Improvement of glucose tolerance by bezafibrate in non-obese patients with hyperlipidemia and impaired glucose tolerance

Assessing the structural stability and drug encapsulation efficiency of poly(ethylene glycol)-poly(L-lactic acid) nanoparticles loaded with atorvastatin calcium: Based on dissipative particle dynamics

Block polymer micelles have been proven highly biocompatible and effective in improving drug utilization for delivering atorvastatin calcium. Therefore, it is of great significance to measure the stability of drug-loading nano micelles from the perspective of block polymer molecular sequence design, which would provide theoretical guidance for subsequent clinical applications. This study aims to investigate the structural stability of drug-loading micelles formed by two diblock/triblock polymers with various block sequences through coarse-grained dissipative particle dynamics (DPD) simulations. From the perspectives of the binding strength of poly(L-lactic acid) (PLLA) and polyethylene glycol (PEG) in nanoparticles, hydrophilic bead surface coverage, and the morphological alteration of nanoparticles induced by shear force, the ratio of hydrophilic/hydrophobic sequence length has been observed to affect the stability of nanoparticles. We have found that for diblock polymers, PEG3kda-PLLA2kda has the best stability (corresponding hydrophilic coverage ratio is 0.832), while PEG4kda-PLLA5kda has the worst (coverage ratio 0.578). For triblock polymers, PEG4kda-PLLA2kda-PEG4kda has the best stability (0.838), while PEG4kda-PLLA5kda-PEG4kda possesses the worst performance (0.731), and the average performance on stability is better than nanoparticles composed of diblock polymers.

Prevention of Elevation in Plasma Triacylglycerol with High-Dose Bezafibrate Treatment Abolishes Insulin Resistance and Attenuates Glucose Intolerance Induced by Short-Term Treatment with Dexamethasone in Rats

OBJECTIVE

Fibrates are used as lipid-lowering drugs and are well tolerated as cotreatments when glucose metabolism disturbances are also present. Synthetic glucocorticoids (GCs) are diabetogenic drugs that cause dyslipidemia, dysglycemia, glucose intolerance, and insulin resistance when in excess. Thus, we aimed to describe the potential of bezafibrate in preventing or attenuating the adverse effects of GCs on glucose and lipid homeostasis.

METHODS

Male Wistar rats were treated with high-dose bezafibrate (300 mg/kg, body mass (b.m.)) daily for 28 consecutive days. In the last five days, the rats were also treated with dexamethasone (1 mg/kg, b.m.).

RESULTS

Dexamethasone treatment reduced the body mass gain and food intake, and bezafibrate treatment exerted no impact on these parameters. GC treatment caused an augmentation in fasting and fed glycemia, plasma triacylglycerol and nonesterified fatty acids, and insulinemia, and bezafibrate treatment completely prevented the elevation in plasma triacylglycerol and attenuated all other parameters. Insulin resistance and glucose intolerance induced by GC treatment were abolished and attenuated, respectively, by bezafibrate treatment.

CONCLUSION

High-dose bezafibrate treatment prevents the increase in plasma triacylglycerol and the development of insulin resistance and attenuates glucose intolerance in rats caused by GC treatment, indicating the involvement of dyslipidemia in the GC-induced insulin resistance.

Bezafibrate maintenance therapy in patients with advanced chronic hepatitis C

BACKGROUND

Bezafibrate exerts multiple effects on lipid metabolism by activating the peroxisome proliferator-activated receptor-α, which modulates the expression of key genes of lipid transport, lipoprotein metabolism as well as inflammation. The aim of the present study was to assess the efficacy and safety of bezafibrate in patients with advanced chronic hepatitis C.

MATERIALS AND METHODS

A total of 34 patients received oral bezafibrate treatment (400 mg/day) on the basis of a prospective observational open-label study design. Clinical, biochemical and virological data were evaluated during a mean treatment duration of 19 months. In a subpopulation (n=8), cytokine expression analysis was carried out and compared with an hepatitis C virus treatment-naive control group (n=7).

