Conjugated linoleic acid and bone biology

Production and characterization of anti-hypertensive and anti-diabetic peptides from fermented sheep milk with anti-inflammatory activity: in vitro and molecular docking studies

BACKGROUND

The present study aimed to evaluate the anti-hypertensive and anti-diabetic activities from biologically active peptides produced by fermented sheep milk with Lacticaseibacillus paracasei M11 (MG027695), as well as to purify and characterize the angiotensin-converting enzyme (ACE) inhibitory and anti-diabetic peptides produced from fermented sheep milk.

RESULTS

After 48 h of fermentation at 37 °C, sheep milk demonstrated significant changes in anti-diabetic effects and ACE-I effects, with inhibition percentages observed for ACE inhibition (76.32%), α-amylase (70.13%), α-glucosidase (70.11%) and lipase inhibition (68.22%). The highest level of peptides (9.77 mg mL-1) was produced by optimizing the growth conditions, which included an inoculation rate of 2.5% and a 48 h of incubation period. The comparison of molecular weight distributions among protein fractions was conducted through sodium dodecyl-sulfate polyacrylamide gel electrophoresis analysis, whereas spots were separated using 2D gel electrophoresis according to both the molecular weight and pH. Peptide characterization with ultra-filtration membranes at 3 and 10 kDa allowed the study to assess molecular weight-based separation. Nitric oxide generated by lipopolysaccharide and the secretion of pro-inflammatory cytokines in RAW 264.7 immune cells were both inhibited by sheep milk fermented with M11. Fourier-transform infrared spectroscopy was employed to assess changes in functional groups after fermentation, providing insights into the structural changes occurring during fermentation.

CONCLUSION

The present study demonstrates that fermentation with L. paracasei (M11) led to significant changes in fermented sheep milk, enhancing its bioactive properties, notably in terms of ACE inhibition and anti-diabetic activities, and the generation of peptides with bioactive properties has potential health benefits. © 2024 Society of Chemical Industry.

The Effect of Conjugated Linoleic Acid Supplementation on Densitometric Parameters in Overweight and Obese Women-A Randomised Controlled Trial

Background and Objectives: Conjugated linoleic acid (CLA) can improve bone health in animals, yet the effects on humans have not been consistent. Therefore, this parallel randomised controlled trial aimed to assess the effect of CLA supplementation on bone mineral density (BMD) and content (BMC) in overweight or obese women. Materials and Methods: The study population included 74 women who were divided into the CLA (n = 37) and control (n = 37) groups. The CLA group received six capsules per day containing approximately 3 g of cis-9, trans-11 and trans-10, cis-12 CLA isomers in a 50:50 ratio. The control group received the same number of placebo capsules that contained sunflower oil. BMC and BMD at total body, lumbar spine (L1-L4), and femoral neck were measured before and after a three-month intervention. Results: The comparison of BMC and BMD for the total body, lumbar spine (L1-L4), and femoral neck before and after the intervention showed no differences between the groups. However, a within-group analysis demonstrated a significant increase in BMC (p = 0.0100) and BMD (p = 0.0397) at lumbar spine (L1-L4) in the CLA group. Nevertheless, there were no significant differences between the CLA and placebo groups in changes in all analysed densitometric parameters. Conclusions: Altogether, three-month CLA supplementation in overweight and obese women did not improve bone health, although the short intervention period could have limited our findings, long-term intervention studies are needed. The study protocol was registered in the German Clinical Trials Register database (ID: DRKS00010462, date of registration: 4 May 2016).

Synovial tissue metabolomics analysis of the therapeutic effects of stir-fried Xanthii Fructus on rheumatoid arthritis in rats

Rheumatoid arthritis (RA) is a rheumatic disease that easily causes synovial hyperplasia and joint damage. Comprehensive metabolomic profiling of synovial tissue can reveal local pathological changes during RA and identify metabolites as candidate biomarkers. Detecting metabolites in synovial tissue can more directly reflect the pathological state and disease activity associated with it. stir-fried Xanthii Fructus has demonstrated efficacy in treating RA, but its pharmacodynamic property and mechanism of action are unclear. In this study, the molecular composition of the extract of stir-fried Xanthium Fructus was determined through HPLC. The major components that exert anti-inflammatory and analgesic effects were speculated to be phenolic acids. Next, the effect of stir-fried Xanthii Fructus extracts in RA treatment was comprehensively evaluated using rat body weight, foot volume, inflammatory factors, and histopathological sections of the ankle joint as evaluation indicators. The results showed that the extract of stir-fried Xanthii Fructus could significantly reduce the inflammatory response and improve the degree of joint swelling and the imbalance between pro-inflammatory and anti-inflammatory in adjuvant arthritis rats. Finally, non-targeted metabolomics based on UPLC-Q-TOF/MS and multivariate statistical analysis were used to explore the changes of endogenous metabolites in synovium tissues and to search for potential biomarkers and related metabolic pathways in stir-fried Xanthii Fructus extract-treated AA rats. The results showed that stir-fried Xanthii Fructus mainly treated RA by regulating energy metabolism, hormone metabolism, amino acid metabolism and oxidative stress response in adjuvant arthritis rats. This study provides a theoretical basis for the mechanism of action of stir-fried Xanthii Fructus extract in treating RA.

The System Research of the Molecular Mechanism of Quyushengxin Capsule in the Treatment of Osteonecrosis of the Femoral Head

Osteonecrosis of the femoral head (ONFH) is a chronic and irreversible disease that has a risk of eventually developing into a joint collapse and resulting in joint dysfunction. Quyushengxin capsule (QYSXC) is an effective and safe traditional Chinese medicine used in the treatment of ONFH. In this present study, an integrated approach was used to investigate the mechanism of QYSXC in the treatment of ONFH, which contained systems pharmacology, molecular docking, and chip experiment. In the systems pharmacology, target fishing, protein-protein interaction (PPI), Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis, and herbs-compounds-targets-pathways (H-C-T-P) network construction were performed to study the mechanism of QYSXC in the treatment of ONFH. The results showed that 15 key compounds, 8 key targets, and 8 key signaling pathways were found for QYSXC in the treatment with ONFH. Then, molecular docking was performed to further explore the interaction between some key compounds and key targets. After that, the chip experiment was performed to verify some target factors, including ICAM-1, IL-6, IL-1α, IL-1β, IL-2, IL-4, IL-10, and TNF-α. The results of this work may provide a theoretical basis for further research on the molecular mechanism of QYSXC in the treatment of ONFH.

