Conjugated linoleic acid reduces early aortic atherosclerosis greater than linoleic acid in hypercholesterolemic hamsters

The effect of conjugated linoleic acid supplementation in comparison with omega-6 and omega-9 on lipid profile: a graded, dose-response systematic review and meta-analysis of randomized controlled trials

Conjugated linoleic acid (CLA) is a geometrical isomer of linoleic acid, which has anti-inflammatory, anti-diabetic, anti-cancer, and anti-obesity properties. However, the studies reported inconstant results about the CLA-related effects on lipid profiles. As a result, meta-analysis and systematic review were performed to survey the CLA supplementation-related effect on lipid profile including high-density lipoprotein (HDL), low-density lipoprotein (LDL), total cholesterol (TC), and triglycerides (TG). To identify the relevant research, a systematic comprehensive search was initiated on the medical databases such as Scopus and PubMed/Medline until December 2022. The overall effect size was estimated by weighted mean difference (WMD) and 95% confidence interval (CI) in a random effect meta-analysis. In the final quantitative analysis, the meta-analysis considered 35 randomized controlled trials (RCTs) with 1,476 participants (707 controls and 769 cases). The pooled results demonstrated that CLA supplementation, compared with olive oil, significantly increased serum TG levels (WMD: 0.05 mmol/L; 95% CI: 0.01 to 0.1; p = 0.04; I2 = 0.0%, p = 0.91). With regard to TC level, CLA supplementation compared with placebo significantly reduced TC concentrations (WMD: -0.08 mmol/L; 95% CI: -0.14 to -0.02; p < 0.001; I2 = 82.4%). Moreover, the non-linear dose-response analysis indicated a decreasing trend of TC serum level from the 15th week of CLA supplementation compared with olive oil (Pnon-linearity = 0.01). The present meta-analysis and systematic review of 35 RCTs showed that the CLA intervention was able to raise the level of TG in comparison to olive oil; however, it can decrease TC level compared with placebo and olive oil.

Dietary supplementation of phytoncide and soybean oil increases milk conjugated linoleic acid and depresses methane emissions in Holstein dairy cows

The objective of this study was to determine whether adding phytoncide oil (PO) and soybean oil (SBO) to the dairy cow diet could increase milk conjugated linoleic acid (CLA) and depress methane (CH4) emissions in Holstein dairy cows. Rumen fermentation was conducted at four levels of SBO (0, 1, 2, and 4%, on DM basis) and two levels of PO (0 and 0.1%, on DM basis) with in vitro experiment. To evaluate blood parameters, fecal microbe population, milk yield and fatty acid compositions, and CH4 production, in vivo experiment was conducted using 38 Holstein dairy cows divided into two groups of control (fed TMR) and treatment (fed TMR with 0.1% PO and 2% SBO as DM basis). In the in vitro study (Experiment 1), PO or SBO did not affect rumen pH. However, SBO tended to decrease ruminal ammonia-N (p = 0.099). Additionally, PO or SBO significantly decreased total gas production (p = 0.041 and p = 0.034, respectively). Both PO and SBO significantly decreased CH4 production (p < 0.05). In addition, PO significantly increased both CLA isomers (c9, t11 and t10, c12 CLA) (p < 0.001). Collectively, 0.1% PO and 2% SBO were selected resulting in most effectively improved CLA and decreased CH4 production. In the in vivo study (Experiment 2), 0.1% PO with 2% SBO (PSO) did not affect complete blood count. However, it decreased blood urea nitrogen and magnesium levels in blood (p = 0.021 and p = 0.01, respectively). PSO treatment decreased pathogenic microbes (p < 0.05). It increased milk yield (p = 0.017) but decreased percentage of milk fat (p = 0.013) and MUN level (p < 0.01). In addition, PSO treatment increased both the concentration of CLA and PUFA in milk fat (p < 0.01). Finally, it decreased CH4 emissions from dairy cows. These results provide compelling evidence that a diet supplemented with PSO can simultaneously increase CLA concentration and decrease CH4 production with no influence on the amount of milk fat (kg/day) in Holstein dairy cows.

Multiple omics analysis reveals the regulation of SIRT5 on mitochondrial function and lipid metabolism during the differentiation of bovine preadipocytes

Preadipocyte differentiation represents a critical stage in adipogenesis, with mitochondria playing an undeniable pivotal role. Given the intricate interplay between transcription and metabolic signaling during adipogenesis, the regulation of sirtuin 5 (SIRT5) on mitochondrial function and lipid metabolism was revealed via multiple omics analysis. The findings suggest that SIRT5 plays a crucial role in promoting mitochondrial biosynthesis and maintaining mitochondrial function during preadipocyte differentiation. Moreover, SIRT5 modulates the metabolic levels of numerous bioactive substances by extensively regulating genes expression associated with differentiation, energy metabolism, lipid synthesis, and mitochondrial function. Finally, SIRT5 was found to suppress triacylglycerols (TAG) accumulation while enhancing the proportion and diversity of unsaturated fatty acids, and providing conditions for the expansion and stability of membrane structure during mitochondrial biosynthesis through numerous gene regulations. Our findings provide a foundation for the identification of crucial functional genes, signaling pathways, and metabolic substances associated with adipose tissue differentiation and metabolism.

Normal-Fat vs. High-Fat Diets and Olive Oil vs. CLA-Rich Dairy Fat: A Comparative Study of Their Effects on Atherosclerosis in Male Golden Syrian Hamsters

The relationship between milk fat intake (because of its high saturated fatty acid content) and the risk of suffering from cardiovascular diseases remains controversial. Thus, Golden Syrian hamsters were fed two types of fat-sheep milk fat that was rich in rumenic (cis9,trans11-18:2) and vaccenic (trans11-18:1) acids and olive oil-and two doses (a high- or normal-fat diet) for 14 weeks, and markers of lipid metabolism and atherosclerosis evolution were analyzed. The results revealed that the type and percentage of fat affected most plasma biochemical parameters related to lipid metabolism, while only the expression of five (CD36, SR-B1, ACAT, LDLR, and HMG-CoAR) of the studied lipid-metabolism-related genes was affected by these factors. According to aortic histology, when ingested in excess, both fats caused a similar increase in the thickness of fatty streaks, but the high-milk-fat-based diet caused a more atherogenic plasma profile. The compositions of the fats that were used, the results that were obtained, and the scientific literature indicated that the rumenic acid present in milk fat would regulate the expression of genes involved in ROS generation and, thus, protect against LDL oxidation, causing an effect similar to that of olive oil.

