Evidence for potential mechanisms for the effect of conjugated linoleic acid on tumor metabolism and immune function: lessons from n-3 fatty acids

Docosahexaenoic acid (DHA) impairs hypoxia-induced cellular and exosomal overexpression of immune-checkpoints and immunomodulatory molecules in different subtypes of breast cancer cells

BACKGROUND

Tumor cells express immune-checkpoint molecules to suppress anti-tumor immune responses. In part, immune evasion takes place by secreting exosomes bearing immune-checkpoint and immunomodulatory molecules and their inducing and/or regulating agents e.g., microRNAs (miRs). This study aimed to evaluate the effects of omega-3 fatty acid, docosahexaenoic acid (DHA), on the expression of some selected immune-checkpoint and immunomodulatory molecules and their regulating miRs under both normoxic and hypoxic conditions in triple negative (TNBC) invasive and triple positive non-invasive breast cancer cell lines.

METHODS

MDA-MB-231 and BT-474 cells were treated with 100 µM DHA under hypoxic and normoxic conditions for 24 h. Exosomes were isolated by ultracentrifuge and confirmed by electron microscope and anti-CD9, -CD63, -CD81 immunoblotting. Total RNA from cells and exosomes were extracted and expression of CD39, CD73, CD47, CD80, PD-L1, B7-H3, B7-H4 genes and their related miRs were evaluated by quantitative Real-time PCR.

RESULTS

This study showed significant over-expression of immune-checkpoint and immunomodulatory molecules under hypoxic condition. Treatment with DHA resulted in a significant decrease in immune-checkpoint and immunomodulatory molecule expression as well as an upregulation of their regulatory miRNA expression.

CONCLUSION

DHA supplementation may be utilized in breast cancer therapy for down-regulation of cellular and exosomal immune escape-related molecules.

Study of the Phytochemical Composition, Antioxidant Properties, and In Vitro Anti-Diabetic Efficacy of Gracilaria bursa-pastoris Extracts

In this study, a comparison was made of the chemical makeup of different extracts obtained from Gracilaria bursa-pastoris, a type of red seaweed that was gathered from the Nador lagoon situated in the northern part of Morocco. Additionally, their anti-diabetic and antioxidant properties were investigated. The application of GC-MS technology to analyze the fatty acid content of the samples revealed that linoleic acid and eicosenoic acid were the most abundant unsaturated fatty acids across all samples, with palmitic acid and oleic acid following in frequency. The HPLC analysis indicated that ascorbic and kojic acids were the most prevalent phenolic compounds, while apigenin was the most common flavonoid molecule. The aqueous extract exhibited significant levels of polyphenols and flavonoids, registering values of 381.31 ± 0.33 mg GAE/g and 201.80 ± 0.21 mg QE/g, respectively. Furthermore, this particular extract demonstrated a remarkable ability to scavenge DPPH radicals, as evidenced by its IC₅₀ value of 0.17 ± 0.67 mg/mL. In addition, the methanolic extract was found to possess antioxidant properties, as evidenced by its ability to prevent β-carotene discoloration, with an IC₅₀ ranging from 0.062 ± 0.02 mg/mL to 0.070 ± 0.06 mg/mL. In vitro study showed that all extracts significantly inhibited the enzymatic activity of α-amylase and α-glucosidase. Finally, molecular docking models were applied to assess the interaction between the primary phytochemicals identified in G. bursa-pastoris extracts and the human pancreatic α-amylase and α-glucosidase enzymes. The findings suggest that these extracts contain bioactive substances capable of reducing enzyme activity more effectively than the commercially available drug acarbose.

Anticancer activity of milk fat rich in conjugated linoleic acid against Ehrlich ascites carcinoma cells in female Swiss albino mice

Background and Aim:

The major conjugated linoleic acid (CLA) isomers have anticancer effect, especially breast cancer cells, inhibits cell growth and induces cell death. Also, CLA has several health benefits in vivo, including antiatherogenesis, antiobesity, and modulation of immune function. The present study aimed to assess the safety and anticancer effects of milk fat CLA against in vivo Ehrlich ascites carcinoma (EAC) in female Swiss albino mice. This was based on acute toxicity study, detection of the tumor growth, life span of EAC bearing hosts, and simultaneous alterations in the hematological, biochemical, and histopathological profiles.

Materials and Methods:

One hundred and fifty adult female mice were equally divided into five groups. Groups (1-2) were normal controls, and Groups (3-5) were tumor transplanted mice (TTM) inoculated intraperitoneally with EAC cells (2×10⁶/0.2 mL). Group (3) was (TTM positive control). Group (4) TTM fed orally on balanced diet supplemented with milk fat CLA (40 mg CLA/kg body weight). Group (5) TTM fed orally on balanced diet supplemented with the same level of CLA 28 days before tumor cells inoculation. Blood samples and specimens from liver and kidney were collected from each group. The effect of milk fat CLA on the growth of tumor, life span of TTM, and simultaneous alterations in the hematological, biochemical, and histopathological profiles were examined.

Results:

For CLA treated TTM, significant decrease in tumor weight, ascetic volume, viable Ehrlich cells accompanied with increase in life span were observed. Hematological and biochemical profiles reverted to more or less normal levels and histopathology showed minimal effects.

Conclusion:

The present study proved the safety and anticancer efficiency of milk fat CLA and provides a scientific basis for its medicinal use as anticancer attributable to the additive or synergistic effects of its isomers.

Dietary probiotic and metabolites improve intestinal homeostasis and prevent colorectal cancer

Metabolites from Lactobacillus casei display substantial antioxidant and anti-inflammatory activities, inhibit colorectal cancer cell proliferation and growth, and modulate gut microfloral composition, specifically reducing sulfidogenic bacteria.

Effect of Dietary Fish Oil on Mammary Gland Development and Milk Production of Holstein Cow

The aim of this study was to evaluate the effect of feeding oil supplement on mammary gland development and milk production responses in Holstein cows. Ten multiparous Holstein cows (42.2±9.2 d before calving, 3.25±0.25 body condition score, and 620±35 kg body weight) were randomly assigned to treatments. Treatments were a diet with oil added as palm oil (PO; n=5), or fish oil (FO; n=5) given to cows until 63 d in milk. Milk yield was recorded daily, milk composition (fat, protein, lactose, total solid and somatic cell count) was measured weekly and fatty acid profiles of milk fat were determined at first and last week of the experiment. Samples of mammary tissue were obtained at 7 and 63 d in milk by biopsy gun. Tissue slides were analyzed by Image J software. Results showed that fish oil supplemented diet compared to the palm oil supplemented diet increased milk production after 6 weeks of lactation (P<0.05), content of polyunsaturated fatty acids milk fat (P<0.05) and docosahexaenoic acid (P<0.01). Moreover, n-6:n-3 ratio was decreased by fish oil supplement (P<0.05). Histological studies showed that FO increased the relative percentage of tissue area occupied by epithelial cells as well as a number of total alveoli in each microscopic field (P<0.05). Data suggested that feeding fish oil during the dry period and early lactation could improve development and function of the mammary gland in the dairy cow.

