Level of dietary iron,not type of dietary fat,is hyperlipidemic in copper-deficient rats

OBJECTIVE: This study was conducted to determine whether high dietary iron will negate the protective effect of unsaturated fat against hyperlipidemia. METHODS: Forty-eight weanling, male Sprague Dawley rats were randomly assigned to eight dietary groups differing in the levels of copper and iron and type of dietary fat (saturated or unsaturated). The diets were either deficient (0.6 microg Cu/g) or adequate (6.8 microg Cu/g) copper and either adequate (53 microg Fe/g) or high (506 microg Fe/g) iron. All diets contained starch as the sole source of dietary carbohydrate. RESULTS: Regardless of the type of dietary fat, three copper-deficient rats fed the high levels of dietary iron died prematurely due to ruptured hearts. Surviving rats belonging to the copper deficiency and high-dietary iron regimen developed severe anemia, enlarged hearts and livers, and exhibited the highest levels of liver iron. These rats also developed hypercholesterolemia. Triglycerides were elevated by the consumption of high iron diets. CONCLUSION: Data show that levels of dietary iron, not the type of dietary fat, are potential inducers of hypertriglyceridemia. Data also show that the combination of high iron intake and dietary copper deficiency is responsible for elevating blood cholesterol.     

Development of anemia in copper-deficient rats fed high levels of dietary iron and sucrose

The effects of dietary carbohydrate and iron on the development of copper deficiency were examined. Male Sprague-Dawley rats (n = 48) were limit-fed one of eight diets in a 2 X 2 X 2 factorial design for 19 d. Two levels of copper (0.85 or 8.6 micrograms Cu/g diet) and iron (54 or 226 micrograms Fe/g diet) and two types of carbohydrate (sucrose or cornstarch, 65.3%) were fed. Compared with control rats, copper-deficient rats had lower hematocrits, lower ceruloplasmin levels, lower tissue levels of copper and increased hepatic iron levels. Copper-deficient rats fed sucrose had significantly lower hematocrits, lower apparent absorption of copper, lower liver iron levels and higher plasma triglyceride levels than copper-deficient rats fed cornstarch. Copper-deficient rats fed sucrose with 226 micrograms Fe/g diet had hematocrit levels that were 15% lower than all other copper-deficient levels and 23% lower than control levels. Tissue levels of copper among copper-deficient rats were not affected by the type of carbohydrate or by the level of dietary iron. These data indicate that both high iron and sucrose can affect the development of the copper deficiency.     

Dietary fructose but not starch is responsible for hyperlipidemia associated with copper deficiency in rats: effect of high-fat diet

OBJECTIVE: To test the hypothesis that copper deficiency in rats may be hyperlipidemic only when the diets consumed contain nutrients which contribute to blood lipids such as fructose and high fat. METHODS: Weanling male Sprague Dawley rats were fed diets which contained either starch or fructose as their sole carbohydrate source. The diets were either inadequate (0.6 microg Cu/g) or adequate (6.0 microg Cu/g) in copper and contained either high (300 g/kg) or low (60 g/kg) fat. At the end of the 4th week the rats were killed. Livers were analyzed for copper content. Plasma was analyzed for cholesterol and triglyceride concentrations. RESULTS: High-fat diet did not increase blood lipids in rats fed a copper-deficient diet containing starch. In contrast, the combination of high-fat diet with fructose increased blood triglycerides and fructose with copper deficiency resulted in a significant increases in blood cholesterol. CONCLUSIONS: Hyperlipidemia of copper deficiency in rats is dependent on synergistic effects between dietary fructose and copper deficiency and fructose and amount of dietary fat. Hyperlipidemia does not develop if starch is the main source of dietary carbohydrate in a copper-deficient diet even if a high-fat diet is fed.     

