Phenobarbital increases rat hepatic prostaglandin F2 alpha, glutathione S-transferase activity and oxidative stress

Eight-week-old female F344/N rats were fed 3.0 or 6.0% of calories (kcal%) as linoleate with or without 0.05% phenobarbital (PB) for 35 days. PB treatment increased glutathione S-transferase (GST) activity by 80% and prostaglandin (PG) F2 alpha levels 4-fold (p less than 0.05). PB decreased hepatic alpha-tocopherol significantly. Hepatic linoleate was decreased by PB in rats fed 6 kcal% but not 3 kcal% linoleate. Increased dietary linoleate had no significant effect on hepatic PGF2 alpha or alpha-tocopherol levels or GST activity. This study suggests that PB hepatotoxicity and tumor-promoting ability may be mediated, at least in part, by PGF2 alpha. PB's effect on PGF2 alpha could be a result of both GST-mediated prostaglandin synthesis and oxidative stress. The removal of significant amounts of hepatic alpha-tocopherol during oxidative stress induced by PB might diminish endogenous inhibition of hepatic PG synthesis by a-tocopherol.     

Influence of dietary vitamin E on the intermembrane transfer of alpha-tocopherol as mediated by an alpha-tocopherol binding protein

The effect of dietary vitamin E on the intermembrane transfer of (3R)-alpha-tocopherol, a spontaneous process accelerated in the presence of an alpha-tocopherol binding protein (alpha TBP), was examined. The transfer activity of this cytosolic liver protein was assayed via in vitro transfer of (3R)-alpha-[3H]tocopherol (alpha[3H]T) from egg lecithin liposomes to human erythrocyte ghosts (EG). Male Fisher 344 rats (1 and 20 months old) were fed diets containing 0, 30, and 500 mg/kg vitamin E (dl-alpha-tocopheryl acetate) for 15 weeks. Liver cytosol fractions were assayed for alpha[3H]T transfer activity (alpha TTA). Among young rats, those fed vitamin E-deficient diets had the highest alpha TTA, 5.02 +/- 3.10 pmole alpha[3H]T/min (mean +/- SD), which was different (P less than 0.05) from the spontaneous transfer rate of 2.10 pmole/min. Neither young rats fed 30 and 500 mg/kg vitamin E diets nor any of the aged rats showed alpha TTA which differed significantly from the spontaneous transfer rate. To examine the relationship between hepatic alpha-tocopherol levels and alpha TTA, alpha-tocopherol concentration per gram of wet liver was assayed by HPLC. A steep positive slope (6.39 +/- 1.46 pmole min-1 nmole g-1) and strong correlation (r = 0.873) between hepatic alpha-tocopherol and alpha TTA were observed (P less than 0.005) among young vitamin E-deficient rats. The data indicates that alpha TTA varies directly with hepatic alpha-tocopherol concentration when total liver vitamin E stores are very low. Thus, alpha TBP-mediated transfer of alpha-tocopherol may be manifest only when vitamin E status is compromised.     

Sex and dietary fat modulate hepatic prostaglandin F2 alpha in F344/N rats.

The study was designed to determine whether sex and fat calories altered hepatic prostaglandin (PG) F2 alpha status; a factor which may reflect susceptibility to cancer development. For 4 weeks, groups of 8 male and 8 female F344/N rats were fed diets with 9% of energy (en%) from linoleate and 15.5, 20, 30 or 40 en% fat. Females had greater hepatic stearate, arachidonate and PGF2 alpha whereas males had greater hepatic myristate, palmitate and oleate. Females also had greater plasma stearate levels. Greater hepatic arachidonate may have stimulated PG production in females. Hepatic oleate increased and hepatic palmitate decreased with increasing en% fat (p < 0.05). Hepatic stearate was greater and hepatic linoleate less when 40 en% fat was fed compared with other levels of dietary fat (p < 0.05). Plasma oleate was greater at 30 or 40 en% fat than at lower levels of fat, whereas plasma linoleate was less at 40 en% than at 15.5% en% fat. The ability of a 30 en% fat diet, containing equal proportions of linoleate and oleate, to suppress hepatic PG production may be related to the effects of dietary fat content and composition on plasma fatty acid profiles. Because suppressed PG production has been linked with suppression of cancer development, dietary recommendations to consume 30 en% fat with a P:M ratio of 1:1 may be cancer-protective.     

