Fish oil administration as a supplement to a corn oil containing diet affects arterial prostacyclin production more than platelet thromboxane formation in the rat

The administration to male rats of 5 en % fish oil (FO) as supplement to a diet containing 5 en % corn oil (CO), selectively and markedly decreased arterial parameters (6-keto-PGF1 alpha formation and platelet antiaggregatory activity) assessed in isolated aortic segments perfused with autologous platelet rich plasma (PRP). Platelet parameters (ADP-induced aggregation, TxB2 formation in thrombin-stimulated PRP and sensitivity to exogenous PGI2) were instead minimally affected. Eicosapentaenoic acid (EPA, 20:5 n-3) did not accumulate in plasma, platelet and aorta lipids and arachidonic acid (AA, 20:4 n-6) levels declined markedly only in the plasma compartment. When FO was given alone at the same 5 en % level, both arterial and platelet parameters were similarly affected. EPA accumulated in plasma cholesterol esters and was present in appreciable concentrations also in platelets and aortic walls. AA levels declined markedly in plasma lipids and appreciably also in platelet and aorta lipids. It is concluded that a) arterial and platelet parameters are differentially affected by FO administration depending upon the presence of n-6 polyunsaturated fatty acids in the diet, b) 6-keto-PGF1 alpha production by arterial tissue does not seem to be related to changes of PG precursor fatty acid levels in the phospholipid fraction.     

Fish oil administration as a supplement to a corn oil containing diet affects arterial prostacyclin production more than platelet thromboxane formation in the rat

The administration to male rats of 5 en % fish oil (FO) as supplement to a diet containing 5 en % corn oil (CO), selectively and markedly decreased arterial parameters (6-keto-PGF_1α formation and platelet antiaggregatory activity) assessed in isolated aortic segments perfused with autologous platelet rich plasma (PRP). Platelet parameters (ADP-induced aggregation, TxB₂ formation in thrombin-stimulated PRP and sensitivity to exogenous PGI₂) were instead minimally affected. Eicosapentaenoic acid (EPA, 20:5 n-3) did not accumulate in plasma, platelet and aorta lipids and arachidonic acid (AA, 20:4 n-6) levels declined markedly only in the plasma compartment. When FO was given alone at the same 5 en % level, both arterial and platelet parameters were similarly affected. EPA accumulated in plasma cholesterol esters and was present in appreciable concentrations also in platelets and aortic walls. AA levels declined markedly in plasma lipids and appreciably also in platelet and aorta lipids. It is concluded that a) arterial and platelet parameters are differentially affected by FO administration depending upon the presence of n-6 polyunsaturated fatty acids in the diet, b) 6-keto-PGF_1α production by arterial tissues does not seem to be related to changes of PG precursor fatty acid levels in the phospholipid fraction.     

Adrenergic mechanisms in control of plasma lipid concentrations.

The mechanisms of the changes in plasma lipids concentrations observed after beta-blockade were examined in 53 patients with hypertension receiving treatment with atenolol, metoprolol, propranolol, and oxprenolol in a randomised cross-over trial. Significant increases in mean plasma total and very-low-density lipoprotein (VLDL) triglyceride and reductions in high-density lipoprotein (HDL) cholesterol and free fatty acids concentrations wer observed with all four drugs, the increase in plasma triglyceride concentration being greatest after propranolol and oxprenolol. No significant changes were observed in total of LDL cholesterol concentrations, but HDL:LDL ratios and HDL cholesterol as a proportion of total cholesterol fell significantly. Thus plasma lipid concentrations should be monitored after three to six months of long-term treatment. Changes in triglyceride, HDL cholesterol and free fatty acid concentrations were associated with a highly significant reduction in clearance of soya oil (Intralipid) in 25 patients studied but were unrelated to changes in blood pressure. The fall in HDL cholesterol and rise in free fatty acid concentrations were significantly less in those with initially reduced HDL cholesterol or raised free fatty acid concentrations respectively. It is proposed that unopposed alpha stimulation inhibits lipoprotein lipase with a subsequent rise in plasma triglyceride and fall in HDL cholesterol concentration. Analysis of the relation between pretreatment concentrations and subsequent changes suggests that excessive alpha stimulation may impair production of HDL cholesterol in those with low HDL cholesterol concentrations before treatment. Subtle catecholamine-mediated changes in plasma lipid concentrations might provide a mechanism for the relation between stress and the development of cardiovascular events.     

