The effect of dietary partially hydrogenated marine oils on desaturation of fatty acids in rat liver microsomes

Serum Trans Fatty Acids Are Not Associated with Weight Gain or Linear Growth in School-Age Children

BACKGROUND

Animal and human adult studies indicate that long-term intake of trans fatty acids (TFAs) may be associated with weight gain. High intake of fast foods and snacks, which are rich in TFAs, is linked to overweight status among school-age children. However, the specific effects of TFAs in this population are unknown.

OBJECTIVE

We examined whether serum TFAs, used as biomarkers of intake, are associated with faster weight gain and linear growth during school years.

METHODS

We quantified TFAs by GLC in serum samples of 668 children aged 5-12 y at the time of recruitment into an ongoing cohort study performed in Bogota (Colombia) since 2006. Serum proportions of trans palmitoleic acid (16:1t), trans oleic acid (18:1t), trans linoleic acid (18:2t), and total TFAs were used as biomarkers of intake. Anthropometric characteristics were measured periodically for a median of 30 mo. Body mass index-for-age z scores (BAZs) and height-for-age z scores (HAZs) were calculated with the use of the WHO reference. We estimated mean changes in BAZs and HAZs over follow-up according to quartiles of each TFA at baseline by using mixed-effects regression models with restricted cubic splines.

RESULTS

Proportions of trans palmitoleic acid, trans oleic acid, trans linoleic acid, and total TFAs (mean ± SD, % of total serum FAs), were 0.22 ± 0.06, 0.91 ± 0.37, 0.96 ± 0.27, and 2.10 ± 0.59, respectively. Serum TFAs were not associated with changes in BAZs and HAZs after adjusting for sex, baseline age, and socioeconomic status. In a subgroup analysis by sex, serum trans palmitoleic acid was positively associated with the estimated change in HAZs from ages 6 to 14 y in boys (with use of the first quartile as the reference, differences in HAZs for trans palmitoleic acid quartiles were 0.73, 0.53, and 0.70, P-trend = 0.03).

CONCLUSIONS

Proportions of serum TFAs, used as biomarkers of TFA intake, were not associated with weight gain in children aged 6-14 y in low- and middle-income populations in Bogota. The proportion of trans palmitoleic acid was positively associated with linear growth in boys. Longer follow-up and studies in diverse cohorts with wider ranges of TFA intake are warranted.

Absorption of dietary cholesterol oxidation products and their downstream metabolic effects are reduced by dietary apple polyphenols

Exogenous and endogenous cholesterol oxidation products (COPs) perturb various metabolic processes, and thereby they may induce various homeostasis-related disorders. Here, we observed that procyanidin-rich dietary apple polyphenol (APP) from unripe apples alleviates the perturbation of lipid metabolism by decreasing the exogenous COP levels in rats. Dietary COPs may be the greatest source of COPs found in the human body. Rats (4 weeks of age) were fed AIN-purified diets containing 0.3% COPs supplemented with 0.5 or 2.5% APP for 3 weeks. Dietary APP alleviated the growth inhibition action of the exogenous COPs. The modulations of the liver lipid profile by COPs remained unchanged. However, serum total cholesterol, high-density lipoprotein cholesterol, and triglyceride levels increased following the intake of dietary APP. Further, dietary APP inhibited the increase in lipid peroxide levels in the liver and serum by COPs. The activity of hepatic Delta6 desaturase was lowered by dietary APP in a dose-dependent manner, although exogenous COPs generally increased the activity of this enzyme. In keeping with this observation, Delta6 desaturation indices in the phospholipids and cholesteryl esters of the liver and serum lipids were lower in the APP-fed groups than those in the control group. Dietary APP also promoted the excretion of exogenous COPs, cholesterol, and acidic steroids in feces. Therefore, the inhibition of intestinal absorption of COPs may partly contribute to the alleviation of the perturbation of lipid metabolism and lipid peroxidation levels. Thus, APP may be an important removal agent of exogenous toxic material such as COPs contained in processed or fast foods.

Comparison of regulative functions between dietary soy isoflavones aglycone and glucoside on lipid metabolism in rats fed cholesterol

The effects of dietary soy isoflavones aglycone and glucoside on lipid metabolism were compared in male Sprague-Dawley rats (4 weeks old) given purified diets containing 0.3% cholesterol. The rats were fed a diet supplemented with either isoflavone aglycone-rich powder (IF-A group) or isoflavone glucoside-rich powder (IF-G group) or isoflavone-free diet (control group) for 40 days. The additional level of isoflavone aglycone moiety in the diet was prepared to the same level (approximately 0.096 g/100 g: approximately 0.1% in diet). The activity of hepatic cholesterol 7alpha-hydroxylase tended to be slightly higher in the rats fed isoflavones than in those fed the isoflavone-free diet. On the other hand, the activity of hepatic Delta6 desaturase in the IF-A group was lower than that of the control group. Reflecting this effect, the Delta6 desaturation indices [(20:3n-6+20:4n-6)/18:2n-6] in liver phospholipids of the IF-A group were lower than those in the control group. Liver and serum total cholesterol levels and liver TG level were also reduced by consumption of isoflavone aglycone. Moreover, serum TG level was lowered by consumption of both isoflavones aglycone and glucoside. The level of serum total isoflavones in the IF-A group was significantly higher than that in the IF-G group. Therefore, we speculate that the absorption speed of isoflavone aglycones might be faster than that of isoflavone glucosides in rats. This study suggests that dietary soy isoflavones, particularly their aglycone form, may exert a beneficial effect on lipid metabolism in rats fed cholesterol.

Regulative actions of dietary soy isoflavone on biological antioxidative system and lipid metabolism in rats

Male Sprague-Dawley rats, 4 weeks of age, were fed purified diets either with or without 0.2% soy isoflavones rich powder for 5 weeks to elucidate their direct functions such as antioxidative action and regulation of lipid metabolism. Dietary soy isoflavones decreased serum lipid peroxide level in rats. Levels of liver and serum alpha-tocopherol were higher in the rats fed isoflavone than in those fed isoflavones-free diet. Thus, dietary soy isoflavones exhibited mild antioxidative function in this animal experiment. Isoflavone metabolites from diet may act as scavengers of reactive oxygen species. Dietary soy isoflavones lowered hepatic 3-hydroxy-3-methylglutaryl CoA reductase activity, although liver cholesterol level was not modulated. However, the levels of serum cholesterol and triglyceride decreased by consumption of soy isoflavones. Therefore, dietary soy isoflavones may exhibit hypocholesterolemic and hypolipidemic functions. Moreover, dietary soy isoflavones lowered hepatic Delta6 desaturase activity. Reflecting this observation, Delta6 desaturation indices ((18:2(n = 6) + 18:3(n = 6))/20:4(n = 6)) of tissue lipids tended to be lower in rats fed isoflavones than in those fed isoflavones-free diet. This action may contribute to the prevention of inflammatory response by imbalance of eicosanoids. These observations suggest that the positive intake of soy isoflavones may reduce the risk of some cardiovasucular diseases through their radical scavenging function and hypocholesterolemic action.

