLA supplementation on semen quality; however, further studies evaluating fertilization rates are necessary to corroborate the results.

SUN-065 Effects of Conjugated Linoleic Acid (CLA) on Insulin Resistance and BMI in Subjects with and without the Metabolic Syndrome: A Systematic Review and Meta-Analysis

*RC and RC equally contribute as the main reviewers Background: CLA supplementation has been widely used by the general population as a weight reduction agent. In-vitro and animal studies have reported beneficial metabolic effects while reports in humans have been mixed, with some even reporting adverse effects. The aim of the present study is to review and synthesize the available evidence from randomized controlled trials (RCTs) of CLA on body weight (BMI) and insulin resistance (HOMA-IR). Methods: We conducted a systematic literature search to identify studies up to December 2017. Only RCTs with CLA t10-c12 isomer or mix 50:50 CLA t10-c12 and c9-t11 as intervention on individuals with or without components of the metabolic syndrome were selected. Individual study results were pooled to obtain weighted mean differences (WMDs) with 95% confidence intervals (CI), funnel plots assessed small study effects and subgroup analysis helped explore a priori identified sources of heterogeneity. Results: A total of 24 RCTs met the inclusion criteria and 19 were eligible for meta-analysis of one or more outcomes of interest. For BMI, the combined result from 15 individual studies showed a reduction of 0.26 units (95%CI -0.47, -0.05) in the intervention group vs placebo (p=0.017). No statistically significant difference was observed from pooling 7 studies on HOMA-IR, a few of which rather indicated a negative effect. Conclusions: Our review demonstrates a weight-lowering influence of CLA. However, although the effect seems consistent, its magnitude does not convincingly suggest clinical relevance. In terms of insulin resistance, there does not seem to be any beneficial effect, and small studies showing adverse effect warrants further scrutiny.

Conjugated linoleic acid prevents age-induced bone loss in mice by regulating both osteoblastogenesis and adipogenesis

Osteoporosis (OP) can increase the risk of bone fracture and other complications, which is a major clinical problem. Previous researches have revealed that conjugated linoleic acid (CLA) can promote the bone formation. But the mechanisms are not clear. Thus, we tested the hypothesis that CLA acts on bone formation might be via mTOR Complex1 (mTORC 1) pathway by in vitro and vivo assays. We studied the effect of CLA mix on MC3T3-E1 pre-osteoblasts differentiation into osteoblasts, and bone formation under osteoporotic conditions. At the same time, 3T3-L1 pre-adipocyte with the same CLA mix concentration gradient for 8 days with adipogenic differentiation medium. We found that Alkaline phosphatase (ALP), runt-related transcription factor 2 (RUNX2) and osteocalcin (OCN) expressions of pre-osteoblasts were up-regulated. Moreover in presence of CLA, peroxisome proliferators-activated receptor γ(PPARγ) and CCAAT/enhancer-binding protein (C/EBPα) were down-regulated. Osteoporosis mice bone parameters in the distal femoral meraphysis were significantly increased compared with placebo mice. Furthermore, the phosphor-S6 (P-S6) was suppressed and phosphor-AKT (P-AKT) was up-regulated. Consistently, CLA can stimulate differentiation of osteoblasts and inhibited pre-adipocytes differentiated into adipocytes via AKT/mTORC1 signal pathway. Overall CLA thus be a suitable candidate for the treatment of patients with postmenopausal osteoporosis and obesity.

Conjugated Linoleic Acid: Potential Health Benefits as a Functional Food Ingredient.

Conjugated linoleic acid (CLA) has drawn significant attention since the 1980s for its various biological activities. CLA consists mainly of two isomers, cis-9,trans-11 and trans-10,cis-12, and the mixture of these two (CLA mix or 50:50) has been approved for food as GRAS (generally recognized as safe) in the United States since 2008. Along with its original discovery as an anticancer component, CLA has been shown to prevent the development of atherosclerosis, reduce body fat while improving lean body mass, and modulate immune and/or inflammatory responses. This review summarizes the clinical trials involving CLA since 2012; additional uses of CLA for age-associated health issues are discussed; and CLA's potential health concerns, including glucose homeostasis, oxidative stress, hepatic steatosis, and milk-fat depression, are examined. With ongoing applications to food products, CLA consumption is expected to rise and close monitoring of not only its efficacy but also its known and unknown consequences are required to ensure proper applications of CLA.

