The effects of coenzyme A and carnitine on steady-state ATP/ADP ratios and the rate of long-chain free fatty acid oxidation in liver mitochondria.

1. Conditions for the optimal coupled oxidation by rat liver mitochondria of long-chain free fatty acids were defined. The fatty acids studied were in the omega9 series: oleic (18 : 1), gondoic (20 : 1) and erucic (22 : 1) acids. Carnitine (about 0.1 mM) maximally stimulated State 3 respiration due to oleic and gondoic acids about three-fold (coenzyme A present), and coenzyme A (10--20 micrometer) stimulated about two-fold (carnitine present). When neither coenzyme A nor carnitine was added, respiration was very slow. 2. When respiration was limited by ADP, concentrations of added CoA only slightly in excess of that required for fatty acid oxidation very significantly decreased the ATP/ADP ratio maintained at a given rate of respiration imposed by externally added ATPase, and increased the level of membrane-associated acyl-CoA. This effect was most pronounced with oleic acid, and least with erucic acid. When excess ADP was present, higher concentrations of added coenzyme A (50--200 micrometer) inhibited to oxidation of oleic acid in a concentration-dependent manner, whereas the oxidation of substrates other than fatty acids was essentially unaffected. 3. It is concluded that, in addition to its requirement for fatty acid oxidation, coenzyme A exerts two independent effects on mitochondrial metabolism as here determined in vitro: (a) under conditions mimicking those in the intact cell with respect to phosphorylation-dependent respiration (ADP limiting), acyl-CoA formed from added coenzyme A and fatty acid inhibits the adenine nucleotide translocase, resulting in a lowering in the extramitochondrial ATP/ADP ratio obtained at any given rate of phosphorylation-limited respiration, and (b) under State 3 conditions (ADP in excess) coenzyme A ( less than 50--200 micrometer) specifically suppresses oxidation of long-chain fatty acids by limiting the rate of formation of intramitochondrial acyl-CoA.

Evidence for a negative modulating effect of erucic acid on the peroxisomal beta-oxidation enzyme system and biogenesis in rat liver.

In male rats fed a 30 cal% high-erucic acid (22:1 (13) (cis] rapeseed oil diet for 4 weeks a transient, small increase in peroxisomal beta-oxidation was observed in liver homogenates and isolated peroxisomes after approximately 1 week. Morphometric analysis revealed a progressive decrease in the average size of the liver peroxisomes (by approx. 20%), as well as their volume fraction (by more than 40%). A negative dose-response was observed when peroxisomal beta-oxidation was determined in animals fed rapeseed oil diets with a variable content of erucic acid. When erucic acid was given as subcutaneous injections the peroxisomal beta-oxidation decreased, in both liver homogenates and isolated peroxisomes. In contrast to recent proposals, our findings indicate that the amount of erucic acid cannot account for the small increase in peroxisomal beta-oxidation observed in the liver of rats adapted to a diet containing 30 cal% rapeseed oil with a high content of this fatty acid. In fact, by the selected criteria erucic acid seems to have a negative modulating effect on both the peroxisomal beta-oxidation enzyme system and biogenesis.

The stimulation of erucate metabolism in isolated rat hepatocytes by rapeseed oil and hydrogenated marine oil-containing diets.

