Lipoxygenase inhibitors inhibit heparin-releasable lipoprotein lipase activity in 3T3-L1 adipocytes and enhance body fat reduction in mice by conjugated linoleic acid

Health Benefits of Anti-aging Drugs

Aging, as a physiological process mediated by numerous regulatory pathways and transcription factors, is manifested by continuous progressive functional decline and increasing risk of chronic diseases. There is an increasing interest to identify pharmacological agents for treatment and prevention of age-related disease in humans. Animal models play an important role in identification and testing of anti-aging compounds; this step is crucial before the drug will enter human clinical trial or will be introduced to human medicine. One of the main goals of animal studies is better understanding of mechanistic targets, therapeutic implications and side-effects of the drug, which may be later translated into humans. In this chapter, we summarized the effects of different drugs reported to extend the lifespan in model organisms from round worms to rodents. Resveratrol, rapamycin, metformin and aspirin, showing effectiveness in model organism life- and healthspan extension mainly target the master regulators of aging such as mTOR, FOXO and PGC1α, affecting autophagy, inflammation and oxidative stress. In humans, these drugs were demonstrated to reduce inflammation, prevent CVD, and slow down the functional decline in certain organs. Additionally, potential anti-aging pharmacologic agents inhibit cancerogenesis, interfering with certain aspects of cell metabolism, proliferation, angioneogenesis and apoptosis.

CLA Has a Useful Effect on Bone Markers in Patients with Rheumatoid Arthritis

Rheumatoid arthritis is a systemic, chronic disease which may increase the risk of osteoporosis. This study was carried out in order to examine the effect of conjugated linoleic acid (CLA) on bone markers in rheumatoid arthritis disease which is the most common autoimmune disease. The present study is a randomized double-blind clinical trial. Subjects included 52 patients with active rheumatoid arthritis who were divided into two groups. Group I received standard treatment plus 2 daily 1.25 g capsules (Containing about 2 g of 9-cis 11-trans isomer and 10-cis 12-trans isomer in ratio of 50 -50 CLA in glycerinated form), Group II received standard treatment plus 2 Placebo 1.25 g capsules containing sunflower oil with high oleic acid. Telopeptides C, osteocalcin, and MMP3 were analyzed by ELISA method, PGE₂ was done by competitive enzymatic immunoassay method, and IGF-1 was analyzed by the IRMA method based on the sandwich method and ALK-P of bone. Before and after the intervention, the questionnaires about general information, nutrition assessment and medical history were filled out by the subjects. Nutritional assessment was done by a 24-h record questionnaire for the three-day diet. The results were analyzed using SPSS software (version 18).

FINDINGS

There was no significant difference between the groups in enzyme activity of ALK-P of bone, PGE₂ and MMP3 variables. However, differences between the two groups in terms of activity of telopeptides C, Osteocalcin, and IGF1 were significant (P < 0.05). CLA has a potentially beneficial effect on bone markers in patients with rheumatoid arthritis. Therefore, in order to study the effect of CLA on bone health in patients with RA and all patients with autoimmune and bone diseases more studies with longer duration and evaluation of bone mass density are required.

Antilipidemic effects and gene expression profiling of the glycosaminoglycans from cricket in rats on a high fat diet

Glycosaminoglycan (GAG) from cricket (Gryllus bimaculatus) was studied as a potential health supplement. Antiatherosclerotic and antilipidemic effects of the GAG of G. bimaculatus (GbG, 5 or 10 mg/kg) were investigated in 15-week old Wistar rats treated with GbG for over a month. GbG produced a meaningful anti-edema effect with inhibition of C-reactive protein (CRP). Also, the weights of abdominal and epididymidal fat were also reduced in conjunction with a mild increase in body weight. Furthermore, the sero-biochemical parameters showed an antihyperlipidemic effect with decreased levels of phospholipid, AST, ALT, total cholesterol and glucose in a dose-dependent manner. In addition anticoagulant and antithrombotic effects were seen: platelet, thrombin time, prothrombin time and Factor I were increased with GbG treatment. Furthermore, the GbG treated rat group (at 10 mg/kg) compared to control, showed that 588 genes (test/control ratio >2.0) including lipocalin 2 (Lcn2) and alpha 2-macroglobulin (A2 m) were up-regulated, and 569 genes (test/control ratio >0.5) including stearoyl-coenzyme A desaturase 1 (Scd1) were down-regulated. Based on these results, GbG could potentially prevent or treat fatty liver or hyperlipidemia in rats on a high-fat diet.