Omega-3 fatty acids increase the arachidonic acid content of liver cholesterol ester and plasma triacylglycerol fractions in the rat.

Recent studies have demonstrated that dietary fish oils rich in eicosapentaenoic acid (C20:5,omega 3) lower the content of arachidonic acid and its metabolites in plasma and tissue phospholipids. The present study examined the fatty acid composition of cholesterol ester and triacylglycerol fractions from plasma and livers of rats fed diets enriched with saturated fatty acids (beef tallow), alpha-linolenic acid (linseed oil) or eicosapentaenoic acid (fish oil). Feeding diets containing linseed oil or fish oil for 28 days increased arachidonic acid (C20:4,omega 6) levels in the cholesterol ester fraction of liver and in the triacylglycerol fraction of the plasma lipids. Plasma cholesterol esters were depleted of C20:4,omega 6 after feeding of the diet containing either linseed oil or fish oil. The changes in C20:4,omega 6 content cannot be explained by alterations in cholesterol ester or triacylglycerol pools of plasma and liver. These results suggest that the decrease in phospholipid C20:4,omega 6 content generally observed after fish oil consumption may be partly due to a shift of C20:4,omega 6 from phospholipid to the triacylglycerol and/or cholesterol ester pools in the same tissue. Triacylglycerols and cholesterol esters may therefore play a buffering role in the homeostatic maintenance of tissue phospholipid levels of arachidonic acid.     

Effects of dietary polyunsaturated fatty acid on platelet aggregation in rats

In the present study, we changed the fatty acid profile in blood and platelet membranes by dietary manipulation, and examined the effect on platelet aggregation in rats. Fifty-five rats were divided into five groups and fed for 56 days with 1% cholesterol and different types of fatty acid-rich diets: basal, lard, lard + fish oil, soybean oil, and soybean oil + fish oil. a decrease in serum arachidonic acid (20:4, omega-6, AA) and an increase in serum eicosapentaenoic acid (20:5, omega-3, EPA) were found in all experimental dietary groups fed with refined fish oil. Similar changes in the polyunsaturated fatty acids were also found in the platelet membrane phospholipids. Platelet aggregation, quantitated by the slope and height of the aggregation curve induced by different concentrations of ADP in a platelet aggregometer, was inhibited in all groups fed with refined fish oil. This inhibition of platelet aggregation may be related to an increase in the ratio of EPA and AA in the platelet membrane phospholipids after dietary manipulation. The differences in the platelet aggregation and thromboxane B2 (TXB2) concentration between the lard and the lard + fish oil groups were more profound than that between the soybean oil and the soybean oil + fish oil group. However, the malondialdehyde (MDA) concentration revealed no significant differences between the five groups.     

Cholesterol-induced stimulation of platelet aggregation is prevented by a hempseed-enriched diet