Dietary copper, manganese and iron affect the formation of aberrant crypts in colon of rats administered 3,2'-dimethyl-4-aminobiphenyl

Aberrant crypt foci (ACF) are preneoplastic lesions for colon cancer. Altered amounts of copper-zinc (CuZnSOD) and manganese (MnSOD) superoxide dismutases have been implicated in multistage carcinogesis of both rodents and humans. Dietary factors are potential modulators of both CuZnSOD and MnSOD activity. The purpose of this study was to investigate the interactive effects of dietary copper, manganese, and iron on 3,2'-dimethyl-4-aminobiphenyl (DMABP)-induced ACF and superoxide dismutase activities in weanling rats fed low or adequate copper (0.8 or 5.1 microg Cu/g diet), low or adequate manganese (0.6 or 17 microg Mn/g diet), and adequate or high iron (37 or 140 microg Fe/g diet). Twelve rats were allowed free access to each of these eight diets for 3.5 wk prior to DMABP administration and for an additional 8 wk after the first DMABP injection. Rats fed low dietary copper had 105% (P < 0.0001) higher formation of DMABP-induced ACF than those fed adequate dietary copper. Rats ingesting low rather than adequate dietary manganese had 23% higher formation of ACF, and rats ingesting high rather than adequate dietary iron had 18% higher formation of ACF. Heart total superoxide dismutase activity was significantly correlated with the number of ACF (r = -0.43, P < 0.0001) in rats administered DMABP. These results suggest that dietary alterations that affect superoxide dismutase activity may affect cancer susceptibility.     

Influence of iron and the sex of rats on hematological, biochemical and immunological changes during copper deficiency

The influence of dietary iron and the sex of rats on suppressed lymphocyte functions caused by copper deficiency was examined. Male and female weanling Lewis rats were fed two concentrations of copper (0.6 or 5.6 micrograms Cu/g diet) and iron (50 or 300 micrograms Fe/g diet) for 42 d. Regardless of dietary iron concentrations, male and female rats consuming low copper diets had lower serum ceruloplasmin activity and serum and liver copper concentrations than those fed the high copper diet. However, hemoglobin and hematocrit levels were higher in copper-deficient females than in copper-deficient males and were unaffected by copper deficiency in females fed the high iron diet. Copper-deficient females also had higher serum and liver iron concentrations than copper-deficient males. Proliferation of concanavalin A (Con A)-stimulated spleen lymphoid cells (SLC) was suppressed in copper-deficient males and females, but the suppression was less in the females. Thus, the primary cause of suppressed SLC proliferation in copper-deficient rats is poor copper status; poor iron status induced by copper deficiency had little influence on proliferation.     

Effect of dietary homocysteine on copper status in rats

The effect on copper status of diets containing homocysteine, an intermediate in the transsulfuration pathway of methionine metabolism, was investigated in rats. Two groups of six male weanling Sprague-Dawley rats were provided with deionized water and pair-fed diets that were adequate (14.0 mg/kg) or deficient (1.3 mg/kg) in Cu to groups fed diets similarly adequate or deficient in Cu but containing DL-homocysteine (10 g/kg). Hemoglobin concentration, tissue Cu levels and the activities of the Cu-dependent enzymes--ceruloplasmin, superoxide dismutase and cytochrome c oxidase--were markedly lowered by Cu-deficient diets and by homocysteine. These dietary treatments also lowered the activity of glutathione peroxidase and produced concomitant increases in the activity of manganese-dependent superoxide dismutase and iron levels in the liver. However, dietary homocysteine decreased hepatic Mn and low Cu diets decreased cardiac iron content. Moreover, both dietary treatments significantly lowered kidney Fe levels. Homocysteine increased heart, liver and kidney weights (g/100 g body tissue) and greatly elevated the level of thiobarbituric acid reactive substances (TBARS) in heart tissue. These results indicate that dietary homocysteine can markedly lower Cu status in rats and result in tissue redistribution of Fe and increased cardiac levels of TBARS, a measure of lipid peroxidation.     

