Modulation of body fat and serum leptin levels by dietary conjugated linoleic acid in Sprague-Dawley rats fed various fat-level diets

OBJECTIVES: In this study, we examined the effect of dietary conjugated linoleic acid (CLA) on body fat levels in Sprague-Dawley rats. METHODS: Rats were fed AIN-93G type diets containing 4%, 7%, and 10% fats with or without 1.5% CLA. RESULTS: Three weeks after the onset of the experimental period, the weights of perirenal white adipose tissue were lower in CLA-fed rats. The weights of epididymal white adipose tissue also were lower in CLA-fed rats than in control rats, but this effect disappeared with increased dietary fat level. Serum leptin levels tended to be lower in the CLA group, especially the low-fat diet group, than in the control group. There were significant positive correlations between serum leptin level and weights of perirenal and epididymal white adipose tissues in control groups, but these correlations were weaker in the CLA groups. Serum tumor necrosis factor-alpha levels also tended to be lower in CLA-fed rats, and this tendency was most remarkable in the rats fed 7% fat diets. CONCLUSION: In conclusion, dietary CLA, especially the low-fat diet, reduced body fat without hepatic injury to Sprague-Dawley rats.     

Metabolic effects of dietary conjugated linoleic acid (CLA) isomers in rats

To know the effect of individual conjugated linoleic acid (CLA) isomers on lipid metabolism, male rats were fed diets containing either linoleic acid (LA, a control fatty acid), CLA containing mainly 9c,11t-isomer, 10t,12c-isomer (at the 0.8% level) or an equivalent mixture of these isomers (at the 0.4% level) for 26 days. Although there were no differences in food intake and body weight gain among the groups, the food efficiency was low in rats fed the CLA containing 10t,12c-isomer in comparison with those fed 9c,11t-CLA. The weight of white (epididymal and perirenal) adipose tissues decreased in all CLA groups, while that of brown adipose tissue increased in rats fed 10t,12c-CLA, the difference between 9c,11t- and 10t,12c-isomers being significant. The concentration of serum total cholesterol, triacylglycerol and phospholipid tended to be lower in rats fed CLA preparations containing 10t,12c-CLA, while there was a trend toward an increasing concentration of serum HDL-cholesterol in all CLA groups. The rate of fatty acid β-oxidation in the liver peroxisomes was slightly higher in rats fed CLA than in those fed LA, and the activity of mitchondrial carnitine parmitoyltranceferase (CPT) in the CLA-mix group significantly increased compared to the LA group. The effect of CLA on the concentration of spleen and serum IgE, IgG and IgA level was variable. No CLA effect was observed on the concentration of serum leptin and TNF-. Thus, individual isomers of CLA may have different effects on some metabolic parameters in rats. The results also suggested a probable interaction of different isomers on lipid metabolism.     

共轭亚油酸对肥胖大鼠PPARγ基因表达及血清瘦素水平的影响

目的　研究不同剂量共轭亚油酸 (CLA)对饮食诱导肥胖大鼠PPARγ基因、瘦素、血糖、血脂的影响。方法　选用雄性Wistar大鼠 ,随机分为对照组、高脂组、高脂 +CLA组 (每 10 0g饲料含CLA分别为 0 75g、1 5 0g、3 0 0g) ,于第 12周末处死动物 ,计算脂 体比 ,测定大鼠血糖、血脂及瘦素水平 ,并应用RT PCR的方法检测大鼠白色脂肪组织过氧化物酶体增殖物激活受体γ(PPARγ)的表达水平。结果　CLA可降低肥胖大鼠血糖、甘油三酯 (TG)、总胆固醇 (TC)及瘦素水平 ,增加脂肪组织PPARγmRNA的表达水平。结论　CLA可降低肥胖大鼠血糖、血脂 ,并可通过激活PPARγ下调瘦素水平 ,有改善肥胖大鼠的瘦素抵抗作用。     

Dietary supplementation with conjugated linoleic acid plus n-3 polyunsaturated fatty acid increases food intake and brown adipose tissue in rats

The effect of supplementation with 1% conjugated linoleic acid and 1% n-3 long chain polyunsaturated fatty acids (CLA/n-3) was assessed in rats. Food intake increased with no difference in body weights. White adipose tissue weights were reduced whereas brown adipose tissue and uncoupling protein-1 expression were increased. Plasma adiponectin, triglyceride and cholesterol levels were reduced while leptin, ghrelin and liver weight and lipid content were unchanged. Hypothalamic gene expression measurements revealed increased expression of orexigenic and decreased expression of anorexigenic signals. Thus, CLA/n-3 increases food intake without affecting body weight potentially through increasing BAT size and up-regulating UCP-1 in rats.     

