The Effect of Cod Liver Oil in Two Populations with Low and High Intake of Dietary Fish

ABSTRACT Two subgroups of healthy males from an inland and a coastal community in Norway with a traditionally low and high consumption of dietary fish were given a dietary supplement of 20 ml cod liver oil rich in n-3 polyunsaturated fatty acids for 3 weeks. Cod liver oil induced an increase in serum high density lipoprotein (HDL) cholesterol in men from the inland. Both groups showed a prolonged primary bleeding time, whereas platelet aggregation and thromboxane A₂ production induced by collagen were mainly unaffected. Platelet phospholipid fatty acids showed similar changes in both groups with a decrease in n-6 and an increase in n-3 polyunsaturated fatty acids. No changes were observed in total cholesterol or platelet phospholipid content. This study shows that dietary supplement with cod liver oil induces changes in serum lipids and platelets that may reduce the tendency to thrombosis both in subjects with a low and in those with a high intake of dietary fish. The effects were more pronounced in the subjects with a traditionally low fish consumption.     

Modification of the fatty acid composition of rat heart sarcolemma with dietary cod liver oil, corn oil or butter

The effect of dietary cod liver oil, corn oil or butter upon the lipid composition of cardiac sarcolemma and the activity of sarcolemmal Na+, K+ ATPase was examined in male Wistar rats. The cod liver oil diet caused significant changes in the fatty acid composition of the major phospholipids of sarcolemma, phosphatidyl choline and phosphatidyl ethanolamine. In both these phospholipids arachidonic acid, 20:4 (n - 6) was reduced by about 50% compared to rats fed butter or corn oil and was replaced by the (n - 3) fatty acids eicosapentaenoic and docosahexaenoic acids. The corn oil diet caused a significant diminution in the oleic acid content of phosphatidyl choline and elevation of linoleic acid in phosphatidyl ethanolamine. The phospholipid class composition, total phospholipid fatty acid content and cholesterol content of sarcolemma were not altered by the diets used. The activity of Na+, K+ ATPase in the cardiac sarcolemma was not significantly changed by the different diets.     

Enhanced level of n-3 fatty acid in membrane phospholipids induces lipid peroxidation in rats fed dietary docosahexaenoic acid oil

The effect of dietary docosahexaenoic acid (DHA, 22:6n-3) oil with different lipid types on lipid peroxidation was studied in rats. Each group of male Sprague-Dawley rats was pair fed 15% (w/w) of either DHA-triglycerides (DHA-TG), DHA-ethyl esters (DHA-EE) or DHA-phospholipids (DHA-PL) for up to 3 weeks. The palm oil (supplemented with 20% soybean oil) diet without DHA was fed as the control. Dietary DHA oils lowered plasma triglyceride concentrations in rats fed DHA-TG (by 30%), DHA-EE (by 45%) and DHA-PL (by 27%), compared to control. The incorporation of dietary DHA into plasma and liver phospholipids was more pronounced in the DHA-TG and DHA-EE group than in the DHA-PL group. However, DHA oil intake negatively influenced lipid peroxidation in both plasma and liver. Phospholipid peroxidation in plasma and liver was significantly higher than control in rats fed DHA-TG or DHA-EE, but not DHA-PL. These results are consistent with increased thiobarbituric acid reactive substances (TBARS) and decreased alpha-tocopherol levels in plasma and liver. In addition, liver microsomes from rats of each group were exposed to a mixture of chelated iron (Fe(3+)/ADP) and NADPH to determine the rate of peroxidative damage. During NADPH-dependent peroxidation of microsomes, the accumulation of phospholipid hydroperoxides, as well as TBARS, were elevated and alpha-tocopherol levels were significantly exhausted in DHA-TG and DHA-EE groups. During microsomal lipid peroxidation, there was a greater loss of n-3 fatty acids (mainly DHA) than of n-6 fatty acids, including arachidonic acid (20:4n-6). These results indicate that polyunsaturation of n-3 fatty acids is the most important target for lipid peroxidation. This suggests that the ingestion of large amounts of DHA oil enhances lipid peroxidation in the target membranes where greater amounts of n-3 fatty acids are incorporated, thereby increasing the peroxidizability and possibly accelerating the atherosclerotic process.     

