Mitochondrial membrane fatty acid composition in the marmoset monkey following dietary lipid supplementation

Characterization of the n-3 polyunsaturated fatty acid enrichment in laying hens fed an extruded flax enrichment source

The time required to reach a plateau of n-3 polyunsaturated fatty acid (PUFA) concentration in plasma and egg yolk and dynamics of the enrichment process were examined in laying hens. A group of 75 Lohmann White Leghorn layers (65 wk) were fed one of 3 diets: control, moderate, or high n-3 PUFA-enriched diet for 18 d. Diets provided similar ME and CP and contained 0, 7.5%, or 15% LinPRO (source of n-3 PUFA), respectively. Prior to dietary treatment, baseline values were established for the BW, fatty acid composition in egg yolk on a whole-egg basis, and in plasma. These measurements were repeated at 6, 12, and 18 d of feeding. Enzymatic conversion rates of linolenic acid (LNA) to long-chain fatty acids were calculated. Data were analyzed with Proc Mixed of SAS, and broken stick analysis was used to determine n-3 PUFA plateau using the NLIN procedure of SAS (P < 0.05). The total egg yolk n-3 PUFA reached a plateau of 343.7 mg/egg and 272.9 mg/egg after 6.6 and 5.9 d on the high and moderate diets, respectively. In blood plasma, the n-3 PUFA concentrations reached saturation in 7.2 d with 0.93 mg/mL and 0.67 mg/mL on high and moderate diets, respectively. The transfer efficiency of total n-3 PUFA from the diet to the egg yolk was calculated as 55.6% in control birds, 30.5% in moderate birds, and 22.2% in high birds, demonstrating reduced transfer efficiency of n-3 PUFA as inclusion in the feed increases. Final egg yolk n-3 PUFA concentrations had a CV of 16.5% compared with 28.5% for plasma. After 12 d, the long-chain n-3 PUFA [eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA)] were significantly higher in egg yolk from hens on the moderate and high enriched diets compared with those from hens fed the control diet, whereas in plasma values did not differ. Broken stick analysis of egg enrichment indicated that high birds reached the target threshold of 300 mg of total n-3 PUFA/egg in 5 d. A significant increase in EPA, DPA, and DHA and reduction in arachidonic acid content in egg yolks from hens fed enriched diets compared with the control diet confirms competition for enzymes during postabsorptive modification of these fatty acids. This work contributes to the understanding of individual hen effects on n-3 PUFA absorption and the effect of level of dietary enrichment with an extruded flax product on final yolk n-3 PUFA concentration.

Endogenous red blood cell membrane fatty acids and sudden cardiac arrest

Little is known of the associations of endogenous fatty acids with sudden cardiac arrest (SCA). We investigated the associations of SCA with red blood cell membrane fatty acids that are end products of de novo fatty acid synthesis: myristic acid (14:0), palmitic acid (16:0), palmitoleic acid (16:1 n7), vaccenic acid (18:1 n7), stearic acid (18:0), oleic acid (18:1 n9), and a related fatty acid, cis-7 hexadecenoic acid (16:1 n9). We used data from a population-based case-control study where cases, aged 25 to 74 years, were out-of-hospital SCA patients attended by paramedics in Seattle, WA (n = 265). Controls, matched to cases by age, sex, and calendar year, were randomly identified from the community (n = 415). All participants were free of prior clinically diagnosed heart disease. We observed associations of higher red blood cell membrane levels of 16:0, 16:1n-7, 18:1n-7, and 16:1n-9 with higher risk of SCA. In analyses adjusted for traditional SCA risk factors and trans- and n-3 fatty acids, a 1-SD-higher level of 16:0 was associated with 38% higher risk of SCA (odds ratio, 1.38; 95% confidence interval, 1.12-1.70) and a 1-SD-higher level of 16:1n-9 with 88% higher risk (odds ratio, 1.88; 95% confidence interval, 1.27-2.78). Several fatty acids that are end products of fatty acid synthesis are associated with SCA risk. Further work is needed to investigate if conditions that favor de novo fatty acid synthesis, such as high-carbohydrate/low-fat diets, might also increase the risk of SCA.