Beta-carotene 15,15'-dioxygenase activity is responsive to copper and iron concentrations in rat small intestine

OBJECTIVE: Previous in vitro studies have suggested that beta-carotene 15,15'-dioxygenase is an iron-dependent enzyme. However, in vivo, it is difficult to alter iron tissue concentration by varying dietary iron because of homeostatic control. On the other hand, an interaction between iron and copper has been shown, i.e., copper-deficiency results in an increase of iron in rat liver. Therefore, we hypothesized that intestinal iron concentration could be increased by copper-deficiency. Our objective was to examine the effects of iron as affected by dietary copper on beta-carotene 15,15'-dioxygenase activity in the small intestine. METHODS: Weanling male Sprague-Dawley rats (40 to 45g) were divided into four dietary groups: two copper-adequate groups (6.0 microg Cu/g diet) and two copper-deficient groups (0.6 microg Cu/g) combined with either normal iron (44 microg Fe/g) or high iron (87 microg Fe/g). Iron and copper concentrations were determined by atomic absorption spectrophotometry and the dioxygenase activity by reverse phase HPLC. RESULTS: Intestinal copper concentration was significantly reduced (40%) by the consumption of the copper-deficient diets, but intestinal iron was not changed by doubling dietary iron in rats fed either copper-adequate or copper-deficient diets. However, as hypothesized, the two copper-deficient groups exhibited higher intestinal iron concentration (> or =137%, p<0.001) than the copper-adequate controls. In addition, intestinal beta-carotene 15,15'-dioxygenase activity was increased by 27% and 106%, respectively, for copper-deficient rats fed either normal or high iron diets, compared to the respective copper-adequate controls (p<0.01). The dioxygenase activity was not significantly affected by dietary iron in either copper-adequate or copper-deficient groups. Finally, the enzyme activity was positively correlated (r=0.67, p<0.0001) with iron concentration and negatively correlated (r=-0.49, p<0.01) with copper concentration in small intestine. CONCLUSIONS: Intestinal beta-carotene 15,15'-dioxygenase may be an iron-dependent enzyme sensitive to copper status in vivo.     

The effect of dietary fat and salt on blood pressure,renal and aortic prostaglandins

The pressor effects of fat and salt were examined in male Sprague-Dawley rats. Rats fed high carbohydrate (5% corn oil), high salt (8% NaCl) diets demonstrated significant elevations in blood pressure within one week of diet introduction which persisted throughout the 9 week experimental period. High saturated fat (5% corn oil-15% coconut oil) diets promoted a significant elevation in blood pressure, irrespective of the level of dietary salt. High dietary salt, as opposed to basal levels, tended to decrease the blood pressure of rats fed a diet containing all unsaturated fat (20% corn oil). The greatest percent increase in the renal vasodilator prostaglandin E₂ was measured in rats fed the high unsaturated-basal salt diet compared to all other dietary treatments. A hypervolemic effect of high levels of dietary salt was demonstrated in the high carbohydrate, all unsaturated fat and high saturated fat groups. These results demonstrate that the amount and type of dietary fat interact with the level of dietary salt to influence blood pressure in rats.     

Comparative Cholesterol Lowering Properties of Vegetable Oils: Beyond Fatty Acids

Objective: Our laboratory has previously reported that the hypolipidemic effect of rice bran oil (RBO) is not entirely explained by its fatty acid composition. Although RBO has up to three times more serum cholesterol-raising saturated fatty acids (SATS) than some unsaturated vegetable oils, we hypothesized that its greater content of the unsaponifiables would compensate for its high SATS and yield comparable cholesterol-lowering properties to other vegetable oils with less SATS.

Methods: To study the comparative effects of different unsaturated vegetable oils on serum lipoprotein levels, nine cynomologus monkeys (Macaca fascicularis) were fed diets, for four weeks, in a Latin square design, containing rice bran, canola or corn oils (as 20% of energy) in a basal mixture of other fats to yield a final dietary fat concentration of 30% of energy. All animals were fed a baseline diet containing 36% of energy as fat with 15% SATS, 15% monounsaturated fatty acids (MONOS) and 6% polyunsaturated fatty acids (POLYS).

