Effects of gemfibrozil on insulin sensitivity and on haemostatic variables in hypertriglyceridemic patients

The Interplay between Non-Esterified Fatty Acids and Plasma Zinc and Its Influence on Thrombotic Risk in Obesity and Type 2 Diabetes

Thrombosis is a major comorbidity of obesity and type-2 diabetes mellitus (T2DM). Despite the development of numerous effective treatments and preventative strategies to address thrombotic disease in such individuals, the incidence of thrombotic complications remains high. This suggests that not all the pathophysiological mechanisms underlying these events have been identified or targeted. Non-esterified fatty acids (NEFAs) are increasingly regarded as a nexus between obesity, insulin resistance, and vascular disease. Notably, plasma NEFA levels are consistently elevated in obesity and T2DM and may impact hemostasis in several ways. A potentially unrecognized route of NEFA-mediated thrombotic activity is their ability to disturb Zn²⁺ speciation in the plasma. Zn²⁺ is a potent regulator of coagulation and its availability in the plasma is monitored carefully through buffering by human serum albumin (HSA). The binding of long-chain NEFAs such as palmitate and stearate, however, trigger a conformational change in HSA that reduces its ability to bind Zn²⁺, thus increasing the ion’s availability to bind and activate coagulation proteins. NEFA-mediated perturbation of HSA-Zn²⁺ binding is thus predicted to contribute to the prothrombotic milieu in obesity and T2DM, representing a novel targetable disease mechanism in these disorders.

Prolonged-release pirfenidone prevents obesity-induced cardiac steatosis and fibrosis in a mouse NASH model

PURPOSE

Obesity is associated with systemic insulin resistance and cardiac hypertrophy with fibrosis. Peroxisome proliferator-activated receptors (PPARs) regulate carbohydrate and lipid metabolism, improving insulin sensitivity, triglyceride levels, inflammation, and oxidative stress. We previously demonstrated that prolonged-release pirfenidone (PR-PFD) is an agonistic ligand for Pparα with anti-inflammatory and anti-fibrotic effects, and might be a promising drug for cardiac diseases-treatment. Here, we investigated the effects of PR-PFD in ventricular tissue of mice with nonalcoholic steatohepatitis (NASH) and obesity induced by high-fat/high-carbohydrate (HFHC) diet.

METHODS

Five male C57BL/6 J mice were fed with normal diet (ND) and ten with HFHC diet for 16 weeks; at 8 weeks of feeding, five mice with HFHC diet were administered PR-PFD (350 mg/kg/day) mixed with HFHC diet.

RESULT

Systemic insulin resistance, heart weight/body weight ratio, myocardial steatosis with inflammatory foci, hypertrophy, and fibrosis were prevented by PR-PFD. In addition, HFHC mice showed significantly increased desmin, Tgfβ1, Timp1, collagen I (Col I), collagen III (Col III), TNF-α, and Nrf2 mRNA levels, including α-SMA, NF-kB, Nrf2, troponin I, Acox1, Cpt1A, and Lxrα protein levels compared with the ND ventricular tissues. Mechanistically, HFHC mice with PR-PFD treatment significantly decreased these genes overexpressed by HFHC diet. Furthermore, PR-PFD overexpressed the Pgc1a mRNA levels and Pparα, Pparγ, Acox1, and Cpt1A protein levels.

CONCLUSIONS

The results suggest that PR-PFD could be a promising drug for the prevention and treatment of cardiac steatosis and fibrosis induced by obesity.

Changes in Plasma Free Fatty Acids Associated with Type-2 Diabetes

Type 2 diabetes mellitus (T2DM) is associated with increased total plasma free fatty acid (FFA) concentrations and an elevated risk of cardiovascular disease. The exact mechanisms by which the plasma FFA profile of subjects with T2DM changes is unclear, but it is thought that dietary fats and changes to lipid metabolism are likely to contribute. Therefore, establishing the changes in concentrations of specific FFAs in an individual’s plasma is important. Each type of FFA has different effects on physiological processes, including the regulation of lipolysis and lipogenesis in adipose tissue, inflammation, endocrine signalling and the composition and properties of cellular membranes. Alterations in such processes due to altered plasma FFA concentrations/profiles can potentially result in the development of insulin resistance and coagulatory defects. Finally, fibrates and statins, lipid-regulating drugs prescribed to subjects with T2DM, are also thought to exert part of their beneficial effects by impacting on plasma FFA concentrations. Thus, it is also interesting to consider their effects on the concentration of FFAs in plasma. Collectively, we review how FFAs are altered in T2DM and explore the likely downstream physiological and pathological implications of such changes.