Cod liver oil does not reduce ventricular extrasystoles after myocardial infarction

Previous work has shown that in experimental animal models a lower incidence of arrhythmias and sudden death was observed if the animals were fed cod liver oil or fish oil. After a 48-h control period starting, on average, 8 days after the onset of symptoms, 18 men who were recovering from acute myocardial infarction were given 20 ml d-1 cod liver oil for 6 weeks, either immediately after the control period, weeks 0-6 (n = 10), or during weeks 6-12 (n = 8). Forty-eight-hour Holter monitoring was carried out before cod liver oil administration and at the end of weeks 6 and 12. The eicosapentaenoic acid content of plasma phospholipids was increased by 230% during cod liver oil administration. However, no significant change was observed in the 24-h prevalence of ventricular extrasystoles or other arrhythmias during the study period. The mean ln number of ventricular extrasystoles was 2.95 +/- 0.51 (+/- SEM) during cod liver oil ingestion and 2.63 +/- 0.30 when not taking cod liver oil.     

Effects of a new fluid fish oil concentrate, ESKIMO-3, on triglycerides, cholesterol, fibrinogen and blood pressure

Eskimos have a very low incidence of cardiovascular disease, at least in part due to a high intake of n-3 fatty acids. ESKIMO-3 is a new stabilized (insensitive to oxidation) fluid fish oil concentrate, 30 ml of which contains an amount of eicosapentaenoic acid and total n-3 fatty acids equivalent to the daily intake among Eskimos. Thirty-three volunteers, healthy or with coronary artery disease, were given ESKIMO-3, at a dose of 15 or 30 ml d-1, corresponding to 2.7 or 5.4 g of eicosapentaenoic acid d-1, or placebo oil, for a period of up to 6 months. ESKIMO-3 had a pronounced dose-dependent effect on several risk factors for coronary artery disease. Intake of one tablespoon (15 ml) daily for 6 months significantly reduced levels of triglycerides (-64%), total cholesterol (-8%), plasma fibrinogen (-23%) and diastolic blood pressure (-9%). Bleeding time was unchanged. Intake of two tablespoons daily for 4 weeks increased plasma eicosapentaenoic acid levels by 490%, and decreased arachidonic acid by 20%. The HDL concentration increased by 21%. No change in the above mentioned variables was observed after intake of placebo oil.     

Altered levels of n-6/n-3 fatty acids in rat heart and storage fat following variable dietary intake of linoleic acid

Fat-supplemented dies enriched with linoleic acid by the addition of 12% w/w sunflower seed oil or proportionally reduced in linoleic acid by addition of 12% mutton fat were fed to rats for 18 months before the fatty acid composition of perirenal storage fat and myocardial membranes (phospholipids) was determined. Although the fatty acid composition of perirenal fat generally reflected that of the diet, there was an inverse relationship between the consumption of n-6 and the deposition of n-9 fatty acids. In addition, enhanced deposition of oleic acid (18:1, n-9) appears to be related to the dietary intake of stearic acid (18:0). In contrast, in myocardial membranes the n-3 polyunsaturated fatty acids are found to be increased when the intake of n-6 polyunsaturated fatty acids is reduced. This is particularly evident for docosahexaenoic acid (22:6, n-3) which is significantly increased in phosphatidylcholine, phosphatidylethanolamine, and diphosphatidylglycerol fractions of myocardial membranes, when the mutton fat diet was fed. After feeding the sunflower seed oil diet, the increased consumption of linoleic acid produced only small changes in the 18:2, n-6 content of cardiac phosphatidylcholine and phosphatidylethanolamine. These major classes of membrane phospholipids also showed only small increases in 20:4, n-6. In diphosphatidylglycerol, increased 18:2, n-6 also followed increased dietary intake, but this was not accompanied by increased 20:4, n-6. These changes in myocardial phospholipid fatty acid composition are similar to those observed after short-term feeding reported previously and confirm that changes in dietary n-6/n-3 fatty acid intake affect the fatty acid composition of both myocardial membranes and storage fat. These changes persist for the duration of the feeding period.     