Dietary zinc restriction in rats alters antioxidant status and increases plasma F2 isoprostanes

Approximately 12% of Americans do not consume the estimated average requirement for zinc and could be at risk for zinc deficiency. Since zinc has proposed antioxidant function, inadequate zinc consumption may lead to an enhanced susceptibility to oxidative stress through several mechanisms, including altered antioxidant defenses. In this study, we hypothesized that dietary zinc restriction would result in lower antioxidant status and increased oxidative damage. We fed weanling Sprague-Dawley rats (n=12 per group) a zinc-adequate (50 mg/kg of zinc) diet, a zinc-deficient (<0.05 mg/kg of zinc) diet or a pair-fed diet for 3 weeks and then assessed their antioxidant status and oxidative stress parameters. Rats were zinc deficient as indicated by a significant (P<.05) reduction in body weight (49%) and 19% lower (P<.05) hepatic zinc (20.6+/-2.1 mg/kg) as compared with zinc-adequate rats (24.6+/-2.2 mg/kg). Zinc deficiency resulted in elevated (P<.05) plasma F(2) isoprostanes. Zinc deficiency-mediated oxidative stress was accompanied by a 20% decrease (P<.05) in the ferritin-reducing ability of plasma assay and a 50% reduction in plasma uric acid (P<.05). No significant change in plasma ascorbic acid or in plasma alpha-tocopherol and gamma-tocopherol was observed. However, hepatic alpha-tocopherol and gamma-tocopherol concentrations were decreased by 38% and 27% (P<.05), respectively, as compared with those in zinc-adequate rats. Hepatic alpha-tocopherol transfer protein levels were unaltered (P>.05) by zinc deficiency, but cytochrome P450 (CYP) 4F2 protein levels were elevated (P<.05) as compared with those in zinc-adequate rats. Collectively, zinc deficiency increased oxidative stress, which may be partially explained by increased CYP activity and reductions in hepatic alpha-tocopherol and gamma-tocopherol and in plasma uric acid.     

Sesamin and alpha-tocopherol synergistically suppress lipid-peroxide in rats fed a high docosahexaenoic acid diet

Docosahexaenoic acid (DHA) is an essential nutrient for human health, but has extremely high oxidative susceptibility. We examined the suppressing effect of sesamin, a sesame seed lignan, on lipidperoxides in rats fed a low alpha-tocopherol and high DHA containing diet. Groups of rats were fed four experimental diets: low alpha-tocopherol (10 mg/kg diet) control diet, low alpha-tocopherol + 0.2% sesamin diet, low alpha-tocopherol + 0.5% DHA diet and low alpha-tocopherol + 0.5% DHA + 0.2% sesamin diet. TBARS concentrations in plasma and liver were significantly increased by DHA, but were completely suppressed by sesamin. Alpha-tocopherol concentrations in plasma and liver decreased by addition of DHA, but with sesamin recovered to the control level. The addition of DHA into the diets caused remarkable increases of DHA concentrations in plasma and liver lipids. Sesamin caused a significant increase of DHA concentrations in the triacylglycerol of plasma.     