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.

Unbound free fatty acids from preterm infants treated with intralipid decouples unbound from total bilirubin potentially making phototherapy ineffective

Extremely low birth weight (ELBW; <1,000 g) infants have poor outcomes, often compromised by bilirubin neurotoxicity. We measured unbound bilirubin (Bf) and unbound free fatty acid (FFAu) levels in 5 ELBW infants in a trial examining the effects of pharmacologic ductal closure on infants treated with Intralipid infusion (3 g/kg/day). The levels for all infants (mean ± SD) were: total serum bilirubin (TSB) 4.6 ± 1.7 mg/dl, FFAu 376 ± 496 nM, and Bf 42 ± 30 nM. Of the 3 infants who died, 2 had TSB <5.9 mg/dl but FFAu >580 nM and Bf >75 nM. Multiple regression revealed a major effect on Bf levels due to FFAu, indicating that Intralipid elevated levels of FFAu and Bf. Indomethacin or ibuprofen reduced Bf levels, most likely by reducing FFAu levels through lipase inhibition. Because displacement of Bf by FFAu decouples Bf from TSB, phototherapy may not reduce the risk of bilirubin or FFAu toxicity in Intralipid-treated ELBW infants.

Lipid peroxidation of poly-unsaturated fatty acids in normal and obese adipose tissues

Adipose tissues function as the primary storage compartment of fatty acids and as an endocrine organ that affects peripheral tissues. Many of adipose tissue-derived factors, often termed adipokines, have been discovered in recent years. The synthesis and secretion of these factors vary in different depots of adipose tissues. Excessive lipid accumulation in adipocytes induces inflammatory processes by up-regulating the expression and release of pro-inflammatory cytokines. In addition, activated macrophages in the obese adipose tissue release inflammatory cytokines. Adipose tissue inflammation has also been linked to an enhanced metabolism of polyunsaturated fatty acids (PUFAs). The non-enzymatic peroxidation of PUFAs and of their 12/15-lipoxygenase-derived hydroperoxy metabolites leads to the generation of the reactive aldehyde species 4-hydroxyalkenals. This review shows that 4-hydroxyalkenals, in particular 4-hydroxynonenal, play a key role in lipid storage homeostasis in normal adipocytes. Nonetheless, in the obese adipose tissue an increased production of 4-hydroxyalkenals contributes to the inflamed phenotype.

Interaction between dietary conjugated linoleic acid and calcium supplementation affecting bone and fat mass

Dietary conjugated linoleic acid (CLA) has shown wide biologically beneficial effects, such as anticancer, antiatherosclerotic, antidiabetic, immunomodulating, and antiobesity effects. However, the effects of CLA on total body ash, reflective of bone mineral content, have not been consistent. We hypothesized that the inconsistency of the CLA effect on ash may be linked to interaction between CLA and dietary calcium levels. Thus, we investigated the effects of CLA on body ash in conjunction with various calcium levels. Male ICR mice were fed three different levels of calcium (0.01, 0.5, and 1%) with or without 0.5% CLA for 4 weeks for Experiment 1 and separate CLA isomers at 0.22% level with 1% calcium in Experiment 2. CLA feeding reduced body fat regardless of dietary calcium level, whereas CLA supplementation increased body ash compared to control only in animals fed the 1% calcium. In Experiment 2 it was confirmed that this observation was associated with the trans-10, cis-12 CLA isomer, but not with the cis-9, trans-11 isomer. CLA administration with 1% dietary calcium significantly improved total ash percent (%) in femurs, confirming that CLA has the potential to be used to improve bone mass.

