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Digestion, absorption and effects on cholesterol absorption of menhaden oil, fish oil concentrate and corn oil by rats.

Adult male rats were surgically provided with a drainage catheter in the left thoracic lymphatic channel and an indwelling duodenal catheter for constant infusion of physiological saline-5% glucose. After an overnight fast, animals were given a single duodenal dose of an aqueous emulsion containing one of the following: oleic acid, corn oil, menhaden oil or a fish oil concentrate (FOC) and [1,2-3H]cholesterol. Digestion and absorption were estimated by recovering the total fatty acids in the thoracic duct lymph over a 24-h collection period (after subtraction of the "baseline" endogenous fatty acids in the lymph). Cholesterol absorption in the thoracic duct lymph was significantly reduced (P less than 0.05) in the presence of menhaden oil or FOC compared to that in the presence of corn oil. With various fat feedings, the major increases in lymph fatty acids were directly related to the dietary fatty acid content. The relative amounts of eicosapentaenoic acid (EPA) and arachidonic acid (AA) in the thoracic lymph were influenced by the lipid content of the emulsion. The EPA/AA ratio in control, oleic acid and corn oil feedings ranged from 0.12 to 0.25. When marine oil was administered, the EPA/AA ratio was 0.78-0.98. The total amount of fatty acids found in the lymph after marine oil feeding was significantly less (P less than 0.01) than that found after corn oil feeding. The results suggested that the digestion and absorption of menhaden oil and FOC were decreased as compared with corn oil. The EPA/AA ratio was increased in the thoracic lymph after dietary fish oil feeding.

Animals

Plasmodium yoelii: comparative antimalarial activities of dietary fish oils and fish oil concentrates in vitamin E-deficient mice.

Feeding vitamin E-deficient diets containing either fish oils such as menhaden, salmon, or anchovy oil or fish oil concentrates based on n-3 ethyl esters or free fatty acids protected mice against Plasmodium yoelii as indicated by decreased parasitemia and improved survival. The fish oil concentrates depressed plasma tocopherol levels more strongly in vitamin E-supplemented mice than the menhaden oil. The free fatty acid concentrate appeared to suppress parasitemia in vitamin E-deficient mice better than the menhaden oil, although ultimate survival was similar in both groups. Dietary manipulation of host antioxidant status offers promise as a possible means of malaria control.

Animals

Clinical applications of fish oils.

Fish oil supplements are currently being nationally advertised, and many physicians are being queried about their clinical utility. Epidemiologic studies reveal a low incidence of cardiovascular disease in people, such as the Eskimos, who eat large amounts of seafood. Cardiovascular health may be improved because fish and fish oil supplements lower plasma lipid levels (especially triglycerides), inhibit platelet aggregation, and may decrease blood pressure and viscosity and increase high-density lipoprotein (HDL) levels. Preliminary observations also suggest a potential future role for fish oils in the treatment of some autoimmune diseases, such as atopic dermatitis, psoriasis, and rheumatoid arthritis. Patients with serum triglyceride levels greater than 5.64 mmol/L and/or cholesterol levels greater than 7.75 mmol/L refractory to dietary management may benefit from a medically supervised trial of fish oil supplements. Data currently available are insufficient to recommend fish oil supplements for the general public, or for patients with other diseases, and side effects must also be considered. These include occasional adverse lipid changes, potential for bleeding and vitamin E deficiency, and, with some preparations, vitamin A and D toxicity.

Adolescent

Evening primose oil and fish oil are ineffective as supplementary treatment of bronchial asthma.

The effect of daily dietary supplementation with 15 to 20 mL of evening primrose seed oil or fish oil was assessed by comparison with olive oil as placebo in a cross-over study in 29 asthmatics. During 10 weeks of each regimen, the patients kept record of symptoms, peak expiratory flow rates and medication. Plasma and urine TxB2, PGE2, PGF2 alpha and 6 keto-PGF1 alpha and plasma fatty acid composition of plasma cholesterol esters were measured at the end of each treatment period. There were no differences between regimes with regard to peak flow rates, symptoms, or drug consumption. Plasma PGE2 levels increased during the fish oil treatment but there were no changes in other prostanoids in plasma or urine. The fatty acid pattern of plasma cholesterol esters showed significant differences between the supplementation periods. We conclude that moderate doses of evening primrose oil or fish oil are ineffective as a supplementary treatment of bronchial asthma.