Systematization of clinical trials related to treatment of metabolic syndrome, 1980-2015

INTRODUCTION

Despite the clinical, epidemiological, and economic significance of metabolic syndrome, the profile of clinical trials on this disease is unknown.

OBJECTIVE

To characterize the clinical trials related to treatment of metabolic syndrome during the 1980-2015 period.

METHODS

Systematic review of the literature using an ex ante search protocol which followed the phases of the guide Preferred Reporting Items for Systematic Reviews and Meta-Analyses in four multidisciplinary databases with seven search strategies. Reproducibility and methodological quality of the studies were assessed.

RESULTS

One hundred and six trials were included, most from the United States, Italy, and Spain, of which 63.2% evaluated interventions effective for several components of the syndrome such as diet (40.6%) or physical activity (22.6%). Other studies assessed drugs for a single factor such as hypertension (7.5%), hypertriglyceridemia (11.3%), or hyperglycemia (9.4%). Placebo was used as control in 54.7% of trials, and outcome measures included triglycerides (52.8%), HDL (48.1%), glucose (29.2%), BMI (33.0%), blood pressure (27.4%), waist circumference (26.4%), glycated hemoglobin (11.3%), and hip circumference (7.5%).

CONCLUSION

It was shown that studies ob efficacy of treatment for metabolic syndrome are scarce and have mainly been conducted in the last five years and in high-income countries. Trials on interventions that affect three or more factors and assess several outcome measures are few, and lifestyle interventions (diet and physical activity) are highlighted as most important to impact on this multifactorial syndrome.

Comparative risk of severe hypoglycemia among concomitant users of thiazolidinedione antidiabetic agents and antihyperlipidemics

We conducted high-dimensional propensity score-adjusted cohort studies to examine whether thiazolidinedione use with a statin or fibrate was associated with an increased risk of severe hypoglycemia. We found that concomitant therapy with a thiazolidinedione+fibrate was associated with a generally delayed increased risk of severe hypoglycemia.

Severe hypoglycemia in users of sulfonylurea antidiabetic agents and antihyperlipidemics

Drug-drug interactions causing severe hypoglycemia due to antidiabetic drugs is a major clinical and public health problem. We assessed whether sulfonylurea use with a statin or fibrate was associated with severe hypoglycemia. We conducted cohort studies of users of glyburide, glipizide, and glimepiride plus a statin or fibrate within a Medicaid population. The outcome was a validated, diagnosis-based algorithm for severe hypoglycemia. Among 592,872 persons newly exposed to a sulfonylurea+antihyperlipidemic, the incidence of severe hypoglycemia was 5.8/100 person-years. Adjusted hazard ratios (HRs) for sulfonylurea+statins were consistent with no association. Most overall HRs for sulfonylurea+fibrate were elevated, with sulfonylurea-specific adjusted HRs as large as 1.50 (95% confidence interval (CI): 1.24-1.81) for glyburide+gemfibrozil, 1.37 (95% CI: 1.11-1.69) for glipizide+gemfibrozil, and 1.63 (95% CI: 1.29-2.06) for glimepiride+fenofibrate. Concomitant therapy with a sulfonylurea and fibrate is associated with an often delayed increased rate of severe hypoglycemia.

Impact of fibrate therapy on plasma plasminogen activator inhibitor-1: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

The aim of this systematic review was to perform a meta-analysis of randomized controlled trials (RCTs) examining the efficacy of fibrate therapy in reducing plasma concentration or activity of plasminogen activator inhibitor 1 (PAI-1).

