Effects of combined selenium and vitamin E administration on DNA in Walker tumor bearing Wistar rat exposed to cytostatic acute treatment

Previous studies have showed that organic Se and Vitamin E have a significant protective effect when administered in combination with cytostatics. This paper reports the investigation on effects of mixed administration Orgasel 50 and Vitamin E in Wistar rat with experimentally induced Walker tumor under acute cytostatic treatment, with emphasis on two aspects: a) the influence of antioxidants upon liver unscheduled DNA biosynthesis under cytostatic (Lomustin) acute aggression; and b) the potential improvement of cytostatic effects by antioxidants treatment in tumor. Two lots of animals were used: lot 1 - Orgasel 50 and Vitamin E administered 7 days before the initiation of tumor induction and lot 2 - the antioxidants were concomitantly administered with tumor cell inoculation. The Walker tumor (an epithelial carcinoma) cells were subcutaneously injected (5 x 10(6) cells/0.5 ml in isotonic saline solution); the first tumor nodules appeared in 4 days; the tumor has reached the appropriate dimensions in 12 days. The unscheduled DNA biosynthesis caused by Lomustin in rat liver as well as the replicative DNA biosynthesis taking place in Walker tumor cells were assessed radioisotopically by measuring the uptake of 3H-Thymidine (200 microCi / 100 g.b.w.). Our observations regarding the role of antioxidant treatment suggest: 1) a benefic effect on DNA alkylant-induced lesions, expressed by a decrease in the level of 3H-Thymidine uptake in liver and, 2) an increase of the inhibitory activity of cytostatic on DNA replication biosynthesis in tumor cells, suggested by lower 3H-Thymidine incorporation in tumor cells. The most significant results were showed in both analyzed tissues, when the Orgasel 50 + Vitamin E administration begins at the same time with the tumor cell inoculation. These findings clearly show the organic Se salts and Vitamin E constitute a valuable adjuvant in anticancer medication, increasing the interest for the application of these antioxidants in cancer therapy and prevention.     

Leptin stimulates endogenous cholesterol synthesis in human monocytes: New role of an old player in atherosclerotic plaque formation. Leptin-induced increase in cholesterol synthesis

The role of leptin in the pathomechanism of atherosclerosis, through its free radical generating ability is established. Its effect however, on the regulation of intracellular cholesterol synthesis has not been studied. The aim of the present study was to elucidate whether leptin influences endogenous cholesterol synthesis in monocytes. Furthermore, leptin signaling to HMG CoA reductase in control and hypercholesterolemic monocytes were compared. The in vitro effect of leptin was studied on freshly isolated human monocytes obtained from healthy control volunteers and patients with hypercholesterolemia. Our results can be summarized as follows: (1) Leptin is able to increase endogenous cholesterol synthesis in human monocytes in vitro. (2) The cholesterol synthesis increasing effect of the hormone is more pronounced in hypercholesterolemic monocytes with high basal cholesterol biosynthesis. (3) The leptin-induced Ca(2+) signal was involved in the enhancement of HMG CoA reductase activation in monocytes from both controls and hypercholesterolemic patients. (4) In control monocytes the Ca(2+) signal originated from intracellular pools, whereas in patients, Ca(2+)-influx and protein kinase C activation were found to be responsible for the leptin-effect. Mevalonate cycle inhibiting fluvastatin and 25-hydroxycholesterol decreased cholesterol production in leptin-stimulated monocytes. Our present study provides the first proof of the cholesterol synthesis enhancing effect of leptin through a statin-sensitive pathway in circulating monocytes. Furthermore our results suggest that leptin can be involved in the pathomechanism of atherosclerotic plaque formation also through its effect on cholesterol biosynthesis in monocytes.     

