Functional Changes of Rat Brain Microsomal Membrane Surface After Learning Task Depending on Dietary Fatty Acids

Abstract: Biochemical characteristics of brain microsomal membranes were examined before and after the brightness-discrimination learning tasks in rats that were fed either safflower oil (α-linolenate-deficient) or perilla oil (α-linolenate-sufficient) diets. We detected small changes in the chain elongation system for polyunsaturated fatty acids in microsomes, whereas no significant difference was detected in the inositol trisphosphate-induced calcium release and ATP-induced calcium uptake profiles of microsomes between the two dietary groups. The calcium ion-induced aggregation rate of microsomes was determined in both groups. We found that the aggregation rate of microsomes in the safflower oil group was significantly greater than that in the perilla oil group. The difference in susceptibility of microsomal membrane phospholipids to phospholipase A₂ between the groups was obvious, and the amount of released fatty acids by phospholipase A₂ from the perilla oil group microsomes was nearly half of that from the safflower oil group microsomes after the learning task. Susceptibility of sialic acids on the brain microsomal membranes to exogenous sialidase was different only after the learning task in the safflower and perilla oil groups. These results suggest that the biochemical characteristics of membrane surfaces of brain microsomes are affected significantly by the learning task itself in a dietary oil-dependent manner.     

Effect of dietary alpha-linolenate/linoleate balance on brain lipid compositions and learning ability of rats

Spontaneously hypertensive rats (SHR) and normotensive control, Wistar/Kyoto (WKY) rats through two generations were fed a semipurified diet supplemented either with safflower oil (rich in linoleate) or with perilla oil (rich in alpha-linolenate). The cerebral lipid contents and phospholipid compositions did not differ between the two dietary groups of SHR rats. There were also no differences in the unsaturated/saturated ratios of individual phospholipids or the proportions of plasma-logens. However, the proportions of (n-3) and (n-6) fatty acids were significantly different. Decreases in the proportions of docosahexaenoate [22:6 (n-3)] in phosphatidylethanolamine and phosphatidylserine in the safflower oil group were compensated for with increases in the proportions of docosatetraenoic [22:4 (n-6)] and docosapentaenoic [22:5 (n-6)] acids as compared with the perilla oil group. These differences in phospholipid acyl chains were much smaller than the difference in the proportions of linoleate and alpha-linolenate of the diets. In a brightness-discrimination learning test, the total number of responses to the positive and negative stimuli were less in the groups fed perilla oil. However, the alpha-linolenate-deficient group took longer to decrease the frequency of R- responses and therefore longer to learn the discrimination. Consequently, the correct response ratios were higher in the perilla oil groups than in the safflower oil groups. Thus, the dietary alpha-linolenate/linoleate balance influenced the (n-3)/(n-6) balance of polyenoic fatty acids differently among brain phospholipids.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of the dietary alpha-linolenate/linoleate balance on lipid compositions and learning ability of rats. II. Discrimination process, extinction process, and glycolipid compositions

Donryu strain rats through two generations were fed semi-purified diets supplemented with safflower seed oil (rich in linoleic acid) or with perilla seed oil (rich in alpha-linolenic acid), or a conventional laboratory chow (normal control diet). Brightness-discrimination learning ability was determined to be the highest in the perilla oil-fed group, followed by the normal group, and then by the safflower group, extending our earlier observation in a different strain of rat that alpha-linolenic acid is a factor in maintaining high learning ability (Yamamoto, N., M. Saitoh, A. Moriuchi, M. Nomura, and H. Okuyama. 1987. J. Lipid Res. 28: 144-151). After the brightness-discrimination learning test was administered, extinction of learning was measured. The time required for extinction was significantly longer in the safflower group than in either the perilla group or the normal diet group. Thus, the dietary alpha-linolenate/linoleate balance affected both the learning and the extinction of learning. The glycolipids of the cerebrum, cerebellum, and olfactory lobe were analyzed. Although the fatty acid compositions of the sulfatide and gangliosides were significantly different in the three parts of the brain, relatively little difference was observed in the fatty acids of glycolipids between the safflower group and the perilla group, suggesting that gross changes in brain glycolipids are not responsible for the differences in learning abilities between these dietary groups.     