Effects of dietary eritadenine on the liver microsomal Delta6-desaturase activity and its mRNA in rats

Eritadenine, a hypocholesterolemic factor of Lentinus edodes mushroom, has a wide range of effects on lipid metabolism such as an increase in the liver microsomal phosphatidylethanolamine (PE) concentration, a decrease in the liver microsomal Delta6-desaturase activity, and an alteration of the fatty acid and molecular species profile of liver and plasma lipids. In this study, the time-dependent effects of dietary eritadenine on several variables concerning lipid metabolism were investigated in rats to clarify the sequence of metabolic changes caused by eritadenine, with special interest in the association of the liver microsomal phospholipid profile and the activity of Delta6-desaturase. The effect of dietary eritadenine on the abundance of mRNA for Delta6-desaturase was also investigated. When the time required for a half-change of variables was estimated during the first 5 days after the change from the control diet to the eritadenine-supplemented (50 mg/kg) diet, the change rates of the variables were fastest in the following order: alteration of the liver microsomal phospholipid profile>decrease in liver microsomal Delta6-desaturase activity>alteration of the fatty acid and molecular species profiles of microsomal and plasma phosphatidylcholine (PC)>decrease in the plasma cholesterol concentration. There was a significant correlation between the Delta6-desaturase activity and liver microsomal PE concentration, but not PC concentration, or the proportion of PC and PE or the PC/PE ratio. The suppression of Delta6-desaturase activity by dietary eritadenine was accompanied by a significant reduction in the abundance of mRNA for the enzyme. These results suggest that dietary eritadenine might suppress the activity of liver microsomal Delta6-desaturase by altering the microsomal phospholipid profile, as represented by an increase in PE concentration, and that the effect of eritadenine is mediated by the regulation of gene expression.

Eritadenine-induced alterations of plasma lipoprotein lipid concentrations and phosphatidylcholine molecular species profile in rats fed cholesterol-free and cholesterol-enriched diets

The effects of dietary eritadenine on the concentration of plasma lipoprotein lipids and the molecular species profile of plasma lipoprotein phosphatidylcholine (PC) were investigated in rats fed cholesterol-free and cholesterol-enriched diets to obtain insights into the relationship between the changes in PC molecular species profile and the hypocholesterolemic action of eritadenine. The effect of eritadenine on the secretion rate of very low density lipoprotein (VLDL) from the liver was also estimated. Rats were fed the control or eritadenine-supplemented (50 mg/kg) diets with or without exogenous cholesterol for 14 d. Eritadenine supplementation significantly decreased the cholesterol of major plasma lipoproteins, high density lipoprotein and VLDL, in rats fed cholesterol-free and cholesterol-enriched diets, respectively. The ratio of PC to phosphatidylethanolamine, delta6-desaturase activity, and the ratio of arachidonic acid to linoleic acid in liver microsomes were markedly decreased by eritadenine irrespective of the presence or absence of exogenous cholesterol. Dietary eritadenine increased the proportion of 16:0-18:2 molecular species with a decrease in 18:0-20:4 in plasma lipoprotein PC in both rats fed cholesterol-free and cholesterol-enriched diets. Eritadenine did not depress the secretion rate of VLDL in rats fed a cholesterol-free diet containing a high level of choline. The results indicate that dietary eritadenine elicits its hypocholesterolemic action with modulations of the fatty acid and molecular species profiles of PC irrespective of the presence or absence of exogenous cholesterol. The eritadenine-induced alteration of PC molecular species profile is discussed in relation to the hypocholesterolemic action of eritadenine.

Increased response of liver microsomal delta 6-desaturase activity to dietary methionine in rats

The effects of dietary casein level (5-40%) on the liver microsomal phospholipid profile, delta 6-desaturase activity and related variables were investigated in rats to examine whether the dietary protein level affected the delta 6-desaturase activity through an alteration of the liver microsomal phospholipid profile. The effects of supplementing a 10% casein diet with certain amino acids were also investigated. The concentration of hepatic S-adenosylmethionine (SAM), the ratio of phosphatidylcholine (PC) to phosphatidylethanolamine (PE) and the delta 6-desaturase activity in liver microsomes, and the ratio of arachidonate to linoleate of microsomal PC increased with increasing dietary casein level. There were significant correlations between the dietary methionine content and hepatic SAM concentration, hepatic SAM concentration and microsomal PE concentration, and microsomal PE concentration and delta 6-desaturase activity. Supplementation of the 10% casein diet with methionine significantly increased the hepatic SAM concentration, PC/PE ratio, delta 6-desaturase activity, and arachidonate/linoleate ratio, whereas cystine supplementation had no or little effect on these variables. These increases induced by methionine were significantly suppressed by additional glycine. The results obtained here, together with those in our previous report, suggest that quantity and type of dietary protein might affect the delta 6-desaturase activity through an alteration of the liver microsomal profile of phospholipids, especially PE, and that the alteration of phospholipid profile might be mediated by a hepatic SAM concentration that reflects the dietary methionine level.

Dietary eritadenine and ethanolamine depress fatty acid desaturase activities by increasing liver microsomal phosphatidylethanolamine in rats

The effects of eritadenine, a constituent of the Lentinus edodes mushroom, and ethanolamine, the base constituent of phosphatidylethanolamine (PE), on fatty acid desaturase activities and lipid profiles were investigated comparatively in rats. Rats were fed a control diet or a diet supplemented with either eritadenine (0.05 g/kg) or ethanolamine (8 g/kg) for 14 d. Eritadenine and ethanolamine had marked hypocholesterolemic effects. The concentration of liver microsomal PE was significantly increased and the ratio of phosphatidylcholine (PC) to PE was significantly decreased by both eritadenine and ethanolamine. These changes in phospholipid profile were also observed in the mitochondria and plasma membranes in the liver. The activities of the Delta5-, Delta6- and Delta9-desaturases in liver microsomes were significantly decreased by eritadenine and ethanolamine; there was a significant correlation between the activity of Delta5- or Delta6-desaturase and the proportion of PE in the total phospholipids or the PC/PE ratio. Reflecting decreased Delta5- and Delta6-desaturase activities, the 20:4(n-6)/18:2(n-6) ratio was significantly decreased by eritadenine and ethanolamine in PC of the liver microsomes, mitochondria and plasma membranes. Although the 20:4(n-6)/18:2(n-6) ratio of liver microsomal PE was also significantly decreased by eritadenine and ethanolamine, the fatty acid composition of phosphatidylinositol and phosphatidylserine was less affected by these compounds. Eritadenine and ethanolamine increased the proportion of 16:0-18:2 and decreased the proportion of 18:0-20:4 in liver PC. The results suggest that dietary eritadenine and ethanolamine might lead to decreases in desaturase activities and changes in fatty acid and molecular species composition of PC through an increase in liver microsomal PE.