1. The metabolism of palmitate and especially of erucate was studied in hepatocytes isolated from rats fed for 3 weeks a diet containing peanut oil (diet, 1), rapeseed oil (diet 2) and partially hydrogenated marine oil (diet 3). 2. The metabolism of palmitate was not significantly influenced by the diet. The rapeseed oil diet caused 1.4 fold and 1.3 fold increase and marine oil diet 3 fold and 2.2 fold increase in the oxidation and chain-shortening respectively of [14-14C]erucic acid in isolated hepatocytes. 3. Cyanide and antimycin A did not inhibit the chain-shortening of erucate in liver cells of rats fed rapeseed oil and peanut oil. The high capacity of the chain-shortening system in hepatocytes of marine oil-fed rats was partially inhibited. 4. Inhibition of the transfer of fatty acids into the mitochondria by lowering the intracellular carnitine concentration and/or by addition of (+)-decanoyl-carnitine resulted in a very pronounced apparent stimulation of the chain-shortening of erucic acid. It is suggested that the chain-shortening system may be virtually independent of the mitochondria, unless the availability of the extramitochondria NAD+ and/or NADP+ is rate-limiting under conditions of extremely low redox potential of the mitochondria. 5. Feeding marine oil or rapeseed oil to the rats induced a 30% increase in catalase activity, a 25--30% increase in urate oxidase activity and a 50% increase in the total CoA in the liver compared to rats fed peanut oil. 6. It is suggested that the increased metabolism of erucate in hepatocytes of marine oil and rapeseed oil-fed rats may be due to the increase in ther peroxisomal beta-oxidation.

The regulation of fatty acid chain elongation in rat liver microsomes: role of fasting and CoASH.

The elongation system for palmitic acid in rat liver microsomes was decreased to 1/3 by fasting, while the elongation of eicosapentaenoic acid was not sensitive to fasting. The rate of eicosapentaenoic acid elongation in the fed state was 50% higher than using palmitic acid as a substrate. The saturated and polyunsaturated fatty acyl-CoA substrates exhibited positive cooperativity on the rate-limiting condensing step in the elongation system, with a Hill constant of approx. 2. An inhibition by CoASH on the total elongation reaction as well as on the condensation step was demonstrated using acyl-CoA substrates, and followed a hyperbolic pattern. The concentrations giving a 50% inhibition (30-70 microM) were in the range found in rat hepatocyte cytosol, indicating that free CoASH has the potential to act as a physiological regulator.

Effect of dietary n-3 and n-6 fatty acids on fatty acid desaturation in rat liver.

To study the effect of high-fat diets with varying contents of n-3 and n-6 fatty acids on the metabolism of essential fatty acids, the rat liver microsomal fatty acid desaturases were measured. The rats were fed for 3 weeks with diets high in linseed oil (18:3(n-3)), sunflower seed oil (18:2(n-6)) or fish oil (20:5(n-3) and 22:6(n-3)) (20%, w/w) using pellet fed rats as a reference. The delta 6-desaturase using 18:2(n-6) or 18:3(n-3) as substrates was stimulated 1.5-2.5-fold by linseed or sunflower seed oil, compared to the pellet reference. The delta 5-desaturase was stimulated 3.5-fold with linseed oil and 2.5-fold with sunflower seed oil, while the delta 9-desaturase was inhibited by all the high-fat diets. The delta 6-, 5- and 9-desaturase activities were in all cases considerably reduced with fish oil as compared to linseed and sunflower seed oil diets. With pellet fed rats the rates were highest for delta 9-desaturation and in decreasing order lower for delta 5-desaturation, delta 6-desaturation with 18:3 (n-3) as substrate and finally delta 6-Desaturation with 18:2(n-6) as substrate. The content of 20:4(n-6) in liver phospholipids increased with the diets rich in 18:2(n-6), and was reduced for the fish oil diet enriched in 20:5 and 22:6(n-3) fatty acids. The amount of 20:5(n-3) in phospholipids was as high with linseed oil diet as with the fish oil diet, while the 22:6(n-3) content was only increased with the fish oil diet.

Studies on the interrelated stimulation of microsomal omega-oxidation and peroxisomal beta-oxidation in rat liver with a partially hydrogenated fish oil diet.