Combined effects of dietary conjugated linoleic acid and sesamin triacylglycerol and ketone body production in rat liver

The effects of a combination of dietary conjugated linoleic acid (CLA) supplemented with sesamin on hepatic ketogenesis and triacylglycerol secretion were compared using the livers of rats fed diets containing 1% CLA or linoleic acid (LA) in combination with 0.2% sesamin for 14 d, respectively. The feeding of CLA, as compared to LA, caused a significant reduction in the weight of perirenal adipose tissue but not that of epididymal adipose tissue, and affected neither growth parameters nor hepatic lipid concentration. Hepatic production of ketone bodies was consistently higher in rats fed CLA than in those fed LA, while triacylglycerol secretion was reversed. No significant difference was noted in the hepatic secretion of cholesterol among the groups. Although there was no effect of the dietary combination of CLA with sesamin on adipose tissue weight, hepatic lipid parameters and ketone body production were observed: i.e., triacylglycerol secretion tended to be reduced. These results suggest that the dietary combination of CLA with sesamin may be an effective approach for lowering serum triacylglycerol levels. The decreased hepatic secretion of triacylglycerol is, in part, due to enhanced fatty acid oxidation in the liver.     

Functional lipids and the prevention of the metabolic syndrome

The metabolic syndrome is increasingly prevalent in worldwide. The quality and quantity of dietary lipids could be important modulators associated with the cardiovascular morbidity and mortality. At present, functional lipids such as conjugated linoleic acid (CLA) and phospholipids have attracted considerable attention because of their beneficial biological effects in attenuating metabolic syndrome. Supplementation of CLA reduces abdominal white adipose tissues, serum triacylglycerol (TAG) level, and liver TAG level in obese Otsuka Long-Evans Tokushima Fatty OLETF rats. These effects were attributed to enhanced fatty acid beta-oxidation and suppressed fatty acid synthesis in the liver. In addition, CLA enhanced energy expenditure in these rats. Anti-hypertensive properties of CLA have also been demonstrated. In obese/diabetic OLETF and Zucker rats, feeding of CLA prevented the development of obesity-induced hypertension. This was associated with an altered production of physiologically active adipocytokines, such as adiponectin, leptin and angiotensinogen. In addition, CLA could alleviate the development of insulin resistance and fatty liver. Dietary phospholipids have physiological functions that are different to dietary TAG. We recently reported that phosphatidylcholine (PC) alleviated orotic acid-induced fatty-liver through the suppression of hepatic lipogenesis in rats, and omega 3-PC from salmon roe prevented the development of obesity-related diseases through the suppression of lipogenic gene expressions and the enhancement of lypolytic gene expressions in the liver of obese rats. However, reports which studying the nutritional functions of minor phospholipids, such as phosphatidylinositol (PI), are scarce. Our study indicated that dietary PI lowered lipids in the plasma and liver by suppressing hepatic TAG synthesis.     

共轭亚油酸对胰岛素抵抗大鼠ap2基因表达的影响

目的通过研究共轭亚油酸(CLA)对饮食诱导胰岛素抵抗大鼠脂肪酸连接蛋白(ap2)基因表达的影响,探讨CLA抗糖尿病作用的机制。方法选用雄性Wistar大鼠,随机分为对照组、高脂组、高脂+CLA组(每100g饲料含CLA分别为0·75g、1·50g、3·00g),每组动物10只,观察CLA对胰岛素抵抗大鼠胰岛素、血糖水平的影响,并应用RT-PCR的方法检测ap2、过氧化物酶体增殖物活性受体γ(PPARγ)的表达水平。结果高脂组大鼠血清游离脂肪酸(FFA)、胰岛素和糖血水平显著高于基础组,CLA可降低胰岛素抵抗大鼠血清FFA、血糖、胰岛素水平,并可增加其脂肪组织ap2、PPARγmRNA的表达水平。结论CLA可通过激活PPARγ上调脂肪酸连接蛋白基因的表达,改善肥胖大鼠的胰岛素抵抗。     