Regulatory mechanisms to control tissue alpha-tocopherol

To test the hypothesis that hepatic regulation of alpha-tocopherol metabolism would be sufficient to prevent overaccumulation of alpha-tocopherol in extrahepatic tissues and that administration of high doses of alpha-tocopherol would up-regulate extrahepatic xenobiotic pathways, rats received daily subcutaneous injections of either vehicle or 0.5, 1, 2, or 10 mg alpha-tocopherol/100 g body wt for 9 days. Liver alpha-tocopherol increased 15-fold in rats given 10 mg alpha-tocopherol/100 g body wt (mg/100 g) compared with controls. Hepatic alpha-tocopherol metabolites increased with increasing alpha-tocopherol doses, reaching 40-fold in rats given the highest dose. In rats injected with 10 mg/100 g, lung and duodenum alpha-tocopherol concentrations increased 3-fold, whereas alpha-tocopherol concentrations of other extrahepatic tissues increased 2-fold or less. With the exception of muscle, daily administration of less than 2 mg/100 g failed to increase alpha-tocopherol concentrations in extrahepatic tissues. Lung cytochrome P450 3A and 1A levels were unchanged by administration of alpha-tocopherol at any dose. In contrast, lung P-glycoprotein (MDR1) levels increased dose dependently and expression of this xenobiotic transport protein was correlated with lung alpha-tocopherol concentrations (R(2)=0.88, p<0.05). Increased lung MDR1 may provide protection from exposure to environmental toxins by increasing alveolar space alpha-tocopherol.     

Green tea flavonoids inhibit the LDL oxidation in osteogenic disordered rats fed a marginal ascorbic acid in diet

Osteogenic Disorder Shionogi (ODS) rats can not synthesize ascorbic acid (AA). We have examined the capacity of green tea flavonoids (GTF) to modify low-density lipoprotein (LDL) oxidation in ODS rats with dietary AA restriction. In the first experiment, ODS rats were fed diets containing 300 (AA300 diet) or 0 (AA0 diet) mg AA/kg diets for 20 d. In comparison with the AA300 diet, the AA0 diet significantly decreased the concentrations of plasma AA and alpha-tocopherol in LDL and significantly shortened the lag time of LDL oxidation in vitro. In the second experiment, ODS rats were fed one of the following three diets: the AA300 diet, the diet containing 25 mg AA (AA25, marginal AA)/kg diet (AA25 diet), or the diet containing 25 mg AA + 8 g GTF/kg diet (AA25 + GTF diet) for 20 d. Plasma AA concentration were significantly lower in rats fed AA25 compared with AA300 but not in those fed AA25 + GTF. LDL oxidation lag time was significantly longer in rats fed AA25 + GTF compared with the other two groups. Lag time for LDL oxidation was significantly and positively correlated with LDL alpha-tocopherol (r = 0.6885, P = 0.0191). These results suggest that dietary flavonoids suppress the LDL oxidation through the sparing effect on LDL alpha-tocopherol and/or plasma AA when AA intake is marginal in the ODS rats.     

Dietary selenium supplementation prolongs pentobarbital induced hypnosis

The present studies characterized the influence of dietary selenium (Na2SeO3) on the duration of pentobarbital (PB) induced hypnosis (sleep) in the rat. Rats were fed semipurified diets varying from 0.01 to 2.0 mg Se/kg for up to 4 weeks. Consumption of diets containing 1.0 and 2.0 mg Se/kg significantly prolonged PB induced hypnosis. Hepatic selenium, but not hepatic glutathione peroxidase activity, correlated with the length of PB induced hypnosis. The prolongation of hypnosis caused by diets containing 1.0 mg Se/kg was substantially reduced or eliminated by repeated exposure to PB. Although single exposure to increasing quantities of PB (60-100 mg/kg body weight) led to a progressive increase in sleep duration, the proportional increase caused by supplemental selenium (2.0 vs 0.1 microg Se/g) remained relatively constant (approximately 25%). Increasing maturity was inversely related to the duration of PB induced hypnosis, regardless of dietary selenium provided. Consumption of the 2.0 mg Se/kg diet prolonged PB induced hypnosis to a greater degree in immature than in mature rats (P < 0.05). Consumption of the selenium enriched diet (2 microg Se/g) resulted in an increase in cytochrome 2B, but had no effect on cytochrome 1A compared to controls (0.1 microg Se/g). Pretreatment of rats with P450 enzymes activators (i.e., PB, Aroclor 1254, or 3-methylcholanthrene) shortened the duration of PB induced sleep and masked the effects of dietary selenium. The current studies document that dietary selenium can influence the response to pentobarbital induced hypnosis and likely relates to changes in drug detoxification enzymes.     