T-10, c-12 CLA Dietary Supplementation Inhibits Atherosclerotic Lesion Development Despite Adverse Cardiovascular and Hepatic Metabolic Marker Profiles

Animal and human studies have indicated that fatty acids such as the conjugated linoleic acids (CLA) found in milk could potentially alter the risk of developing metabolic disorders including diabetes and cardiovascular disease (CVD). Using susceptible rodent models (apoE−/− and LDLr−/− mice) we investigated the interrelationship between mouse strain, dietary conjugated linoleic acids and metabolic markers of CVD. Despite an adverse metabolic risk profile, atherosclerosis (measured directly by lesion area), was significantly reduced with t-10, c-12 CLA and mixed isomer CLA (Mix) supplementation in both apoE−/− (p<0.05, n = 11) and LDLr−/− mice (p<0.01, n = 10). Principal component analysis was utilized to delineate the influence of multiple plasma and tissue metabolites on the development of atherosclerosis. Group clustering by dietary supplementation was evident, with the t-10, c-12 CLA supplemented animals having distinct patterns, suggestive of hepatic insulin resistance, regardless of mouse strain. The effect of CLA supplementation on hepatic lipid and fatty acid composition was explored in the LDLr−/− strain. Dietary supplementation with t-10, c-12 CLA significantly increased liver weight (p<0.05, n = 10), triglyceride (p<0.01, n = 10) and cholesterol ester content (p<0.01, n = 10). Furthermore, t-10, c-12 CLA also increased the ratio of 18∶1 to 18∶0 fatty acid in the liver suggesting an increase in the activity of stearoyl-CoA desaturase. Changes in plasma adiponectin and liver weight with t-10, c-12 CLA supplementation were evident within 3 weeks of initiation of the diet. These observations provide evidence that the individual CLA isomers have divergent mechanisms of action and that t-10, c-12 CLA rapidly changes plasma and liver markers of metabolic syndrome, despite evidence of reduction in atherosclerosis.

Influence of different CLA isomers on insulin resistance and adipocytokines in pre-diabetic, middle-aged men with PPARγ2 Pro12Ala polymorphism

Conjugated linoleic acids (CLAs) are natural PPARγ ligands, which showed conflicting effects on metabolism in humans. We examined metabolic effects of different isomers of CLA in subjects with PPARγ2 Pro12Ala polymorphisms. A total of 35 men underwent four intervention periods in a crossover study design: subjects with either genotypes received c9, t11 CLA or t10, c12 CLA, a commercially available 1:1 mix of both isomers or reference oil (linoleic acid (LA)). Adipocytokines, insulin, glucose and triglycerides were assessed in the fasting state and after a standardized mixed meal. Across all genotypes, there was a significant (p=0.025) CLA treatment effect upon postprandial (pp) HOMA-IR values, with c9, t11 CLA and CLA isomer mix improving, but t10, c12 CLA isomer worsening. In Ala12Ala subjects, the t10, c12 isomer caused weight gain (p=0.03) and tended to increase postprandial insulin levels (p=0.05). In Pro12Pro subjects, t10, c12 resulted in reduction in waist circumference (p=0.03). The comparison of the different genotype groups revealed statistically different changes in fasting and postprandial insulin, HOMA-IR and leptin after intervention. c9, t11 CLA and the commercial CLA mix showed beneficial effects on insulin sensitivity compared with LA, while t10, c12 CLA adversely affects body weight and insulin sensitivity in different PPAR genotypes. CLA isomers have different effects on metabolism in Ala and Pro carriers.