To investigate the mechanism for initiation of peroxisomal beta-oxidation by high-fat diets the time-courses of peroxisomal beta-oxidation and microsomal omega-oxidation stimulated by 20% (w/w) partially hydrogenated fish oil were studied. The relative stimulation of these two activities developed in a very similar way. We also observed an elevated level of long-chain acyl-CoA with partially hydrogenated fish oil, but not of free fatty acids. There was, however, a significant shift in the composition of free fatty acids to a higher amount of monoenes and lower amounts of 18:2 and 20:4 fatty acids. In peroxisomes purified by Nycodenz gradient centrifugation there was no lauric acid hydroxylation. This study indicates that with partially hydrogenated fish oil we obtain a parallel stimulation of reactions in two different cellular compartments. Dicarboxylic fatty acids, which are products of the omega-oxidation, had only a slight stimulatory effect on peroxisomal beta-oxidation. Therefore, the primary stimulatory agent of peroxisomal beta-oxidation and microsomal omega-oxidation is still unknown. It was speculated that this agent may activate a gene-locus responsible for both reactions.

The effect of high-fat diets on microsomal lauric acid hydroxylation in rat liver.

A diet with 20% (w/w) fish oil or partially hydrogenated fish oil has been shown to stimulate omega-oxidation of lauric acid 2.5-fold with rat liver microsomal preparations after 1 week of feeding. A diet containing either 20% (w/w) soybean oil, partially hydrogenated soybean oil or rapeseed oil had no effect. The omega-oxidation was also stimulated by fasting (3.7-fold) and by clofibrate (13-fold). The stimulation of omega-oxidation with partially hydrogenated fish oil was at its highest level after 3 days of feeding, and was dose dependent in the dietary oil of range 5-25% (w/w). With various high-fat diets, a high correlation was found (r = 0.81) between peroxisomal beta-oxidation of palmitoyl-CoA and microsomal omega-oxidation of lauric acid.

Acyl-CoA synthetase activity of rat liver microsomes. Substrate specificity with special reference to very-long-chain and isomeric fatty acids.

1. A fatty acid-depleted rat liver microsomal fraction has been used for the measurement of acyl-CoA synthetase (acid : CoA ligase (AMP-forming), EC 6.2.1.3) activity. The assay was based on measurement of the reaction product AMP by high-performance liquid chromatography (HPLC). The synthetase activity (V') revealed an optimum at 12 : 0 with saturated fatty acids as substrate, and at 14 : 1 with mono-unsaturated fatty acids. The apparent Michaelis constant, on the other hand, showed no systematic dependence on the fatty acid chain-length. 2. The mono-unsaturated fatty acids from 14 : 1 to 22 : 1 gave higher activities than the corresponding saturated fatty acids, and the relative differences were greatest with the very-long-chain fatty acids eicosaenoic (20 : 1 (11) (cis)) and docosaenoic acid (22 : 1 (11) (cis)). The synthetase activity with saturated and mono-unsaturated fatty acids was found to correlate to their capacity factor (k') on reversed phase chromatography (HPLC). This finding may indicate that the observed chain-length dependence of the activity largely reflects the partition of the fatty acids between a hydrophobic and a hydrophilic phase. In general, the position of the double bond and the cis/trans configuration had little effect on the V' values except for 22 : 1 (11)(cis) which revealed a 2-fold higher activity tha 22 : 1 (13) (cis). 3. The polyunsaturated fatty acid 22 : 6 (all cis) ;was notably found to be a much better substrate than other C22 fatty acids. 4. The present study does not support the idea of more than a single ATP-dependent acyl-CoA synthetase in the rat liver microsomal fraction.

On the mechanism of induction of the enzyme systems for peroxisomal beta-oxidation of fatty acids in rat liver by diets rich in partially hydrogenated fish oil.