Effects of Icariin on Modulating Gut Microbiota and Regulating Metabolite Alterations to Prevent Bone Loss in Ovariectomized Rat Model

Postmenopausal osteoporosis (PMOP) is an estrogen deficiency-induced bone loss, which has been shown an association with an altered gut microbiota (GM). Gut microbiota-bone axis has been recognized as a crucial mediator for bone homeostasis. Icariin (ICA) is an effective agent to delay bone loss by regulating the bone homeostasis. Thus, we hypothesize that ICA can prevent bone loss by modulating GM and regulating metabolite alterations. The effects of ICA on bone metabolism improvement in ovariectomized (OVX) rats and their relationships with the GM and fecal metabolites were investigated. Micro-computed tomography (micro-CT) and hematoxylin-eosin (HE) staining showed a typical bone boss in OVX group, while ICA or estradiol (E2) administration exhibited positive effects on bone micro-architecture improvement. The GM such as Actinobacteria, Gammaproteobacteria, Erysipelotrichi, Erysipelotrichales, Enterobacteriales, Actinomycetales, Ruminococcus and Oscillospira significantly correlated to serum bone Gla-protein (BGP), receptor activator of nuclear factor-κB (RANK), receptor activator of nuclear factor-κB ligand (RANKL), osteoprotegerin (OPG) and tartrate resistant acid phosphatase (TRACP). Further t-test revealed a substantial variation of the GM and fecal metabolites in different treatments. Among them, Lachnoclostridium, Butyricimonas, Rikenella, Paraprevolla, Adlercreutzia, Enterorhabdus, Anaerovorax, Allobaculum, Elusimicrobium, Lactococcus, Globicatella and Lactobacillus were probably the key microbial communities driving the change of bile acid, amino acid and fatty acid, thereby leading to an improvement of PMOP. The significant up-regulation of L-Saccharopine, 1-Aminocyclohexadieneacid and linoleic acid after ICA administration suggested important contributions of amino acid and fatty acid metabolisms in the prevention and treatment of PMOP. Taken together, our study has provided new perspectives to better understand the effects of ICA on PMOP improvement by regulating GM and the associated fecal metabolites. Our findings contribute to develop ICA as a potential therapy for PMOP.

Assessment of the anti-rheumatoid arthritis activity of Gastrodia elata (tian-ma) and Radix aconitic lateralis preparata (fu-zi) via network pharmacology and untargeted metabolomics analyses

AIM

Gastrodia elata and Radix aconiti lateralis preparrata are respectively named as Tian-Ma and Fu-Zi (TF) in Chinese. We explored the active components against rheumatoid arthritis (RA) from an extensively used couplet of Chinese herbs, Gastrodia elata and Radix aconiti lateralis preparata (TF) via untargeted metabolomics and network pharmacological approaches.

METHODS

Water extracts of TF were mixed at ratios 1:1, 3:2 and 2:3 (w/w). Ultra-performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS) was then utilized as metabolomics screening. Human Metabolome (http://www.hmdb.ca/) and Lipidmaps (http://www.lipidmaps.org/) databases were used to annotate detected compounds. Further identification of vital genes and important pathways associated with the anti-RA properties of the TF preparations was done via network pharmacology, and verified by real-time quantitative polymerase chain reaction (RT-qPCR).

RESULTS

Four key compounds involved in unsaturated fatty acid biosynthesis and isoflavonoid biosynthesis were identified through metabolomics analyses. Three key components of TF associated with anti-RA activity were linoleic acid, daidzein, and daidzin. Results of RT-qPCR revealed that all 3 tested TF couplets (1:1, 3:2, and 2:3) markedly suppressed the transcription of PTGS2. These results were consistent with our network pharmacological predictions.

CONCLUSIONS

The anti-RA properties of Tian-Ma and Fu-Zi are associated with the inhibition of arachidonic acid metabolism pathway.

Lipid-modifying effects of nutraceuticals: An evidence-based approach

The present review provides an up-to-date summary of the findings on the lipid-lowering effects of the most important nutraceuticals and functional foods. Based on current knowledge, nutraceuticals might exert significant lipid-lowering, and their use has several advantages: A number of important questions remain to be addressed, including whether longer durations of therapy would result in a better response and the exact safety profile of nutraceuticals, especially at doses higher than those consumed in an average diet. Additionally, data regarding the effects of nutraceutical supplementation on the incidence of cardiovascular outcomes are lacking, and it is not clear whether additional lipid lowering by nutraceuticals can modify the residual cardiovascular risk that remains after statin therapy.

Pros and cons of fatty acids in bone biology

Despite the growing interest in deciphering the causes and consequences of obesity-related disorders, the mechanisms linking fat intake to bone behaviour remain unclear. Since bone fractures are widely associated with increased morbidity and mortality, most notably in elderly and obese people, bone health has become a major social and economic issue. Consistently, public health system guidelines have encouraged low-fat diets in order to reduce associated complications. However, from a bone point of view, mechanisms linking fat intake to bone alteration remain quite controversial. Thus, after more than a decade of dedicated studies, this timely review offers a comprehensive overview of the relationships between bone and fatty acids. Using clinical evidences as a starting-point to more complex molecular elucidation, this work highlights the complexity of the system and reveals that bone alteration that cannot be solved simply by taking ω-3 pills. Fatty acid effects on bone metabolism can be both direct and indirect and require integrated investigations. Furthermore, even at the level of a single cell, one fatty acid is able to trigger several different independent pathways (receptors, metabolites…) which may all have a say in the final cellular metabolic response.