Alendronate lowers cholesterol synthesis in the central nervous system of rats - a preliminary study

Nitrogen-containing bisphosphonates were found to inhibit farnesyl diphosphate synthase - an essential enzyme in the cholesterol biosynthesis pathway, but their effect on cholesterol synthesis per se in the central nervous system (CNS) remains unknown. The aim of the present study was to examine possible influence of a representative agent alendronate on cholesterol synthesis rates in selected parts of rat CNS and on plasma cholesterol level. Two groups of rats were orally administered either alendronate (3 mg/kg b.w.) or vehicle for 9 days. At the end of experiment, brain (basal ganglia, frontal cortex and hippocampus) and spinal cord were isolated and cholesterol synthesis was determined using the technique of deuterium incorporation from deuterated water. In the alendronate group significant reductions of cholesterol synthesis rates were detected in frontal cortex, hippocampus and spinal cord (p<0.001). However, the experimental treatment did not produce a significant alteration in the levels of plasma cholesterol. In conclusion, this study brings the first experimental evidence of the inhibition of cholesterol biosynthesis with alendronate in central nervous system.     

Antihypercholesterolemic and antioxidative effects of an extract of the oyster mushroom, Pleurotus ostreatus, and its major constituent, chrysin, in Triton WR-1339-induced hypercholesterolemic rats

Hypercholesterolemia and oxidative stress are known to accelerate coronary artery disease and progression of atherosclerotic lesions. In the present study, an attempt was made to evaluate the putative antihypercholesterolemic and antioxidative effects of an ethanolic extract of the oyster mushroom (Pleurotus ostreatus) and chrysin, one of its major components, in hypercholesterolemic rats. Hypercholesterolemia was induced in rats by a single intraperitoneal injection of Triton WR-1339 (300 mg/kg body weight (b.wt.)), which resulted in persistently elevated blood/serum levels of glucose, lipid profile parameters (total cholesterol, triglycerides, low-density lipoprotein-, and very low-density lipoprotein-cholesterol), and of hepatic marker enzymes (alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and lactate dehydrogenase). In addition, lowered mean activities of hepatic antioxidant enzymes (catalase, superoxide dismutase, and glutathione peroxidase) and lowered mean levels of nonenzymatic antioxidants (reduced glutathione, vitamin C, and vitamin E) were observed. Oral administration of the mushroom extract (500 mg/kg b.wt.) and chrysin (200 mg/kg b.wt.) to hypercholesterolemic rats for 7 days resulted in a significant decrease in mean blood/serum levels of glucose, lipid profile parameters, and hepatic marker enzymes and a concomitant increase in enzymatic and nonenzymatic antioxidant parameters. The hypercholesterolemia-ameliorating effect was more pronounced in chrysin-treated rats than in extract-treated rats, being almost as effective as that of the standard lipid-lowering drug, lovastatin (10 mg/kg b.wt.). These results suggest that chrysin, a major component of the oyster mushroom extract, may protect against the hypercholesterolemia and elevated serum hepatic marker enzyme levels induced in rats injected with Triton WR-1339.     

Relative resistance of the hamster to aortic atherosclerosis in spite of prolonged vitamin E deficiency and dietary hypercholesterolemia. Putative effect of increased HDL?

Male golden hamsters were rendered hypercholesterolemic by feeding diets enriched with cholesterol and fat. In the first series of experiments, 5% butter and 1% cholesterol were added to a chow diet and plasma cholesterol levels were maintained at 350–390 mg/dl over the entire experimental period. Groups of hamsters and their age controls consuming the chow diet, were killed after 7, 15 and 20 months when the aorta was examined for atherosclerosis by determination of cholesterol mass. In the controls, aortic total cholesterol (TC) increased with age by 28% and esterified cholesterol increased to 11% of TC. In the hypercholesterolemic animals aortic TC was only 28% higher than in the controls and cholesteryl ester was also 11.5% of TC. In the second series, one group of hamsters were fed a semi-purified diet deficient in vitamin E, containing 1% cholesterol and 10% lard; a second group received the same diet, but supplemented with vitamin E. Controls consumed local chow. After 7 months on the vitamin E deficient diet plasma α-tocopherol was 0.05 mg/l, in those supplemented with vitamin E it was 20 mg/l, while in the controls it was 3.3 mg/l. Plasma thiobarbituric acid reactive substances (TBARS) were higher in the vitamin E deficient group and there was a greater propensity of lipoproteins (d < 1.063 g/ml to peroxidation in vitro than in the vitamin E supplemented group. Plasma cholesterol was 366 mg/dl in the vitamin E deficient, 336 mg/dl in the vitamin E supplemented group, and 64 mg/dl in controls. Aortic cholesterol was 79.1 in vitamin E supplemented and 84.4 μg/ 10 mg dry weight in vitamin E deficient hamsters. In both series of experiments, HDL amounted to 36–41% of plasma TC in the hypercholesterolemic animals and 59–62% in the controls. In conclusion: the hamster appears to be quite resistant to atherosclerosis in face of sustained hypercholesterolemia, even in the presence of increased peroxidative stress caused by vitamin E deficiency. This relative resistance could be related to commensurate increase in plasma HDL which was observed in both series of experiments. Since vitamin E deficiency did not enhance aortic cholesteryl ester deposition, the protective effect of HDL seems to be related to its role in reverse cholesterol transport, rather than in prevention of peroxidation.     