In this paper, we describe the early biochemical changes in liver cells that occur in rats fed a semisynthetic diet containing 20% (w/w) partially hydrogenated fish oil. Within hours the level of ornithine decarboxylase (ODC) increased, peaked at about 24 h (11-fold increase) and returned to subnormal levels within 48 h. The diet evoked a similar rapid increase in the cellular level of mRNA for the bifunctional enzyme of peroxisomal beta-oxidation (enoyl-CoA hydratase: beta-hydroxyacyl-CoA dehydrogenase (HD)) (12-fold), followed by increases in the specific content of HD protein (3-fold) and the capacity for beta-oxidation in peroxisomes (5.3-fold). The cellular level of long-chain acyl-CoA increased 2.1-fold. By contrast, no significant changes were observed in the specific activities of ornithine decarboxylase, peroxisomal beta-oxidation activity and microsomal omega-hydroxylation as well as the level of long-chain acyl-CoA in livers of rats fed (1 week) diets containing 20% (w/w) soybean oil with added 3 or 6% (w/w) of either elaidic acid (18:1(11) (trans)), brassidic acid (22:1(13) (trans)) or erucic acid (22:1(13) (cis)). Expression of normal levels of mRNA for the bifunctional enzyme was also found. Morphometric analyses revealed no proliferation of peroxisomes in these fatty acid-supplemented diets, in contrast to that observed with the partially hydrogenated fish oil diet. These results are consistent with the proposal (Flatmark, T., Christiansen, E.N. and Kryvi, H. (1983) Biochim. Biohys. Acta 753, 460-466) that components in dietary oils, different from C22:1 cis and trans fatty acids, are responsible for the pleiotropic responses evoked in target cells. Thus, the pattern of response induced by partially hydrogenated fish oil mimics those induced by xenobiotic compounds collectively termed peroxisome proliferators.

Elongation and desaturation of arachidonic and eicosapentaenoic acids in rat liver. Effect of clofibrate feeding.

The fatty acid elongation-desaturation ability of 5,8,11,14-eicosatetraenoic (20:4(n-6)) and 5,8,11,14,17-eicosapentaenoic (20:5(n-3)) acids was determined in both liver microsomal and light mitochondrial (rich in peroxisomes) fractions of untreated and clofibrate treated rats. The elongation and the subsequent desaturation steps were performed in the corresponding favorable media. 20:5(n-3) elongation was about 2-times more extensive than that of 20:4(n-6). Clofibrate feeding for 10 days resulted in a marked decrease in the elongation rate with the two substrates, while the delta 4 desaturation rate was increased. There were small differences in the elongation rate between the microsomal and light mitochondrial fractions, however, the relative delta 4 desaturation rate was higher in the light mitochondrial fraction than microsomes.

Effects of marine oil diet on peroxisomes and mitochondria of rat liver. A combined biochemical and morphometric study.

Feeding male rats a high cal% partially hydrogenated marine oil diet induced a response in the parenchymal liver cells at the cellular as well as the subcellular level. An adaptation in the lipid metabolism is indicated by an accumulation of triglycerides and a hypertrophy of the liver cells, and a rather selective increase (4.9-fold) in the specific activity of peroxisomal beta-oxidation. In addition, a slight proliferation of peroxisomes was observed; the volume fraction and the total number of peroxisomes increased 1.5-fold. The peroxisomes, however, preserved the biochemical and morphological homogeneity characteristic of peroxisomes in normal controls. At the mitochondrial level, a gradual development of megamitochondria was observed as the principal morphological change, with a 1.6-fold increase in the average size. The functional significance of this change remains to be determined. The effects of a partially hydrogenated marine oil diet on parenchymal liver cells appears to be manifestations with multiple causal factors. The high content of very long-chain trans fatty acids is of particular significance for the peroxisomal changes. An essential fatty acid deficiency, enforced by the presence of trans fatty acids in the diet, is most likely the determining factor for the development of megamitochondria.

Polydispersity of rat liver peroxisomes induced by the hypolipidemic and carcinogenic agent clofibrate.