Osteoprotective effect of soybean and sesame oils in ovariectomized rats via estrogen-like mechanism

The purpose of the present study was to investigate the osteoprotective effects of soybean oil (SbO) and sesame oil (SO) in ovarictomized (OVX) rats. The results indicated that the OVX rats exhibited a significant decrease in Ca and P level in both serum and bone, the activities of the antioxidant enzymes SOD and CAT and the antioxidant biomarker GSH accompanied with a marked increase in the oxidative stress markers MDA and PC, the inflammatory indices (TNF-α, CRP levels, WBCs counts and ACP activity) in, both, bone and serum. Supplementating the diet of the OVX rats with SbO (15 % w/w) or SO (10 % w/w) for 2 months to resulted in modulation of the alterations in all tested parameters and succeeded to restore minerals, antioxidant enzymes, antioxidant biomarkers, oxidative stress markers, inflammatory indices, and WBCs counts. It could be concluded that the consumption of diets supplemented with SbO or SO might be useful for preventing bone loss caused by estrogen deficiency in ovariectomy status.

Conjugated linoleic Acid prevents ovariectomy-induced bone loss in mice by modulating both osteoclastogenesis and osteoblastogenesis

Postmenopausal osteoporosis due to estrogen deficiency is associated with severe morbidity and mortality. Beneficial effects of conjugated linoleic acid (CLA) on bone mineral density (BMD) have been reported in mice, rats and humans, but the effect of long term CLA supplementation against ovariectomy-induced bone loss in mice and the mechanisms underlying this effect have not been studied yet. Eight-week old ovariectomized (Ovx) and sham operated C57BL/6 mice were fed either a diet containing 0.5 % safflower oil (SFO) or 0.5 % CLA for 24 weeks to examine BMD, bone turn over markers and osteotropic factors. Bone marrow (BM) cells were cultured to determine the effect on inflammation, osteoclastogenesis, and osteoblastogenesis. SFO/Ovx mice had significantly lower femoral, tibial and lumbar BMD compared to SFO/Sham mice; whereas, no difference was found between CLA/Ovx and CLA/Sham mice. CLA inhibited bone resorption markers whereas enhanced bone formation markers in Ovx mice as compared to SFO-fed mice. Reverse transcriptase polymerase chain reaction and fluorescence activated cell sorting analyses of splenocytes revealed that CLA inhibited pro-osteoclastogenic receptor activator of NF-κB (RANKL) and stimulated decoy receptor of RANKL, osteoprotegerin expression. CLA also inhibited pro-inflammatory cytokine and enhanced anti-inflammatory cytokine production of lipopolysaccharide-stimulated splenocytes and BM cells. Furthermore, CLA inhibited osteoclast differentiation in BM and stimulated osteoblast differentiation in BM stromal cells as confirmed by tartrate resistant acid phosphatase and Alizarin Red staining, respectively. In conclusion, CLA may prevent postmenopausal bone loss not only by inhibiting excessive bone resorption due to estrogen deficiency but also by stimulating new bone formation. CLA might be a potential alternative therapy against osteoporotic bone loss.

Supplementation with fish oil and genistein, individually or in combination, protects bone against the adverse effects of methotrexate chemotherapy in rats

Cancer chemotherapy has been shown to induce long-term skeletal side effects such as osteoporosis and fractures; however, there are no preventative treatments. This study investigated the damaging effects of anti-metabolite methotrexate (MTX) subcutaneous injections (0.75 mg/kg BW) for five days and the potential protective benefits of daily oral gavage of fish oil at 0.5 mL/100 g BW (containing 375 mg of n-3 PUFA/100 g BW), genistein (2 mg/100 g BW), or their combination in young adult rats. MTX treatment alone significantly reduced primary spongiosa height and secondary spongiosa trabecular bone volume. Bone marrow stromal cells from the treated rats showed a significant reduction in osteogenic differentiation but an increase in adipogenesis ex vivo. Consistently, stromal cells had significantly higher mRNA levels of adipogenesis-related proliferator activator activated receptor-γ (PPAR-γ) and fatty acid binding protein (FABP4). MTX significantly increased the numbers of bone-resorbing osteoclasts and marrow osteoclast precursor cell pool while significantly enhancing the mRNA expression of receptor activator for nuclear factor kappa B ligand (RANKL), the RANKL/osteoprotegerin (OPG) ratio, interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in the bone. Supplementary treatment with fish oil and/or genistein significantly preserved trabecular bone volume and osteogenesis but suppressed MTX-induced adipogenesis and increases in osteoclast numbers and pro-osteoclastogenic cytokine expression. Thus, Fish oil and/or genistein supplementation during MTX treatment enabled not only preservation of osteogenic differentiation, osteoblast number and bone volume, but also prevention of MTX treatment-induced increases in bone marrow adiposity, osteoclastogenic cytokine expression and osteoclast formation, and thus bone loss.

Effects of dietary DHA and α-tocopherol on bone development, early mineralisation and oxidative stress in Sparus aurata (Linnaeus, 1758) larvae

DHA deficiency has been related to skeletal malformations in fish, but high DHA levels have produced controversial results that could relate to the oxidative status of fish tissues in the different reports. In the present study, gilthead seabream (Sparus aurata) larvae were fed deficient, adequate or high DHA levels, or high DHA levels supplemented with the antioxidant α-tocopherol. Larvae fed deficient DHA levels tended to be smaller, and showed the highest incidence of urinary bladder calculi, lordosis and kyphosis and the lowest number of mineralised vertebrae for any given size class. Elevation of dietary DHA increased larval growth and significantly enhanced the expression of the insulin-like growth factor 1 (IGF-1) gene. However, a DHA level increase up to 5 % raised the degree of lipid oxidation in larval tissues and deformities in cranial endochondral bones and in axial skeletal haemal and neural arches. The increase in dietary α-tocopherol supplementation in high-DHA feeds reduced again the occurrence of skeletal deformities. Moreover, the expression of genes coding for specific antioxidants such as catalase, superoxide dismutase or glutathione peroxidase, which neutralised reactive oxygen substances formed by increased dietary DHA, was significantly decreased in larvae fed high α-tocopherol levels. These results denoted the importance of DHA for early bone formation and mineralisation. Low dietary DHA levels delay early mineralisation and increase the risk of cranial and axial skeletal deformities. Excessive DHA levels, without an adequate balance of antioxidant nutrients, increase the production of free radicals damaging cartilaginous structures before bone formation.