The Growth-Inhibiting Effects of Beef Fatty Acids on MCF-7 Cells Are Influenced Mostly by the Depot Location and Inconsistently by the Biohydrogenation Intermediate Content

Biohydrogenation intermediates (BHI) including conjugated linoleic acid (CLA) isomers are formed during ruminal biohydrogenation of polyunsaturated fatty acids (PUFA) in ruminants. Although many studies have examined the anticarcinogenic effects of CLA, few studies have reported the anticarcinogenic properties of BHI in their natural form found in dairy and beef fats. The present study compared the growth-inhibitory effects of fatty acids from beef perirenal fat (PRF) or subcutaneous fat (SCF) with low or high levels of BHI in MCF-7 human breast cancer cells. Cells were exposed for 72 h to media containing increasing doses (50 to 400 μM) of different beef fat treatments. Fatty-acid analysis showed that BHI were readily incorporated into cell phospholipids (PL) in a treatment-dependent manner, but higher BHI in PL did not consistently inhibit growth. Culturing with low-BHI PRF or high-BHI PRF did not lead to growth inhibition, but low-BHI SCF inhibited growth, and inhibition was further increased by high-BHI SCF. Other classes of fatty acids may, therefore, be interacting with BHI resulting in differential effects on growth inhibition in human breast cancer cells.

Omega-3 Polyunsaturated Fatty Acids Time-Dependently Reduce Cell Viability and Oncogenic MicroRNA-21 Expression in Estrogen Receptor-Positive Breast Cancer Cells (MCF-7)

The omega-3 polyunsaturated fatty acid (n-3 PUFA), α-linolenic acid (ALA), and its metabolites, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), independently reduce the growth of breast cancer cells in vitro, but the mechanisms, which may involve microRNA (miRNA), are still unclear. The expression of the oncomiR, miR-21, is reduced by DHA treatment, but the effects of ALA on miR-21, alone or combined with EPA and DHA under physiologically relevant concentrations, have not been investigated. The effects of ALA alone and +/-EPA and DHA at the blood molar ratios seen in either humans (1.0:1.0:2.5, ALA:EPA:DHA) or mice (1.0:0.4:3.1, ALA:EPA:DHA) post flaxseed oil consumption (containing ALA) were assessed in vitro in MCF-7 breast cancer cells. Cell viability and the expression of miR-21 and its molecular target, phosphatase and tension homolog (PTEN, gene and protein), at different time points, were examined. At 1, 3, 48 and 96 h ALA alone and 24 h animal ratio treatments significantly reduced MCF-7 cell viability, while 1 and 3 h ALA alone and human and animal ratio treatments all significantly reduced miR-21 expression, and 24 h animal ratio treatment reduced miR-21 expression; these effects were not associated with changes in PTEN gene or protein expressions. We showed for the first time that ALA alone or combined with EPA and DHA at levels seen in human and animal blood post-ALA consumption can significantly reduce cell viability and modulate miR-21 expression in a time- and concentration-dependent manner, with the animal ratio containing higher DHA having a greater effect. The time dependency of miR-21 effects suggests the significance of considering time as a variable in miRNA studies, particularly of miR-21.

The influence of dietary immunomodulatory factors on development of food allergy in children

In the last few years many studies have been conducted on the role of dietary and environmental factors in the prevention of allergic diseases among children. Many studies have shown that the diet of pregnant women and children in their early postnatal life, rich in antioxidants, vitamin D, and fatty acids is beneficial as it reduces the risk of allergy in their future life. Moreover, there are many reports about the main role of gut microbiota and probiotics in the allergy prevention, what can indicate new ways of procedures in allergic diseases.

Perillyl alcohol: Dynamic interactions with the lipid bilayer and implications for long-term inhalational chemotherapy for gliomas

Background:

Gliomas display a high degree of intratumor heterogeneity, including changes in physiological parameters and lipid composition of the plasma membrane, which may contribute to the development of drug resistance. Biophysical interactions between therapeutic agents and the lipid components at the outer plasma membrane interface are critical for effective drug uptake. Amphipathic molecules such as perillyl alcohol (POH) have a high partition coefficient and generally lead to altered lipid acyl tail dynamics near the lipid-water interface, impacting the lipid bilayer structure and transport dynamics. We therefore hypothesized that glioma cells may display enhanced sensitivity to POH-induced apoptosis due to plasma membrane alterations, while in non-transformed cells, POH may be expelled through thermal agitation.

Methods:

Interactions between POH and the plasma membrane was studied using molecular dynamics simulations. In this phase I/II trial, we set up to evaluate the clinical effectiveness of long-term (up to 5 years) daily intranasal administration of POH in a cohort of 19 patients with low-grade glioma (LGG). Importantly, in a series of clinical studies previously published by our group, we have successfully established that intranasal delivery of POH to patients with malignant gliomas is a viable and effective therapeutic strategy.

Results:

POH altered the plasma membrane potential of the lipid bilayer of gliomas and prolonged intranasal administration of POH in a cohort of patients with LGG halted disease progression with virtually no toxicity.

Conclusion:

Altogether, the results suggest that POH-induced alterations of the plasma membrane might be contributing to its therapeutic efficacy in preventing LGG progression.

Nanotechnology-Based Drug Delivery Systems for Melanoma Antitumoral Therapy: A Review

Melanoma (MEL) is a less common type of skin cancer, but it is more aggressive with a high mortality rate. The World Cancer Research Fund International (GLOBOCAN 2012) estimates that there were 230,000 new cases of MEL in the world in 2012. Conventional MEL treatment includes surgery and chemotherapy, but many of the chemotherapeutic agents used present undesirable properties. Drug delivery systems are an alternative strategy by which to carry antineoplastic agents. Encapsulated drugs are advantageous due to such properties as high stability, better bioavailability, controlled drug release, a long blood circulation time, selective organ or tissue distribution, a lower total required dose, and minimal toxic side effects. This review of scientific research supports applying a nanotechnology-based drug delivery system for MEL therapy.