Effects of Cod Liver Oil on Platelets and Coagulation in Familial Hypercholesterolemia (Type IIa)

Patients with familial hypercholesterolemia (type IIa) were given 30 ml cod liver oil (CLO) as dietary supplement daily for 6 weeks. The effects on platelets, bleeding time, coagulation and blood and platelet lipids were examined. The major findings were a reduced collagen-induced platelet aggregation and a decrease in thrombin-stimulated thromboxane B₂ generation in platelets in vitro. The primary bleeding time was not significantly prolonged. Statistically significant increase in ***eicosapentaenoic add/arachidonic acid ratios in the main platelet phospholipids were also observed. These changes did not correlate with any of the changes in platelet behavior observed after CLO intake. The serum total and HDL cholesterol and triglycerides were not altered during the trial.     

Serum enriched with n-3 polyunsaturated fatty acids inhibits procoagulant activity in endothelial cells.

Nine healthy male volunteers (mean age 24.3 years, range 21-27 years) ingested 25 ml cod liver oil (CLO) daily for 8 weeks. Blood samples were collected before and after the intervention period. A slight increase in total serum cholesterol (+ 12.2%, P less than 0.01) and high density lipoprotein cholesterol (+ 16.9%, P less than 0.01) were calculated to have a non-significant effect on the high/low density lipoprotein ratio. Polyunsaturated fatty acids in serum were displaced from the n-6 family to the n-3 family, reflected by an eight-fold increase of the eicosapentaenoic (20:5 n-3)/arachidonic (20:4n-6) acid ratio. Human umbilical vein endothelial cells were grown in a medium to which 30% sterile filtered serum, collected before and after CLO supplementation for 72 h, was added. After 2 h exposure to lipopolysaccharides the thromboplastin activity in endothelial cultures incubated with serum enriched with n-3 fatty acids was 43% lower than in cultures containing serum collected before the intervention (1.86 +/- 0.48 10(-3)/10(6) cells vs 3.26 +/- 0.85 10(-3)/10(6) cells). It is suggested that serum prepared from subjects given n-3 fatty acids may support the thromboresistence of endothelial cells.     

Comparative effects of feeding different fats on fatty acid composition of major individual phospholipids of rat hearts

Comparative effects of feeding dietary linoleic (corn oil), oleic (olive oil), alpha-linolenic (soybean oil) and polyunsaturated fatty acids (fish oil) on lipid content and fatty acid composition of major individual phospholipids of rat hearts were examined. Feeding different diets did not result in lipid accumulation in the heart. Total triglyceride, nonesterified fatty acid, cholesteryl ester and phospholipid levels of heart tissue were not affected by the type of dietary fatty acid. However, heart free cholesterol levels decreased in both animals fed the olive and the fish oil diets. The percentage of individual phospholipids, phosphatidylcholine (PC), phosphatidylethanolamine (PE) and cardiolipin (CL) did not modify by changes in the dietary fat composition. Heart tissue from animals fed on olive oil were enriched with 18:1 (n-9 + n-7) fatty acid in all phospholipid fractions. Animals fed corn oil contained higher proportions of 18:2 (n-6) for PC, PE and CL, and the ingestion of the soybean oil diet increased 18:2 (n-6) for PC and CL in the same proportion as the ingestion of the corn oil diet. The levels of 22:6 (n-3) were increased in the fish oil-fed group, accompanied by both a decrease in total (n-6) fatty acids and an increase in total (n-3) fatty acids in the three phospholipid fractions. The 20:5 (n-3) was only detected in these animals. These results show that olive oil is as effective as fish oil in reducing heart cholesterol content and support earlier works suggesting the role of fish oil in preventing cardiovascular disease.     