Effects of dietary eritadenine on delta6-desaturase activity and fatty acid profiles of several lipids in rats fed different fats

Effects of dietary eritadenine on liver microsomal delta6-desaturase activity and the fatty acid profile of phosphatidylcholine, cholesteryl esters, and triglycerides of liver microsomes or plasma were investigated in rats fed different fats (palm oil, olive oil, and safflower oil). The activity of delta6-desaturase was influenced by both dietary fat types and eritadenine. In rats fed control diets, delta6-desaturase activity was higher in the order of the palm oil, olive oil, and safflower oil groups. In rats fed eritadenine-supplemented diets, the enzyme activity was markedly decreased to a constant level irrespective of dietary fat type. The 20:4n-6/18:2n-6 ratio of phosphatidylcholine and cholesteryl esters, as compared with triglycerides, was highly sensitive to eritadenine. The results suggest that the activity of delta6-desaturase is regulated by dietary fats and eritadenine independently, and that the effect of eritadenine is stronger than that of dietary fats.

Metabolic fate and selective utilization of major fatty acids in human sebaceous gland

The sebaceous gland is an integral part of the pilosebaceous unit of mammalian skin, which produces and secretes a unique mixture of lipids, known as sebum. Wax esters, which account for approximately 25% of human sebaceous lipids, are unique in that they are not synthesized by other cells in the body. To explore the biosynthesis of wax esters, the metabolic fate of exogenously supplied saturated (16:0, 18:0), mono-unsaturated Delta9 (16:1, 18:1), and polyunsaturated (18:2, Delta9,12) fatty acids was followed in biopsy punches from human facial skin rich in sebaceous glands. Acetate was incorporated into all of the cellular and secreted lipids and 16:0 was incorporated into all of the fatty-acid-containing lipids. The 16:0 was elongated to 18:0 and the 16:1 was incorporated primarily into polar lipids, secondarily into triglycerides, but not into other lipids and was elongated to 18:1 (Delta11). As proven by HPTLC analysis, both 18:0 and 18:1 were incorporated into the cellular lipids but at a lower rate into wax esters. Moreover, addition of exogenous 18:1 was not further processed following initial incorporation. Linoleic acid (18:2, Delta9,12) was the only fatty acid tested that appeared to be subjected to beta-oxidation. This was proven to be specific to linoleic acid, as it did not induce the oxidation of other fatty acids. The ability of the sebaceous cells to synthesize wax esters correlated with the beta-oxidation activity in these cells. Thus, the oxidation of linoleic acid is specific for the sebaceous cells and correlates with their function and differentiation. Our results provide evidence that the sebaceous gland selectively utilizes fatty acids as 16:0 is the preferred fatty acid that is incorporated into wax esters and linoleic acid undergoes beta-oxidation.

Metabolic characterization of sciadonic acid (5c,11c,14c-eicosatrienoic acid) as an effective substitute for arachidonate of phosphatidylinositol

Sciadonic acid (20:3 Delta-5,11,14) is an n-6 series trienoic acid that lacks the Delta8 double bond of arachidonic acid. This fatty acid is not converted to arachidonic acid in higher animals. In this study, we characterized the metabolic behavior of sciadonic acid in the process of acylation to phospholipid of HepG2 cells. One of the characteristics of fatty acid compositions of phospholipids in sciadonic acid-supplemented cells is a higher proportion of sciadonic acid in phosphatidylinositol (PtdIns) (27.4%) than in phosphatidylethanolamine (PtdEtn) (23.2%), phosphatidylcholine (PtdCho) (17.3%) and phosphatidylserine (PtdSer) (20.1%). Similarly, the proportion of arachidonic acid was higher in PtdIns (35.8%) than in PtdEtn (29.1%), PtdSer (18.2%) and PtdCho (20.2%) in arachidonic-acid-supplemented cells. The extensive accumulation of sciadonic acid in PtdIns resulted in the enrichment of newly formed 1-stearoyl-2-sciadonoyl molecular species (38%) in PtdIns and caused the reduction in the level of pre-existing arachidonic-acid-containing molecular species. The kinetics of incorporation of sciadonic acid to PtdEtn, PtdSer and PtdIns of cells were similar to those of arachidonic acid. In contrast to sciadonic acid, neither eicosapentaenoic acid (20:5 Delta-5,8,11,14,17) nor juniperonic acid (20:4 Delta-5,11,14,17) accumulated in the PtdIns fraction. Rather, these n-3 series polyunsaturated fatty acids, once incorporated into PtdIns, tended to be excluded from PtdIns. In addition, the level of arachidonic-acid-containing PtdIns molecular species remained unchanged by eicosapentaenoic-acid-supplementation. These results suggest that sciadonic acid or sciadonic-acid-containing glycerides are metabolized in a similar manner to arachidonic acid or arachidonic-acid-containing glyceride in the biosynthesis of PtdIns and that sciadonic acid can effectively modify the molecular species composition of PtdIns in HepG2 cells. In this regard, sciadonic acid will be an interesting experimental tool to clarify the significance of arachidonic acid-residue of PtdIns-origin bioactive lipids.