A single-cell correlative nanoelectromechanosensing approach to detect cancerous transformation: monitoring the function of F-actin microfilaments in the modulation of the ion channel activity

Cancerous transformation may be dependent on correlation between electrical disruptions in the cell membrane and mechanical disruptions of cytoskeleton structures. Silicon nanotube (SiNT)-based electrical probes, as ultra-accurate signal recorders with subcellular resolution, may create many opportunities for fundamental biological research and biomedical applications. Here, we used this technology to electrically monitor cellular mechanosensing. The SiNT probe was combined with an electrically activated glass micropipette aspiration system to achieve a new cancer diagnostic technique that is based on real-time correlation between mechanical and electrical behaviour of single cells. Our studies demonstrated marked changes in the electrical response following increases in the mechanical aspiration force in healthy cells. In contrast, such responses were extremely weak for malignant cells. Confocal microscopy results showed the impact of actin microfilament remodelling on the reduction of the electrical response for aspirated cancer cells due to the significant role of actin in modulating the ion channel activity in the cell membrane.

Synthesis of conjugated linoleic acid by the linoleate isomerase complex in food-derived lactobacilli

AIMS

To assess strains of lactobacilli for their capacity to produce functional fatty acid-conjugated linoleic acid. To assess the linoleate isomerase for CLA production in the most efficient CLA producer.

METHODS AND RESULTS

In this study, strains of food-derived lactobacilli were cultured in media with linoleic acid and CLA production was assessed. Most of the selected strains produced CLA at different levels, with Lactobacillus plantarum ZS2058 being the most efficient CLA producer converting over 50% of linoleic acid to c9, t11-CLA and t9, t11-CLA. Some intermediates 10-hydroxy-cis-12-octadecenoic acid, 10-oxo-cis-12-octadecenoic acid and 10-oxo-trans-11-octadecenoic acid were determined via GC-MS. The genes coding the multicomponent linoleate isomerase containing myosin-cross-reactive antigen, short-chain dehydrogenase/oxidoreductase and acetoacetate decarboxylase for CLA production in Lact. plantarum ZS2058 were cloned and expressed in Escherichia coli. With the mixture of recombinant E. coli, c9, t11-CLA and three kinds of intermediates were produced from linoleic acid, which were in line with those in the lactobacilli.

CONCLUSIONS

The ability for CLA production by lactobacilli exhibited variation. Lactobacillus plantarum and Lact. bulgaricus were the most efficient producers in the selected strains. Lact. plantarum ZS2058 converted linoleic acid to CLAs with 10-hydroxy-cis-12-octadecenoic acid, 10-oxo-cis-12-octadecenoic acid and 10-oxo-trans-11-octadecenoic acid as intermediates. The multiple-step reactions for CLA production catalysed by multicomponent linoleate isomerase in Lact. plantarum ZS2058 were confirmed successfully.

SIGNIFICANCE AND IMPACT OF THE STUDY

Multicomponent linoleate isomerase provides important results for the illustration of the mechanism for CLA production in lactic acid bacteria. Food-derived lactobacilli with CLA production ability offers novel opportunities for functional foods development.

Matrix metalloproteinase (MMP)-9 in cancer-associated fibroblasts (CAFs) is suppressed by omega-3 polyunsaturated fatty acids in vitro and in vivo

Cancer associated fibroblasts (CAFs) are responsible for tumor growth, angiogenesis, invasion, and metastasis. Matrix metalloproteinase (MMP)-9 secreted from cancer stroma populated by CAFs is a prerequisite for cancer angiogenesis and metastasis. Omega-3 polyunsaturated fatty acids (omega-3 PUFA) have been reported to have anti-tumor effects on diverse types of malignancies. Fat-1 mice, which can convert omega-6 to omega-3 PUFA independent of diet, are useful to investigate the functions of endogenous omega-3 PUFA. To examine the effect of omega-3 PUFA on tumorigenesis, TC-1 cells, a murine epithelial cell line immortalized by human papillomavirus (HPV) oncogenes, were injected subcutaneously into fat-1 or wild type mice. Tumor growth and angiogenesis of the TC-1 tumor were significantly suppressed in fat-1 compared to wild type mice. cDNA microarray of the tumors derived from fat-1 and wild type mice revealed that MMP-9 is downregulated in fat-1 mice. Immunohistochemical study demonstrated immunoreactivity for MMP-9 in the tumor stromal fibroblasts was diffusely positive in wild type whereas focal in fat-1 mice. MMP-9 was expressed in primary cultured fibroblasts isolated from fat-1 and wild type mice but was not expressed in TC-1 cells. Co-culture of fibroblasts with TC-1 cells enhanced the expression and the proteinase activity of MMP-9, although the protease activity of MMP-9 in fat-1-derived fibroblasts was lower than that in wild type fibroblasts. Our data suggests that omega-3 PUFAs suppress MMP-9 induction and tumor angiogenesis. These findings may provide insight into mechanisms by which omega-3 PUFAs exert anti-tumor effects by modulating tumor microenvironment.

Trans fatty acid intake is associated with increased risk and n3 fatty acid intake with reduced risk of non-hodgkin lymphoma

We evaluated the association of dietary fat and protein intake with risk of non-Hodgkin lymphoma (NHL) in a clinic-based study in 603 cases (including 218 chronic lymphocytic leukemia/small lymphocytic lymphoma, 146 follicular lymphoma, and 105 diffuse large B-cell lymphoma) and 1007 frequency-matched controls. Usual diet was assessed with a 128-item food-frequency questionnaire. Unconditional logistic regression was used to estimate ORs and 95% CIs, and polytomous logistic regression was used to assess subtype-specific risks. trans Fatty acid (TFA) intake was positively associated with NHL risk [OR = 1.60 for highest vs. lowest quartile (95% CI = 1.18, 2.15); P-trend = 0.0014], n3 (ω3) fatty acid intake was inversely associated with risk [OR = 0.48 (95% CI = 0.35, 0.65); P-trend < 0.0001], and there was no association with total, animal, plant-based, or saturated fat intake. When examining intake of specific foods, processed meat [OR = 1.37 (95% CI = 1.02, 1.83); P-trend = 0.03], milk containing any fat [OR = 1.47 (95% CI = 1.16, 1.88); P-trend = 0.0025], and high-fat ice cream [OR = 4.03 (95% CI = 2.80, 5.80); P-trend < 0.0001], intakes were positively associated with risk, whereas intakes of fresh fish and total seafood [OR = 0.61 (95% CI = 0.46, 0.80); P-trend = 0.0025] were inversely associated with risk. Overall, there was little evidence for NHL subtype-specific heterogeneity. In conclusion, diets high in TFAs, processed meats, and higher fat dairy products were positively associated with NHL risk, whereas diets high in n3 fatty acids and total seafood were inversely associated with risk.