1. The present study has confirmed that the hypolipidemic and carcinogenic agent clofibrate induces a marked increase in the specific activity of some peroxisomal marker enzymes in rat liver homogenates, notably of the palmitoyl-CoA dependent dehydrogenase and catalase activities. 2. Clofibrate was found to induce a marked polydispersity of the peroxisomes as determined by analytical differential centrifugation of homogenates and morphometric analysis of hepatocytes. 3. Two major populations of peroxisomes were detected by analytical differential centrifugation under conditions which reduce the hydrostatic pressure effects on the organelle to a minimum. Using urate oxidase as the marker enzyme, the S4,B-values of the two populations were estimated to 1 1 860 S and 4240 S, both different from that of the homogenous population of peroxisomes in the control animals (S4,B approximately equal to 6680 S). The 4240 S-population induced by clofibrate revealed a high specific activity relative to that of of urate oxidase and particularly relative to that of catalase, which was very low. In addition, a less distinct population of particles (870 S lees than S lees than 4240 S) contained more than 50% of the total particle-bound palmitoyl-CoA dependent dehydrogenase activity sedimented at a centrifugal effect of t integral of 0 rmp(2)dt = 1.5 x 10(10) min(-1), but not urate oxidase and catalase activities. This fraction was not observed in the homogenates of normal rats. As in the normal controls, the palmitoyl-CoA dependent dehydrogenase activity was found to be particle-bound (S greater than 870 S). 4. Morphometric analyses of randomly selected hepatocytes revealed that after clofibrate treatment the relative volume fraction of the peroxisomes increased by a factor of 5.5 and thier average diameter and volume by a factor of 1.3 and 2.1, respectively. Furthermore, the frequency of electron-dense matrix cores decreased on clofibrate treatment. In contrast, no change was observed in the average size of the mitochondria, and their relative volume fraction increased only by a factor of 1.2. 5. The clofibrate induced changes in eh morphological and biochemical properties of rat liver peroxisomes appears to be a very useful model system in which to study the biogenesis as well as the biochemical and physiological role(s) of this organelle in mammalian cells.

Vitamin E deficiency in phrynoderma cases from Sri Lanka.

Phrynoderma cases were identified in a village close to Colombo in Sri Lanka. The alpha-tocopherol level in plasma was 3.3 +/- 0.6 mumol/L among the phrynoderma patients (n = 11) and 13.0 +/- 2.3 mumol/L among the control subjects (p less than 0.002). A test on glutathione reductase activity in erythrocytes revealed a stronger riboflavin deficiency among patients than among control subjects (p less than 0.005). No significant differences were found between the groups with regard to plasma levels of retinol, retinol-binding protein, vitamin B-12, folic acid, thiamin, selenium, zinc, or essential fatty acid pattern. Primary malnutrition may partly explain the deficiency of alpha-tocopherol and riboflavin observed in phrynoderma cases.

Factor analysis of plasma lipoprotein components.

Serum phospholipids were analyzed for their content of long-chained fatty acids together with other components of lipoproteins (total- and HDL-cholesterol, apolipoproteins A-I and B, triglycerides), in 60 coronary heart disease patients and 30 control individuals. Some of the individual variations in content of the various components showed co-variation with each other. This formed the basis for the extraction of 7 'factors' by the statistical procedure 'factor analysis'. Analysis of variance was performed with the 'factor scores' for subgroups of high and low age and high and low total serum cholesterol. The analysis revealed two unexpected factors which discriminated with statistical significance between young, hypercholesterolaemic patients and controls. One factor was a positive risk factor and the other a negative one. They could possibly be dependent on the existence of two at present uncharacterized subgroups of lipoproteins. These lipoproteins contained, according to the analysis, large amounts of certain fatty acids. It is suggested that fatty acid analysis might be useful in the characterization of lipoproteins that are involved in the development of atherosclerosis.

Effect of 3- and 4-thia-substituted fatty acids on glycerolipid metabolism and mitochondrial beta-oxidation in rat liver.

