Dietary proteins modulate the effects of fish oil on triglyceridemia in the rat

Sprague-Dawley rats were fed purified diets varying in both protein (20%) and lipid (11%) content for 28 d to verify the independent and interactive effects of dietary proteins and lipids on serum and hepatic lipids, and on tissue lipoprotein lipase (LPL) activity in both fasted and postprandial states. These diets consisted of either casein-menhaden oil, casein-coconut oil, soy protein-menhaden oil (SPMO), soy protein-coconut oil, cod protein-menhaden oil, or cod protein-coconut oil. A randomized 3×2 factorial design was used. A significant protein-lipid interaction was seen on serum triglyceride levels: menhaden oil, compared with coconut oil, induced a decrease in serum triglyceride levels when combined with soy protein but not when combined with cod protein and casein. The lower serum triglyceride concentrations observed in the SPMO-fed rats could be the result of decreased hepatic triglycerides when soy protein was compared with casein and when menhaden oil was compared with coconut oil. Total LPL activity in the heart was higher in menhaden oil-fed rats than in coconut oil-fed rats in the postprandial state. The higher LPL activity in the heart could, however, explain only 10% of the reduction of serum triglycerides, contributing slightly to the lowering effects of SPMO diet on serum triglycerides. Therefore, the present results indicate that dietary proteins can modulate the effects of fish oil on triglyceridemia in the rat, and that could be mainly related to specific alterations in hepatic lipid concentrations.     

Lipoprotein lipase in rats fed fish oil: Apparent relationship to plasma insulin levels

To investigate the role of lipoprotein lipase (LPL) and hepatic lipase in the triacylglycerol lowering effects of fish oil, rats were fed lard (L), corn oil (CO) or menhaden oil (MO) as the primary fat source in otherwise identical diets. After 2 weeks, soleus muscle LPL differed between groups (MO>CO>L). Hepatic lipase did not differ between CO- and MO-fed rats but was elevated in L-fed rats. Adipose LPL did not differ between diet groups. Total epididymal fat weight was reduced in MO-fed rats. There was a significant positive correlation between adipose tissue weight and plasma free fatty acids. MO-fed rats had lower plasma insulin levels. Insulin was directly correlated with plasma triacylglycerol and glucose, consistent with a hyperinsulinemic, insulin-resistant state in CO-and L-fed rats, and a protective effect with MO feeding. In addition, insulin was directly correlated with adipose LPL. A negative relationship between soleus muscle LPL and insulin approached significance. Soleus muscle LPL was significantly inversely correlated with triacylglycerol. The data indicate that increased skeletal muscle LPL, in response to MO or a MO-induced decrease in insulin, may contribute to the triacylglycerol-lowering effects of fish oil. Decreased fat weight and adipose LPL and increased soleus muscle LPL and decreased plasma triacylglycerol suggest a shift from fat deposition to oxidation with MO feeding. The lack of response of hepatic lipase to MO feeding suggests that this enzyme does not contribute to the fish oil-stimulated lowering of plasma triacyglycerolvia hepatic reuptake of very low density lipoproteins or other triacylglycerol-rich lipoproteins.     

Effect of oxidized oil on lipogenic enzymes

Male Wistar rats were fed for 4 wk on diets containing 2% oxidized corn oil. Liver tissue was then studied to determine the effect of feeding peroxidized oil on lipogenic enzymes. Although substances which reacted with thiobarbituric acid increased in liver microsomes and mitochondria with increasing peroxide values of the dietary corn oil fed, the activities of glucose-6-phosphate dehydrogenase, malic enzyme and acetyl-CoA carboxylase in liver were unchanged. However, when rats were fed for 2 wk on diets containing 10% fat, of which 0.5, 5 or 10% was unoxidized corn oil and the remainder was hydrogenated beef tallow filler, the lipogenic enzyme activities and also the liver triglyceride levels were observed to decrease with increasing amounts of dietary corn oil. Therefore, although a synthetic diet containing corn oil was easy to oxidize spontaneously, the reductions of lipogenic enzymes in rats fed the diet would not have been caused by lipid peroxides but by unsaturated fatty acids themselves.     

