Supplemental Conjugated Linoleic Acid Consumption Does Not Influence Milk Macronutrient Contents in all Healthy Lactating Women

The term “conjugated linoleic acid” (CLA) refers to a group of positional and geometric isomers that are derived from linoleic acid and are found primarily in meat and milk products from ruminant animals. Due to the array of putative benefits associated with various forms of CLA, there has been recent interest in supplementing human diets with these fatty acids especially when weight loss is desired. However, in many animal models, CLA has been shown to decrease milk fat production. There is some concern, therefore, that maternal CLA supplementation during lactation might inadvertently decrease nutrient supply to the nursing infant. However, there is only limited research on the effect of CLA consumption on milk fat content in women. Based on previously published work from our laboratory, we hypothesized that CLA supplementation would reduce the milk fat percentage in lactating women in a dose-dependent manner. Breastfeeding women (n = 12) were assigned randomly to treatments of 4 g/day safflower oil (SFO), 2 g/day CLA plus 2 g/day SFO, or 4 g/day CLA in a double blind, 3 × 3 Latin square design. Conjugated linoleic acid supplements contained approximately equal amounts of cis9,trans11–18:2 and trans10,cis12–18:2; the two most common isoforms of CLA. Milk was collected by complete breast expression on the last day (day 5) of each intervention period and analyzed for macronutrient and fatty acid composition. On day 4 of each intervention period, infant milk consumption was estimated by 24 h weighing of the infant. Washout periods were 9 days in length. We observed a dose-dependent increase in the concentrations of cis9,trans11–18:2 and trans10,cis12–18:2 in the milk fat. However, we detected neither a change in overall macronutrient composition nor infant milk consumption. These data do not support those obtained from animal models or our previous human work suggesting that consumption of CLA mixtures necessarily reduces milk fat. It is possible that either (1) the interpretation of our previously published data should be reevaluated, and/or (2) there are important intra- and inter-species differences in this regard.     

Dietary Conjugated Linoleic Acid-c9t11 Prevents Collagen-Induced Arthritis,Whereas Conjugated Linoleic Acid-t10c12 Increases Arthritic Severity

Two conjugated linoleic acid (CLA) isomers, cis‐9, trans‐11 (CLAc9t11) and trans‐10, cis‐12 (CLAt10c12), reduce inflammation in a number of animal models, including collagen‐induced arthritis (CA). However, little is known about the ability of individual CLA isomers to prevent autoimmune disease onset. Evidence that mixed isomer CLA drives T helper cell (Th) 1 responses suggests that CLA, or a specific isomer, exacerbates onset of Th1 autoimmune diseases. In two experiments, we examined if prior dietary exposure to CLAt10c12 (experiment 1) or CLAc9t11 (experiment 2) affected the incidence or severity of CA. DBA/1 mice were fed a semi purified diet with either 6% corn oil (CO, w/w), 5.75% CO plus 0.25% CLAt10c12, or 5.5% CO plus 0.5% CLAc9t11 prior to arthritis development. Arthritis incidence and severity, anti‐collagen antibodies, paw cytokines, and hepatic fatty acids were measured. CLAt10c12 had no effect on arthritis incidence but increased arthritic severity (42%, P = 0.02); however, CLAc9t11 decreased arthritis incidence 39% compared to CO fed mice (P = 0.01), but had no effect on disease severity. CLAt10c12‐induced increase in anti‐collagen type II IgG antibodies may be a mechanism by which this isomer increased arthritic severity, and CLAc9t11‐induced increase in Th2 paw cytokines (IL‐4 and IL‐10, P ≤ 0.04) may explain how CLAc9t11 reduced the arthritis incidence. While both isomers are well known to reduce inflammation in arthritic mice, these new data suggest isomer differences when fed prior to autoimmune disease.     

