Levels of omega 3 fatty acids, vitamin D, dioxins and dioxin-like PCBs in oily fish; a new perspective on the reporting of nutrient and contaminant data for risk-benefit assessments of oily seafood.

Oily seafood is an important food source which contains several key nutrients beneficial for human health. On the other hand, oily seafood also contains persistent organic pollutants (POPs), including the dioxin-like compounds (DLCs) polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/Fs) and dioxin-like-polychlorinated biphenyls (dl-PCBs), potentially detrimental to human health. For a comprehensive comparison of the beneficial and potentially adverse health effects of seafood consumption, risk-benefit analyses are necessary. Risk-benefit analyses require reliable quantitative data and sound knowledge of uncertainties and potential biases. Our dataset comprised more than 4000 analyses of DLCs and more than 1000 analyses each of docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and vitamin D in the three most important Norwegian commercial oily seafood species: Atlantic herring (Clupea harengus), Atlantic mackerel (Scomber scombrus) and farmed Atlantic salmon (Salmo salar). The levels of several DLC congeners were below the limit of quantification (LOQ), making estimation of true levels challenging. We demonstrate that the use of upper bound substitution of censored data will overestimate, while lower bound substitution will underestimate the actual levels of DLCs. Therefore, we implement an alternative robust statistical method by combining Maximum Likelihood Estimation, Regression on Order Statistics and Kaplan-Meier analyses, which is better suited for providing estimations of levels of these contaminants in seafood. Moreover, we illustrate the impact of the toxic equivalency factor (TEF) system on estimation of the sums of DLCs by comparing the TEF system to an alternative system of relative effect potency (REP) factors (Consensus Toxicity Factors). The levels of nutrients and contaminants were related to adequate intake (AI) and tolerable weekly intake (TWI), respectively. We used AI and the TWI values established by the European Food Safety Authority (EFSA). The benefit and the risk were further viewed in the context of the Norwegian average intake of oily fish, and the Norwegian governmental official dietary recommendations of oily fish. Our results showed that both benefit and risk are met at the levels found of nutrients and DLCs in oily seafood. The comprehensive quantitative data presented here will be a key for future risk-benefit assessment of oily fish consumption. Together, our results underline that a refined formalized integrative risk-benefit assessment of oily fish in the diet is warranted, and that the data and methodology presented in this study are highly relevant for future integrated and multidisciplinary assessment of both risks and benefits of seafood consumption for human health.

Long-term effect of tetradecylthioacetic acid: a study on plasma lipid profile and fatty acid composition and oxidation in different rat organs.

Administration of tetradecylthioacetic acid (a 3-thia fatty acid) increases mitochondrial and peroxisomal beta-oxidative capacity and carnitine palmitoyltransferase activity, but reduces free fatty acid and triacylglycerol levels in plasma compared to palmitic acid-treated rats and controls. The decrease in plasma triacylglycerol was accompanied by a reduction (56%) in VLDL-triacylglycerol. Prolonged supplementation of tetradecylthioacetic acid caused a significant increase in lipogenic enzyme activities (ATP-citrate lyase and acetyl-CoA carboxylase) and diacylglycerol acyltansferase, but did not affect phosphatidate phosphohydrolase. Plasma cholesterol, LDL- and HDL-cholesterol levels were reduced. 3-Hydroxy-3-methylglutaryl-coenzyme A reductase activity was, however, stimulated in 3-thia fatty acid-treated rats compared to controls. In addition. the mRNAs of 3-hydroxy-3-methylglutaryl-coenzyme A reductase and LDL-receptor were increased. Tetradecylthioacetic acid administration affected the fatty acid composition in plasma and liver by increasing the amount of monoenes, especially 18:1(n-9), mostly at the expense of omega-3 fatty acids. Compared to liver a large amount of tetradecylthioacetic acid accumulated in the heart, and this accumulation was accompanied by an increase in omega-3 fatty acids, particularly 22:6(n-3) and a decrease in omega-6 fatty acids, mainly 20:4(n-6). The results show that the hypolipidemic effect of tetradecylthioacetic acid is sustained after prolonged administration and may, at least in part, be due to increased fatty acid oxidation and upregulated LDL-receptor gene expression. The increase in lipogenic enzyme activities as well as increased 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity, may be compensatory mechanisms to maintain cellular integrity. Decreased level of 20:4(n-6) combined with increased omega-3/omega-6 ratio in cardiac tissue after tetradecylthioacetic acid treatment may have influence on membrane dynamics and function.