Influence of medium-chain triglycerides on lipid metabolism in the rat

Lipid metabolism was studied in rats fed diets containing corn oil, coconut oil, or medium-chain triglyceride (MCT), a glyceride mixture containing fatty acids of 8 and 10 carbons in length. The ingestion of MCT-supplemented, cholesterolfree diets depressed plasma and liver total lipids and cholesterol as compared with corn oil-supplemented diets. In rats fed cholesterol-containing diets, plasma cholesterol levels were not influenced by dietary MCT, but liver cholesterol levels were significantly lower than in animals fed corn oil. In vitro cholesterol synthesis from acetate-1-¹⁴C was lower in liver slices of rats that consumed MCT than in similar preparations from corn oil-fed rats. Studies of fatty acid carboxyl labeling from acetate-1-¹⁴C and the conversion of palmitate-1-¹⁴C to C₁₈ acids by liver slices showed that chain-lengthening activity is greater in the liver tissue of rats fed MCT than in the liver of animals fed corn oil. The hepatic fatty acid desaturation mechanisms, evaluated by measuring the conversion of stearate-2-¹⁴C to oleate, was also enhanced by feeding MCT. Adipose tissue of rats fed MCT converts acetate-1-¹⁴C to fatty acids at a much faster rate than does tissue from animals fed corn oil. Evidence is presented to show that the enhanced incorporation of acetate into fatty acids by the adipose tissue of rats fed MCT represents de novo synthesis of fatty acids and not chain-lengthening activity. Data are also presented on the fatty acid composition of plasma, liver, and adipose tissue lipids of rats fed the different fats under study.     

Effects of fish oil,corn oil and lard diets on lipid peroxidation status and glutathione peroxidase activities in rat heart

In this study, we investigated the effect of various types of fats on heart lipid peroxidation status and on blood lipid parameters. Rats were fed either a low-fat diet (2.2% lard plus 2.2% corn oil), a corn oil diet (17%), a salmon oil diet (12.5%) supplemented with 4.5% corn oil, or a lard diet (15%) supplemented with 2% corn oil. All diets were supplemented with 1% cholesterol. Rats were fed for eight weeks. When compared with the low-fat diet, the salmon oil-diet intake resulted in a lower blood cholesterol, triglyceride and phospholipid concentrations (−50, −56 and −30%, respectively). Corn oil only tended to lower blood lipids; this decrease was significant for triglycerides only (−40%). The hypocholesterolemic effect of salmon oil diet is even more pronounced, if blood cholesterol values are compared with those of rats fed the lard diet. Heart lipid composition was not affected by dietary manipulations. Fatty acid composition of cardiac phosphatidylcholines and phosphatidylethanolamines, however, were altered by high-fat diets. In phosphatidylcholine, salmon oil induced a twelvefold decrease in the n−6/n−3 ratio and a 26% increase in the unsaturation index. For phosphatidylethanolamine, the n−6/n−3 ratio decreased 7.7-fold and the unsaturation index increased by 13%. A 50% decrease of the n−6/n−3 ratio was observed in animals fed the lard diet. Ultramicroscopic examination of ventricles revealed that those of the salmon oil group significantly accumulated lipofuscin-like or ceroid material, whereas this accumulation was barely detectable in hearts of the other groups. Seleniumdependent glutathione peroxidase activity tended to be the highest in hearts of rats fed the salmon oil diet; this increase is significant (+36% and +54% for total and specific activities, respectively), if values are compared with those of the rats fed the lard diet. Liver glutathione peroxidase and heart glutathione S-transferases activities remained unchanged. These results indicate that fish oil did not lower the selenium involved in glutathione peroxidase activity. This rules out that a deficiency in this enzyme was at the origin of heart lipofuscinosis. Also, it is concluded that the n−6/n−3 ratio of the diet is likely more determinant in the alteration of heart lipid peroxidation status than is the polyunsaturated/saturated ratio. Part of this work was presented at the International Congress: “Selenium in Medicine and Biology,” Avoriaz, France, March, 15–18, 1988.     