Low Dietary c9t11-Conjugated Linoleic Acid Intake from Dairy Fat or Supplements Reduces Inflammation in Collagen-Induced Arthritis

Dietary cis‐9,trans‐11 (c9t11) conjugated linoleic acid (CLA) fed at 0.5 % w/w was previously shown to attenuate inflammation in the murine collagen‐induced (CA) arthritis model, and growing evidence implicates c9t11‐CLA as a major anti‐inflammatory component of dairy fat. To understand c9t11‐CLA's contribution to dairy fat's anti‐inflammatory action, the minimum amount of dietary c9t11‐CLA needed to reduce inflammation must be determined. This study had two objectives: (1) determine the minimum dietary anti‐inflammatory c9t11‐CLA intake level in the CA model, and (2) compare this to anti‐inflammatory effects of dairy fat (non‐enriched, naturally c9t11‐CLA‐enriched, or c9t11‐CLA‐supplemented). Mice received the following dietary fat treatments (w/w) post arthritis onset: corn oil (6 % CO), 0.125, 0.25, 0.375, and 0.5 % c9t11‐CLA, control butter (6 % CB), c9t11‐enriched butter (6 % EB), or c9t11‐CLA‐supplemented butter (6 % SB, containing 0.2 % c9t11‐CLA). Paw arthritic severity and pad swelling were scored and measured, respectively, over an 84‐day study period. All c9t11‐CLA and butter diets decreased the arthritic score (25–51 %, P < 0.01) and paw swelling (8–11 %, P < 0.01). Throughout the study, plasma tumor necrosis factor (TNFα) was elevated in CO‐fed arthritic mice compared to non‐arthritic (NA) mice but was reduced in 0.5 % c9t11‐CLA‐ and EB‐fed mice. Interleukin‐1β and IL‐6 were increased in arthritic CO‐fed mice compared to NA mice but were reduced in 0.5 % c9t11‐CLA‐ and EB‐fed mice through day 42. In conclusion, 0.125 % c9t11‐CLA reduced clinical arthritis as effectively as higher doses, and decreased arthritis in CB‐fed mice suggested that the minimal anti‐inflammatory levels of c9t11‐CLA might be below 0.125 %.     

A Soap-Free Strategy for One-Pot Synthesizing Conjugated Linoleic Acid: Alkali Isomerization of Linoleic Acid through Preferential Esterification Pathway

Conjugated linoleic acid (CLA) exhibits beneficial biological activities but possesses poor natural abundance, which is usually obtained by alkali isomerization of linoleic acid (LNA). The one-pot alkali isomerization consists two reactions, firstly saponifying LNA and then isomerizing linoleate. This current process has been limited by two drawbacks, the overconsumption of both alkali and solvent, as well as the weak mass/heat transfer of the viscous paste of reaction mixture that limits the synthesis scale. The present study alternated the reaction pathway with a soap-free preferential esterification pathway, that is, firstly employing slight NaOH to induce the esterification of LNA and diol (the reaction solvent), then conducting alkali isomerization of the intermediate alkyl linoleate instead of sodium linoleate. In this developed one-pot procedure, a CLA yield of 90% and the selectivity of the desired isomers (“c9, t11” and “t10, c12” CLA) of 82.4% were obtained; and it reduced the consumption of NaOH and the solvent by 60% and 25% comparing to the current soap pathway, respectively; Yet the result is comparative to that obtained with assistant of microwave/ultrasound in even longer reaction time. In this way, the two drawbacks can be overcome and the green characteristics of the current process was well kept.     