METHODS

Scopus and MEDLINE databases were searched (up to October 15, 2014) to identify RCTs investigating whether fibrates lower plasma PAI-1 concentration or activity. A random-effects model and the generic inverse variance method were used for quantitative data synthesis. Sensitivity analyses were conducted using the one-study remove approach. Random-effects meta-regression was performed to assess the impact of potential moderators on the estimated effect sizes.

RESULTS

A total of 14 RCTs examining the effects of gemfibrozil (6 trials), bezafibrate (4 trials), and fenofibrate (5 trials) were included. Meta-analysis suggested that fibrate therapy did not significantly reduce plasma PAI-1 concentration (weighed mean difference [WMD]: -11.39 ng/mL, 95% CI: -26.64, 3.85, p=0.143) or activity (WMD: 2.02 U/mL, 95% CI: -0.87, 4.90, p=0.170). These results remained unchanged after subgroup analysis according to duration of treatment (<12 and ≥12 weeks) and type of fibrate administered (fenofibrate, bezafibrate or gemfibrozil). The estimated effects of fibrate therapy on plasma concentration and activity of PAI-1 were independent of treatment duration and changes in plasma triglyceride levels in the meta-regression analysis.

CONCLUSION

This meta-analysis of RCTs suggested that fibrate therapy does not reduce plasma concentration or activity of PAI-I. The putative benefits of fibrate therapy in patients with cardiovascular disease appear to be exerted via mechanisms independent of effects on PAI-1.

[Rosuvastatin improves insulin sensitivity in overweight rats induced by high fat diet. Role of SIRT1 in adipose tissue]

OBJECTIVE

To study the effects of rosuvastatin on insulin resistance in overweight rats induced by high fat diet, as well as potential mediators.

METHODS

We used male Wistar rats fed with a standard diet (CT) or high fat diet (33.5% fat) (HFD); half of the animals HFD were treated with rosuvastatin (15mg/kg/day) (HFD+Rosu) for 7 weeks.

RESULTS

HFD rats showed increased body, epididymal and lumbar adipose tissue weights. Treatment with Rosu did not modify body weight or the weight of the adipose packages in HFD rat. Plasma glucose and insulin levels and HOMA index were higher in HFD rats, and rosuvastatin treatment reduced them. Leptin/adiponectin ratio in plasma and lumbar adipose tissue were higher in HDF rats, and were reduced by rosuvastatin. SIRT-1, PPAR-γ and GLUT-4 protein expression in lumbar adipose tissue were lower in HFD rats and Rosu normalized expression of the three mediators.

CONCLUSIONS

Rosuvastatin ameliorates insulin sensitivity induced by HFD in rats. This effect is mediated by several mechanisms including reduction of leptin and enhancement of SIRT-1, PPAR-γ and GLUT-4 expression in white adipose tissue. SIRT1 could be considered a major mediator of the beneficial effects of rosuvastatin on insulin sensitivity in overweight rats induced by diet.

Lack of association between peroxisome proliferator-activated receptors alpha and gamma2 polymorphisms and progressive liver damage in patients with non-alcoholic fatty liver disease: a case control study

Background

Peroxisome proliferator-activated receptors (PPARs) play key roles in the pathogenesis of nonalcoholic fatty liver disease (NAFLD).

Aim

to assess the effect of functional single nucleotide polymorphisms (SNPs) of PPARα and PPARγ2, previously associated with insulin resistance and dyslipidemia, on liver damage in NAFLD, whose progression is influenced by metabolic abnormalities and inherited factors.

Methods

The Leu162Val PPARα and Pro12Ala PPARγ2 SNPs were evaluated by restriction analysis. We considered 202 Italian patients with biopsy-proven NAFLD.

Results

The frequency of the evaluated SNPs did not differ between patients and 346 healthy controls. The presence of the PPARα 162Val allele (prevalence 57%), but not of the PPARγ2 12Ala allele (prevalence 18%), was associated with higher insulin resistance (HOMA-IR index 4.71 ± 3.8 vs. 3.58 ± 2.7, p = 0.026), but not with hyperglycemia. The PPARα 162Val and PPARγ2 12Ala alleles were not associated with the severity of steatosis, necroinflammation, or fibrosis.