Role of Phaseolus vulgaris L. in the Prevention of Cardiovascular Diseases-Cardioprotective Potential of Bioactive Compounds

In terms of safe and healthy food, beans play a relevant role. This crop belongs to the species of Phaseolusvulgaris L., being the most consumed legume worldwide, both for poor and developed countries, the latter seek to direct their diet to healthy feeding, mainly low in fat. Phaseolus vulgaris L. stands out in this area-an important source of protein, vitamins, essential minerals, soluble fiber, starch, phytochemicals, and low in fat from foods. This species has been attributed many beneficial properties for health; it has effects on the circulatory system, immune system, digestive system, among others. It has been suggested that Phaseolus vulgaris L. has a relevant role in the prevention of cardiovascular events, the main cause of mortality and morbidity worldwide. Conversely, the decrease in the consumption of this legume has been related to an increase in the prevalence of cardiovascular diseases. This review will allow us to relate the nutritional level of this species with cardiovascular events, based on the correlation of the main bioactive compounds and their role as cardiovascular protectors, in addition to revealing the main mechanisms that explain the cardioprotective effects regulated by the bioactive components.

Conjugated Fatty Acids in Muscle Food Products and Their Potential Health Benefits: A Review

Conjugated fatty acids (CFAs) are a group of positional and geometric isomers of polyunsaturated fatty acids (PUFAs) with conjugated double bonds. There are several subgroups of CFAs including conjugated linoleic acids (CLAs), conjugated linolenic acids (CLNAs), conjugated eicosapentaenoic acids (CEPAs), and conjugated docosahexaenoic acids (CDHAs). CFAs, especially CLAs, have been studied in recent years both for their health benefits and factors that affect their level in muscle food products. CFAs have been reported in numerous studies as having antitumor, antiobesity, antidiabetes, anticardiovascular disease, and modulating immune system effects. These biological activies are involved in changes of lipid peroxidation and energy expenditure, as well as inhibitory effects on the hormone receptor, lipid metabolism, lipoprotein lipase activity, and adiponectin production. A large body of studies has revealed that the diet, processing, storage conditions, slaughter season, and age are common factors that affect CFA content in muscle food products, as detailed in this review. Recommendations are made regarding animal farming and meat product processing to obtain high CFA content meat products and to optimize the benefits of CFA for health promotion.

Physiological Properties of Conjugated Linoleic Acid and Implications for Human Health

Conjugated linoleic acid (CLA) refers to a mixture of positional and geometric dienoic isomers of linoleic acid found naturally in animal products of ruminant sources. Recent interest in CLA research stems from the well-documented anticarcinogenic, antiatherogenic, antidiabetic, and antiobesity properties of CLA in rodents. However, there has been very little published human research on CLA. This review discusses the physiologic properties of CLA and their potential implications for human health.

Dietary trans-10, cis-12-conjugated linoleic acid alters fatty acid metabolism and microbiota composition in mice

The main aim of the present study was to investigate the effects of dietary trans-10, cis-12-conjugated linoleic acid (t10c12-CLA) on intestinal microbiota composition and SCFA production. C57BL/6 mice (n 8 per group) were fed a standard diet either supplemented with t10c12-CLA (0·5 %, w/w) (intervention) or with no supplementation (control), daily for 8 weeks. Metabolic markers (serum glucose, leptin, insulin and TAG, and liver TAG) were assessed by ELISA commercial kits, tissue long-chain fatty acids and caecal SCFA by GC, and microbial composition by 16S rRNA pyrosequencing. Dietary t10c12-CLA significantly decreased visceral fat mass (P< 0·001), but did not affect body weight (intervention), when compared with no supplementation (control). Additionally, lipid mass and composition were affected by t10c12-CLA intake. Caecal acetate, propionate and isobutyrate concentrations were higher (P< 0·05) in the t10c12-CLA-supplemented group than in the control group. The analysis of the microbiota composition following 8 weeks of t10c12-CLA supplementation revealed lower proportions of Firmicutes (P= 0·003) and higher proportions of Bacteroidetes (P= 0·027) compared with no supplementation. Furthermore, t10c12-CLA supplementation for 8 weeks significantly altered the gut microbiota composition, harbouring higher proportions of Bacteroidetes, including Porphyromonadaceae bacteria previously linked with negative effects on lipid metabolism and induction of hepatic steatosis. These results indicate that the mechanism of dietary t10c12-CLA on lipid metabolism in mice may be, at least, partially mediated by alterations in gut microbiota composition and functionality.

Non-fat milk solids attenuate hypercholesterolemic effect of conjugated linoleic acid

The present study instigates the notion that non-fat milk has a beneficial effect on hypercholesterolemia caused by dietary conjugated linoleic acid (CLA). Two groups of mice (6 per group) were fed synthetic CLA (predominantly a mixture of t10, c12 and c9, t11 isomers) at 1 % level in the diet with or without skim milk powder (SMP). Another group (control) was fed a similar diet without CLA and SMP. The study was conducted for 60 days (d). Daily feed intake and weekly body weight were recorded. Plasma lipid profile was determined monthly. At the conclusion of experiment, animals were sacrificed and liver tissue was removed to assay cholesterol and triacylglycerols (TAG). Following 60 day feeding, the plasma total cholesterol content increased significantly in CLA group (218 mg/dl) than in control group (167 mg/dl), while in CLA + SMP group (fed non-fat milk solids along with CLA), it was similar to that in control group. The fractions of high density lipoproteins (HDL) and low density lipoprotein + very low density lipoprotein (LDL + VLDL) cholesterol as well as triacylglycerols (TAG) in plasma increased in CLA group, but in CLA + SMP group it remained similar to the control levels. Thus, it is concluded that dietary CLA increases plasma cholesterol and TAG contents in mice on normocholesterolemic diet and the inclusion of non-fat milk solids reverses this effect.