Antioxidant activity and metabolite profile of quercetin in vitamin-E-depleted rats

Dietary antioxidants interact in a dynamic fashion, including recycling and sparing one another, to decrease oxidative stress. Limited information is available regarding the interrelationships in vivo between quercetin and vitamin E. We investigated the antioxidant activity and metabolism of quercetin (Q) in 65 F-344 rats (n=13 per group) randomly assigned to the following vitamin E (VE)-replete and -deficient diets: (a) VE replete (30 mg alpha-tocopherol acetate/kg diet) control ad libitum (C-AL), (b) VE replete pair fed (C-PF), (c) VE replete+5.0 g Q/kg diet (R-VE+5Q), (d) VE deplete (<1 mg/kg total tocopherols)+5.0 g Q/kg diet (D-VE+5Q) and (e) D-VE. After 12 weeks, blood and tissue were collected for measurement of plasma vitamin E, quercetin and its metabolites, serum pyruvate kinase (PK), plasma protein carbonyls, malondialdehyde (MDA) and oxygen radical absorbance capacity. D-VE diets decreased serum alpha-tocopherol and increased PK activity in a time-dependent manner. The D-VE diet increased plasma protein carbonyls but did not affect MDA. Dietary quercetin supplementation increased quercetin and its metabolites in plasma and liver but did not affect D-VE-induced changes in plasma alpha-tocopherol, PK or protein carbonyls. Plasma isorhamnetin and its disposition in muscle were enhanced by the D-VE diet, as compared to the R-VE diet. Conversely, tamarixetin disposition in muscle was decreased by the D-VE diet. Thus, quercetin did not slow vitamin E decline in vivo; neither did it provide antioxidant activity in vitamin-E-depleted rats. However, vitamin E status appears to enhance the distribution of isorhamnetin into the circulation and its disposition in muscle.     

Reduced hepatic alpha-tocopherol content after long-term administration of ethanol to rats

We have studied the effects of long-term administration of ethanol on the distribution and pharmacokinetics of alpha-tocopherol. In rats fed ethanol (35% of total energy) for 5-6 weeks concentration of alpha-tocopherol in whole liver was reduced by 25% as compared to the pair-fed controls (P less than 0.003). This reduction was significant in the parenchymal cells (28%, P less than 0.004), whereas no significant difference was observed for the nonparenchymal cells. Mitochondrial alpha-tocopherol content was reduced by 55% in the ethanol-treated rats as compared to the controls (P less than 0.002), whereas no significant difference was observed in microsomes, light mitochondria or cytosol. The serum levels of alpha-tocopherol showed no significant difference between the groups. When in vivo labeled chylomicron alpha-[3H]tocopherol was injected intravenously to anesthetized rats, we found a significant increase in serum half-life of alpha-tocopherol in the ethanol-treated group as compared to the controls (P less than 0.025). Hepatic alpha-[3H]tocopherol content was similar in the two groups 24 h after injection.     

L-carnitine increases liver alpha-tocopherol and lowers liver and plasma triglycerides in aging ovariectomized rats

The objective of this study was to determine whether dietary L-carnitine can influence the status of alpha-tocopherol, retinol and selected lipid parameters in aging ovariectomized rats, an animal model for the menopausal state. Fourteen Fisher-344 female rats 18 months old were acclimated for 4 weeks and ovarectomized. Seven rats per treatment were assigned to either a control group fed ad libitum AIN-93M diet or a carnitine group fed the same diet supplemented with L-carnitine. After an 8-week feeding period, blood and selected tissues were taken for analyses. No differences were noted in food intake, body weight, or organ weights due to L-carnitine. Dietary carnitine significantly increased liver alpha-tocopherol and tended to increase plasma alpha-tocopherol (P<.09). No changes in alpha-tocopherol were observed in other tissues including the brain, lungs and retroperitoneal fat. Retinol levels in plasma and tissues were not affected by supplemental L-carnitine. Significant decreases in liver and plasma triglyceride (TG) levels were noted, suggesting increased utilization of fatty acids. No differences were observed in the fatty acid profile of tissues. The results provide evidence that dietary supplementation of L-carnitine enhances the alpha-tocopherol status and improves the utilization of fat leading to lowering of the liver and plasma levels of TG in aging ovariectomized rats. Whether supplemental L-carnitine may be of benefit to postmenopausal women in lowering plasma TG and improving the antioxidant status remains to be studied.     

