Clofibric acid induces hepatic CYP 2B1/2 via constitutive androstane receptor not via peroxisome proliferator activated receptor alpha in rat.

Peroxisome proliferator activated receptor α (PPARα) ligands, fibrates used to control hyperlipidemia. We demonstrated CYP2B induction by clofibric acid (CFA) however, the mechanism was not clear. In this study, HepG2 cells transfected with expression plasmid of mouse constitutive androstane receptor (CAR) or PPARα were treated with CFA, phenobarbital (PB) or TCPOBOP. Luciferase assays showed that CFA increased CYP2B1 transcription to the same level as PB, or TCPOBOP in HepG2 transfected with mouse CAR But failed to induce it in PPARα transfected cells. CYP2B expressions were increased with PB or CFA in Wistar female rats (having normal levels of CAR) but not in Wistar Kyoto female rats (having low levels of CAR). The induction of CYP2B by PB or CFA was comparable to nuclear CAR levels. CAR nuclear translocation was induced by CFA in both rat strains. This indicates that fibrates can activate CAR and that fibrates-insulin sensitization effect may occur through CAR, while hypolipidemic effect may operate through PPARα.

Conservative treatment of L-asparaginase-associated lipid abnormalities in children with acute lymphoblastic leukemia.

OBJECTIVE: To determine the incidence and clinical consequences of asparaginase-associated lipid abnormalities in children with acute lymphoblastic leukemia (ALL). METHODS: Sixty-five newly diagnosed children and adolescents aged 0.4-21 years with ALL or lymphoblastic lymphoma were retrospectively evaluated for lipid abnormalities. They were treated according to the ALLIC-BFM 2002 protocol between 2002 and 2005. Fasting cholesterol levels were measured in all patients and triglycerides (TG) in 42/65 patients. RESULTS: Prior to treatment, mean cholesterol level was 149 +/- 50 mg/dl, and increased to maximal level 274 +/- 124 mg/dl during treatment. Mean TG level during treatment was 459 +/- 526 mg/dl (range 54-3,009). Twelve patients (28%) had TG levels <200 mg/dl, 18 (43%) had 200-400 mg/dl, 3 (7%) had 400-600 mg/dl, 4 (10%) between 600 and 1,000 mg/dl, and 5 (12%) patients had >1,000 mg/dl. No association was found between TG levels and age or gender. One of the 12 patients with TG >400 mg/dl developed left saggital sinus thrombosis and left frontal lobe infarct. TG level at the time of the event was 2,640 mg/dl. None of the five patients with TG levels >1,000 mg/dl developed pancreatitis. Children with TG levels between 400 and 600 mg/dl were treated by fasting. Fibrates and heparin were added to those with levels >600 mg/dl. Lipid abnormalities normalized in all children upon completion of asparaginase treatment. CONCLUSIONS: Abnormalities of lipid profile in children with ALL during asparaginase therapy are relatively common. We recommend measuring TG before and during asparaginase treatment. Initiation of conservative treatment could prevent further increase of TG and decrease the risk of potential complications.

[Effectiveness of cardiometabolic risk reduction in patients with type 1 diabetes mellitus]. / A kardiometabolikus kockázati tényezôk kezelésének eredményessége 1-es típusú diabetesben szenvedôk körében.