RESULTS

A significant improvement in aspartate aminotransferase (P=0.007), alanine aminotransferase (P<0.0001), alkaline phosphatase (P=0.001), γ-glutamyltranspeptidase levels (P=0.001) and aspartate aminotransferase-to-platelets ratio index Score (P=0.026) could be found at the end of observation. No significant effect on viral load was observed. Bezafibrate treatment for at least 4 months markedly increased interferon-γ expression compared with the treatment-naive patients (4.81 vs. 1.63 arbitrary units; P=0.005), whereas tumour necrosis factor-α and interleukin-6 levels were not significantly influenced.

CONCLUSION

This observational study provides evidence that bezafibrate is effective for patients with advanced chronic hepatitis C by reducing liver enzymes significantly and should be further evaluated as a potentially beneficial maintenance therapy.

Fibric acid derivatives in cardiovascular disease prevention: results from the large clinical trials

PURPOSE OF REVIEW

Results from five large placebo-controlled trials with second-generation fibrates have shown varying success in reducing cardiovascular events. This review focuses on a number of extended analyses from these trials that may relate to the success or failure of fibrate therapy and indicate who might likely benefit from this therapy.

RECENT FINDINGS

Results have been far from uniform and several trials have been adversely impacted by high off-trial statin use. Collective evidence suggests, however, that fibrates have optimum cardiovascular benefit in diabetes or other manifestations of insulin resistance. Much of this evidence comes from posttrial analysis in subgroups with more sharply defined clinical characteristics than in the overall trial population. Analyses also suggest that different fibrates have a different range of favorable clinical properties, that the cardiovascular benefit of fibrates may not be readily measured or mostly predicted by changes in traditional lipid measurements, and that other nonlipid properties of fibrates as peroxisome proliferator-activated receptor agents might explain some of the benefit of these drugs.

SUMMARY

Results of major clinical endpoint trials with fibrates, although not uniformly positive, provide substantial evidence for a selective therapeutic role of these drugs in cardiovascular event reduction in diabetes or insulin resistance.

The effect of high-dose simvastatin on free fatty acid metabolism in patients with type 2 diabetes mellitus

Statins improve all major lipid fractions, reduce coronary heart disease risk, and may have a minor effect on glucose tolerance. A reduction in free fatty acid flux and concentrations could be partly responsible for these effects. We measured nocturnal and postprandial plasma palmitate concentrations and rate of appearance (R(a)) on 2 occasions in 12 obese dyslipidemic subjects with type 2 diabetes mellitus, using a single-blind, crossover format (placebo followed by simvastatin, 80 mg/d), and also on 1 occasion in 6 untreated control subjects. The diabetic subjects had increased average nocturnal (127+/-13 vs 80+/-10 micromol/L, P<.05) and 2-hour postprandial (49+/-6 vs 17+/-2 micromol/L, P<.001) palmitate concentrations, as well as increased nocturnal (31.6+/-3.7 vs 19.5+/-3.7 mmol/m(2) over 9 hours, P<.05) and postprandial (11.5+/-3.7 vs 5.5+/-3.7 mmol/m(2) every 4 hours, P<.005) integrated palmitate R(a) compared to normal controls. High-dose simvastatin reduced serum triglycerides by 35% but had no effect on plasma palmitate concentrations or R(a). These results suggest that the triglyceride-lowering effect of statins is not mediated through an effect on FFA metabolism.

The "Statinth" wonder of the world: a panacea for all illnesses or a bubble about to burst

After the introduction of statins in the market as effective lipid lowering agents, they were shown to have effects other than lipid lowering. These actions were collectively referred to as 'pleiotropic actions of statins.' Pleiotropism of statins formed the basis for evaluating statins for several indications other than lipid lowering. Evidence both in favour and against is available for several of these indications. The current review attempts to critically summarise the available data for each of these indications.

