Weeks Of Dietary Supplementation Research Articles

Effects of alpha-tocopherol and beta-carotene on hepatic lipid peroxidation and blood lipids in rats with dietary iron overload.

The ability of dietary antioxidants to reduce lipid peroxidation induced by iron overload was examined in weanling male Sprague-Dawley rats. Animals were fed ad libitum a modified AIN-76A diet (control) or control diet with 0.5% alpha-tocopherol acid succinate, 0.5% crystalline trans-beta-carotene, or 0.5% alpha-tocopherol acid succinate + 0.5% trans-beta-carotene for four weeks. In the following four-week period, the animals received the above diets with 10,000 micrograms Fe/g; a control group continued to receive 35 micrograms Fe/g, and a high-iron group received 10,000 micrograms Fe/g with no antioxidants. After four weeks of dietary supplementation with alpha-tocopherol. Beta-carotene or alpha-tocopherol + beta-carotene, liver concentrations of alpha-tocopherol and beta-carotene increased significantly (p < 0.001). Liver lipid peroxidation, measured by the lipid-conjugated diene assay, increased significantly from 0.012 mumol/mg of lipid in the controls to 0.021 mumol/mg of lipid in animals receiving the high-iron diet. However, lipid peroxidation was significantly reduced in all animals fed the antioxidants, with the group fed alpha-tocopherol + beta-carotene having a lower level than the high-iron group. Total serum cholesterol was elevated in animals fed a high-iron diet and in animals fed the high-iron diet with alpha-tocopherol. In contrast, total serum cholesterol levels in the two groups of animals receiving the diets containing high iron with beta-carotene alone or high iron with beta-carotene + alpha-tocopherol were significantly reduced to the level of the control group. High-density lipoprotein cholesterol also decreased to baseline in the animals receiving beta-carotene alone. Modulation of lipid peroxidation by alpha-tocopherol or beta-carotene may be an important mechanism for reducing oxidative stress.

Fish oil feeding modulates leukotriene production in murine lupus nephritis

Diets enriched with fish oil (FO) ameliorate kidney disease in the MRL- 1pr/1pr murine model of lupus nephritis. Although the mechanisms of this effect are not known, FO is rich in the polyunsaturated fatty acid eicosapentaenoic acid (EPA) which may have profound effects on eicosanoid metabolism. In MRL- 1pr/1pr mice, FO feeding reduces renal production of cyclooxygenase metabolites. However, EPA may also affect the metabolism of arachidonate by the 5-lipoxygenase (5-LO) pathway and enhanced production of 5-LO metabolites has been implicated in the pathogenesis of kidney disease in MRL- 1pr/1pr mice. We therefore investigated the effects of FO feeding on production of 5-LO metabolites in 20 week old MRL- 1pr/1pr mice. After 8 weeks of dietary supplementation with FO, both renal hemodynamic function and glomerular histology were improved compared to safflower oil (SO) controls. Amelioration of kidney disease was associated with alterations in the pattern of leukotriene production by macrophages and kidneys from FO fed mice. There was a significant decrease in the production of leukotriene B 4 (LTB 4) and tetraene peptidoleukotrienes by peritoneal macrophages isolated from mice given FO compared to control animals. Similarly, dietary supplementation with FO decreased renal production of LTB 4. Reduced production of tetraene leukotrienes was accompanied by a modest increase in the production of pentaene leukotrienes by macrophages from FO fed mice. We speculate that this modulation of leukotriene production by FO feeding may have beneficial effects on renal disease in autoimmune nephritis.

Asymmetric incorporation of dietary n-3 fatty acids into membrane aminophospholipids of human erythrocytes.

Dietary supplementation with different classes of polyunsaturate fatty acids is known to result in their incorporation into cell membranes, but the effects of this on eicosanoid formation and other cell functions frequently does not correspond to the degree of alteration in total membrane fatty acids. This phenomenon may be related to the compartmentalization of polyunsaturate fatty acids both within the organelles and within membranes. Aminophospholipids are asymmetrically distributed across the membrane bilayers of most human cells. These phospholipids are highly enriched in polyunsaturated fatty acids, and are known to have specific interactions with a number of membrane proteins. To determine whether dietary n-3 fatty acids are preferentially incorporated into membrane lipids in a particular spatial pattern, we have utilized the nonpermeant aminophospholipid probe, trinitrobenzenesulfonic acid, to study the transmembrane molecular species distribution of human erythrocyte ethanolamine phospholipids and phosphatidylserines before and at the end of 4 weeks of dietary supplementation with n-3 fatty acids. Selective incorporation of n-3 fatty acids occurred in the inner membrane leaflet ethanolamine phospholipids, particularly into the alkenyl-acyl species. The n-3 species in phosphatidylserines, particularly 18:0 and 22:6 n-3 (sn-1 and sn-2, respectively), replaced n-6 and n-9 species. These data may provide a basis for different cell responses to n-3 fatty acid enrichment, and for different degrees of diet-induced alteration in responses involving inner and outer membrane leaflet functions.