Effect of supplementation with an 80:20 cis9,trans11 conjugated linoleic acid blend on the human platelet proteome

SCOPE

The dietary fatty acid cis9,trans11 conjugated linoleic acid (cis9,trans11 CLA) has been shown to modify the function of endothelial cells, monocytes, and platelets, all of which are involved in the development of atherosclerosis. Potential mechanisms for the platelet effects have not been assessed previously. In this study, we assessed how supplementation of the diet with an 80:20 cis9,trans11 CLA blend affects the platelet proteome.

METHODS AND RESULTS

In a double-blind, randomized, placebo-controlled, parallel-group trial, 40 overweight but apparently healthy adults received either 4 g per day of cis9,trans11 CLA-enriched oil or placebo oil, consisting of palm oil and soybean oil, for 3 months. Total platelet proteins were extracted from washed platelets, separated using two-dimensional gel electrophoresis and differentially regulated protein spots were identified by LC-ESI-MS/MS. Supplementation with the CLA blend, compared with placebo, resulted in significant alterations in levels of 46 spots (p < 0.05), of which 40 were identified. Network analysis revealed that the majority of these proteins participate in regulation of the cytoskeleton and platelet structure, as well as receptor action, signaling, and focal adhesion.

CONCLUSION

The platelet proteomics approach revealed novel insights into regulation of cellular biomarkers of atherogenic and thrombotic pathways by an 80:20 cis9,trans11 CLA blend.

A multi-gene analysis strategy identifies metabolic pathways targeted by trans-10, cis-12-conjugated linoleic acid in the liver of hamsters

In mice, hepatic functions can be greatly affected by dietary trans-10, cis-12-conjugated linoleic acid (CLA). However, this phenomenon has been less documented in hamsters. In the present study, male hamsters were fed two doses of the trans-10, cis-12-CLA (0.5 and 1%, w/w diet) or linoleic acid (0.5%) for 6 weeks. The effects on the liver were examined by measuring the expression of thirty-six genes representing key metabolic pathways. CLA-responsive genes and their relationships with physiological outcomes were examined by a multivariate analysis procedure. Compared with control hamsters, those receiving either 0.5 or 1% CLA exhibited similar fat loss (15-24%; P < or = 0.05) and liver enlargement (21-28%; P < or = 0.05), with no signs of steatosis. We also observed a dose-dependent increase in the transcription of genes involved in lipid breakdown and lipid harvesting from blood, and in genes related to the oxidative stress and inflammatory responses. These responsive genes varied in parallel with cell membrane lipids (R2 0.31-0.42) and to a lesser extent with liver enlargement (R2 0.22) (all P < 0.05). We conclude that in hamsters, liver enlargement induced by trans-10, cis-12-CLA is accompanied by an increased metabolic potential to process fatty acids from mobilised adipose stores. This elevated metabolic activity, comprised of anabolic pathways and their catabolic counterparts, can trigger inflammation and the oxidant stress defence pathways in a dose-dependent manner. These results provide novel insights into the mechanisms by which trans-10, cis-12-CLA affects pathways related to liver function.

Conjugated linoleic acid and atherosclerosis: studies in animal models

Conjugated linoleic acids (CLA) are isomeric forms of linoleic acid (LA) containing two conjugated sites of unsaturation. The most abundant dietary form of CLA is the cis-9,trans-11 (c-9,t-11) isomer that is found in the fatty tissues and milk of ruminant animals. CLA can also be acquired by ingestion of supplements, which are usually equimolar mixtures of the c-9,t-11 and t-10,c-12 CLA. For more than a decade, the potential for CLA to modify atherosclerosis in animal models has been examined. However, to date, the studies have failed to reach consensus on whether CLA can be effective in reducing the incidence or severity of atherosclerotic lesions, or whether or not plasma lipid and lipoprotein levels can be improved with CLA supplementation. This review will examine the evidence for and against a role for CLA in atherosclerosis, with a focus on the rabbit, the hamster, and the apoE-deficient mouse.

Conjugated linoleic acid modulation of risk factors associated with atherosclerosis

Conjugated linoleic acid (CLA) has been the subject of extensive investigation regarding its possible benefits on a variety of human diseases. In some animal studies, CLA has been shown to have a beneficial effect on sclerotic lesions associated with atherosclerosis, be a possible anti-carcinogen, increase feed efficiency, and act as a lean body mass supplement. However, the results have been inconsistent, and the effects of CLA on atherogenesis appear to be dose-, isomer-, tissue-, and species-specific. Similarly, CLA trials in humans have resulted in conflicting findings. Both the human and animal study results may be attributed to contrasting doses of CLA, isomers, the coexistence of other dietary fatty acids, length of study, and inter-and/or intra-species diversities. Recent research advances have suggested the importance of CLA isomers in modulating gene expression involved in oxidative damage, fatty acid metabolism, immune/inflammatory responses, and ultimately atherosclerosis. Although the possible mechanisms of action of CLA have been suggested, they have yet to be determined.

Effects of CLA at different dietary fat levels on the nutritional status of rats during protein repletion

OBJECTIVE

Protein depletion is associated with decreased body weight gain, low nitrogen balance, intrahepatic lipid accumulation, and hypoalbuminemia. Because conjugated linoleic acid (CLA) can increase lean body mass, enhance feed efficiency, and modulate lipid metabolism, this study investigated the effects of CLA at two levels of dietary fat on energy efficiency, nitrogen retention, and plasmatic and hepatic lipid levels in rats during dietary protein repletion.

METHODS

The animals were subjected to a moderate protein restriction for 14 d. After that, they were fed a protein repletion diet for 30 d, supplemented or not with CLA at recommended and high-fat levels. Energy efficiency, nitrogen balance, and nutritional parameters in serum and tissues were evaluated.