Dietary conjugated linoleic acid mixture affects the activity of intestinal acyl coenzyme A: cholesterol acyltransferase in hamsters

The present study was designed to study the mechanisms by which dietary conjugated linoleic acids (CLA) decrease serum cholesterol. Hamsters were fed a semi-synthetic diet containing 1 g cholesterol/kg diet with or without supplementation with 20 g linoleic acid (LA) and 20 g CLA/kg diet. After 8 weeks, serum fasting total cholesterol (TC) and triacylglycerol (TG) were significantly lower in the LA-supplemented and CLA-supplemented groups compared with those of the control (CTL) hamsters. In contrast to LA, CLA significantly lowered hepatic cholesterol but it increased the level of adipose tissue cholesterol, suggesting that the hypocholesterolaemic mechanism of CLA is different from that of LA. CLA decreased the activity of intestinal acyl CoA:cholesterol acyltransferase (ACAT) whereas LA had no effect on this enzyme. Consequently, CLA supplementation increased the faecal excretion of total neutral sterols, but it had no or little effect on the faecal acidic sterols. If the ACAT is associated with cholesterol absorption, the part of mechanisms by which CLA decreases serum cholesterol may involve down-regulation of intestinal ACAT activity.     

Dietary effect of pomegranate seed oil rich in 9cis, 11trans, 13cis conjugated linolenic acid on lipid metabolism in obese,hyperlipidemic OLETF Rats

Conjugated fatty acid, the general term of positional and geometric isomers of polyunsaturated fatty acids with conjugated double bonds, has attracted considerable attention because of its potentially beneficial biological effects. In the present study, dietary effect of pomegranate seed oil rich in punicic acid (9 cis, 11 trans, 13 cis -conjugated linolenic acid; 9c, 11t, 13c-CLNA) on lipid metabolism was investigated in obese, hyperlipidemic Otsuka Long-Evans Tokushima Fatty (OLETF) rats. After 2 weeks feeding period, OLETF rats revealed obesity and hyperlipidemia compared with their progenitor LETO rats. Feeding of the diet supplemented with 9% safflower oil and 1% pomegranate seed oil (9c, 11t, 13c-CLNA diet) did not affect abdominal white adipose tissue weights and serum lipid levels compared with the diet supplemented with 10% safflower oil (control diet) in OLETF rats. However, the accumulated hepatic triacylglycerol was markedly decreased by 9c, 11t, 13c-CLNA diet in OLETF rats. Activities of hepatic enzymes related to fatty acid synthesis and fatty acid β-oxidation were not altered by 9c, 11t, 13c-CLNA diet. Levels of monounsaturated fatty acid (MUFA), major storage form of fatty acid, in serum triacylglycerol were markedly higher in obese, hyperlipidemic OLETF rats than in lean LETO rats. In addition, 9c, 11t, 13c-CLNA diet significantly decreased MUFA levels in OLETF rats. This is the first study showing that 9c, 11t, 13c-CLNA suppresses delta-9 desaturation in vivo, and we suggest that the alleviation of hepatic triacylglycerol accumulation by 9c, 11t, 13c-CLNA diet was, at least in part, attributable to the suppression of delta-9 desaturation in OLETF rats.     

Dietary conjugated linoleic acid differentially alters fatty acid composition and increases conjugated linoleic acid content in porcine adipose tissue