Results: Despite the lower SATS and higher MONOS content of canola oil and the higher POLYS content of corn oil, RBO produced similar reductions in serum total cholesterol (TC) (?25%) and low density lipoprotein cholesterol (LDL-C) (?30%). In addition, as compared to the baseline diet, the reduction in serum TC and LDL-C cholesterol with RBO was not accompanied by reductions in high density lipoprotein cholesterol (HDL-C) which occurred with the other two dietary oils. Using predictive equations developed from data gathered from several studies with non-human primates, we noted that the observed serum TC and LDL-C lowering capabilities of the RBO diet were in excess of those predicted based on the fatty acid composition of RBO.

Conclusions: These studies suggest that non-fatty acid components (unsaponifiables) of RBO can contribute significantly to its cholesterol-lowering capability.     

Total body content of copper and other essential metals in rats fed fructose or starch

The effects of dietary carbohydrate and copper on whole body levels of copper and other essential minerals were investigated. Weaned male rats were pair-fed diets containing 62% fructose or cornstarch with either adequate (6–7 mg/kg) or deficient (0.5–0.7 mg/kg) copper (Cu) for 32–33 days. Recommended levels of other minerals were present in all diets. Total copper in whole body was approximately 2-fold higher in rats fed copper-supplemented diets than copper-deficient diets and was independent of the type of dietary carbohydrate. Whole body levels of zinc, iron, manganese and magnesium were independent of dietary copper and carbohydrate. Selenium content of rats fed copper-deficient diet with fructose was 35% higher than in those fed copper-adequate diet with fructose. Rats fed the copper-deficient diet containing starch had a whole body calcium level 17–23% lower than that of the other dietary groups. These results demonstrate that the copper-carbohydrate interaction is not a result of carbohydrate-dependent effects on the retention of dietary copper and other essential minerals.     

Figure and Fitness

The objective of the present study was to establish whether copper (Cu)-deficient rats fed a diet containing fructose as their sole carbohydrate source require more biotin than the recommended 2 mg/kg diet when egg-white serves as the dietary protein.

Eighty weanling male Sprague-Dawley rats were randomly divided into 8 groups according to type of dietary carbohydrate (starch or fructose), level of Cu (0.6 micrograms Cu/g diet or 6.0 micrograms Cu/g diet) and level of biotin (2 mg/kg diet or 10 mg/kg diet).

Regardless of the level of dietary biotin, Cu-deficient rats fed a fructose-containing diet exhibited growth retardation, anemia, atrophied pancreata, enlarged hearts and similar death rates. The remaining Cu-deficient rats fed fructose were emaciated and sick regardless of dietary biotin levels. The concentration of biotin in serum and biotin content of liver of rats fed fructose were higher than corresponding values from rats fed starch.

Cu-deficient rats fed fructose are not deficient in biotin compared to published normal values. Supplementation of 10 mg/biotin/kg diet did not improve morbidity or mortality and therefore was not beneficial.     

Dietary copper primarily affects antioxidant capacity and dietary iron mainly affects iron status in a surface response study of female rats fed varying concentrations of iron, zinc and copper.

This study was designed to examine the interactions among dietary iron (Fe), copper (Cu), and zinc (Zn) and their effects on Fe status and oxidative stress in female rats. In a three-factor central composite response surface design, rats were assigned to 15 groups and fed modified AIN-93G basal diets with varying amounts of Fe and Zn (7.0, 15.5, 45.8, 135.6, or 300 micrograms/g diet) and Cu (0.5, 1.1, 3.2, 9.2, or 20 micrograms/g diet) for 6 wk. Variations in hemoglobin, hematocrit, and serum ferritin were mainly related to dietary Fe. Liver nonheme Fe was directly affected by dietary Fe and was slightly attenuated by interactions between Cu and Zn, and Zn and Fe. Serum ceruloplasmin activity was primarily determined by an interaction between Cu and Zn with substantial moderation by the quadratic effect of dietary Cu. Liver and heart total superoxide dismutase (SOD) and Cu/Zn SOD activities were directly affected by dietary Cu. Dietary Fe was the only significant, yet weak, predictor of liver thiobarbituric acid reactive substances (TBARS) and vitamin E content and serum triacylglycerols. Variability in serum Cu was mostly determined by the interaction between Cu and Fe, with modification from the quadratic effect of dietary Cu. Serum Zn varied with dietary Zn with a small negative influence from the interaction between Cu and Fe. In summary, Fe status was minimally influenced by dietary Zn or Cu, and Fe intakes 10-fold greater than required did not induce overt oxidative stress in female rats. In addition, measures of antioxidant capacity were primarily influenced by dietary Cu and were optimal at moderate intakes of this micronutrient.     