RESULTS

Protein repletion improved most of the nutritional parameters evaluated independently of CLA supplementation at both fat levels. At recommended fat levels, CLA did not have any effect. At high-fat levels, energy efficiency increased more than 20% by fat accumulation in carcasses and epididymal pads, serum cholesterol increased (two-fold), and liver triacylglycerol accumulation remained elevated. However, at high-fat levels, CLA prevented lipid accumulation in liver and adipose tissue.

CONCLUSION

Protein repletion improved the nutritional status of protein-restricted rats with minor effects of CLA at both dietary fat levels. However, when high-fat diets were given, CLA-enriched oil showed preventive effects on liver and adipose tissue lipid accumulation and no deleterious effects were observed. Because there are no studies dealing with CLA effects on protein repletion, this experimental model could improve nutritional interventions to overcome the protein-deficit stage.

Upregulation of tumor necrosis factor-alpha expression by trans10-cis12 conjugated linoleic acid enhances phagocytosis of RAW macrophages via a peroxisome proliferator-activated receptor gamma-dependent pathway

The aim of this study was to examine whether tumor necrosis factor (TNF)-alpha expression in the phagocytic activity of RAW macrophages by trans10-cis12 (10t-12c) conjugated linoleic acid (CLA) is associated with peroxisome proliferator-activated receptor gamma (PPARgamma) activation. 10t-12c CLA induced the TNF-alpha expression in RAW macrophages. Phagocytic activity of naive RAW macrophages was increased either by recombinant mouse (rm) TNF-alpha or by culture supernatant from 10t-12c CLA-treated RAW macrophages. This phagocytic activity was inhibited by addition of anti-rmTNF-alpha polyclonal antibody (pAb). 10t-12c CLA also increased the level of PPARgamma protein and mRNA in RAW macrophages. When naive RAW macrophages were incubated with the culture supernatant from RAW macrophages treated with 10t-12c CLA plus GW 9662, a PPARgamma antagonist, their phagocytic activity was significantly inhibited. In addition, GW 9662 antagonized the effect of 10t-12c CLA in stimulating TNF-alpha expression. These results suggest that 10t-12c CLA modulates the phagocytic activity of RAW macrophages by upregulating TNF-alpha expression via a PPARgamma-dependent pathway.

Effects of trans-10,cis-12 conjugated linoleic acid on cholesterol metabolism in hypercholesterolaemic hamsters

BACKGROUND

Conjugated linoleic acid (CLA) has received great attention in recent years because of its pleiotropic biological activities, but considerably fewer studies have been published addressing its role in serum lipids and atherosclerosis compared to other topics covered.

AIMS OF THE STUDY

The aim of the present study was to assess the effects of the trans-10,cis-12 isomer of CLA on cholesterolaemia and on several metabolic pathways involved in cholesterol metabolism in hamsters.

METHODS

Animals were fed atherogenic diets supplemented with 0.5% linoleic acid, 0.5% trans-10,cis-12 CLA or 1.0% trans-10,cis-12 CLA, for 6 weeks. Serum lipoproteins were separated by FPLC. Cholesterol in serum and liver, as well as triacylglycerols and phospholipids in liver were assessed by spectrophotometry. 3-Hydroxy-3-methylglutaryl coenzyme A reductase (HMGCoAR), acyl-coenzyme A:cholesterol acyltransferase (ACAT) and cholesteryl ester hydrolase (CEH) activities were measured by radiometry, and LDL receptors were determined by Western blot.

RESULTS

trans-10,cis-12 CLA feeding did not modify food intake nor final body weight. Although serum total cholesterol remained unchanged, when cholesterol fractions were analyzed a significant decrease in VLDL-cholesterol was observed in CLA-fed animals, without changes in HDL-cholesterol or LDL-cholesterol. trans-10,cis-12 CLA decreased cholesterol ester content and increased free cholesterol in liver. The activity of HMGCoAR was not modified. In contrast, ACAT activity was reduced by both CLA doses and CEH was increased by the high CLA dose. LDL receptors were significantly reduced by trans-10,cis-12 feeding when expressed as arbitrary units per mg of protein, however, the total receptor mass remained unchanged.

CONCLUSIONS

These results suggest that, under the present experimental conditions, trans-10,cis-12 CLA feeding reduces cholesterol esterification in liver and decreases the minority serum VLDL-cholesterol fraction, but it does not show a hypocholesterolaemic effect. A dose-response effect was not observed.

Lipid atherogenic risk markers can be more favourably influenced by thecis-9,trans-11-octadecadienoate isomer than a conjugated linoleic acid mixture or fish oil in hamsters

The aim of our present study was to compare the efficiency of conjugated linoleic acids (CLA) and fish oil in modulating atherogenic risk markers. Adult male hamsters were given a cholesterol-rich diet (0·6 g/kg) for 8 weeks; the diet was supplemented with 5 gcis-9,trans-11-CLA isomer/kg, 12 g CLA mixture (CLA-mix)/kg, 12 g fish oil/kg or 12 g fish oil + 12 g CLA-mix/kg. The plasma cholesterol status was improved only with thecis-9,trans-11-CLA (HDL-cholesterol and HDL-cholesterol:LDL-cholesterol ratio,P<0·05), but was of borderline significance for CLA-mix (HDL-cholesterol:LDL-cholesterol ratio,P=0·06), with an increase (33–40 %) in the liver lipoprotein receptors (scavenger receptor-type I and LDL ApoB/E receptor) and HDL-binding protein 2 (P<0·05). A 100 % pigment gallstones incidence and a slight insulin resistance (homeostatic model assessment index) were observed in the CLA-mix-fed hamsters (P=−0·031). In comparison, fish-oil feeding alone improved merely the scavenger receptor-type I and HDL-binding protein 2 liver status and faeces sterol output. For most of our present observations, the concomitant intake of fish oil and CLA-mix gave dominant effects that were exclusive and specific to one or the other oil. In conclusion, part of the beneficial effects of CLA in the present study can be ascribed to thecis-9,trans-11-isomer, and these did not generally overlap with those of fish oil. In addition, the CLA-mix effects are clearly affected by the marine (n-3) fatty acids.