Adult

Effects of dietary corn oil and fish oil concentrate on lipid composition of calf tissues.

Lipid composition of calf blood plasma, liver platelets, muscle, heart, and brain was measured, as affected by high dietary intake of linoleic acid from corn oil or of polyunsaturated fatty acids from fish oil concentrate. Plasma total lipids, phosphatidylcholine, and cholesteryl esters were reduced by corn oil and fish oil concentrate. Dietary fatty acid composition had no influence on percentage distribution of the major phospholipid components of liver, heart, muscle, and brain, but did alter the polyunsaturated fatty acid composition of major phospholipids in plasma, liver, platelets, muscle, and heart. In general, high linoleic acid intake increased linoleic acid and decreased oleic, arachidonic, and linolenic acids in tissue phospholipids, and fish oil concentrate high in eicosapentaenoic and docosahexaenoic acids increased phospholipid concentrations of these fatty acids. The fatty acid composition of brain phosphatidylcholine and phosphatidyl-ethanolamine was relatively resistant to dietary lipid alterations. The fatty acid changes in tissue phospholipids that resulted from dietary lipid alterations may have important implications in eicosanoid metabolism, and in the structure and function of cell membranes.

Animal Feed

Blood pressure in spontaneously hypertensive rats fed butterfat, corn oil, or fish oil.

Dietary fats have been shown to influence blood pressure in humans and animal models of hypertension. The ability of a particular fat to modulate arterial pressure appears to depend on its fatty acid profile rather than its degree of saturation or unsaturation. Little is known about the effects of specific dietary fats of animal origin on blood pressure. We tested the concurrent effects of both calcium and dietary fat on blood pressure development in the spontaneously hypertensive rat. Sixty animals were fed diets containing butterfat, fish oil, or corn oil from 3-26 weeks of age. Each diet among the three oils was further modified to contain either 0.25% or 2.0% of the diet as calcium. All six diets provided 18% of the diet (36% of the calories) as fat. The polyunsaturated-to-saturated fat ratio was 0.07, 0.84, and 4.54 for butterfat, fish oil, and corn oil, respectively. Fish oil consumption resulted in lower blood pressures compared with butterfat (p less than 0.036) or corn oil (p less than 0.0009). Similarly, butterfat feeding resulted in lower blood pressures when compared with corn oil (p less than 0.054). Supplementing the diet with calcium decreased blood pressure in both the butterfat and corn oil diets. When butterfat diets were supplemented with calcium, the resulting blood pressures did not differ significantly from those obtained with the two fish oil diets. It is concluded that butterfat, though highly saturated, is associated with less of an increase in the spontaneously hypertensive rat's blood pressure than is corn oil, which is highly unsaturated.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals

Absorption of eicosapentaenoic acid and docosahexaenoic acid from fish oil triacylglycerols or fish oil ethyl esters co-ingested with a high-fat meal.

The absorption of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fish oil triacylglycerols and fish oil ethyl esters consumed in a high-fat meal (44 g total fat) by male volunteers was measured and compared to values previously reported for consumption in a low-fat meal (8 g total fat). Absorption of EPA, but not of DHA, from fish oil triacylglycerols was significantly improved from 69% to 90% by co-ingestion with the high-fat meal. Absorption of both EPA and DHA from fish oil ethyl esters was increased three-fold, to about 60%, by co-ingestion with the high-fat meal, indicating that absorption of fatty acid ethyl esters is highly dependent on the amount of co-ingested fat.

Absorption

[Quantitative determination of trace metals in frozen fish, fish oil and fish meal (author's transl)].