Differential effects of conjugated linoleic acid isomers in insulin-resistant female C57Bl/6J mice

Obesity is associated with a high risk of developing diabetes and cardiovascular disease. Therefore, management of body weight to prevent obesity remains as an important priority. The present investigation addresses the effects of conjugated linoleic acid (CLA) isomers on body weight and composition of body fat in female C57Bl/6J mice. To investigate the differential effects of individual CLA isomers and their mixture on changes in lean mass, fat mass, glucose and insulin, 6-month-old female C57BL/6J mice were fed with 10% corn oil (CO) as a dietary fat source and either supplemented with purified cis 9, trans 11 (c9t11) CLA (0.5%) or trans 10, cis 12 (t10c12) CLA (0.5%) and/or their mixture (50:50) for 6 months. As a result of 6 months' dietary intervention, both the t10c12-CLA and CLA mix showed increased lean mass and reduced fat mass compared to the CO and c9t11-CLA groups. Insulin resistance was, however, increased in t10c12-CLA and CLA mix-fed groups based on the results of homeostasis model assessment (HOMA), the revised quantitative insulin-sensitivity check index (R-QUICKI) and also with intravenous glucose tolerance test (IVGTT). In conclusion, long-term feeding of the major CLA isomers in 12-month-old C57Bl/6J mice revealed a contrasting effect on fat mass, glucose and insulin metabolism. The t10c12 isomer is found to reduce the fat mass and increase the lean mass but significantly contributed to increase insulin resistance and liver steatosis, whereas c9t11 isomer prevented the insulin resistance.

Higher immunoglobulin production in conjugated linoleic acid-supplemented rats during gestation and suckling

Conjugated linoleic acid (CLA) has been reported to exert beneficial physiological effects on body composition and the immune system. However, little information is available on the influence of CLA on immune function during early life periods. The present study evaluates the effect of feeding an 80:20 mixture of cis-9, trans-11- and trans-10, cis-12-CLA isomers during gestation and suckling on the systemic immune response of weaned Wistar rats. Pups received dietary CLA from dams through the placental barrier and during suckling by breast milk (group A) or by oral administration (group B). Pups from group C only received CLA during suckling by oral administration. Group D constituted the reference group. Milk from dams fed the CLA diet had a high content of CLA and higher IgA and IgG concentrations than rats fed the standard diet. The plasma of pups from groups A, B and C showed six, twelve and nine times higher content of the cis-9, trans-11-CLA isomer than that of the group D pups. Rats from group A exhibited higher serum IgG concentrations than rats from the rest of the groups (22.14 (SEM 2.14) v. about 5 mg/ml; P < 0.05), whereas rats from groups A and B showed approximately 2-fold higher splenocyte IgM production than rats from groups C and D. However, CLA supplementation did not influence significantly the splenocyte proliferative response or cytokine secretion. Supplementation during gestation and suckling with an 80:20 cis-9, trans-11-trans-10, cis-12 CLA mix enhances the production of the main in vivo and in vitro Ig isotypes in Wistar rats.

Conjugated linoleic acid (CLA) prevents age associated skeletal muscle loss in mice by maintaining redox balance during aging

Age related skeletal muscle sarcopenia is a major health problem. Currently, there is no safe and effective therapies that selectively increase skeletal muscle mass. Previously, we have shown that CLA maintains higher skeletal muscle mass in mice. This study was designed to elucidate the molecular mechanisms of muscle loss prevention by CLA using 12 mo old C57BL/6 mice fed 10% corn oil (CO) or a diet supplemented with 0.5% c9t11 CLA (CLA 1), t10c12 CLA (CLA 2) or c9t11 CLA+t10c12 CLA (CLA mix) for 6 months. Dual energy X‐ray absorptiometry (DXA) scan was performed at baseline, and end of dietary intervention. CLA 2 and CLA mix groups showed significantly higher muscle mass as compared to CO and CLA 1 groups by DXA and muscle wet weight. Production of muscle mitochondrial ATP, and H2O2 as reactive oxygen species and muscle antioxidant enzymes (catalase and glutathione peroxidase) has been analyzed. Enhanced production of ATP, and antioxidant enzymes accompanied by slight increase in H2O2 level was noted in CLA 2 and CLA mix groups as compared to that of CO and CLA 1 groups. Finally, we have analyzed serum malondialdehyde (MDA) level. The lower level of serum MDA in CLA 2 and CLA mix groups indicate less oxidative stress in these groups. These data suggest that CLA 2 and CLA mix groups may preserve muscle mass by enhancing muscle mitochondrial energy production as well as by maintaining the redox balance during aging. Research support: NIH