Intracellular composition of fatty acid affects the processing and function of tyrosinase through the ubiquitin-proteasome pathway

Proteasomes are multicatalytic proteinase complexes within cells that selectively degrade ubiquitinated proteins. We have recently demonstrated that fatty acids, major components of cell membranes, are able to regulate the proteasomal degradation of tyrosinase, a critical enzyme required for melanin biosynthesis, in contrasting manners by relative increases or decreases in the ubiquitinated tyrosinase. In the present study, we show that altering the intracellular composition of fatty acids affects the post-Golgi degradation of tyrosinase. Incubation with linoleic acid (C18:2) dramatically changed the fatty acid composition of cultured B16 melanoma cells, i.e. the remarkable increase in polyunsaturated fatty acids such as linoleic acid and arachidonic acid (C20:4) was compensated by the decrease in monounsaturated fatty acids such as oleic acid (C18:1) and palmitoleic acid (C16:1), with little effect on the proportion of saturated to unsaturated fatty acid. When the composition of intracellular fatty acids was altered, tyrosinase was rapidly processed to the Golgi apparatus from the ER (endoplasmic reticulum) and the degradation of tyrosinase was increased after its maturation in the Golgi. Retention of tyrosinase in the ER was observed when cells were treated with linoleic acid in the presence of proteasome inhibitors, explaining why melanin synthesis was decreased in cells treated with linoleic acid and a proteasome inhibitor despite the abrogation of tyrosinase degradation. These results suggest that the intracellular composition of fatty acid affects the processing and function of tyrosinase in connection with the ubiquitin-proteasome pathway and suggest that this might be a common physiological approach to regulate protein degradation.

Coconut oil induces short-term changes in lipid composition and enzyme activity of chick hepatic mitochondria

We studied the short-term effects of a 20% coconut oil supplementation to the chick diet on lipid composition of liver and hepatic mitochondria, and changes that occurred in mitochondrial-associated enzymes as a result of this diet. No significant differences were observed in the lipid contents of liver when young chicks were fed the experimental diet, whereas hepatic mitochondria rapidly changed in response to this diet. Total cholesterol significantly increased in mitochondria at 24 hours of coconut oil diet feeding and decreased when dietary treatment was prolonged for 5 to 14 days. Changes in total mitochondrial phospholipids showed an inverse profile. A significant decrease in phosphatidylethanolamine and an increase in sphingomyelin were found at 24 hours. The cholesterol/phospholipid molar ratio significantly and rapidly (24 hours) increased in mitochondria from treated animals. Cytochrome oxidase activity drastically increased after 24 hours of experimental diet feeding and lowered to the control values when dietary manipulation was prolonged for 5 to 14 days. ATPase activity showed an inverse profile. Changes in cytochrome oxidase activity were parallel to changes in the cholesterol/phospholipid molar ratio, whereas changes in ATPase activity showed an inverse correlation with changes in this molar ratio. To our knowledge, this is one of the first reports on the very rapid response (24 hours) of mitochondrial lipid composition and function to saturated fat feeding.

Supplementation of coconut oil from different sources to the diet induces cellular damage and rapid changes in fatty acid composition of chick liver and hepatic mitochondria

Supplementation of 20% coconut oil from two commercial sources pharmaceutical ("Pharmacy") and cooking ("Pastry") use, to the chick diet for 14 days produced a clear damage to the hepatic mitochondria, accompanied by an accumulation of glycogen and lipid droplets in the hepatocyte cytoplasm. These effects may be accounted for the high proportion of fat supplemented to the diets (20%). Pharmacy coconut oil induced a high percentage of cellular death when administered for 14 days. Fatty acid profiles in liver and hepatic mitochondria rapidly changed (24 hr) after both coconut oils supplementation to the diet. The accumulation of shorter chain fatty acids (12:0 and 14:0) was always higher after Pharmacy than after Pastry diet feeding. This fact may contribute, at least in part, to the cellular damage mentioned above especially after Pharmacy diet feeding. Mitochondrial ratios of saturated/unsaturated and saturated/polyunsaturated fatty acids rapidly changed in parallel to these ratios in both diets. Most of the mitochondrial parameters measured tend to recuperate the control values when diets were supplied for 5-14 days. Nevertheless, the maintenance of the mentioned ratios after 14-days Pharmacy diet feeding at significantly higher levels than those observed in control, seems to suggest the lack of the homeostatic mechanism in these membranes and could be also related with the high percentage of cellular death observed after this dietary manipulation.