Human health effects of conjugated linoleic acid from milk and supplements

The primary purpose of the present review was to determine if the scientific evidence available for potential human health benefits of conjugated linoleic acid (CLA) is sufficient to support health claims on foods based on milk naturally enriched with cis-9, trans-11-CLA (c9, t11-CLA). A search of the scientific literature was conducted and showed that almost all the promising research results that have emerged in relation to cancer, heart health, obesity, diabetes and bone health have been in animal models or in vitro. Most human intervention studies have utilised synthetic CLA supplements, usually a 50:50 blend of c9, t11-CLA and trans-10, cis-12-CLA (t10, c12-CLA). Of these studies, the only evidence that is broadly consistent is an effect on body fat and weight reduction. A previous review of the relevant studies found that 3.2 g CLA/d resulted in a modest body fat loss in human subjects of about 0.09 kg/week, but this effect was attributed to the t10, c12-CLA isomer. There is no evidence of a consistent benefit of c9, t11-CLA on any health conditions; and in fact both synthetic isomers, particularly t10, c12-CLA, have been suspected of having pro-diabetic effects in individuals who are already at risk of developing diabetes. Four published intervention studies using naturally enriched CLA products were identified; however, the results were inconclusive. This may be partly due to the differences in the concentration of CLA administered in animal and human studies. In conclusion, further substantiation of the scientific evidence relating to CLA and human health benefits are required before health claims can be confirmed.

t10c12-CLA maintains higher bone mineral density during aging by modulating osteoclastogenesis and bone marrow adiposity

Conjugated linoleic acid (CLA) has been shown to positively influence calcium and bone metabolism. Earlier, we showed that CLA (equal mixture of c9t11-CLA and t10c12-CLA) could protect age-associated bone loss by modulating inflammatory markers and osteoclastogenesis. Since, c9t11-CLA and t10c12-CLA isomers differentially regulate functional parameters and gene expression in different cell types, we examined the efficacy of individual CLA isomers against age-associated bone loss using 12 months old C57BL/6 female mice fed for 6 months with 10% corn oil (CO), 9.5% CO + 0.5% c9t11-CLA, 9.5% CO + 0.5% t10c12-CLA or 9.5% CO + 0.25% c9t11-CLA + 0.25% t10c12-CLA. Mice fed a t10c12-CLA diet maintained a significantly higher bone mineral density (BMD) in femoral, tibial and lumbar regions than those fed CO and c9t11-CLA diets as measured by dual-energy-X-ray absorptiometry (DXA). The increased BMD was accompanied by a decreased production of osteoclastogenic factors, that is, RANKL, TRAP5b, TNF-alpha and IL-6 in serum. Moreover, a significant reduction of high fat diet-induced bone marrow adiposity was observed in t10c12-CLA fed mice as compared to that of CO and c9t11-CLA fed mice, as measured by Oil-Red-O staining of bone marrow sections. In addition, a significant reduction of osteoclast differentiation and bone resorbing pit formation was observed in t10c12-CLA treated RAW 264.7 cell culture stimulated with RANKL as compared to that of c9t11-CLA and linoleic acid treated cultures. In conclusion, these findings suggest that t10c12-CLA is the most potent CLA isomer and it exerts its anti-osteoporotic effect by modulating osteoclastogenesis and bone marrow adiposity.

Effects of conjugated linoleic acid on cleavage of amyloid precursor protein via PPARγ

Conjugated linoleic acid (CLA) plays important roles in physiological conditions. The aim of present study was to explore the effects of CLA on the cleavage of amyloid precursor protein (APP) and the potential mechanism involved. The effects of CLA on intracellular APP, BACE1 (β-site APP Cleaving Enzyme1, BACE1), a disintegrin and metalloprotease (ADAM10) and extracellular sAPPα (soluble) were analyzed by RT-PCR, Western blot and ELISA in SH-SY5Y cells. Our study indicated that CLA significantly decreased the expression of BACE1 and increased the extracellular secretion of sAPPα, but not affected the levels of APP and ADAM10. The study also revealed that the nuclear receptor peroxisome proliferators activated receptor γ (PPARγ) played an important role in the CLA-induced intracellular BACE1 decrease, as well as the extracellular sAPPα increase through knockdown of PPARγ transcription using siRNA. We hypothesize that CLA acts as an agonist or ligand, which binds with PPARγ and leads to the increase in APP cleavage via α-secretase-mediated pathway and the decrease in the deposition of Aβ.

High-fat diets affect energy and bone metabolism in growing rats

BACKGROUND

High-fat diets are usually associated with greater weight (W) gain and body fat (BF). However, it is still unclear whether the type and amount of fat consumed influence BF. Additionally, dietary fat intake may also have consequences on skeletal health.

OBJECTIVE

To evaluate in healthy growing rats the effects of high-fat diets and type of dietary fat intake (saturated or vegetable oils) on energy and bone metabolism.

METHODS

At weaning, male Wistar rats (n = 50) were fed either a control diet (C; fat = 7% w/w) or a high-fat diet (20% w/w) containing either: soybean oil, corn oil (CO), linseed oil (LO), or beef tallow (BT) for 8 weeks. Zoometric parameters, BF, food intake and digestibility, and total and bone alkaline phosphatase (b-AP) were assessed. Total skeleton bone mineral density (BMD) and content (BMC), BMC/W, spine BMD, and bone volume (static-histomorphometry) were measured.

RESULTS

Animals fed BT diet achieved lower W versus C. Rats fed high-fat vegetable oil diets showed similar effects on the zoometric parameters but differed in BF. BT showed the lowest lipid digestibility and BMC. In contrast, high vegetable oil diets produced no significant differences in BMC, BMC/W, BMD, spine BMD, and bone volume. Marked differences were observed for LO and BT groups in b-AP and CO and BT groups in bone volume.

CONCLUSION

BT diet rich in saturated fatty acids had decreased digestibility and adversely affected energy and bone metabolisms, in growing healthy male rats. There were no changes in zoometric and bone parameters among rats fed high vegetable oil diets.

The effect of polyunsaturated fatty acids on bone health

The essential polyunsaturated fatty acids (PUFAs) are divided into two classes, n-3 (ω-3) and n-6 (ω-6) and their dietary precursors are α-linolenic (ALA) and linoleic acid (LA), respectively. PUFAs are precursors of a wide range of metabolites, for example eicosanoids like prostaglandins and leukotrienes, which play critical roles in the regulation of a variety of biological processes, including bone metabolism.