Methylated eicosapentaenoic acid and tetradecylthioacetic acid: effects on fatty acid metabolism.

We introduced methyl or ethyl groups to the 2- or 3-position of the eicosapentaenoic acid (EPA) molecule to investigate whether the branching of EPA could influence its hypolipidemic effect in rats. The most effective branching involved two methyl groups in the 2-position and one methyl group in the 3-position. These EPA derivatives increased hepatic mitochondrial and peroxisomal beta-oxidation and decreased plasma lipids concomitant with suppressed acetyl-coenzyme A (CoA) carboxylase (EC 6.4.1.2) and fatty acid synthase (EC 2.3.1.85) activities. This was followed by elevated activities of camitine O-palmitoyltransferase (EC 2.3.1.21) and possibly 2,4-dienoyl-CoA reductase (EC 1.3.1.34), as well as induced mRNA levels of these enzymes and fatty acyl-CoA oxidase. The fatty acid composition in liver changed, with an increased 18:1 n-9 content, whereas the expression of delta9-desaturase remained unchanged. We investigated the flux of fatty acids in cultured hepatocytes, and found that oxidation of [1-14C]-labeled palmitic acid increased but the secretion of palmitic acid-labeled triglycerides decreased after addition of 2-methyl-EPA. The fatty acyl-CoA oxidase (EC 1.3.3.6) activity in these cells remained unchanged. A significant negative correlation was obtained between palmitic acid oxidation and palmitic acid-labeled synthesized triglycerides. To investigate whether the hypolipidemic effect occurred independently of induced peroxisomal beta-oxidation, we fed rats 2-methyl-tetradecylthioacetic acid. This compound increased the peroxisomal but not the mitochondrial beta-oxidation, and the plasma lipid levels were unchanged. In conclusion, EPA methylated in the 2- or 3-position renders it more potent as a hypolipidemic agent. Furthermore, this study supports the hypothesis that the mitochondrion is the primary site for the hypolipidemic effect.

Lipid metabolism and tissue composition in Atlantic salmon (Salmo salar L.)--effects of capelin oil, palm oil, and oleic acid-enriched sunflower oil as dietary lipid sources.

Triplicate groups of Atlantic salmon (Salmo salar L.) were fed four diets containing different oils as the sole lipid source, i.e., capelin oil, oleic acid-enriched sunflower oil, a 1:1 (w/w) mixture of capelin oil and oleic acid-enriched sunflower oil, and palm oil (PO). The beta-oxidation capacity, protein utilization, digestibility of dietary fatty acids and fatty acid composition of lipoproteins, plasma, liver, belly flap, red and white muscle were measured. Further, the lipid class and protein levels in the lipoproteins were analyzed. The different dietary fatty acid compositions did not significantly affect protein utilization or beta-oxidation capacity in red muscle. The levels of total cholesterol, triacylglycerols, and protein in very low density lipoprotein (VLDL), low density lipoprotein (LDL), high density lipoprotein (HDL), and plasma were not significantly affected by the dietary fatty acids. VLDL, LDL, and HDL fatty acid compositions were decreasingly affected by dietary fatty acid composition. Dietary fatty acid composition significantly affected both the relative fatty acid composition and the amount of fatty acids (mg fatty acid per g tissue, wet weight) in belly flap, liver, red and white muscle. Apparent digestibility of the fatty acids, measured by adding yttrium oxide as inert marker, was significantly lower in fish fed the PO diet compared to the other three diets.

Chronic administration of eicosapentaenoic acid and docosahexaenoic acid as ethyl esters reduced plasma cholesterol and changed the fatty acid composition in rat blood and organs.