Effects of dietary oil related to the toxic oil syndrome on the lipids of guinea pig liver microsomes

The potential effects of oil specimens related to cases of toxic oil syndrome (TOS) on the liver microsomal lipid composition from guinea pigs were investigated. For four weeks, animals were fed diets supplemented with either "case oil" (oil related to cases of TOS) or "control oil" (oil unrelated to cases of TOS), either previously heated or not. Results were compared with those from guinea pigs fed the same diet with no oil. The administration of case oil produced changes in liver microsomal lipid composition. Statistically significant differences were also found between heated case and heated control oils. The cholesterol/phospholipid molar ratios and the major phospholipid class distribution were unaffected under these diet conditions. However, increases in the relative contents of linoleic and arachidonic acids and, simultaneously, a reduction in palmitic and palmitoleic acid levels were observed by diet effects. Heated oil administration decreased the saturated/unsaturated ratios in all cases. Our data suggest that changes observed in the fatty acid composition are attributable to the free fatty acid contents of administered oils. The toxic constituents of case oil seem to be able to alter the liver microsomal lipid composition.

The short-term effect of dietary fats on the brain fatty acid composition in rats

The effects of dietary fats on brain fatty acid composition were studied in weanling rats. Three groups of rats were fed for six days a basal diet supplemented with a 10% (w/w) of fat as coconut, olive or sunflower oil. There were no differences in the saturated and monounsaturated fatty acid content among the different groups. The more abundant polyunsaturated fatty acids were arachidonic (20:4 n-6) and docosahexaenoic (22:6 n-3) acids. No effect of the diet on their amount in brain membranes has been found. We can conclude that the brain does not modify its fatty acid composition after a short-time administration of these lipids.

Effect of a high fat diet on phospholipid class distribution and fatty acid composition in rat liver

1. Long term consumption (20 weeks) of a high fat diet (65% of the energy content as fat) rich in either saturated [30% (w/w) coconut oil] or unsaturated [30% (w/w) sunflower oil] fatty acids resulted in strikingly similar alterations in the phospholipid class distribution and fatty acid composition in the liver of male Wistar rats. 2. The effect of these two diets was compared to a control group maintained on a 2% fat diet (w/w) for the same time interval. 3. In spite of the difference in the PUFA/SFA (polyunsaturated fatty acid/saturated fatty acid) ratio between the two high fat diets (0.1, saturated fatty acid diet; 5.4, unsaturated fatty acid diet), both diets resulted in a similar PUFA/SFA ratio in liver phospholipids, a similar reduction in palmitic acid (16:0), oleic acid (18:1, n-9) and arachidonic acid (20:4, n-6) and an elevation in stearic acid (18:0), linoleic acid (18:2, n-6) and docosahexaenoic acid (22:6, n-3). 4. Further, changes in the phospholipid classes were also similarly affected by both high fat diets.

Preferential accumulation of n-3 fatty acids in the brain of chicks from eggs enriched with n-3 fatty acids

Docosahexaenoic acid (DHA) is the major polyunsaturated fatty acid in the phospholipids of brain tissue. The extent to which maternal dietary n-3 fatty acid may influence the n-3 fatty acid composition of phosphatidylethanolamine (PE) and phosphatidylcholine (PC) fractions of brain and liver tissue of progeny was investigated. Hens were fed diets containing n-9, n-3, or n-6 fatty acids. The brain tissue of the chicks from eggs enriched with n-3 fatty acids contained higher DHA, resulting in an increased C22:6 n-3:C20:4 n-6 ratio compared with chicks from eggs enriched with n-9 or n-6 fatty acids. Incorporation of C22:5 n-3, and C22:6 n-3 was mainly in the PE fraction as compared with the PC fraction of the chick brain. For chicks hatched from eggs enriched with n-9, n-3, and n-6 fatty acids, the total n-3 fatty acids in the brain PE fraction were 29.3, 41.3, and 21.9% compared with 6.7, 8.8, and 4.0% in the brain PC fraction. In contrast, the n-3 fatty acids increased evenly in phospholipid PC and PE fractions. Total amounts of PE in the brain lipids of chicks from eggs enriched with n-3 and n-6 fatty acids were 40.8 and 41.9% compared with 33.1% for chicks from eggs enriched with n-9 fatty acids. Analyses of the remaining yolk sac revealed a preferential absorption of DHA from the egg PE fraction by the developing chick.