Effects of dietary corn oil and salmon oil on lipids and prostaglandin E2 in rat gastric mucosa

Three groups of male rats were fed either a corn oilenriched diet (17%, w/w), a salmon oil-enriched diet (12.5%) supplemented with corn oil (4.5%) or a low-fat diet (4.4%) for eight wk to investigate the possible relationships between dietary fatty acids and lipid composition, and prostaglandin E₂ level and phospholipase A₂ activity in the rat gastric mucosa. High-fat diets induced no important variation in total protein, phospholipid and cholesterol contents of gastric mucosa. Compared with a low-fat diet, corn oil produced a higher n−6/n−3 ratio in mucosal lipids, whereas this ratio was markedly lowered by a fish oil diet. In comparison with the low-fat diet, the production of prostaglandin E₂(PGE₂) in gastric mucosa of rats fed salmon oil was significantly, decreased by a factor of 2.8. In the corn oil group, PGE₂ production tended to decrease, but not significantly. In comparison with the low-fat diet, both specific and total gastric mucosal phospholipase A₂ activities were increased (+18 and 23%, respectively) in the salmon oil group; they were unchanged in the corn oil group. It is suggested that the decrease of gastric PGE₂ in rats fed fish oil is not provoked by a decrease in phospholipase A₂ activity but may be the result of the substitution of arachidonic acid by n−3 PUFA or activation of PGE₂ catabolism.     

Effects of dietary vitamin E,selenium, and polyunsaturated fats on in vivo lipid peroxidation in the rat as measured by pentane production

Starting at 21 days of age, groups of six rats each were fed a basal Torula yeast diet supplemented with 0,4% L-methionine and varying amounts of vitamin E as dl-alpha tocopherol acetate, selenium as sodium selenite, and with either 10% stripped corn oil, stripped lard, or coconut oil. By 7 wk, pentane production by rats fed a corn oil diet deficient in both vitamin E and selenium was twice that by rats fed 0.1 or 1 mg of selenium per kg of the same basal diet. Blood glutathione peroxidase activity after 7 wk was proportional to the logarithm of dietary selenium. Groups of rats fed the vitamin E- and selenium-deficient diets with lard or coconut oil had one-half the pentane production of rats fed the vitamin E- and selenium-deficient corn oil diets. The plasma level of linoleic plus arachidonic acid was 1.8 times greater on a wt % basis in rats fed corn oil than in rats fed lard or coconut oil as the fat source. Pentane production by rats fed 40 i.u. dl-alpha tocopherol acetate per kg of the selenium-deficient corn oil diet was one-sixth of that by rats fed the same diet without vitamin E; the plasma of the rats fed the vitamin E-supplemented corn oil diet had a level of vitamin E that was about six times greater than that of the rats fed the vitamin E-deficient corn oil diet.     

Adenylate cyclase and β-receptors in salivary glands of rats fed diets containingtrans fatty acids

The effects oftrans fatty acids on adenylate cyclase were determined in the submandibular salivary glands (SMSG) of rats fed diets containing 20% corn oil, 20% partially hydrogenated soybean oil (PHSBO) or 18% PHSBO + 2% corn oil. The fluoride-and isoproterenol-stimulated adenylate cyclase activities were higher in the SMSG from rats fed 20% PHSBO than in the control group fed 20% corn oil. The feeding of 2% corn oil with the diet containing 18% PHSBO resulted in a complete restoration of isoproterenol-stimulated and a partial restoration of fluoride-stimulated adenylate cyclase activity. There was no significant difference in the concentration of the β-adrenergic receptor or in the receptor-binding affinity constants among the three dietary groups as measured by [³H]dihydroalprenolol (DHA)-binding. Higher fluorescence polarization of diphenyl hexatriene (DPH) was observed in SMSG membranes of rats fed diet containing 20% PHSBO than in the other two oils, suggesting that membrane fluidity may play a role in adenylate cyclase activity.     