Oleic Acid Attenuates trans-10,cis-12 Conjugated Linoleic Acid-Mediated Inflammatory Gene Expression in Human Adipocytes

The weight loss supplement conjugated linoleic acid (CLA) consists of an equal mixture of trans-10,cis-12 (10,12) and cis-9,trans-11 (9,11) isomers. However, high levels of mixed CLA isomers, or the 10,12 isomer, causes chronic inflammation, lipodystrophy, or insulin resistance. We previously demonstrated that 10,12 CLA decreases de novo lipid synthesis along with the abundance and activity of stearoyl-CoA desaturase (SCD)-1, a δ-9 desaturase essential for the synthesis of monounsaturated fatty acids (MUFA). Thus, we hypothesized that the 10,12 CLA-mediated decrease in SCD-1, with the subsequent decrease in MUFA, was responsible for the observed effects. To test this hypothesis, 10,12 CLA-treated human adipocytes were supplemented with oleic acid for 12?h to 7?days, and inflammatory gene expression, insulin-stimulated glucose uptake, and lipid content were measured. Oleic acid reduced inflammatory gene expression in a dose-dependent manner, and restored the lipid content of 10,12 CLA-treated adipocytes without improving insulin-stimulated glucose uptake. In contrast, supplementation with stearic acid, a substrate for SCD-1, or 9,11 CLA did not prevent inflammatory gene expression by 10,12 CLA. Notably, 10,12 CLA impacted the expression of several G-protein coupled receptors that was attenuated by oleic acid. Collectively, these data show that oleic acid attenuates 10,12 CLA-induced inflammatory gene expression and lipid content, possibly by alleviating cell stress caused by the inhibition of MUFA needed for phospholipid and neutral lipid synthesis.     

A simple method of preparation of methyl trans-10,cis-12- and cis-9,trans-11-octadecadienoates from methyl linoleate

Pure conjugated isomers of linoleic acid were prepared on a large scale by alkali-isomerization of purified methyl linoleate. The methyl esters of alkali-isomerized linoleic acid contained mainly the methyl cis-9,trans-11- and trans-10,cis-12-octadecadienoates (44 and 47%, respectively). These two isomers were then separated and purified by a series of low-temperature crystallizations from acetone. The isomeric purity obtained for the cis-9,trans-11-octadecadienoate isomer was >90% and that of the trans-10,cis-12-octadecadienoate isomer was 89 to 97%. The isolated yield of the two isomers corresponded to 18 and 25.7%, respectively, of the starting material. The structure of the two isomers was confirmed using partial hydrazine reduction, silver nitrate-thin-layer chromatography of the resulting monoenes and gas chromatography coupled with mass spectrometry of the 4,4-dimethyloxazoline derivatives. Fourier transform infrared spectroscopy of the monoenes gave the confirmation of the geometry of each double bond.     

Physical Properties of Two Isomers of Conjugated Linoleic Acid

Thermal properties, powder X-ray diffraction patterns and FT-IR absorption spectra of crystals of two isomers of conjugated linoleic acid (CLA), 9-cis, 11-trans-CLA (c9t11), 10-trans, 12-cis-CLA (t10c12) were examined. To search for polymorphic modifications, we carefully performed crystallization from melt and solution phases, and isolated one type of crystalline form in c9t11 and t10c12. The melting temperature (T _m) was 14.9 °C, enthalpy of fusion (ΔH) was 38.7 kJ/mol, and entropy of fusion (ΔS) was 134 J/mol K for c9t11, and T _m = 19.8 °C, ΔH = 35.6 kJ/mol and ΔS = 122 J/mol K for t10c12. The X-ray diffraction and FT-IR measurements indicated O_⊥ subcell packing in the crystals of c9t11 and t10c12, and long spacing values of 4.22 nm for c9t11 and 3.88 nm for t10c12. The unique molecular structures of the two isomers of CLA are discussed in comparison to the polymorphism of oleic acid, petroselinic acid, elaidic acid and linoleic acid, all of which are unsaturated fatty acids having the same carbon number of 18 as that of the two CLA isomers.     