Muscle moment and power profiles in the medial and lateral gastrocnemius of the cat during jumping

Glucose transport in muscle is a function of the muscle metabolic state, as evidenced by the increase in glucose transport which occurs with conditions of altered aerobic metabolism such as hypoxia or contractile activity. The energy state of the muscle can be determined by the muscle phosphocreatine concentration. Dietary supplementation of creatine has been shown to increase both phosphocreatine (PCr) and creatine (TCr) levels in muscle, although not in the same proportion, so that the PCr/TCr ratio falls suggesting an altered energy state in the cell. The purpose of this study was to determine the effect of increased creatine content on glucose uptake in muscle. PCr and TCr were determined in plantaris muscles from rats following five weeks of dietary supplementation of creatine monohydrate (300 mg/kg/day). 3H-2-deoxyglucose uptake was measured in epitrochlearis muscles incubated in the presence or absence of a maximally stimulating dose of insulin. Despite a significant increase in creatine content in muscle, neither basal nor insulin-stimulated glucose uptake was altered in creatine supplemented rats. Since PCr levels were not increased with creatine supplementation, these results suggest that the actual concentration of PCr is a more important determinant of glucose uptake than the PCr/TCr ratio.

Influence of probucol on enhanced LDL oxidation after fish oil treatment of hypertriglyceridemic patients.

The susceptibility of low-density lipoprotein (LDL) to oxidation was studied in hypertriglyceridemic men (5 with type III and 5 with type IV) at baseline on a low-saturated-fat, low-cholesterol diet, after 6 weeks of dietary supplementation with fish oil (Promega, 12 g/d), and after 6 weeks of fish oil combined with probucol (500 mg BID). The relative content of n-3 polyunsaturated fatty acids in plasma and LDL was increased during the two treatment periods, and a low alpha-tocopherol to n-3 polyunsaturated fatty acids ratio was observed. Plasma thiobarbituric acid-reactive substances (TBARS) levels were unchanged after 6 weeks of fish oil, but the ratio of lipid peroxides to the reduced triglyceride (TG) levels (MDA:TG) was significantly higher (P < .01). Addition of probucol lowered both absolute levels of TBARS (P < .01) and the MDA to TG ratio (P < .001). The susceptibility of LDL to Cu(2+)-catalyzed oxidation was evaluated over a 5-hour time course by determining TBARS formation, free amino group levels, and changes in LDL electrophoretic mobility. TBARS levels that were higher in native LDL (1.019 < d < 1.050 g/mL) after 6 weeks of fish oil than at baseline (P < .01) were reduced 52.3 +/- 11.3% by the addition of probucol (P < .001). With fish oil alone, TBARS production after exposure of LDL to Cu2+ for 5 hours was increased 17.0 +/- 5.8% compared with corresponding baseline values (P < .001), whereas a 64.1 +/- 14.3% reduction from the previous period was observed with fish oil + probucol (P < .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of dietary fatty-acid supplementation on fatty-acid composition and deformability of young and old erythrocytes

The effects of cell age on erythrocyte phospholipid fatty-acid composition and deformability were examined in 20 healthy adults (11 male, 9 female) prior to and following 12 weeks of dietary supplementation with 3.5 g/day of safflower oil (high in n - 6 fatty acids) or fish oil (high in n - 3 fatty acids). In the absence of dietary supplementation, old erythrocytes demonstrated an increase in filtration time ( P < 0.001), an increase in membrane phospholipid total n - 6 fatty acids ( P < 0.01), and a decrease in total n - 3/total n - 6 ratio ( P < 0.01) compared to young erythrocytes. Both safflower and fish oil supplementation attenuated age-related differences in membrane phospholipid total n - 6 and total n - 3 fatty acids. Fish oil supplementation also increased the proportion of n - 3 fatty acids (P < 0.01) and the n - 3 n - 6 ratio (P < 0.05) in the phospholipids of both young and old erythrocytes, and eliminated age-related differences in erythrocyte filtration time by reducing the relative filtration time of the old erythrocytes.