The hydroxyphenylpyruvate dioxygenase from Synechocystis sp. PCC 6803 is not required for plastoquinone biosynthesis

Recently it has been reported that macrophages express a nuclear receptor, peroxisome proliferator-activated receptor γ (PPARγ). Using a ligand of PPARγ, troglitazone or pioglitazone, we have shown that the expression of two genes involved in cholesterol biosynthesis, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase and HMG-CoA reductase, were increased by activation of PPARγ through a PPAR response element (PPRE) in THP-1 macrophages. In addition, treatment with troglitazone significantly increased the activity of HMG-CoA reductase and the amount of intracellular cholesterol. Thus, we conclude that PPARγ and its agonists increase the cholesterol content of macrophages by the increased expression of genes involved in cholesterol biosynthesis. These findings suggest that PPARγ may play a role in cholesterol metabolism in macrophages.     

Effects of dietary fish oil supplementation on cellular adhesion molecule expression and tissue myeloperoxidase activity in hypercholesterolemic mice with sepsis

This study investigated the effects of fish oil on adhesion molecule expression and tissue myeloperoxidase (MPO) activity in hypercholesterolemic mice with sepsis. There were one control and two experimental groups in this study. The control group (C) was fed a regular chow diet for 7 weeks, while hypercholesterolemia in the experimental group was induced by feeding a high-fat diet (20%, w/w) with cholesterol (2%, w/w) for 4 weeks. Then the experimental group was divided into two subgroups with identical nutrient distributions except that one subgroup was fed soybean oil (SO), while part of the soybean oil was replaced by fish oil (FO) in the other one for 3 weeks. After feeding the diets for 7 weeks, sepsis was induced in all three groups by cecal and ligation and puncture (CLP), and mice were sacrificed at 0, 6 or 24 h after CLP, respectively. The results showed that the FO group had a higher intracellular interferon-gamma/interleukin-4 ratio and lower tumor necrosis factor-alpha and monocyte chemoattractant protein-1 concentrations in peritoneal lavage fluid at 6 h after CLP than those in the C and SO groups. Lymphocyte CD11a/CD18 expressions were higher at 0 and 6 h and neutrophil CD11b/CD18 were higher at 6 h in the SO group than in the FO and C groups. The SO group had higher plasma intercellular adhesion molecule (ICAM)-1 levels than C group at 0 and 6 h, whereas no difference in ICAM-1 concentrations were observed between the C and FO groups at 0 h after CLP. Hypercholesterolemia resulted in higher tissue MPO activities. There were no differences in MPO activities in various organs between the two experimental groups. These results suggest that hypercholesterolemic mice fed FO did not exhibit immunosuppression when complicated with sepsis. FO administration reduced adhesion molecule expressions and inflammatory-related mediators at the site of injury at an early but not a late stage of sepsis. However, compared with the SO group, the influences of FO on MPO activities in various organs were not obvious in hypercholesterolemic mice with sepsis.     