UNLABELLED: The attainment and maintenance of therapeutic goal of cardiovascular risk factors are of great clinical importance. The effectiveness of cardiovascular risk management is not well characterized during regular care of patients with type 1 diabetes mellitus. AIM: The aim of the study was to estimate the effectiveness of cardiovascular risk management in type 1 diabetic patients. METHODS: Adult patients with type 1 diabetes mellitus (n = 533; 256 men, 277 women; age: 35.6 +/- 11.6 years; duration of diabetes: 18.0 +/- 11.1 years; x +/- SD) were consecutively enrolled from 11 diabetes outpatient departments. Data on medical history, actual treatment, anthropometric and laboratory parameters as well as actual blood pressure were registered, while eating and smoking habits, education level and physical activity were evaluated by standardized questionnaires. The treating goal was set according to the national guideline which corresponds to the current international task force. RESULTS: Of 533 patients, the body mass index target level (< 25 kg/m 2 ) was achieved by 295 (55.5%) patients. Ideal waist circumference (< 80 cm for women and < 94 cm for men) was measured in 140 (50.5%) and in 165 (63.7%) patients, respectively. Optimal glycaemic control (HbA 1c level < 6.5%) was documented in 45 (8.4%) patients. Lipid lowering drugs (statins, fibrates or ezetimibe) were used by 130 patients, among which 53.1% reached the target triglyceride level, 71.5% the target HDL-cholesterol and 27.8% the target LDL-cholesterol levels. Taking the lipid target values together, only 23 (17.7%) patients were at goal. Antihypertensive drugs were used by 173 patients among which 29.5% reached the systolic and 34.8% the diastolic target values (< 130/80 mmHg). Regarding smoking habits, 94 (17.7%) patients were current smokers and 102 (19.2%) ex-smokers. CONCLUSIONS: The attainment of therapeutic goal of cardiovascular risk factors proved to be difficult in a substantial part of patients. Further efforts are needed for attaining and maintaining the established goal of cardiovascular risk management during regular care of adult patients with type 1 diabetes mellitus.

Clofibric acid, a peroxisome proliferator-activated receptor alpha ligand, inhibits growth of human ovarian cancer.

Recent reports have shown that peroxisome proliferator-activated receptor (PPAR)alpha ligands reduce growth of some types of malignant tumors and prevent carcinogenesis. In this study, we investigated the inhibitory effect of clofibric acid (CA), a ligand for PPARalpha on growth of ovarian malignancy, in in vivo and in vitro experiments using OVCAR-3 and DISS cells derived from human ovarian cancer and aimed to elucidate the molecular mechanism of its antitumor effect. CA treatment significantly suppressed the growth of OVCAR-3 tumors xenotransplanted s.c. and significantly prolonged the survival of mice with malignant ascites derived from DISS cells as compared with control. CA also dose-dependently inhibited cell proliferation of cultured cell lines. CA treatment increased the expression of carbonyl reductase (CR), which promotes the conversion of prostaglandin E(2) (PGE(2)) to PGF(2alpha), in implanted OVCAR-3 tumors as well as cultured cells. CA treatment decreased PGE(2) level as well as vascular endothelial growth factor (VEGF) amount in both of OVCAR-3-tumor and DISS-derived ascites. Reduced microvessel density and induced apoptosis were found in solid OVCAR-3 tumors treated by CA. Transfection of CR expression vector into mouse ovarian cancer cells showed significant reduction of PGE(2) level as well as VEGF expression. These results indicate that CA produces potent antitumor effects against ovarian cancer in conjunction with a reduction of angiogenesis and induction of apoptosis. We conclude that CA could be an effective agent in ovarian cancer and should be tested alone and in combination with other anticancer drugs.

[Analysis of dietary habits and dietary intake in hypertensive smokers]. / Ocena zwyczajów zywieniowych i sposobu zywienia osób palacych papierosy z nadcisnieniem tetniczym.

The aim of this study was to compare dietary habits and nutrient intake of hypertensive smokers with hypertensive non-smokers. The study population comprised 30 hypertensive smokers and 35 non-smokers, aged 30-60y. The participants were subjected to a triple 24-h diet recall and to a dietary habits questionnaire. The results showed that smokers had unhealthy patterns of nutrient intake. Smokers declared consuming too much fat, cholesterol and too low antioxidant vitamins, calcium and fibre. It was found that concentration of vitamin E in smokers' daily diet is significant lower than in non-smokers. Smokers consumed significantly higher saturated fatty acids comparing to non-smokers. In conclusion, smokers have unhealthy diet and it may intensify harmful effects of smoking in their organism.

Modulation of hepatic canalicular or basolateral transport proteins alters hepatobiliary disposition of a model organic anion in the isolated perfused rat liver.