The effect of dietary supplementation with eicosapentaenoic acid on the phospholipid and fatty acid composition of erythrocytes of marmoset

Adult male marmoset monkeys were fed eicosapentaenoic acid (20:5n-3) as the ethyl ester in diets containing either 32% (reference diet, no added cholesterol) or 7% (atherogenic diet with 0.2% added cholesterol) linoleic acid (18:2n-6) for 30 wk. No changes were seen in the level of phosphatidylcholine (PC) or phosphatidylethanolamine (PE) but minor changes were observed in both the sphingomyelin (SPM) and phosphatidylinositol plus phosphatidylserine (PI+PS) fractions of erythrocyte lipids. The extent of total n-3 fatty acid incorporation into membrane lipids was higher in atherogenic diets (polyunsaturated/monounsaturated/saturated (P/M/S) ratio 0.2:0.6:1.0) than reference diets (P/M/S ratio 1:1:1) and this was true for both PE (33.4 +/- 1.0% vs 24.3 +/- 1.1%) and PC (9.3 +/- 0.5% vs 4.9 +/- 0.3%). Although suitable controls for cholesterol effects were not included in the study, earlier results obtained with marmosets lead us to believe such effects were probably small. Regardless of basic diet (atherogenic, reference), 20:5n-3 was preferentially incorporated into PE (10.8 +/- 0.2%, 6.0 +/- 0.02%) while smaller amounts were incorporated into PC (6.9 +/- 0.4%, 3.2 +/- 0.2%). The major n-3 polyunsaturated fatty acid found in PE in response to dietary 20:5n-3 was the elongation metabolite 22:5n-3 in both the atherogenic (17.7 +/- 0.7%) and reference (14.3 +/- 1.0%) dietary groups; 22:6n-3 levels were less affected by diet (4.7 +/- 0.3% and 3.9 +/- 0.2%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Prostaglandin synthesis and fatty acid composition of phospholipids and triglycerides in skeletal muscle of chicks fed combinations of flaxseed oil and animal tallow

Chicks were fed isocaloric and isonitrogenous diets containing 6% (w/w) added fat consisting of various proportions of animal tallow and flaxseed oil (FSO). No differences among treatments were seen in growth rate, muscular deposition of protein and lipids nor in the muscle phospholipid (PL) and triglyceride (TG) contents. Prostaglandin (PG)E2 synthesis in isolated skeletal muscle was depressed significantly by feeding FSO or by treatment with naproxen (6-methoxy-alpha-methyl-2-napthaleneacetic acid), an inhibitor of PG synthesis. The changes associated with diet may be related to differences in the fatty acid composition of muscle lipids. Levels of saturated fatty acids in muscle PL and TG were relatively insensitive to dietary treatments. Monounsaturated fatty acid levels were significantly lower in the FSO-fed groups. FSO diets caused significant depression in muscle PL 20:4 omega 6 and almost completely inhibited 22:5 omega 6 incorporation. FSO diets decreased ratios of omega 6/omega 3 fatty acids and increased the unsaturation index of muscle PL. Muscles of chicks fed FSO showed increased levels of 18:3 omega 3, and of its derivatives 20:4 omega 3 and 22:5 omega 3. These results suggest that FSO inhibits PG synthesis and modifies the fatty acids of PL and TG of chick muscle. These changes may have implications for PG-dependent and/or membrane-dependent processes in muscle metabolism.