Conclusions

The presence of the PPARα 162Val allele was associated with insulin resistance, but not with liver damage in NAFLD. Because of the limited power of the present sample, larger studies are needed to exclude a minor effect of the PPARγ2 12Ala allele on necroinflammation/fibrosis in NAFLD.

Gemfibrozil concentrations are significantly decreased in the presence of lopinavir-ritonavir

OBJECTIVE

The objective of this study was to determine the influence of a 2-week course of lopinavir-ritonavir on the pharmacokinetics of the triglyceride-lowering agent, gemfibrozil.

METHODS

The study was conducted as an open label, single-sequence pharmacokinetic study in healthy human volunteers. Gemfibrozil pharmacokinetic parameter values were compared using a Student t test after a single 600-mg dose was administered to healthy volunteers before and after 2 weeks of lopinavir-ritonavir (400/100 mg) twice daily.

RESULTS

Fifteen healthy volunteers (eight males) completed the study. All study drugs were generally well tolerated and no subjects withdrew participation. The geometric mean ratio (90% confidence interval) for gemfibrozil area under the plasma concentration-time curve after 14 days of lopinavir-ritonavir compared with baseline was 0.59 (0.52, 0.67) (P < 0.001). All 15 study subjects experienced a reduction in gemfibrozil area under the plasma concentration-time curve after lopinavir-ritonavir (range, -6% to -74%). The geometric mean ratios for gemfibrozil apparent oral clearance and maximum concentration were 1.69 (1.41, 1.97) and 0.67 (0.49, 0.86) after 14 days of lopinavir-ritonavir versus baseline, respectively (P < 0.0001 and 0.01, respectively). Gemfibrozil elimination half-life did not change after lopinavir-ritonavir administration (P = 0.60).

CONCLUSION

Lopinavir-ritonavir significantly reduced the systemic exposure of gemfibrozil by reducing gemfibrozil absorption. Clinicians treating HIV-infected patients with hypertriglyceridemia should be aware of this drug interaction.

Peroxisome proliferator activated receptor alpha/gamma dual agonist tesaglitazar attenuates diabetic nephropathy in db/db mice

Peroxisome proliferator-activated receptors (PPARs) are nuclear transcription factors and play a central role in insulin sensitivity, lipid metabolism, and inflammation. Both PPARalpha and -gamma are expressed in the kidney, and their agonists exhibit renoprotective effects in type 2 diabetes. In the present studies, we investigated the effect of the PPARalpha/gamma dual agonist tesaglitazar on diabetic nephropathy in type 2 diabetic db/db mice. Treatment of db/db mice with tesaglitazar for 3 months significantly lowered fasting plasma glucose and homeostasis model assessment of insulin resistance levels but had little effect on body weight, adiposity, or cardiac function. Treatment with tesaglitazar was associated with reduced plasma insulin and total triglyceride levels and increased plasma adiponectin levels. Notably, tesaglitazar markedly attenuated albuminuria and significantly lowered glomerulofibrosis, collagen deposition, and transforming growth factor-beta1 expression in renal tissues of db/db mice. In cultured mesangial cells and proximal tubule cells, where both PPARalpha and -gamma were expressed, tesaglitazar treatment abolished high glucose-induced total collagen protein production and type I and IV collagen gene expression. Collectively, tesaglitazar treatment not only improved insulin resistance, glycemic control, and lipid profile but also markedly attenuated albuminuria and renal glomerular fibrosis in db/db mice. These findings support the utility of dual PPARalpha/gamma agonists in treating type 2 diabetes and diabetic nephropathy.

Tesaglitazar, a dual peroxisome proliferator-activated receptor alpha/gamma agonist, improves apolipoprotein levels in non-diabetic subjects with insulin resistance

AIM

To determine the effects of the peroxisome proliferator-activated receptor (PPAR) alpha/gamma agonist tesaglitazar on serum levels of apolipoprotein (apo) A-I, apoB, and apoCIII in non-diabetic insulin-resistant subjects.

METHODS

This randomized, double-blind, multicentre, placebo-controlled trial examined the effect of tesaglitazar (0.1, 0.25, 0.5, and 1mg) once daily for 12 weeks on apolipoprotein levels in 390 abdominally obese subjects with hypertriglyceridaemia.