Evaluation of the Antiobesity Effects of an Amino Acid Mixture and Conjugated Linoleic Acid on Exercising Healthy Overweight Humans: A Randomized, Double-blind, Placebo-controlled Trial

This single-centre, randomized, double-blind, placebo-controlled trial investigated the effects of administering a mixture of four amino acids (lysine, proline, alanine and arginine) with or without conjugated linoleic acid to healthy overweight humans before and after exercising. Forty-one healthy subjects (body mass index ≥ 23 to < 30 kg/m2) completed the study following randomization to receive either placebo or one of three test supplements: amino acid mixture 0.76 g/day; amino acid mixture 1.52 g/day; or amino acid mixture 1.52 g/day coadministered with conjugated linoleic acid 1.6 g/day. Each of the study treatments was administered 30 min before and immediately after a period of daily exercise, which was delivered by an exercise expert, for a period of 12 weeks. When compared with the placebo group, several indicators, such as waist and hip circumferences, were found to have significantly decreased in the test supplement groups compared with the placebo. These results suggest that ingestion of these supplements might enhance the fat-burning effects of exercise.

Effect of conjugated linoleic acid supplementation on lipoprotein lipase activity in 3T3-L1 adipocyte culture

Supplementation with conjugated linoleic acid may reduce fat body mass and increase lean body mass in various species. Some studies have demonstrated that conjugated linoleic acid reduces body fat, in part, by inhibiting the activity of lipoprotein lipase in adipocytes. The objective of this work was to study the effect of conjugated linoleic acid supplementation on lipoprotein lipase activity in 3T3-L1 adipocyte culture. 3T3-L1 adipocytes received linoleic acid (group C) or conjugated linoleic acid (group AE, supplemented with AdvantEdge® CLA, and group CO, supplemented with CLA One®) in concentrations of 1 mmol/L. Heparin-releasable lipoprotein lipase activity was analyzed by means of a 3T3-L1 adipocyte culture. After 7 days, heparin-releasable lipoprotein lipase activity was lower in the groups AE and CO supplemented with conjugated linoleic acid. These results suggest that one of the mechanisms by which CLA is capable of reducing body fat is by reducing lipoprotein lipase activity.

Conjugated linoleic acid-induced fat loss dependence on Delta6-desaturase or cyclooxygenase

OBJECTIVE

To determine whether conjugated linoleic acid (CLA)-induced body fat loss is dependent upon metabolism of CLA by Delta6-desaturase, cyclooxygenase, or lipoxygenase.

METHODS AND PROCEDURES

Mice were fed diets with or without CLA and inhibitors to either Delta6-desaturase (SC-26196), cyclooxygenase (aspirin), or lipoxygenase (nordihydroguaiaretic acid (NDGA)) for 2 weeks. Body fat percent, lean mass, fat pad weights, liver weight, and fatty acid concentrations were determined. A Delta6-desaturase index was calculated, and adipose tissue prostaglandin E(2) (PGE(2)) and leukotriene B(4) (LTB(4)) concentrations were determined to confirm enzyme inhibition.

RESULTS

Inhibition of Delta6-desaturase and cyclooxygenase were confirmed. CLA caused a loss of body fat (P < 0.001). The body fat loss was blocked (P = 0.08) by the Delta6-desaturase inhibitor at a dose that decreased (P < 0.05) the calculated index. Aspirin and NDGA had no effect on body fat and did not interact with CLA.

DISCUSSION

Inhibition of Delta6-desaturase prevented CLA from being able to cause a body fat loss. Therefore, a desaturated metabolite of CLA appears to be involved in the CLA antiobesity effect. This effect of CLA does not seem dependent upon cyclooxygenase. Because lipoxygenase activity was not blocked by NDGA, we cannot draw conclusions about its importance in mediating the antiobesity effect of CLA.

Nordihydroguaiaretic acid and aspirin increase lifespan of genetically heterogeneous male mice

The National Institute on Aging's Interventions Testing Program was established to evaluate agents that are purported to increase lifespan and delay the appearance of age-related disease in genetically heterogeneous mice. Up to five compounds are added to the study each year and each compound is tested at three test sites (The Jackson Laboratory, University of Michigan, and University of Texas Health Science Center at San Antonio). Mice in the first cohort were exposed to one of four agents: aspirin, nitroflurbiprofen, 4-OH-alpha-phenyl-N-tert-butyl nitrone, or nordihydroguaiaretic acid (NDGA). Sample size was sufficient to detect a 10% difference in lifespan in either sex,with 80% power, using data from two of the three sites. Pooling data from all three sites, a log-rank test showed that both NDGA (p=0.0006) and aspirin (p=0.01) led to increased lifespan of male mice. Comparison of the proportion of live mice at the age of 90% mortality was used as a surrogate for measurement of maximum lifespan;neither NDGA (p=0.12) nor aspirin (p=0.16) had a significant effect in this test. Measures of blood levels of NDGA or aspirin and its salicylic acid metabolite suggest that the observed lack of effects of NDGA or aspirin on life span in females could be related to gender differences in drug disposition or metabolism. Further studies are warranted to find whether NDGA or aspirin, over a range of doses,might prove to postpone death and various age-related outcomes reproducibly in mice.