Hypercholesterolemia indirectly increases the risk for myocardial infarction by enhancing the ability of platelets to aggregate. Diets enriched with polyunsaturated fatty acids (PUFAs) have been shown to reduce the detrimental effects of cholesterol on platelet aggregation. This study investigated whether dietary hempseed, a rich source of PUFAs, inhibits platelet aggregation under normal and hypercholesterolemic conditions. Male New Zealand white rabbits were fed one of 6 dietary interventions: regular control diet (RG); control diet + 10% hempseed (HP); control diet + 10% partially delipidated hempseed (DHP); control diet + 0.5% cholesterol (OL); control diet + 0.5% cholesterol + 10% hempseed (OLHP); control diet + 5% coconut oil (CO). After 8 weeks, blood was collected to measure ADP- and collagen-induced platelet aggregation and plasma levels of fatty acids, cholesterol, and triglycerides. The hempseed-fed animals (HP and OLHP) displayed elevated plasma levels of PUFAs and a prominent enhancement in 18:3n-6 (gamma-linolenic acid, GLA) levels, a unique PUFA found in hempseed. The cholesterol-supplemented groups (OL and OLHP) had significantly elevated plasma levels of cholesterol and triglycerides, but platelet aggregation was significantly augmented only in the OL group. The addition of hempseed to this diet (OLHP) normalized aggregation. The direct addition of GLA to the OL platelet samples blocked the cholesterol-induced stimulation of platelet aggregation. The results of this study demonstrate that when hempseed is added to a cholesterol-enriched diet, cholesterol-induced platelet aggregation returns to control levels. This normalization is not due to a reduction in plasma cholesterol levels, but may be partly due to increased levels of plasma GLA.     

The cumulative dose response effect of eicosapentaenoic and docosahexaenoic acid on blood pressure, plasma lipid profile and diet pattern in mild to moderate essential hypertensive black patients

In this study eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were given in a cumulative manner, every 6 weeks, starting with 10 mg, then 100 mg, 1000 mg and 10,000 mg EPA daily to mild to moderate essential hypertensive black patients. The corresponding DHA doses were 3, 33, 333 and 3333 mg. A control group was given olive oil as placebo for the entire 24 weeks. The placebo group had lower diastolic and systolic blood pressures after 24 weeks than the EPA and DHA group. No effect was seen on plasma triglycerides, cholesterol, HDL-cholesterol and gamma-glutamyltranspeptidase at any stage of the trial. In the EPA group plasma free-EPA increased significantly from 1000 mg onwards and plasma free-arachidonic acid (AA) decreased after 1000 mg EPA. No other plasma free essential fatty acid changed during the trial, although the HDL:cholesterol increased slightly but non-significantly with an increase in EPA and DHA. No significant changes in diet pattern or body mass was observed. It is therefore concluded that EPA and DHA supplementation had no beneficial effects in mild to moderate essential hypertensive black patients except for a lowering of plasma AA.     

Effects of a prudent diet containing either lean beef and mutton or fish and skinless chicken on the plasma lipoproteins and fatty acid composition of triacylglycerol and cholesteryl ester of hypercholesterolemic subjects

In this two-phase crossover study, 39 hypercholesterolemic subjects followed a prudent diet with either lean red meat or fish and skinless chicken (treatment groups), and 13 subjects (reference group) followed their habitual diet. Fasting blood samples were analyzed for plasma total cholesterol, triacylglycerol (TAG), high density lipoprotein cholesterol (HDL-C), low density lipoprotein one- and two-cholesterol, apolipoprotein-B, very low density lipoprotein cholesterol, and very low density lipoprotein TAG, and fatty acid composition of plasma TAG and cholesteryl ester (CE). Body mass and blood pressure were determined. Seven-day dietary records were kept once at baseline and twice during the treatment periods. Significant differences were observed in dietary intake between the baseline and treatment diets and between the two treatment diets. HDL-C (P < 0.05) and diastolic blood pressure (P < 0.01) were higher in patients on the red meat diet than in those on the chicken-fish diet. No other significant differences in lipoproteins were observed between the effects of the two treatment diets. The linoleic acid (%), eicosapentaenoic acid (%), and the eicosapentaenoic acid/arachidonic acid ratios in TAG and CE were higher (P < 0.01) in subjects on the chicken-fish diet than in those on the red meat diet. In conclusion, this study showed that the effect of two lipid-lowering diets containing either lean red meat or skinless chicken and fish on the atherogenic lipoproteins did not differ significantly. A prudent diet with skinless chicken and fish, however, had a more favorable effect on the fatty acid composition of the plasma TAG and the CE than did the lean red meat diet.     