Effect of dietary palm oil and its fractions on rat plasma and high density lipoprotein lipids

Male Sprague Dawley rats were fed semipurified diets containing 20% fat for 15 weeks. The dietary fats were corn oil, soybean oil, palm oil, palm olein and palm stearin. No differences in the body and organ weights of rats fed the various diets were evident. Plasma cholesterol levels of rats fed soybean oil were significantly lower than those of rats fed corn oil, palm oil, palm olein or palm stearin. Significant differences between the plasma cholesterol content of rats fed corn oil and rats fed the three palm oils were not evident. HDL cholesterol was raised in rats fed the three palm oil diets compared to the rats fed either corn oil or soybean oil. The cholesterol-phospholipid molar ratio of rat platelets was not influenced by the dietary fat type. The formation of 6-keto-PGF_1α was significantly enhanced in palm oil-fed rats compared to all other dietary treatments. Fatty acid compositional changes in the plasma cholesterol esters and plasma triglycerides were diet regulated with significant differences between rats fed the polyunsaturated corn and soybean oil compared to the three palm oils.     

Effect of conjugated linoleic acid on body composition in mice

The effects of conjugated linoleic acid (CLA) on body composition were investigated. ICR mice were fed a control diet containing 5.5% corn oil or a CLA-supplemented diet (5.0% corn oil plus 0.5% CLA). Mice fed CLA-supplemented diet exhibited 57% and 60% lower body fat and 5% and 14% increased lean body mass relative to controls (P<0.05). Total carnitine palmitoyltransferase activity was increased by dietary CLA supplementation in both fat pad and skeletal muscle; the differences were significant for fat pad of fed mice and skeletal muscle of fasted mice. In cultured 3T3-L1 adipocytes CLA treatment (1×10⁻⁴ M) significantly reduced heparin-releasable lipoprotein lipase activity (−66%) and the intracellular concentrations of triacylglyceride (−8%) and glycerol (−15%), but significantly increased free glycerol in the culture medium (+22%) compared to control (P<0.05). The effects of CLA on body composition appear to be due in part to reduced fat deposition and increased lipolysis in adipocytes, possibly coupled with enhanced fatty acid oxidation in both muscle cells and adipocytes.     

Dietary fat and colon cancer: Animal model studies

Since it was first suggested that high dietary fat is a risk factor in colon cancer, there have been several studies to test this hypothesis. Epidemiologic studies suggested a positive association between dietary fat and colon cancer. Laboratory animal model studies demonstrated that not only the amount of rat, but also types of fat differing in fatty acid composition are important determining factors in colon tumor development. Chemically-induced colon tumor incidence was increased in rats fed the semipurified diets containing 23% corn oil, safflower oil, lard or beef tallow (high-fat) as compared to those fed 5% corn oil, safflower oil, lard or beef tallow diets (low-fat). Diets containing 23% conconut oil, olive oil or fish oil, or high-fat diets containing varying levels oftrans fat, had no colon tumor-enhancing effect compared to their respective low fat diets. The stage at which the effect of dietary fat is exerted appears to be mostly during the post-initiation phase of colon carcinogenesis. Lack of a colon tumor enhancing effect of dietary fish oil is observed both during the initiation and postinitiation phases. The mechanisms by which various dietary fats increase colon carcinogenesis are not fully understood. In most instances, however, the high-fat diet appears to enhance tumorigenesis through elevation of agents, such as secondary bile acids, that act as promoters of tumor development. Lack of colon tumor promotion by dietary fish oil andtrans fat appears to be mediated through their effect on mucosal ornithine decarboxylase activity, colonic secondary bile acids and/or prostaglandin synthesis. Based on a paper presented at the Symposium on Lipids in Cancer held at the AOCS Annual Meeting, Baltimore, MD, April 1990.     