Conjugated Linoleic Acid (CLA) Inhibits Expression of the Spot 14 (THRSP) and Fatty Acid Synthase Genes and Impairs the Growth of Human Breast Cancer and Liposarcoma Cells

Spot 14 (THRSP, S14) is a nuclear protein involved in the regulation of genes required for fatty acid synthesis in normal and malignant mammary epithelial and adipose cells. Harvatine and Bauman (1) reported that conjugated linoleic acid (CLA) inhibits S14 gene expression in bovine mammary and mouse adipose tissues and reduces milk fat production in cows. We hypothesized that CLA inhibits S14 gene expression in human breast cancer and liposarcoma cells and that this will retard their growth. Exposure of T47D breast cancer cells to a mixture of CLA isomers reduced the expression of the S14 and fatty acid synthase (FAS) genes. The mixture caused a dose-related inhibition of T47D cell growth, as did pure c9, t11 and t10, c12-CLA, but not linoleic acid. Similar effects were observed in MDA-MB-231 breast cancer cells. Provision of 8 μM palmitate fully (CLA mix, t10, c12-CLA) or partially (c9, t11-CLA) reversed the antiproliferative effect in T47D cells. CLA likewise suppressed levels of S14 and FAS mRNAs in liposarcoma cells and caused growth inhibition that was prevented by palmitic acid. CLA did not affect the growth of nonlipogenic HeLa cells or human fibroblasts. We conclude that as in bovine mammary and mouse adipose cells, CLA suppresses S14 and FAS gene expression in human breast cancer and liposarcoma cells. Rescue from the antiproliferative effect of CLA by palmitic acid indicates that reduced tumor lipogenesis is a major mechanism for the anticancer effects of CLA

Regulation of adhesion molecule expression in human endothelial and smooth muscle cells by omega-3 fatty acids and conjugated linoleic acids: Involvement of the transcription factor NF- κB?

We previously showed conjugated linoleic acids (CLA) inhibited TNF- α-induced monocyte (THP-1) adhesion to human umbilical vein endothelial cells (HUVEC) in vitro which involved an increase in platelet activating factor (PAF). Here we show adhesion molecule (ADM) regulation by fatty acids and the differing role of nuclear factor kappa B (NF- κB) activation in HUVEC and vascular smooth muscle cells (vSMC). CLA and omega-3 long-chain polyunsaturated fatty acids (PUFA) (FA) reduced TNF-ά-induced expression of ADMs (intercellular adhesion molecule-1 (ICAM-1); vascular cell adhesion molecule-1 (VCAM-1) but not E-selectin) on HUVEC and vSMC to different extents depending on FA type and concentration, cell type and method of analysis. I κBά phosphorylation in HUVEC and vSMC and transient transfection with NF- κB-luciferase reporter plasmid (HUVEC only) indicated differential NF- κB involvement during FA modulation ( cis-9, trans-11; trans-10, cis-12 and a 50:50 mix of both CLA isomers; eicosapentaenoic acid (EPA); docosahexaenoic acid (DHA)). TNF- α-induced ADM expression in both cell types by 2–10-fold. In HUVEC, CLA t10, c12 and CLA mix (50:50 mixture of CLA c9, t11 and t10, c12) and EPA and DHA reduced ICAM-1 expression (15–35%) at 12.5, 25 and/or 50 μM. VCAM-1 expression was reduced by 25 μM t10, c12 isomer and mix; omega-3 PUFA and other concentrations of CLA and TNF- α-induced E-selectin expression were unaffected. TNF α-induced inhibitor kappa B (I κB) phosphorylation was biphasic peaking at 5 min in both cell types and 60 and 120 min in HUVEC and SMC, respectively. I κB α phosphorylation and NF- κB activity was reduced (29% and 30%, respectively) by 25 μM CLA mix. n-3 PUFA did not reduce I κB α phosphorylation or NF- κB activity but reduced ADM expression. We show that n-3 PUFA and CLA reduce expression of ADM on HUVEC and vSMC. This reflected reduced adherence of monocytes to HUVEC previously reported by our group. Reduction of ICAM-1 and VCAM-1 protein expression by n-3 PUFA was less dependent on the NF- κB pathway than reduction by CLA which reflected the parallel attenuation of NF- κB activity. This indicated involvement of other transcription factors (i.e. AP-1) in the FA regulation of ADM expression and has, to our knowledge, not been previously reported.