The Effect of Boron on Some Biochemical Parameters in Experimental Diabetic Rats

In this study, we evaluated the effect of boron (B) as boric acid (BA) on body weight (b.w.); blood glucose; plasma insulin; lipase and paraoxonase (PON1) activities; and serum triglyceride, total cholesterol, high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol, lipid peroxidation (MDA), and total antioxidant capacity (TAC) in streptozotocin (STZ)-induced experimental diabetes in rats. Sixty Wistar albino rats (200–250 g) were divided into six groups of ten. The groups received the following treatment: group 1, control group; group 2, 50 mg/kg (b.w.) i.p. STZ-induced diabetes; group 3, 5 mg/kg (b.w.) B; group 4, 10 mg/kg (b.w.) B; group 5, diabetes + 5 mg/kg (b.w.) B; and group 6, diabetes + 10 mg/kg (b.w.) B. The experiment lasted 4 weeks. Increased serum MDA levels with diabetes were significantly reduced and although it is not statistically significant, serum TAC levels approached to values of control group; also, insignificant increases were observed in HDL cholesterol levels in experimental diabetic rats with treatment 5 and 10 mg/kg B. Furthermore, body weight, plasma insulin, and lipase activities increased insignificantly, blood glucose and serum LDL cholesterol decreased significantly, and total cholesterol levels decreased insignificantly in the diabetes + 10 mg/kg B group. There was no difference between the groups in terms of plasma PON1 activities and serum triglyceride levels. In conclusion, B may have beneficial effects on some biochemical parameters changes in experimental diabetes, and in order to determine the full effect of this element on the metabolism, further studies are required which use various dosages and compounds of B.     

The effect of PPAR ligands to modulate glucose metabolism alters the incorporation of metabolic precursors into proteoglycans synthesized by human vascular smooth muscle cells

PPAR ligands are important effectors of energy metabolism and can modify proteoglycan synthesis by vascular smooth muscle cells (VSMCs). Describing the cell biology of these important clinical agents is important for understanding their full clinical potential, including toxicity. Troglitazone (10 microM) and fenofibrate (30 microM) treatment of VSMCs reduces ((35)S)-sulphate incorporation into proteoglycans due to a reduction of glycosaminoglycan (GAG) chain length. Conversely, under physiological glucose conditions (5.5 mM), the same treatment increases ((3)H)-glucosamine incorporation into GAGs. This apparent paradox is the consequence of an increase in the intracellular ((3)H)-galactosamine specific activity from 48.2 +/- 3.2 microCi/ micromol to 90.7 +/- 11.0 microCi/ micromol (P < 0.001) and 57.1 +/- 2.6 microCi/ micromol (P < 0.05) when VSMCs were treated with troglitazone and fenofibrate, respectively. The increased specific activity observed with troglitazone (10 microM) treatment correlates with a two-fold increase in glucose consumption, while fenofibrate (50 microM) treatment showed a modest (14.6%) increase in glucose consumption. We conclude that the sole use of glucosamine precursors to assess GAG biosynthesis results in misleading conclusions when assessing the effect of PPAR ligands on VSMC proteoglycan biosynthesis.     

The effect of heat-stable extract from bovine sublingual salivary gland on serum cholesterol and triglyceride levels in normal and hypercholesterolemic rabbits

An extract of bovine sublingual glands (SLF3) reduced the serum cholesterol levels of normal rabbits 34.6% and serum triglyceride levels 19.6% when injected intraperitoneally (i.p.) at 20 mg/kg body wt on alternate days for 7 days. SLF3 also reduced serum cholesterol levels 69.0% and triglyceride levels 46.5% in hypercholesterolemic rabbits, while in similar rabbits injected with a control muscle tissue extract, the rate of decrease in serum cholesterol levels was 33.3% and triglyceride levels 26.7%.     