Thermic effect of a meal. 3. Effect of dietary supplementation in chronically undernourished human subjects.

Five apparently healthy, chronically undernourished (UN) male volunteers aged between 18 and 30 years were studied before and after 12 weeks of dietary supplementation. The thermic effect of a meal (TEM) was measured over a period of 6 h using a ventilated-hood system. Results indicated a significant increase in body-weight after supplementation due to increases in body fat and fat-free mass (FFM) in the proportion of 69% and 31% respectively. The basal metabolic rates (BMR) measured post supplementation were significantly higher in absolute terms, with a trend towards higher values when adjusted for the changes in FFM. TEM responses measured after 12 weeks of supplementation were significantly lower when expressed either in absolute terms (presupplementation 227.0 kJ v. post supplementation 193.5 kJ), or as a percentage of the energy density of the meal (9.1% v. 7.7%). This lower TEM was reciprocal to the changes in the BMR (r -0.86). The post-meal total energy output (PMTEO) was, however, not significantly different after 12 weeks of dietary supplementation. The unchanged PMTEO would indicate an unaltered 'thermogenic capacity', following supplementation, in these chronically undernourished subjects. These results confirm our earlier conclusion that, in chronic undernutrition, the thermic response to a meal may not contribute to any energy saving.

Diets Enriched With N‐3 Fatty Acids Ameliorate Lactic Acidosis by Improving Endotoxin‐Induced Tissue Hypoperfusion in Guinea Pigs J.J. POMPOSELLI, E.A. FLORES, G.L. BLACKBURN, S.H. ZEISEL, B.R. BISTRIAN Ann Surg 213:166–176, 1991

The authors compared the effects of 6 weeks of dietary supplementation with either N‐3 fatty acids (fish oil) or N‐6 fatty acids (safflower oil) on the acute physiologic response to continuous endotoxin infusion in guinea pigs. Substantial evidence has accumulated to suggest that arachidonic acid metabolites may act as a common efferent signal in the pathogenesis of septic shock. Studies attempting to elucidate the physiologic effects of diets rich in N‐3 fatty acids have centered on the altered formation and metabolism of prostanoids. Eicosapentaenoic acid (EPA) has been shown to be the metabolically active fatty acid in fish oil because of its structural similarity to the prostaglandin precursor, arachidonic acid (AA). Controlled dietary intake of selected fish oils rich in EPA and N‐3 fatty acids have been shown to down‐regulate eicosanoid metabolism leading to a more vasodilatory platelet and neutrophil antiaggregatory state compared with diets enriched with N‐6 fatty acids. In previous studies, the authors have shown that dietary pretreatment with N‐3 fatty acids attenuated the febrile response, reduced thromboxane formation to exogenous IL‐1 administration, and improved survival after endotoxin challenge in guinea pigs. In the present study, it is hypothesized that diets enriched with N‐3 fatty acids may alter the physiologic response to endotoxin, possibly by altering membrane phospholipids.Three different experimental protocols were carried out after a 6‐week feeding period in which animals received a standard diet containing either menhaden fish oil (N‐3 fatty acids) or safflower oil (N‐6 fatty acids). In the first experiment, animals were infused with endotoxin for 7 hours and blood pH, paCO2, bicarbonate, blood pressure, plasma lactate, serum phospholipid fatty acid profile, and histology (lung, liver, and kidney) were examined. In the second experiment, cardiac output and blood flow distribution during endotoxemia were determined. In the third experiment, the effect of either indomethacin or a specific thromboxane A2 receptor blocker (BM 13505) on the response to endotoxemia was examined. An additional subset of animals were infused with dichloroacetic acid (DCA), which prevents inhibition of the pyruvate dehydrogenase enzyme complex by endotoxin.The mortality rate of animals infused with endotoxin alone was 20% in the safflower oil‐fed group and 10% in the menhaden oil‐fed group (not a statistically significant difference). No deaths were observed in animals pretreated with either indomethacin or BM 13505 regardless of diet. Safflower oil‐fed animals developed an initial respiratory alkalosis followed by metabolic acidosis in response to endotoxin infusion, whereas fish‐oil fed animals developed a mild respiratory alkalosis and no metabolic acidosis. Pre‐treatment with indomethacin or BM 13505 had similar effects to N‐3 fatty acid feeding in ameliorating the development of metabolic acidosis in safflower oil‐fed animals, suggesting that prostaglandins and especially thromboxane, may be responsible for the development of some of the sequelae of endotoxemia. Safflower oil‐fed animals had a sevenfold increase in lactate production compared with controls and a threefold increase compared with fish oil‐fed animals. Infusion of indomethacin, significantly reduced the amount of lactate formed in safflower oil‐fed animals given endotoxin, but had no additive effect in fish oil‐fed animals. Administration of BM 13505 was only partially effective in reducing lactate levels, which remained significantly above control levels. The infusion of DCA failed to lower blood lactate levels in both groups given endotoxin. Safflower oil‐fed animals developed a diffuse interstitial pneumonia with increased neutrophils and intravascular congestion. Fish oil‐fed animals infused with endotoxin demonstrated intravascular congestion in their lungs without infiltrates. Examination of other tissues did not demonstrate any abnormalities in all groups, with the exception of the liver, which showed mild fatty infiltration in both dietary groups. Lung function was not severely compromised during the initial period of endotoxemia in either group. Endotoxin infusion caused a significant decrease in percent perfusion of both skin and muscle, regardless of dietary intake. However, in muscle, decreased perfusion was partly prevented by pre‐treatment with N‐3 fatty acids.