Conjugated linoleic acids (CLA) have been shown to decrease body fat content in pigs. It is possible that feeding pigs diets rich in CLA may increase carcass lipid CLA to levels that could provide health benefits when included as a part of a healthy diet. Therefore, the aim of the present study was to determine whether dietary CLA supplementation has any effect on the fatty acid composition of subcutaneous and intramuscular adipose tissue in pigs. Thirty-five female cross bred (Large White x Landrace) pigs (initial weight 57.2 kg and initial P2 back fat 11.5 mm) were used in the present study. Pigs were housed individually and randomly allocated to one of six dietary treatments (0.00, 1.25, 2.50, 5.00, 7.50 and 10.00 g CLA55 (55 g CLA isomers/100 g total fatty acids; Natural Lipids Ltd, Hovdebygda, Norway)/kg) and fed their respective diets for 8 weeks. Twelve CLA isomers in the diet and in pig tissue lipids were separated by Ag+-HPLC. CLA was incorporated at fivefold higher levels in subcutaneous fat as compared with intramuscular fat and in a dose-dependant manner. Overall, the transfer efficiency of CLA was maximized at 5.00 g CLA55/kg. However, there was clear selectivity in the uptake or incorporation of cis,trans-9,11 isomer over the trans,cis-10,12 isomer. In general, CLA supplementation produced significant changes in skeletal muscle and adipose tissue fatty acid composition, indicating that dietary CLA had a potent affect on lipid transport and metabolism in vivo. Significant increases in myristic, palmitic and palmitoleic acids and a reduction in arachidonic acid were observed, suggesting an alteration in activity of delta5-, delta6- and delta9-desaturases in pig adipose tissue. In conclusion, feeding pigs diets supplemented with CLA increases carcass lipid CLA, but also results in changes in the fatty acid profile in pig fat that could potentially outweigh the benefits of CLA.     

共轭亚油酸对饮食诱导肥胖大鼠脂代谢及相关基因表达的影响

目的:通过研究共轭亚油酸(CLA)对饮食诱导肥胖大鼠脂肪酸转移蛋白、酰基CoA合成酶基因表达的影响,探讨CLA抗糖尿病机制。方法:选雄性Wistar大鼠,随机分为对照组、高脂组、高脂+CLA组(每100g饲料含CLA分别为0.75、1.50、3.00g),每组动物10只,观察CLA对肥胖大鼠血清游离脂肪酸(FFA)、胰岛素、血糖水平的影响,并应用RT-PCR法检测脂肪酸转移蛋白(FATP)、酰基CoA合成酶(ACS)、过氧化物酶体增殖物活性受体γ(PPARγ)mRNA的表达水平。结果:高脂组大鼠血清FFA、胰岛素和血糖水平显著高于对照组,CLA可降低肥胖大鼠血清FFA、胰岛素、血糖水平,并且可增加肥胖大鼠脂肪组织FATP、ACS、PPARγmRNA的表达水平。结论:CLA可通过激活PPARγ上调FATP、ACS基因的表达,改善肥胖大鼠的胰岛素抵抗。     

Dietary conjugated linoleic acid reduces lipid peroxidation by increasing oxidative stability in rats

The antioxidative effect of conjugated linoleic acid (CLA) was examined by determining lipid peroxidation and antioxidative enzyme activities. Male Sprague-Dawley rats were fed one of the experimental diets-normal diet, vitamin E-deficient control diet, 0.5% CLA vitamin E-deficient diet, or 1.5% CLA vitamin E-deficient diet for 5 wk. Hepatic thiobarbituric acid reactive substances (TBARS) were increased in the vitamin E-deficient control group, but they were was significantly lowered in the CLA groups. Similarly, hepatic glutathione peroxidase activity was increased in the vitamin E-deficient diet and reduced by CLA supplementation. In addition, CLA caused a significant decrease in superoxide dismutase activity while having no effect on catalase activity. Analyses of the fatty acid composition revealed that dietary CLA was incorporated into hepatic microsomal membrane dose-dependently. Compared to the vitamin E-deficient control, CLA resulted in significantly higher saturated and monounsaturated fatty acids (palmitic and oleic acids) while lowering levels of oxidation-susceptible polyunsaturated fatty acids (linoleic, linolenic, and arachidonic acids) in both plasma and hepatic membrane. The concentrations of plasma cholesterol and triacylglycerol (TG) were lower in the 1.5% CLA group than in other groups. These results suggest that dietary CLA has antiatherosclerotic and antioxidant activity by increasing oxidative stability in plasma and hepatic membrane in the vitamin E-deficient rats.     