Effect of conjugated linoleic acid on bone formation and rheumatoid arthritis

Conjugated linoleic acid (CLA) has shown a variety of biologically beneficial effects. Dietary CLA inhibits eddosteal bone resorption, increases endocortical bone formation, and modulates the action and expression of cyclooxygenase (COX) enzyme, thereby decreasing prostaglandin-dependent bone resorption. CLA also enhances calcium absorption and may improve bone formation in animals, although results are not consistent. Since CLA can also affect inflammatory cytokines, it is hypothesized that CLA may be a good tool for prevention or reduction of rheumatoid arthritis symptoms. The possible mechanisms by which CLA prevents rheumatoid arthritis as well as other inflammatory diseases is discussed.

Six months supplementation with conjugated linoleic acid induces regional-specific fat mass decreases in overweight and obese

Long-term supplementation with conjugated linoleic acid (CLA) reduces body fat mass (BFM) and increases or maintains lean body mass (LBM). However, the regional effect of CLA was not studied. The study aimed to evaluate the effect of CLA per region and safety in healthy, overweight and obese adults. A total of 118 subjects (BMI: 28-32 kg/m2) were included in a double blind, placebo-controlled trial. Subjects were randomised into two groups supplemented with either 3 x 4 g/d CLA or placebo for 6 months. CLA significantly decreased BFM at month 3 (Delta=- 0 x 9 %, P=0 x 016) and at month 6 (Delta=- 3 x 4 %, P=0 x 043) compared with placebo. The reduction in fat mass was located mostly in the legs (Delta=- 0 x 8 kg, P<0 x 001), and in women (Delta=-1 x 3 kg, P=0 x 046) with BMI >30 kg/m2 (Delta=-1 x 9 kg, P=0 x 011), compared with placebo. The waist-hip ratio decreased significantly (P=0 x 043) compared with placebo. LBM increased (Delta=+0 x 5 kg, P=0 x 049) within the CLA group. Bone mineral content was not affected (P=0 x 70). All changes were independent of diet and physical exercise. Safety parameters including blood lipids, inflammatory and diabetogenic markers remained within the normal range. Adverse events did not differ between the groups. It is concluded that supplementation with CLA in healthy, overweight and obese adults decreases BFM in specific regions and is well tolerated.

Conjugated linoleic acid and its effects on animal products and health in single-stomached animals

Conjugated linoleic acids (CLA) have been shown to have anti-carcinogenic, anti-obesity, anti-atherogenic and immunomodulatory functions. The basis for these effects has not been fully explained, but probably involves effects of CLA on eicosanoid metabolism, cytokine production and\or gene expression. The predominant isomer (85–90%) in the natural sources of CLA has thecis-9, trans-11 configuration. As interest in CLA grew and synthetic forms became available, the number of studies examining the effects of dietary CLA in rodents, human subjects and livestock has increased greatly. In the late 1990 s the observation that CLA had anti-obesity effects was reported. Subsequently, it was determined that this effect in mice could be attributed to thetrans-10, cw-12 isomer that, along with thecis-9,trans-11 isomer, predominates in the synthetic forms of CLA. The santi-obesity response varies in magnitude depending on species, and has not been consistent in non-rodents. In general, the response is greatest in mice and less or absent in other species. The basis for this lack of consistency is not clear and is unlikely to be accounted for by differences in the source of CLA. In the pig variation in body fat of animals may account for differences in responsiveness. There is no direct evidence of an anti-carcinogenic effect of CLA in human subjects or livestock. Indirect evidence fromin vitrostudies with cell lines, as well as epidemiological studies, suggest that CLA may be relevant as a natural anti-carcinogen. The immunomodulatory effects of CLA may have application in livestock production as an alternative to the use of feed antibiotics, or as a means of improving the response to vaccination and conferring disease resistance. The recent literature on the effects of CLA, with emphasis on its anti-obesity effects, is reviewed.