The effects of streptozotocin diabetes on tissue specific lipase activities in the rat

Fasting in normal rats produced a fall in hepatic triglyceride lipase (H-TGL) activity as well as lipoprotein lipase (LPL) activities of adipose tissue and psoas minor muscle. On the other hand, LPL activities of heart and diaphragm were not decreased by fasting; the former, in fact, was increased significantly. Changes in tissue specific lipase activity caused by withdrawal of insulin from insulin-treated diabetic animals paralleled in direction the changes induced by starvation of normal rats. Furthermore, it was shown in the present paper that the tissue specific lipase activity of diabetic rats became stuck in the starve phase of the starve-feed cycle regardless of dietary intake. The changes of the tissue specific lipase activities, especially of liver, adipose tissue and heart, appeared to coincide with those of plasma insulin levels. These results strongly suggest that the tissue specific lipase system is under hormonal regulation by insulin. Streptozotocin diabetes produced hypertriglyceridemia. The possible mechanism of the hypertriglyceridemia in diabetic animals was discussed in connection with the role of the tissue specific lipase system in the serum triglyceride metabolism.     

Effects of low casein and fish oil on hyperlipidemia and proteinuria in nephritic rats

The effects of amino acid-fortified low casein and fish oil (FO) diets on hyperlipidemia and proteinuria were studied in rats with nephrotoxic serum nephritis. After an antiserum injection, rats were maintained for 14 d on four different experimental diets: a 20% casein diet containing corn oil (CO) or FO, or an 8% casein diet supplemented with cystine plus threonine containing CO or FO. The 8% casein diets reduced urinary protein excretion in nephritic rats without inducing severe growth retardation or fatty liver compared with the basal 20% casein diets. Both the 8% casein diet and the FO diet decreased serum cholesterol, triglyceride and phospholipid levels in nephritic rats, and nonesterified fatty acid levels were decreased by FO feeding. In nephritic animals, hepatic cholesterol synthesis was decreased by the 8% casein diets compared with the 20% casein diets, and tended to be reduced by FO feeding between groups at the same casein levels. No effect of diet was observed on fatty acid synthesis among the nephritic rats. FO administration to the nephritic animals suppressed fecal steroid excretion. While lipoprotein lipase activity was unchanged among the nephritic rats, hepatic triglyceride lipase activity was reduced by either the 8% casein or FO diet. The results suggest that the hypolipidemic action of low casein diets may, at least in part, be due to reduced hepatic cholesterol synthesis and suppressed triglyceride secretion from the liver. They also suggest that the hypolipidemic action of FO may, at least in part, be due to reduced hepatic cholesterol synthesis and decreased fatty acid mobilization from peripheral adipose tissue.     

Dietary Source of Stearidonic Acid Promotes Higher Muscle DHA Concentrations than Linolenic Acid in Hybrid Striped Bass

Rapid expansion of aquacultural production is placing increasing demand on fish oil supplies and intensified the search for alternative lipid sources. Many of the potential alternative sources contain low concentrations of long chain n-3 fatty acids and the conversion of dietary linolenic acid to longer chain highly unsaturated fatty acids is a relatively inefficient process in some species. A 6-week study was conducted to compare tissue fatty acid (FA) concentrations in hybrid striped bass fed either 18:3n-3 (α-linolenic acid; ALA) or 18:4n-3 (stearidonic acid; SDA). Hybrid striped bass were fed either a control diet containing fish oil, or diets containing ALA or SDA at three different levels (0.5, 1 and 2% of the diet). There were no significant differences in whole animal responses between fish fed ALA or SDA. Liver and muscle concentrations of ALA and SDA were responsive to dosages fed. However, only 22:6n-3 concentrations in muscle were significantly affected by dietary source of 18 carbon precursors. Muscle 22:6n-3 concentrations were significantly higher in fish fed SDA compared to fish fed ALA. Based on these data, it appears that feeding SDA can increase long chain n-3 fatty acid concentrations in fish muscle.     