Trans-10, cis-12, but not cis-9, trans-11, conjugated linoleic acid attenuates lipogenesis in primary cultures of stromal vascular cells from human adipose tissue

We have previously shown that both a commercially available mixture of conjugated linoleic acid (CLA) isomers and the trans-10, cis-12 isomer of CLA reduced the triglyceride (TG) content and induced apoptosis in differentiating cultures of murine 3T3-L1 preadipocytes. However, the influence of CLA isomers on differentiating human (pre)adipocytes is unknown. Therefore, we conducted a series of studies using primary cultures of stromal vascular cells isolated from human adipose tissue to determine: 1) the influence of seeding density and thiazolidinedione (TZD) concentration on TG content; 2) the chronic dose response of cis-9, trans-11 CLA vs. trans-10, cis-12 CLA on TG content; 3) whether chronic linoleic acid supplementation could rescue the TG content of CLA-treated cultures; and 4) whether trans-10, cis-12-mediated reduction in cellular TG was due to decreased lipogenesis and/or increased lipolysis. In expt. 1, the TG content [micromol/(L x 10(6) cells)] increased as both seeding density and TZD concentration increased. For example, cultures seeded at 4 x 10(4) cells/cm(2) and supplemented with 10 micromol/L BRL 49653 had 10-fold more TG than similarly seeded cultures without BRL 49653. In expt. 2, TG content decreased as the level of trans-10, cis-12 CLA increased from 1 to 10 micromol/L, whereas the TG content increased with increasing concentrations of either linoleic acid or cis-9, trans-11 CLA. In expt. 3, linoleic acid supplementation restored the TG content of cultures treated with trans-10, cis-12 CLA compared with cultures treated with CLA alone, suggesting that attenuation of TG content by CLA is reversible. In expt. 4, glucose incorporation into total lipid decreased with increasing levels of trans-10, cis-12 CLA, whereas neither CLA isomer acutely affected lipolysis. These data suggest that the reported antiobesity actions of a supplement containing a crude mixture of CLA isomers given to humans may be due to inhibition of lipogenesis by the trans-10, cis-12 isomer.     

Short-term feeding of conjugated linoleic acid does not induce hepatic steatosis in C57BL/6J mice

We investigated the effect of short-term feeding of conjugated linoleic acid (CLA) on adipose tissue weights, liver weight, hepatic lipid metabolism, and serum lipoprotein profiles in C57BL/6J mice. Mice were fed semi-synthetic diets containing either 6%, high-linoleic safflower oil (HL-SAF) or 4% HL-SAF+2% CLA for 1 wk. Short-term feeding of CLA showed an anti-obesity effect without inducing hepatomegaly in mice. In addition to the decline of hepatic triglyceride concentration, significant inhibition of A9 desaturation of fatty acid in the total liver lipids was found in CLA-fed mice. The CLA diet significantly increased the activities of peroxisomal beta-oxidation and decreased the activities of diacylglycerol acyltransferase, a triglyceride synthesis-related enzyme, in the liver. Moreover, serum lipoprotein profiles of CLA-fed mice showed preferable changes in the atherogenic indices. However, serum leptin and adiponectin were drastically decreased by CLA feeding, suggesting that prolonged administration of CLA would induce further decrease of serum adipocytokine levels, which may be a cause of lipodystrophy in mice. These results show that short-term feeding of CLA does not induce adverse effect in C57BL/6J mice.     

The 10trans, 12cis isomer of conjugated linoleic acid promotes energy metabolism in OLETF rats

OBJECTIVE: We investigated the effect of conjugated linoleic acid (CLA) on energy metabolism in Otsuka Long-Evans Tokushima Fatty (OLETF) rats. METHODS: In experiment 1, male OLETF rats were fed either control diet, 10% safflower oil or CLA diet, 9% safflower oil plus 1% CLA for 4 wk. In experiment 2, male OLETF rats were fed either 9c,11t-CLA diet, 9% safflower oil plus 1% 9c,11t-CLA-rich oil or 10t,12c-CLA diet, 9% safflower oil plus 1% 10t,12c-CLA-rich oil for 10 d. RESULTS: In experiment 1, after 4 wk of feeding, serum and hepatic triacylglycerol concentrations in the CLA group were decreased significantly as compared with the control group. The CLA diet increased oxygen consumption and energy expenditure as compared with the control diet in OLETF rats. In experiment 2, a significant reduction of serum and hepatic triacylglycerol concentrations was seen in the 10t,12c-CLA group as opposed to the 9c,11t-CLA group. Oxygen consumption and energy expenditure were significantly higher in the 10t,12c-CLA group than in the 9c,11t-CLA group. CONCLUSIONS: These results demonstrated that the hypolipidemic effect and the enhancement of energy metabolism by CLA can be attributed to the effect of the 10t,12c-CLA isomer.     