As a contribution to the discussion on the "Verordnung uber Umweltkontaminanten" (draft) we examined 73 double samples of the frequent types of edible fish and 2 samples each of fish oil and fish meal for their content of arsenic (As), cadmium (Cd), lead (Pb) and mercury (Hg). Arsenic was determined photometrically, cadmium and lead by anodic stripping voltammetry and mercury by flameless atomic absorption spectrometry. We found the following average contents (ppm): 0.84 As, 0.003 Cd, 0.08 Pb, 0.06 Hg. The limits (ppm) set up in the draft for a German "Höchstmengenverordnung" (regulation specifying the maximum concentrations allowed) were by far not reached in the case of Cd, Pb, and Hg with all samples while they were fulfilled in the case of As by only 18% of the samples. It seems that the limit for As of 0.5 ppm has been set up too low. In the average, the following proportion applies for the trace contents found: Cd:Hg:Pb:As = 1:20:27:280. Correlations between the contents of trace metals on the one hand and fishing grounds or trawler or sample piece on the other could not be found.

Arsenic

Analytical-scale high-performance liquid chromatography of omega-3 fatty acid esters derived from fish oils.

Fish oil triglycerides were transesterified to their corresponding methyl and ethyl esters. The esters were separated by reversed-phase high-performance liquid chromatography on a 10-cm column of 5-microns octadecylsilyl silica, using a ternary mobile phase of acetonitrile-tetrahydrofuran-water (9:5:11). The separation of principal saturated and unsaturated C14-C22 fatty acid esters was accomplished in 60 min. For the polyenoic acid esters, detection limits of ca. 26 micrograms were observed, and baseline resolution of the important critical pair of esters of the omega 3 fatty acids, eicosapentaenoic acid (C20:5 omega 3) and docosahexaenoic acid (C22:6 omega 3) was achieved. However, to obtain baseline resolution of the esters from minor fatty acid esters, a urea crystallization procedure was required prior to chromatographic analysis. The influence on the reversed-phase chromatographic retention of four different ester moieties on the fatty acids were also studied. The n-alkyl esters exhibited an increase in ln k' with increasing chain length and with increasing lipophilic character of the alkyl ester moieties; however, with the aromatic benzyl derivatives there was a decrease in ln k' compared with the alkyl esters.

Chromatography, High Pressure Liquid

A double-blind comparison of olive oil and a combination of evening primrose oil and fish oil in the management of canine atopy.

A randomised double-blind parallel study lasting eight weeks was used to assess the effects of olive oil in a group of atopic dogs whose clinical signs were well controlled by dietary supplementation with a combination of evening primrose oil and fish oil. Nine of the 11 dogs which continued to receive this combination were considered unchanged at the conclusion of the study, whereas eight of the 10 dogs switched to olive oil had deteriorated. The mean plasma concentration of dihomogammalinolenic acid, a precursor of potentially antiinflammatory mediators, was significantly reduced (P < 0.05) in the olive oil-treated group at the end of the study. There were no significant differences between the mean plasma linoleic, eicosapentaenoic and arachidonic acid concentrations in the two groups. These findings suggest that olive oil is not an effective therapeutic agent in the control of canine atopy.

Animal Feed

Effect of dietary intake of fish oil and fish protein on the development of L-azaserine-induced preneoplastic lesions in the rat pancreas.

The effect of dietary intake of fish (menhaden) oil and fish (cod) protein on the development of pancreatic preneoplastic lesions was examined in male Wistar rats. Fourteen-day-old animals were given a single ip injection of 30 mg L-azaserine/kg body weight [CAS: 115-02-6; diazoacetate serine (ester)]. At 21 days of age they were weaned and maintained on dietary treatment for 4 months. Fish protein did not appear to produce a significantly different preneoplastic response when compared to casein as a protein source. However, a 20% menhaden oil diet, rich in omega 3 fatty acids, produced a significant decrease in the development of both the size and number of preneoplastic lesions when compared to a 20% corn oil diet rich in omega 6 fatty acids. This study provides evidence that fish oils, rich in omega 3 fatty acids, may have potential as inhibitory agents in cancer development.

Animals

Supplementation of patients with homozygous sickle cell disease with zinc, alpha-tocopherol, vitamin C, soybean oil, and fish oil.