Treatment of normolipidemic rats by alkylthiopropionic acid (CETTD), resulted in a dose- and time-dependent increase in total dihydroxyacetone phosphate acyltransferase (DHAPAT) activity, in extent comparable to that of 3-thiadicarboxylic acid (BCMTD) and alkylthioacetic acid (CMTTD). Thus, in CETTD- and CMTTD-treated rats, the specific DHAPAT activity increased in the microsomal, peroxisomal and mitochondrial fractions. In contrast, repeated administration of the peroxisome proliferator, BCMTD, decreased the specific DHAPAT activity both in the peroxisomal fraction and in purified peroxisomes. A three-fold increase in specific activity was, however, revealed in the mitochondrial fraction. Whether the variation of the DHAPAT activity in the mitochondrial and microsomal fractions among the feeding groups can be explained by increased number of enlarged and small peroxisomes sedimenting in the fractions, are to be considered. Subcellular fractionation studies confirmed previous findings that rat liver glycerophosphate acyltransferase (GPAT) was located both in mitochondria and the microsomal fraction. BCMTD was considerably more potent than CMTTD in stimulating the microsomal and mitochondrial GPAT activities. Administration of CETTD marginally affected the isoenzymes of GPAT. Diacylglycerol acyltransferase (DGAT) activity was increased by 35% in BCMTD and CMTTD treated rats, but by administration of CETTD the enzyme activity was decreased by more than 80%. The acyl-CoA cholesterol acyltransferase (ACAT) activity was marginally affected in animals treated with BCMTD, CMTTD and CETTD. Thus, the results indicate that the initial steps in the synthesis of triacylglycerols and ether glycerolipids as well as the last step in triacylglycerol synthesis could not be identified as mediating the fat accumulation or the lowering of triacylglycerol content in liver of CETTD, or BCMTD and CMTTD treated rats. On the other hand, CMTTD increased the palmitoyl-CoA oxidation in mitochondria, and CETTD considerably inhibited the activity. Therefore, it is conceivable that the development of fatty liver with CETTD is mostly due to inhibition of mitochondrial beta-oxidation.

Effects of partially hydrogenated fish oil, partially hydrogenated soybean oil and butter on the susceptibility of low density lipoprotein to oxidative modification in men.

OBJECTIVE: To study the effect of partially hydrogenated fish oil (PHFO-diet), partially hydrogenated soybean oil (PHSO-diet) and butterfat (butter-diet) on the susceptibility of low density lipoprotein (LDL) to in vitro oxidative modification. DESIGN: A strictly controlled, randomized, single-blind dietary study with cross-over design. SUBJECTS: Thirty-three healthy men aged from 21 to 46 years entered the study; 29 men completed the study. INTERVENTIONS: Fat provided approximately 35% of the energy intake in all three test diets, and the content of trans-fatty acids was 8.0, 8.5 and 0.9% of energy in the PHFO-, PHSO- and butter-diets, respectively. The subjects consumed all three test diets each during three weeks, in a single-blind, random order. LDL isolated from the participants given the three different diets was subjected to Cu(2+)-induced oxidation. RESULTS: No significant differences were seen on either conjugated dienes, lipid peroxides, uptake by macrophages or relative electrophoretic mobility of LDL. Vitamin E level in serum from subjects on the PHFO-diet was significantly higher compared to the two other diets. Furthermore, no significant differences were found in the composition of the LDL particle between the three diet groups. CONCLUSIONS: Our results indicate that consumption of trans-fatty acids does not alter the susceptibility of LDL to oxidative modification.

The effect of feeding fish oils, vegetable oils and clofibrate on the ketogenesis from long chain fatty acids in hepatocytes.