The body fat-lowering effect of conjugated linoleic acid: a comparison between animal and human studies

Different reasons which justify differences between rodents and humans in body fat reduction produced by conjugated linoleic acid (CLA) could be proposed. The doses used in humans are lower than those used in rodents. Human experiments have been performed with CLA isomer mixtures instead of isolated isomers. The variable dilution of t-10, c-12, the active isomer, among different preparations might explain the reduced responsiveness in humans. Diet composition may modulate CLA effects on body fat accumulation. As far as human studies are concerned, a specific dietary pattern has not been established. As a result differences among studies and also among subjects in the same study are likely. In rodents, the effects of CLA vary with genotype, suggesting that genetic predisposition to fat accumulation can play an important role in the effectiveness of CLA. Human volunteers with different body mass index have participated in the published studies and even in the same experiment. So, differences in lipid metabolism among subjects could help to explain the discrepancies observed in the literature. Age and maturity may also be crucial. Experiments using rodents have been conducted with growing animals and there is little evidence of CLA effectiveness in adult animals. By contrast, human studies have been performed with adults. Inhibition of lipogenesis in white adipose tissue is one of the mechanisms which have been proposed to explain the body-fat lowering effect of CLA, but lipogenesis in this tissue is very low in humans. Another mechanism suggested is increased fatty acid oxidation in the liver associated with peroxisome proliferation, but humans are relatively insensitive to this effect.

Esculetin induces apoptosis and inhibits adipogenesis in 3T3-L1 cells

OBJECTIVE

To determine the effects of esculetin, a plant phenolic compound with apoptotic activity in cancer cells, on 3T3-L1 adipocyte apoptosis and adipogenesis.

RESEARCH METHODS AND PROCEDURES

3T3-L1 pre-confluent preadipocytes and lipid-filled adipocytes were incubated with esculetin (0 to 800 microM) for up to 48 hours. Viability was determined using the Cell Titer 96 Aqueous One Solution cell proliferation assay; apoptosis was quantified by measurement of single-stranded DNA. Post-confluent preadipocytes were incubated with esculetin for up to 6 days during maturation. Adipogenesis was quantified by measuring lipid content using Nile Red dye; cells were also stained with Oil Red O for visual confirmation of effects on lipid accumulation.

RESULTS

In mature adipocytes, esculetin caused a time- and dose-related increase in adipocyte apoptosis and a decrease in viability. Apoptosis was increased after only 6 hours by 400 and 800 microM esculetin (p < 0.05), and after 48 hours, as little as 50 microM esculetin increased apoptosis (p < 0.05). In preadipocytes, apoptosis was detectable only after 48 hours (p < 0.05) with 200 microM esculetin and higher concentrations. However, results of the cell viability assay indicated a reduction in preadipocyte number in a time- and dose-related manner, beginning as early as 6 hours with 400 and 800 microM esculetin (p < 0.05). Esculetin also inhibited adipogenesis of 3T3-L1 preadipocytes. Esculetin-mediated inhibition of adipocyte differentiation occurred during the early, intermediate, and late stages of the differentiation process. In addition, esculetin induced apoptosis during the late stage of differentiation.

DISCUSSION

These findings suggest that esculetin can alter fat cell number by direct effects on cell viability, adipogenesis, and apoptosis in 3T3-L1 cells.

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.

Beef tallow increases the potency of conjugated linoleic acid in the reduction of mouse mammary tumor metastasis

Animal studies consistently show that dietary conjugated linoleic acid (CLA) reduces mammary tumorigenesis including metastasis. Relatively low concentrations of CLA are required for those effects, and a threshold level exists above which there is no added reduction. We reasoned that the concentration of CLA required to effectively alter mammary tumor metastasis may be dependent on the type of dietary fat because select fatty acids can enhance or suppress normal or malignant cell growth and metastasis. For this study, the diets (a total of 12 different groups) differed in fatty acid composition but not in energy from fat (40%). In experiments involving spontaneous metastasis, mice were fed for 11 wk; in experiments in which mice were injected i.v. with tumor cells, they were fed for 7 wk. Mice were then assessed for the effect of CLA concentration on mammary tumorigenesis. Mammary tumor growth was not altered, but metastasis was significantly decreased when beef tallow (BT) replaced half of a defined vegetable fat blend (VFB). That blend reflects the typical fat content of a Western diet. In addition, that same VFB:BT diet lowered the concentration of CLA required to significantly decrease mammary tumor metastasis from 0.1% of the diet to 0.05%. A diet in which corn oil replaced half of the VFB did not lower the threshold from 0.1 to 0.05%. In vitro, the main fatty acid in vegetable oil, linoleic acid, reduced the efficacy of CLA toxicity on mammary tumor cells in culture. Alternatively, fatty acids normally found in BT, such as oleic, stearic, and palmitic acids, either did not change or enhanced the cytolytic effects of CLA isomers on mouse mammary tumor cells in culture. These data provide evidence that dietary BT, itself with negligible levels of CLA, may increase the efficacy of dietary CLA in reducing mammary tumorigenesis.