Exploring risk factors for follicular lymphoma

Follicular lymphoma (FL) is an indolent malignancy of germinal center B cells with varied incidence across racial groups and geographic regions. Improvements in the classification of non-Hodgkin lymphoma subtypes provide an opportunity to explore associations between environmental exposures and FL incidence. Our paper found that aspects of Western lifestyle including sedentary lifestyle, obesity, and diets high in meat and milk are associated with an increased risk of FL. Diets rich in fruits and vegetables, polyunsaturated fatty acids, vitamin D, and certain antioxidants are inversely associated with FL risk. A medical history of Sjogren's syndrome, influenza vaccination, and heart disease may be associated with FL incidence. Associations between FL and exposure to pesticides, industrial solvents, hair dyes, and alcohol/tobacco were inconsistent. Genetic risk factors include variants at the 6p21.32 region of the MHC II locus, polymorphisms of the DNA repair gene XRCC3, and UV exposure in individuals with certain polymorphisms of the vitamin D receptor. Increasing our understanding of risk factors for FL must involve integrating epidemiological studies of genetics and exposures to allow for the examination of risk factors and interactions between genes and environment.

Polyunsaturated Fatty acids of marine macroalgae: potential for nutritional and pharmaceutical applications

As mammals are unable to synthesize essential polyunsaturated fatty acids (PUFA), these compounds need to be taken in through diet. Nowadays, obtaining essential PUFA in diet is becoming increasingly difficult; therefore this work investigated the suitability of using macroalgae as novel dietary sources of PUFA. Hence, 17 macroalgal species from three different phyla (Chlorophyta, Phaeophyta and Rhodophyta) were analyzed and their fatty acid methyl esters (FAME) profile was assessed. Each phylum presented a characteristic fatty acid signature as evidenced by clustering of PUFA profiles of algae belonging to the same phylum in a Principal Components Analysis. The major PUFA detected in all phyla were C₁₈ and C₂₀, namely linoleic, arachidonic and eicosapentaenoic acids. The obtained data showed that rhodophytes and phaeophytes have higher concentrations of PUFA, particularly from the n-3 series, thereby being a better source of these compounds. Moreover, rhodophytes and phaeophytes presented “healthier” ∑n-6/∑n-3 and PUFA/saturated fatty acid ratios than chlorophytes. Ulva was an exception within the Chlorophyta, as it presented high concentrations of n-3 PUFA, α-linolenic acid in particular. In conclusion, macroalgae can be considered as a potential source for large-scale production of essential PUFA with wide applications in the nutraceutical and pharmacological industries.

Effects of margarine supplemented with t10c12 and C9T11 CLA on atherosclerosis and steatosis in apoE/LDLR -/- mice

OBJECTIVES

The objective of this study was to evaluate functional effects of margarine supplemented with individual CLA isomers trans-10, cis-12 and cis-9, trans-11 in apoE/LDLR -/- mice.

DESIGN

In LONG experiment (LONG), two-month old mice with no atherosclerosis were assigned to experimental groups and fed for the next 4 months. In SHORT experiment (SHORT), four-month old mice, with pre-established atherosclerosis, were assigned to experimental groups and fed for the next 2 months. The experimental diets were: AIN-93G (margarine), AIN-93G + 0.5% trans-10, cis-12 CLA (t10c12), and AIN-93G + 0.5% cis-9, trans-11 CLA (c9t11).

RESULTS

In both experiments (LONG and SHORT), liver weight was significantly (P<0.05) increased in mice fed t10c12 CLA. Hepatic steatosis was found in animals fed t10c12 diet and no signs of the steatosis was observed in mice fed c9t11 CLA. Dietary treatments with t10c12 CLA significantly increased total plasma cholesterol and plasma triacylglycerols. There were no isomer-specific effects of CLA isomers on area of atherosclerotic plaque in aortic root.

CONCLUSION

In conclusion, t10c12 CLA significantly increased liver weight in mice in LONG and SHORT experiments. Our results do not support the notion that CLA isomer supplementation to the margarine possess anti-atheroclerotic effect. Therefore, no isomer-specific effects of CLA on development of atherosclerosis were observed.

Review:Trans-forming beef to provide healthier fatty acid profiles

Dugan, M. E. R., Aldai, N., Aalhus, J. L., Rolland, D. C. and Kramer, J. K. G. 2011. Review: Trans- forming beef to provide healthier fatty acid profiles. Can. J. Anim. Sci. 91: 545–556.Trans fatty acids are found naturally in foods, particularly in those derived from ruminant animals, such as beef and dairy cattle. Over the past few decades, human consumption of trans fatty acids has increased, but this has been mainly from products containing partially hydrogenated vegetable oils. The correlation of trans fatty acid consumption with diseases such as coronary heart disease has been cause for concern, and led to recommendations to reduce their consumption. Trans fatty acids, however, have differing effects on human health. Therefore, in foods produced from ruminant animals, it is important to know their trans fatty acid composition, and how to enrich or deplete fatty acids that have positive or negative health effects. This review will cover the analysis of trans fatty acids in beef, their origin, how to manipulate their concentrations, and give a brief overview of their health effects.

Effects of n-3 PUFAs on breast cancer cells through their incorporation in plasma membrane

Background

PUFAs are important molecules for membrane order and function; they can modify inflammation-inducible cytokines production, eicosanoid production, plasma triacylglycerol synthesis and gene expression. Recent studies suggest that n-3 PUFAs can be cancer chemopreventive, chemosuppressive and auxiliary agents for cancer therapy. N-3 PUFAs could alter cancer growth influencing cell replication, cell cycle, and cell death. The question that remains to be answered is how n-3 PUFAs can affect so many physiological processes. We hypothesize that n-3 PUFAs alter membrane stability, modifying cellular signalling in breast cancer cells.

Methods

Two lines of human breast cancer cells characterized by different expression of ER and EGFR receptors were treated with AA, EPA or DHA. We have used the MTT viability test and expression of apoptotic markers to evaluate the effect of PUFAs on cancer growth. Phospholipids were analysed by HPLC/GC, to assess n-3 incorporation into the cell membrane.

Results

We have observed that EPA and DHA induce cell apoptosis, a reduction of cell viability and the expression of Bcl2 and procaspase-8. Moreover, DHA slightly reduces the concentration of EGFR but EPA has no effect. Both EPA and DHA reduce the activation of EGFR.