Dietary fish oils containing eicosapentaenoic acid and the prevention of atherosclerosis and thrombosis.

Recent epidemiologic studies have shown that rates of cardiovascular disease are lower in populations such as the Greenland Eskimos than in those that do not eat seafood, even though the levels of dietary fat intake are often similar. Dietary fish oils are rich in eicosapentaenoic acid (EPA), a polyunsaturated fatty acid of the omega-3 series. EPA has been shown to prolong bleeding time and to decrease platelet aggregation and blood viscosity. EPA inhibits the production of prostaglandins from endogenous arachidonic acid, which is associated with the formation of thromboxane A2 and may also dampen cyclo-oxygenase and lipoxygenase metabolites involved in mediating endothelial cell proliferation. Dietary fish oils are now available in the form of EPA-enriched capsules. Short-term trials in humans have shown that EPA significantly reduces the levels of plasma triglycerides and may increase the levels of high-density lipoproteins; however, no consistent effect on serum cholesterol levels has been shown. The results of evaluations of EPA''s use in patients with renal disorders, mild hypertension, inflammatory disorders or hyperlipidemia have been promising. On the basis of the epidemiologic and biologic evidence dietary fish oils warrant further study in extensive clinical trials.     

Echium oil reduces plasma lipids and hepatic lipogenic gene expression in apoB100-only LDL receptor knockout mice

We tested the hypothesis that dietary supplementation with echium oil (EO), which is enriched in stearidonic acid (SDA; 18:4 n-3), the product of Delta-6 desaturation of 18:3 n-3, will decrease plasma triglyceride (TG) concentrations and result in conversion of SDA to eicosapentaenoic acid (EPA) in the liver. Mildly hypertriglyceridemic mice (apoB100-only LDLrKO) were fed a basal diet containing 10% calories as palm oil (PO) and 0.2% cholesterol for 4 weeks, after which they were randomly assigned to experimental diets consisting of the basal diet plus supplementation of 10% of calories as PO, EO or fish oil (FO) for 8 weeks. The EO and FO experimental diets decreased plasma TG and VLDL lipid concentration, and hepatic TG content compared to PO, and there was a significant correlation between hepatic TG content and plasma TG concentration among diet groups. EO fed mice had plasma and liver lipid EPA enrichment that was greater than PO-fed mice but less than FO-fed mice. Down-regulation of several genes involved in hepatic TG biosynthesis was similar for mice fed EO and FO and significantly lower compared to those fed PO. In conclusion, EO may provide a botanical alternative to FO for reduction of plasma TG concentrations.     

A diet rich in (n-3) fatty acids increases peroxisomal beta-oxidation activity and lowers plasma triacylglycerols without inhibiting glutathione-dependent detoxication activities in the rat liver

By using comparisons with a safflower oil diet (15% w/w) and a control, low-fat diet, the ability of a fish oil diet (15% MaxEPA) rich in the (n-3) fatty acids, eicosapentaenoic acid and docosahexaenoic acid, to alter hepatic activities has been determined in adult, male rats. Compared with the safflower diet, treatment for 2 weeks with the fish oil diet caused significant increases in the ratio of liver weight/body weight and the specific activities in liver homogenates of peroxisomal enzymes fatty acyl-CoA oxidase (263%) and catalase (149%) and caused a significant lowering of plasma triacylglycerol levels. Fish oil diets rich in (n-3) fatty acids should thus be placed in the category of hypotriglyceridemic agents which stimulate peroxisomal beta-oxidation activity. In contrast to the effects seen with the other hypotriglyceridemic, peroxisomal proliferating agents such as clofibrate, hepatic glutathione peroxidase and glutathione S-transferase activities are unchanged or are increased rather than inhibited with the fish oil diet.     