共轭亚油酸乙酯的合成

采用间歇式反应 ,以硫酸、磷酸、对甲苯磺酸为催化剂对共轭亚油酸乙酯进行了合成 ,并采用正交实验设计研究了物料比、反应温度、反应时间、催化剂用量对产品收率和品质的影响。硫酸、对甲苯磺酸催化活性佳 ,磷酸催化活性差。得到了如下合成工艺条件 :硫酸催化 ;n(共轭亚油酸 )∶n(无水乙醇 ) =1∶6;酯化反应温度 76℃ ;反应时间 1h ;催化剂用量为共轭亚油酸质量的 2 5 % ,收率可达 75 % ,产品w(共轭亚油酸乙酯 ) =77%～ 82 %。     

酯交换法合成共轭亚油酸三甘酯

采用酯交换反应,以共轭亚油酸乙酯、甘油为原料,脂肪酸钾为均相化试剂,无水K2CO3为催化剂,在压力～1 0kPa下反应制得共轭亚油酸三甘酯。合成工艺条件:n(共轭亚油酸乙酯)∶n(甘油)=6∶1;酯化反应温度140℃;反应时间～1 5h;无水K2CO3用量为共轭亚油酸乙酯质量的0 5%～1%;按统计平均值,产物三甘酯脂肪酸侧链中w(共轭亚油酸)>80%;产率(以甘油计)60%～65%。     

Conjugated Linoleic Acid Isomers Trans‐10, Cis‐12 and Cis‐9, Trans‐11 Prevent Collagen‐Induced Arthritis in a Direct Comparison

Mixed‐isomer conjugated linoleic acid (CLA) and the individual isomers, trans‐10, cis‐12 (CLAt10c12) and cis‐9, trans‐11 (CLAc9t11), decrease severity of collagen‐induced arthritis (CA) when consumed after disease onset. Few studies have been conducted exploring the role of CLA in the prevention of autoimmune diseases. These studies suggest that isomer‐specific effects may be occurring; however, a direct comparison of CLAt10c12 and CLAc9t11 has yet to be conducted. A study to compare the ability of CLAt10c12 and CLAc9t11 to prevent CA and assess their effects on early inflammation was performed. DBA/1 mice were fed a semipurified diet containing 6% corn oil (CO), 5.5% CO and 0.5% CLAt10c12, or 5.5% CO and 0.5% CLAc9t11 (n = 27 per diet) starting three weeks before CA primary immunization. Effects on disease incidence and severity, anticollagen antibodies, plasma and paw cytokines, and hepatic fatty acids were measured. Arthritis incidence was reduced by a minimum of 34% in mice fed either CLA isomer compared to those fed CO diet (p = 0.06). In mice that did develop arthritis (n = 9–12 mice per treatment), CLAt10c12 reduced arthritic severity to a greater extent than CLAc9t11 and CO (p = 0.03). CLA isomer treatment attenuated the increased hepatic arachidonic acid (ARA; 20:4n‐6) observed with arthritis at one‐week postonset (p = 0.03), while no differences in anticollagen antibodies or cytokines were observed between dietary treatments. These results suggest that CLA isomers may be effective at preventing specific immune‐mediated inflammatory diseases, in part, through modulation of the ARA cascade.     

Dietary Conjugated Linoleic Acid Renal Benefits and Possible Toxicity vary with Isomer,Dose and Gender in Rat Polycystic Kidney Disease

Conjugated linoleic acid (CLA) is anti-proliferative and anti-inflammatory in the Han:SPRD-cy rat model of kidney disease. We used different doses of CLA and examined effects on renal histological benefit, the renal PPARgamma system and hepatic and renal levels of CLA isomers. Male and female offspring of Han:SPRD-cy heterozygotes were fed diets with 0, 1 or 2% CLA isomer mixture for 12 weeks before dual-energy X-ray absorptiometry, harvest of renal and hepatic tissue for histologic and lipid analysis. Both CLA diets reduced body fat content in both genders but did not change lean body mass. CLA produced a dose dependent reduction in female renal cystic change. CLA reduced fibrosis, but this reduction was significantly less with higher dose in males. CLA reduced macrophage infiltration, tissue oxidized LDL content and proliferation of epithelial cells. Serum creatinine rose significantly in female animals fed CLA diets. CLA treatment did not change PPARgamma activation. A significant negative correlation with renal content of the 18:2 c9,t11 isomer and the sum of histologic effects was identified. CLA reduces histologic renal injury in the Han:SPRD-cy rat model probably inversely proportionate to c9,t11 renal content. Possible functional CLA toxicity at high dose in female animals warrants further exploration.     