Effects of dietary fish oil supplementation on platelet aggregability and platelet membrane fluidity in normolipemic subjects with and without high plasma Lp(a) concentrations

The purpose of this study was to compare the relative effect of n − 3 fatty acids on plasma lipids and platelet function in normolipemic subjects n − 8 with plasma Lp(a) levels > 30 mg/dl and normolipemic subjects n − 7 without detectable plasma Lp(a) concentrations. Six weeks of dietary supplementation (3.8 g EPA and 2.9 g DHA/d) significantly reduced ( P < 0.005) plasma TGs in both groups whereas no changes of plasma TC, LDL-C, HDL-C, and Lp(a), respectively, were found. Collagen- or thrombin-stimulated platelet aggregation and collagen- or thrombin-induced TXB 2 generation from platelets decreased by approx. 45% in Lp(a)-negative and Lp(a)-positive platelet donors after a 6 week dietary intake. Four more weeks without n − 3 supplementation restored the pretreatment values of TGs, platelet aggregability and TXB 2 release. The biophysical properties of platelets from normolipemics with and without high plasma Lp(a) concentrations revealed a similar structural order of platelets at 37°C using DPH, TMA-DPH, or 6-AS as fluorescent probes. Also similar temperature-dependent changes in platelet fluidity from 37°C to 17°C were observed in platelet preparations from Lp(a)-positive and Lp(a)-negative subjects. However, no subtle changes in the structural order of platelets due to nutrient intakes were found in all subjects ( n = 15, 19–28 yrs) using fluorescence polarization technique. The present data suggest a similar in vitro platelet behaviour from normolipemic subjects with and without high plasma levels of Lp(a) (which is considered a risk for premature atherosclerosis) in contrast to platelet aggregability and platelet fluidity in certain hyperlipidemic stages.

Synthesis of prostaglandins and thromboxane B2 by cholesterol-fed rabbits.