Potentiation of the anti-tumour effect of docetaxel by conjugated linoleic acids (CLAs) in breast cancer cells in vitro

Response rates of tumours to docetaxel (DOCT) are 45–60% in advanced breast cancer but problems associated with side effects, drug resistance and high costs occur. Conjugated linoleic acids (CLAs) also have anti-tumorigenic activity that elicits similar changes in oncogene expression to DOCT and could augment DOCT efficacy. CLA isomers appear to differ in cytotoxicity toward cancer cells. Effects of two CLA isomers on cytotoxicity of DOCT in breast cancer cells (MCF-7; MDA-MB-231) in vitro were assessed. Cells were incubated up to 72 h with 40 μM each of LA or CLA isomers ( cis-9, trans-10 CLA, or trans-10, cis-12 CLA) or a 50:50 isomer mix, alone or with DOCT (0–64 μM); a pilot study determined IC 50 and IC 70 concentrations. Treatments were concurrent (CLA and DOCT together) or sequential (CLA then DOCT). MTT assay determined cell viability. Trans-10, cis-12 CLA was the most effective fatty acid ( P<0.001) and increased with treatment time. IC 50 and IC 70 concentrations of DOCT were determined, concurrently or sequentially, with and without fatty acids, in the two cell types. Concurrent treatment with trans-10, cis-12 CLA and DOCT augmented inhibition of cell growth in one or both cell lines (decreased IC 50 and IC 70 in MCF-7; P<0.05 but only IC 50 in MDA-MB-231; P<0.05). CLA mix reduced IC 50 and IC 70 in MDA-MB-231 ( P<0.001) but not in MCF-7. Cis-9, trans-11 CLA and LA had no effect. Sequential treatment with CLAs then DOCT reduced IC 50 and IC 70 in MCF-7 but not in MDA-MB-231. The latter had increased IC 50 and IC 70 with LA treatment ( P<0.05) and increased IC 70 with c is-9, trans-11 CLA ( P<0.05) with sequential but not concurrent treatment. Longer pre-incubation times with trans-10, cis-12 CLA (24–72 h) elicited greater reductions in IC 50 and IC 70 in MCF-7 cells. Results show that CLA isomers augment anti-tumour effects of docetaxel in breast cancer cells and suggest possible dual treatment regimens.

Conjugated Linoleic Acid Attenuates Cyclooxygenase-2 Transcriptional Activity via an Anti-AP-1 Mechanism in MCF-7 Breast Cancer Cells