Dietary soybean protein moderates the deleterious disturbance of lipid metabolism caused by exogenous oxidized cholesterol in rats

Effects of dietary protein on oxidized cholesterol-induced disturbance of lipid metabolism were examined in 4 week old male Sprague-Dawley rats, using casein and soybean protein as dietary protein source. The rats were given one of the two proteins in 0. 078% cholesterol (control), 0.25% cholesterol or 0.25% oxidized cholesterol mixture (containing 0.078% cholesterol) diets. Dietary oxidized cholesterol, compared to cholesterol, tended to inhibit hepatic sterol biosynthesis in casein-fed rats, whereas this inhibitory action was slightly moderated by intake of soybean protein. As a result, the hepatic 3-hydroxy-3-methylglutaryl-CoA reductase activity was rather higher in the rats fed oxidized cholesterol than in those fed cholesterol in the soybean protein-fed group. The hepatic cholesterol 7alpha-hydroxylase activity tended to be higher in the rats fed oxidized cholesterol than in those fed control diet in the soybean protein-fed group, despite the fact that oxidized cholesterol lowered the hydroxylase activity in the casein-fed group. On the other hand, dietary oxidized cholesterol tended to slightly enhance the hepatic Delta6 desaturase activity in the casein-fed group; however, this observation was not shown in the soybean protein-fed group. Moreover, dietary soybean protein facilitated fecal oxidized cholesterol excretion and simultaneously inhibited the accumulation of oxidized cholesterol in serum and liver. In conclusion, dietary soybean protein alleviated the deleterious actions of exogenous oxidized cholesterol on hepatic cholesterol and linoleic acid metabolism, although these efficacies were not necessarily significant. A great part of these moderations may be exerted by the specific hypocholesterolemic function of soybean protein, such as the stimulation of fecal oxidized cholesterol excretion, the change of hormonal release and modulation of lipoprotein catabolism.

Effects of a mixture of organisms, Lactobacillus acidophilus or Streptococcus faecalis on delta6-desaturase activity in the livers of rats fed a fat- and cholesterol-enriched diet

The effect of a mixture of organisms (a probiotic mixture) comprising Bacillus, Lactobacillus, Streptococcus, Clostridium, Saccharomyces, and Candida (10(7-8) colony-forming units/g rice bran of each component) on delta6-desaturase activity in liver microsomes was compared with those of Lactobacillus acidophilus and Streptococcus faecalis. There were four treatment groups. Each group of these rats received rice bran (control), the mixture of organisms, L. acidophilus, or S. faecalis (30 g/kg) along with a fat- and cholesterol-enriched diet for 4 wk. The serum total cholesterol concentration of the group fed the mixture of organisms was reduced by 15-33% compared with the other groups at the end of the 4-wk feeding period (P<0.05). The proportion of palmitic acid in the serum phosphatidylcholine (PC) for the control group was significantly higher than those of the other groups. The proportion of arachidonic acid in the serum PC for the mixed-organism group was also significantly higher than those of the other groups. The proportion of arachidonic acid in the liver PC for the mixed-organism group was significantly higher than those of the control and S. faecalis groups. The ratio of arachidonic acid/linoleic acid was significantly higher in the liver PC of rats fed the mixed organisms compared with the control group (P<0.05). The delta6-desaturase activity in the liver microsomal fraction of the mixed-organism group was significantly higher than those of the other groups. The delta6-desaturase activity correlated positively with the ratio of arachidonic acid/linoleic acid of liver PC, the correlation coefficient (r) being 0.819 (P<0.001). The results indicate that the effect of the mixture of organisms was to increase delta6-desaturase activity and serum arachidonic acid and decrease cholesterol compared to the other organisms and control, but the mechanism whereby the enzyme activity was related to serum cholesterol does not appear to have been explored.

Correlation of suppressed linoleic acid metabolism with the hypocholesterolemic action of eritadenine in rats

The dose-dependent effects of dietary eritadenine on the metabolism of linoleic acid and on the plasma cholesterol concentration were investigated to clarify the mechanism of the hypocholesterolemic action of eritadenine in rats. Rats were fed control or eritadenine-supplemented (2 to 20 mg/kg) diets for 14 d. Eritadenine supplementation significantly decreased both the plasma cholesterol concentration and the 20:4n-6/18:2n-6 ratio of liver microsomal and plasma phosphatidylcholine (PC) in a dose-dependent manner. Eritadenine was also found to decrease the activity of delta 6 desaturase in liver microsomes; there was significant correlation between the delta 6-desaturase activity and the 20:4n-6/18:2n-6 ratio in the PC of liver microsomes (r = 0.989, P < 0.001) or plasma (r = 0.986, P < 0.001). Certain plasma PC molecular species, as represented by 16:0-18.2, were increased by eritadenine in a dose-dependent manner, and certain plasma PC molecular species, as represented by 18:0-20:4, were conversely decreased by eritadenine. There was a significant correlation between the plasma total cholesterol concentration and the proportion of the sum of plasma PC molecular species which contain 18:1 or 18:2 in the sn-2 position. These results support the idea that the suppression of linoleic acid metabolism by eritadenine might be associated with the hypocholesterolemic action of eritadenine.

Clofibrate treatment increases stearoyl-CoA desaturase mRNA level and enzyme activity in mouse liver

Stearoyl-CoA desaturase activity is encoded by two highly homologous genes, SCD1 and SCD2, which show tissue-specific expression and regulation. SCD1, which is expressed in the liver, showed a marked diurnal variation with the highest expression during the feeding period. Treatment of mice with the peroxisome proliferator clofibrate, which induces several lipid metabolizing enzymes, increased both the enzyme activity and mRNA level in the liver, indicating regulation at the transcriptional level. The highest expression of both SCD1 and SCD2 was found in brown adipose tissue, which was slightly down-regulated by feeding a fat-free diet.

Oxidized cholesterol modulates age-related change in lipid metabolism in rats

For three weeks, male Sprague-Dawley rats at either four weeks (young) or eight months (adult) of age were pair-fed one of the purified diets free of or containing either 0.2% of oxidized cholesterol mixture (cholesterol oxidation products) or 0.2% of cholesterol. Although the food intake was similar, dietary oxidized cholesterol lowered body weight gain in young rats, but did not increase relative liver weight, in contrast to the enlargement seen with dietary cholesterol. Oxidized cholesterol, compared to cholesterol, tended to reduce the activity of hepatic 3-hydroxy-3-methylglutaryl CoA reductase and cholesterol 7 alpha-hydroxylase, particularly the latter in aged rats, and prevented the rise in the concentration of liver cholesterol at both ages. It also tended to increase the activity of hepatic delta 6 desaturase, particularly in young rats. Moreover, oxidized cholesterol in relation to cholesterol influenced liver and serum lipid concentrations in different ways, and increased lipid peroxidation at both ages. The ratio of splenic CD4+/CD8+ T-lymphocytes increased with age, but the influence of cholesterol and oxidized cholesterol was comparable. Thus, oxidized cholesterol may specifically disturb growth and age-related changes in the lipid metabolism in rats.