Fish oils rich in n-3 fatty acids have been shown to decrease plasma lipid levels, but the underlying mechanism has not yet been elucidated. This investigation was performed in order to further clarify the effects of purified ethyl esters of eicosapentaenoic acid (EPA-EE) and docosahexaenoic acid (DHA-EE) on lipid metabolism in rats. The animals were fed EPA-EE, DHA-EE, palmitic acid, or corn oil (1 g/kg/d) by orogastric intubation along with a chow background diet for three months. At the end the animals were sacrificed. Plasma and liver lipids were measured, as well as lipid-related enzyme activities and mRNA levels. The fatty acid composition of plasma and different tissues was also determined. This study shows that, compared to the corn oil control, EPA-EE and DHA-EE lowered plasma cholesterol level, whereas only EPA-EE lowered the amount of plasma triacylglycerol. In liver peroxisomes, both EE preparations increased fatty acyl-CoA oxidase FAO activities, and neither altered 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase activities. In liver microsomes, EPA-EE raised HMG-CoA reductase and acyl-CoAicholesterol acyltransferase activities, whereas DHA-EE lowered the former and did not affect the latter. Neither product altered mRNA levels for HMG-CoA reductase, low density lipoprotein-receptor, or low density lipoprotein-receptor related protein. EPA-EE lowered plasma triacylglycerol, reflecting lowered very low density lipoprotein secretion, thus the cholesterol lowering effect in EPA-EE-treated rats may be secondary to the hypotriacylglycerolemic effect. An inhibition of HMG-CoA reductase activity in DHA-EE treated rats may contribute to the hypocholesterolemic effect. The present study reports that 20:5n-3, and not 22:6n-3, is the fatty acid primarily responsible for the triacylglycerol lowering effect of fish oil. Finally, 20:5n-3 was not converted to 22:6n-3, whereas retroconversion of 22:6n-3 to 20:5n-3 was observed.

Carnitine palmitoyltransferase I, carnitine palmitoyltransferase II, and acyl-CoA oxidase activities in Atlantic salmon (Salmo salar).

Salmon farmers are currently using high-energy feeds containing up to 35% fat; the fish's capability of fully utilizing these high-energy feeds has received little attention. Carnitine is an essential component in the process of mitochondrial fatty acid oxidation and, with the cooperation of two carnitine palmitoyltransferases (CPT-I and CPT-II) and a carnitine acylcarnitine transporter across the inner mitochondrial membrane, acts as a carrier for acyl groups into the mitochondrial matrix where beta-oxidation occurs. However, no reports are available differentiating between CPT-I and CPT-II activities in fish. In order to investigate the potential for fatty acid catabolism, the activities of key enzymes involved in fatty acid oxidation were determined in different tissues from farmed Atlantic salmon (Salmo salar), i.e., acyl-CoA oxidase (ACO) and CPT-I and CPT-II. Malonyl-CoA was a potent inhibitor of CPT-I activity not only in red muscle but also in liver, white muscle, and heart. By expressing the enzyme activities per wet tissue, the CPT-I activity of white muscle equaled that of the red muscle, both being >> liver. CPT-II dominated in red muscle whereas the liver and white muscle activities were comparable. ACO activity was high in the liver regardless of how the data were calculated. Based on the CPT-II activity and total palmitoyl-L-carnitine oxidation in white muscle, the white muscle might have a profound role in the overall fatty acid oxidation capacity in fish.

Dietary intake of differently fed salmon: a preliminary study on contaminants.

BACKGROUND: In a previous study, a group of coronary heart disease (CHD) patients exhibited positive cardioprotective effects of fatty acids derived from a diet of farmed Atlantic salmon fed fish oil (Seierstad et al. 2005). This follow-up study examines these patients for plasma exposure to selected organic and inorganic contaminants found in seafood that may detract from the benefits of eating oily fish. METHODS: The study design was from Seierstad et al. (2005), where 58 patients were allocated into three groups consuming 700 g week(-1) of differently fed Atlantic salmon (Salmo salar) fillets for 6 weeks: 100% fish oil (FO), 100% rapeseed oil (RO), or 50% of each (FO/RO). RESULTS: Different fillets showed graded levels (FO > FO/RO > RO) of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), dioxin-like polychlorinated biphenyls (DLPCBs), indicator PCBs, polybrominated diphenyl ethers (PBDEs), and arsenic (As). Mercury (Hg) and lead (Pb) levels were similar across the three types of fillets. After 6 weeks of consumption, patient levels of PCDDs, DLPCBs, and PCBs in plasma decreased as the dietary intake of these contaminants increased. Plasma PBDEs only showed increases for the FO patients. Levels of inorganic contaminants in plasma showed only slight changes over the study period. CONCLUSIONS: These results show a reduction in the use of marine oils in fish feed reduces organic contaminant levels in farmed salmon while still providing a good dietary source of marine fatty acids.