RESULTS

Tesaglitazar dose-dependently increased serum concentrations of apoA-I (p<0.009) and decreased concentrations of apoB (p<0.0001), the apoB/apoA-I ratio (p<0.0001), and apoCIII (p<0.0001). Similar improvements were observed in all subgroups of subjects, where individuals were grouped according to age, gender, baseline body mass index, serum triglycerides and high-density lipoprotein cholesterol levels. Low-density lipoprotein particle concentrations were also dose-dependently reduced by tesaglitazar (p<0.0001).

CONCLUSION

Although tesaglitazar is no longer in clinical development, these data indicate that dual PPARalpha/gamma agonism may be a useful pharmacological approach to improve the atherogenic dyslipidaemia associated with insulin resistance.

Single nucleotide polymorphisms of the peroxisome proliferator-activated receptor-alpha gene (PPARA) influence the conversion from impaired glucose tolerance to type 2 diabetes: the STOP-NIDDM trial

Peroxisome proliferator-activated receptor (PPAR) alpha, a transcription factor of the nuclear receptor superfamily, regulates fatty acid oxidation. We evaluated the association of single nucleotide polymorphisms (SNPs) of the PPAR-alpha gene (PPARA) with the conversion from impaired glucose tolerance to type 2 diabetes in 767 subjects of the STOP-NIDDM trial in order to investigate the effect of acarbose in comparison with placebo on the prevention of diabetes. In the placebo group, the G (162V) allele of rs1800206 increased the risk for diabetes by 1.9-fold (95% CI 1.05-3.58) and was associated with elevated levels of plasma glucose and insulin. The effect of this allele on the risk of diabetes in the placebo group was enhanced by the simultaneous presence of the risk alleles of the PPAR-gamma2, PPAR-gamma coactivator 1alpha, and hepatic nuclear factor 4alpha genes (odds ratios 2.2, 2.5, and 3.4, respectively). In the acarbose group, subjects carrying the minor G allele of rs4253776 and the CC genotype of rs4253778 of PPARA had a 1.7- and 2.7-fold increased risk for diabetes. Our data indicate that SNPs of PPARA increase the risk of type 2 diabetes alone and in combination with the SNPs of other genes acting closely with PPAR-alpha.

PPARalpha activation elevates blood pressure and does not correct glucocorticoid-induced insulin resistance in humans

Fibrates, activators of the nuclear receptor PPARalpha, improve dyslipidemia, but their effects on insulin resistance and vascular disease are unresolved. To test the hypothesis that PPARalpha activation improves insulin resistance and vascular function, we determined the effects of fenofibrate in healthy adults with insulin resistance induced by short-term glucocorticoid administration. Eighteen normal-weight subjects were studied in four stages: at baseline, after 21 days of fenofibrate (160 mg/day) alone, after 3 days of dexamethasone (8 mg/day) added to fenofibrate, and after 3 days of dexamethasone added to placebo (dexamethasone alone). Dexamethasone alone caused hyperinsulinemia, increased glucose, decreased glucose disposal, and reduced insulin-induced suppression of hepatic glucose production as determined by hyperinsulinemic euglycemic clamp and increased systolic blood pressure as determined by ambulatory monitoring, features associated with an insulin-resistant state. Fenofibrate improved fasting LDL and total cholesterol in the setting of dexamethasone treatment but had no significant effect on levels of insulin or glucose, insulin-stimulated glucose disposal, or insulin suppression of glucose production during clamps, or ambulatory monitored blood pressure. In the absence of dexamethasone, fenofibrate lowered fasting triglycerides and cholesterol but unexpectedly increased systolic blood pressure by ambulatory monitoring. These data suggest that PPARalpha activation in humans does not correct insulin resistance induced by glucocorticoids and may adversely affect blood pressure.

Gemfibrozil decreases atherosclerosis in experimental diabetes in association with a reduction in oxidative stress and inflammation

AIMS/HYPOTHESIS

It is postulated that peroxisome proliferator-activated receptor alpha agonists confer cardiovascular benefits in diabetes, independently of their effects on lipid metabolism. We investigated putative mechanisms responsible for these anti-atherogenic effects in an in vivo model of diabetes-associated atherosclerosis.