N-3 fatty acids are partially metabolized in both cell lines; AA is integrated without being further metabolized. We have analysed the fatty acid pattern in membrane phospholipids where they are incorporated with different degrees of specificity. N-3 PUFAs influence the n-6 content and vice versa.

Conclusions

Our results indicate that n-3 PUFA feeding might induce modifications of breast cancer membrane structure that increases the degree of fatty acid unsaturation. This paper underlines the importance of nutritional factors on health maintenance and on disease prevention.

Effect of conjugated linoleic acid (CLA) on lipid profile and liver histology in laboratory rats fed high-fructose diet

The objective of the study was to assess the effect of CLA on serum lipid profile, plasma malondialdehyde and liver histology in Wistar rats fed high-fructose diet. Eighteen rats were randomly assigned to three experimental groups and fed for the next 21 days. The experimental diets were: I, Control; II, Fructose (63.2% of fructose); and III, CLA+Fructose (1% CLA and 63.2% of fructose). The experimental treatments had no effect on body weight of the rats. The LDL+VLDL cholesterol, TG and liver weight were significantly increased in animals fed Fructose. MDA concentrations were significantly increased in rats fed Fructose diet but CLA+Fructose diet had no effect on this marker. In the same line, the histological examination of the livers showed a series of morphological alterations, notably hepatic steatosis in animals fed high-fructose diet. No signs of the steatosis in rats fed CLA+Fructose diet were observed. In conclusion, CLA in high-fructose diet, decreases serum LDL+VLDL and TG and plasma MDA concentrations as well as liver weight and liver cholesterol, thus opposing the effects of high-fructose diet and showing a potential antiatherogenic effect. Similarly, dietary CLA fed at 1% level (w/w) in high-fructose diet, prevented steatosis observed histologically in livers of rats fed high-fructose diets.

Abnormal fatty acid distribution of the serum phospholipids of patients with non-Hodgkin lymphoma

The data about the fatty acid (FA) status of non-Hodgkin lymphoma (NHL) patients are poor. Therefore, the aim of this study was to investigate the FA profile of serum phospholipids in NHL patients related to the aggressiveness and clinical stage of NHL. We analyzed the FA profile of serum phospholipids in 47 newly diagnosed, untreated NHL patients and in 29 healthy subjects. Significantly higher (p < 0.001) levels of palmitic (16:0), oleic (18:1 n-9) and arachidonic acids (20:4 n-6), saturated and monounsaturated FA were found in NHL patients, while linoleic acid (18:2 n-6) and the levels of total polyunsaturated FA (PUFA), n-3 PUFA, eicosapentaenoic (20:5 n-3) and docosahexaenoic (DHA, 22:6 n-3) were significantly reduced (p < 0.01). The level of oleic acid in patients with indolent NHL was significantly lower (p < 0.05) than in more aggressive types of disease. Contents of palmitoleic acid, docosatetraenoic (22:4 n-6), and PUFA was lower in very aggressive NHL. According to clinical stage (CS), patients with CS I had significantly higher SFA and lower n-6 FA than other three groups, and group with CS IV showed significantly decreased DHA and n-3 PUFA. Our results showed an abnormal FA profile in serum phospholipids in NHL patients.

Cytotoxic activity of an octadecenoic acid extract from Euphorbia kansui (Euphorbiaceae) on human tumour cell strains

We have investigated the cytotoxic and antitumour activity of an octadecenoic acid extract, mainly containing oleic and linoleic acids, from Euphorbia kansui on human gastric (SGC-7901), hepatocellular carcinoma (BEL-7402), and leukaemia (HL-60) tumour cell strains. Significant and dose-dependent antiproliferation effects were observed on tumour cells from the dose of 3.2 μg mL−1, which were comparable with or better than those of the common antitumour agent 5-fluorouracil. Results from the clone formation assay and flow cytometry indicated that the mixture of octadecenoic acids resulted in a dose-dependent reduction in the number of tumour cells and significantly inhibited cell proliferation, with induced apoptosis and G0/G1 phase cell cycle arrest. Also, the octadecenoic acids could not only cause cell apoptosis/necrosis but also functionally and structurally damage the tumour cell membrane and cell ultra-structures. These observations encourage further clinical evaluation of the inhibitory effects of octadecenoic acids on various forms of cancer.

A meta-analysis of the effects of conjugated linoleic acid on fat-free mass in humans

Treatment of laboratory animals with a 50:50 mixture of c9,t11 and t10,c12 conjugated linoleic acid (CLA) results in fat loss and, to a smaller degree, fat-free mass (FFM) gain. In a previous meta-analysis, we found that CLA produced a fat loss, but that humans were not as responsive as mice. We performed a similar meta-analysis in the same 18 studies to test whether CLA increased FFM. Only placebo-controlled trials that measured body composition were included. We found that FFM increased during CLA treatment (0.3 +/- 0.7 kg; p = 0.05), but that the change did not display an effect of length of treatment (0.001 +/- 0.005 kg.week(-1); p = 0.8), or an effect of dosage (0.1 +/- 0.1 kg.g CLA(-1).day(-1); p = 0.3). We conclude that FFM does increase in humans during CLA treatment, but the onset of the increase is rapid and the total increase is small (<1%).

Conjugated linoleic acids as functional food: an insight into their health benefits

This review evaluates the health benefits of the functional food, conjugated linoleic acids (CLA) - a heterogeneous group of positional and geometric isomers of linoleic acid predominantly found in milk, milk products, meat and meat products of ruminants. During the past couple of decades, hundreds of reports - principally based on in vitro, microbial, animal, and of late clinical trials on humans - have been accumulating with varying biological activities of CLA isomers. These studies highlight that CLA, apart form the classical nuclear transcription factors-mediated mechanism of action, appear to exhibit a number of inter-dependent molecular signalling pathways accounting for their reported health benefits. Such benefits relate to anti-obesitic, anti-carcinogenic, anti-atherogenic, anti-diabetagenic, immunomodulatory, apoptotic and osteosynthetic effects. On the other hand, negative effects of CLA have been reported such as fatty liver and spleen, induction of colon carcinogenesis and hyperproinsulinaemia. As far as human consumption is concerned, a definite conclusion for CLA safety has not been reached yet. Parameters such as administration of the type of CLA isomer and/or their combination with other polyunsaturated fatty acids, mode of administration (eg., as free fatty acid or its triglyceride form, liquid or solid), daily dose and duration of consumption, gender, age, or ethnic and geographical backgrounds remain to be determined. Yet, it appears from trials so far conducted that CLA are functional food having prevailing beneficial health effects for humans.