Influence of different supplements of N-3 polyunsaturated fatty acids on blood and tissue lipids in rats receiving high intakes of linoleic acid

The influence of a supplement of linseed oil (LO), rich in linoleic acid (C18:3,n-3), was compared with one of fish oil (MaxEPA) rich in eicosapentaenoic acid (C20:5,n-3) and docosahexaenoic acid (22:6,n-3) on blood and tissue lipids in weanling rats receiving a high intake of linoleic acid. Both the LO and the MaxEPA supplement decreased plasma cholesterol concentrations. The MaxEPA supplement but not the linseed oil supplement also decreased the concentrations of plasma triglycerides and HDL cholesterol. The proportion of C20:5,n-3 was markedly increased in the platelet and erythrocyte lipids by the MaxEPA supplement but not in tissue lipids. However, the increase in the proportion of C20:5,n-3 in the platelet was small compared with other studies. Both supplements led to an increase in the proportion of C22:6,n-3 in blood and tissue lipids but the MaxEPA supplement was more potent than the LO supplement. The most marked change was observed in the heart lipids. These changes were accompanied by reciprocal changes in the proportions of arachidonic, adrenic and docosapentaenoic acid.     

Influence of alpha-linolenic acid and fish-oil on markers of cardiovascular risk in subjects with an atherogenic lipoprotein phenotype

We tested the hypothesis that dietary alpha-linolenic acid (ALA) can exert effects on markers of cardiovascular risk similar to that produced by its longer chain counterparts in fish-oil. A dietary intervention study was undertaken to examine the effects of an ALA-enriched diet in 57 men expressing an atherogenic lipoprotein phenotype (ALP). Subjects were randomly assigned to one of three diets enriched either with flaxseed oil (FXO: high ALA, n = 21), sunflower oil (SO: high linoleic acid, n = 17), or SO with fish-oil (SOF n = 19) for 12 weeks, resulting in dietary intake ratios of n-6:n-3 PUFA of 0.5, 27.9 and 5.2, respectively. The relative abundance of ALA and EPA in erythrocyte membranes increased on the FXO diet (p < 0.001), whereas both EPA and DHA increased after fish-oil (p < 0.001). There were significant decreases in total plasma cholesterol within (FXO -12.3%, p = 0.001; SOF -7.6%, p = 0.014; SO -7.3%, p = 0.033) and between diets (p = 0.019), and decreases within diets after 12 weeks for HDL cholesterol on flaxseed oil (FXO -10%, p=0.009), plasma TG (-23%, p < 0.001) and small, dense LDL (-22% p = 0.003) in fish-oil. Membrane DHA levels were inversely associated with the changes in plasma TG ( p= 0.001) and small, dense LDL (p<0.05) after fish-oil. In conclusion, fish-oil produced predictable changes in plasma lipids and small, dense LDL (sdLDL) that were not reproduced by the ALA-enriched diet. Membrane DHA levels appeared to be an important determinant of these fish-oil-induced effects.     

Effects of dietary alpha- and gamma-linolenic acid on lipid metabolism in young and adult rats

The effect of age on lipid metabolism was studied in rats fed diets containing safflower oil (SFO, 78% linoleic acid), evening primrose oil (EPO, 9.4% gamma-linolenic acid and 70% linoleic acid) or the mixture of safflower and linseed oil (SLO, 10.2% alpha-linolenic acid and 68% linoleic acid). The activity of hepatic HMG-CoA reductase declined with age in all groups. In adult rats, the reductase activity was high in the EPO group and low in the SLO group. The activity of hepatic cholesterol 7 alpha-hydroxylase was independent of the diet or age. Hepatic delta 6-desaturase activity was low in adult rats fed EPO. In liver microsomal phospholipids, the percentage of 22:5 n-6 decreased while that of 22:6 n-3 increased with age. The ratio of linoleate metabolites to linoleate was high in the EPO group and low in the SLO group. Liver and serum cholesterol increased with age only in rats fed the SLO diet. Thus, the results indicated an enhanced susceptibility to dietary fats with age.     