Overexpression of cyclooxygenase-2 (COX-2) is regarded as a causative factor in the onset of tumorigenesis of the breast. In this study, we investigated the effects of conjugated linoleic acid (CLA) on COX-2 transcription in MCF-7 breast cancer cells. Results of transient transfection studies revealed that treatment with a CLA mix or selected isomers (c9, t11-CLA; t10, c12-CLA) at concentrations ranging from 20 to 80 micromol/L, attenuated COX-2 transcription induced by the proinflammatory agent 12-O-tetradecanoylphorbol-13-acetate (TPA). In addition, the CLA mix inhibited TPA-induced activity of the collagenase-1 promoter. Using electrophoretic mobility shift assays, we found that the CLA mix reduced TPA-induced recruitment of nuclear proteins to a cAMP response element (CRE) in the COX-2 promoter and a consensus TPA-responsive element (TRE) in the collagenase-1 promoter. Both CRE and TRE are binding sites for activator protein-1 (AP-1). Binding studies revealed that the t10, c12-CLA isomer was more effective than the CLA mix or c9, t11-CLA in reducing binding of cJun to either the COX-2 CRE or collagenase-1 TRE, whereas linoleic acid increased binding to both elements. Overexpression of the AP-1 member, c-Jun, reversed the inhibitory effects of the CLA mix on COX-2 transcription, and restored binding of nuclear proteins to the CRE and TRE. Collectively, these results suggest that CLA represses AP-1-mediated activation of COX-2 transcription.

Gender differences in the cardiac response to dietary conjugated linoleic acid isomers

The present study was undertaken to assess the heart function, by the in vivo catheterization technique, of healthy male and female Sprague-Dawley rats fed different conjugated linoleic acid (CLA) isomers, (cis-9, trans-11 (c9,t11) and trans-10, cis-12 (t10,c12)) individually and in combination (50:50 mix as triglyceride or fatty acids) from 4 to 20 weeks of age. Whereas the triglyceride form of the CLA isomer mix lowered the heart rate, the rate of contraction (+dP/dt) and rate of relaxation (-dP/dt), systolic and diastolic pressures, mean arterial pressure, and the left ventricular systolic pressure were higher in male rats as compared with all the other dietary groups. In contrast, there were no significant effects in the cardiac function of the female rats in response to the CLA isomer mix in triglyceride form. Whereas the heart rate, +dP/dt, and left ventricular systolic pressure were lower in male rats fed the t10,c12 CLA isomer alone, the heart rate of the female rats was higher, but the systolic pressure, +dP/dt, and mean arterial pressure were lower compared with the control group. Also, the left ventricular end-diastolic pressure was specifically higher in the female rats in response to free fatty acids-containing CLA mix. Furthermore, an additive effect of the free fatty acids-containing CLA mix was seen in the +dP/dt and -dP/dt of female rats compared with the control group. These results indicate that CLA isomers exert differential effects on heart function and suggest the need for a complete evaluation of the benefits, interactions, and potential side effects of each isomer.

Dietary trans octadecenoic acids upregulate the liver gene encoding Peroxisome Proliferator-Activated Receptor-α in transition dairy cows

Effects of feeding calcium salts of conjugated linoleic acid (CLA) or trans octadecenoic acids (trans 18:1) on lipid metabolism and hepatic contents of mRNA encoding carnitine palmitoyltransferase 1 (CPT1), microsomal triglyceride transfer protein (MTP) and peroxisome proliferator-activated receptor alpha (PPARalpha) were examined in 15 early post-partum Holstein cows. Dietary treatments were initiated at approximately 4 weeks prior to expected calving dates and continued for 7 weeks post partum. Treatments prepartum consisted of 1) a basal diet (Control), 2) basal diet+150 g/d of CLA mix (CLA), or 3) basal diet+150 g/d of trans 18:1 mix (TRANS). Intakes of calcium salts of CLA and trans 18:1 mixes were adjusted to 225 g/d during the 7-week postpartum treatment period. Blood samples were collected at weeks 1, 2 and 4 post partum and plasma was harvested immediately for subsequent hormone and metabolite assays. Concentrations of insulin, insulin-like growth factor-I (IGF-I), and leptin in blood did not vary among cows fed the three diets. Plasma nonesterified fatty acid (NEFA) concentrations decreased between weeks 1 and 4 of lactation and were lower in cows fed the diet supplemented with trans 18:1 than in those fed a control diet at week 2 post partum. Periparturient fat supplementation had no detectable effects on CPT1 mRNA content in the liver. Steady-state concentration of MTP mRNA in the liver was greater in the TRANS treatment group than in the control group at week 1 postpartum. Feeding trans 18:1 supplements to transition dairy cows upregulated hepatic PPARalpha mRNA content during the first month of lactation. Under the present experimental conditions, dietary CLA had minimal effects on plasma and hepatic lipid metabolite concentrations in early lactation Holstein cows. Results indicate that dietary trans fatty acids may affect liver lipid metabolism in post-partum dairy cows through alterations in PPARalpha gene expression.