Effects of dietary proteins on linoleic acid desaturation and membrane fluidity in rat liver microsomes

The effect of dietary protein, casein (CAS) and soybean protein (SOY), on linoleic acid desaturation in liver microsomes was studied in rats. The activity of delta 6 desaturase in total and rough endoplasmic reticula (ER and RER) was significantly higher in the CAS group than in the SOY group. In ER and smooth endoplasmic reticulum, the steady-state fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene, when incorporated into the membrane, was decreased in the SOY group and accompanied by a reduction in the cholesterol/phospholipid (CHOL/PL) ratio, consistent with an increase in membrane fluidity. In a separate study, the effect of varying dietary proteins, CAS, milk whey protein, egg albumin, SOY, potato protein and wheat gluten, on the relationship between the delta 6 desaturase activity and microsomal membrane fluidity was also examined. The results indicated that the dietary protein-dependent change in the liver microsomal CHOL/PL ratio affected membrane fluidity, and subsequently the activity of delta 6 desaturase in liver microsomes. However, since dietary protein influenced the delta 6 desaturase activity in RER without influencing membrane fluidity, it is possible that some regulation might have taken place at the level of enzyme synthesis.

trans fatty acids. 5. Fatty acid composition of lipids of the brain and other organs in suckling piglets

The effects of dietary trans fatty acids on the fatty acid composition of the brain in comparison with other organs were studied in 3-wk-old suckling piglets. In Experiment (Expt.) 1 the piglets were delivered from sows fed partially hydrogenated fish oil (PHFO) (28% trans), partially hydrogenated soybean oil (PHSBO) (36% trans) or lard (0% trans). In Expt. 2 the piglets were delivered from sows fed PHFO, hydrogenated fish oil (HFO) (19% trans) or coconut fat (CF) (0% trans) with two levels of dietary linoleic acid (1 and 2.7%) according to factorial design. In both experiments the mother's milk was the piglets' only food. The level of incorporation of trans fatty acids in the organs was dependent on the levels in the diets and independent of fat source (i.e., PHSBO, PHFO or HFO). Incorporation of trans fatty acids into brain PE (phosphatidylethanolamine) was non-detectable in Expt. 1. In Expt. 2, small amounts (less than 0.5%) of 18:1 trans isomers were found in the brain, the level being slightly more on the lower level of dietary linoleic acid compared to the higher. In the other organs the percentage of 18:1 trans increased in the following order: heart PE, liver mitochondria PE, plasma lipids and subcutaneous adipose tissue. Small amounts of 20:1 trans were found in adipose tissue and plasma lipids. Other very long-chain fatty acids from PHFO or HFO (i.e., 20:1 cis and 22:1 cis + trans) were found in all organ lipids except for brain PE. Dietary trans fatty acids increased the percentage of 22:5n-6 in brain PE.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibitory effect of curcumin on fatty acid desaturation in Mortierella alpina 1S-4 and rat liver microsomes

An extract of rhizomes of Curcuma longta L. (turmeric) inhibited the desaturation of dihomo-gamma-linolenic acid (DGLA) in the arachidonic acid (AA) producing fungus Mortierella alpina 1S-4. The factor responsible for this phenomenon was isolated and identified as curcumin (diferuloyl methane). Mycelial DGLA levels increased about two-fold (22.3 mg/g dry weight) with a concomitant decrease in AA levels when the fungus was cultivated with curcumin. The 50% inhibitory concentration against delta 5 desaturase was 27.2 microM. Curcumin also inhibited rat liver microsomal delta 5 and delta 6 desaturases.

Trans fatty acids. 4. Effects on fatty acid composition of colostrum and milk

trans Isometric fatty acids of partially hydrogenated fish oil (PHFO) consist of trans 20:1 and trans 22:1 in addition to the trans isomers of 18:1, which are abundant in hydrogenated vegetable oils, such as in partially hydrogenated soybean oil (PHSBO). The effects of dietary trans fatty acids in PHFO and PHSBO on the fatty acid composition of milk were studied at 0 (colostrum) and 21 days postpartum in sows. The dietary fats were PHFO (28% trans), or PHSBO (36% trans) and lard. Sunflower seed oil (4%) was added to each diet. The fats were fed from three weeks of age throughout the lactation period of Experiment 1. In Experiment 2 PHFO or "fully" hydrogenated fish oil (HFO) (19% trans), in comparison with coconut oil (CF) (0% trans), was fed with two levels of dietary linoleic acid, 1 and 2.7%, from conception throughout the lactation period. Feeding trans-containing fats led to secretion of trans fatty acids in the milk lipids. Levels of trans 18:1 and trans 20:1 in milk lipids, as percentages of total cis + trans 18:1 and cis + trans 20:1, respectively, were about 60% of that of the dietary fats, with no significant differences between PHFO and PHSBO. The levels were similar for colostrum and milk. Feeding HFO gave relatively less trans 18:1 and trans 20:1 fatty acids in milk lipids than did PHFO and PHSBO. Only low levels of cis + trans 22:1 were found in milk lipids.(ABSTRACT TRUNCATED AT 250 WORDS)

Sesamin is a potent and specific inhibitor of delta 5 desaturase in polyunsaturated fatty acid biosynthesis

Incubation with sesame oil increases the mycelial dihomo-gamma-linolenic acid content of an arachidonic acid-producing fungus, Mortierella alpina, but decreases its arachidonic acid content [Shimizu, S., K. Akimoto, H. Kawashima, Y. Shinmen and H. Yamada (1989) J. Am. Oil Chem. Soc. 66, 237-241]. The factor causing these effects was isolated and identified to be (+)-sesamin. The results obtained in experiments with both a cell-free extract of the fungus and with rat liver microsomes demonstrated that (+)-sesamin specifically inhibits delta 5 desaturase at low concentrations, but does not inhibit delta 6, delta 9 and delta 12 desaturases. Kinetic analysis showed that (+)-sesamin is a noncompetitive inhibitor (Ki for rat liver delta 5 desaturase, 155 microM). (+)-Sesamolin, (+)-sesaminol and (+)-episesamin also inhibited only delta 5 desaturases of the fungus and liver. These results demonstrate that (+)-sesamin and related lignan compounds present in sesame seeds or its oil are specific inhibitors of delta 5 desaturase in polyunsaturated fatty acid biosynthesis in both microorganisms and animals.

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.

Evidence for the induction of fatty acid desaturation in proliferating hepatic endoplasmic reticulum in response to treatment with polychlorinated biphenyls. Are fatty acid desaturases cytochrome P-450-dependent monooxygenases?