Proprotein convertase subtilisin/kexin type 9 (PCSK9) affects gene expression pathways beyond cholesterol metabolism in liver cells

Proprotein convertase subtilisin/kexin type 9 (PCSK9) induces degradation of low‐density lipoprotein receptor (LDLR) in the liver. It is being pursued as a therapeutic target for LDL‐cholesterol reduction. Earlier genome‐wide gene expression studies showed that PCSK9 over‐expression in HepG2 cells resulted in up‐regulation of genes in cholesterol biosynthesis and down‐regulation of genes in stress response pathways; however, it was not known whether these changes were directly regulated by PCSK9 or were secondary to PCSK9‐induced changes to the intracellular environment. In order to further understand the biological function of PCSK9 we treated HepG2 cells with purified recombinant wild type (WT) and D374Y gain‐of‐function PCSK9 proteins for 8, 24, and 48 h, and used microarray analysis to identify genome‐wide expression changes and pathways. These results were compared to the changes induced by culturing HepG2 cells in cholesterol‐free medium, mimicking the intracellular environment of cholesterol starvation. We determined that PCSK9‐induced up‐regulation of cholesterol biosynthesis genes resulted from intracellular cholesterol starvation. In addition, we identified novel pathways that are presumably regulated by PCSK9 and are independent of its effects on cholesterol uptake. These pathways included “protein ubiquitination,” “xenobiotic metabolism,” “cell cycle,” and “inflammation and stress response.” Our results indicate that PCSK9 affects metabolic pathways beyond cholesterol metabolism in HepG2 cells. J. Cell. Physiol. 224:273–281, 2010 © 2010 Wiley‐Liss, Inc.     

The protective effect of the Cornus mas fruits (cornelian cherry) on hypertriglyceridemia and atherosclerosis through PPARα activation in hypercholesterolemic rabbits

Cornelian cherry (Cornus mas L.) fruits have been used in traditional cuisine and in folk medicine in various countries. This study was conducted to evaluate the constituents and impact of cornelian cherry (C. mas L.) fruits lyophilisate on lipid levels, PPARα protein expression, atheromatous changes in the aorta, oxido-redox state, and proinflammatory cytokines in hypercholesterolemic rabbits. The HPLC–MS method was used for determining active constituents in cornelian cherry. In a subsequent in vivo study the protective effect of the cornelian cherry on diet-induced hyperlipidemia was studied using a rabbit model fed 1% cholesterol. Cornelian cherry (100 mg/kg b.w.) or simvastatin (5 mg/kg b.w.) were administered orally for 60 days. Two iridoids – loganic acid and cornuside – and five anthocyanins were identified as the main constituents of the cornelian cherry. The administering of the cornelian cherry led to a 44% significant decrease in serum triglyceride levels, as well as prevented development of atheromatous changes in the thoracic aorta. Cornelian cherry significantly increased PPARα protein expression in the liver, indicating that its hypolipidemic effect may stem from enhanced fatty acid catabolism. Simvastatin treatment did not affect PPAR-α expression. Moreover, the cornelian cherry had a significant protective effect on diet-induced oxidative stress in the liver, as well as restored upregulated proinflammatory cytokines serum levels. In conclusion, we have shown loganic acid to be the main iridoid constituent in the European cultivar of the cornelian cherry, and proven that the cornelian cherry could have protective effects on diet-induced hypertriglicerydemia and atherosclerosis through enhanced PPARα protein expression and via regulating oxidative stress and inflammation.     

Effect of baikal skullcap root (Scutellaria baicalensis radix) on cholesterol level and meat quality in rabbits fed a cholesterol rich diet

The aim of this study was to evaluate the effect of the Baikal skullcap root (Scutellaria baicalensis radix) on the cholesterol level and chemical composition of the hind leg muscles of rabbits. Thirty two White New Zealand rabbits were assigned to four groups. Group C consisted of control animals which were fed a basal mixture for rabbits. Group CH received the same basal diet with a 1% (w/w) pure cholesterol supplement. Group CH+SR received the basal diet with two supplements: 1% (w/w) pure cholesterol and 9% (w/w) skullcap root. Group SR received the basal diet with a 9% (w/w) skullcap root supplement. After 6 weeks rabbits were slaughtered and, total cholesterol as well as dry matter, protein, fat, ash and pH24 were determined in samples of hind leg muscles. Using a Baikal skullcap root with hypercholesterolemic diet (group CH+SR) caused significant reduction (P < or = 0.05) in total cholesterol level in comparison with hypercholesterolemic diet (CH group). The addition of Baikal skullcap root to the food of rabbits significantly increased the muscle protein content (P < or = 0.05) in comparison with C and CH groups. Moreover, supplementation with Baikal skullcap root (CH+SR) decreased about 15.6% (P < or = 0.05) fat level in comparison to CH group. No significant effects were seen in dry matter content, ash, and pH24 value of hind leg muscles of experimental rabbits     