Comparative changes in the fatty-acid composition of rat cardiac phospholipids after long-term feeding of sunflower seed oil- or tuna fish oil-supplemented diets

The fatty-acid composition of rat heart phospholipids was examined after long-term, i.e. more than 12 months, feeding of diets supplemented with n-6 fatty acids as sunflower seed oil (SSO), or n-3 fatty acids as tuna fish oil (TFO) which is a particularly rich source of docosahexenoic acid (DHA). Although some small changes occurred in the relative proportions of palmitic and stearic acids and in the ratio of total saturates to total unsaturates, the most important changes were in the relative proportions of 18:2 n-6 and 20:4 n-6 to 20:5 n-3 and 22:6 n-3. In general, the n-6/n-3 ratio of phosphatidylcholine (PC), phosphatidylethanolamine (PE) and diphosphatidyl glycerol (DPG) was altered in favour of the family of fatty acids administered, although the proportions of the individual long-chain polyunsaturated fatty acids which contributed to this ratio varied from one class of phospholipids to another. In cardiac PC and PE, feeding TFO supplements reduced the proportions of arachidonic acid (AA) and significantly elevated (p less than 0.01) the proportions of DHA but produced relatively little change in those of eicosapentenoic acid (EPA). In DPG, feeding TFO led to a significant increase in the proportion of AA as well as an increase in DHA. The level of EPA was relatively low in PC, PE and DPG even after TFO feeding and never reached comparable levels with that of either AA or DHA. Nevertheless the n-6/n-3 ratio in all these classes of major cardiac phospholipids was significantly reduced by feeding TFO compared to the SSO diet or the commercial rat chow (CC) reference group. In contrast to the reports of other workers who have studied the fatty-acid composition of platelet membranes after feeding various fish oil supplements, in the rat heart the major effect of tuna fish oil is an increase in the proportion of DHA rather than EPA in the cardiac phospholipids.     

Influence of different dietary fatty acid sources on erythrocyte lipids and plasma and liver essential fatty acids in hamsters fed ethanol

Hamsters fed ethanol were given three different dietary sources of essential fatty acids; safflower oil, evening primrose oil (both mainly n-6 fatty acids) or linseed oil (mainly n-3 fatty acids). After 7 weeks, plasma, erythrocyte and liver lipids and fatty acids were analyzed. Plasma and liver lipids were not significantly different in the ethanol-fed hamsters compared to the controls. Erythrocyte total phospholipid was increased only in the ethanol-fed groups given n-6 but not n-3 fatty acids. Some fatty acid changes induced by ethanol were predictable, e.g. lower 20:4 n-6 in hamsters fed n-6 fatty acids, but others were not predictable, e.g. higher 22:6 n-3 in all the ethanol-fed groups. The effect of ethanol on hamster lipids and fatty acid composition appears dependent on the predominant class of dietary fatty acids.     

The antihypertensive effect of dietary supplementation with a 6-desaturated essential fatty acid concentrate as compared with sunflower seed oil.