Comparison of effects of dietary saturated, monounsaturated, and polyunsaturated fatty acids on plasma lipids and lipoproteins in man

Twenty patients consumed a liquid diet in which the predominant fatty acids were either saturated (Sat), monounsaturated (Mono), or polyunsaturated (Poly). The fats in these three diets comprised 40% of total calories and consisted of palm oil, high-oleic safflower oil, and high-linoleic safflower oil, respectively. During the third and fourth week of each dietary period, multiple samples of blood were taken and were analyzed for plasma total cholesterol (TC), triglycerides (TG), and cholesterol in lipoprotein fractions (VLDL-C, LDL-C, and HDL-C). Twelve of the patients had normal TG levels; in these patients, both Mono and Poly diets caused statistically significant and equal lowerings of plasma LDL-C, but the Poly diet lowered HDL-C levels more frequently than did the Mono diet. Neither diet changed the level of plasma TG. The proportions of total protein and the various lipid components in isolated fractions (VLDL, IDL, LDL, HDL) were not altered by the two diets. Eight patients had hypertriglyceridemia; these individuals showed considerable variability in response to Mono and Poly diets. Although there was a trend towards reductions in TC and LDL-C levels by both types of unsaturated fats, the changes were inconsistent; furthermore, HDL-C concentrations were low on the Sat diet and were unaffected by either the Mono or the Poly diet. The results of this study show that oleic acid is as effective as linoleic acid in lowering LDL-C levels in normo-triglyceridemic patients, and oleic acid seemingly reduces HDL-C levels less frequently than does linoleic acid. Neither type of unsaturated fat had striking effects on lipoprotein levels of hypertriglyceridemic patients.     

Effect of age on the modification of rat plasma lipids by fish and soybean oil diets

The effects of sardine and soybean oils on plasma lipids have been studied in young and aged rats. Plasma cholesterol and bile acids of aged rats fed on a sardine oil diet decreased to a greater degree than those of young rats. Cholesterol, bile acids and phospholipids of the soybean oil diet group decreased only in aged rats. Increases in plasma eicosapentaenoic (sardine) and linoleic (soybean) acid levels of aged rats were observed to be greater than those of young rats. These results indicate that the age enhances the effects of fish and soybean oils on plasma lipids by suppressing their characteristic fatty acid metabolism.     

Physiological effects of a fish oil supplement on captive juvenile tuatara (Sphenodon punctatus)

Tuatara (Sphenodon, Order Sphenodontia) are rare New Zealand reptiles whose conservation involves captive breeding. Wild tuatara eat seabirds, which contain high levels of the long-chain n-3 polyunsaturated fatty acids (PUFAs) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These fatty acids are absent from the captive diet, and consequently, plasma fatty acid composition of wild and captive tuatara differs. This study investigated the effects of incorporating EPA and DHA into the diet of captive juvenile tuatara (Sphenodon punctatus) in an attempt to replicate the plasma fatty acid composition of wild tuatara. Tuatara receiving a fish oil supplement containing EPA and DHA showed overall changes in their plasma fatty acid composition. Phospholipid EPA and DHA increased markedly, reaching 10.0% and 5.9 mol%, respectively, by 18 mo (cf. 相似文献   

Effect in the cow of intraruminal infusions of volatile fatty acids and of lactic acid on the secretion of the component fatty acids of the milk fat and on the composition of blood