Vitamin E supplementation in the mitigation of carbon tetrachloride induced oxidative stress in rats

Oxidative stress is implicated in the pathophysiology of a number of chronic diseases including atherosclerosis, diabetes, cataracts and accelerated aging. The aim of this study was to elucidate the protective role of vitamin E supplementation when oxidative stress is induced by CCl4 administration, using the rat as a model. Rats were fed diets for four weeks either with or without dl-alpha-tocopherol acetate supplementation. Half of the rats (n = 9) from each of the diet groups were then challenged with CCl4 at the completion of the four week diet period. Plasma levels of 8-iso-PGF(2alpha), antioxidant micronutrients and antioxidant enzyme activities were measured to examine changes in oxidative stress subsequent to the supplementation of dl-alpha-tocopherol in the diet. Plasma alpha-tocopherol (vitamin E) concentrations were higher for the groups supplemented with dl-alpha-tocopherol acetate, however the supplemented diet group that was subsequently challenged with CCl4 had significantly lower (p <0.001) plasma alpha-tocopherol concentration than the dl-alpha-tocopherol acetate diet group that was not challenged with CCl4. Total plasma 8-iso-PGF(2alpha) concentration was elevated in diet groups challenged with CCl4, however, the concentration was significantly lower (p <0.001) when the diet was supplemented with dl-alpha-tocopherol acetate. The antioxidant enzymes were not influenced by either dietary alpha-tocopherol manipulation or by the inducement of oxidative stress with CCl4. Plasma concentrations of trans-retinol (vitamin A) were reduced by CCl4 administration in both the dl-alpha-tocopherol acetate supplemented and unsupplemented diet groups. The results of this study indicate that dl-alpha-tocopherol acetate supplementation was protective of lipid peroxidation when oxidative stress is induced by a pro-oxidant challenge such as CCl4.     

Alpha-tocopherol modulates Cyp3a expression, increases gamma-CEHC production, and limits tissue gamma-tocopherol accumulation in mice fed high gamma-tocopherol diets

Although all forms of vitamin E are absorbed, the liver preferentially secretes alpha-, but not gamma-tocopherol, into plasma. Liver alpha-tocopherol secretion is under the control of the alpha-tocopherol transfer protein (TTP). Therefore, to assess gamma-tocopherol bioactivities Ttpa-/-, +/- and +/+ mice were fed for 5 weeks diets containing gamma-tocopherol 550 (gamma-T550), gamma-tocopherol 60 (gamma-T60) mg/kg that also contained trace amounts of alpha-tocopherol, a vitamin E-deficient diet, or a control diet. Plasma and tissues from mice fed gamma-T550 diets were found to contain similar gamma- and alpha-tocopherol concentrations despite the high dietary gamma-tocopherol content; nervous tissues contained almost no gamma-tocopherol. Liver vitamin E metabolites (carboxyethyl hydroxychromans, CEHCs) were also measured. In mice with widely ranging liver alpha- (from 0.7 to 16 nmol/g) and gamma-tocopherol concentrations (0 to 13 nmol/g), hepatic alpha-CEHC was undetectable, but gamma-CEHC concentrations (0.1 to 0.8 nmol/g) were correlated with both alpha- and gamma-tocopherol concentrations (P < 0.004). Hepatic cytochrome P450s (CYPs) involved in vitamin E metabolism, Cyp4f and Cyp3a, were also measured. There were no variations in Cyp4f protein expression as related to diet or mouse genotype. However, Cyp3a was correlated (P < 0.0001) with liver alpha-, but not gamma-tocopherol concentrations. These data support the hypothesis that alpha-tocopherol modulates xenobiotic metabolism by increasing Cyp3a expression, gamma-CEHC formation, and the excretion of both gamma-tocopherol and gamma-CEHC.     