This study examined the impact of hepatic transport protein modulation on the hepatobiliary disposition of a nonmetabolized probe substrate, 5- (and 6)-carboxy-2',7'dichlorofluorescein (CDF) in rat isolated perfused livers (IPLs). In vivo treatment with modulators (100 and 200 mg/kg/day clofibric acid, 80 mg/kg/day phenobarbital, and 25 mg/kg/day dexamethasone) was used to alter the expression of hepatic transport proteins [organic anion transporting polypeptide 1a1, multidrug resistance-associated protein (Mrp) 3, and Mrp2] governing the disposition of CDF. The basolateral and biliary excretion of CDF was measured in single-pass IPLs from control and treated rats. Modulators increased the percentage of CDF eliminated into perfusate of IPLs from treated rats ( approximately 20-35%) compared with controls ( approximately 10%); CDF biliary excretion was decreased in the treated groups. These observations are consistent with modulator-associated increases in the first-order rate constant governing CDF excretion from the hepatocytes into perfusate (k(perfusate)) or decreases in the first-order rate constant governing CDF excretion into bile (k(bile)). Pharmacokinetic modeling of the data and subsequent simulations revealed that the routes of CDF excretion were most sensitive to changes in k(perfusate). In contrast, hepatic accumulation of CDF was most sensitive to k(bile). The differential sensitivity of CDF excretory routes and hepatic accumulation to these rate constants is a function of intrahepatic distribution kinetics, which must be taken into consideration in assessing the potential impact of altered hepatobiliary transport processes.

Statin and fibrate treatment of combined hyperlipidemia: the effects on some novel risk factors.

The effects of cerivastatin and fenofibrate on proteins involved in haemostasis and on markers of inflammation were investigated in otherwise healthy middle-aged males with combined hyperlipidemia. Besides classical risk factors, other so-called novel risk factors for coronary artery disease are seen to be playing an increasingly important role in the development and progression of atherosclerosis. Thirty-eight males, aged 49 +/-5 years were randomised to 12 weeks treatment either with cerivastatin at a daily dose of 0.2 mg to 0.4 mg to achieve the LDL cholesterol goal of <3.0 mM, or with fenofibrate 250 mg daily. Fasting serum lipids, homocysteine, total and free tissue factor pathway inhibitor (TFPI), plasminogen activator inhibitor (PAI-1) and tissue plasminogen activator (t-PA) antigen and activity, C-reactive protein (CRP), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) were measured. No change in homocysteine level was observed in the cerivastatin group, while after fenofibrate administration it increased (p <0.0001). Total TFPI decreased significantly after cerivastatin (p = 0.002), but not after fenofibrate. Free TFPI did not decrease after either drug. Neither drug affected (t-PA) antigen and activity, while fenofibrate increased PAI-1 antigen (p <0.05) and activity (p <0.05). Cerivastatin decreased serum CRP values by 49.5% (p = 0.001), and fenofibrate by 29.8% (p = 0.03). The decreases of CRP in the two groups differed significantly (p = 0.04). IL-6 levels decreased significantly in the fenofibrate group (39%; p <0.0001), but not in the cerivastatin group (15%; p = 0.24) No significant decreases were observed for TNF-alpha. Cerivastatin had neutral effects on fibrinolysis, homocysteine or coagulation. On the other hand, fenofibrate increased PAI-1 antigen and activity and homocysteine, and did not affect coagulation. Both cerivastatin and fenofibrate reduced CRP levels, the decrease being significantly greater after cerivastatin. Fenofibrate also significantly decreased IL-6.

Liver gene expression profiles of rats treated with clofibric acid: comparison of whole liver and laser capture microdissected liver.

Clofibric acid (CLO) is a peroxisome proliferator (PP) that acts through the peroxisome proliferator activated receptor alpha, leading to hepatocarcinogenesis in rodents. CLO-induced hepatocarcinogenesis is a multi-step process, first transforming normal liver cells into foci. The combination of laser capture microdissection (LCM) and genomics has the potential to provide expression profiles from such small cell clusters, giving an opportunity to understand the process of cancer development in response to PPs. To our knowledge, this is the first evaluation of the impact of the successive steps of LCM procedure on gene expression profiling by comparing profiles from LCM samples to those obtained with non-microdissected liver samples collected after a 1 month CLO treatment in the rat. We showed that hematoxylin and eosin (H&E) staining and laser microdissection itself do not impact on RNA quality. However, the overall process of the LCM procedure affects the RNA quality, resulting in a bias in the gene profiles. Nonetheless, this bias did not prevent accurate determination of a CLO-specific molecular signature. Thus, gene-profiling analysis of microdissected foci, identified by H&E staining may provide insight into the mechanisms underlying non-genotoxic hepatocarcinogenesis in the rat by allowing identification of specific genes that are regulated by CLO in early pre-neoplastic foci.