Bezafibrate on lipids and glucose metabolism in obese diabetic Otsuka Long-Evans Tokushima fatty rats

Type 2 diabetes is caused by insulin resistance and beta-cell dysfunction. The Otsuka Long-Evans Tokushima Fatty (OLETF) rat is an established animal model of human type 2 diabetes that exhibits chronic and slowly progressive hyperglycemia and hyperlipidemia and is accompanied by progressive fibrosis in the islets. The aim of the present study was to examine whether worsening of hyperglycemia, insulin resistance, and histologic alterations of the islets in OLETF rats is related to hyperlipidemia by treating these animals with a lipid-lowering drug, bezafibrate. The bezafibrate-treated groups of OLETF and their control counterpart Long-Evans Tokushima Otsuka (LETO) rats received a bezafibrate-rich diet (150 mg/100 g normal chow) for 16 weeks, from 12 to 28 weeks of age, while the other groups of rats received standard rat chow. Bezafibrate treatment significantly reduced serum triglyceride (TG) and free fatty acid (FFA) levels, suppressed the increase in islet size, and inhibited the expression of alpha-smooth muscle actin, a marker for activated pancreatic stellate cells that are involved in the fibrosis of the pancreas, in the islets in OLETF rats, but had no influences on food intake, body weight gain, abdominal adipose depots, and pancreatic insulin content in both strains of rats. Although bezafibrate significantly reduced circulating lipid levels and suppressed the increase in insulin secretion evaluated by area under the curve (AUC) analysis in response to an intravenous glucose tolerance test (IVGTT) until the end of the experiment, improvement of insulin resistance was observed only for the first 8 weeks after the onset of bezafibrate treatment. These results suggest that dyslipidemia is not responsible for the reduced insulin sensitivity, but the impairment of glucose tolerance is the primary defect in the OLETF rats, although improvement of dyslipidemia suppressed histologic alterations in the islets and temporally improved insulin resistance.

No effect of simvastatin treatment on insulin sensitivity in patients with primary hypercholesterolemia

OBJECTIVE

Statins, in addition to cholesterol lowering, have nonlipid effects on formation and progression of atheromatous plaque. Insulin resistance and hyperinsulinemia may have detrimental influences on the arterial wall. Statins (may also) inhibit insulin signal transferring in vascular smooth cell cultures. However, their effect on insulin sensitivity remains controversial. Therefore, we decided to investigate the effect of simvastatin on insulin sensitivity in hypercholesterolemic patients.

PATIENTS AND METHODS

Eighteen patients with primary hypercholesterolemia were divided into simvastatin group (n = 9; 4 females, 5 males; BMI 30.6 +/- 4 kg/m2; mean ages 57 +/- 6 years) and placebo group (n = 9; 4 females, 5 males; BMI 28 +/- 2.9 kg/m2; mean ages 49 +/- 10 years). Simvastatin (20 mg/day) or placebo were given for 2 months. Total and HDL cholesterol were measured and LDL cholesterol was calculated by Friedewald formula. Insulin sensitivity was determined by using euglycemic hyperinsulinemic clamp technique [40 microU/m2/min insulin infusion rate; glucose disposal rate (M)= mg/kg/min] before and after treatment.

RESULTS

Plasma levels of total, LDL and HDL cholesterol decreased significantly in simvastatin group after treatment (p = 0.000, p = 0.000, and p = 0.048, respectively). Plasma levels of total cholesterol decreased significantly (p = 0.032), whereas LDL and HDL levels remained unchanged in placebo group. M value (mg/kg/min) decreased insignificantly in simvastatin group (4.32 +/- 1.57 vs. 3.71 +/- 1.91) and increased in placebo group (3.55 +/- 1.91 vs. 3.95 +/- 0.95).

CONCLUSION

Short-term simvastatin treatment did not affect insulin sensitivity determined by "gold standard" euglycemic hyperinsulinemic clamp method in hypercholesterolemic patients in this research. Further studies with simvastatin using higher doses and longer duration should be performed.