Ácido linoléico conjugado e perda de peso

O tratamento e a prevenção da obesidade têm sido considerados uma enorme batalha para os profissionais da área de saúde. As indústrias de alimentos e de fármacos, por sua vez, têm oferecido cada vez mais uma vasta gama de novos produtos que preconizam a perda de peso. O ácido linoléico conjugado, encontrado em maiores concentrações na gordura de animais ruminantes, parece apresentar efeitos favoráveis quanto à manutenção do peso corporal. Esta revisão apresenta uma análise crítica dos dados disponíveis na literatura, que relacionam o ácido linoléico conjugado com o metabolismo energético e a composição corporal. Os estudos realizados com humanos ainda não são conclusivos, embora alguns apontem um possível aumento da lipólise e/ou redução da lipogênese, que reflete em alterações apenas na composição corporal, especialmente no tecido adiposo abdominal, mas não na perda de peso. Entretanto, as altas doses usadas nesses estudos podem implicar efeitos colaterais indesejáveis. Portanto, mais estudos são necessários para uma indicação desse ácido graxo como um agente para a melhora da composição corporal e/ou como um agente anti-obesidade.

Conjugated linoleic acid reduction of murine mammary tumor cell growth through 5-hydroxyeicosatetraenoic acid

Conjugated linoleic acid (CLA) is a dietary fatty acid that has been shown to reduce tumorigenesis and metastasis in breast, prostate and colon cancer in animals. However, the mechanism of its action has not been clarified. The goal of this study was to determine whether CLA altered mouse mammary tumor cell growth and whether specific metabolites of the lipoxygenase pathway were involved in CLA action. Both t10, c12-CLA and a lipoxygenase inhibitor, but not c9, t11-CLA or linoleic acid (LA), reduced mouse mammary tumor cell viability and growth by inducing apoptosis and reducing cell proliferation. t10, c12-CLA reduced the production of the 5-lipoxygenase metabolite, 5-hydroxyeicosatetraenoic acid (5-HETE). That effect was not seen with c9, t11-CLA or LA. Adding 5-HETE back to tumor cells reduced the t10, c12-CLA effect on both apoptosis and cell proliferation. These data suggest that t10, c12-CLA reduction of tumor cell growth may involve the suppression of the 5-lipoxygenase metabolite, 5-HETE, with subsequent effects on apoptosis and cell proliferation.

Structure–activity relationship of conjugated linoleic acid and its cognates in inhibiting heparin-releasable lipoprotein lipase and glycerol release from fully differentiated 3T3-L1 adipocytes

Conjugated linoleic acid (CLA) reduces body fat in part by inhibiting the activity of heparin-releasable lipoprotein lipase (HR-LPL) activity in adipocytes, an effect that is induced by the trans-10,cis-12 CLA isomer. In this study we used a series of compounds that are structurally related to CLA (i.e., CLA cognates) to investigate the structural basis for this phenomenon. None of the 18:1 CLA cognates that were tested, nor trans-9,cis-12 18:2, cis-12-octadecen-10-ynoic acid (10y,cis-12) or 11-(2'-(n-pentyl)phenyl)-10-undecylenic acid (designated P-t10), exhibited any significant effect on HR-LPL activity. Among the CLA derivatives (alcohol, amide, and chloride) that were tested, only the alcohol form inhibited HR-LPL activity, although to a lesser extent than CLA itself. In addition, intracellular TG was reduced only by trans-10,cis-12 CLA and the alcohol form of CLA. Hence it appears that the trans-10,cis-12 conjugated double bond in conjunction with a carboxyl group at C-1 is required for inhibition of HR-LPL activity, and that an alcohol group can partially substitute for the carboxyl group. We also studied glycerol release from the cells, observing that this was enhanced by trans-10 18:1, trans-13 18:1, cis-12 18:1, cis-13 18:1, P-t10 but was reduced by cis-9 18:1, the alcohol and amide forms of CLA or 10y,cis-12. Accordingly the structural feature or features involved in regulating lipolysis appear to be more complex. Despite enhancing lipolysis in cultured 3T3-L1 adipocytes, trans-10 18:1 did not reduce body fat gain when fed to mice.