Comparative effects of perilla and fish oils on the activity and gene expression of fatty acid oxidation enzymes in rat liver

The activity and mRNA level of hepatic enzymes in fatty acid oxidation and synthesis were compared in rats fed diets containing either 15% saturated fat (palm oil), safflower oil rich in linoleic acid, perilla oil rich in α-linolenic acid or fish oil rich in eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) for 15 days. The mitochondrial fatty acid oxidation rate was 50% higher in rats fed perilla and fish oils than in the other groups. Perilla and fish oils compared to palm and safflower oils approximately doubled and more than tripled, respectively, peroxisomal fatty acid oxidation rate. Compared to palm and safflower oil, both perilla and fish oils caused a 50% increase in carnitine palmitoyltransferase I activity. Dietary fats rich in n-3 fatty acids also increased the activity of other fatty acid oxidation enzymes except for 3-hydroxyacyl-CoA dehydrogenase. The extent of the increase was greater with fish oil than with perilla oil. Interestingly, both perilla and fish oils decreased the activity of 3-hydroxyacyl-CoA dehydrogenase measured using short- and medium-chain substrates. Compared to palm and safflower oils, perilla and fish oils increased the mRNA level of many mitochondrial and peroxisomal enzymes. Increases were generally greater with fish oil than with perilla oil. Fatty acid synthase, glucose-6-phosphate dehydrogenase, and pyruvate kinase activity and mRNA level were higher in rats fed palm oil than in the other groups. Among rats fed polyunsaturated fats, activities and mRNA levels of these enzymes were lower in rats fed fish oil than in the animals fed perilla and safflower oils. The values were comparable between the latter two groups. Safflower and fish oils but not perilla oil, compared to palm oil, also decreased malic enzyme activity and mRNA level. Examination of the fatty acid composition of hepatic phospholipid indicated that dietary α-linolenic acid is effectively desaturated and elongated to form EPA and DHA. Dietary perilla oil and fish oil therefore exert similar physiological activity in modulating hepatic fatty acid oxidation, but these dietary fats considerably differ in affecting fatty acid synthesis.     

Reversibility of n-3 fatty acid deficiency-induced alterations of learning behavior in the rat: level of n-6 fatty acids as another critical factor

Rats fed a semipurified diet supplemented with 3% (w/w) safflower oil [Saf, n-3 fatty acid deficient, high linoleic acid (18:2n-6)] through two generations exhibit decreased correct response ratios in a brightness-discrimination learning test compared with rats fed 3% perilla oil [Per, high alpha-linolenic acid (18:3n-3)]. This is associated with a decreased DHA (22:6n-3)-to-arachidonic acid (20:4n-6) ratio in brain lipids. In the first set of experiments, dietary oil was shifted from Saf to a mixture of 2.4% safflower oil plus 0.6% DHA after weaning (Saf-DHA), but all parameters measured in the learning test were essentially unchanged. Brain 22:6n-3 content of the Saf-DHA group reached that of the Per group but the levels of 20:4n-6 and docosatetraenoic acid (22:4n-6) did not decrease to those of the Per group at the start of the test. In the second set of experiments, dietary oil was shifted to a mixture of 0.6% safflower oil plus 1.2% oleic acid (OA) plus 1.2% DHA (Saf-OA-DHA group) with 18:2n-6 content comparable to that of the Per group. The Saf-OA-DHA group exhibited a learning performance similar to that of the Per group; brain 22:6n-3, 20:4n-6, and 22:4n-6 contents were also comparable to those of the Per group. These results indicate that the altered learning behavior associated with a long-term n-3 fatty acid deficiency is reversed by supplementing 22:6n-3 after weaning, when the levels of competing n-6 fatty acids in the diet and brain lipids are limited.     