Influence of dietary lipid composition on cardiac pathology in farmed Atlantic salmon, Salmo salar L.

The present study investigated the short-term (5 months) effect of replacing dietary marine oils with vegetable oils on the development of arteriosclerotic changes in the heart of Atlantic salmon, Salmo salar. The experiment was performed as a randomized observer-blinded and controlled trial. Farmed Atlantic salmon were randomly sampled from a study population containing 900 individuals. The salmon were divided into three groups and given diets with either 100% fish oil (Diet 1), a 50/50% mixture of fish oil and rapeseed oil (Diet 2) or 100% rapeseed oil (Diet 3). Ten sexually immature salmon from each dietary group were sampled in March and August 2002. Additionally, 47 sexually mature wild salmon were randomly collected in mid-September 2001. Serial histological sections were taken from the bulbus arteriosus and ventricle wall for histopathological evaluation of the coronary arteries and myocardium. No significant differences in mean coronary changes recorded by the main variable 'mean range lesion' (MRL) were detected between the groups in March or August. MRL increased significantly between March and August with Diet 2 (P < 0.01), was nearly significant with Diet 3 (P = 0.06) and was unchanged with Diet 1. This pattern coincided with the Diet 2 group having the highest increase in heart weight. MHC class II immunoreactive cells in the coronary changes were detected in sections from one individual in each group. Heart weight was the most dominant variable in the data set and explained linearly 15.5% of the variation in MRL. Body weight, fish length and heart weight were all significantly, positively and linearly correlated to MRL. The Diet 2 group had the highest growth rate and also exhibited a significant increase in MRL. The possible influence of diet composition on weight gain and MRL needs to be further elucidated. Increase in heart weight seems to be the dominating predictor of the appearance of MRL in Atlantic salmon. However, the present results cannot exclude the possibility that differences in fatty acid composition of fish feed can influence the development of arteriosclerotic changes in Atlantic salmon.

Dietary intake of differently fed salmon; the influence on markers of human atherosclerosis.

BACKGROUND: Cardioprotective effects of omega-3 polyunsaturated fatty acids (n-3 PUFAs) of marine origin are well recognized. Because of the shortness of marine resources vegetable oils are increasingly used in fish farming. The effects on human health of fish fed on vegetable oils are largely unknown. METHODS: In a double-blinded intervention study, 60 patients with coronary heart disease (CHD) were randomly allocated to three groups consuming approximately 700 g per week for 6 weeks of differently fed Atlantic salmon: 100% fish oil (FO), 100% rapeseed oil (RO) or 50% of each (FO/RO), resulting in fillets with high, intermediate and low levels of marine n-3 PUFAs. Patient analyses before and after the intervention period included serum fatty acid profile, serum lipoproteins, and markers of vascular inflammation. RESULTS: The serum fatty acid profiles of the patients after the intervention mirrored those of the corresponding salmon fillets and the respective salmon feeds. Significant differences between the groups were obtained, especially for the levels of total n-3 PUFAs and the n-3/n-6 FA ratio, which were markedly increased in the FO group in contrast to the two other groups (P < 0.02 for all). Additionally, significant reductions of serum triglycerides and of vascular cell adhesion molecule-1 and interleukin-6 were obtained in patients receiving the FO diet when compared with the two other groups (P < 0.05 for all). CONCLUSIONS: Tailor-made Atlantic salmon fillets very high in n-3 PUFAs of marine origin seem to impose favourable biochemical changes in patients with CHD when compared with ingestion of fillets with intermediate and low levels of marine n-3 PUFAs, when replaced by rapeseed oil.

Tetradecylthioacetic acid reduces the amount of lipid droplets, induces megamitochondria formation and increases the fatty acid oxidation in rat heart.