Conjugated linoleic acid and obesity control: efficacy and mechanisms

Obesity is associated with high blood cholesterol and high risk for developing diabetes and cardiovascular disease. Therefore, management of body weight and obesity are increasingly considered as an important approach to maintaining healthy cholesterol profiles and reducing cardiovascular risk. The present review addresses the effects of conjugated linoleic acid (CLA) on fat deposition, body weight and composition, safety, as well as mechanisms involved in animals and humans. Animal studies have shown promising effects of CLA on body weight and fat deposition. The majority of the animal studies have been conducted using CLA mixtures that contained approximately equal amounts of trans-10, cis-12 (t10c12) and cis-9, trans-11 (c9t11) isomers. Results of a few studies in mice fed CLA mixtures with different ratios of c9t11 and t10c12 isomers have indicated that the t10c12 isomer CLA may be the active form of CLA affecting weight gain and fat deposition. Inductions of leptin reduction and insulin resistance are the adverse effects of CLA observed in only mice. In pigs, the effects of CLA on weight gain and fat deposition are inconsistent, and no adverse effects of CLA have been reported. A number of human studies suggest that CLA supplementation has no effect on body weight and insulin sensitivity. Although it is suggested that the t10c12 CLA is the antiadipogenic isomer of CLA in humans, the effects of CLA on fat deposition are marginal and more equivocal as compared to results observed in animal studies. Mechanisms through which CLA reduces body weight and fat deposition remain to be fully understood. Proposed antiobesity mechanisms of CLA include decreased energy/food intake and increased energy expenditure, decreased preadipocyte differentiation and proliferation, decreased lipogenesis, and increased lipolysis and fat oxidation. In summary, CLA reduces weight gain and fat deposition in rodents, while produces less significant and inconsistent effects on body weight and composition in pigs and humans. New studies are required to examine isomer-specific effects and mechanisms of CLA in animals and humans using purified individual CLA isomers.

Dietary conjugated linoleic acid and body composition

Conjugated linoleic acid (CLA) is a group of positional and geometric isomers of conjugated dienoic derivatives of linoleic acid. The major dietary source of CLA for humans is ruminant meats, such as beef and lamb, and dairy products, such as milk and cheese. The major isomer of CLA in natural food is cis-9,trans-11 (c9,t11). The commercial preparations contain approximately equal amounts of c9,t11 and trans-10,cis-12 (t10,c12) isomers. Studies have shown that CLA, specifically the t10,c12-isomer, can reduce fat tissue deposition and body lipid content but appears to induce insulin resistance and fatty liver and spleen in various animals. A few human studies suggest that CLA supplementation has no effect on body weight and could reduce body fat to a much lesser extent than in animals. To draw conclusions on this form of dietary supplementation and to ultimately make appropriate recommendations, further human studies are required. The postulated antiobesity mechanisms of CLA include decreased energy and food intakes, decreased lipogenesis, and increased energy expenditure, lipolysis, and fat oxidation. This review addresses recent studies of the effects of CLA on lipid metabolism, fat deposition, and body composition in both animals and humans as well as the mechanisms surrounding these effects.

Fatty acid composition of fats is an early determinant of childhood obesity: a short review and an opinion

The importance of dietary fat in human obesity remains a controversial issue as the prevalence of overweight and obesity has increased despite no dramatic change in the amount of ingested fats over the past few decades. However, qualitative changes (i.e. the fatty acid composition of fats) have been largely disregarded. In this review, we summarize experimental evidence which supports polyunsaturated fatty acids of the omega6 series as being potent promoters of both adipogenesis in vitro and adipose tissue development in vivo during the gestation/lactation period. This conclusion is also supported by epidemiological data from infant studies as well as by the assessment of the fatty acid composition of mature breast milk and formula milk. It is proposed that unnoticed changes in fatty acid composition of ingested fats over the last decades have been important determinants in the increasing prevalence of childhood overweight and obesity.