共轭亚油酸对肥胖大鼠脂肪组织瘦素的影响

目的　通过共轭亚油酸 (CLA)对高脂高糖肥胖模型大鼠的干预后 ,观察大鼠体重 ,血脂、以及脂肪组织中的瘦素表达水平的变化 ,探讨CLA对肥胖大鼠影响作用及其机制。方法　选取成年雌性Wistar大鼠 5 0只 ,按体重随机分为 5组 ,1组正常对照组 ,4组模型组 ,模型组高脂高糖饮食 1个月后 ,选出体重大于 2 30 g的大鼠 2 8只 ,在按体重水平随机分为 4组 :肥胖对照组和 3组共轭亚油酸干预组 :低 0 .4 ,中 0 . 8,高 1 6 g/ (kg·bw)。灌胃给予共轭亚油酸4周后 ,测定体重变化和血清中血脂水平 ,Western杂交观察大鼠脂肪组织中瘦素的表达。结果　与肥胖模型对照组相比 ,共轭亚油酸可明显减轻大鼠体重 ,降低大鼠血清甘油三脂水平 ,减少脂肪组织瘦素 (leptin)表达水平。 结论　共轭亚油酸能降低大鼠体重、血脂水平 ,其机制可能是通过调节瘦素表达的来影响脂肪代谢。     

Trans-11 vaccenic acid dietary supplementation induces hypolipidemic effects in JCR:LA-cp rats

Trans-11 vaccenic acid [VA; 18:1(n-9)] is a positional and geometric isomer of oleic acid and is the precursor to conjugated linoleic acid (CLA) in humans. Despite VA being the predominant trans monoene in ruminant-derived lipids, very little is known about its nutritional bioactivity, particularly in conditions of chronic metabolic disorders, including obesity, insulin resistance, and/or dyslipidemia. The aim of this study was to assess the potential of VA to improve dyslipidemia, insulin sensitivity, or inflammatory status in obese and insulin-resistant JCR:LA-cp rats. The obese rats and age-matched lean littermates were fed a control diet or a control diet supplemented with 1.5% (wt:wt) VA for a period of 3 wk. The incorporation of VA and subsequent conversion to CLA in triglyceride was measured in adipose tissue. Glucose and insulin metabolism were assessed via a conscious adapted meal tolerance test procedure. Plasma lipids as well as serum inflammatory cytokine concentrations were measured by commercially available assays. VA supplementation did not result in any observable adverse health effects in either lean or obese JCR:LA-cp rats. After 3 wk of feeding, body weight, food intake, and glucose/insulin metabolism did not differ between VA-supplemented and control groups. The incorporation of VA and CLA into adipose triglycerides in obese rats fed VA increased by 1.5-fold and 6.5-fold, respectively, compared with obese rats fed the control diet. The most striking effect was a 40% decrease (P < 0.05) in fasting triglyceride concentrations in VA-treated obese rats relative to obese controls. Serum Il-10 concentration was decreased by VA, regardless of genotype (P < 0.05). In conclusion, short-term dietary supplementation of 1.5% VA did not result in any detrimental metabolic effects in JCR:LA-cp rats. In contrast, dietary VA had substantial hypo-triglyceridemic effects, suggesting a new bioactivity of this fatty acid that is typically found in ruminant-derived food products.     