Cell proliferation and apoptosis are altered in mice deficient in the NF-kappaB p50 subunit after treatment with the peroxisome proliferator ciprofibrate.

We previously showed that the peroxisome proliferator ciprofibrate increases hepatic NF-kappaB DNA binding activity in rats, mice, and hepatoma cell lines. Here, we analyzed the response to ciprofibrate in mice that lack the NF-kappaB p50 gene (p50-/-). Wild-type and p50-/- mice were fed a diet with or without 0.01% ciprofibrate for 10 days. NF-kappaB DNA binding activity was present and increased after ciprofibrate treatment in wild-type mice, but was not detected in p50-/- mice. The untreated p50-/- mice had a higher level of hepatic cell proliferation, as measured by BrdU labeling, than did untreated wild-type mice. However, the increase in proliferation was greater in ciprofibrate-fed wild-type mice than in ciprofibrate-fed p50-/- mice. The apoptotic index was low in wild-type mice in the presence or absence of ciprofibrate. Apoptosis was increased in untreated p50-/- mice compared to wild-type mice; apoptosis was reduced in p50-/- mice after ciprofibrate feeding. The c-Jun and JunB mRNA levels were higher in untreated p50-/- mice than in untreated control mice; c-Jun mRNA levels increased, whereas JunB mRNA levels decreased in both groups after ciprofibrate treatment. The c-Jun and JunB protein levels were the same in untreated wild-type and p50-/- mice and increased in both groups after ciprofibrate treatment. Several apoptosis-related mRNAs were higher in untreated p50-/- mice compared to untreated control mice; expression of these genes increased in both groups after ciprofibrate treatment. These data indicate that NF-kappaB contributes to the proliferative and apoptotic changes that occur in the liver in response to ciprofibrate.

Clofibric acid or diethylmaleate supplemented diet decrease blood pressure in DOCA-salt treated male Sprague Dawley rats--relation with liver antioxidant status.

The effects of 8-week diethylmaleate (DEM) and clofibric acid (CFA) supplemented diet on blood pressure, body and liver weights, liver antioxidant status and nitric oxide synthase (NOS) activity were investigated in 8-week DOCA-salt treated and untreated Sprague-Dawley male rats. It appeared that DEM and particularly CFA treatments were associated with a significant decrease in blood pressure in DOCA-salt treated rats, and an accentuation of the decreases in body weights in both diet supplemented groups. This was not associated with increases in NO production in the liver. In contrast, hepatic lipid peroxidation was significantly decreased in both DOCA-salt treated and untreated groups on DEM and particularly on CFA supplemented diet. The protective effects of CFA and DEM against hepatic cellular damage could be involved in the decreases in blood pressure in DOCA-salt treated rats, where CFA was more efficient than DEM. In CFA supplemented groups, there was a strong increase in hepatic superoxide dismutase (SOD), glutathione-peroxidase (GSH-Px), and catalase (CAT) activities and in DEM supplemented groups, increases in SOD and CAT activities and in GSH levels were observed. Our data suggest that normalization of blood pressure in DOCA-salt treated rats by CFA was due to an enhancement of the half-life of NO while DEM increased its availability.

Retrospective evaluation of serum ornithine carbamyltransferase activity as an index of hepatotoxicity in toxicological studies with rats.

The sensitivity of elevated serum ornithine carbamyltransferase (OCT) as an index of hepatotoxicity in rats was assessed in different studies conducted over a number of years and originally designed to examine the toxicity or carcinogenicity of a variety of test chemicals and diets. Changes in serum OCT activities were compared with the more widely used clinical endpoints, alanine aminotranserase (ALT) and aspartate aminotransferase (AST). In the first study, rats received a single oral dose of the hepatotoxic and hepatocarcinogenic fungal toxin aflatoxin B(1) (AFB(1)). The increase in enzyme levels between control and AFB(1)-treated rats was greater for serum OCT than for ALT or AST. This response was similar to the changes in serum enzyme levels in studies where rats ingested a hepatotoxic and hepatocarcinogenic choline deficient (CD) diet. When rats were exposed to the hepatotoxic and nephrotoxic fungal toxin fumonisin B(1) (FB(1)) by intraperitoneal injection for 6 days, serum AST and ALT were significantly elevated above control levels while OCT was unaffected. The peroxisome proliferator ciprofibrate caused elevated ALT and AST but not OCT at week 52 of dietary exposure, after the development of liver nodules and tumours. Of the two liver-specific enzymes examined in all of the studies, ALT was more consistently predictive of hepatotoxicity than OCT.