Therapeutic role of peroxisome proliferator-activated receptors in obesity, diabetes and inflammation

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear receptor family and play a significant role in regulation of lipid metabolism, hepatic peroxisomal enzyme expression, insulin sensitivity and glucose homeostasis. PPARs have been classified into three subtypes encoded by different genes: PPARalpha (NR1C1), PPARdelta (NR1C2), and PPARgamma (NR1C3). Each subtype of PPARs appears to be differently expressed in a tissue-specific manner because of their binding to specific consensus DNA sequences, known as PPREs (peroxisome proliferator response elements). Thus, PPARs have emerged as potential molecular targets for the design and synthesis of a different class of compounds, considering the conformation of receptors for the treatment of human metabolic disorders. This review covers the rapid progress made in functional analysis of PPARs and progress made towards the identification of ligands for each subtype receptor.

Bezafibrate improves hypertension and insulin sensitivity in humans

We examined cellular membrane fatty acid composition and insulin sensitivity in patients with mild essential hypertension and hyperlipidemia, and investigated whether bezafibrate, a lipid-lowering drug, could improve elevated blood pressure and insulin sensitivity in these subjects by ameliorating cellular membrane fatty acid composition. Twenty-seven subjects were recruited. Twelve men with mild essential hypertension [systolic blood pressure (SBP) between 140 mmHg and 160 mmHg] and hypertriglyceridemia (plasma triglyceride concentration over 150 mg/dl) were designated the HL group. Fifteen men with mild essential hypertension and normotriglyceridemia (plasma triglyceride concentration below 150 mg/dl) were designated the NL group. Subjects in the HL group were given bezafibrate 400 mg/dl and those in the NL group were given placebo for 3 months. Bezafibrate significantly reduced SBP (140 +/- 2.6 to 131.8 +/- 2.6 mmHg, mean +/- SEM), diastolic blood pressure (DBP) (87.8 +/- 2.0 to 82.8 +/- 2.6 mmHg), fasting plasma triglyceride concentration (225.5 +/- 23.5 to 102.9 +/- 10.9 mg/dl), fasting plasma insulin concentration (9.6 +/- 0.8 to 7.1 +/- 0.8 microU/ml), and homeostasis model assessment scores (HOMA-R, 2.4 +/- 0.2 to 1.7 +/- 0.2), and significantly improved the insulin sensitivity index (56.0 +/- 3.0 to 70.7 +/- 4.8 mg x l2/mmol x mU x min) in the HL group. Regarding erythrocyte membrane fatty acid composition, bezafibrate reduced the percentages of saturated fatty acids (SFA) and increased the percentage of polyunsaturated fatty acids (PUFA). Plasma triglyceride concentrations were positively correlated with HOMA-R (r = 0.50, p < 0.01) and SFA (r = 0.39, p < 0.05), and negatively correlated with PUFA (r = -0.45, p < 0.05) before administration of placebo or bezafibrate. In conclusion, an improvement of hyperlipidemia by bezafibrate may be attributed to reduction of blood pressure and amelioration of insulin sensitivity. Abnormalities in membrane lipid composition may play an important role in these metabolic disorders.

Novel tricyclic-alpha-alkyloxyphenylpropionic acids: dual PPARalpha/gamma agonists with hypolipidemic and antidiabetic activity

Synthesis and structure-activity relationships of tricyclic alpha-ethoxy-phenylpropionic acid derivatives guided by in vitro PPARalpha and PPARgamma transactivation data and computer modeling led to the identification of the novel carbazole analogue, 3q, with dual PPARalpha (EC(50) = 0.36 microM) and PPARgamma (EC(50) = 0.17 microM) activity in vitro. Ten days treatment of db/db mice with 3q improved the insulin sensitivity, as measured by OGTT, better than that seen with both pioglitazone and rosiglitazone treatment, suggesting in vivo PPARgamma activity. Likewise, 3q lowered plasma triglycerides and cholesterol in high cholesterol fed rats after 4 days treatment, indicating in vivo PPARalpha activity. Investigations of the pharmacokinetics of selected compounds suggested that extended drug exposure improved the in vivo activity of in vitro active compounds.