Effect of dietary alpha-linolenate/linoleate balance on mean survival time, incidence of stroke and blood pressure of spontaneously hypertensive rats

Following the suckling period, stroke-prone spontaneously hypertensive rats (SHR-SP) were fed semi-purified diets supplemented either with safflower seed oil (rich in linoleic acid) or with perilla seed oil (rich in alpha-linolenic acid). The mean survival time of male SHR-SP fed the perilla diet was longer than that fed the safflower diet by 17% (p less than 0.001) while the difference was 15% in female SHR-SP (p less than 0.05). The mean survival times of female SHR-SP were more than 40% longer than those of male SHR-SP in both dietary groups. Post-mortem examinations of brains revealed apoplexy-related symptoms as the major cause of the death in both dietary groups. The systolic blood pressure was lower by ca. 10% (21 mmHg) in the perilla group than in both the safflower group and conventional diet group. The eicosapentaenoate (20:5 n-3)/arachidonate (20:4 n-6) ratio of platelet phospholipids in spontaneously hypertensive rat (SHR), a measure of platelet aggregability, was much higher in the perilla group than in the safflower group. Thus, increasing the dietary alpha-linolenate/linoleate ratio resulted in an increased mean survival time of SHR-SP rats, possibly by lowering blood pressure and platelet aggregability.     

Effect of the dietary alpha-linolenate/linoleate balance on leukotriene production and histamine release in rats

Rats were fed semi-purified diets supplemented either with safflower seed oil rich in linoleate (18:2n-6) or with perilla seed oil rich in alpha-linolenate (18:3n-3) through two generations. In the major phospholipids of polymorphonuclear leukocytes (PMNs), the proportions of n-6 polyunsaturated fatty acids (18:2, 20:4, 22:4 and 22:5) were higher but those of n-3 acids (20:5, 22:5 and 22:6) were lower in the safflower group than in the perilla group. When stimulated with a calcium ionophore, the PMNs from the safflower group produced 27% more leukotriene (LT)B4 than those from the perilla group. The formation of LTB5 which has biological activities less than 1/10 those of LTB4, was negligible in the safflower group but was 40 ng/10(7) PMN cells in the perilla group. The amount of the total LTB formed in the perilla group tended to be more than in the safflower group. The formation of SRS-A (slow-reacting substances of anaphylaxis) by PMNs was determined by measuring the spasmogenic activities of LTs on guinea pig ileum. SRS-A activity was 59% higher in the safflower group than in the perilla group. In contrast, histamine release from rat peritoneal mast cells was not significantly different between the two groups. Thus, the increasing the alpha-linolenate/linoleate ratio of diets results in the decreased formation of LTs derived from 20:4n-6 in PMNs. This may be beneficial in lowering the severity of allergic and inflammatory responses caused by LTs, and thereby shifting the pathological symptoms to normal self-defense mechanism.     

Effect of dietary alpha-linolenate on platelet-activating factor production in rat peritoneal polymorphonuclear leukocytes.

The effects of dietary alpha-linolenate (18:3, n-3) and linoleate (18:2, n-6) on platelet-activating factor (PAF) production were examined. Rats were fed an alpha-linolenic acid-rich (perilla oil) diet or a linoleic acid-rich (safflower oil) diet for 6 wk, and polymorphonuclear leukocytes (PMN) were elicited by peritoneal injection of casein. The overall phospholipid content and composition as well as the subclass distribution of choline and ethanolamine glycerophospholipids in PMN were not altered by these diets. However, with the perilla oil diet their content of a putative precursor of PAF, 1-alkyl-2-arachidonoyl-sn-glycero-3-phosphocholine was approximately 50% of that with safflower oil diet. On exposure to various concentrations of FMLP, PAF formation by PMN in the perilla oil group was less than 50% of that by PMN in the safflower oil group. A larger difference in PAF productions by PMN in the two dietary groups was observed on their stimulation with calcium ionophore A23187. These results demonstrate that PAF production is modulated in some as yet unknown way by changing the alpha-linolenate/linoleate balance of the diet.     

Minimum requirements of n-3 and n-6 essential fatty acids for the function of the central nervous system and for the prevention of chronic disease.

General behavioral patterns of rats or mice fed 5 wt% safflower oil (75% linoleate [n-6] and less than 0.1% alpha-linolenate [n-3]) for two generations were significantly different from those of animals fed 5 wt% perilla oil (15% n-6 and 55% n-3). Also, brightness-discrimination learning ability and retinal function were higher in the perilla group than in the group fed 5 wt% soybean oil (53% n-6 and 4.7% n-3) or safflower oil, indicating that the requirement of n-3 for the maximum responses of the nervous system is above 0.6 en% when there is 6.8 en% linoleate n-6. Perilla oil has been found to be beneficial for the suppression of carcinogenesis, allergic hyperreactivity, thrombotic tendency, apoplexy, hypertension, and aging in animals, as compared with soybean oil and safflower oil. These results are against a lipid peroxide theory of aging, carcinogenesis, and chronic diseases. Animal experiments and epidemiological studies lead to a recommendation that the intake of n-6 should be decreased to as low as 2-4 en% and that of n-3 be increased to levels higher than linoleate n-6 for the prevention of chronic diseases prevailing in the industrialized countries.     