Incorporation and effects of dietary eicosapentaenoate (20:5(n-3)) on plasma and erythrocyte lipids of the marmoset following dietary supplementation with differing levels of linoleic acid

The effect of dietary eicosapentaenoic acid (EPA, 20:5(n-3), as the ethyl ester) on plasma lipid levels and the incorporation of EPA into erythrocyte and plasma lipids were investigated in the marmoset monkey. Marmosets were fed high mixed-fat diets (14.5% total fat) supplemented with or without 0.8% EPA for 30 weeks. Markedly elevated plasma cholesterol (16.4 mmol/l) was induced by an atherogenic-type diet but with EPA supplementation, plasma cholesterol increased to only 6.6 mmol/l. Plasma triacylglycerol levels were not elevated with an atherogenic type diet. Substantial EPA incorporation was evident for plasma phospholipid, triacylglycerol and cholesterol ester fractions. The proportion of docosapentaenoic acid (22:5(n-3)) but not docosahexaenoic acid (22:6(n-3)) was also elevated in these plasma lipid fractions. Greatest incorporation of EPA occurred when it was administered with an atherogenic type diet having a P:M:S (polyunsaturated:monounsaturated:saturated) fatty acid ratio of about 0.2:0.6:1.0 in comparison to the control diet of 1.0:1.0:1.0. Incorporation of EPA and 22:5(n-3)) into erythrocyte phospholipids was also apparent and this was at the expense of linoleic acid (18:2(n-6)). These results in the marmoset highlight both the cholesterol-lowering properties of EPA and the extent of its incorporation into plasma lipids and erythrocyte membrane phospholipids with far greater incorporation occurring when the level of dietary linoleic acid was reduced.

Changes in lipid composition and desaturase activities of duodenal mucosa induced by dietary fat

In the present work we have studied the effects of feeding either olive or sunflower oil on lipid composition and desaturase activities of duodenal mucosa microsomes. Duodenal microsomes prepared from dogs fed the sunflower oil diet showed higher percentages of saturated, of linoleic and of n - 3 polyunsaturated fatty acids as well as lower levels of oleic, dihomo-gamma-linolenic and arachidonic acids in phosphatidylcholine and phosphatidylethanolamine than those prepared from animals fed the olive oil diet. In sphingomyelin, the dietary supplementation did not produce significant differences between the two groups. The cholesterol/phospholipid molar ratio was higher in the sunflower oil group than in the olive oil group. The in vitro delta 9-desaturase activity was higher in microsomes from the olive oil dogs. The delta 6-desaturase activity was similar in microsomes from the two groups and lower than that found for delta 9-desaturase activity. Desaturase activities were higher in duodenal microsomes than those previously found for liver microsomes.

Changes in lipid composition of liver microsomes and fatty acyl-CoA desaturase activities induced by medium chain triglyceride feeding

Changes in fatty acid composition, microsomal delta 9- and delta 6-desaturase activities and liver contents of cholesterol and phospholipids were studied in rats fed medium chain triglyceride-supplemented diets. Weanling rats were divided into four groups and fed for three weeks a basal diet with different 10%-fat supplements: corn oil, medium chain triglyceride-corn oil, olive oil and medium chain triglyceride-olive oil. The highest relative content of saturated fatty acids corresponded to corn oil-fed animals. Both monounsaturated fatty acid content and delta 9-desaturase activity were higher in the animals fed olive oil diets than in corn oil-fed rats. The long chain polyunsaturated fatty acids of the n-3 series were increased in the olive oil and medium chain triglyceride-olive oil-fed groups probably due to the lower linoleic/alpha-linolenic ratios found in these two diets. The cholesterol/phospholipid molar ratio was unaffected by diet and the unsaturation index was only slightly changed in the four groups. Thus, some mechanism may be operative under these conditions to maintain the homeostasis of the membrane.

Tissue specific differences in the fatty acid composition of the marmoset monkey (Callithrix jacchus)

1. The possible relationship between the fatty acid composition of the adipose tissue of the marmoset monkey (Callithrix jacchus) and its dietary lipid intake was examined after a long-term feeding trial. 2. Only the proportions of stearic and linoleic acid in the adipose tissue were similar to those in the diet. The proportions of all other saturated and unsaturated fatty acid components were significantly different thus greatly reducing the potential value of this relationship in the marmoset. 3. The phospholipid fatty acid profiles of cardiac and skeletal muscle, aortae, kidney, liver, lung and brain were also compared to those of the plasma, platelets or red blood cells. 4. With the exception of the liver where the fatty acid profile is similar to that of the plasma, no clear relationships were found between the fatty acid profiles of these tissues and the components of the blood. 5. The fatty acid composition of skeletal muscle was very similar to that of the cardiac muscle of the marmoset, suggesting that muscle biopsy might be useful as an index of cardiac muscle composition.