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.

Selective effect of conjugated linoleic acid isomers on atherosclerotic lesion development in apolipoprotein E knockout mice

Research suggests that conjugated linoleic acid (CLA) may inhibit atherosclerosis, but there are contradictory results in different animal models fed heterogeneous mixtures of CLA isomers. This study addressed the hypothesis that the individual CLA isomers may exert different atherogenic properties. ApoE(-/-) mice were fed isocaloric, isonitrogenous westernized diets containing 0.15% cholesterol and enriched with 1% (w/w) cis-9,trans-11-CLA (c9,t11-CLA), trans-10,cis-12-CLA (t10,c12-CLA) or linoleic acid (control diet) for 12 weeks. At the end of the dietary intervention, the effects of CLA isomers on the development of atherosclerotic vascular lesions, lipid metabolism, inflammation and oxidative stress were assessed. The t10,c12-CLA diet had a profound pro-atherogenic effect, whereas c9,t11-CLA impeded the development of atherosclerosis. En face aortic lesion assessment showed more dorsal and lumbar extensions presenting atherosclerotic foci after the t10,c12-CLA diet. Furthermore, animals fed t10,c12-CLA had pronounced hyperlipidemia, higher 8-iso-prostaglandin F(2alpha) levels, higher vulnerable atherosclerotic plaque with a lower smooth muscle and fibre contents and higher macrophage content and activation, assayed as plasma chitotriosidase compared to the control or c9,t11-CLA dietary groups. Plasma chitotriosidase activity was more closely associated with the extent of the plaque than with MOMA staining or than monocyte chemoattractant protein-1 levels. Our results demonstrate that CLA isomers differentially modulate the development of atherosclerosis, c9,t11-CLA impedes, whereas t10,c12-CLA promotes atherosclerosis. These opposing effects may be ascribed to divergent effects on lipid, oxidative, inflammatory and fibro muscular components of this pathology. Plasma chitotriosidase is a better indicator of dietary fat interventions that alter plaque monocyte activity in this murine model.

Cis-9, trans- 11 and trans-10, cis-12 conjugated linoleic acid (CLA) do not affect the plasma lipoprotein profile in moderately overweight subjects with LDL phenotype B

BACKGROUND

Results of a pilot study suggested that cis-9, trans-11 conjugated linoleic acid (CLA) improved LDL phenotype in moderately overweight subjects with LDL phenotype B.

OBJECTIVE

Initiated by the results of this pilot study, we have specifically designed a study to test the hypothesis that cis-9, trans-11 conjugated linoleic acid improves LDL phenotype in moderately overweight subjects with LDL phenotype B. Effects on the serum lipid profile, on plasma glucose and insulin concentrations, and on clinical parameters were also examined.

DESIGN

Volunteers with LDL phenotype B were divided into three groups consuming daily a drinkable dairy product not enriched with CLA (placebo, n = 34), the same dairy product enriched with 3g c9, t11 CLA (n = 34), or the dairy product enriched with 3g t10, c12 CLA (n = 19) for 13 weeks.

RESULTS

Median changes in the proportions of plasma small dense LDL were -2.0% in the control group and -0.1% in the c9, t11 CLA and t10, c12 CLA groups (p = 0.981 for the differences between the groups). c9, t11 CLA or t10, c12 CLA did also not affect serum concentrations of LDL and HDL cholesterol, and of triacylglycerol, and plasma concentrations of glucose and insulin.

CONCLUSIONS

In humans with LDL phenotype B, c9, t11 CLA and t10, c12 CLA do not beneficially change risk factors for cardiovascular disease or diabetes.

The form of dietary conjugated linoleic acid does not influence plasma and liver triacylglycerol concentrations in Syrian golden hamsters

Several studies have shown that conjugated linoleic acid (CLA) supplementation can improve the plasma lipid profile and thereby probably decrease the risk for development of atherosclerosis. The aim of the present study was to compare the effects on plasma and organ lipids of different dietary forms of CLA: triacylglycerol (TAG), diacylglycerol (DAG), monoacylglycerol (MAG), and fatty acid ethyl esters (FAEEs). DAG-, MAG-, and FAEE-CLA were produced by enzymatic interesterifications and all supplements were composed of a 1:1 mixture of the 2 major CLA isomers: cis-9, trans-11 and trans-10, cis-12. Male Syrian Golden hamsters were fed mildly atherogenic diets (10 g butter/100 g, 0.1 g cholesterol/100 g) supplemented with 0.5 g CLA/100 g or without CLA (control) for 8 wk. Liver weights were greater in the TAG- and FAEE-CLA groups than in the control group. In general, the form of CLA did not differentially affect plasma or liver cholesterol or plasma lipoprotein cholesterol concentrations, but only the TAG-CLA group had a higher final plasma TAG concentration than the control group. Both CLA isomers were incorporated into plasma, livers, and spleens. The results of the present study suggest that the form in which CLA is supplemented in the diet does not affect hamster plasma and liver TAG concentrations. The TAG-CLA form, a frequently used form of supplemental CLA, increases plasma TAG concentrations. If similar effects occur in humans, supplemental TAG-CLA cannot be considered to be beneficial given the relation between plasma TAG and the development of atherosclerosis.