There is increasing evidence that the type of fat in the diet may play a role in the control of blood pressure and development of hypertension. The purpose of the present study was to investigate the effect of a concentrated preparation of the 6-desaturated essential fatty acids gamma-linolenic acid (C18:3n-6), eicosapentaenoic acid (C20:5n-3) and docosahexaenoic acid (C22:6n-3) on individuals with raised BP. Eighteen volunteers from our College staff with elevated BP on several occasions but otherwise healthy, were divided into two groups following a two-week baseline period. One group received 4g sunflower seed oil daily and the other 4g of an oil preparation rich in C18:3n-6, C20:5n-3 and C22:6n-3 for six weeks. Major measurements included BP and fatty acids in phospholipids and cholesteryl esters. Dietary intakes and urinary fluid and electrolyte excretion were also monitored during baseline and intervention periods. The subjects' office diastolic BP showed a significantly greater effect of the concentrate over the sunflower seed oil, both overall (P = 0.03) and in interaction with time (P = 0.012). Fatty acids in plasma cholesteryl esters underwent mild alterations following the administration of the concentrate. There were no important changes in nutrient intakes or in sodium, potassium and fluid excretion during the trial period.     

Plasma lipid levels and platelet and neutrophil function in patients with vascular disease following fish oil and olive oil supplementation.

This double-blind study was designed to examine and compare the effects of supplementing the existing diet with fish oil or olive oil on lipids and cell function in patients with peripheral vascular disease. Thirty-two patients with symptomatic and angiographically demonstrated peripheral vascular disease were screened, matched, and randomly allocated to take either 15 g/d fish oil or olive oil for 4 weeks. Fish oil reduced serum triglyceride levels by 26%, but increased total cholesterol levels due to a significant increase in both low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein-2 cholesterol (HDL2-C). There was a nonsignificant decrease in HDL3-C levels. Olive oil reduced total cholesterol levels, accountable to a significantly decrease in LDL-C levels. Serum thromboxane B2 (TXB2) levels remained unchanged following fish oil, but were significantly increased by olive oil. Urinary excretion of TXB2 and 6-keto-PGF1 alpha was unaffected by either oil supplement. Platelet aggregation, which was measured in platelet-rich plasma in response to two doses of collagen or platelet-activating factor (PAF), was significantly reduced after fish oil, but was increased by olive oil. Following fish oil, there was a significant increase in eicosapentaenoic acid (EPA, 20:5) and docosahexaenoic acid (DHA, 22:6) levels and a decrease in arachidonic acid content of platelet phospholipids. The platelet fatty acid composition after olive oil was unchanged. Fish oil decreased neutrophil leukotriene B4 (LTB4) generation following calcium ionophore stimulation by 33%, while leukotriene B5 levels increased significantly. Neutrophil PAF production and plasma lyso-PAF were unaffected by either oil.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dietary N-3 polyunsaturated fatty acids decrease biliary cholesterol saturation in gallstone disease.

Because fatty acid composition of biliary phospholipids influences cholesterol secretion into bile, we investigated whether replacement of n-1 monounsaturated or n-6 polyunsaturated fatty acids with n-3 polyunsaturated fatty acids in biliary phosphatidylcholines reduces supersaturation with cholesterol and prevents precipitation of cholesterol crystals in bile of gallstone patients. Seven patients with radiolucent gallstones in functioning gallbladders were studied before (control) and after 5 wk of dietary supplementation with marine fish oil (11.3 gm/day = 3.75 gm n-3 polyunsaturated fatty acids/day). Duodenal bile was collected for analysis during intravenous infusion of cholecystokinin. Gallbladder emptying in response to cholecystokinin was comparable before and during intake of n-3 polyunsaturated fatty acids. Intake of n-3 polyunsaturated fatty acids increased (p less than 0.001) the fractions of eicosapentaenoic and docosahexaenoic acids and decreased the fractions of linoleic (p less than 0.001) and arachidonic acids (p less than 0.02) in biliary phospholipids. Concomitantly, the molar ratio of cholesterol to phospholipids decreased (-19%; p less than 0.05). As a consequence, the cholesterol saturation index was reduced by -25% (p = 0.01), from 1.60 +/- 0.44 to 1.24 +/- 0.38. However, in vitro nucleation time of duodenal bile was not prolonged. The decrease in cholesterol saturation was not sufficient to prevent nucleation of cholesterol crystals in bile of gallstone patients. In conclusion, our data suggest that cholesterol saturation can be influenced by the fatty acid composition of the phosphatidylcholines secreted in bile.     