Interactions of dietary fats and proteins on fatty acid composition of immune cells and LTB4 production by peritoneal exudate cells of rats

The interaction of dietary fats and proteins on lipid parameters of rats was studied using safflower oil (linoleic acid-rich), borage oil (gamma-linolenic acid-rich) or perilla oil (alpha-linolenic acid-rich) in combination with casein or soybean protein. The experiment was focused on the fatty acid composition of immune cells and the leukotriene B4 production by peritoneal exudate cells. Serum total cholesterol, triglyceride, and phospholipid levels were low in perilla oil-fed or soybean protein-fed rats. Fatty acid compositions of serum and liver phospholipids reflected those of dietary fats. However, feeding borage oil resulted in a marked increase in the proportion of dihomo-gamma-linolenic acid in phospholipids of peritoneal exudate cells, spleen lymphocytes, and mesenteric lymph node lymphocytes in relation to those of liver and serum. It is suggested that activities of metabolic n-6 polyunsaturated fatty acids are different between immune and other tissues. In addition, the magnitude of the reduction of the proportion of linoleic acid of perilla oil in immune cells was considerably more moderate than serum and liver, indicating a different degree of interference of alpha-linolenic acid with linoleic acid metabolism. Leukotriene release from peritoneal exudate cells was in the order of safflower oil > borage oil > perilla oil groups as reflecting the proportion of arachidonic acid, and tended to be lower in soybean protein-fed groups. These suggest an anti-inflammatory property of gamma-linolenic acid as well as alpha-linolenic acid tended to be strengthened when they were combined with soybean protein than with casein.     

Study of diet and drug interactions on prostanoid metabolism

To study the extent to which combinations of different dietary lipids stimulate or inhibit prostanoid synthesis groups of 12 rats were fed diets containing 10% (w/w) of either safflower oil, hydrogenated coconut oil/safflower oil, cod liver oil/safflower oil or cod liver oil/linseed oil for a period of four weeks. All diets, with the exception of the safflower oil feed, contained similar levels of linoleic acid. Two further groups of rats placed on the cod liver oil diets were injected with indomethacin (4 mg/kg, i.p.) every three days to establish the completeness of dietary prostaglandin (PG) inhibition. In spite of a 20 fold difference in dietary linoleic acid content, the safflower oil group had similar PG generating capacities to the saturated fat control group, suggesting tight metabolic control of PGs and their precursors. Although there were prostanoid variations in tissue responses, both of the cod liver oil diets substantially reduced generation of aortic, whole blood and renal prostanoids, and decreased urinary PG excretion. The degree of inhibition of renal PGs was substantially greater in the cod liver oil/linseed oil group, with prostaglandin levels being 35% lower than those observed in the cod liver oil/safflower oil fed animals suggesting that linolenic acid and the marine oil fatty acids act synergistically to inhibit formation of 2-series prostaglandins. Concurrent administration of omega-3 fatty acids and indomethacin reduced PG levels further than those obtainable by diet alone, demonstrating that the diets did not result in maximal inhibition. Awareness of these various effects is important for both physiological or clinical studies in which dietary manipulations are used as a means of modifying prostanoid synthesis.     

Effect of dietary alpha-linolenic acid on the activity and gene expression of hepatic fatty acid oxidation enzymes