MATERIALS AND METHODS

Control and streptozotocin-induced diabetic apolipoprotein-deficient mice received gemfibrozil (100 mg kg(-1) day(-1)) or no treatment for 20 weeks. Aortic plaque deposition was assessed by Sudan IV staining and subsequent en face quantification. Superoxide production was measured using lucigenin-enhanced chemiluminescence. Markers of pathways including inflammation and oxidative stress were measured using real-time RT-PCR.

RESULTS

No significant effect of gemfibrozil was observed on glycated haemoglobin, cholesterol or insulin in diabetic mice. Diabetes was associated with a three-fold increase in plaque area and a significant increase in NADPH-dependent superoxide compared with control mice. Gemfibrozil significantly attenuated plaque area and superoxide production in diabetic mice. In addition, gemfibrozil reduced the expression of the genes encoding the NADPH oxidase subunits p47phox, gp91phox and Rac-1. In addition, gemfibrozil reduced the expression of the genes encoding nuclear factor kappa B (NF-kappaB) subunit, p65, the NF-kappaB-dependent chemokine monocyte chemoattractant protein-1, and tissue factor.

CONCLUSIONS/INTERPRETATIONS

This study demonstrates that gemfibrozil exerts anti-atherogenic actions, independently of changes in cholesterol and glucose metabolism. Such findings emphasise the possible usefulness of fibrates such as gemfibrozil in a setting of atherosclerosis even in the absence of dyslipidaemia.

Fenofibrate: a novel formulation (Triglide) in the treatment of lipid disorders: a review

Cardiovascular disease is the major cause of mortality worldwide and accounts for approximately 40% of all deaths. Dyslipidemia is one of the primary causes of atherosclerosis and effective interventions to correct dyslipidemia should form an integral component of any strategy aimed at preventing cardiovascular disease. Fibrates have played a major role in the treatment of hyperlipidemia for more than two decades. Fenofibrate is one of the most commonly used fibrates worldwide. Since fenofibrate was first introduced in clinical practice, a major drawback has been its low bioavailability when taken under fasting conditions. Insoluble Drug Delivery-Microparticle fenofibrate is a new formulation that has an equivalent extent of absorption under fed or fasting conditions. In this review, we will discuss the clinical pharmacology of fenofibrate, with particular emphasis on this novel formulation, as well as its lipid-modulating and pleiotropic actions. We will also analyze the major trial that evaluated fibrates for primary and secondary prevention of cardiovascular disease, the safety and efficacy profile of fibrate-statin combination treatment, and the current recommendations regarding the use of fibrates in clinical practice.

Type 2 diabetes, dyslipidemia, and vascular risk: rationale and evidence for correcting the lipid imbalance

Type 2 diabetes is an important cardiovascular risk factor. A significant component of the risk associated with type 2 diabetes is thought to be because of its characteristic lipid "triad" profile of raised small dense low-density lipoprotein levels, lowered high-density lipoprotein, and elevated triglycerides (TGs). Trials of statins and fibrates have included substantial numbers of patients with diabetes and indicate that lipid lowering reduces cardiovascular event rates in these patients. However, statins alone do not always address all the lipid abnormalities of diabetes. Fibrates, which have low affinity for peroxisome proliferator-activated receptor alpha (PPARalpha), improve most aspects of the atherogenic dyslipidemia of diabetes. Chronic elevations of free fatty acids (FFA) induce insulin resistance and contribute to the lipid triad of diabetes. Therefore, reducing their levels is likely to ameliorate insulin resistance and improve the lipid triad of diabetes. PPARs are intimately involved in the regulation of FFA: PPARalpha modulation increases FFA catabolism and PPARgamma agonism (eg, by thiazolidinediones) increases TG lipolysis, FFA transport, conversion of FFA to TGs, and safe storage of FFA. Integrating potent PPARalpha and PPARgamma activity may deliver greater improvement of the diabetic dyslipidemic profile and its attendant risks than selective PPAR activation.