Thirteen patients (aged 0.7-17.9 y) with homozygous sickle cell disease were supplemented with alpha-tocopherol, vitamin C, zinc, and soybean oil (suppl 1; for 8 mo) and alpha-tocopherol, vitamin C, and fish oil (suppl 2; for 7 mo). Urinary zinc (suppl 1), plasma vitamin C, plasma cholesterol ester and erythrocyte (RBC) omega 3 fatty acids (suppl 2), and plasma and RBC alpha-tocopherol (suppl 1 and 2) increased. Suppl 1 decreased irreversibly sickled cells by 37.5%, decreased RBC protoporphyrin and urinary porphyrins, and increased the RBC total fatty acid-cholesterol ratio. Suppl 2 decreased plasma triglycerides, further increased the RBC alpha-tocopherol, moderately increased the RBC double-bond index, but decreased the RBC total fatty acid-cholesterol ratio. Zinc, copper, and porphyrins showed prolonged changes. The supplements did not change hemoglobin concentrations, RBC age (reticulocytes, polyamines), or number of aplastic and vasoocclusive crises. Zinc reduces irreversibly sickled cells. Augmentation of RBC antioxidant status by alpha-tocopherol and vitamin C and incorporation of omega 3 fatty acids into RBCs do not affect hemolytic component. Effects on vasoocclusive component are unclear.

Adolescent

Effect of a fish oil diet on the composition of rat neutrophil lipids and the molecular species of choline and ethanolamine glycerophospholipids.

When rats were fed a corn oil versus a corn oil-fish oil diet the overall phospholipid content and composition as well as the subclass distribution of the choline- and ethanolamine-containing glycerophospholipids from neutrophils were not altered. The serine-containing glycerophospholipids were characterized by high levels of stearic and oleic acids. When fish oil was added to the diet it replaced some of the arachidonate in both the inositol- and the serine-containing glycerophospholipids. In the corn oil-fed animals, 25.2 and 33.6 mole %, respectively, of the molecular species of 1,2-diacyl- and 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine contained arachidonate. The values for 1,2-diacyl and 1-O-alk-1'-enyl-2-acyl-sn-glycero-3-phosphoethanolamine were, respectively, 41 and 55.8 mole %. When half of the 5% corn oil in the diet was replaced by fish oil, there was a 53, 38, 27, and 25% reduction, respectively, in the level of arachidonate in these four lipid subclasses. The amount of 5,8,11,14,17-eicosapentaenoic acid incorporated into these four subclasses was always less than the decline in arachidonic acid. This was due, in part, to the acylation of small amounts of 22-carbon (n-3) acids into these lipids. Molecular species analysis demonstrated that 5,8,11,14,17-eicosapentaenoic acid paired with the same components at the sn-1 position, and in the same ratio, as did arachidonic acid. The amounts of 16- and 18-carbon saturated and unsaturated fatty acid at the sn-2 position were not altered by dietary change. Collectively, these findings suggest that 5,8,11,14,17-eicosapentaenoic and arachidonic acids are metabolized in a similar way by neutrophils. These studies also support the concept that neutrophils contain two metabolic pools of phospholipids. One pool is altered by dietary fat change while the pool containing 16- and 18-carbon acids is resistant to change when fish oil is included in the diet.

Animals

A fish oil diet inhibits amyloid P component (AP) acute phase responses in arthritis susceptible mice.

Amyloid P component (AP) bears close homology with C-reactive protein and behaves as an acute phase reactant in the plasma of mice but not in man. Our aim was to determine whether AP is influenced by diet, gender, and arthritis severity in a murine model of arthritis. B10.RIII mice were segregated according to gender and diet at 8 wk of age: the source of fat was either corn oil, fish oil, or beef tallow (5% by weight). Four weeks later, each mouse was immunized with 100 micrograms fetal bovine type II collagen, and the incidence and severity of arthritis was noted at weekly intervals. AP was measured by competitive ELISA in plasma taken 5 wk and 15 wk after immunization. AP levels were less in fish oil fed males and females. Under all conditions tested AP levels of females were greater than in males. There was a negative correlation between AP levels and the severity of arthritis. We conclude from these data that although AP levels cannot be used as indices of arthritis severity, there are significant dietary and gender effects on AP concentrations as long as 15 wk after immunization with type II collagen.

Acute-Phase Reaction

Intestinal absorption of fish oil in rats previously adapted to diets containing fish oil or corn oil.