Conjugated linoleic acid isomers reduce blood cholesterol levels but not aortic cholesterol accumulation in hypercholesterolemic hamsters

The aim of the present study was to characterize plasma lipids and lipoprotein cholesterol and glucose concentrations in hamsters fed either cis-9,trans-11 CLA (9c,11 tCLA); trans-10,cis-12 CLA (10t,12c CLA); or linoleic acid (LA) on the accumulation of aortic cholesterol in hypercholesterolemic hamsters. One hundred male F1B strain Syrian Golden Hamsters (Mesocricetus auratus) (BioBreeders Inc., Watertown, MA) approximately 9 wk of age were housed in individual stainless steel hanging cages at room temperature with a 12-h light/dark cycle. Hamsters were given food and water ad libitum. Following a 1-wk period of acclimation, the hamsters were fed a chow-based (nonpurified) hypercholesterolemic diet (HCD) containing 10% coconut oil (92% saturated fat) and 0.1% cholesterol for 2 wk. After an overnight fast, the hamsters were bled and plasma cholesterol concentrations were measured. The hamsters were then divided into 4 groups of 25 based on similar mean plasma VLDL and LDL cholesterol (nonHDL-C) concentrations. Group 1 remained on the HCD (control). Group 2 was fed the HCD plus 0.5% 9c,11t CLA isomer. Group 3 was fed the HCD plus 0.5% 10t,12c CLA isomer. Group 4 was fed the HCD plus 0.5% LA. Compared with the control, both CLA isomers and LA had significantly lower plasma total cholesterol and HDL cholesterol concentrations (P < 0.001) after 12 but not 8 wk of treatment and were not significantly different from each other. Also, both CLA isomers had significantly lower plasma nonHDL-C concentrations (P < 0.01) compared with the control after 12 but not 8 wk of treatment and were not significantly different from each other or the LA-fed hamsters. Plasma TG concentrations were significantly higher (P < 0.004) with the 10t, 12c CLA isomer compared with the other treatments at 8 but not at 12 wk of treatment. Plasma TG concentrations were also significantly lower (P < 0.03) with the 9c,11t CLA isomer compared with the control at 12 wk of treatment. Also, the 10t,12c CLA isomer and LA had significantly higher plasma glucose concentrations compared with the control and 9c,11t CLA isomer (P < 0.008) at 12 wk of treatment, whereas at 8 wk, only the LA treatment had significantly higher plasma glucose concentrations (P < 0.001) compared with the 9c,11t CLA isomer. Although liver weights were significantly higher in 10t,12c CLA isomer-fed hamsters, liver total cholesterol, free cholesterol, cholesterol ester, and TG concentrations were significantly lower in these hamsters compared with hamsters fed the control, 9c,11t CLA isomer, and LA diets (P< 0.05). The 9c,11t CLA isomer and LA diets tended to reduce cholesterol accumulation in the aortic arch, whereas the 10t,12c CLA isomer diet tended to raise cholesterol accumulation compared with the control diet; however, neither was significant. In summary, no differences were observed between the CLA isomers for changes in plasma lipids or lipoprotein cholesterol concentrations. However, the 9c,11t CLA isomer did appear to lower plasma TG and glucose concentrations compared with the 10t,12c CLA isomer. Such differences may increase the risk of insulin resistance and type 2 diabetes in humans when the 10t,12c CLA isomer is fed separately.

Selective conjugated fatty acids inhibit guinea pig platelet aggregation

Conjugated linoleic acids have been shown to reduce eicosanoid release from select tissues and/or cells. To elucidate effects of conjugated linoleic acid isomers on cyclooxygenase-1 (COX-1) activity and their application as platelet aggregation inhibitors, conjugated linoleic acid isomers and conjugated nonadecadienoic acid were incubated with ovine COX-1 and Raw264.7 macrophage to examine their effects on COX-1 activity. The effects were further examined in collagen and ADP-induced guinea pig whole blood platelet aggregation. Fatty acids tested were shown to inhibit COX-1 enzymatic activity. However, only 10t, 12c-conjugated linoleic acid, 9t, 11t-conjugated linoleic acid and conjugated nonadecadienoic acid inhibited collagen and ADP-induced platelet aggregation with IC(50) 125.9 microM (74.2 microM to 213.4 microM, 95% confidence interval), 99.3 microM (52.8 microM to 187.2 microM, 95% confidence interval) and 124.3 microM (85.1 microM to 181.5 microM, 95% confidence interval) respectively in collagen-induced aggregation. TxB(2) release was also appreciably inhibited by 10t, 12c-conjugated linoleic acid, 9t, 11t-conjugated linoleic acid and conjugated nonadecadienoic acid. Based on these data, we conclude 10t, 12c-conjugated linoleic acid, 9t, 11t-conjugated linoleic acid and conjugated nonadecadienoic acid are platelet aggregation inhibitors while 9c, 11t-conjugated linoleic acid is a moderate inhibitor and linoleic acid, and 9c, 11c-conjugated linoleic acid have no effect on whole blood platelet aggregation.

Biological effects of conjugated linoleic acids in health and disease

Conjugated linoleic acid (CLA) is a mixture of positional and geometric isomers of octadecadienoic acid [linoleic acid (LA), 18:2n-6] commonly found in beef, lamb and dairy products. The most abundant isomer of CLA in nature is the cis-9, trans-11 (c9t11) isomer. Commercially available CLA is usually a 1:1 mixture of c9t11 and trans-10, cis-12 (t10c12) isomers with other isomers as minor components. Conjugated LA isomer mixture and c9t11 and t10c12 isomers alone have been attributed to provide several health benefits that are largely based on animal and in vitro studies. Conjugated LA has been attributed many beneficial effects in prevention of atherosclerosis, different types of cancer, hypertension and also known to improve immune function. More recent literature with availability of purified c9t11 and t10c12 isomers suggests that t10c12 is the sole isomer involved in antiadipogenic role of CLA. Other studies in animals and cell lines suggest that the two isomers may act similarly or antagonistically to alter cellular function and metabolism, and may also act through different signaling pathways. The effect of CLA and individual isomers shows considerable variation between different strains (BALB/C mice vs. C57BL/6 mice) and species (e.g., rats vs. mice). The dramatic effects seen in animal studies have not been reflected in some clinical studies. This review comprehensively discusses the recent studies on the effects of CLA and individual isomers on body composition, cardiovascular disease, bone health, insulin resistance, mediators of inflammatory response and different types of cancer, obtained from both in vitro and animal studies. This review also discusses the latest available information from clinical studies in these areas of research.