Short-term intake of conjugated linoleic acid inhibits lipoprotein lipase and glucose metabolism but does not enhance lipolysis in mouse adipose tissue

Feeding diets supplemented with t10c12 conjugated linoleic acid (CLA) to growing mice reduces body fat mass. The effects are evident after 1 wk and maximal by 3 wk and are accompanied by reductions in fat cell size. This may complicate direct comparisons with adipocytes from control mice. Accordingly, we investigated the early biochemical events that occur within adipocytes during the first week of CLA feeding, before changes in the size of adipocytes have occurred. Female ICR mice were fed a control diet or a diet supplemented with 0.5 g/100 g of CLA for 4 d, at which time there were no differences in body weight, fat mass or adipocyte size (except that CLA-fed mice had fewer adipocytes >90 micro m in diameter). Parametrial adipose tissue from the CLA-fed mice had significantly reduced heparin-releasable lipoprotein lipase (LPL) and intracellular LPL activities and significantly reduced glucose incorporation into CO(2), fatty acid and glycerol. There were no differences between adipose tissues from CLA-fed or control mice in the ratios of 16:0 to 16:1 and 18:0 to 18:1 fatty acids or in norepinephrine-stimulated lipolysis. Serum insulin levels in food-deprived mice, measured at 4 d and 7 wk, did not differ between groups nor did the concentration of free fatty acids in serum of food-deprived or fed mice measured at the same time points. In mice, CLA-induced inhibition of heparin-releasable LPL and glucose metabolism may be the most important early steps leading to subsequent body fat reduction. In addition, CLA does not appear to enhance lipolysis in mouse adipose tissue in vivo.

Inhibition of stearoyl-CoA desaturase activity by the cis-9,trans-11 isomer and the trans-10,cis-12 isomer of conjugated linoleic acid in MDA-MB-231 and MCF-7 human breast cancer cells

Conjugated linoleic acid (CLA) is a collective term for a group of positional and geometric conjugated dienoic isomers of linoleic acid. CLA has been shown to have strong inhibitory effects on mammary carcinogenesis both in vitro and in vivo. In this study, we investigated the regulation of human stearoyl-CoA desaturase (SCD, EC 1.14.99.5) expression by CLA in human breast cancer cell lines, MDA-MB-231 and MCF-7. Treatment of the cells with the cis-9,trans-11 and trans-10,cis-12 CLA isomers (45 microM) did not repress SCD mRNA in both MDA-MB-231 and MCF-7 cells. However, the cis-9,trans-11 and trans-10,cis-12 CLA isomers significantly decreased SCD protein levels and SCD activity in MDA-MB-231 cells. In MCF-7 cells, both isomers did not affect protein levels, but they inhibited SCD activity. These results suggest that in MDA-MB-231 cells the cis-9,trans-11 and trans-10,cis-12 CLA isomers regulate human SCD by reducing SCD protein levels, while in MCF-7 cells both isomers have a direct inhibitory effect on SCD enzyme activity.

trans-10,cis-12-Conjugated linoleic acid reduces leptin secretion from 3T3-L1 adipocytes

The trans10,cis12 (t10c12) isomer of conjugated linoleic acid (CLA) has been shown to inhibit heparin-releasable lipoprotein lipase activity, reduce lipid stores in cultured 3T3-L1 adipocytes, and, when fed to mice, reduce body fat gain. We now report that t10c12 CLA significantly reduced leptin secretion from cultured 3T3-L1 adipocytes, and reduced leptin mRNA levels within the cells. Similar effects were produced by conjugated nonadecadienoic acid (a 19-carbon CLA cognate that is more effective than CLA in reducing body fat gain in mice), the lipoxygenase inhibitor nordihydroguaiaretic acid (which is synergistic with CLA in reducing body fat gain in mice), and ciglitazone (TZD, a PPARgamma agonist). Feeding mice diet supplemented with 0.5% t10c12 CLA for 4 weeks significantly reduced body fat gain, serum leptin levels and adipocyte leptin mRNA expression, without affecting feed intake or body weight. These data provide new insights into apparent mechanistic similarities among t10c12 CLA, CNA, NDGA, and TZD.