Dietary cholesterol influences cardiac beta-adrenergic receptor adenylate cyclase activity in the marmoset monkey by changes in membrane cholesterol status

The activity of the beta-adrenergic receptor/adenylate cyclase system of the marmoset monkey heart was investigated following dietary cholesterol supplementation (0.5%). After 22 weeks, plasma cholesterol levels in the cholesterol group were more than twice that of the control group. In the cholesterol-fed group, the affinity for ICYP binding to cardiac membranes was elevated more than 2-fold, while the receptor number was decreased by 31%. Isoproterenol, norepinephrine and sodium fluoride stimulated adenylate cyclase activity was significantly higher in the cholesterol-fed group although the fold stimulation over basal levels was not affected. The most prominent change in the cardiac membrane lipids was an increase in the cholesterol to phospholipid ratio in marmoset monkeys fed cholesterol. These results indicate that in the marmoset, membrane cholesterol is an important factor in determining various properties of the cardiac beta-adrenergic receptor particularly receptor affinity which may impact on the response of the beta-adrenergic receptor/adenylate cyclase system of the heart to catecholamines. This result is in agreement with dietary fatty acid supplements designed to increase cardiac membrane cholesterol in this animal species (McMurchie, E.J. et al. (1988) Biochim. Biophys. Acta 937, 347-358). Elevated membrane cholesterol enhances beta-adrenergic receptor affinity and certain aspects of adenylate cyclase activity. This is a likely mechanism whereby atherogenic diets could promote cardiac arrhythmia in non-human primates and indeed in man.

Modification of the fatty acid composition of L1210 leukemia subcellular organelles

We have examined the extent to which it is possible to modify the fatty acid composition of subcellular organelles of L1210 leukemia cells. A polyunsaturated fatty acid, docosahexaenoic acid, or a monounsaturated fatty acid, oleic acid, were added to the culture media. After 48 hr, the cells were ruptured and the subcellular fractions isolated. Fatty acid analysis revealed that nuclei, mitochondria, plasma membranes and microsomes of the cells grown in media supplemented with docosahexaenoic acid contained increased amounts of polyenoic fatty acids compared with cells grown in oleic acid. We conclude that it is possible to experimentally modify the lipids of multiple intracellular structures of L1210 cells by the addition of fatty acids to the growth media.

Influence of diet on (n-3) and (n-6) fatty acids in monkey erythrocytes

Cynomolgus monkeys were fed oils high in linoleic acid or with half of the linoleic acid replaced by either (n-3) linolenic acid or marine fatty acids. When the diet contained similar quantities of linoleic and (n-3) linolenic acid, erythrocyte fatty acids maintained a ratio of (n-6) to (n-3) fatty acids of approximately 2:4. Fatty acids from menhaden oil enhanced the incorporation of eicosapentaenoic and docosahexaenoic acids into the monkey erythrocytes, the composition of which was not altered by additional alpha-tocopherol.

The influence of dietary lipid supplementation on cardiac beta-adrenergic receptor adenylate cyclase activity in the marmoset monkey

Dietary lipid supplements high in either saturated fat derived from sheep kidney fat or unsaturated fat derived from sunflower seed oil, and a low mixed fat reference diet were fed to marmoset monkeys for 20 months and the effects on cardiac membrane lipid composition, and myocardial catecholamine-stimulated adenylate cyclase and beta-adrenergic receptor binding activity were investigated. For cardiac membranes enriched for beta-adrenergic binding activity, the dietary lipid treatment resulted in small changes in the proportion of saturated to unsaturated fatty acids and substantial changes in the (n - 6) to (n - 3) series of unsaturated fatty acids in the membrane phospholipids. The sheep kidney fat diet increased the cholesterol-to-phospholipid ratio in cardiac membranes in comparison to the other diets. This diet also significantly elevated basal and isoproterenol-, epinephrine- and norepinephrine-stimulated adenylate cyclase activity. The value of the dissociation constant (Kd) and the receptor number (Bmax) for the binding of [125I]ICYP to the beta-adrenergic receptor was significantly reduced in marmosets fed the sheep kidney fat diet. These results suggest that dietary lipids can influence the activity of the beta-adrenergic/adenylate cyclase system of the heart. Modulation of this transmembrane signalling system may be induced by changes in the properties of the associated membrane lipids, particularly by alteration in the membrane cholesterol-to-phospholipid ratio. This effect may be limited to those animal species in which the nature of the dietary fatty acid intake may be influencing cardiac membrane cholesterol homeostasis, which is in agreement with previous results in rats following dietary cholesterol supplementation (McMurchie et al. (1987) Biochim. Biophys. Acta 898, 137-153). ICYP, (-)-iodocyanopindolol.