Effect of dietary cholesterol on the release of prostacyclin from the mesenteric vascular bed in diabetic rat

Streptozotocin-induced diabetic female rats and age-matched control rats were fed a regular chow with or without the addition of 1% cholesterol in the diet. The release of 6-keto-PGF1 alpha, a prostacyclin metabolite, from the mesenteric vascular bed was significantly increased in diabetic rats. The production of PGI2 in diabetic rats was significantly reduced whereas that in the control was not affected by cholesterol feeding. The examination of the fatty acid composition of phospholipids from the mesenteric vascular bed indicated that proportions of stearic (18:0), linoleic (18:2n-6) and dihomo-gamma-linolenic (20:3n-6) acids were higher whereas those of oleic (18:1n-9) was lower in diabetic rats than those in the controls. Cholesterol feeding had no significant effect on the levels of arachidonic acid (20:4n-6) in the controls but it significantly decreased those in diabetic rats. It is suggested that cholesterol feeding lowers the release of PGI2 from the mesenteric vascular bed possibly because of a reduced level of arachidonic acid, the major precursor for prostaglandin synthesis. This could be due to an impairment of delta-5 desaturase.     

Fatty acid alterations in liver peroxisomes from n-3-deficient mice

A diet deficient in n-3 fatty acids dramatically reduces docosahexaenoic acid (4.8-fold) and 20:5n-3 content in murine total peroxisomal phospholipids, and conversely increases 22:5n-6 (17.1-fold) and also, to a lesser extent, 20:4n-6. This was also found in purified phosphatidylethanolamine and phosphatidylcholine. After changing the non-deficient diet (containing alpha-linolenic acid, ALA) to a deficient one (deficient in ALA), it took a very long time for docosahexaenoic acid concentration in peroxisomes to decline (>5 months). In contrast, after changing the deficient to a non-deficient diet, time to complete recovery was more rapid (3 weeks). Changes in 20:5n-3, 22:6n-3 and 20:4n-6 were generally stabilized within 2-4 weeks. Dietary n-3 fatty acids control the fatty acid composition of peroxisomal membranes, and thus possibly affect some of their functions.     

Effects of saturated and unsaturated fatty acids on estimated desaturase activities during a controlled dietary intervention

Background and aimsDirect measurement of desaturase activities are difficult to obtain in humans. Consequently, surrogate measures of desaturase activity (estimated desaturase activities) have been frequently used in observational studies, and estimated Δ⁹- (or stearoyl-CoA-desaturase (SCD)), Δ⁶- and Δ⁵-desaturase activities have been associated with cardiometabolic disease. Data on how the markers of desaturase activities are modified by changes in dietary fat quality are lacking and therefore warrant examination.Methods and resultsIn a two-period (three weeks) strictly controlled cross-over study, 20 subjects (six women and 14 men) consumed a diet high in saturated fat (SAT-diet) and a rapeseed oil diet (RO-diet), rich in oleic acid (OA), linoleic acid (LA) and α-linolenic acid (ALA). Estimated desaturase activities were calculated as precursor to product FA ratios in serum cholesteryl esters and phospholipids. The estimated SCD [16:1 n-7/16:0] and Δ⁶-desaturase [20:3 n-6/18:2 n-6] was significantly higher while Δ⁵-desaturase [20:4 n-6/20:3 n-6] was significantly lower in the SAT-diet (P < 0.001 for all), compared to the RO-diet. The serum proportions of palmitic, stearic, palmitoleic and dihomo-γ-linolenic acids were significantly higher in the SAT-diet while the proportions of LA and ALA were significantly higher in the RO-diet.ConclusionThis is the first study to demonstrate that surrogate measures of desaturase activities change as a consequence of an alteration in dietary fat quality. Both the [16:1/16:0]-ratio and 16:1 seem to reflect changes in saturated fat intake and may be useful markers of saturated fat intake in Western countries.