The activities of hepatic fatty acid oxidation enzymes in rats fed linseed and perilla oils rich in alpha-linolenic acid (alpha-18:3) were compared with those in the animals fed safflower oil rich in linoleic acid (18:2) and saturated fats (coconut or palm oil). Mitochondrial and peroxisomal palmitoyl-CoA (16:0-CoA) oxidation rates in the liver homogenates were significantly higher in rats fed linseed and perilla oils than in those fed saturated fats and safflower oil. The fatty oxidation rates increased as dietary levels of alpha-18:3 increased. Dietary alpha-18:3 also increased the activity of fatty acid oxidation enzymes except for 3-hydroxyacyl-CoA dehydrogenase. Unexpectedly, dietary alpha-18:3 caused great reduction in the activity of 3-hydroxyacyl-CoA dehydrogenase measured with short- and medium-chain substrates but not with long-chain substrate. Dietary alpha-18:3 significantly increased the mRNA levels of hepatic fatty acid oxidation enzymes including carnitine palmitoyltransferase I and II, mitochondrial trifunctional protein, acyl-CoA oxidase, peroxisomal bifunctional protein, mitochondrial and peroxisomal 3-ketoacyl-CoA thiolases, 2, 4-dienoyl-CoA reductase and delta3, delta2-enoyl-CoA isomerase. Fish oil rich in very long-chain n-3 fatty acids caused similar changes in hepatic fatty acid oxidation. Regarding the substrate specificity of beta-oxidation pathway, mitochondrial and peroxisomal beta-oxidation rate of alpha-18:3-CoA, relative to 16:0- and 18:2-CoAs, was higher irrespective of the substrate/albumin ratios in the assay mixture or dietary fat sources. The substrate specificity of carnitine palmitoyltransferase I appeared to be responsible for the differential mitochondrial oxidation rates of these acyl-CoA substrates. Dietary fats rich in alpha-18:3-CoA relative to safflower oil did not affect the hepatic activity of fatty acid synthase and glucose 6-phosphate dehydrogenase. It was suggested that both substrate specificities and alterations in the activities of the enzymes in beta-oxidation pathway play a significant role in the regulation of the serum lipid concentrations in rats fed alpha-18:3.     

Diurnal rhythms of retinal phospholipid synthetic enzymes are retained but their activities are decreased in rats under alpha-linolenic acid deficiency

Rats fed a safflower oil (alpha-linolenic acid (ALNA)-deficient) diet over the course of two generations had significantly decreased docosahexaenoic acid (22:6n-3) and increased docosapentaenoic acid (22:5n-6) contents in the major retinal phospholipids such as phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylserine (PS) when compared with those fed a perilla oil (ALNA-sufficient) diet, but the compositions of phosphatidylinositol acyl chains were relatively unaffected. The contents of individual phospholipids in the retina were essentially the same for the two dietary groups. The activities of the rate-limiting enzymes in the de novo synthesis of PC and PE, CTP:phosphocholine cytidylyltransferase (CT), and CTP:phosphoethanolamine cytidylyltransferase (ET), respectively, were measured in the retinas excised at 5:00, 9:00, 13:00, and 17:00 h from rats adapted to a 24-h cycle with lights on from 7:00 to 19:00 h. Both enzymes exhibited significant diurnal rhythms with the lowest activities at 5:00 h and gradually increasing activities following exposure of the rats to light; the maximum activities were at 13:00 h for CT and 17:00 h for ET. The diurnal rhythms were not significantly affected by the above-mentioned diets. However, both enzyme activities at each collection time point were significantly lower in the safflower oil group than in the perilla oil group. These results suggest that retinal phospholipid turnover associated with shedding, phagocytosis, and resynthesis of the rod outer segments is limited by ALNA deficiency.     

Manganese absorption and retention in rats is affected by the type of dietary fat

There is evidence that manganese (Mn) metabolism may be altered by the form and amount of dietary fat. Also, iron (Fe) absorption is greater with saturated fats, as compared to polyunsaturated fatty acids (PUFAs). The absorption of Fe and Mn are interrelated in many aspects; therefore, the form of dietary fat may indirectly alter Mn absorption. The reported studies were conducted to determine whether saturated fat, as compared to unsaturated fat, affected Mn absorption, retention, and metabolism. In experiment I, adult rats were fed diets containing either 0.7 or 100.4 μg/g Mn with the fat source as high-linoleic safflower oil or stearic acid. After 2 wk of equilibration, the animals were fed a test meal of ⁵⁴Mn followed by whole-body counting for 10 d. Manganese absorption was significantly (p<0.05) lower in the stearic acid group (0.9–4.8%) than in the safflower oil group (20–33.8%); however, the biological half-life was shorter in the safflower oil group. Retention of ⁵⁴Mn and total Mn was always significantly (p<0.05) greater in the safflower oil group when dietary Mn was low, but it was the same when dietary Mn was high. In experiment II, weanling rats were fed 1.3, 39.3, or 174.6 μg Mn/g and either stearate, high-oleic safflower oil or high-linoleic safflower oil for 8 wk. Long-term feeding of the stearate and low Mn-containing diet resulted in a significant (p<0.0001) reduction in heart superoxide dismutase activity and kidney and liver Mn concentrations compared to the other diets. These data show that stearic acid inhibitits Mn absorption, but it may not inhibit Mn retention when dietary Mn is high. The U.S. Department of Agriculture, Agricultural Research Service, Northern Plains Area, is an equal opportunity/affirmative action employer and all agency services are available without discrimination. Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable.     