Effect of the peroxisome proliferator ciprofibrate on lipid peroxidation and 8-hydroxydeoxyguanosine formation in transgenic mice with elevated hepatic catalase activity.

Peroxisome proliferators are a group of non-genotoxic hepatic carcinogens which have been proposed to act by increasing oxidative damage in the liver. To test this hypothesis, we have produced a transgenic mouse line that has elevated catalase activity specifically in the liver. In this study, we have examined if catalase overexpression influences the induction of lipid peroxidation or oxidative DNA damage, two mechanisms which have been hypothesized to be important in the carcinogenesis by peroxisome proliferators. Transgenic mice or non-transgenic litter mates were fed either 0.01% ciprofibrate or a control diet for 21 days. The activities of fatty acyl CoA oxidase and lauric acid hydroxylase were not significantly affected by catalase overexpression, although the ratio of fatty acyl CoA oxidase to catalase was significantly decreased in transgenic animals. Hepatic lipid peroxidation was estimated by quantifying the concentrations of malondialdehyde and conjugated dienes. Ciprofibrate treatment did not affect either endpoint, but catalase overexpression increased the concentrations of malondialdehyde (in untreated mice only) and conjugated dienes (in both untreated and ciprofibrate-fed mice). Oxidative DNA damage was estimated by quantifying 8-hydroxydeoxyguanosine (8-OHdG) by high-performance liquid chromatography/electrochemical detection. Ciprofibrate treatment significantly increased hepatic 8-OHdG concentrations, in agreement with several previous studies, but catalase overexpression did not significantly affect them, although 8-OHdG concentrations were decreased 50% in untreated mice. These results imply that the metabolism of hydrogen peroxide by catalase is not an important factor in the development of hepatic lipid peroxidation. The decrease in hepatic 8-OHdG in untreated transgenic mice and the increase seen after ciprofibrate administration imply that hydrogen peroxide is important in the formation of 8-OHdG. While the lack of decreased 8-OHdG levels in ciprofibrate-treated transgenic mice does not support this conclusion, it is possible that catalase levels were not sufficiently high to affect this endpoint. Transgenic mice with higher hepatic catalase activities may be required to resolve this issue.

Down regulation of epidermal growth factor receptors in rat hepatocytes treated with clofibric acid.

The effect of clofibric acid (CA), a peroxisome proliferator and a non-genotoxic hepatocarcinogen was investigated on epidermal growth factor (EGF) receptors in hepatocytes of female Sprague-Dawley rats treated at a dose of 9000 ppm in a diet for up to 13 weeks. Hepatocyte plasma membranes were isolated in Weeks 1 and 13, and assayed with [125I]EGF. The binding of EGF to the hepatocyte plasma membranes was reduced in Week 1 as a result of decreased number of low-affinity receptors. The fall of binding capacity was further evident in Week 13, which was associated with decreased numbers of both high- and low-affinity receptors. The equilibrium dissociation constant remained unchanged either in Week 1 or 13. These results were in agreement with previous observations of a decreased hepatocyte response to mitogens after prolonged treatment with CA. This suggested that the CA-associated liver tumor promoting effect is related to its ability to decrease the number of EGF receptors and the resultant aberrant growth environment.

The effect of deferoxamine on ciprofibrate-induced hepatocarcinogenesis in the rat.