Effect of conjugated linoleic acid isomers on insulin resistance and mRNA levels of genes regulating energy metabolism in high-fat–fed rats

Objective We investigated the effects of specific conjugated linoleic acid (CLA) isomers on glucose metabolism and insulin resistance and on mRNA levels of genes important in glucose and lipid metabolism. Methods Sprague-Dawley rats were fed for 8 wk on a high-fat diet (45% kcal from fat) or one of three CLA-supplemented diets (1% CLA) containing differing isomers of CLA, including a mixture of CLAs (CLA mix), cis-9, trans-11-CLA (C9,T11-CLA), or trans-10, cis-12-CLA (T10,C12-CLA). Results Compared with the high-fat group, all the CLA groups had enhanced glucose tolerance. Insulin resistance index was significantly lower in the CLA-treated groups. No significant difference could be observed in the level of serum lipids between groups and in the activities of phosphoenolpyruvate carboxylase, glucose-6-phosphatase, and glucokinase. However, C9,T11-CLA and T10,C12-CLA significantly increased acyl coenzyme A oxidase mRNA in skeletal muscle. In addition, C9,T11-CLA increased hepatic acyl coenzyme A oxidase mRNA and skeletal muscle uncoupling protein-2 mRNA. The CLA mix showed intermediate effects on the levels of these genes. Conclusions The addition of all types of CLA to Sprague-Dawley rats fed a high-fat diet can decrease insulin resistance. Possible mechanisms are increased fat oxidation and energy expenditure by increasing acyl coenzyme A oxidase and uncoupling protein-2 mRNA in the liver and/or skeletal muscle.

Conjugated linoleic acid isomer effects in atherosclerosis: Growth and regression of lesions

Conjugated linoleic acid (CLA), a mixture of positional and geometric isomers of octadecadienoic acid, has been shown to inhibit experimentally induced atherosclerosis in rabbits and also to cause significant regression of pre-established atheromatous lesions in rabbits. The two major CLA isomers (cis9,trans11 and trans10,cis12), now available at 90% purity, have been tested individually for their anti-atherogenic or lesion regression potency. The two major isomers and the mixture were fed for 90 d to rabbits fed 0.2% cholesterol. Atherosclerosis was inhibited significantly by all three preparations. The two CLA isomers and the isomer mix were also fed (1.0%) as part of a cholesterol-free diet for 90 d to rabbits bearing atheromatous lesions produced by feeding an atherogenic diet. A fourth group was maintained on a cholesterol-free diet. On the CLA-free diet atherosclerosis was exacerbated by 35%. Reduction of severity of atheromatous lesions was observed to the same extent in all three CLA-fed groups. The average reduction of severity in the three CLA-fed groups was 26 +/- 2% compared with the first control (atherogenic diet) and 46 +/- 1% compared with the regression diet. Insofar as individual effects on atherosclerosis were concerned, there was no difference between the CLA mix and the cis9,trans11 and trans10,cis12 isomers. They inhibit atherogenesis by 50% when fed as a component of a semipurified diet containing 0.2% cholesterol; and when fed as part of a cholesterol-free diet, they reduce established lesions by 26%. Reduction of atheromata to the observed extent by dietary means alone is noteworthy.

Modulation of nitric oxide and 6-keto-prostaglandin F(1alpha) production in bovine aortic endothelial cells by conjugated linoleic acid.