Bezafibrate reduces mRNA levels of adipocyte markers and increases fatty acid oxidation in primary culture of adipocytes

The molecular mechanisms by which peroxisome proliferator-activated receptor (PPAR) activation by fibrates reduces fat deposition and improves insulin sensitivity are not completely understood. We report that exposure of a rat primary culture of adipocytes for 24 h to the PPAR activator bezafibrate increased the mRNA levels of crucial genes involved in peroxisomal and mitochondrial beta-oxidation. The mRNA levels of the peroxisomal beta-oxidation rate-limiting enzyme acyl-CoA oxidase and of the muscle-type carnitine palmitoyl transferase I (M-CPT-I), which determines the flux of mitochondrial beta-oxidation, increased by 1.6-fold (P < 0.02) and 4.5-fold (P = 0.001), respectively. These changes were accompanied by an increase in the transcript levels of the uncoupling protein-2 (UCP-2; 1.5-fold induction; P < 0.05) and UCP-3 (3.7-fold induction; P < 0.001), mitochondrial proteins that reduce ATP yield and may facilitate the oxidation of fatty acids. Furthermore, bezafibrate increased the mRNA levels of the fatty acid translocase (2-fold induction; P < 0.01), suggesting a higher fatty acid uptake into adipocytes. In agreement with these changes, bezafibrate caused a 1.9-fold induction (P < 0.02) in 9,10-[(3)H]palmitate oxidation. Moreover, bezafibrate reduced the mRNA expression of several adipocyte markers, including PPARgamma (30% reduction; P = 0.05), tumor necrosis factor-alpha (33% reduction; P < 0.05), and the ob gene (26% reduction). In contrast, adipocyte fatty acid binding protein mRNA levels increased (1.5-fold induction; P < 0.01), pointing to a mobilization of fatty acids to mitochondria and peroxisomes. The reduction of the adipocyte markers caused by bezafibrate was accompanied by an increase in the mRNA levels of the preadipocyte marker Pref-1 (1.6-fold induction; P < 0.01). Some of the changes observed in the primary culture of rat adipocytes also were studied in the epididymal white adipose tissue of bezafibrate-treated rats for 7 days. In vivo, M-CPT-I mRNA levels increased (4.5-fold induction; P = 0.001) in epididymal white adipose tissue of bezafibrate-treated rats. Similarly, fatty acid translocase (2.6-fold induction; P = 0.002) and Pref-1 (5.6-fold induction) mRNA levels increased, although differences in the latter were not significant because of huge individual variations. These results indicate that exposure of adipocytes to bezafibrate, independent of its hepatic effects, increases the degradation of fatty acids, reducing their availability to synthesize triglycerides. As a result, some degree of dedifferentiation of adipocytes to preadipocyte-like cells is achieved. These changes may be involved in the reduction in fat depots and in the improvement of insulin sensitivity observed after bezafibrate treatment.

Treating dyslipidaemia in non-insulin-dependent diabetes mellitus -- a special reference to statins

Patients with non-insulin-dependent diabetes (NIDDM) have an increased incidence of ischaemic heart disease (IHD) when compared with nondiabetic subjects. In addition, they have a worse prognosis after their first myocardial infarction (MI). According to the recent USA recommendations, the threshold for initiation of dietary intervention in diabetic subjects is an LDL greater than 2.6 mmol/l, with the goal to achieve levels less than 2.6 mmol/l (100 mg/dl). This is also the threshold for initiation and treatment goal for pharmacological intervention in diabetic subjects, unless they are completely free of IHD, peripheral vascular disease or cerebrovascular disease and have no other IHD risk factors. In the latter circumstances, the threshold for treatment is an LDL greater than 3.38 mmol/l (130 mg/dl), with the goal to achieve levels less than 3.38 mmol/l. The HMG-CoA reductase inhibitors (statins) can improve the lipid profile effectively and safely in NIDDM. Results from post hoc analyses of diabetic subgroups in the large intervention trials suggest that some statins significantly reduce the risk for IHD-related mortality/morbidity. However, because these results are derived from secondary prevention trials, we cannot be sure if these benefits apply to all diabetic subjects or only to those who already have IHD. Nevertheless, it seems logical to assume that this benefit also applies to NIDDM patients who do not have IHD because they share a similar vascular risk as nondiabetic subjects who have IHD. Intervention trials using statins and fibrates, alone or in combination, in NIDDM are under way. In a few years these trials will provide definitive end-point-based evidence in this high-risk group of patients.