Lipid therapy for cardiovascular disease with insulin resistance, diabetes, or the metabolic syndrome

Insulin resistance with the development of diabetes or metabolic syndrome is associated with characteristic lipid abnormalities and an increased likelihood of cardiovascular events. This review examines the rationale and clinical trial evidence for the benefit of lipid drug therapy in the presence of these related high-risk conditions. In particular, the results of the more recent statin trials are discussed and contrasted with evidence from trials with fibrates, which, although fewer in number, appear to show that this particular therapy has selective benefit for the overweight individual with diabetes or features of the metabolic syndrome.

Enantiomeric separation of gemfibrozil chiral analogues by capillary electrophoresis with heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin as chiral selector

The enantiomeric separation of gemfibrozil chiral analogues was performed by capillary zone electrophoresis (CZE). Resolution of the enantiomers was achieved using heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin (TM-beta-CD) as chiral selector dissolved into a buffer solution. In order to optimize the separation conditions, type, pH and concentration of running buffer and chiral selector concentration were varied. For each pH value, the optimum chiral selector concentration that produced the resolution of the isomers was found. The migration order of labile diastereoisomers formed was valued at the optimum experimental conditions by adding a pure optical isomer to the racemic mixture. Data from 1H NMR studies confirmed host-guest interaction between TM-beta-CD and 5-(2,5-dimethylphenoxy)-2-ethylpentanoic acid sodium salt. The hypothesized stoichiometry host:guest was 1:1. An apparent equilibrium constant (Ka) was estimated monitoring the chemical shift variation as a function of TM-beta-CD concentration. Salt effect on complexation equilibrium constant was also investigated.

Peroxisome proliferator-activated receptor (PPAR) activation induces tissue-specific effects on fatty acid uptake and metabolism in vivo--a study using the novel PPARalpha/gamma agonist tesaglitazar

Agonists of peroxisome proliferator-activated receptors (PPARs) have emerged as important pharmacological agents for improving insulin action. A major mechanism of action of PPAR agonists is thought to involve the alteration of the tissue distribution of nonesterified fatty acid (NEFA) uptake and utilization. To test this hypothesis directly, we examined the effect of the novel PPARalpha/gamma agonist tesaglitazar on whole-body insulin sensitivity and NEFA clearance into epididymal white adipose tissue (WAT), red gastrocnemius muscle, and liver in rats with dietary-induced insulin resistance. Wistar rats were fed a high-fat diet (59% of calories as fat) for 3 wk with or without treatment with tesaglitazar (1 micromol.kg(-1).d(-1), 7 d). NEFA clearance was measured using the partially metabolizable NEFA tracer, (3)H-R-bromopalmitate, administered under conditions of basal or elevated NEFA availability. Tesaglitazar improved the insulin sensitivity of high-fat-fed rats, indicated by an increase in the glucose infusion rate during hyperinsulinemic-euglycemic clamp (P < 0.01). This improvement in insulin action was associated with decreased diglyceride (P < 0.05) and long chain acyl coenzyme A (P < 0.05) in skeletal muscle. NEFA clearance into WAT of high-fat-fed rats was increased 52% by tesaglitazar under basal conditions (P < 0.001). In addition the PPARalpha/gamma agonist moderately increased hepatic and muscle NEFA utilization and reduced hepatic triglyceride accumulation (P < 0.05). This study shows that tesaglitazar is an effective insulin-sensitizing agent in a mild dietary model of insulin resistance. Furthermore, we provide the first direct in vivo evidence that an agonist of both PPARalpha and PPARgamma increases the ability of WAT, liver, and skeletal muscle to use fatty acids in association with its beneficial effects on insulin action in this model.