Conjugated linoleic acid isomers: differences in metabolism and biological effects

The term conjugated linoleic acid (CLA) refers to a mixture of linoleic acid positional and geometric isomers, characterized by having conjugated double bonds, not separated by a methylene group as in linoleic acid. CLA isomers appear as a minor component of the lipid fraction, found mainly in meat and dairy products from cows and sheep. The most abundant isomer is cis-9,trans-11, which represents up to 80% of total CLA in food. These isomers are metabolized in the body through different metabolic pathways, but important differences, that can have physiological consequences, are observed between the two main isomers. The trans-10,cis-12 isomer is more efficiently oxidized than the cis-9,trans-11 isomer, due to the position of its double bounds. Interest in CLA arose in its anticarcinogenic action but there is an increasing amount of specific scientific literature concerning the biological effects and properties of CLA. Numerous biological effects of CLA are due to the separate action of the most studied isomers, cis-9,trans-11 and trans-10,cis-12. It is also likely that some effects are induced and/or enhanced by these isomers acting synergistically. Although the cis-9,trans-11 isomer is mainly responsible for the anticarcinogenic effect, the trans-10,cis-12 isomer reduces body fat and it is referred as the most effective isomer affecting blood lipids. As far as insulin function is concerned, both isomers seem to be responsible for insulin resistance in humans. Finally, with regard to the immune system it is not clear whether individual isomers of CLA could act similarly or differently.

Effects of dietary supplementation with conjugated linoleic acid on experimental human rhinovirus infection and illness

Background

Because studies suggest that the dietary supplement conjugated linoleic acid (CLA) has immunomodulatory activities that might benefit common colds, we performed two studies of CLA effects in experimental human rhinovirus (HRV) infection.

Methods

The first study explored whether CLA supplementation (Safforin™; Loders Croklaan, BV, Wormerveer, the Netherlands) altered the virological or clinical course of experimental HRV infection, and the second explored whether CLA affected the frequency and severity of HRV cold-associated sore throat and cough. The trials were randomized, double-blinded and placebo-controlled. In total, 50 healthy volunteers aged 18–45 years and susceptible to HRV type-39 (serum neutralizing antibody titre ≤1:2) participated in study 1 and 80 similar volunteers susceptible to Hank's HRV participated in study 2. Participants ingested CLA 2 g/day or placebo for 4 weeks before and 4 days following intranasal HRV inoculation. The primary endpoint for study 1 was the frequency of colds and for study 2 was the symptom severity scores for sore throat and cough.

Results

In study 1, 10/24 (42%) placebo compared with 7/21 (33%) CLA participants developed colds ( P=0.53). CLA was associated with significant reductions in mean scores for cough (0 CLA versus 0.9 placebo) and sore throat (0.8 CLA versus 2.9 placebo). In study 2, clinical colds developed in 19/33 (58%) placebo and 27/43 (63%) CLA participants. Symptom scores for cough (0.9 CLA versus 1.0 placebo) and sore throat (2.6 CLA versus 3.2 placebo) were not significantly different. Similarly no differences in nasal viral titres or serological responses were found.

Conclusions

CLA dietary supplementation had no consistent effects on the virological or clinical course of experimental HRV colds. A larger study would be required to detect more subtle effects of CLA on HRV cold-associated symptoms.

Effects of increasing docosahexaenoic acid intake in human healthy volunteers on lymphocyte activation and monocyte apoptosis

Dietary intake of long-chain n-3 PUFA has been reported to decrease several markers of lymphocyte activation and modulate monocyte susceptibility to apoptosis. However, most human studies examined the combined effect of DHA and EPA using relatively high daily amounts of n-3 PUFA. The present study investigated the effects of increasing doses of DHA added to the regular diet of human healthy volunteers on lymphocyte response to tetradecanoylphorbol acetate plus ionomycin activation, and on monocyte apoptosis induced by oxidized LDL. Eight subjects were supplemented with increasing daily doses of DHA (200, 400, 800, 1600 mg) in a TAG form containing DHA as the only PUFA, for 2 weeks each dose. DHA intake dose-dependently increased the proportion of DHA in mononuclear cell phospholipids, the augmentation being significant after 400 mg DHA/d. The tetradecanoylphorbol acetate plus ionomycin-stimulated IL-2 mRNA level started to increase after ingestion of 400 mg DHA/d, with a maximum after 800 mg intake, and was positively correlated (P < 0.003) with DHA enrichment in cell phospholipids. The treatment of monocytes by oxidized LDL before DHA supplementation drastically reduced mitochondrial membrane potential as compared with native LDL treatment. Oxidized LDL apoptotic effect was significantly attenuated after 400 mg DHA/d and the protective effect was maintained throughout the experiment, although to a lesser extent at higher doses. The present results show that supplementation of the human diet with low DHA dosages improves lymphocyte activability. It also increases monocyte resistance to oxidized LDL-induced apoptosis, which may be beneficial in the prevention of atherosclerosis.

Abnormal immune responses in fa/fa Zucker rats and effects of feeding conjugated linoleic acid

OBJECTIVE

The objective of this study was to characterize immune function in the fa/fa Zucker rat, and to determine the effects of feeding conjugated linoleic acid (CLA) isomers on immune function.

METHODS AND PROCEDURES

Lean and fa/fa Zucker rats were fed for 8 weeks nutritionally complete diets with different CLA isomers (%wt/wt): control (0%), c9t11 (0.4%), t10c12 (0.4%), or MIX (0.4% c9t11 + 0.4% t10c12). Isolated splenocytes were used to determine phospholipid (PL) fatty acid composition and cell phenotypes, or stimulated with mitogen to determine their ability to produce cytokines, immunoglobulins (Ig), and nitric oxide (NO).

RESULTS

Splenocyte PL of fa/fa rats had a higher proportion of total monounsaturated fatty acids and n -3 polyunsaturated fatty acids (PUFA), and lower n -6 PUFA and n -6-to-n -3 PUFA ratio (P < 0.05). Feeding CLA increased the content of CLA isomers into PL, but there were lower proportions of each CLA isomer in fa/fa rats. Splenocytes of fa/fa rats produced more amounts of IgA, IgG, and IgM, NO, and interleukin-1beta (IL-1beta), IL-6, and tumor necrosis factor-alpha (TNF-alpha) (P < 0.05). Obese rats fed the t10c12 diet produced less TNF-alpha and IL-1beta (lippopolysaccharide (LPS), P < 0.05). Splenocytes of fa/fa rats produced less concanavalin A (ConA)-stimulated IL-2 (P < 0.0001) than lean rats, except fa/fa rats fed the c9t11 diet (P < 0.05).