Content of liver and brain ubiquinol-9 and ubiquinol-10 after chronic ethanol intake in rats subjected to two levels of dietary alpha-tocopherol

To assess the effect of chronic ethanol ingestion in the content of the reduced forms of coenzymes Q9 (ubiquinol-9) and Q10 (ubiquinol-10) as a factor contributing to oxidative stress in liver and brain, male Wistar rats were fed ad libitum a basal diet containing either 10 or 2.5 mg alpha-tocopherol/100 g diet (controls), or the same basal diet plus a 32% ethanol-25% sucrose solution. After three months treatment, ethanol chronically-treated rats showed identical growth rates to the isocalorically pair-fed controls, irrespectively of alpha-tocopherol dietary level. Lowering dietary alpha-tocopherol led to a decreased content of this vitamin in the liver and brain of control rats, without changes in that of ubiquinol-9, and increased levels of hepatic ubiquinol-10 and total glutathione (tGSH), accompanied by a decrease in brain tGSH. At the two levels of dietary alpha-tocopherol, ethanol treatment significantly decreased the content of hepatic alpha-tocopherol and ubiquinols 9 and 10. This effect was significantly greater at 10 mg alpha-tocopherol/100 g diet than at 2.5, whereas those of tGSH were significantly elevated by 43% and 9%, respectively. Chronic ethanol intake did not alter the content of brain alpha-tocopherol and tGSH, whereas those of ubiquinol-9 were significantly lowered by 20% and 14% in rats subjected to 10 and 2.5 mg alpha-tocopherol/100 g diet, respectively. It is concluded that chronic ethanol intake at two levels of dietary alpha-tocopherol induces a depletion of hepatic alpha-tocopherol and ubiquinols 9 and 10, thus contributing to ethanol-induced oxidative stress in the liver tissue. This effect of ethanol is dependent upon the dietary level of alpha-tocopherol, involves a compensatory enhancement in hepatic tGSH availability, and is not observed in the brain tissue, probably due to its limited capacity for ethanol biotransformation and glutathione synthesis.     

Antioxidant alpha-tocopherol ameliorates glycemic control of GK rats, a model of type 2 diabetes

We have shown recently that oxidative stress by chronic hyperglycemia damages the pancreatic beta-cells of GK rats, a model of non-obese type 2 diabetes, which may worsen diabetic condition and suggested the administration of antioxidants as a supportive therapy. To determine if natural antioxidant alpha-tocopherol (vitamin E) has beneficial effects on the glycemic control of type 2 diabetes, GK rats were fed a diet containing 0, 20 or 500 mg/kg diet alpha-tocopherol. Intraperitoneal glucose tolerance test revealed a significant increment of insulin secretion at 30 min and a significant decrement of blood glucose levels at 30 and 120 min after glucose loading in the GK rats fed with high alpha-tocopherol diet. The levels of glycated hemoglobin A1c, an indicator of glycemic control, were also reduced. Vitamin E supplementation clearly ameliorated diabetic control of GK rats, suggesting the importance of not only dietary supplementation of natural antioxidants but also other antioxidative intervention as a supportive therapy of type 2 diabetic patients.     

Modulation of Cyp3a11 mRNA expression by alpha-tocopherol but not gamma-tocotrienol in mice