1. Polychlorinated biphenyls (PCBs) are abundant and persistent pollutants in the ecosystem which accumulate in biological systems. 2. We have shown previously (Borlakoglu et al., 1990; Eur. J. Biochem. 118, 327-332) that 120 hr after treating pigeons and rats with 1.5 mmol Aroclor 1254/kg body weight, hepatic microsomal membranes showed significant increases in the proportion of arachidonate (20:4,5, 8,11,14), in the concentration of cytochrome P-450 and in the activities of a wide range of cytochrome P-450-dependent enzymes involved in the metabolism of drugs and other xenobiotics. 3. After treating pigeons and rats in vivo with Aroclor 1254, linoleate desaturases activity increased significantly 3.35-, 4.35-, 5.83- and 8.61-fold 24, 48, 68 and 120 hr for pigeons and 2- and 7-fold for rats respectively 48 and 120 hr post treatment. The total activity of linoleate desaturases in the whole liver of pigeons and rats increased 40- and 10-fold respectively. 4. There were excellent correlations between the concentrations of cytochrome b5 and cytochrome P-450 and the activity of pigeon linoleate desaturases. Extrapolation of the concentration of cytochrome P-450 to zero is coincident with zero linoleate desaturase activity. 5. Evidence is presented to suggest the novel concept that linoleate desaturation is dependent upon the catalytic cycle of these monooxygenases.

Influence of dietary linoleic acid and trans fatty acids on the fatty acid profile of cardiolipins in rats

Cardiolipins (CL) have unique fatty acid profiles with generally high levels of polyunsaturated fatty acids, primarily 18:2n-6, and low levels of saturated fatty acids. In order to study the effect of dietary fatty acid isomers on the fatty acid composition of cardiolipins, rats were fed partially hydrogenated marine oils (HMO), rich in 16:1, 18:1, 20:1, and 22:1 isomeric fatty acids, supplemented with linoleic acid at levels ranging from 1.9% to 14.5% of total fat. Although the dietary fats contained 33% trans fatty acids, the levels of trans fatty acids in CL were below 2.5% in all organs. The fatty acid profiles of cardiolipins of liver, heart, kidney and testes showed different responses to dietary linoleic acid level. In liver, the contents of 18:2 reflected the dietary levels. In heart and kidney, the levels of 18:2 also paralleled increasing dietary levels, but in all groups fed HMO, levels of 18:2 were considerably higher than in the reference group fed palm oil. In testes, the 18:2 levels were unaffected by the dietary level of 18:2 and HMO.

Age-related changes of lipid fractions and total fatty acids in liver lipids and heart lipids of female and male rats aged 37-1200 days (liver) and 331-1200 days (heart)

1. Total lipids and the lipid fractions cholesterol ester, triacylglycerol, free cholesterol, free fatty acids and phospholipids, as well as the fatty acid patterns of total lipids, were measured in liver homogenates of female and male rats (Wistar SPF, strain Hannover) aged 37-1213 days. 2. The same parameters were measured in the apex of the heart in female and male rats aged 331-1213 days. 3. All parameters were monitored every 49th day. Five female and five male animals were used in each experiment. 4. The lipid fractions in liver showed a positive linear regression vs age, whereas all lipids in rat heart showed a negative regression vs age in both sexes. 5. The significance of regression vs age of fatty acids was much less than that in the lipid fractions of liver and heart of these animals.

Trans fatty acids. 3. Fatty acid composition of the brain and other organs in the newborn piglet

The effects of dietary trans fatty acids on tissue fatty acid composition were studied in newborn piglets delivered from sows fed partially hydrogenated fish oil (PHFO) (28% trans) or partially hydrogenated soybean oil (PHSBO) (36% trans) in comparison with lard (0% trans) from 3 wk of age and through gestation in Experiment 1, or fed PHFO or "fully" hydrogenated fish oil (HFO) (19% trans) in comparison with coconut oil (CF) (0% trans) with two levels, 1 and 2.7%, of dietary linoleic acid from conception through gestation in Experiment 2. The piglets were sampled immediately after delivery, without having access to mothers' milk. Incorporation of trans fatty acids into brain PE (phosphatidylethanolamine) were non-detectable or very low (less than 0.1%). The incorporation of 18:1 trans into heart-PE, liver mitochondria-PE, total plasma lipids and adipose tissue was low, and 20:1 trans was not detected. Dietary trans fatty acids had no consistent effects on the overall fatty acid composition of the different tissue lipids. It is concluded that trans fatty acids from PHFO, HFO and PHSBO have no significant effects on the fatty acid accretion in the fetal piglet.

Levels of dihomo-gamma-linolenate are depressed in heart phosphatidylcholine and phosphatidylethanolamine in the biotin-deficient chick

Male broiler chicks were fed a purified diet with 0 or 500 micrograms/kg of added biotin for 21 days posthatch. Fatty acid composition of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were determined in erythrocytes and in heart mitochondria and microsomes of chicks at 12 and 21 days of age. The biotin-deficient (BD, 0 microgram biotin) chicks had lower body weights, lower feed efficiencies, and higher scores for dermatitis and twisted leg than the biotin-adequate (BA, 500 micrograms biotin) chicks. The erythrocyte arachidonate level in PC was higher in BD chicks compared to the BA controls, and the level increased with age in PC and PE in the erythrocytes. The level of dihomo-gamma-linolenate (20:3 omega 6) in PC and PE in heart mitochondria and microsomes was consistently decreased in BD chicks compared with that in BA chicks. In heart subcellular organelles, the level of arachidonate in PC increased, but the level of dihomo-gamma-linolenate in PE decreased with age. These data demonstrate that biotin deficiency results in dramatic changes in the fatty acid composition of specific phospholipids in chick erythrocytes and heart subcellular organelles.

Dietary linoleic acid and the fatty acid profiles in rats fed partially hydrogenated marine oils

The influence of the linoleic acid levels of diets containing partially hydrogenated marine oils (HMO) rich in isomeric 16:1, 18:1, 20:1 and 22:1 fatty acids on the fatty acid profiles of lipids from rat liver, heart and adipose tissue was examined. Five groups of rats were fed diets containing 20 wt % fat--16% HMO + 4% vegetable oils. In these diets, the linoleic acid contents varied between 1.9% and 14.5% of the dietary fatty acids, whereas the contents of trans fatty acids were 33% in all groups. A sixth group was fed a partially hydrogenated soybean oil (HSOY) diet containing 8% linoleic acid plus 32% trans fatty acids, mainly 18:1, and a seventh group, 20% palm oil (PALM), with 10% linoleic acid and no trans fatty acids. As the level of linoleic acid in the HMO diets increased from 1.9% to 8.2%, the contents of (n-6) polyunsaturated fatty acids (PUFA) in the phospholipids increased correspondingly. At this dietary level of linoleic acid, a plateau in (n-6) PUFA was reached that was not affected by further increase in dietary 18:2 (n-6) up to 14.5%. Compared with the HSOY- or PALM-fed rats, the plateau values of 20:4(n-6) were considerably lower and the contents of 18:2(n-6) higher in liver phosphatidylcholines (PC) and heart PC. Heart phosphatidylethanolamines (PE) on the contrary, had elevated contents of 20:4(n-6), but decreased 22:5(n-6) compared with the PALM group.(ABSTRACT TRUNCATED AT 250 WORDS)