A study was conducted to evaluate whether the composition of previous dietary fat affects the absorption and composition of lymph obtained after a meal of fish oil. Adult male Sprague-Dawley rats were fed diets containing either corn oil or fish oil (MaxEPA) for 2 weeks. They were then given intraduodenally a bolus of an emulsion of 0.5 ml of fish oil plus 0.5 ml of 20 mM sodium taurocholate. Intestinal lymph was collected from a cannula in the main intestinal lymph trunk for various times after oil administration. Rats proportion of the test dose fo fish oil than those fed corn oil. There was an effect of previous diet on the fatty acid composition of the lymph. Rats fed fish oil had a higher percentage of eicosapentaenoic and docosahexaenoic acids in the lymph lipids than those fed corn oil while those fed corn oil had a higher percentage of linoleic acid. These results rule out decreased intestinal absorption as a mechanism for the hypotriacylglycerolemic effect of dietary fish oils. They also indicate a significant contribution of endogenous lipids to the fatty acids in lymph.

Adaptation, Physiological

[Should I also eat fish oils? A critical assessment of the use of fish oils in the prevention of ischemic heart disease].

The effect of a daily dietary supplement of 6 g fish oil (3.4 g eicosapentaenoic and docosahexaenoic acid) on body weight, blood pressure, bleeding time and blood lipids was assessed in an open trial. The fish oil was taken for four weeks by nine 30-55 year-old individuals. An age- and sex-matched control group took equivalent amounts of safflower oil, which has an overall fatty acid composition similar to the tested fish oil. The fish oil supplement caused significant changes in body weight (median: +0.9 kg), systolic blood pressure (-10 mmHg), diastolic blood pressure (-5 mmHg), and high density lipoprotein (HDL) cholesterol concentration (+0.21 mmol/l), whereas serum triglycerides decreased insignificantly (-0.25 mmol/l). Low density lipoprotein (LDL) concentration were not affected. We observed no changes in the control group. In the discussion, it is underlined that fish oil supplementation may affect some risk markers of ischemic heart disease favourably. However, other important risk markers, including LDL cholesterol, are unaffected or unfavourably affected by fish oils. A more uni-directional reduction in risk can be attained by a change in dietary habits, which should be preferable to a fish oil supplement in the general population. Individuals who show critically low HDL/total cholesterol ratios, who are hypertriglyceridemic, or are mildly hypertensive may, however, benefit from a fish oil supplement of the amount tested here.

Adult

Diet and fatty acids: can fish substitute for fish oil?

As fish oil has been shown to be beneficial in rheumatoid arthritis and in psoriasis, we examined whether a diet rich in fish has a similar effect on membrane and plasma lipids as a dietary fish oil supplement. Volunteers recruited by 2 rheumatology units in Switzerland formed three parallel groups eating respective diets during 2 months: a normal diet without fish; a normal diet including 700 g fish per week; a normal diet without fish but with additional fish oil (7.5 g daily). As outcome measures we determined the lipid composition of platelet-rich plasma, the serum cholesterol and triglycerides before the study and after 1 and 2 months of the designated diet. The relative amounts of both eicosapentaenoic acid and docosahexaenoic acid increased significantly in the fish oil group and in the group with the fish diet; no change was seen in the control group. The effect on triglycerides, which were low at the beginning of the study, was minor and no change in cholesterol was seen. In conclusion, 4 to 6 meals with fish per week without any other dietary changes can induce similar changes in lipids as a supplement of fish oil.

Adolescent

Reduction in the ADP release from shear-stressed red blood cells by fish oil administration.

Fish oil concentrate (5.4 g/day) was administered to 8 young male volunteers and to 7 middle-aged male volunteers for 1 week. ADP released into the supernatant of red blood cell (RBC) suspension by a shear stress of 375/sec for 3 min was measured before and after fish oil administration. Before the administration the ADP release from shear-stressed RBCs in the middle-aged group was significantly higher than in the young group. After the administration the ADP release was reduced significantly in the young group (by 46%, p less than 0.001) and nonsignificantly in the middle-aged group (by 54%, p = 0.09). If the two groups were combined, the reduction was also significant (by 50%, p less than 0.005). This reduction was significantly correlated with the improvement of RBC filterability after fish oil administration (n = 13, r = 0.62, p less than 0.05). We suggest that the reduction of the ADP release from shear-stressed RBCs is one of the mechanisms of action of eicosapentaenoic acid against thrombotic disease.

Adenosine Diphosphate