Effect of dietary conjugated linoleic acid isomers on lipid metabolism in hamsters fed high-carbohydrate and high-fat diets

Dietary conjugated linoleic acids (CLA) have been reported to have a number of isomer-dependent effects on lipid metabolism including reduction in adipose tissue deposition, changes in plasma lipoprotein concentrations and hepatic lipid accumulation. The aim of this study was to compare the effect of individual CLA isomers against lipogenic and high 'Western' fat background diets. Golden Syrian hamsters were fed a high-carbohydrate rodent chow or chow supplemented with 17.25 % fat formulated to represent the type and amount of fatty acids found in a typical 'Western' diet (including 0.2 % cholesterol). Diets were further supplemented with 0.25 % (w/w) rapeseed oil, cis9, trans11 (c9,t11)-CLA or trans10, cis12 (t10,c12)-CLA. Neither isomer had a significant impact on plasma lipid or lipoprotein concentrations. The t10,c12-CLA isomer significantly reduced perirenal adipose tissue depot mass. While adipose tissue acetyl CoA carboxylase and fatty acid synthase mRNA concentrations (as measured by quantitative PCR) were unaffected by CLA, lipoprotein lipase mRNA was specifically reduced by t10,c12-CLA, on both background diets (P < 0.001). This was associated with a specific reduction of sterol regulatory element binding protein 1c expression in perirenal adipose tissue (P = 0.018). The isomers appear to have divergent effects on liver TAG content with c9,t11-CLA producing lower concentrations than t10,c12-CLA. We conclude that t10,c12-CLA modestly reduces adipose tissue deposition in the Golden Syrian hamster independently of background diet and this may possibly result from reduced uptake of lipoprotein fatty acids, as a consequence of reduced lipoprotein lipase gene expression.     

Trans-10, cis-12 conjugated linoleic acid increases fatty acid oxidation in 3T3-L1 preadipocytes

The purpose of this study was to examine the effect of 0-50 micromol/L trans-10, cis-12 conjugated linoleic acid (CLA) and cis-9, trans-11 CLA isomers on lipid and glucose metabolism in cultures of differentiating 3T3-L1 preadipocytes. Specifically, we investigated the effects of 6 d of CLA treatment on the following: 1) (14)C-glucose and (14)C-oleic acid incorporation and esterification into lipid; 2) (14)C-glucose and (14)C-fatty acid oxidation; and 3) basal and isoproterenol-stimulated lipolysis. Trans-10, cis-12 CLA supplementation (25 and 50 micromol/L) increased both (14)C-glucose and (14)C-oleic acid incorporation into the cellular lipid fraction, which was primarily triglyceride (TG), compared with bovine serum albumin (BSA) controls. Although glucose oxidation ((14)C-glucose to (14)C-CO(2)) was unaffected by CLA supplementation, oleic acid oxidation ((14)C-oleic acid to (14)C-CO(2)) was increased by approximately 55% in the presence of 50 micromol/L trans-10, cis-12 CLA compared with BSA controls. In contrast, 50 micromol/L linoleic acid (LA) and cis-9, trans-11 CLA-treated cultures had approximately 50% lower CO(2) production from (14)C-oleic acid compared with control cultures after 6 d of fatty acid exposure. Finally, 50 micromol/L trans-10, cis-12 CLA modestly increased basal, but not isoproterenol-stimulated lipolysis compared with control cultures. Thus, the TG-lowering actions of trans-10, cis-12 CLA in cultures of 3T3-L1 preadipocytes may be via increased fatty acid oxidation, which exceeded its stimulatory effects on glucose and oleic acid incorporation into lipid.     

共轭亚油酸对肥胖大鼠UCP2基因表达的影响

目的 通过研究共轭亚油酸(Conjugated linoleic acid，CLA)对饮食诱导肥胖大鼠解偶联蛋白2(Unconpling protein 2，UCP2)基因表达的影响，探讨CLA降低体重、体脂作用的机制。方法 选用雄性Wistar大鼠，随机分为对照组、高脂组、高脂 CLA组(每100g饲料含CLA分别为0．75，1．50，3．00g)，每组动物10只，观察CLA对肥胖大鼠体重、体脂、血脂水平的影响，并应用RT-PCR的方法检测UCP2 mRNA的表达水平。结果 CLA可降低饮食诱导肥胖大鼠的体重和体脂含量，降低血清甘油三酯、胆固醇、游离脂肪酸水平，并可增加肥胖大鼠脂肪组织UCP2 mRNA的表达水平。结论 CLA可改善肥胖大鼠的脂代谢紊乱，增加UCP2基因的表达，发挥降低体重、体脂的作用。