Peroxisome proliferator-activated receptor alpha activators improve insulin sensitivity and reduce adiposity

Fibrates and glitazones are two classes of drugs currently used in the treatment of dyslipidemia and insulin resistance (IR), respectively. Whereas glitazones are insulin sensitizers acting via activation of the peroxisome proliferator-activated receptor (PPAR) gamma subtype, fibrates exert their lipid-lowering activity via PPARalpha. To determine whether PPARalpha activators also improve insulin sensitivity, we measured the capacity of three PPARalpha-selective agonists, fenofibrate, ciprofibrate, and the new compound GW9578, in two rodent models of high fat diet-induced (C57BL/6 mice) or genetic (obese Zucker rats) IR. At doses yielding serum concentrations shown to activate selectively PPARalpha, these compounds markedly lowered hyperinsulinemia and, when present, hyperglycemia in both animal models. This effect relied on the improvement of insulin action on glucose utilization, as indicated by a lower insulin peak in response to intraperitoneal glucose in ciprofibrate-treated IR obese Zucker rats. In addition, fenofibrate treatment prevented high fat diet-induced increase of body weight and adipose tissue mass without influencing caloric intake. The specificity for PPARalpha activation in vivo was demonstrated by marked alterations in the expression of PPARalpha target genes, whereas PPARgamma target gene mRNA levels did not change in treated animals. These results indicate that compounds with a selective PPARalpha activation profile reduce insulin resistance without having adverse effects on body weight and adipose tissue mass in animal models of IR.

Uncoupling protein-3 mRNA levels are increased in white adipose tissue and skeletal muscle of bezafibrate-treated rats

Fibrates are hypolipidemic drugs that are also able to improve glucose tolerance in animals and diabetic patients through an unknown mechanism. Since uncoupling proteins (UCP) seem to play an important role in the pathogenesis of non-insulin-dependent diabetes mellitus (NIDDM), we examined whether treatment of rats with bezafibrate for 3, 7, or 15 days modified UCP mRNA levels. Using RT-PCR, we observed a weak ectopic expression of UCP-1 and a 2-fold increase in UCP-3 mRNA levels in white adipose tissue after 7 and 15 days of treatment. Moreover, bezafibrate administration caused a 1. 7-fold induction in UCP-3 mRNA levels in skeletal muscle on day 7. Since UCP-3 mRNA levels are reduced in skeletal muscle of diabetic patients, this effect may be involved in the improvement of insulin sensitivity caused by bezafibrate in NIDDM.

Statin + fibrate combination therapy fluvastatin with bezafibrate or ciprofibrate in high risk patients with vascular disease

We evaluated the use of combination therapy (ciprofibrate 100 mg or bezafibrate 400 mg plus fluvastatin 40 mg) in 23 patients (n = 13 in the ciprofibrate group) with established cardiovascular disease. Both treatments achieved a significant (P< or =0.01) decrease in the total cholesterol (TC) (32 and 21%), triglycerides (TG) (53 and 46%) and low-density lipoprotein (LDL) (36 and 26%) levels and the TC/high-density lipoprotein (HDL) (42 and 31%) and LDL/HDL (46 and 35%) ratios. HDL levels were increased (19% for both treatment groups), but this rise only achieved significance (P=0.01) in the ciprofibrate group. Although the two patient groups were not strictly matched, the reduction in serum TC and LDL levels was greater with ciprofibrate (32 and 36%, respectively; P< or =0.001) than with bezafibrate (21 and 26%, respectively; P< or =0.01). There was a significant reduction in plasma fibrinogen levels (36.4 and 13.5% in the ciprofibrate and bezafibrate group, respectively). None of the patients reported myalgia or had abnormal creatine kinase activity or liver function tests. Combination therapy is worth considering in high-risk patients because of the advantages associated with this option. Combination therapy is competitively priced when compared with high doses of statins. An end-point-based trial is needed.