Characterization and regulation of the bovine stearoyl-CoA desaturase gene promoter

The bovine stearoyl-CoA desaturase (Scd) gene plays an important role in the bovine mammary gland where substrates such as stearic and vaccenic acids are converted to oleic acid and conjugated linoleic acid (CLA), respectively. Up to 90% of the CLA in bovine milk is formed due to the action of this enzyme in the mammary gland. The areas of the bovine promoter of importance in regulating this key enzyme were examined and an area of 36bp in length was identified as having a critical role in transcriptional activation and is designated the Scd transcriptional enhancer element (STE). Electrophoretic mobility shift assay detected three binding complexes on this area in Mac-T cell nuclear extracts. Treatment of cells with CLA caused a significant reduction in transcriptional activity, with this effect being mediated through the STE region. The bovine Scd gene promoter was up-regulated by insulin and down-regulated by oleic acid.

Acis-9,trans-11-conjugated linoleic acid-rich oil reduces the outcome of atherogenic process in hyperlipidemic hamster

Conjugated linoleic acid (CLA) mixtures demonstrated antiatherogenic properties in several animal models, including hamsters, but the mechanism of action of the main food-derived CLA isomer is unknown in this species. This study thus focused on cis-9, trans-11-CLA (rumenic acid), and its effect was compared with that of fish oil, which is known to influence several aspects of atherogenesis. Syrian hamsters were fed (for 12 wk) diets containing 20% (wt/wt) butter fat (B diet) or the same diet augmented with either 1% (wt/wt) of a cis-9, trans-11-CLA-rich oil (BR diet) or 1% (wt/wt) fish oil (BF diet). The BR diet induced the lowest aortic lipid deposition (from −30% to −45%) among the butter oil-fed hamsters. In this group, plasma also displayed a reduced non-HDL-to-HDL-cholesterol ratio (21% less than in the butter oil group) and inflammatory serum amyloid A levels (70–80%) and an improvement of anti-oxidized LDL paraoxonase activity (all P < 0.05). Compared with the B group, the beneficial effects of the BR diet could be further explained in part by preventing the high VCAM-1 expression rate, increasing (30%) ATP-binding cassette subfamily A1 expression in the aorta, and downregulating expression of inflammatory-related genes (TNF-α, IL-1β, and cyclooxygenase 2, 2- to 2.8-fold, P < 0.05). This effect was partly associated with an activation of peroxisome proliferator-activating receptor (PPAR)/liver X receptor (LXR)-α signaling cascade. Interestingly, activation of PPAR/LXR-α signaling was not observed in hamsters fed the BF diet, in which the early signs of atherogenesis were increased. In conclusion, this study demonstrated that milk fat-rich cis-9, trans-11-CLA reduces the atherogenic process in hyperlipidemic hamsters.

Butter naturally enriched in conjugated linoleic acid and vaccenic acid alters tissue fatty acids and improves the plasma lipoprotein profile in cholesterol-fed hamsters

Butter, which is naturally enriched in cis-9, trans-11 conjugated linoleic acid (rumenic acid; RA) and vaccenic acid (VA), has been shown to be an effective anticarcinogen in studies with animal models; however, there has been no examination of the effects of a naturally derived source of VA and RA on atherosclerosis-related biomarkers. The current study was designed to determine the effect of a diet containing VA/RA-enriched butter on plasma lipoproteins and tissue fatty acid profiles in cholesterol-fed hamsters. Male Golden Syrian hamsters were fed diets containing 0.2% cholesterol and 20% added fat as: 1) Control, 20% standard butter (CT); 2) 5% standard butter + 15% VA/RA-enriched butter (EB); 3) 15% standard butter + 5% partially-hydrogenated vegetable oil (VO). After 4 wk, plasma lipoproteins were isolated, cholesterol quantified, and tissue fatty acid profiles determined. Tissue concentrations of VA and RA were increased by consumption of the EB diet compared with both the CT and VO diets, whereas the VO diet increased their concentration compared with the CT diet only. Total and LDL cholesterol concentrations were significantly reduced in hamsters fed EB and VO compared with CT, whereas VLDL cholesterol concentrations were reduced in hamsters fed EB compared with those fed CT and VO. HDL cholesterol concentrations did not differ among treatments. The ratio of potentially atherogenic lipoproteins [VLDL + intermediate density lipoproteins (IDL) + LDL] to antiatherogenic HDL was significantly lower in hamsters fed VA/RA-enriched butter (0.60) than in those fed either control diet (1.70) or the diet containing partially hydrogenated vegetable oil (1.04). Thus, increasing the VA/RA concentration of butter results in a plasma lipoprotein cholesterol profile that is associated with a reduced risk of atherosclerosis.

Divergent mechanisms of cis 9, trans 11 ‐ and trans 10 , cis 12 ‐ conjugated linoleic acid affecting insulin resistance and inflammation in apolipoprotein E knockout mice: a proteomics approach

Conjugated linoleic acids (CLA) affect atherogenesis, but mechanisms are not well understood. We explored how two isomers of CLA, cis9, trans11-CLA and trans10, cis12-CLA, affected lipid and glucose metabolism, as well as hepatic protein expression, in apolipoprotein E knockout mice. After 12 wk of intervention, plasma triglyceride, NEFA, and glucose concentrations were significantly higher in the trans10, cis12-CLA group, whereas plasma triglyceride, NEFA, glucose, and insulin concentrations were significantly lower in the cis9, trans11-CLA group, compared with control mice consuming linoleic acid. Proteomics identified significant up- or down-regulation of 113 liver cytosolic proteins by either CLA isomer. Principal component analysis revealed that the treatment effect of cis9, trans11-CLA was mainly explained by the up-regulation of different posttranslational forms of heat shock protein 70 kD. In contrast, the treatment effect of trans10, cis12-CLA was mainly explained by up-regulation of key enzymes in the gluconeogenic, beta-oxidation, and ketogenesic pathways. Correlation analysis again emphasized the divergent effects of both CLA isomers on different pathways, but also revealed a linkage between insulin resistance and increased levels of hepatic serotransferrin. Thus, our systems biology approach provided novel insights into the mechanisms by which individual CLA isomers differentially affect pathways related to atherogenesis, such as insulin resistance and inflammation.