Effects of Dietary Fat and Endurance Exercise on Plasma Cortisol,Prostaglandin E2, Interferon-γ and Lipid Peroxides in Runners

Objective: Exercise and the neuroendocrine and oxidative stress it elicits on immune function is modulated by dietary fat intake. The effects of increasing dietary fat on endurance exercise-induced alterations (80% of V?O_2max for 2 hours) in the plasma levels of cortisol and prostaglandin E₂ (PGE₂), interferon-γ (IFN-γ) and lipid peroxides were investigated. As higher levels of cortisol, PGE₂ and lipid peroxides could be immunosuppressive, the effects of different levels of dietary fat on these measures in runners were determined.

Methods: Healthy trained runners (males and females) consumed serially 15% fat diet (of daily energy), 30% fat diet and 40% fat diets for four weeks each. In the last week of each diet period the subjects ran to exhaustion at 80% of their V?O_2max and blood was drawn pre- and post-run. Cortisol, IFN-γ, PGE₂ and lipid peroxides were determined using standard techniques.

Results: Pre-exercise levels of plasma cortisol were elevated, IFN-γ was unchanged and PGE₂ and lipid peroxides decreased on the 40%F diet compared to 30%F and 15%F. Post-exercise levels of plasma cortisol (p < 0.004), PGE₂ (p < 0.0057) and lipid peroxide levels increased (p < 0.0001) after endurance exercise on all diets. The rates of increase of plasma cortisol levels during exercise were similar on all three diets. Although absolute cortisol levels were higher in the high fat group, the rate of increase of plasma cortisol level during exercise was similar on each diet. The dietary fat levels did not affect IFN-γ, however, PGE₂ and lipid peroxides decreased with increasing fat at baseline at 40%F level (p < 0.01; 30%F vs. 40%F: p < 0.002; 15%F vs. 40%F: p < 0.007).

Conclusions: Data from the present study suggest that higher levels of fat in the diet, up to 40%, increase endurance running time without adverse effects on plasma cortisol, IFN-γ, and lipid peroxide levels.     

Effect of copper deficiency on erythrocyte membrane proteins of rats

The effects of copper deficiency on the proteins of rat erythrocyte membranes were assessed by electrophoretic analysis. For 42 d, rats were fed diets containing less than 1 ppm Cu with 35 or 250 ppm Fe or 5 ppm Cu with 35 or 250 ppm Fe. Electrophoresis of erythrocyte membrane proteins indicated a significant increase in the amount of a 170,000-dalton protein in rats fed copper-deficient diets. High dietary iron reduced the amount of the 170,000-dalton protein in erythrocyte membranes from rats in both the copper-deficient and copper-adequate groups. However, feeding high dietary iron to copper-deficient rats did not reduce the amount of the protein to the level found in rats fed the copper-adequate diet containing 35 ppm Fe. Triton X-100 extraction of erythrocyte membranes demonstrated that the 170,000-dalton protein was associated with the membrane cytoskeleton. Thus, copper deficiency possibly alters the cell's mechanical properties and consequently decreases erythrocyte survivability by modifying the membrane cytoskeleton.     

Dietary cellulose, zinc and copper: effects on tissue levels of trace minerals in the rat.