DISCUSSION

The c9t11 and t10c12 CLA isomers were incorporated into the membrane PL of the fa/fa Zucker rat, but to a lesser extent than lean rats. Splenocytes of obese rats responded in a proinflammatory manner and had reduced T-cell function and feeding the t10c12 and c9t11 CLA isomers may improve some of these abnormalities by distinct methods.

PPARalpha and PP2A are involved in the proapoptotic effect of conjugated linoleic acid on human hepatoma cell line SK-HEP-1

Conjugated linoleic acid (CLA), found in dairy products, in beef and lamb has been demonstrated to possess anticancer properties protecting several tissues from developing cancer. Moreover, it has been shown to modulate apoptosis in several cancer cell lines. The aim of this study was to investigate which signaling transduction pathways were modulated in CLA-induced apoptosis in human hepatoma SK-HEP-1 cells. The cells exposed to CLA were evaluated for PPARalpha, PP2A, pro-apoptotic proteins Bak, Bad and caspases, and anti-apoptotic proteins Bcl-2 and Bcl-X(L). Cells were also treated with okadaic acid, a PP2A inhibitor, or with Wy-14643, a specific PPARalpha agonist. The CLA-induced apoptosis was concomitant to the increase of percentage of cells in the S phase, PPARalpha, PP2A and pro-apoptotic proteins; simultaneously, antiapoptotic proteins decreased. Inhibition of PP2A prevented apoptosis, and PPARalpha agonist showed similar effect as CLA. The increased PP2A could be responsible for the dephosphorylation of Bcl-2 and Bad, permitting apoptotic activity of Bax and Bad. The increase of caspase 8 and 9 suggested that both the intrinsic and extrinsic apoptotic pathways were induced. PP2A was probably increased by PPARalpha, since putative PPRE sequences were found in genes encoding its subunits. In conclusion, CLA induces apoptosis in human hepatoma SK-HEP-1 cells, by increasing PPARalpha, PP2A and pro-apoptotic proteins.

Conjugated linoleic acid supplementation reduces peripheral blood mononuclear cell interleukin-2 production in healthy middle-aged males

Conjugated linoleic acid (CLA) refers to geometric and positional isomers of linoleic acid. Animal studies have shown that CLA modulates the immune system and suggest that it may have a therapeutic role in inflammatory disorders. This double-blind placebo-controlled intervention trial investigated the effects of CLA supplementation on indices of immunity relating to cardiovascular disease (CVD) in a cohort of healthy middle-aged male volunteers. Subjects were randomly assigned to supplement their diet with 2.2 g 50:50 isomeric blend of cis 9, trans 11 (c9, t11)-CLA and trans 10, cis 12 (t10, c12)-CLA or placebo daily for 8 weeks. Interleukin (IL) 2, IL-10 and tumour necrosis factor (TNF) alpha were measured in the supernatant of cultured unstimulated and concanavalin A (Con A)-stimulated peripheral blood mononuclear cells (PBMC) by ELISA. Serum IL-6 and plasma CRP were measured by ELISA and plasma fibrinogen by automated clotting assay. Gene expression was investigated by real-time RT-PCR. CLA supplementation significantly reduced Con A-stimulated PBMC IL-2 secretion (37.1%; P=.02). CLA supplementation had no significant effect on transcription of IL-2. CLA supplementation had no direct significant effects on PBMC TNFalpha or IL-10 secretion. Other inflammatory markers associated with CVD, including IL-6, CRP and fibrinogen, were not affected by CLA supplementation. This study showed that CLA supplementation reduced PBMC IL-2 secretion from Con A-stimulated PBMC but lacked effect on other markers of the human inflammatory response.

Nutrients intake and the risk of hepatocellular carcinoma in Italy

Although hepatitis C and B viruses and alcohol consumption are the major risk factors for hepatocellular carcinoma (HCC), dietary habits may also be relevant. A hospital-based case-control study was conducted in Italy in 1999-2002, including 185 HCC cases and 412 cancer-free controls. Dietary habits were assessed using a validated food-frequency questionnaire to compute nutrient intakes. Odds ratios (OR) and corresponding confidence intervals (CI) were calculated using the energy-adjusted residual models. Inverse association emerged for linoleic acid (OR=0.35 for highest versus lowest tertile; 95% CI: 0.18-0.69) and, possibly, beta-carotene (OR=0.48; 95% CI: 0.24-0.93). Among minerals, iron intake was associated with increased HCC risk (OR=3.00; 95% CI: 1.25-7.23), but the association was considerably reduced when iron from wine was excluded (OR=1.61; 95% CI: 0.78-3.30). In conclusion, a diet rich in linoleic acid containing foods (e.g. white meats and fish) and beta-carotene was inversely related to HCC risk.

Functional effects of eggs, naturally enriched with conjugated linoleic acid, on the blood lipid profile, development of atherosclerosis and composition of atherosclerotic plaque in apolipoprotein E and low-density lipoprotein receptor double-knockout mice (apoE/LDLR− / − )

The objective of this study was to evaluate potential anti-atherogenic properties of hen eggs enriched naturally with conjugated linoleic acid (CLA) isomers (cis-9,trans-11 andtrans-10,cis-12). Eighteen apoE and LDL receptor double-knockout mice (apoE/LDLR− / − ), at the age of 4 months with pre-established atherosclerosis, were randomly assigned to three experimental groups (n6) and fed AIN-93G-based diets for the next 2 months. The experimental diets were: AIN-93G+ CLA-free egg-yolk powder (control); AIN-93G+ CLA-free egg-yolk powder +0·1 % CLA (CLA-supplemented eggs); and AIN-93G+ CLA-enriched egg-yolk powder, providing 0·1 % CLA (CLA-enriched eggs). For assessment of anti-atherogenic properties of CLA-enriched or CLA-supplemented eggs the following criteria were used: (1) serum lipid profile; (2) development of atherosclerosis; and (3) composition of atherosclerotic plaque. CLA-enriched eggs, compared with CLA-supplemented eggs, reduced significantly (P < 0·05) total plasma cholesterol in the mice. At the same time, both CLA-supplemented eggs and CLA-enriched eggs tended to decrease the size of atherosclerotic plaque in aortic roots of mice. Most importantly, atherosclerotic plaques of mice fed CLA-enriched eggs showed significantly (P < 0·05) reduced number of atherogenic macrophages and increased area occupied by smooth muscle cells in atherosclerotic lesions. In conclusion, CLA-enriched eggs exerted an anti-inflammatory effect more effectively than CLA-supplemented eggs. This anti-inflammatory effect can be considered their major functional claim that warrants further exploitation.