Trans fatty acids. 1. Growth, fertility, organ weights and nerve histology and conduction velocity in sows and offspring

Effects of dietary trans fatty acids on the pre- and postnatal growth and development in pigs were studied with special emphasis on nervous tissue. In experiment 1, female pigs were fed partially hydrogenated fish oil (PHFO) (28% trans) or soybean oil (PHSBO) (36% trans), in comparison with lard (0% trans) from weaning (3 wk) through the first reproduction cycle (up to 2 yr). In experiment 2, female pigs were fed two fish oils (33 and 19% trans) in comparison with coconut oil (0% trans) in diets with low and high levels of linoleic acid (18:2n-6 cis, cis) from gestation until their offspring were three wk old. Compared with the trans-free fats, the trans-containing fats had no effect on growth and development, feed consumption and utilization or on the weight of the brain, heart, kidneys, liver, lungs or spleen in the adult sows and their offspring. No effects from the experimental fats were found on histology and conduction velocity of the peroneal nerve. An increased number of the sows fed PHFO had fertility problems compared with those fed lard and PHSBO in Expt. 1, but no similar effects were seen in Expt. 2. It is concluded that consumption of trans fatty acids with 18-22 carbon atoms from PHFO and with 18 carbon atoms from PHSBO at levels that were 5 to 12 times higher than those normally consumed by humans had no detrimental effects on female pigs or their offspring during pregnancy and lactation.

Trans fatty acids. 2. Fatty acid composition of the brain and other organs in the mature female pig

Female pigs were fed from three wk of age and up to two years a diet containing partially hydrogenated fish oil (PHFO, 28% trans monoenoic fatty acids), partially hydrogenated soybean oils (PHSBO, 36% trans fatty acids) or lard. No consistent differences were found between PHFO and PHSBO with regard to incorporation of trans fatty acids in organ lipids, but trans incorporations were highly organ-specific. No trans fatty acids were detected in brain phosphatidylethanolamine (PE). The incorporation of monoenoic trans isomers, as a percentage of total cis + trans, in other organs was highest in subcutaneous adipose tissue and liver mitochondria PE, followed by blood lipids with the lowest level in heart PE. The percentage of trans isomers compared with that of dietary lipids was consistently lower for 20:1, compared with 18:1 in organs from PHFO-fed pigs. The only effect of dietary trans fatty acids on the fatty acid pattern of brain PE was an increased level of 22:5n-6. Heart PE and total serum lipids of pigs fed the hydrogenated fats contained higher levels of 18:2n-6, and these lipids of the PHFO-fed group also contained slightly elevated amounts of 20:3n-6, 18:3n-3 and 20:5n-3. Liver mitochondria PE of the PHFO group also contained higher levels of 20:3n-6 and 22:5n-6. Dietary trans fatty acids caused a consistent decrease of saturated fatty acids compensated by increased levels of monoenes.(ABSTRACT TRUNCATED AT 250 WORDS)

Liver subcellular fatty acid profiles of chicks fed diets containing hydrogenated fats and varying linoleate levels

Day-old male broiler chickens were fed semipurified diets containing 5% lipid from one of four different lipid sources: corn oil (CO), partially hydrogenated soybean oil (HSBO), a spent restaurant grease (SRG) and a purified mixture of triolein, tripalmitin and tristearin (OPS). Diets CO and HSBO contained adequate amounts of linoleic acid, but diets SRG and OPS were deficient in linoleate. In addition, SRG and HSBO contained trans isomers of 16:1 and 18:1. The diets were fed for 3 wk to determine the effects of low linoleate levels and trans isomers on fatty acid profiles in liver microsomes, mitochondria and cytosol. Chicks fed HSBO had the highest body weights, while those fed SRG and OPS had the lowest. The incidence and severity of dermatitis were similar for all treatments. The proportions of linoleate and arachidonate in lipids from liver subcellular fractions were reduced significantly in chicks fed OPS and SRG; however, levels of 20:3 omega 9 were not increased. Feeding HSBO, which is high in both linoleate and linolenate, resulted in higher levels of 18:3 omega 3 and 20:5 omega 3 in liver subcellular fractions and lower levels of 20:4 omega 6 than those seen in chicks fed CO. The isomeric forms of 18:1 present in the partially hydrogenated fats (HSBO and SRG) appeared to be incorporated into the lipids of liver fractions. The results of this study show that dietary lipids influence fatty acid profiles of chick liver microsomes, mitochondria and cytosol. Decreases in linoleate and arachidonate in these organelles occur before overt essential fatty acid (EFA), deficiency signs in chicks fed EFA-deficient diets.

Influence of dietary partially hydrogenated vegetable and marine oils on membrane composition and function of liver microsomes and platelets in the rat

The aim of the present study was to investigate the influence of partially hydrogenated vegetable and marine oils on membrane composition and function of liver microsomes and platelets with particular reference to the metabolism of linoleic acid and the production of arachidonic acid metabolites. Four groups of male weanling rats were fed linoleic acid supplemented diets containing 20% (w/w) of partially hydrogenated low erucic acid rapeseed oil (HLRSO), partially hydrogenated herring oil (HHO), olive oil (OO) and trierucin + triolein (TE) for 10 weeks. An additional two groups were fed partially hydrogenated low erucic acid rapeseed oil and partially hydrogenated herring oil without linoleic acid supplementation (HLRSO- and HHO-, respectively). Substantial amounts of trans fatty acids were incorporated into liver microsomes (12.6% in group HLRSO) and platelets (7.0% in group HLRSO-). This incorporation was not dependent on the dietary linoleic acid level. Hepatic microsomal delta5 -desaturase activity was significantly increased after HLRSO feeding compared to 00 feeding. Delta6 -Desaturase activity did not vary in the linoleic acid supplemented groups. Both delta5 -and delta6 -desaturase activities were significantly increased in groups without linoleic acid supplementation. Docosenoic acid was incorporated into platelet phospholipids in contrast to liver microsomes. In the platelet, docosenoic acid seemed to have a special preference for phosphatidylserine. Very small amounts were incorporated into platelet phosphatidylinositol. Feeding diets HLRSO, HHO and 00 did not influence rat platelet cyclooxygenase or 12-lipoxygenase activity. Platelets from rats fed TE, however, produced significantly less 12-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) than platelets from rats fed OO. Feeding of HLRSO- and HHO- resulted in a significantly diminished production of the arachidonic acid metabolites 12-HETE, 12-hydroxy-5,8,10-heptadecatrienoic acid (HHT) and 6-keto-prostaglandin F1alpha in stimulated platelets and aorta. Thus, high dietary levels of trans isomers of monoenoic acids do not interfere with platelet cyclooxygenase or lipoxygenase activity provided sufficient amounts of linoleic acid are available.