Metabolism of vitamin E is initiated by cytochrome P450 (CYP) enzymes usually involved in the metabolism of xenobiotics. Like other CYP substrates, vitamin E induced a reporter gene under the control of the pregnane X receptor (PXR) which regulates the expression of CYPs including CYP3A4. gamma-Tocotrienol, the most effective PXR activator, also induced endogenous CYP3A4 mRNA in HepG2 cells. Since these findings imply an interference of vitamin E with drug metabolism it was deemed necessary to investigate their in vivo relevance. Therefore, mice were grown for 3 months with alpha-tocopherol-deficient, -adequate, and -supranutritional diet, i.e. 2, 20 and 200 mg RRR-alpha-tocopheryl acetate/kg diet, respectively. Half of them received 250 microg gamma-tocotrienol/day for the last 7 days. After 3 months, hepatic levels of Cyp3a11 mRNA, the murine homolog to human CYP3A4, were about 2.5-fold higher in the 20 and 200 mg alpha-tocopherol groups than in the 2 mg group. After feeding 200 mg alpha-tocopherol for 9 months, Cyp3a11 mRNA was 1.7-fold higher than after 3 months. In contrast, gamma-tocotrienol did not induce Cyp3a11 mRNA. This could be explained by its high metabolism as demonstrated by the 20- to 25-fold increase in the urinary excretion of gamma-CEHC, the final metabolite of gamma-tocotrienol degradation. In conclusion, alpha-tocopherol maintains an adequate level of xenobiotic-metabolizing enzymes. If fed in supranutritional dosages, especially for longer times, alpha-tocopherol induces Cyp3a11 to levels which might interfere with drug metabolism.     

Fenofibrate prevents orotic acid--induced hepatic steatosis in rats

The experiments performed in this report were designed to investigate the mechanisms involved in the metabolic alterations associated with orotic acid-induced hepatic steatosis and the effect of fenofibrate, a stimulant of peroxisome proliferators-activated receptor alpha (PPARalpha), on these alterations. Male Wistar rats were divided into three experimental groups: 1) fed a balanced diet (C); 2) fed a balanced diet supplemented with 1% orotic acid (OA); 3) fed OA diet containing 100 mg.kg(-1) bw.day(-1) fenofibrate (OA+F), for 9 days. Administration of OA to rats induced significant increase in the hepatic total lipids content, marked microvesicular steatosis and decrease in plasma lipids concentrations compared to control group. Fenofibrate treatment prevented fatty liver induction, caused an additional reduction on plasma lipids concentrations and caused a 40% decrease in the lipogenic rate in adipose tissue. The results also showed a 40% increase in lipoprotein lipase (LPL) activity in adipose tissue from OA treated group and fenofibrate administration induced a 50% decrease in LPL activity. The liver mRNA expression of PPARalpha and ACO (acyl CoA oxidase) were 85% and 68% decreased in OA group when compared to control, respectively. Fenofibrate treatment increased the PPARalpha and ACO expressions whereas the CPT-1 (carnitine palmitoyl transferase-1) expression was not altered. Our results have shown that fenofibrate treatment decreases the hepatic lipid content induced by OA which is mediated by an important increase in fatty acid oxidation consequent to an increase in hepatic mRNA expression of PPARalpha and ACO.     

Feeding of a low-zinc diet lowers the tissue concentrations of alpha-tocopherol in adult rats

Previous work has shown that a low dietary intake of zinc for a short duration significantly lowers the lymphatic absorption of α-tocopherol (αTP) in adult male rats. The present study investigated whether the nutritional status of zinc is critical in maintaining the tissue levels of the vitamin. One group of rats was fed an AIN-93G diet containing 3 mg zinc/kg (low zinc, LZ) and the other was fed the same diet but containing 30 mg zinc/kg (adequate zinc, AZ). Food intakes between groups were matched by feeding two meals per day. At 6 wk, the body weights (356±8 g) of LZ rats reached 98% those (362±10 g) of AZ rats. Feeding of the LZ diet for 6 wk significantly lowered the concentrations of both αTP and zinc in the liver, kidney, heart, testis, and brain. No consistent relationships between αTP and zinc concentrations were observed in other tissues such as spleen, lung, gastrocnemius muscle, and retroperitoneal fat tissues. The concentrations of αTP in the liver, testis, brain, spleen, heart, and kidney were significantly correlated with the tissue concentrations of zinc. The LZ diet slightly but significantly increased the total lipid contents (mg/g) of liver, kidney, heart, and spleen. However, the tissue levels of phospholipid (μmol/100 mg lipid) in the heart, lung, testis, and spleen were decreased significantly in LZ rats. These findings indicate that low zinc intake results in a pronounced decrease in the animal’s αTP status under the conditions of matched food intakes, body weights, and feeding patterns. The lower tissue levels of αTP may explain in part the compromised antioxidant defense system and increased susceptibility to oxidative damage observed in zinc deficiency.     