This study was designed to examine the effect of graded levels of cellulose, zinc and copper on tissue mineral levels. Tissue mineral levels were assayed by atomic absorption spectrophotometry in samples collected from a study which involved 12 treatments in a 3 X 2 X 2 factorial arrangement. This study involved three levels of cellulose (0, 8, and 16% of the diet), two levels of Cu (deficient and adequate; 2 and 18 mg/kg of diet, respectively), and two levels of Zn (marginal and abundant; 10 and 120 mg/kg of diet, respectively). Six weanling, male Sprague-Dawley rats were assigned to each treatment and after 9 weeks they were killed. Reductions of tissue Cu content were observed in the serum, liver, tibia and testis of the rats fed the Cu-deficient diets. The Fe content of the tibia and testis was reduced, but that of liver was elevated in the rats fed Cu-deficient diets. Reductions in tibial Zn levels were observed in the rats fed marginal-Zn as compared to those fed the abundant-Zn diets; and in the rats fed Cu-adequate as compared to those fed Cu-deficient diets. Increases in cellulose resulted in increased liver and testicular Cu content only in rats fed the Cu-deficient diets. Additions of cellulose appeared to have no adverse effect on the distribution of Zn, Cu and Fe in tissues which are sensitive to dietary deficiencies. With the exception of rats fed the copper-deficient, marginal zinc diets, the rats fed the other diets demonstrated a small reduction in serum zinc values as cellulose was increased.     

The Effect of Short-Term (21-Day) Orlistat Treatment on the Physiologic Balance of Six Selected Macrominerals and Microminerals in Obese Adolescents

Objectives: Orlistat is a gastrointestinal lipase inhibitor used to reduce dietary fat absorption and could be used to treat overweight and obesity in adolescents. The primary objective was to assess whether orlistat has an effect on the physiologic balance of three macrominerals (calcium, phosphorus and magnesium) and three microminerals (iron, zinc and copper).

Methods: This was a 21-day, double-blind, randomized, parallel-group, placebo-controlled mineral balance study conducted in adolescent obese volunteers (BMI ≥ 85th percentile, adjusted for age and gender). Subjects were maintained on a hypocaloric diet with a normal daily mineral content in both treatment groups and received oral treatment with orlistat 120 mg (n = 16) or placebo (n = 16) three times daily for 21 days. Following a 14-day equilibration period, balances for calcium, phosphorus, magnesium, iron, copper and zinc were measured for days 15–21. Serum and urine electrolytes were also measured at baseline and at the end of treatment.

Results: On average, orlistat inhibited dietary fat absorption by ～27%. This degree of dietary fat inhibition caused no significant changes in mineral balance between orlistat and placebo groups. In addition, serum and urine electrolytes (sodium and potassium) as well as urinary creatinine excretion were not affected by orlistat treatment. Orlistat was well tolerated; adverse events occurred mainly in the gastrointestinal tract and were of mild or moderate intensities.

Conclusions: Administration of orlistat had no significant effect on the balance of six selected minerals in adolescent obese patients.     

Adverse effects of high dietary iron and ascorbic acid on copper status in copper-deficient and copper-adequate rats

The effects of elevated dietary ascorbic acid and iron on copper utilization were examined. Male Sprague-Dawley rats were fed one of two levels of Cu (deficient, 0.42 microgram Cu/g, or adequate, 5.74 micrograms Cu/g), Fe (moderate, 38 micrograms Fe/g or high, 191 micrograms Fe/g), and ascorbic acid (low, 0% or high, 1% of the diet) for 20 d. High Fe decreased (p less than 0.05) Cu absorption only in Cu-deficient rats. High ascorbic acid significantly decreased tissue Cu levels in Cu-adequate rats. High Fe with ascorbic acid caused severe anemia in Cu-deficient rats and decreased plasma ceruloplasmin by 44% in Cu-adequate rats. Cu,Zn-superoxide dismutase activity in erythrocytes was decreased (p less than 0.05) by 14% during Cu deficiency but was not affected by Fe or ascorbic acid. These results may be important to individuals with high intakes of Fe and ascorbic acid.     