Effect of trifluoperazine on cholesterol metabolism of smooth muscle cells exposed to hypercholesterolemic medium in vitro

We recently demonstrated that the preventive effect of trifluoperazine (a potent inhibitor of calmodulin, protein kinase C, and phospholipase A2) on cholesterol-induced atherogenic activity of smooth muscle cells was mediated through its ability to inhibit smooth muscle cellular DNA synthesis coupled with stimulation of LDL receptor synthesis. The present study addressed the effect of trifluoperazine on cholesterol metabolism of aortic SMCs enriched with cholesterol through the nonreceptor pathway and revealed that (a) TFP caused inhibition of cholesterol synthesis compared with control cells bathed with hypercholesterolemic medium alone. (b) The drug also caused inhibition of free cholesterol and cholesteryl ester accumulation within smooth muscle cells compared to control cells. These results demonstrate that the preventive effect of TFP on atherogenic activity of smooth muscle cells may also be due to its ability to affect the altered/modified cholesterol metabolism of smooth muscle cells exposed to hypercholesterolemic medium in vitro.     

Lack of Effect of Vitamin E on Cholesteryl Ester Transfer and Lipoprotein Composition in Cholesterol-fed Rabbits

The concentration and activity of cholesteryl ester transfer protein (CETP) is increased in plasma in hypercholesterolemic humans and in experimental animals fed cholesterol. While the concentration of lipoproteins appears to be the major determinant of CETP activity, we have found previously that dietary measures and pharmacologic agents that alter their lipid composition reduce the activity of CETP in plasma (CET). Since vitamin E is lipophilic and is incorporated into lipoproteins, we have examined the question of whether it too attenuates CET in cholesterol-fed New Zealand White rabbits prior to and 14 weeks after treatment with differing doses (5, 15, 30, 45 mg/kg) of vitamin E. Plasma triglycerides (TG), cholesterol (TC) and phospholipids (Lys, Sph, Lec, PI, PE) all increased significantly to a comparable degree in the rabbits fed cholesterol compared to those fed chow (p < 0.05; p < 0.01); the levels achieved were similar in the vitamin E-treated and untreated groups. As was observed with plasma lipids, cholesteryl ester transfer (CET) was accelerated to the same degree in each of the cholesterol-fed groups independent of whether they received vitamin E compared to chow-fed controls (p < 0.01) and the distribution of cholesterol in apo-B containing lipoproteins (VLDL, IDL, and LDL) was similar in the vitamin E-treated and untreated groups. These findings indicate that vitamin E has no discernible effect on CET when cholesterol levels are markedly elevated.     

Effect of Artichoke Leaf Extract on Hepatic and Cardiac Oxidative Stress in Rats Fed on High Cholesterol Diet

Hypercholesterolemia and lipid peroxidation play complementary roles in atherosclerosis. Artichoke (Cynara scolymus L., Asteraceae) leaf extract (ALE), rich in antioxidants, has cholesterol-reducing effect. We investigated the effect of ALE on serum and hepatic lipid levels and pro-oxidant–antioxidant balance in the liver and heart of hypercholesterolemic rats. Rats were fed on 4% (w/w) cholesterol and 1% cholic acid (w/w) supplemented diet for 1 month. ALE (1.5 g/kg/day) was given by gavage during the last 2 weeks. High cholesterol (HC) diet caused significant increases in serum and liver cholesterol and triglyceride levels. It increased malondialdehyde (MDA) and diene conjugate (DC) levels in both tissues. Hepatic vitamin E levels and hepatic and cardiac glutathione peroxidase (GSH-Px) activities decreased, but superoxide dismutase and glutathione transferase activities, glutathione, and vitamin C levels remained unchanged due to HC diet. Serum cholesterol and triglyceride levels and ratio of cholesterol to high-density lipoprotein (HDL)-cholesterol decreased in ALE plus HC-treated rats, but liver cholesterol and triglyceride levels remained unchanged. Significant decreases in hepatic and cardiac MDA and DC levels and increases in hepatic vitamin E and GSH-Px activities were observed in ALE-treated hypercholesterolemic rats. Our results indicate that ALE decreases serum lipids and hypercholesterolemia-induced pro-oxidant state in both tissues.     