The effects of prolonged administration (3 months) of a 3-thia fatty acid analogue and omega-3-fatty acids on cardiac fatty acid oxidation and the volume fraction of lipid droplets and mitochondria in cardiomyocytes were investigated. Doses were 1 g/day/kg body weight, except 150 mg/day/kg body weight for tetradecylthioacetic acid (a 3-thia fatty acid). One group served as control and did not receive any treatment. The volume fraction of lipid droplets in cardiomyocytes was significantly lower in the tetradecylthioacetic acid group compared to the other groups. Mitochondrial beta-oxidation was 60% greater and fatty acyl-CoA oxidase activity was increased by 430% in the tetradecylthioacetic acid group compared to control. This was accompanied by a greater volume fraction of mitochondria in cardiomyocytes (0.514 +/- 0.032% in tetradecylthioacetic acid v 0.318 +/- 0.007% in control) which was due to an increased size of mitochondria. The volume fraction of mitochondria was also greater in eicosapentaenoic acid (EPA) treated rats compared to control, but the enzymic activities were unaffected. Docosahexaenoic acid (DHA) treatment resulted in a greater volume fraction of lipid droplets in the cardiomyocytes, but the volume fraction of mitochondria and enzyme activities were unaltered. These results indicate that EPA and DHA have different effects on the modulation of mitochondrial biogenesis. Tetradecylthioacetic acid treatment results in megamitochondria formation and increased peroxisomal and mitochondrial beta-oxidation with a concomitant reduction of lipid droplets in the cardiomyocytes.

Up-regulated delta 9-desaturase gene expression by hypolipidemic peroxisome-proliferating fatty acids results in increased oleic acid content in liver and VLDL: accumulation of a delta 9-desaturated metabolite of tetradecylthioacetic acid.

In the liver of rats, monocarboxylic 3-thia fatty acids, tridecylthioacetic acid (C13-S-acetic acid) and tetradecylthioacetic acid (C14-S-acetic acid), increase the mRNA levels of delta 9-desaturase both in a time- and dose-dependent manner. The increased delta 9-desaturase mRNA levels were accompanied by increased delta 9-desaturase activity and increased amounts of oleic acid (18:1 n-9) and delta 9-desaturated C14-S-acetic acid. delta 9-Desaturated C14-S-acetic acid was only detected in phospholipid and cholesterolester species after C14-S-acetic acid treatment. In contrast, C14-S-acetic acid was detected in all the different hepatic lipid fractions, but mainly in the phospholipids. Moreover, C13-S-acetic acid and C14-S-acetic acid were detected in both liver and very low density lipoprotein (VLDL). No delta 9-desaturated 3-thia fatty acid products, however, were found in VLDL. Administration of mono- and dicarboxylic 3-thia fatty acids to rats induced liver expression of the fatty acyl-CoA oxidase gene. After 1 week of C14-S-acetic acid treatment, the levels of fatty acyl-CoA oxidase mRNA increased 5-fold, whereas the delta 9-desaturase mRNA was increased about 1.8-fold. Both fatty acyl-CoA oxidase and delta 9-desaturase mRNA increased about 8-fold after 12 weeks of treatment with C14-S-acetic acid. In conclusion, this study demonstrates that C14-S-acetic acid increases rat delta 9-desaturase gene expression and activity and that changes in hepatic lipids, e.g., 18:1 n-9, are reflected in the VLDL. The peroxisome-proliferating monocarboxylic thia fatty acids are good substrates for desaturases, as delta 9-desaturated metabolites of monocarboxylated thia acids were formed in the liver. Modification of delta 9-desaturation, however, appears not to be related to peroxisome proliferation.

On the effects of thia fatty acid analogues on hydrolases involved in the degradation of metabolisable and non-metabolisable acyl-CoA esters.