BACKGROUND: Peroxisome proliferators (PP) are proven hepatocarcinogens in rats and mice. The carcinogenic effect of PP has been attributed to the oxidative stress that results from generation of high levels of hydrogen peroxide (H2O2). Since the hydroxyl radical is produced via metal mediated reaction from H2O2 and is DNA reactive, we have examined the effect of deferoxamine, the specific iron chelator, on ciprofibrate-induced hepatocarcinogenesis. MATERIALS AND METHODS: Male F-344 rats were fed a diet containing ciprofibrate (0.025%) alone or ciprofibrate plus deferoxamine (0.3% or 0.6%) for 60 to 61 weeks, and the livers were analyzed for the incidence, number and size of the tumors. RESULTS: One hundred percent of rats in all groups developed neoplastic nodules and hepatocellular carcinomas. However, in rats given a higher dose of deferoxamine there was a significant decrease in the number of tumors per liver and the number of tumors larger than 10mm. CONCLUSIONS: Although deferoxamine did not prevent tumor development, at the higher dose level it caused a decrease in the number of tumors. These findings indicate that the decreased tumor numbers maybe due to a reduction in the level of hydroxyl radicals.

Altered hepatic eicosanoid concentrations in rats treated with the peroxisome proliferators ciprofibrate and perfluorodecanoic acid.

Several hypolipidemic drugs, plasticizers, and other chemicals induce hepatic peroxisome proliferation and hepatocellular carcinomas in rodents. These agents induce and promote hepatocarcinogenesis by unknown mechanisms, since most studies have not found them to be genotoxic. Peroxisome proliferators increase the expression of several genes, including those for the enzymes of the peroxisomal beta-oxidation pathway and the cytochrome P-450 4A family, which metabolize lipids, including eicosanoids and their precursor fatty acids. The peroxisome proliferators ciprofibrate and perfluorodecanoic acid (PFDA) were therefore examined for their ability to alter hepatic eicosanoid concentrations. Rats received injections of 3 or 10 mg PFDA/kg body weight every 14 days or were fed 0.01% ciprofibrate for 10 days, 24 days, 6 weeks, 26 weeks, or 54 weeks. The activity of the peroxisomal enzyme fatty acyl CoA oxidase was significantly increased by both ciprofibrate and PFDA at all times. Hepatic concentrations of prostaglandins E2 and F2a (PGE2, PGF2a), thromboxane B2 (TXB2), and leukotriene C4 (LTC4) were measured by immunoassay. Concentrations of PGE2, PGF2a, and TXB2 were decreased in livers of rats receiving ciprofibrate or PFDA compared to livers of control rats, with ciprofibrate exerting a greater effect than PFDA at the doses used. Hepatic LTC4 concentrations were significantly increased by ciprofibrate at 10 days and PFDA at 54 weeks, and significantly decreased by PFDA at 26 weeks. These alterations in eicosanoid concentrations may be important in the natural history of peroxisome proliferator-induced hepatocarcinogenesis.

[Regression of hard exudates in diabetic background retinopathy in therapy with etofibrate antilipemic agent]. / Rückbildung harter Exsudate bei diabetischer Hintergrundretinopathie unter Therapie mit dem Lipidsenker Etofibrat.

BACKGROUND: The aim of this pilot study was to investigate the influence of a lipid lowering therapy with etofibrate on the progression of diabetic background retinopathy in patients with diabetes mellitus and combined hyperlipoproteinemia. In addition to the well known correlation between the duration of diabetes and the quality of blood glucose control, a correlation between diabetic microangiopathy and elevated triglyceride levels is discussed for many years. The most important pathogenic mechanisms in this respect seem to be an elevation of blood viscosity and alterations in the fibrinolytic system. Fibrinogen and triglycerides are the main determinants of plasma viscosity. As lipid lowering drugs containing fibrates and nicotinic acid are able to lower triglycerides and fibrinogen effectively, a favourable therapeutic effect on the progression of diabetic retinopathy may be expected. PATIENTS AND METHOD: 11 type II diabetics with combined hyperlipoproteinemia (Fredrickson type IIb) and mild to moderate background retinopathy detected by fundus photography were treated with etofibrate (2 x 500 mg/day) for a period of 6 months. RESULTS: In 7 of 10 patients hard exudates, which had been present at the beginning of treatment, showed clear regression at the end of the treatment period. Among the laboratory test parameters a significant 30% reduction of triglycerides (p < 0.010) was observed. There was also a clear 25% increase in HDL cholesterol and a 12% fibrinogen reduction. Considerable changes of the quality of blood glucose control were not evident during the treatment period. CONCLUSION: Treatment with the lipid lowering drug etofibrate seems to produce favourable therapeutic effects on hard exudates in diabetic background retinopathy in patients with diabetes mellitus and combined hyperlipoproteinemia. The mechanisms of this effect are not yet clearly understood, in addition to positive effects on the microcirculation of the retina by lowering blood viscosity there is a direct lipolytic effect in the area of hard exudates to be discussed, too. It is important to point out that we did not see any positive effect of etofibrate therapy concerning other morphological changes of diabetic background retinopathy, i.e. microaneurysms or hemorrhages in our pilot study.