Distribution of Tocotrienols in Rats Fed a Rice Bran Tocotrienol Concentrate

To examine the distribution of rice bran tocotrienol (T3), we gave rice bran T3 to rats after considering an acceptable daily intake of vitamin E for humans. Male SD rats (5 weeks of age) were fed for 3 weeks on a commercial diet containing 6.4 mg of vitamin E per 100 g wt and additively received vitamin E or the vehicle (vitamin E-free corn oil) by oral intubation. The animals were randomly divided into 4 groups depending on the type of test diet: control (vehicle), non-T3 (no T3 + 4.3 mg of tocopherol (TOC)/kg body weight (b.w.)/day), low-T3 (0.8 mg T3 + 3.5 mg TOC/kg b.w./day), and high-T3 (3.2 mg T3 + 1.1 mg TOC/kg b.w./day). The control rats and rats in the non-T3, low-T3, and high-T3 groups took 4.3 and 8.6 mg of vitamin E/kg b.w./day, respectively. Rice bran γ-T3 was significantly distributed to the adipose tissue and increased from 1.1 to 10.2 nmol/g of adipose tissue according to the rice bran T3 intake.     

Intestinal lipoprotein synthesis in control and hypercholesterolemic rats

Previous studies in our laboratory have shown that very-low-density lipoproteins (VLDL) synthesized by the intestine of the diet-induced hypercholesterolemic rat are enriched in cholesteryl esters and unesterified cholesterol compared with intestinal VLDL from control rats. In these studies, we isolated and characterized nascent intestinal Golgi intermediate-density lipoproteins (IDL, d 1.006-1.040 g/ml) and studied isotope incorporation into apoliproteins of Golgi VLDL from control and hypercholesterolemic rats. IDL were triacylglycerol-rich lipoproteins but contained more cholesteryl ester and protein than the corresponding Golgi VLDL fractions. IDL from hypercholesterolemic rats were enriched in cholesteryl esters to a greater extent than IDL from control rats. The apolipoprotein patterns of IDL fractions were the same as those of intestinal Golgi VLDL, consisting of apolipoproteins (apo) B-48, A-I and A-IV. Time-course isotope incorporation curves for apo A-I and A-IV in Golgi VLDL were similar, but they differed from curves for apo B-48. None of these curves was markedly altered in the hypercholesterolemic rat. We conclude that the major effect of increased dietary cholesterol on intestinal lipoprotein biosynthesis is to increase the percentage of cholesteryl esters in Golgi lipoproteins. Dietary cholesterol does not alter the apolipoprotein composition of Golgi lipoproteins, nor does it have a significant effect on the pattern of isotope incorporation into apolipoproteins of Golgi VLDL. The effect of cholesteryl ester enrichment on the subsequent metabolism of these particles in the circulation and the effect of these particles on hepatic lipoprotein production remain to be determined.     

Cholesterol, 7-ketocholesterol and 25-hydroxycholesterol uptake studies and effect on 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity in human fibroblasts.

In human fibroblasts two oxidized derivatives of cholesterol, 7-ketocholesterol and 25-hydroxycholesterol, but not cholesterol itself, are potent inhibitors of 3-hydroxy-3-methylglutaryl co-enzyme A reductase (mevalonate: NADP+ oxidoreductase (Co-enzyme A acylating), (EC 1.1.1.34), the rate-limiting enzyme in sterol biosynthesis. In addition, these derivatives of cholesterol are effective regulators in cells from homozygous familial hypercholesterolemic individuals. The differences in the inhibitory potencies of the sterols cannot be explained in terms of the amount of uptake into the cell.