Conjugated linoleic acid (CLA) refers to a group of polyunsaturated fatty acids that exist as positional (18:2) and stereo (cis/trans) isomers of conjugated dienoic octadecadienoate. Reports consistently indicate that CLA may inhibit both the onset and progression of atherosclerosis, via an as yet unknown mechanism(s). In an effort to identify the putative biochemical effects of CLA on bovine aortic endothelial cells (BAECs), the authors examined both the temporal and dose-dependent effects of a commercial CLA isomeric mixture on the expression and enzymatic function of endothelial nitric oxide synthase (eNOS) and cyclooxygenase-I/II (COX-I/II) in these cells. Initial investigations indicated that CLA mix (0 to 10 microg/mL, 0 to 24 h) failed to regulate either the expression or activity of eNOS in BAECs under basal conditions. Pretreatment of BAECs with CLA mix (10 microg/mL) for either 3 or 24 h, followed by incubation with 5 microM bradykinin (BK) for 3 h, however, increased BK-stimulated nitrite release by 2.4 +/- 0.6- and 3.0 +/- 0.4-fold, respectively, more than control cells (BK-stimulation without CLA pretreatment). Under basal conditions, CLA mix (10 microg/mL, 0 to 24 h) had no significant effect on either COX-I or COX-II expression, genes that could be readily induced in response to hemodynamic stimuli. CLA could, however, significantly attenuate BAEC release of 6-keto-prostaglandin F(1alpha) (6k-PGF(1alpha)), a stable breakdown product of prostaglandin I2 (PGI2) within the cyclooxygenase pathway, in a dose- and time-dependent manner. In conclusion, therefore, the results suggest that CLA may potentiate agonist-stimulated eNOS activation whilst attenuating COX-dependent PGI2 synthesis in BAECs. This ability to increase agonist-stimulated nitric oxide (NO) levels, whilst reducing production of inflammatory mediators within vascular ECs, supports a putative atheroprotective role for CLA and provides an important biochemical insight into its purported ability to modulate endothelium-mediated vascular homeostasis.

Isomer-specific effects of conjugated linoleic acid on lipid peroxidation in humans: regulation by alpha-tocopherol and cyclo-oxygenase-2 inhibitor.

We have found previously that supplementation with conjugated linoleic acid (CLA) induces lipid peroxidation and inflammation in humans as indicated by an increase of 8-iso-prostaglandin F2alpha (PGF2alpha) and 15-keto-dihydro-PGF2alpha respectively. The present study was undertaken firstly to study the regulatory mechanisms behind these effects, and secondly to see if these effects are specific to different isomers of CLA. Sixty healthy men and women, divided into six groups, were given a cyclo-oxygenase (COX)-2 inhibitor (rofecoxib; 12 mg/day), alpha-tocopherol (200 mg/day) or neither treatment (control group) over a period of 6 weeks. During the last 4 weeks, three groups were given a CLA preparation (3.5 g/day) mainly containing the isomers cis-9, trans-11 and trans-10, cis-12 (CLA mix), and the three other groups a CLA preparation mainly containing the isomer trans-10, cis-12 (CLA 1012; 4.0 g/day). Treatment with alpha-tocopherol or COX-2 inhibitor did not alter the basal urinary levels of either 8-iso-PGF2alpha or 15-keto-dihydro-PGF2alpha. Both CLA preparations induced an increase in 8-iso-PGF2alpha and 15-keto-dihydro-PGF2alpha in the urine, with a larger increase being found in the CLA 1012 group. Treatment with the COX-2 inhibitor suppressed the increase in urinary 15-keto-dihydro-PGF2alpha in the CLA 1012 group, but not in the CLA mix group. Neither the COX-2 inhibitor nor alpha-tocopherol had any effect on 8-iso-PGF2alpha levels after supplementation with CLA. The CLA-induced production of PGF2alpha metabolites is probably partially mediated by COX-2. Levels of the induced lipid peroxidation may be dependent on the isomeric property of CLA.