The interaction of dietary fatty acid and cholesterol on catecholamine-stimulated adenylate cyclase activity in the rat heart

Diets supplemented with high levels of saturated or unsaturated fatty acids supplied by addition of sheep kidney fat or sunflower seed oil, respectively, were fed to rats with or without dietary cholesterol. The effects of these diets on cardiac membrane lipid composition, catecholamine-stimulated adenylate cyclase and beta-adrenergic receptor activity associated with cardiac membranes, were determined. The fatty acid-supplemented diets, either with or without cholesterol, resulted in alterations in the proportion of the (n-6) to (n-3) series of unsaturated fatty acids, with the sunflower seed oil increasing and the sheep kidney fat decreasing this ratio, but did not by themselves significantly alter the ratio of saturated to unsaturated fatty acids. However, cholesterol supplementation resulted in a decrease in the proportion of saturated and polyunsaturated fatty acids and a dramatic increase in oleic acid in cardiac membrane phospholipids irrespective of the nature of the dietary fatty acid supplement. The cholesterol/phospholipid ratio of cardiac membrane lipids was also markedly increased with dietary cholesterol supplementation. Although relatively unaffected by the nature of the dietary fatty acid supplement, catecholamine-stimulated adenylate cyclase activity was significantly increased with dietary cholesterol supplementation and was positively correlated with the value of the membrane cholesterol/phospholipid ratio. Although the dissociation constant for the beta-adrenergic receptor, determined by [125I](-)-iodocyanopindolol binding, was unaffected by the nature of the dietary lipid supplement, the number of beta-adrenergic receptors was dramatically reduced by dietary cholesterol and negatively correlated with the value of the membrane cholesterol/phospholipid ratio. These results indicate that the activity of the membrane-associated beta-adrenergic/adenylate cyclase system of the heart can be influenced by dietary lipids particularly those altering the membrane cholesterol/phospholipid ratio and presumably membrane physico-chemical properties. In the face of these dietary-induced changes, a degree of homeostasis was apparent both with regard to membrane fatty acid composition in response to an altered membrane cholesterol/phospholipid ratio, and to down regulation of the beta-adrenergic receptor in response to enhanced catecholamine-stimulated adenylate cyclase activity.

Influence of dietary fats on blood coagulation and prostaglandin production in the common marmoset

Common marmosets were fed a standard marmoset diet (REF) or diets supplemented with 12% (wt/wt) sunflower seed oil (SSO) or sheep fat (SF) for a period of 90 weeks. The values for coagulation indices, clotting time, and Russel viper venom time were consistent with decreased thrombotic tendency of platelets from animals on the SSO diet relative to the low fat, REF diet animals, while an increased tendency to thrombosis was observed with SF-fed marmosets. The SSO- and SF-supplemented marmosets showed a significantly reduced thromboxane (TXB2) generation from platelets aggregating to collagen (ASC) relative to the REF group, while at 50 micrograms/ml ASC this difference was maintained only by the SSO group. The SF diet-fed marmosets showed a reduced prostacyclin (measured as 6-keto-PGF1 alpha) generation from incubated aorta relative to the REF or SSO-fed groups, which were not different from each other. A reduced proportion of platelet phospholipid arachidonic acid (20:4, n-6) and increased alpha-tocopherol concentration was consistent with the decreased aggregability and thromboxane generation of platelets from SSO-fed marmosets relative to the REF and SF groups. The SF diet-fed marmosets, on the other hand, showed minimal change in arachidonic acid, alpha-tocopherol or platelet reactivity from the REF group. These differing responses to dietary fats are discussed in relation to the potential for the development of thrombosis and atherosclerosis.