Effects of chronic treatment with clofibric acid on response of rat hepatocytes to mitogenic stimuli.

Mitoinhibitory effects of clofibric acid (CA) were investigated in rat hepatocytes in vitro and in vivo. Female Sprague-Dawley rats, 11 weeks of age, were dietetically treated with CA at 9000 ppm for up to 13 weeks. In the in vitro study, hepatocytes were isolated from rats on day 4 and in weeks 1, 2, 5, 9 and 13, and cultured for 48 h in a medium containing epidermal growth factor. Over the last 24 h, bromodeoxyuridine (BrdU) was added to the medium to determine number of hepatocytes in S-phase. The labeling index (LI) of CA-treated hepatocytes in culture was below control values as early as day 4, and progressively declined with increasing treatment period. In the in vivo study, rats were 2/3 partially hepatectomized at week 13 and maintained for 24 h. BrdU was injected intraperitoneally 1 h prior to necropsy. The LI in the CA-treated liver was also decreased. These data indicated that continuous treatment of CA resulted in decreases in hepatocyte response to growth stimuli, and suggested a possible relation between the chronic growth inhibitory effect on cell multiplication and tumor promotion in rat hepatocarcinogenesis.

Coordinate induction of acyl-CoA binding protein, fatty acid binding protein and peroxisomal beta-oxidation by peroxisome proliferators.

Acyl-CoA binding protein (ACBP) and fatty acid binding protein (FABP) are important intracellular lipid binding proteins. The purpose of the present experiments was to test the hypothesis that peroxisome proliferators induce ACBP in rat hepatocytes as has been shown previously for FABP. The effects of two structurally dissimilar peroxisome proliferators perfluorodecanoic acid (PFDA) and clofibric acid (CPIB) were examined in primary rat hepatocyte cultures in a chemically defined media. Both compounds alter lipid metabolism in primary rat hepatocytes in a similar fashion, although PFDA is more potent than CPIB at inducing peroxisomal beta-oxidation. In addition, PFDA and CPIB compete with long-chain fatty acids for binding to FABP but do not compete with long-chain acyl-CoA esters for binding to ACBP. The concentration of ACBP and FABP was increased in peroxisome proliferator-treated hepatocytes relative to vehicle controls within 48 h of treatment. Evidence is given to support increases in ACBP and FABP mRNA being the cause of the increased protein levels by peroxisome proliferators. In addition, the peroxisome proliferators PFDA, perfluorooctanoic acid and ciprofibrate induced hepatic ACBP following in vivo administration to rats indicating that this phenomena is not exclusive to in vitro systems. Therefore, ACBP appears to be a member of the peroxisome proliferator loci, a group of lipid metabolizing proteins, including FABP, which are regulated by peroxisome proliferators such as fibric acids and perfluorinated fatty acids.

Effects of joint exposures to selected peroxisome proliferators on hepatic acyl-CoA oxidase activity in male B6C3F1 mice.

The interaction potential of peroxisome proliferators of similar and dissimilar structure was examined in B6C3F1 mice. Mice were fed diets containing varying concentrations of ciprofibrate (Cipro), clofibrate (Clof) or di(2-ethylhexyl)phthalate (DEHP), or combinations of Cipro and Clof or Cipro and DEHP for 4 d. Induction of peroxisomal beta-oxidation, measured by increased acyl-CoA oxidase activity, was used as the endpoint for analysis. An additive response occurred following joint exposure to the structurally related compounds Cipro and Clof, whereas a possible synergistic response occurred at low dose combinations of the structurally dissimilar Cipro and DEHP. These findings represent the first report assessing the in-vivo interaction potential of structurally similar and dissimilar peroxisome proliferators and provides insight into the dose-response nature of joint exposures to certain non-genotoxic carcinogens.