Groups of rats were fed diets containing 25% fish oil (FO), 25% soybean oil, 25% partially hydrogenated fish oil (PHFO), 25% partially hydrogenated soybean oil (PHSO), 25% partially hydrogenated coconut oil or 0.3% clofibrate for 3 wk. After the animals were fasted for 24 hr, hepatocytes were isolated and ketogenesis from added palmitate, linoleate cis and trans, arachidonate and docosahexaenoate was measured. Ketogenesis after oil feeding was significantly stimulated (two- to threefold) only in cells from the PHFO- and PHSO-fed rats. The stimulation was most apparent with the long chain unsaturated fatty acids as substrates. These fatty acids were relatively poor ketone body precursors in control hepatocytes. Essential fatty acid deficiency did not seem to be the reason for this stimulation. Clofibrate also stimulated ketogenesis significantly (1.5- to 3-fold). The degree of stimulation increased with chain length and degree of unsaturation of the substrate. The activity of the enzyme 2,4-dienoyl-CoA reductase was also studied in the same groups. Its activity was stimulated about fourfold in the clofibrate-treated rats and to a lesser extent by the PHFO, PHSO and FO diets. The activity showed no correlation with the content of unsaturated fatty acids in the diet or their oxidation in isolated hepatocytes. The 2,4-dienoyl-CoA reductase, therefore, does not seem to be a regulatory enzyme in the metabolism of dietary polyunsaturated fatty acids. It is concluded that an induction of the peroxisomal beta-oxidation system most likely is involved in the reported increases in ketogenesis from very long chain polyunsaturated fatty acids.

Long-term effects of high-fat diets on peroxisomal beta-oxidation in male and female rats.

In weanling male rats a 4-fold increase of heart triacylglycerols was observed after three days on a high-fat diet containing partially hydrogenated fish oil (PHFO). In female rats this increase was only about 50%. No significant differences were observed between female and male rats in the fatty acid composition of the accumulated lipids. The initial level of peroxisomal beta-oxidation activity was similar in male and female rats in both liver and heart. After three weeks of receiving high-fat diets, the rats showed a marked increase in peroxisomal beta-oxidation activity with PHFO in the diet and less with soybean oil (SO), confirming previous studies with male rats. Catalase activity was similarly affected in hearts of both sexes. In male rats the levels of peroxisomal beta-oxidation observed after three weeks of feeding on the high-fat diets were found to be maintained, both in liver and heart, during a feeding period of three months. The response to high-fat diets in females, however, seems to be further accentuated after three months of feeding, resulting in a capacity of peroxisomal beta-oxidation in liver of about three times that of the male rats when calculated on a total body-weight basis.

Effect of marine oil and rapeseed oil on composition of fatty acids in lipoprotein triacylglycerols from rat blood plasma and liver perfusate.

The fatty acid patterns of triacylglycerols (TG) from very low density lipoprotein (VLDL) in blood plasma and liver-perfusate from rats fed partially hydrogenated marine oil or rapeseed oil were determined. In the plasma from rats fed rapeseed oil for three days and three weeks, there was a small but significant decrease in the percentage of 22:1 fatty acid from 17.2 to 11.2% with length of feeding. In liver-perfusate, the comparable decrease with dietary rapeseed oil was from 18.5 to 5.2%, and with dietary marine oil from 13.4 to 8.0%. In contrast to the liver-perfusate, the remaining liver had only a very low 22:1 composition (ca 2%) independent of feeding period or diet. The results indicated that the liver exported the very long chain fatty acids and that an adaptation took place after three days feeding with rapeseed oil or marine oil. This adaptation in the liver could possibly explain why TG accumulation in hearts, which appears after three days' feeding with rapeseed oil or marine oil, disappears after an extended feeding period.

Effect of very long chain fatty acids on peroxisomal beta-oxidation in primary rat hepatocyte cultures.

Previous studies have demonstrated that certain high fat diets can induce peroxisomal fatty acid beta-oxidation in rodent liver and that this may be due to their content of trans 22:1 fatty acids. In this study we have examined the effects of cis and trans 22:1 fatty acids (erucic and brassidic) and oleic acid (18:1) on palmitoyl-CoA oxidation, carnitine acetyltransferase and carnitine palmitoyltransferase activities in primary rat hepatocyte cultures. Brassidic and erucic acid and, to a lesser extent, oleic acid were cytotoxic to rat hepatocytes. However, at a concentration of 0.1 mM, brassidic acid produced small increases in palmitoyl-CoA oxidation and carnitine acetyltransferase activities in hepatocytes cultured 70 hr. Treatment of cells with 0.1 and 0.3 mM of either erucic or oleic acid had no effect on any of the enzymes measured.