Novel peroxisome proliferator-activated receptor (PPAR) gamma and PPARdelta ligands produce distinct biological effects

The peroxisome proliferator-activated receptors (PPARs) include three receptor subtypes encoded by separate genes: PPARalpha, PPARdelta, and PPARgamma. PPARgamma has been implicated as a mediator of adipocyte differentiation and the mechanism by which thiazolidinedione drugs exert in vivo insulin sensitization. Here we characterized novel, non-thiazolidinedione agonists for PPARgamma and PPARdelta that were identified by radioligand binding assays. In transient transactivation assays these ligands were agonists of the receptors to which they bind. Protease protection studies showed that ligand binding produced specific alterations in receptor conformation. Both PPARgamma and PPARdelta directly interacted with a nuclear receptor co-activator (CREB-binding protein) in an agonist-dependent manner. Only the PPARgamma agonists were able to promote differentiation of 3T3-L1 preadipocytes. In diabetic db/db mice all PPARgamma agonists were orally active insulin-sensitizing agents producing reductions of elevated plasma glucose and triglyceride concentrations. In contrast, selective in vivo activation of PPARdelta did not significantly affect these parameters. In vivo PPARalpha activation with WY-14653 resulted in reductions in elevated triglyceride levels with minimal effect on hyperglycemia. We conclude that: 1) synthetic non-thiazolidinediones can serve as ligands of PPARgamma and PPARdelta; 2) ligand-dependent activation of PPARdelta involves an apparent conformational change and association of the receptor ligand binding domain with CREB-binding protein; 3) PPARgamma activation (but not PPARdelta or PPARalpha activation) is sufficient to potentiate preadipocyte differentiation; 4) non-thiazolidinedione PPARgamma agonists improve hyperglycemia and hypertriglyceridemia in vivo; 5) although PPARalpha activation is sufficient to affect triglyceride metabolism, PPARdelta activation does not appear to modulate glucose or triglyceride levels.

Bezafibrate has an antioxidant effect: peroxisome proliferator-activated receptor alpha is associated with Cu2+, Zn2+-superoxide dismutase in the liver

Administration of bezafibrate in rats significantly reduced the levels of plasma thiobarbituric acid-reactive substances (TBARS) in comparison with those obtained in rats fed a soy or lard chow. Moreover, an elevation of in vitro conjugated diene production and linoleic acid levels in the high-density lipoproteins and low-density lipoproteins induced by a soy or lard chow, was reduced by bezafibrate administration. In addition, the liver Cu2+, Zn2+-superoxide dismutase (SOD) gene expression showed a significant positive correlation with the liver peroxisome proliferator-activated receptor alpha (PPARalpha) mRNA level (R=0.769, p<0.0001). This unique characteristic of bezafibrate, which possesses both a hypolipidemic effect and antioxidant activity, may be beneficial in preventing vascular complications in hyperlipidemia.

Effect of troglitazone (CS-045) and bezafibrate on glucose tolerance, liver glycogen synthase activity, and beta-oxidation in fructose-fed rats

To clarify the relationship between lipid and glucose metabolism abnormalities in fructose-fed rats, we examined whether an improvement of insulin sensitivity by troglitazone (CS-045) or a decrease in plasma lipids by bezafibrate affects the relationship between serum levels of lipid and glucose. In addition, we also examined changes in liver glycogen metabolism and beta-oxidation in fructose-fed rats. Troglitazone ameliorated fasting hyperlipidemia, hyperglycemia, and hyperinsulinemia. In addition, it augmented glycogen synthase activity by 53%, and decreased the mitochondrial palmitic acid beta-oxidation rate and ketone body production rate by 27% and 55%, respectively. However, hyperglycemia and liver glycogen synthase activity were not improved by bezafibrate treatment despite a marked reduction of serum triglyceride (TG) levels resulting from a 1.76-fold increase in mitochondrial oxidation and a 2.04-fold increase in hepatic ketone body production. These results suggest that abnormalities in glucose and lipid metabolism in fructose-fed rats, which are ameliorated by troglitazone, may be closely linked to reduced glycogen synthase activity in the liver.