Marginal copper and high fat diet produce alterations in electrocardiograms and cardiac ultrastructure in male rats

This study investigated whether a high fat diet in tandem with a marginal copper (Cu) diet exerts deleterious effects on copper status, cardiac morphology, and electrophysiology compared to a low-fat marginal copper diet. Male weanling Long-Evans rats were fed diets containing either marginal copper (42.5 mumol/kg) or adequate copper (97.6 mumol/kg), and low fat (50.0 g/kg) or high fat (150.0 g/kg) diet for 12 wk in a 2 x 2 factorial design. To simulate the western diet, fat was composed of a 1:2 polyunsaturated:saturated fatty acids using a coconut and corn oil mixture. High dietary fat increased liver Cu concentration. Marginal copper diets decreased liver Cu,Zn-superoxide dismutase activity. Dietary copper and fat level had no effect on volume densities of mitochondria and myofibril. However, lower mitochondrial pathologic scores were observed in the rats consuming the high fat diets. Marginal copper high fat diet prolonged atrial electric depolarization (PR) and ventricular electric depolarization and repolarization (QT) intervals. This study provided direct evidence that a high fat diet can exert detrimental effects on cardiac ultrastructure and lead to alterations in electrocardiograms. The combination of marginal copper-high fat diet appears to alter cardiac electric conductivity. Longer term studies should provide information more relevant to clinical situations and morphologic changes.     

High dietary iron concentrations enhance the formation of cholesterol oxidation products in the liver of adult rats fed salmon oil with minimal effects on antioxidant status

The aim of this study was to investigate the effect of high dietary iron concentrations on the antioxidant status of rats fed two different types of fat. Four groups of male adult Sprague-Dawley rats were fed diets with adequate (50 mg iron supplemented per kg diet) or high (500 mg iron supplemented per kg diet) iron concentrations with either lard or salmon oil as dietary fat at 100 g/kg for 12 wk. The antioxidant status of the rats was profoundly influenced by the type of fat. Rats fed salmon oil diets had higher concentrations of thiobarbituric acid-reactive substances (TBARS) (P < 0.001), various cholesterol oxidation products (COP) (P < 0.001), total and oxidized glutathione (P < 0.05) and a lower concentration of alpha-tocopherol (P < 0.05) in liver and plasma than rats fed lard diets. The iron concentration of the diet did not influence the concentrations of TBARS, the activities of superoxide dismutase and glutathione peroxidase or the concentration of alpha-tocopherol in plasma or liver. The activity of catalase (P < 0.01) and the concentrations of total, oxidized and reduced glutathione (P < 0.05) in liver were slightly but significantly higher in rats fed high iron diets than in rats fed adequate iron diets, irrespective of the dietary fat. Rats fed the high iron diets with salmon oil, moreover, had higher concentrations of various COP in the liver (P < 0.001) than rats fed adequate iron diets with salmon oil. These results suggest that feeding a high iron diet does not generally affect the antioxidant status of rats but enhances the formation of COP, particularly if the diet is rich in polyunsaturated fatty acids.     

Dietary fat and selenium effects on ex vivo prostaglandin production in rat colon,kidney, and blood

The effects were determined of dietary fat and selenium (Se) levels on prostaglandin (PG) production in rat blood, kidney, and colon mucosa. For 30 weeks, male Wistar‐derived MRC rats were prefed diets containing low (6 g/367 kcal) or high (20 g/367 kcal) levels of fat with one of three Se supplements from sodium selenite: 0.0, 0.1, or 2.0 ppm Se. PG production was stopped by adding aspirin immediately following removal of the blood, kidney, and colon samples. Separate samples were allowed to incubate 10 or 60 minutes before blockage of PG production for determination of ex vivo PG production. Prostaglandin E₂ (PGE₂), thromboxane B₂, and 6‐keto‐prostaglandin F_1α (6‐keto‐PGF_1α) were measured by radioimmunoassay following separation on silicic acid columns. Basal levels of the three PGs were not influenced by diet. PGE₂ production in the colon was highest in the group fed the high‐fat diet that contained 2.0 ppm Se at 10 and 60 minutes, but PGE₂ production in the blood and kidney were not altered by diet. Thromboxane B₂ production in the rats’ blood was higher in those prefed high‐fat diets, but it was not influenced by dietary Se. Production of 6‐keto‐PGF_1α in the blood and thromboxane B₂ and 6‐keto‐PGF_1α production by the kidney and colonic mucosa were not influenced by either dietary fat or Se.