Zinc deficiency decreases plasma level and hepatic mRNA abundance of apolipoprotein A-I in rats and hamsters

The influence of Zn deficiency on the plasma level as well asthe hepatic and intestinal gene expression of apolipoprotein (apo) A-Iwas examined in rats and hamsters. Male Sprague-Dawley rats (8 wk old)and Golden Syrian hamsters (7 wk old) were assigned to three dietarytreatments: Zn adequate (ZA, 30 mg Zn/kg diet), Zn deficient (ZD,<0.5 mg Zn/kg diet), and Zn replete (ZDA, ZD animals fed the ZA dietfor the last 2 days). The dietary treatments lasted for 18 days forrats or 6 wk for hamsters. For the measurement of apoA-I mRNAabundance, hamster apoA-I cDNA was cloned from the small intestine. Thefull-length 905-base pair cDNA shared ~80% similarity with thehuman, rat, and mouse apoA-I cDNAs. Hepatic and plasma Zn levels werereduced in ZD animals but normalized in ZDA rats and increased in ZDAhamsters compared with ZA animals. Zn deficiency reduced plasma apoA-Iand hepatic apoA-I mRNA levels 13 and 38%, respectively, in ZD rats.The 2 days of Zn replenishment raised plasma apoA-I and hepatic apoA-ImRNA levels in ZDA rats by 34 and 28%, respectively, higher than ZArats. Similarly, these levels were decreased by 18 and 25%,respectively, in ZD hamsters but normalized in ZDA hamsters comparedwith ZA hamsters. In contrast to the alterations of hepatic apoA-I mRNAlevels, neither Zn deficiency nor subsequent Zn repletion producedalterations in the intestinal apoA-I mRNA abundance. Data from thisstudy demonstrated that Zn deficiency specifically decreases hepaticapoA-I gene expression, which may at least be partly responsible forthe reduction of plasma apoA-I levels.

     

Dependence of plasma alpha-tocopherol flux on very low-density triglyceride clearance in humans

To evaluate the effect of dietary fat-induced alterations in triglyceride (TG) metabolism on plasma and very low-density lipoprotein (VLDL)-alpha-tocopherol, nine healthy males (mean +/- SEM, age: 36 +/- 3 years, BMI: 24.7 +/- 1.1) consumed a 35%-fat diet (control) for one week followed by a 15% low-fat, high-carbohydrate diet for 5 weeks. After each dietary phase, the subjects ingested an evening meal along with a 50 mg capsule of (2)H(6)-RRR-alpha-tocopheryl acetate; blood samples were drawn over a 24 h period while the subjects remained fasted. Low-fat feeding increased fasting plasma TG concentrations by 53% (116 +/- 27 to 178 +/- 32, mg/dl, p < 0.0001) primarily by reducing VLDL-TG clearance. Total plasma alpha-tocopherol concentrations (labeled + unlabeled) were unchanged (25.8 +/- 2.3 vs. 26.4 +/- 3.0 nmol/ml plasma) and no differences between the diets were observed for plasma (2)H(6)-alpha-tocopherol concentration (4.8 +/- 0.6 nmol/ml, for both diets) or enrichments (18.1 +/- 1.8% average for both diets). However, low-fat feeding significantly increased the amount of alpha-tocopherol in the VLDL fraction (43%, p = 0.04) in concert with elevations in VLDL-apoB and TG. The alpha-tocopherol and TG content of VLDL varied in parallel in individual subjects and fractional replacement rates and clearance of alpha-tocopherol and TG in VLDL were closely correlated. Kinetic parameters were decreased by 32-39% from high-fat to low-fat. These data suggest that vitamin E bioavailability is similar between a 15 and 35% fat diet, with a redistribution of alpha-tocopherol in lipoproteins occurring during low-fat feeding (increased in the VLDL fraction, reduced in the other lipoproteins), and transfer of alpha-tocopherol from VLDL depends upon TG removal from the particle, consistent with previous observations in vitro and in animal studies.