Body Compositional Changes and Growth Alteration in Chicks from Hens Fed Conjugated Linoleic Acid

Effects of feeding conjugated linoleic acid (CLA) to hens on progeny chick development and composition at hatch (NHC) and three weeks of age (TWC) were assessed. CLA (0 or 0.5%, composed of mixed isomers of cis-9,trans-11 or trans-10,cis-12-CLA) was fed to hens with either safflower (SO) or olive oil (OO) (3 or 3.5%) to assure successful hatch for 2 weeks prior to collection for incubation. Maternal CLA feeding had no effect on hatchability, but improved egg fertility (p < 0.05). Maternal feeding of CLA with SO increased 21 day-old progeny growth, while CLA with OO decreased growth (oil*CLA, p < 0.05). In 25 day-old chicks (TWC), but not NHC, maternal CLA decreased the proportion of total body water (p < 0.05) and increased body ash (p < 0.05). While monounsaturated fatty acids were decreased and saturated fatty acids increased in eggs and NHC from hens fed CLA, no differences in fatty acid composition were observed in chicks at 25 days of age from hens fed CLA. Maternal CLA feeding resulted in the presence of c9,t11 and t10,c12-CLA in NHC, but only c9,t11 in the TWC. In conclusion, hens fed CLA led to improved fertility and altered body composition at 3 weeks of age.     

碱法异构化亚油酸甲酯制备共轭亚油酸

该文探索在乙二醇溶剂中以氢氧化钠碱法异构化亚油酸甲酯制备共轭亚油酸的方法,适宜的异构化条件为m(氢氧化钠)∶m(亚油酸甲酯)∶m(乙二醇)=1∶5∶8.4,170℃反应4 h,亚油酸甲酯转化率和共轭亚油酸产率分别为92.4%和89.3%。该法比目前常用的亚油酸原料法的优越之处体现在:以氢氧化钠取代常用碱氢氧化钾,降低成本;以亚油酸甲酯取代亚油酸为原料,避免了原料本身大量消耗碱;反应初期避免原料大量皂化,减小了体系的传质阻力,因而减少了溶剂乙二醇消耗量。     

Direct Isomerization of Linoleic Acid to Conjugated Linoleic Acids (CLA) using Gold Catalysts

Supported gold catalysts, e.g., Au on Al₂O₃, Fe₂O₃, CeO₂, MnO₂, TiO₂, ZrO₂, activated carbon, titanium silicalite TS‐1, were prepared and used for the isomerization of linoleic acid (cis‐9,cis‐12‐octadecadienoic acid) to conjugated linoleic acids (CLA) in the presence of hydrogen at 165 °C in a batch reactor. The best results were obtained using a catalyst with 2 wt % Au on TS‐1, which exhibits a high selectivity (78 %) towards CLA. The two biologically active target CLA isomers, i.e., cis‐9,trans‐11‐CLA and trans‐10,cis‐12‐CLA, were the main products. During the isomerization of linoleic acid to CLA, consecutive reactions also took place. These were the hydrogenation of linoleic acid and CLA to monounsaturated octadecenoic acids and the further hydrogenation of monounsaturated acids to stearic acid. Thus, gold catalysts are capable of isomerizing linoleic acid to CLA and hydrogenating their double bonds to an extent that depends on the Au catalyst used.     