1. We investigated the nature and roles of various xenobiotic acyl-CoA hydrolases in liver subcellular fractions from rat treated with sulphur-substituted (thia) fatty acids. To contribute to our understanding of factors influencing enzymes involved in the degradation of activated fatty acids, the effects on these activities of the oppositely acting thia fatty acid analogues, the peroxisome proliferating 3-thia fatty acids (tetradecylthioacetic acid and 3-dithiacarboxylic acid), which are blocked for beta-oxidation, and a non-peroxisome-proliferating 4-thia fatty acid (tetradecylthiopropionic acid), which undergoes one cycle of beta-oxidation, were studied. 2. The hepatic subcellular distributions of palmitoyl-CoA, tetradecylthioacetyl-CoA and tetradecylthiopropionyl-CoA hydrolase activities were similar to each other in the control and 3-thia fatty acid-treated rat. In control animals, most of these hydrolases were located in the microsomal fraction, but after treatment with the 3-thia fatty acids, the specific activities of the mitochondrial, peroxisomal, and cytosolic palmitoyl-CoA, tetradecylthioacetyl-CoA, and tetradecylthiopropionyl-CoA hydrolase activities were significantly increased. This increase in activity was seen mostly for the enzymes using tetradecylthiopropionyl-CoA and tetradecylthioacetyl-CoA as substrates. The increased mitochondrial activities for these two substrates were seen already after 1 day of treatment, whereas the peroxisomal activities increased after 3 days. No stimulation was seen after treatment with the 4-thia fatty acid analogue, tetradecylthiopropionic acid, but a decrease in peroxisomal hydrolase activities for all three substrates was observed. 3. The cellular distributions of clofibroyl-CoA, POCA-CoA, and sebacoyl-CoA hydrolase activities were different from those of the 'long-chain acyl-CoA' hydrolases mentioned above both in the normal and 3-thia fatty acid treated rat. This group of hydrolases was found in the mitochondrial, peroxisomal, and cytosolic fractions. 3-Thia fatty acid treatment increased the activities of clofibroyl-CoA and sebacoyl-CoA hydrolases in all three fractions. Clofibroyl-CoA and sebacoyl-CoA hydrolase activities were increased after 1 day of treatment. Only the cytosolic POCA-CoA hydrolase was stimulated after 3-thia fatty acid treatment after only 1 day of treatment, whereas treatment with the 4-thia fatty acid led to an increase of enzyme activity in the mitochondrial and peroxisomal fractions. 4. Based on the subcellular distributions and specific activities, we suggest that several enzymes exist which may act as regulators of intracellular acyl-CoA levels.

Peroxisomal fatty acid oxidation capacity is more resistant to ischaemic and reperfusion injury than mitochondrial fatty acid oxidation capacity in feline hearts.

We investigated ischaemic and postischaemic mitochondrial and peroxisomal fatty acid oxidation capacity, ATP levels and regional function in 40 anaesthetized open chest cats subjected to 10 or 40 min of regional myocardial ischaemia with or without 3 h of reperfusion (n = 10 in each situation). Following 10 min of ischaemia, the mitochondrial fatty acid oxidation capacity measured in tissue extracts from ischaemic tissue (nmol min-1 mg protein-1) was reduced in both subepi- and subendocardium, but was normalized in reperfused tissue extracts from both wall layers (0.29 +/- 0.03 and 0.30 +/- 0.04 vs. 0.57 +/- 0.05 and 0.59 +/- 0.05. P < 0.05). Peroxisomal fatty acid oxidation capacity in tissue extracts was unaffected by ischaemia and reperfusion. ATP levels and regional function measured in the LAD region was partly restored transmurally. After 40 min of LAD occlusion, mitochondrial fatty acid oxidation capacity was reduced, with higher activity in subepi- than in subendocardium (0.27 +/- 0.05 vs. 0.19 +/- 0.04. P < 0.05). Reperfusion did not restore mitochondrial fatty acid oxidation capacity. Peroxisomal fatty acid oxidation capacity was increased in the ischaemic subendocardium compared with levels in non-ischaemic subendocardium (0.53 +/- 0.02 vs. 0.45 +/- 0.03, P < 0.05), with normalization at the end of reperfusion. ATP levels were non-uniformly reduced during ischaemia and not repleted during reperfusion. Regional function recovered in circumferential segments but not in longitudinal segments following 40 min of ischaemia. In conclusion fatty acid oxidation enzymes seem to be more resistant to ischaemia in peroxisomes than in mitochondria. Mitochondrial fatty acid oxidation is fully reversible following shortlasting ischaemia, but remains depressed following prolonged ischaemia and reperfusion.

Eicosapentaenoic acid and sulphur substituted fatty acid analogues inhibit the proliferation of human breast cancer cells in culture.