(n-6) PUFA increase and dairy foods decrease prostate cancer risk in heavy smokers

Previous studies offer suggestive, but not definitive, evidence that total fat or specific fats may increase prostate cancer risk. This study investigates associations of dietary fat, meat, and dairy foods with prostate cancer risk among 12,025 men in the Carotene and Retinol Efficacy Trial (CARET). After 11 y of follow-up, 890 incident prostate cancers were reported and confirmed. Diet was assessed by a biannual FFQ. Cox proportional hazards models were used to estimate multivariate-adjusted hazard ratios (HR) of intake of fat and fat-related foods (meat and dairy) with prostate cancer incidence. Multiplicative interaction terms tested whether associations differed by family history, race, or smoking. Overall, fat was not associated with total, nonaggressive or aggressive prostate cancer. In subgroup analyses the HR for men with a family history of prostate cancer were 2.47 (95%CI = 0.96-6.37) and 2.61 (95% CI = 1.01-6.72) for total polyunsaturated fat (PUFA) and (n-6) PUFA for the 4th vs. 1st quartiles of intake, respectively. Red meat was not associated with total or aggressive prostate cancer. However, higher dairy intake had a statistically significant reduced risk of aggressive prostate cancer than lower dairy intake (HR = 0.59, 95% CI = 0.40-0.85). Dairy foods also protected current, but not former, smokers against aggressive cancer (HR = 0.42, 95% CI = 0.25-0.70). Our findings suggest that associations of dietary fat with prostate cancer risk may vary by type of fat or fat-containing food, and that risk may vary by host factors, including family history and smoking.

Phase 2 enzyme induction by conjugated linoleic acid improves lupus-associated oxidative stress

Conjugated linoleic acid (CLA) exhibits anticancer and anti-inflammatory properties. Its ability to increase total GSH (GSH+GSSG) amount and gamma-glutamylcysteine ligase (gammaGCL) protein expression was recently associated with the inhibition of typical pathological signs in MRL/MpJ-Fas(lpr) mice (MRL/lpr). In the present study the ability of CLA to modulate oxidative stress and phase 2 enzyme activity in the same animal model was investigated. Disease severity was associated with age-dependent production of anti-double-stranded DNA antibodies (anti-dsDNA IgGs) and with enhanced extent of oxidative stress markers: reduced total GSH, increased protein 3-nitrotyrosines (3-NT), and protein-bound carbonyl (PC) amounts. To examine the effect of CLA on antioxidant status, CLA or olive oil (as control) was administered to pregnant MRL/lpr mice. Significantly higher total GSH and Trolox equivalent antioxidant capacity (TEAC) levels were measured in serum of CLA-treated dams (and their pups), as compared with controls. Finally, the antioxidant and chemopreventive properties of CLA were investigated in old MRL/lpr mice. Sera of CLA-treated mice contained higher concentrations of total GSH which were negatively correlated with the levels of oxidative stress markers. Moreover, increased GSH, gammaGCL, glutathione S-transferase (GSTs), and NAD(P)H:quinone oxidoreductase (NQO1) activities were measured in liver and spleen of CLA-treated animals. In conclusion our data indicate that the activation of detoxifying enzymes may be one of the mechanisms whereby dietary CLA down-regulates oxidative stress in MRL/lpr mice.

A mechanistic approach to understanding conjugated linoleic acid's role in inflammation using murine models of rheumatoid arthritis

A naturally occurring fatty acid, conjugated linoleic acid (CLA), reduces immune-induced TNF and inducible cyclooxygenase (COX-2) expression; key mediators of inflammation in rheumatoid arthritis (RA). On the basis of previous work, it was hypothesized that dietary CLA would act as an anti-inflammatory agent in select animal models of RA. In the collagen antibody-induced arthritis (CAIA) model, mice fed CLA (mixed isomers of c9, t11, and t10, c12-CLA) for 3 wk before anticollagen antibody injection had reduced lipopolysaccharide-induced plasma TNF levels and had arthritic scores that were 60% of mice fed corn oil (CO). In the collagen-induced arthritis (CIA) model, mice fed mixed isomers of CLA for 21 days before immunization had lower IgG(1) titers, earlier signs of joint inflammation, but similar arthritis scores compared with CO fed mice during the remaining 70-day post-injection period. Beginning on day 80 to 133, CLA-fed mice had arthritic scores 70% that of the CO-fed mice. In a second CIA experiment, CLA was fed only after the booster injection. Plasma IgG(1) levels were not reduced and arthritis onset was delayed 4 days in CLA-fed mice compared with the CO-fed mice. Peak arthritis score was similar between CLA and CO-fed mice from day 35 to 56. Because CLA reduced inflammation in the CAIA model, delayed onset of arthritis in the CIA model (CIA experiment 2) and reduced arthritis score after day 80 in the CIA model (CIA experiment 1), we concluded that dietary CLA exhibited anti-inflammatory activity that was dependent on antibody.

Eicosapentaenoic acid and 3,10 dithia stearic acid inhibit the desaturation oftrans-vaccenic acid intocis-9,trans-11-conjugated linoleic acid through different pathways in Caco-2 and T84 cells

Stearoyl-CoA desaturase (SCD) is a key enzyme that determines the composition and metabolic fate of ingested fatty acids, in particular the conversion oftrans-vaccenic acid (TVA) to conjugated linoleic acid (CLA). The present study addressed the hypothesis that intestinal TVA absorption and biotransformation into CLA can be modulated by EPA and 3,10-dithia stearic acid (DSA) via altered SCD mRNA levels and desaturation indices (cis-9,trans-11-CLA:TVA and oleic acid:stearic acid ratios) in Caco-2 and T84 cells, two well-establishedin vitromodels of the human intestinal epithelium. The study determined the effect of acute (3h with 0·3mm-EPA or 0·3mm-DSA) and acute-on-chronic (1 week with 0·03mm-EPA or -DSA, followed by respectively, 0·3mm-EPA or -DSA for 3h) treatments. In both cell lines, acute EPA treatment did not alter SCD desaturation indices, whereas the acute-on-chronic treatment affected these surrogate markers of SCD activity. This was associated with reduced sterol regulatory-element binding protein-1c and SCD mRNA levels. In contrast, acute and acute-on-chronic DSA treatments significantly reduced SCD desaturation indices without affecting SCD mRNA levels in Caco-2 cells. The present study on intestinal cells shows that the conversion rate of TVA to c9, t11-CLA is affected by other fatty acids present in the diet such as EPA, confirming previous observations in hepatic and mammary cell models.