1. The effects in the cow of intraruminal infusions of acetic acid, propionic acid or butyric acid on the secretion of the component fatty acids of the milk fat, and of these acids and of lactic acid on the composition of the blood plasma of the jugular vein, have been studied. 2. The infusion of acetic acid or butyric acid increased the yield of the C₄–C₁₆ acids of milk fat but decreased the yield of C₁₈ acids. The infusion of propionic acid decreased the yields of all major component acids except palmitic acid and possibly lauric acid. 3. The changes in the concentrations in blood plasma of glucose and of ketone bodies were consistent with the glucogenic effect of propionic acid and the ketogenic effects of butyric acid and acetic acid. The effects of lactic acid were not consistent from cow to cow. Only with the infusion of acetic acid was a significant increase in the concentration of total volatile fatty acids in blood plasma found. Infusions of butyric acid and of propionic acid tended to depress the concentration of citric acid in the blood plasma and infusion of acetic acid increased it. No consistent effects of the infused acids on the concentration in blood plasma of esterified cholesterol, free cholesterol, triglyceride or phospholipid were observed. 4. The possibility is discussed that the effects of the infused acids on milk-fat secretion are caused through an alteration of the concentrations of precursors of milk fat in mammary arterial blood.     

Effect of dietary fish oil on platelet aggregability: comparison between two oils with different eicosapentaenoic to arachidonic acid ratio.

Rats, acclimatized on a control diet, were fed for 60 days with diets, supplemented with 10% fat of either marine Hilsa fish (Hilsa ilisa) or fresh-water Chital fish (Notopterus chitala). The percentage of eicosapentaenoic acid in chital oil diet was 0.57 times that of the hilsa oil diet, but the eicosapentaenoic to arachidonic acid ratio in the latter (4.08) was 3.2 times that of the former (1.27). Otherwise these two diets were comparable in respect to total saturated, monounsaturated and n-3 polyunsaturated fatty acid contents. Results showed that of the two only hilsa oil diet could significantly lower platelet aggregability and in vitro thromboxane production, through replacement of arachidonic acid in platelet phospholipid by eicosapentaenoic acid. The antithrombic criteria of the oil seems to be a combination of low arachidonic acid content and high eicosapentaenoic to arachidonic acid ratio.     

Effects on plasma lipoproteins of monounsaturated, saturated, and polyunsaturated fatty acids in the diet of African green monkeys

Work by other investigators has shown that an increase in dietary content of monounsaturated fatty acids can result in a decreased plasma low density lipoprotein (LDL) cholesterol concentration. This observation, combined with the epidemiologic evidence that monounsaturated fat-rich diets are associated with decreased rates of death from coronary heart disease, suggests that inclusion of increased amounts of mono-unsaturated fat in the diet may be beneficial. The present study was carried out in a primate model, the African green monkey, to evaluate the effects of dietary monounsaturated fat on plasma lipoprotein cholesterol endpoints. Two study periods were carried out in which the fatty acid compositions of the experimental diets were varied. All diets contained 35% of calories as fat. In the first experimental period, a mixture of fats was used to set the dietary fatty acid composition to be approximately 50-60% of the desired fatty acid, either saturated, monounsaturated, or polyunsaturated (n-6). In the second experimental period, pure fats were used (palm oil, oleic acid-rich safflower oil, and linoleic acid-rich safflower oil) to maximize the difference in fatty acid composition. The effects of the more exaggerated dietary fatty acid differences of period 2 were similar to those that have been reported in humans. For the group fed the diet enriched in monounsaturated fat compared to saturated fat, whole plasma and LDL cholesterol concentrations were significantly lower while high density lipoprotein (HDL) cholesterol concentrations were not affected. For the group fed the diet enriched in polyunsaturated fat compared to saturated fat, both LDL and HDL cholesterol concentrations were significantly lower than in the group fed saturated fat. LDL cholesterol concentrations were comparable in the monounsaturated and polyunsaturated fat groups and the percentage of cholesterol in LDL was lowest in the monounsaturated fat fed group. Trends were similar for the mixed fat diets, although no statistically significant differences in plasma lipoprotein endpoints could be attributed to monounsaturated fatty acids in this dietary comparison. Since effects on plasma lipoproteins similar to those seen in humans were identified in this primate model, relevant mechanisms for the effects of dietary fatty acids on lipoprotein endpoints related to coronary artery atherosclerosis, per se, can subsequently be examined.     