A large body of evidence supports an effect of PUFA on bone metabolism which may be mediated by regulation of osteoblastogenesis and osteoclast activity, change of membrane function, decrease in inflammatory cytokines, such as interleukin-1 (IL-1), interleukin-6 (IL-6), and tumour necrosis factor alpha (TNF-α), modulation of peroxisome proliferators-activated receptor γ (PPARγ) and influence in NO secretion and NO synthase.

Animal studies have shown that a higher dietary omega-3/omega-6 fatty acids ratio is associated with beneficial effects on bone health. Human studies conducted in elderly subjects suggest that omega-3 instead of omega-6 has a positive effect on bone metabolism. In spite of increasing evidence, studies conducted in humans do not allow us to draw a definitive conclusion on the usefulness of PUFAs in clinical practice.

Trans-10, cis-12-conjugated linoleic acid modulates NF-κB activation and TNF-α production in porcine peripheral blood mononuclear cells via a PPARγ-dependent pathway

The activation of PPARγ by ligands, including conjugated linoleic acid (CLA) isomers, plays an important role in the immune response. Among CLA isomers, trans-10, cis-12 (t10c12)-CLA is known to participate in the modulation of pro-inflammatory cytokine secretion. The aim of the present study was to assess the effect of t10c12-CLA on PPARγ activation, NF-κB activation and TNF-α expression in lipopolysaccharide (LPS)-naive and LPS-stimulated porcine peripheral blood mononuclear cells (PBMC). In addition, the effect of PPARγ inhibition on NF-κB activation and TNF-α expression in porcine PBMC was examined. t10c12-CLA was found to increase TNF-α expression and NF-κB activity in LPS-naive porcine PBMC. In contrast, t10c12-CLA decreased TNF-α expression and NF-κB activity in LPS-stimulated porcine PBMC. t10c12-CLA up-regulated PPARγ activity and mRNA expression in both LPS-naive and LPS-stimulated porcine PBMC. GW9662, a PPARγ antagonist, completely negated the modulating effects of t10c12-CLA on TNF-α expression and NF-κB activity in both LPS-naive and LPS-stimulated porcine PBMC. These results suggest that t10c12-CLA can modulate TNF-α production and NF-κB activation by a PPARγ-dependent pathway in porcine PBMC.

Cell nanomechanics and focal adhesions are regulated by retinol and conjugated linoleic acid in a dose-dependent manner

Retinol and conjugated linoleic acid (CLA) have previously been shown to have an important role in gene expression and various cellular processes, including differentiation, proliferation and cell death. In this study we have investigated the effect of retinol and CLA, both individually and in combination, on the intracellular cytoskeleton, focal adhesions (FAs) and the nanomechanical properties of 3T3 fibroblasts. We observed a dose-dependent decrease in the formation of FAs following treatment with either compound, which was directly correlated to an increase in cell height (>30%) and a decrease in the measured Young's modulus (approximately 28%). Furthermore, treatments with both compounds demonstrated an increased effect and led to a reduction of >70% in the average number of FAs per cell and a decrease of >50% in average cell stiffness. These data reveal that retinol and CLA disrupt FA formation, leading to an increase in cell height and a significant decrease in stiffness. These results may broaden our understanding of the interplay between cell nanomechanics and cellular contact with the external microenvironment, and help to shed light on the important role of retinoids and CLA in health and disease.

Conjugated linoleic acid prevents growth attenuation induced by corticosteroid administration and increases bone mineral content in young rats

Corticosteroids are a common therapy in many disease states, despite frequent and potentially serious side effects. Nutritional supplementation with conjugated linoleic acid (CLA) has been shown to increase fat-free mass, whereas supplementation with n-3 and n-6 fatty acids has been shown to increase bone mineral density (BMD). To determine whether CLA can attenuate the side effects of 8 weeks of corticosteroid administration, we randomized twenty-four 5-week-old male Sprague-Dawley rats into 1 of 4 groups: control; control + methylprednisolone (7 mg.kg-1.week-1); CLA diet (1% CLA w/w); or CLA plus methylprednisolone. Body composition, bone mineral content (BMC), and BMD were assessed with dual-energy X-ray absorptiometry at the onset and at the end of the 8-week intervention. The mechanical properties of bone were determined using 3-point femur bending at the end of the intervention. Methylprednisolone resulted in an attenuation of the increase in body mass and lean mass over the 8 weeks (p < 0.05). CLA prevented the methylprednisolone-induced attenuation of body mass and lean mass accumulation. CLA also resulted in a greater increase in BMC (p < 0.05) in the lumbar spine. The energy at failure of the isolated femurs was increased with CLA (p < 0.05). Dietary CLA prevents many of the growth- and bone-related side effects arising from 8 weeks of corticosteroid administration, results in greater increases in BMC and BMD, and can contribute to an improvement in some of the mechanical properties of bone.

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.

The potential benefits of creatine and conjugated linoleic acid as adjuncts to resistance training in older adults

Human aging is associated with a significant reduction in muscle mass (sarcopenia) resulting in muscle weakness and functional limitations in the elderly. Sarcopenia has been associated with mitochondrial dysfunction and the accumulation of mtDNA deletions. Resistance training increases muscle strength and size and can increase mitochondrial capacity and decrease oxidative stress in older adults. Creatine monohydrate (CrM) and conjugated linoleic acid (CLA) have biological effects that could enhance some of the beneficial effects of resistance training in older adults (i.e., up arrow fat-free mass, down arrow total body fat). We have completed two resistance-training studies with CrM alone and CrM+CLA supplementation in older adults to evaluate the independent effects of exercise and dietary supplements, as well as their interactive effects. Our studies, and several others, have found that CrM enhanced the resistance exercise mediated gains in fat-free mass and strength. More recently, we found that the addition of CLA also lead to a significant reduction of body fat after six months of resistance training in older adults. Older adults have fewer wild-type mtDNA copies and higher amounts of mtDNA deletions as compared with younger adults in mature skeletal muscle; however, these deletions are not seen in the satellite cell-derived myoblast cultures. These findings, and the fact that mtDNA deletions are lower and wild-type mtDNA copy number is higher after resistance training in older adults, suggests that activation of satellite cells secondary to resistance exercise-induced muscle damage can dilute or "shift" the proportion of mtDNA genotype towards that of a younger adult. Recent evidence suggests that CrM supplementation in combination with strength training can enhance satellite cell activation and total myonuclei number per muscle fiber in young men. Future studies are required to determine whether the mitochondrial adaptations to resistance exercise in older adults are further enhanced with CrM supplementation and whether this is due to increased recruitment of satellite cells. It will also be important to determine whether these changes are maintained over a longer time period.