Dietary docosahexaenoic acid ameliorates, but rapeseed oil and safflower oil accelerate renal injury in stroke-prone spontaneously hypertensive rats as compared with soybean oil, which is associated with expression for renal transforming growth factor-beta, fibronectin and renin

We have noted that n-3 fatty acid-rich oils, such as fish oil, perilla oil and flaxseed oil as well as ethyl docosahexaenoate (DHA) prolonged the survival time of stroke-prone spontaneously hypertensive rats (SHRSP) rats by approximately 10% as compared with linoleate (n-6)-rich safflower oil. Rapeseed oil with a relatively low n-6/n-3 ratio unusually shortened the survival time by approximately 40%, suggesting the presence of minor components unfavorable to SHRSP rats. This study examined the effects of dietary oils and DHA on renal injury and gene expression related to renal injury in SHRSP rats. Rats fed rapeseed oil- and safflower oil-supplemented diets developed more severe proteinuria than those fed soybean oil-supplemented diet used as a control, but there were no significant differences in blood pressure. In contrast, the DHA-supplemented diet inhibited the development of proteinuria and suppressed hypertension. The mRNA levels for renal TGF-beta, fibronectin and renin were higher in the rapeseed oil and safflower oil groups after 9 weeks of feeding of the experimental diet than in the soybean oil and DHA groups. The fatty acid composition of kidney phospholipids was markedly affected by these diets. These results indicate that the renal injury observed in the groups fed safflower oil with a high n-6/n-3 ratio and rapeseed oil with presumed minor components is accompanied by increased expression of the TGF-beta, renin and fibronectin genes, and that dietary DHA suppresses renal injury and gene expression as compared with soybean oil.     

β-adducin (Add2) KO mice show synaptic plasticity, motor coordination and behavioral deficits accompanied by changes in the expression and phosphorylation levels of the α- and γ-adducin subunits

Adducins are a family of proteins found in cytoskeleton junctional complexes, which bind and regulate actin filaments and actin-spectrin complexes. In brain, adducin is expressed at high levels and is identified as a constituent of synaptic structures, such as dendritic spines and growth cones of neurons. Adducin-induced changes in dendritic spines are involved in activity-dependent synaptic plasticity processes associated with learning and memory, but the mechanisms underlying these functions remain to be elucidated. Here, β-adducin knockout (KO) mice were used to obtain a deeper insight into the role of adducin in these processes. We showed that β-adducin KO mice showed behavioral, motor coordination and learning deficits together with an altered expression and/or phosphorylation levels of α-adducin and γ-adducin. We found that β-adducin KO mice exhibited deficits in learning and motor performances associated with an impairment of long-term potentiation (LTP) and long-term depression (LTD) in the hippocampus. These effects were accompanied by a decrease in phosphorylation of adducin, a reduction in α-adducin expression levels and upregulation of γ-adducin in hippocampus, cerebellum and neocortex of mutant mice. In addition, we found that the mRNA encoding β-adducin is also located in dendrites, where it may participate in the fine modulation of LTP and LTD. These results strongly suggest coordinated expression and phosphorylation of adducin subunits as a key mechanism underlying synaptic plasticity, motor coordination performance and learning behaviors.     