Differential effects of dietary fat on chick plasma and liver composition and HMG-CoA reductase activity

The comparative effects of diet supplementation with 10% saturated fat rich in 12:0 and 14:0 fatty acids (coconut oil), without and with 1% added cholesterol, and with 10% unsaturated fat rich in n-3 polyunsaturated fatty acids (menhaden oil) on cholesterol metabolism in neonatal chicks were examined to clarify the different mechanisms of their hyper- and hypolipidemic action. Supplementation of coconut oil produced a significant hypercholesterolemia after 7 days of treatment, with a similar increase in the amount of both free and esterified cholesterol. Supplementation of coconut oil plus cholesterol produced a higher increase of plasma cholesterol levels (approximately two to three times higher than those found with standard diet). However, supplementation of menhaden oil induced a significant decrease in total cholesterol after only 2 weeks of treatment. Levels of plasma triglycerides did not change by coconut oil addition to the diet, but a significant increase was observed after coconut oil plus cholesterol feeding. Menhaden oil produced a transient decrease in plasma triglycerides. Hepatic 3-hydroxy-3-methylglutaryl-CoA reductase activity did not change with coconut oil treatment. However, both coconut oil plus cholesterol and menhaden oil supplemented diets drastically decreased reductase activity after 1 week of dietary manipulation. These results show that different nutrients with the same inhibitory effect on reductase activity produced opposite effects on plasma cholesterol content, suggesting the existence of important differences in the regulatory mechanisms implied in cholesterol biosynthesis and its accumulation in plasma.     

Increases in platelet and red cell counts,blood viscosity,and arterial pressure during mild surface cooling: factors in mortality from coronary and cerebral thrombosis in winter.

Six hours of mild surface cooling in moving air at 24 degrees C with little fall in core temperature (0.4 degree C) increased the packed cell volume by 7% and increased the platelet count and usually the mean platelet volume to produce a 15% increase in the fraction of plasma volume occupied by platelets. Little of these increases occurred in the first hour. Whole blood viscosity increased by 21%; plasma viscosity usually increased, and arterial pressure rose on average from 126/69 to 138/87 mm Hg. Plasma cholesterol concentration increased, in both high and low density lipoprotein fractions, but values of total lipoprotein and lipoprotein fractions were unchanged. The increases in platelets, red cells, and viscosity associated with normal thermoregulatory adjustments to mild surface cooling provide a probable explanation for rapid increases in coronary and cerebral thrombosis in cold weather. The raised arterial pressure and possibly cholesterol concentration may contribute to slower components of the increased thrombosis.     

Reduction in plasma cholesterol and increase in biliary cholesterol by a diet rich in n-3 fatty acids in the rat

Cholesterol and lipoprotein metabolism were investigated in a group of rats fed a fish oil-supplemented diet, a rich source of n-3 fatty acids. For comparison purposes, other groups of rats were fed either safflower oil (n-6 fatty acids) or coconut oil (saturated fatty acids). Diets were isocaloric and contained identical amounts of cholesterol. Rats fed fish oils for 2 weeks showed a 35% lower plasma cholesterol level than rats fed safflower oil, who in turn showed a 14% lower plasma cholesterol level than those fed coconut oil. The fall in plasma cholesterol level with fish oils was associated with significant falls in low density and high density lipoprotein cholesterol levels, but with no significant change in the ratio of low density to high density lipoprotein cholesterol. The fatty acid compositions of plasma, hepatic, and biliary lipids showed relative enrichment with n-3 fatty acids, reflecting the composition of the diet. The fish oil diet increased the basal secretion rate of cholesterol into bile, but the bile acid secretion rate remained unchanged. It is suggested that n-3 fatty acids reduce the plasma cholesterol level in rats by increasing the transfer of cholesterol into bile.