The impact of nutritional and exercise strategies for aging bone and muscle

This symposium addressed recent evidence suggesting that nutritional intervention and resistance-training strategies may be important for aging bone and muscle. The physiological consequences of aging and the potential mechanistic actions of nutritional aids during resistance training were emphasized.

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.

Conjugated linoleic acid protects against age-associated bone loss in C57BL/6 female mice

Osteoporosis is one of the major causes of morbidity in the elderly. Inflammation exerts a significant influence on bone turnover, inducing the chronic form of osteoporosis. Dietary nutrition has the capacity to modulate inflammatory response. Therefore, nutritional strategies and lifestyle changes may prevent age-related osteoporosis, thereby improving the quality of life of the elderly population. Conjugated linoleic acid (CLA) has been shown to positively influence calcium and bone metabolism. Hence, this study was undertaken to examine the effect of CLA on bone mineral density (BMD) in middle-aged C57BL/6 female mice. After 10 weeks on diet, CLA-fed mice (14 months) maintained a higher BMD in different bone regions than corn oil (CO)-fed mice. The increased BMD was accompanied by a decreased activity of proinflammatory cytokines (such as tumor necrosis factor alpha, interleukin-6 and the receptor activator of NF-kappaB ligand) and decreased osteoclast function. Furthermore, a significant decrease in fat mass and an increase in muscle mass were also observed in CLA-fed mice compared to CO-fed mice. In conclusion, these findings suggest that CLA may prevent the loss of bone and muscle mass by modulating markers of inflammation and osteoclastogenic factors.

Conjugated linoleic acid inhibits osteoclast differentiation of RAW264.7 cells by modulating RANKL signaling

Bone destruction is a pathological hallmark of several chronic inflammatory diseases, including rheumatoid arthritis, periodontitis, and osteoporosis. Inflammation-induced bone loss of this sort results from increased numbers of bone-resorbing osteoclasts. Numerous studies have indicated that conjugated linoleic acid (CLA) positively influences calcium and bone metabolism. Gene-deletion studies have shown that receptor activator of nuclear factor-kappaB ligand (RANKL) is one of the critical mediators of osteoclastogenesis. In this report, we examine the ability of CLA to suppress RANKL signaling and osteoclastogenesis in RAW264.7 cells, a murine monocytic cell line. Treatment of these cells with RANKL activated nuclear factor-kappaB (NF-kappaB), and preexposure of the cells to CLA significantly suppressed RANKL-induced NF-kappaB activation, including phosphorylation of I-kappaBalpha, degradation of I-kappaBalpha, and nuclear translocation of p65. RANKL induced osteoclastogenesis in these monocytic cells, and CLA inhibited RANKL-induced tumor necrosis factor-alpha production and osteoclast differentiation, including osteoclast-specific genes such as tartrate-resistant acid phosphatase, cathepsin K, calcitonin receptor, and matrix metalloproteinase-9 expression and osteoclast-specific transcription factors such as c-Fos, nuclear factor of activated T-cells expression, and bone resorption pit formation. CLA also inhibited RANKL-induced activation of mitogen-activated protein kinase p38 but had little effect on c-Jun N-terminal kinase activation. Collectively, these data demonstrate for the first time that CLA inhibits osteoclastogenesis by modulating RANKL signaling. Thus, CLA may have important therapeutic implications for the treatment of bone diseases associated with enhanced bone resorption by excessive osteoclastogenesis.

Desaturation indices in liver, muscle, and bone of growing male and female mice fed trans-10, cis-12 conjugated linoleic acid

trans-10,cis-12-CLA (t10,c12-CLA) inhibits lipid deposition in adipose tissue of many species, but it also enhances lipid deposition in liver. We evaluated effects of dietary t10,c12-CLA content and gender on carcass composition, FA profile of selected tissues, and expression of FA synthase (FAS) and stearoyl-CoA desaturase-1 (SCD) mRNA in adipose tissue. Male and female (63 of each) CD-1 mice were assigned a diet containing 0.0, 0.15, or 0.30% t10,c12-CLA at 4 wk of age. Seven mice per dietary group within gender were sacrificed after 2, 4, or 6 wk. The CLA isomer caused dose-dependent reductions in dry carcass weight and fat content, without altering protein content, but carcass fat and epididymal fat pad weights of males were reduced to a greater extent than carcass fat and inguinal fat pad weights of females. FAS and SCD mRNA in adipose tissue was more abundant in females than males, but expression in both genders decreased as the t10,c12-CLA content of the diet increased. Although the weight of gastrocnemius muscle was not influenced by diet, total FA content of the muscle of both genders decreased in response to dietary t10,c12-CLA content. Femur weight of male mice increased as the t10,c12-CLA content of the diet increased, but the weight increase was associated with a reduction in total FA content. The delta 9 desaturation indices for muscle and femur suggested a linear reduction in SCD activity, whereas delta 9 indices for liver indicated linear enhancement of SCD activity. Overall, results suggested that growing male mice were more susceptible than females to t10,c12-CLA inhibition of lipid deposition.