Alterations in the synthesis of thromboxane A2 (TxA2) and prostacyclin have been implicated in the development of atherosclerosis. We measured the amounts of the degradation products of these substances, TxB2 and 6-oxo-prostaglandin F1 alpha (6-oxo-PGF1 alpha), respectively, as well as PGE2, that were synthesized by slices and the luminal surfaces of aortas from rabbits fed either a control diet or a diet supplemented with cholesterol and peanut oil. For these studies, we developed conditions that were designed to minimize the autoinactivation of cyclooxygenase during removal and preparation of the tissue. Pretreatment of aortas with a medium containing ibuprofen and EDTA resulted in an approximately twofold increase in 6-oxo-PGF1 alpha production upon subsequent incubation. Despite the increased lipid peroxidation associated with atherosclerotic lesions, we observed no changes in either aortic 6-oxo-PGF1 alpha production or in the levels of its major urinary metabolite, 2,3-dinor-6-oxo-PGF1 alpha, after as long as 15 weeks of dietary supplementation with cholesterol and peanut oil. Similarly, synthesis of PGE2 by aortic slices and the aortic lumen was the same in cholesterol-fed and control rabbits. In contrast to aortic 6-oxo-PGF1 alpha and PGE2 synthesis, there was a dramatic 10-fold increase in TxB2 released from slices of thoracic aorta after 15 weeks on the atherogenic diet. This was much greater than the approximately twofold increase in the synthesis of TxB2 by the luminal surface of the thoracic aorta, suggesting that the primary site of TxB2 synthesis in the aorta is in the inner part of the blood vessel.(ABSTRACT TRUNCATED AT 250 WORDS)

Fish oil reduces ethanol‐induced damage of the duodenal mucosa in humans

Eight healthy volunteers were studied before and after 3 weeks of dietary supplementation with fish oil (10.5 g day-1, 18% (1.9 g) eicosapentaenoic acid). Duodenal mucosal lesions were induced by instillation of 40 ml ethanol (40%). Mean endoscopic lesion score was lower after fish oil treatment (1.62 +/- 0.32; mean +/- SEM) than before (3.25 +/- 0.31; P less than 0.01). Histologic lesion score fell from 22.75 +/- 1.98 before treatment to 13.50 +/- 1.51 after fish oil (P less than 0.01). Basal and pentagastrin-stimulated gastric acid output remained unaffected. Release of prostaglandin E2, 6-keto-prostaglandin F1 alpha, and thromboxane B2 from biopsy specimens of the duodenal mucosa in vitro was not significantly altered after fish oil ingestion. In the same in vitro system calcium ionophore A23187-induced release of total leukotriene C (LTC) increased from 10.6 +/- 1.5 ng g-1 mucosa 20 min before treatment to 30.4 +/- 3.2 ng after fish oil. High pressure liquid chromatography analysis showed that this increase was partly due to formation of LTC5 as after fish oil 28% of total LTC were identified as LTC5 whereas 72% were LTC4. We conclude that in humans fish oil reduces ethanol-induced damage of the duodenal mucosa without inhibiting gastric acid secretion or stimulating prostaglandin formation. It remains to be clarified if the changes in leukotriene formation are relevant for the mucosaprotective fish oil effect.

The effects of N-3 polyunsaturated fatty acids on the generation of platelet-activating factor-acether by human monocytes.

Human leukocytes generate platelet-activating factor (PAF-acether), a lipid mediator of inflammation, from membrane alkyl phospholipids through the release of arachidonic acid or other fatty acids at the 2-position and subsequent acetylation. Because it was previously demonstrated that fish oil fatty acids suppress human leukocyte arachidonic acid release and metabolism, separate experiments were conducted to investigate the effects of dietary fish oil supplementation and in vitro incubation with fish oil fatty acids on calcium ionophore-stimulated PAF-acether generation in human monocytes. In subjects on their regular diets, a 4-hr incubation of monocyte monolayers with an optimally effective concentration of arachidonic acid of 1 micrograms/ml resulted in a 64% increase of calcium ionophore-induced net PAF-acether generation from 7.75 +/- 0.78 ng/10(6) cells for untreated monolayers to 12.70 +/- 1.21 ng/10(6) cells (mean +/- SEM). Treatment of monolayers with eicosapentaenoic acid (EPA) at the optimal concentration of 1 micrograms/ml decreased net PAF-acether generation by 28%. However, treatment of monocyte monolayers with docosahexaenoic acid did not appreciably affect net PAF-acether generation. The changes in PAF-acether release with each fatty acid added in vitro paralleled those in total PAF-acether generation; the percentage PAF-acether release remained unaffected. Three weeks of dietary supplementation with 18 g MaxEPA daily, providing 3.2 g EPA did not affect the PAF-acether generation of calcium ionophore-stimulated human monocyte monolayers. However, 6 weeks of dietary supplementation resulted in a 47% decrease of net total PAF-acether generation and a concomitant 59% decline in net PAF-acether release; the percentage release of PAF-acether was not affected. Thus, whether added to the diet or introduced in vitro, fish oil-derived fatty acids suppress PAF-acether generation by human monocyte monolayers.