The Effects of Simultaneous Administration of Dietary Conjugated Linoleic Acid and Telmisartan on Cardiovascular Risks in Rats

Dietary conjugated linoleic acid (CLA) and the antihypertensive drug, telmisartan, have both been shown to modify cardiovascular risks. The effects of a combination of these two agents have, however, not been investigated. This 20 week study sought to assess the therapeutic potential of a CLA/telmisartan co-administration in rats fed a high-fructose high-fat diet. Thirty-three male Sprague–Dawley rats were randomly assigned to five experimental groups, including control, losartan, telmisartan, CLA, and CLA + telmisartan-treated animals. Body weight, blood pressure, and blood levels of lipids, glucose, insulin, and inflammatory markers were measured. Co-administration of CLA and telmisartan resulted in significant (P < 0.05) reductions in body weight, visceral fat, serum total cholesterol, triglycerides, glucose, plasma insulin concentrations, and systolic blood pressure compared with those in the control group. Moreover, plasma levels of IL1-α and IFN-γ were reduced and levels of IL1-β, IL-4, IL-6, and IL-10, plus TNF-α were increased in the co-therapy group, compared with controls. In conclusion, this study suggests that a combination of CLA with telmisartan may modify several risk factors of cardiovascular disease commonly seen in metabolic syndrome. This combination of nutraceuticals and pharmaceuticals may be a safe and cost-effective strategy in a number of high-risk subjects. Future studies will further document clinical benefits of such combination therapy.     

The Production of an Experimental Table Margarine Enriched with Conjugated Linoleic Acid (CLA): Physical Properties

Even though conjugated linoleic acid (CLA) is known to have some beneficial effects on the human body, its consumption has decreased over the past 20 years due to the replacement of animal fats by vegetable oils. In this study, using the structured lipid (SL) containing CLA, an experimental table margarine enriched with CLA was produced and stored for 3 months at two temperatures prior to performing the relevant analyses. The GC results showed that the margarine fat had 10.6% CLA. The solid fat content was the highest in week 0 in all samples, which then decreased during storage but the hardness increased. An increment in dropping point was also observed in the samples. In week 0, all the samples had the β′ crystal as the predominant crystal form but a crystal transformation from β′ to β was observed during storage.     

Impact of Conjugated Linoleic Acid (CLA) on Skeletal Muscle Metabolism

Conjugated linoleic acid (CLA) has garnered special attention as a food bioactive compound that prevents and attenuates obesity. Although most studies on the effects of CLA on obesity have focused on the reduction of body fat, a number of studies have demonstrated that CLA also increases lean body mass and enhances physical performances. It has been suggested that these effects may be due in part to physiological changes in the skeletal muscle, such as changes in the muscle fiber type transformation, alteration of the intracellular signaling pathways in muscle metabolism, or energy metabolism. However, the mode of action for CLA in muscle metabolism is not completely understood. The purpose of this review is to summarize the current knowledge of the effects of CLA on skeletal muscle metabolism. Given that CLA not only reduces body fat, but also improves lean mass, there is great potential for the use of CLA to improve muscle metabolism, which would have a significant health impact.     

Optimization of Lipase-Catalyzed Fractionation of Two Conjugated Linoleic Acid (CLA) Isomers

The separation of two isomers of conjugated linoleic acid is highly significant since each exhibits different biochemical properties. The aim of this study was to investigate and optimize several factors affecting the esterification of l-menthol with the c9,t11-CLA isomer in an organic solvent-free system using lipase from Candida rugosa (Lipase AY-30). D-optimal design with 5 factors and 3 levels were employed to evaluate the effects of synthesis parameters; reaction time (8–24 h), temperature (30–50 °C), enzyme content (2–20 U/ml), substrate molar ratio of conjugated linoleic acid oil to l-menthol (2:1–1:2) and pH (6–8) on esterification of c9,t11-CLA with l-menthol. Based on the analysis of the residual amount of c9,t11-CLA in the free fatty acid fraction after just one-step esterification, the optimum synthesis conditions were as follows: reaction time 23.12 h, temperature 32.65 °C, enzyme amount 135.40 U, molar ratio of CLA oil to l-menthol at 1:1.7 and pH at 7.7; the lowest purity of c9,t11-CLA in free fatty acid fraction based on the total content of c9,t11 and t10,c12-CLA isomers was 8.6 %.