Regulation of Osteoblast Gene Expression and Phenotype by Polylactide-fatty Acid Surfaces

Cell function is influenced by surface structure and molecules. Molecules that enhance cellular differentiation can be applied to tissue scaffold surfaces to stimulate endogenous tissue regeneration. The application of this approach to bone implants yields surfaces coated with factors (proteins, peptides, etc...) that promote the differentiation of osteoblasts, the cells that make bone. Increased bone formation leads to increased healing and union of the implant with endogenous bone. To obtain better control over surface coating we developed PLLA copolymers with allyl (PLLA-co-DAG) and 3-hydroxypropyl (PLLA-co-HP) side chains to which we can attach functional groups. Given the potential of fatty acids being able to incorporate into lipid bilayers and/or influence gene expression, we grafted different fatty acid side chains to PLLA-co-HP by esterifying the corresponding fatty acids with the PLLA-co-HP 3-hydroxypropyl side chains. The effects of the polymer modifications on osteoblasts were then evaluated. While cellular morphology differed between surface coatings, they did not reflect changes in cellular phenotype. Changes in gene expression were most evident with arachidonate and 3-hydroxypropyl side-chains which exhibited osteoblast differentiating capabilities. Linoleate, myristate, oleate, and stearate ester side-chains did not have a significant influence on osteoblast phenotype. Growth characteristics of osteoblasts did not differ between the fatty acid copolymer films, although cells grown on PLLA-co-HP exhibited a trend toward increased growth. Taken together our findings demonstrate that surface fatty acid composition can impact osteoblast phenotype.

The Effects of Conjugated Linoleic Acid Supplementation during Resistance Training

PURPOSE

We determined the effects of conjugated linoleic acid (CLA) supplementation during resistance training.

METHODS

Seventy-six subjects were randomized to receive CLA (5 g.d(-1)) or placebo (PLA) for 7 wk while resistance training 3 d.wk(-1). Seventeen subjects crossed over to the opposite group for an additional 7 wk. Measurements at baseline, 7 wk, and 14 wk (for subjects in the crossover study) included body composition, muscle thickness of the elbow flexors and knee extensors, resting metabolic rate (RMR), bench and leg press strength, knee extension torque, and urinary markers of myofibrillar degradation (3-methylhistidine (3MH) and bone resorption (cross-linked N-telopeptides (Ntx)).

RESULTS

After 7 wk the CLA group had greater increases in lean tissue mass (LTM) (+1.4 vs +0.2 kg; P < 0.05), greater losses of fat mass (-0.8 vs +0.4 kg; P < 0.05), and a smaller increase in 3MH (-0.1 vs + 1.3 micromol.kg LTM.d(-1); P < 0.05) compared with PLA. Changes between groups were similar for all other measurements, except for a greater increase in bench press strength for males on CLA (P < 0.05). In the crossover study subjects had minimal changes in body composition, but smaller increases in 3MH (-1.2 vs +2.2 micromol.kg LTM.d(-1); P < 0.01) and NTx (-4.8 vs +7.3 nmol.kg(-1) LTM.d(-1); P < 0.01) while on CLA versus PLA.

CONCLUSIONS

Supplementation with CLA during resistance training results in relatively small changes in body composition accompanied by a lessening of the catabolic effect of training on muscle protein.

Conjugated linoleic acid can prevent tumor necrosis factor gene expression by inhibiting nuclear factor binding activity in peripheral blood mononuclear cells from weaned pigs challenged with lipopolysaccharide

Twenty-four weanling barrows were fed corn-soybean diets supplemented with 2% conjugated linolenic acid (CLA) or soybean oil. On day 14 and 21, pigs were injected intraperitoneally with lipopolysaccharide (LPS) or sterile saline. Plasma samples were collected 2h after injection. Peripheral blood mononuclear cells (PBMC) were also collected on day 21, 2 h after injection to determine tumor necrosis factor-alpha (TNF-alpha) production and its mRNA expression. The results indicate that dietary CLA inhibited the production of TNF-alpha by pig PBMC both at the protein and mRNA expression level. In a second experiment, PBMC, collected from a healthy pig, were incubated with either c9,t11-CLA or t10,c12-CLA, or without CLA and stimulated with LPS. Both CLA isomers inhibited LPS-stimulated TNF-alpha production and expression, which may be partially due to inhibition of the binding activity of nuclear factor-kappaB. The t10,c12 isomer was more effective than the c9,t11-CLA isomer in reducing TNF-alpha levels and nuclear factor-kappaB activation.

Lack of effect of dietary conjugated linoleic acids naturally incorporated into butter on the lipid profile and body composition of overweight and obese men

BACKGROUND

Dietary conjugated linoleic acid (CLA) is known to reduce atherosclerosis, plasma total and LDL-cholesterol concentrations, and body fat accumulation in several animal species. Of the few studies that investigated the effects of CLA supplementation in humans, all used commercially formulated oral supplements made from a mixture of CLA isomers.

OBJECTIVE

We compared the effects on plasma lipoproteins and body composition of the consumption of a modified butter naturally enriched with CLA (CLA-B: 4.22 g CLA/100 g butter fat) by the addition of sunflower oil to the diet of dairy cows with the consumption of a control butter (CON-B) that was low in CLA (0.38 g CLA/100 g butter fat).

DESIGN

In a crossover design study including an 8-wk washout period, 16 men [x +/- SD age: 36.6 +/- 12.4 y; body mass index (in kg/m2): 31.2 +/- 4.4] were fed each of the 2 experimental isoenergetic diets, providing 15% of energy as protein, 45% as carbohydrates, and 40% as lipids, of which >60% was derived from experimental fats, for 4 wk.

RESULTS

Consumption of the CLA-B diet induced a significantly (P < 0.05) smaller reduction in plasma total cholesterol and in the ratio of total to HDL cholesterol (-0.02 mmol/L and -0.00, respectively) than did consumption of the CON-B diet (-0.26 mmol/L and-0.34, respectively). Abdominal adipose tissue area measured by computed tomography showed no difference in accumulation of either visceral or subcutaneous adipose tissue after the 2 experimental diets.

CONCLUSION

These results suggest that a 10-fold CLA enrichment of butter fat does not induce beneficial metabolic effects in overweight or obese men.

Association between Dietary Conjugated Linoleic Acid and Bone Mineral Density in Postmenopausal Women

OBJECTIVE

To determine if dietary conjugated linoleic acid (CLA) is associated with bone mineral density (BMD) of different skeletal sites in postmenopausal women.

METHODS

A cross-sectional analysis in 136 Caucasian, healthy, postmenopausal women, mean age 68.6 years. BMD and soft tissue were assessed by dual energy x-ray absorptiometry (DXA). Energy, calcium, protein, fat, CLA and other relevant nutrients were estimated using 3 day dietary records. Supplement use was recorded as well. Current and past physical activity were determined using the Allied Dunbar National Fitness Survey for older adults.