Dietary fat modulation of apoA-II metabolism and prevention of senile amyloidosis in the senescence- accelerated mouse

Senescence-accelerated mouse-prone (SAMP1; SAMP1@Umz) is an animal model of senile amyloidosis with apolipoprotein A-II (apoA-II) amyloid fibril (AApoAII) deposits. This study was undertaken to investigate the effects of dietary fats on AApoAII deposits in SAMP1 mice when purified diets containing 4% fat as butter, safflower oil, or fish oil were fed to male mice for 26 weeks. The serum HDL cholesterol was significantly lower (P < 0.01) in mice on the diet containing fish oil (7.4 +/- 3.0 mg/dl) than in mice on the butter diet (38.7 +/- 12.5 mg/dl), which in turn had significantly lower (P < 0.01) HDL levels than mice on the safflower oil diet (51.9 +/- 5.6 mg/dl). ApoA-II was also significantly lower (P < 0.01) in mice on the fish oil diet (7.6 +/- 2.7 mg/dl) than on the butter (26.9 +/- 7.3 mg/dl) or safflower oil (21.6 +/- 3.7 mg/dl) diets. The mice fed fish oil had a significantly greater ratio (P < 0.01) of apoA-I to apoA-II, and a smaller HDL particle size than those fed butter and safflower oil. Severe AApoAII deposits in the spleen, heart, skin, liver, and stomach were shown in the fish oil group compared with those in the butter and safflower oil groups (fish oil > butter > safflower oil group, P < 0.05). These findings suggest that dietary fats differ in their effects on serum lipoprotein metabolism, and that dietary lipids may modulate amyloid deposition in SAMP1 mice.     

Effects of the degree of saturation of dietary fat on the hepatic production of lipoproteins in the African green monkey

The cholesteryl ester content of plasma low density lipoproteins (LDL) in monkeys has previously been shown to be related to the rate of hepatic cholesterol secretion and cholesteryl ester content of newly secreted lipoproteins in the isolated perfused liver. In the present studies, African green monkeys were fed diets containing cholesterol and 40% of calories as either butter or safflower oil in order to determine the effects of saturated versus polyunsaturated dietary fat on hepatic lipoprotein secretion. The rate of cholesterol accumulation in liver perfusates was correlated with the size of the donor's plasma LDL, but for any rate, a smaller plasma LDL was found in donor animals of the safflower oil group than in those of the butter group. Hepatic very low density lipoproteins (VLDL) were smaller in the safflower oil group but contained more cholesteryl ester and fewer triglyceride molecules per particle than those from the butter group. Livers from the safflower oil group contained more cholesteryl ester and less triglyceride than those from the butter group. The cholesteryl ester percentage composition of hepatic VLDL resembled that of the liver in each group. The data show that dietary polyunsaturated fat decreased plasma LDL size even though it increased the cholesteryl ester content of lipoproteins secreted by the liver. Therefore, intravascular formation of plasma LDL from hepatic precursor lipoproteins appears to include the removal of relatively greater amounts of cholesteryl esters from the precursor lipoproteins in polyunsaturated fat-fed animals.     

Influence of dietary safflower oil and tallow on growth, plasma lipids and lipogenesis in rats, pigs and chicks.

Rats, chicks and pigs were fed diets containing safflower oil or tallow. Plasma triglyceride levels were elevated when tallow, rather than safflower oil was added to the diet of rats, unchanged in chicks and lowered when tallow, rather than safflower oil was fed to pigs. The rate of fatty acid synthesis in rat and chick liver was higher, whereas the rate of lipogenesis in adipose tissue preparations from rats and pigs was lower when tallow, rather than safflower oil was fed. These results indicate that there are species-specific, as well as organ-specific, metabolic responses to various dietary fats.     

Evaluation of safflower meal as a protein source in diets of rainbow trout [Oncorhynchus mykiss,Walbaum, 1792)]*

The effects of different levels of safflower meal (a residue of the plant oil extraction process) in diets of rainbow trout (Oncorhynchus mykiss) on growth performance, nutrient digestibility and body composition were investigated. Four different diets containing 0% (Control group), 10% (Diet 1), 15% (Diet 2) and 20% (Diet 3) safflower meal were formulated for the fish with a mean weight of 132.70 ± 0.75 g fed for 70 days. At the end of the experiment, there were no significant differences among dietary treatments for weight gain, specific growth rate and feed conversion ratio (P > 0.05). There were also no differences in the digestibility of crude protein and crude lipid between groups (P > 0.05). Supplementation of safflower meal in the diets also had no adverse effects on body composition. The results indicate that safflower meal is a promising feed ingredient and can be used up to a concentration of 20% in the rainbow trout diet with no adverse effects on growth performance, nutrient digestibility or body composition.