Dietary Monounsaturated Fatty Acids but not Saturated Fatty Acids Preserve the Insulin Signaling Pathway via IRS-1/PI3K in Rat Skeletal Muscle

Saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) show different effects on the development of insulin resistance. In this study, we compared the effect of dietary SFA and MUFA on the insulin signaling pathway in the skeletal muscle of a type 2 diabetic animal model. Twenty-nine-week-old male Otsuka Long-Evans Tokushima fatty (OLETF) rats were randomly divided into three groups and fed one of the following diets for 3 weeks; a normal chow diet, an SFA (lard oil) enriched or a MUFA (olive oil) enriched high-fat diet. The vastus lateralis muscle was used for analyses. Insulin tolerance test showed improved insulin sensitivity in rats fed the MUFA diet, as compared to those fed the SFA diet (p < 0.001). The SFA diet reduced IRS-1 expression and phosphorylated PI3K levels in skeletal muscle, as compared with a chow diet (p < 0.001, respectively). On the contrary, muscle IRS-2 expression and phosphorylated ERK1/2 was significantly increased in rats fed the SFA diet (p < 0.001, respectively). Membrane translocation of glucose transporter type 4 decreased in the skeletal muscle of rats fed the SFA diet, as compared to those fed a chow diet (p < 0.001). These changes in insulin signaling pathway in skeletal muscle were not observed in rats fed the MUFA diet. In conclusion, the beneficial effect of dietary MUFA on insulin sensitivity is associated with a conserved IRS-1/PI3K insulin signaling pathway which was altered by dietary SFA.     

Digestion and absorption of free and esterified fish oil fatty acids in rats

This study was designed to test the hypotheses that digestibility and post-absorption metabolism of fish oil are influenced by impaired lipolysis and by the stereospecific composition of its triacylglycerols. Male Wistar rats were fed nonpurified diets containing one of the following fat sources: 9% native fish oil (NFO), 9% autorandomized fish oil (RFO), 8.1% fish oil-derived free fatty acids (FO-FFA) plus 0.9% glycerol, or 9% soybean oil (SO) as a reference fat. In a 24-day balance study, apparent digestibility of total dietary fat averaged 93.1% in the SO, NFO and RFO groups, and 90.9% in the FO-FFA group. Randomization of fish oil had no effect on apparent digestibility of individual fatty acids. In rats fed FO-FFA, apparent absorption of saturated and monounsaturated fatty acids was lower when compared to the NFO and RFO groups. Feeding the FO-FFA diet tended to increase plasma triglyceride content. The hypocholesterolemic effect of polyunsaturated n−3 fatty acids was not influenced by the dietary source. Similar effects on fatty acid profiles of plasma and liver phospholipids were caused by the NFO, RFO and the FO-FFA diets. We conclude that once polyunsaturated n−3 fatty acids are absorbed, their effect on lipid metabolism is not determined by the dietary source.     

Influence of elaidate and erucate on heart mitochondria

Male, weanling rats were fed, for up to six weeks, corn oil (CO), rapeseed oil (RSO), partially hydrogenated fat (HF), or a mixture of partially hydrogenated fat and corn oil (HF+CO). The respiratory activity of their isolated heart mitochondria, their hormone-sensitive lipase activity, and the fatty acid compositions of the phospholipids of the mitochondria were determined. The results indicated that heart mitochondria isolated from rats which had been fed corn oil (CO) had a higher rate of oxygen uptake, showed higher respiratory control ratios, higher ADP/0 ratios and a higher rate of ATP synthesis than the heart mitochondria isolated from those fed rapeseed oil or hydrogenated fats. The oxygen uptake rates of the rat heart mitochondria isolated from each dietary group of rats was in order: oleyl carnitine ≫ erucyl carnitine > elaidyl carnitine. The decreased capacity to oxidize substrate by heart mitochondria which had been isolated from the hearts of rats fed rapeseed or hydrogenated soybean oil as compared with those fed corn oil as a sole source of dietary fat seemed related to the mitochondria lipid composition. The type of dietary fat fed had a pronounced influence on the mitochondrial fatty acid compositions of phosphatidylcholine, phosphatidylethanolamine, and cardiolipin. The lipase activity of the RSO-fed group did not show any increment with either epinephrine or supplemental ATP treatment. The substrate preference for lipase activity in myocardium was corn oil-triglycerides > trierucin > trielaidin > tripalmitin. However, cardiac lipid accumulation did not seem related to lipase activity in the myocardium. Taken from a thesis submitted by Chi Ming Lee Hsu in partial fulfillment of the Ph.D. degree in Food Science, University of Illinois at Urbana-Champaign.     