Numerous studies have shown dietary fatty acids to influence the progression of several types of cancers. The purpose of the present investigation was to examine the influence of various types of fatty acids, including omega-3 fatty acids and a new class of hypolipidemic peroxisome proliferating fatty acid analogues, namely the 3-thia fatty acids, on MCF-7 human breast cancer cell growth. 3-thia fatty acids represent non-beta-oxidizable fatty acid analogues in which a sulphur atom substitutes for the beta-methylene group (3-position) in the saturated and unsaturated fatty acids. The effects of increasing concentrations of palmitic acid, tetradecylthioacetic acid (a 3-thia fatty acid), eicosapentaenoic acid, docosahexaenoic acid, and two 3-thia polyunsaturated fatty acids on the proliferation of MCF-7 cells, maintained in serum-free culture, were studied. At the highest concentration of fatty acid used (64 microM) tetradecylthioacetic acid was found to be the most effective of all fatty acids tested in inhibiting cell growth, whilst palmitic acid and docosahexaenoic acid had no significant effect on cell growth. Thus, of the two dietary polyunsaturated omega-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid, only eicosapentaenoic acid possesses an inhibitory effect on the proliferation of MCF-7 cells. In all cases the inhibitory effect of the fatty acid was found to be reversible. Tetradecylthioacetic acid has been shown to be a potent peroxisome proliferator. It was, therefore, hypothesized that tetradecylthioacetic acid may inhibit the human MCF-7 cell growth by increasing the level of oxidative stress within the cell. However, use of agents which modify the cell's protective apparatus against oxidative stress had no influence on the inhibitory effect of tetradecylthioacetic acid. These experiments indicate that tetradecylthioacetic acid inhibits cell growth by mechanisms which may be independent of oxidative status.

Docosahexaenoic and eicosapentaenoic acids are differently metabolized in rat liver during mitochondria and peroxisome proliferation.

The 3-thia fatty acids, tetradecylthioacetic acid and 3,10-dithiadicarboxylic acid are mitochondrion and peroxisome proliferators. Administration of these promotes an increased transport of endogenous fatty acids to these organelles and a higher capacity of beta-oxidation. Administration of 3-thia fatty acids to rats resulted in a significant decrease of the hepatic level of docosahexaenoic acid (DHA) (17-24%) and especially eicosapentaenoic acid (EPA) (40-80%) accompanied by increased gene expression of mitochondrial 2,4-dienoyl-CoA reductase and enoyl-CoA isomerase. The mitochondrial oxidation of EPA was increased more than 4-fold after administration of 3-thia fatty acids. EPA-CoA was a good substrate for mitochondrial carnitine acyltransferase-I and treatment with 3-thia fatty acids increased the activity 1.7-fold. DHA was a poor substrate for both mitochondrial and peroxisomal beta-oxidation. DHA-CoA was a very poor substrate for mitochondrial carnitine acyltransferase-I and -II, and the activity did not increase after treatment. However, the peroxisomal DHA-CoA oxidase increased 10-fold after 3-thia fatty acid treatment, whereas the peroxisomal EPA-CoA oxidase increased only 5-fold. In isolated hepatocytes, 16% of total metabolized EPA was oxidized and 76% was incorporated into glycerolipids, whereas DHA was oxidized very little. We conclude that under conditions of increased mitochondrial and peroxisomal proliferation by 3-thia fatty acids, a relatively higher oxidation rate of polyunsaturated n-3 fatty acids might result in a decreased hepatic level of EPA and DHA. Under these conditions DHA seems to be oxidized by the peroxisomes, whereas EPA, which can be oxidized in both organelles, is mainly oxidized by mitochondria.

Long-term retention of a novel antioxidant sulphur-substituted fatty acid analogue after local delivery in porcine coronary arteries.

OBJECTIVE: Antioxidants have been suggested to reduce restenosis after balloon angioplasty. A novel sulphur-containing fatty acid, tetradecylthioacetic acid (TTA), with antioxidant properties, is efficiently incorporated into cellular phospholipids. We have determined the uptake and retention of TTA after local coronary artery delivery in 20 pigs. DESIGN: Radiolabelled TTA was delivered to 40 main coronary arteries via a multiporous coronary angioplasty balloon catheter inflated before, after, or without overstretch vessel injury. The animals were killed at intervals of up to 6 weeks post-procedure. The radioactivity of the tissue sections was determined as nmol TTA/g tissue. RESULTS: Concentrations of TTA in the coronary arteries were 1.84 +/- 0.45 nmol/g up to 24 h, 1.50 +/- 0.96 nmol/g at 2 weeks, 0.22 +/- 0.11 nmol/g at 4 weeks and a trace was present at 6 weeks (p-value for trend <0.01). The arterial wall uptake at the delivery site was higher than distal to delivery (1.84 +/- 0.37 vs 0.55 +/- 0.13 nmol/g, p = 0.006) and perivascular fat (p < 0.01) but not higher than in the myocardium. Infusion before, after or without vessel injury was not important for tissue concentration. CONCLUSIONS: After local coronary artery delivery, the antioxidant TTA is taken up by the arterial wall in which it is retained for at least 4 weeks.