RESULTS

CLA (63.1 +/- 46.8 mg, mean +/- SD) was a significant predictor of Ward's triangle BMD (p = 0.040) in a multiple regression model containing years since menopause (18.5 +/- 8.4 y), lean tissue, energy intake (1691 +/- 382 kcal/day) dietary calcium (873 +/- 365 mg), protein (70.6 +/- 18.6 g), fat (57.9 +/- 23.9 g), zinc (19.2 +/- 13.6 mg), and current and past physical activity, with R(2)(adj) = 0.286. Subjects were also divided into groups below (Group 1) and above (Group 2) the median intake for CLA. Group 2 had higher BMD in the forearm, p = 0.042, and higher BMD in the hip, lumbar spine and whole body, however statistical significance was not reached.

CONCLUSION

These findings indicate dietary CLA may positively benefit BMD in postmenopausal women. More studies are warranted examining the relationship between dietary CLA and BMD.

Polyunsaturated fatty acids: biochemical, nutritional and epigenetic properties

Dietary polyunsaturated fatty acids (PUFA) have effects on diverse physiological processes impacting normal health and chronic diseases, such as the regulation of plasma lipid levels, cardiovascular and immune function, insulin action and neuronal development and visual function. Ingestion of PUFA will lead to their distribution to virtually every cell in the body with effects on membrane composition and function, eicosanoid synthesis, cellular signaling and regulation of gene expression. Cell specific lipid metabolism, as well as the expression of fatty acid-regulated transcription factors, likely play an important role in determining how cells respond to changes in PUFA composition. This review will focus on recent advances on the essentiality of these molecules and on their interplay in cell physiology, leading to new perspective in different therapeutic fields.

Conjugated linoleic acid attenuates the production and gene expression of proinflammatory cytokines in weaned pigs challenged with lipopolysaccharide

We investigated the anti-inflammatory role of conjugated linoleic acid (CLA) in inflammation-challenged weaned pigs and in in vitro cultured peripheral blood mononuclear cells (PBMCs). To test the hypothesis that inflammation responses can be attenuated by dietary CLA supplementation, we used an acute inflammation model in which pigs were injected with lipopolysaccharide (LPS). After 14 d of dietary supplementation with either 2% soybean oil or 2% CLA, half of the pigs in each diet group were challenged with LPS. Dietary CLA alleviated growth depression and prevented the elevations in production and mRNA expression of proinflammatory cytokines [i.e., interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha] induced by the LPS challenge. CLA enhanced the expression of interleukin-10 (IL-10) and peroxisome proliferator-activated receptor-gamma (PPARgamma) in spleen and thymus. To further elucidate the inhibitory effects and the mechanism of action of CLA on cytokine profiles (i.e., IL-1beta, IL-6, and TNF-alpha), PBMCs were isolated from weaned pigs and cultured in media containing cis-9, trans-11 (9c,11t) CLA and trans-10, cis-12 (10t,12c) CLA. Each CLA isomer suppressed the production and expression of IL-1beta, IL-6, and TNF-alpha, and enhanced PPARgamma activation and gene expression in cultured PBMCs. At the molecular level, the inhibitory actions of CLA on IL-1beta, IL-6, and TNF-alpha are attributable mainly to 10t,12c-CLA and the anti-inflammatory properties of CLA are mediated, at least in part, through a PPARgamma-dependent mechanism.

Conjugated linoleic acid reduces parathyroid hormone in health and in polycystic kidney disease in rats

BACKGROUND

Feeding conjugated linoleic acid (CLA) is reported to reduce prostaglandin E(2) synthesis, which is required for parathyroid hormone (PTH) release.

OBJECTIVE

This study was undertaken to determine whether CLA would suppress hyperparathyroidism and the resulting high-turnover bone disease in a rat model of polycystic kidney disease (PKD).

DESIGN

Outcome measurements were conducted after 8 wk of feeding diets supplemented with and without CLA (1% of dietary fat) to Han:SPRD-cy male rats (n = 52). PTH, bone formation, and resorption were assessed in addition to femur bone mass with use of dual-energy X-ray absorptiometry.

RESULTS

CLA feeding resulted in attenuation of PTH concentrations in both PKD-affected and nonaffected rats (by 60%) but did not significantly alter bone formation and resorption.

CONCLUSION

Reduction in PTH may open possibilities for CLA as an adjunctive therapy in secondary hyperparathyroidism.

An enriched mixture of trans-10,cis-12-CLA inhibits linoleic acid metabolism and PGE2 synthesis in MDA-MB-231 cells

Conjugated linoleic acid (CLA) isomers are potent inhibitors of mammary tumor cell growth. Evidence suggests that CLA modulates essential fatty acid (EFA) metabolism; however, it is not clear which parts of this pathway are important regulatory points modulated by CLA. Enriched mixtures of D9-cis,11-trans (D9c,11t)- and D10-trans,12-cis (D10t,12c)-18:2 were used to assess outcome measures of EFA metabolism pertaining to membrane phospholipid incorporation, tumor cell growth, and prostaglandin E2 (PGE2) synthesis in the MDA-MB-231 mammary tumor cell line. Tumor cells were treated with linoleic acid (LA), an equal mixture (Mix), or enriched preparations of D9c,11t- or D10t,12c-18:2. Treatment with Mix or the enriched mixture of D10t,12c-18:2 significantly inhibited the synthesis of arachidonic acid (AA) from LA, resulting in increased levels of LA and decreased levels of AA in membrane phosphatidylcholine and phosphatidylethanolamine (P < 0.05). LA and AA levels were not altered in cells treated with enriched D9c,11t-18:2 and were similar to those in LA control treated cells. All CLA treatments reduced [3H]thymidine uptake, an indicator of tumor cell growth, by more than one-half relative to LA controls. MDA-MB-231 cells challenged with AA in the presence of all CLA mixtures resulted in significantly reduced PGE2 synthesis relative to controls treated with LA (P < 0.05). It is evident that individual isomers exert inhibitory effects at specific steps of EFA metabolism, which correspondingly leads to a reduction in PGE2 synthesis and, ultimately, tumor growth.