Fatty acid oxidation in relation to cholesterol biosynthesis in rats

Groups of male and female rats were fed diets containing (calorie basis) 2% corn oil (low-fat, LF), 42% corn oil (CO) or 2% corn oil plus 40% beef tallow (BT) for 2 weeks. Then rats of each sex and diet group were given an intraperitoneal injection of¹⁴C-acetate,- stearate- oleate or linoleate. Acetate incorporation into cholesterol and rate of oxidation of each fatty acid were determined. Specific activity of cholesterol was higher in females than males, higher with 40% lipid in the diet than with 2% corn oil and higher for CO than BT. Linoleate was oxidized more rapidly than oleate which exceeded stearate. An index of dietary lipid oxidation was computed based on fatty acid oxidation rate, per cent of each fatty acid in the diet and per cent of lipid calories in the diet. Serum cholesterol-¹⁴C was found to be proportional to dietary lipid oxidation index.     

Reduced plasma lecithin cholesterol acyl transferase activity in rats fed iron-deficient diets

An iron-deficient diet containing no fat (FF?Fe) or containing either 14% hydrogenated coconut oil (HCNO?Fe) or 14% corn oil (CO?Fe) was fed to separate groups of rats for 10 weeks. In the control group, the corresponding iron-supplemented diets were fed FF+Fe, HCNO+Fe, CO+Fe. When rats were fed iron-deficient diets, their plasma lecithin cholesterol acyl transferase (LCAT) activity was significantly reduced as compared to controls. Their plasma also contained relatively more cholesteryl esters (CE) than free cholesterol (CH). In rats fed FF+Fe and CO+Fe diets, plasma contained similar levels of CE and CH. In those fed HCNO+Fe diet, plasma had 40% less CE than CH. Red cell CH content was significantly greater in the CO?Fe group. Iron deficiency, as indicated by low blood hemoglobin (Hb) and hematocrit (Hct) values, was also observed only in this group. The triglyceride and phospholipid contents of plasma in rats fed iron-deficient diets were significantly lower than of those in the control groups. Thus, changes in LCAT activity and CE/CH ratio in plasma showed the effect of iron-deficient diet consumption even before the blood Hb and Hct levels were reduced.     

Effect of age and dietary fat (fish,corn and coconut oils) on tocopherol status of C57BL/6Nia mice

The effect of age and dietary fat type on tocopherol status was investigated using young and old C57BL/6Nia mice fed semipurified diets containing 5% (by weight) fish, corn or coconut oils and supplemented with 30, 100 or 500 ppm dl-α-tocopheryl acetate for 6 wk. Tocopherol levels in the diets, plasma, liver, kidney and lung were measured by high performance liquid chromatography following appropriate extractions. The results indicate that mice fed fish oil maintain lower plasma and tissue tocopherol concentrations than those fed corn and cononut oils (fish<corn oil<coconut oil). The difference was not due to a loss of tocopherol prior to consumption, but rather appeared to occur during the absorption process. Old mice had lower plasma and liver tocopherol concentrations than young mice. Old mice fed fish oil, however, maintained plasma tocopherol levels better than young mice fed fish oil, presumably due to their larger tocopherol pool. No age effect was detected on kidney and lung tocopherol levels. It is concluded that tocopherol status is affected by age and dietary fat type, especially fish oil.