Effect of conjugated linoleic acid isomers on lipoproteins and atherosclerosis in the Syrian Golden hamster

Conjugated linoleic acid (CLA) is a group of positional and geometric isomers of linoleic acid (LA, C18:2 cis-9, cis-12) that are reported to have important biological activities, including protection against atherosclerosis. In this study, the potential role of the individual cis-9, trans-11 and trans-10, cis-12 isomers of CLA in atherogenesis were compared with LA in the Syrian Golden hamster. Supplementation of a high-fat, high-cholesterol diet (HFHC) with 1% (w/w) cis-9, trans-11 CLA or trans-10, cis-12 CLA did not significantly affect plasma cholesterol levels compared to supplementation with 1% (w/w) LA. Very low density lipoprotein cholesterol (VLDL-C) was lower and plasma triglycerides (TG) were higher in diets where C18:2 fatty acid was added to the HFHC diet, but neither the cis-9, trans-11 CLA group nor trans-10, cis-12 CLA group was significantly different from the LA control group. CLA supplementation did not significantly affect low density lipoprotein cholesterol (LDL-C). Trans-10, cis-12 CLA increased high density lipoprotein cholesterol (HDL-C) levels compared to LA or cis-9, trans-11 CLA (P<0.02), and although the ratio of non-HDL-C:HDL-C in the cis-9, trans-11 CLA group (1.11+/-0.54) and the trans-10, cis-12 CLA group (1.11+/-0.21) was lower than the LA group (1.29+/-0.45), the reduction did not reach statistical significance. Atherosclerosis was assessed in the ascending aorta by measuring the number of aortic cross-sections containing Oil Red O-stained intimal lesions. Compared to the LA group (60+/-11%), both the cis-9, trans-11 CLA group (38+/-8%) and the trans-10, cis-12 CLA group (28+/-7%) had fewer sections displaying a fatty streak lesion, although the differences did not reach statistical significance. These results suggest that individual CLA isomers may reduce atherosclerotic lesion development in the hamster, but when compared to LA, the apparent atheroprotective effects do not correlate with beneficial changes in lipoprotein profile.

The Combination of Dietary Conjugated Linoleic Acid and Treadmill Exercise Lowers Gain in Body Fat Mass and Enhances Lean Body Mass in High Fat–Fed Male Balb/C Mice

Nearly half of the U.S. adult population is overweight or obese, which may be related to increased energy intake combined with lack of physical activity. Obesity increases the risk of several chronic diseases including diabetes, coronary heart disease, hypertension, and stroke. Conjugated linoleic acids (CLA) were shown to decrease fat and increase lean mass in several animal studies. However, the effects of CLA in combination with exercise (Ex) on body composition have not been studied in an animal model. We examined the effect of a low concentration of either safflower oil as control (0.5%) or mixed isomers of CLA (0.4%) along with treadmill exercise on body composition in male Balb/C mice fed a high-fat diet (20% corn oil) in a 2 x 2 factorial design. CLA consumption lowered change in fat mass (P < 0.001) confirming the results of other studies, and change in fat mass decreased further (P < 0.001) with CLA and exercise. Change in lean mass did not increase with exercise alone; it increased, although not significantly, with CLA alone and increased significantly (P < 0.05) due to the combination of CLA and exercise. This effect was accompanied by decreased serum leptin levels and lower leptin mRNA expression in peritoneal fat (P < 0.001). Serum insulin, glucose, tumor necrosis factor (TNF)-alpha, and interleukin-6 were lower in CLA-fed mice than in controls (P < 0.05), whereas serum TNF-alpha was increased by exercise (P < 0.05). Exercise increased oxygen consumption and energy expenditure when measured under resting conditions (P < 0.05). In summary, the combination of dietary CLA and exercise decreased fat mass and increased lean mass in mice fed a high-fat diet, and these effects may be related in part to decreased serum leptin and exercise-induced increases in oxygen consumption and energy expenditure.

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.

Conjugated linoleic acid supplementation, insulin sensitivity, and lipoprotein metabolism in patients with type 2 diabetes mellitus

BACKGROUND

Some animal studies have suggested that conjugated linoleic acid (CLA) supplementation may have therapeutic potential with respect to insulin sensitivity and lipid metabolism, which are important cardiovascular disease (CVD) risk factors associated with type 2 diabetes mellitus.

OBJECTIVE

We investigated the effect of CLA supplementation on markers of glucose and insulin metabolism, lipoprotein metabolism, and inflammatory markers of CVD in subjects with type 2 diabetes.

DESIGN

The study was a randomized, double-blind, placebo-controlled trial. Thirty-two subjects with stable, diet-controlled type 2 diabetes received CLA (3.0 g/d; 50:50 blend of cis-9,trans-11 CLA and trans-10,cis-12 CLA) or control for 8 wk. A 3-h 75-g oral-glucose-tolerance test was performed, and fasting plasma lipid concentrations and inflammatory markers were measured before and after the intervention.

RESULTS

CLA supplementation significantly increased fasting glucose concentrations (6.3%; P < 0.05) and reduced insulin sensitivity as measured by homeostasis model assessment, oral glucose insulin sensitivity, and the insulin sensitivity index (composite) (P = 0.05). Total HDL-cholesterol concentrations increased by 8% (P < 0.05), which was due to a significant increase in HDL(2)-cholesterol concentrations (P < 0.05). The ratio of LDL to HDL cholesterol was significantly reduced (P < 0.01). CLA supplementation reduced fibrinogen concentrations (P < 0.01) but had no effect on the inflammatory markers of CVD (C-reactive protein and interleukin 6).

CONCLUSIONS

CLA supplementation had an adverse effect on insulin and glucose metabolism. Whereas CLA had positive effects on HDL metabolism and fibrinogen, a therapeutic nutrient should not be associated with potentially adverse effects on other clinical markers of type 2 diabetes.

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.