Incorporation of trans fatty acids into submandibular salivary gland lipids

Three groups of rats were fed diets containing 20% corn oil, 20% margarine stock (MS) or 19% MS + 1% corn oil. Diets were fed for 12 weeks, 1 week of pregnancy, 3 weeks of lactation and 8 weeks post-weaning. The incorporation of trans-octadecenoate into various lipids of the submandibular salivary gland (SMSG) homogenates and plasma membranes was studied. Trans octadecenoate was incorporated into all the lipid fractions studied. Its levels were the highest in phosphatidylethanolamine. The double bond index of phospholipid fatty acids in the plasma membranes of the SMSG was substantially lower in the group fed 20% MS. The fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) was generally higher in the membranes of SMSG from rats fed MS than that of the other two groups, thus indicating lower fluidity. Also, the breakpoints in fluorescence polarization were at a higher temperature in the membranes from rats fed MS as compared with those fed corn oil. Lower fluidity of plasma membranes of SMSG observed in rats fed 20% MS may result in modification of the activities of membrane-bound enzymes.

The effects of trans fatty acids on fatty acyl delta 5 desaturation by human skin fibroblasts

The effectiveness of different fatty acids as inhibitors of fatty acyl delta 5 desaturation activity in human skin fibroblasts has been investigated. When incubated with 2.25 microM [14C] eicosatrienoate (20:3 omega 6) in otherwise lipid-free medium, these cells rapidly incorporate the radiolabeled fatty acid into cellular glycerolipids and desaturate it to produce both [14C] arachidonate and [14C]docosatetraenoate. The delta 5 desaturation activity can be enhanced by prior growth of the cells without serum lipids. Elaidate (9t-18:1) is a potent inhibitor of delta 5 desaturation while trans-vaccenate (11t-18:1) is virtually without effect. Oleate and linoleate are only mildly inhibitory. Linoelaidate (9t,12t-18:2) is more inhibitory than linoleate but significantly less effective than elaidate. The effects of elaidate can be readily overcome by increasing the concentration of exogenous eicosatrienoate. Studies with a variety of trans monounsaturates of differing chain lengths indicate that the omega 9 trans fatty acids are potent inhibitors of delta 5 desaturation, while omega 7 trans fatty acids are relatively ineffective. Intact human fibroblasts could thus be important in characterizing novel fatty acids as selective inhibitors of arachidonate synthesis in vivo.

Changes in the content of n-6 fatty acids in liver phospholipids in rats as a consequence of partially hydrogenated dietary oils

The effects of unhydrogenated and partially-hydrogenated marine and rapeseed oils on the relative content of n-6 fatty acids in rat liver phospholipids were studied by gas-liquid chromatography. The type of dietary oil strongly affected the pattern of n-6 fatty acids in the liver phospholipids even after a relatively short feeding period (3 weeks). With diets deficient in linoleic acid, accumulation of the 20:3 n-9 fatty acid was observed in the animals receiving partially hydrogenated oils, but not in the animals receiving the unhydrogenated marine oil which contained relatively high amounts of polyunsaturated fatty acids of the n-3 family. The results presented are in line with reports in the literature that dietary trans fatty acids may inhibit the desaturation-elongation enzyme systems of rat liver. The observed effects did not appear to be directly correlated to the dietary content of very-long-chain monounsaturated fatty acids.

Effect of dietary fats on desaturase activities and the biosynthesis of fatty acids in rat-liver microsomes

Four groups of rats were fed diets containing 15% (w/w) high-oleic safflower oil (SFO, rich in cis-18:1 acids), a mixture of 80% partially hydrogenated soybean oil plus 20% corn oil (H + CO, rich in trans-18:1 acids), lard (L, rich in saturated fatty acids) and corn oil (Co, rich in 18:2 omega 6). Fatty acid composition of liver microsomes and activities of the delta 5, delta 6 and delta 9 desaturases were determined. Microsomal delta 6 desaturase activity and arachidonic acid were lower in the H + CO group compared with SFO of L. No difference was found in the delta 5 or delta 6 desaturase activity of CO and SFO groups. Thus, the oleic-acid level of the SFO diet had no effect on the metabolism of 18:2 omega 6. Fluorescent polarization studies, using trans-parinaric acid as a probe, showed no differences between the physical states of phospholipid vesicles made from lipids isolated from each group. We concluded that the trans-18:1 acids in partially hydrogenated soybean oil have a more inhibitory effect than saturated acids on EFA metabolism, even in the presence of adequate amounts of essential fatty acid.

The effects of partially hydrogenated marine oils on the mitochondrial function and membrane phospholipid fatty acids in rat heart

The influence of dietary partially hydrogenated marine oils containing docosenoic acid on rat heart mitochondrial membrane phospholipid fatty acid composition was studied with particular reference to cardiolipin and oxidative phosphorylation. Five groups of male weanling rats were fed diets containing 20% (w/w) peanut oil (PO), partially hydrogenated peanut oil (HPO), partially hydrogenated Norwegian capelin oil (HCO), partially hydrogenated herring oil (HHO), and rapeseed oil (RSO) for 10 weeks. All the cardiac phospholipids investigated were influenced by the experimental diets. An increased amount of arachidonic acid observed in phosphatidylethanolamine (PE) after feeding partially hydrogenated oils suggests a changed regulation of the arachidonic acid metabolism in comparison with PO treatment. 22:1 originating from the dietary oils was incorporated only to a small extent into phosphatidylcholine (PC) and PE. A selective incorporation of 18:1 isomers into the 1- and 2-positions of PC and PE with respect to geometry and position of the double bond was observed. Large amounts of 18:1 trans were incorporated into the 1-position of PC and PE, irrespective of the amount of 18:2 supplemented to the diets, replacing a considerable proportion of stearic acid in this position. After feeding HHO and RSO, the content of 22:1 in mitochondrial cardiolipin of rat heart was found to be 3% (mainly cetoleic acid) and 10% (mainly erucic acid), respectively, indicating a high affinity for cis isomers of 22:1, but also a considerable resistance against incorporation of trans isomers was observed. The ability of rat cardiac mitochondria to oxidize palmitoylcarnitine and to synthesize ATP was depressed after feeding HHO and RSO. Dietary cis isomers of 22:1 seem to have a specific ability to interfere with cardiac ATP synthesis and also to alter the fatty acid composition of cardiolipin of rat heart.