Role of thrombotic and fibrinolytic factors in acute coronary syndromes

There is a growing body of literature concerning the contribution of hemostatic factors to the development of cardiovascular disease. The mechanisms of the coagulation/fibrinolytic system are complicated and one factor is intimately interrelated with another; thus the contribution of each factor cannot be clearly understood, unless hemostatic factors are considered in accordance with endothelial function and vessel morphology. Although there are many clinical studies about the correlation between hemostatic factors and cardiovascular risk, the results are inconsistent and conflicting at times. Fibrinogen and D-dimer are associated with atherosclerosis or coronary events across multiple studies, even after multivariate adjustment. But the hemostatic factors are intimately correlated, so it can be said that focusing on one to the exclusion of others is inappropriate. The clinical trials with statins or angiotensin converting enzyme inhibitors have shown favorable effects on the prognosis of cardiovascular disease. The study of hemostatic factors in relation to these drugs has provided insights into understanding how these drugs produce beneficial effects.

Fibrates for treatment of the metabolic syndrome

The National Cholesterol Education Program Adult Treatment Panel III has provided a clinical definition for the metabolic syndrome that is practical for use in an office setting. Identification and treatment of the metabolic syndrome is of enormous public health importance because it is associated with a marked elevation in coronary heart disease risk and affects nearly 25% of adults in the United States. First-line therapy is lifestyle modification, which includes body weight reduction, increased physical activity, and moderation of the dietary glycemic load. Drug treatments focusing on the major components of the syndrome (atherogenic dyslipidemia, hypertension, and a prothrombotic state) have demonstrated efficacy for reducing coronary heart disease events. Fibrates seem to be particularly effective in patients for whom a disturbance of the triglyceride-high-density lipoprotein axis is the primary lipid disorder. Fibrates also appear to influence a number of emerging risk factors, including hemostatic and inflammatory markers and indicators of improved vascular wall biology, which may contribute to their cardioprotective effects.

O-arylmandelic acids as highly selective human PPAR alpha/gamma agonists

A new class of O-arylmandelic acid PPAR agonists show excellent anti-hyperglycemic efficacy in a db/db mouse model of DM2. These PPARalpha-weighted agonists do not show the typical PPARgamma associated side effects of BAT proliferation and cardiac hypertrophy in a rat tolerability assay.

Peroxisome proliferator-activated receptor-alpha agonist treatment in a transgenic model of type 2 diabetes reverses the lipotoxic state and improves glucose homeostasis

Abnormalities in insulin action are the characteristics of type 2 diabetes. Dominant-negative muscle-specific IGF-I receptor (MKR) mice exhibit elevated lipid levels at an early age and eventually develop type 2 diabetes. To evaluate the role of elevated lipids in the progression of the diabetic state, MKR mice were treated with WY14,643, a peroxisome proliferator-activated receptor (PPAR)-alpha agonist. WY14,643 treatment markedly reduced serum fatty acid and triglyceride levels within a few days, as well as muscle triglyceride levels, and subsequently normalized glucose and insulin levels in MKR mice. Hyperinsulinemic-euglycemic clamp analysis showed that WY14,643 treatment enhanced muscle and adipose tissue glucose uptake by improving whole-body insulin sensitivity. Insulin suppression of endogenous glucose production by the liver of MKR mice was also improved. The expression of genes involved in fatty acid oxidation was increased in liver and skeletal muscle, whereas gene expression levels of hepatic gluconeogenic enzymes were decreased in WY14,643-treated MKR mice. WY14,643 treatment also improved the pattern of glucose-stimulated insulin secretion from the perfused pancreata of MKR mice and reduced the beta-cell mass. Taken together, these findings suggest that the reduction in circulating or intracellular lipids by activation of PPAR-alpha improved insulin sensitivity and the diabetic condition of MKR mice.

Insulin resistance and cardiovascular events with low HDL cholesterol: the Veterans Affairs HDL Intervention Trial (VA-HIT)

OBJECTIVE

To assess the effect of insulin resistance and the benefit of the fibrate, gemfibrozil, on the incidence of major cardiovascular events in subjects with low HDL cholesterol and a broad range of triglyceride values who participated in the Veterans Affairs High Density Lipoprotein Intervention Trial (VA-HIT).

RESEARCH DESIGN AND METHODS

This intention-to-treat analysis, specified as a secondary objective in VA-HIT, determined using Cox proportional hazards models the 5-year combined incidence of nonfatal myocardial infarction, coronary heart disease (CHD) death, or stroke in relation to the presence or absence of insulin resistance (defined by the highest tertile of the homeostasis model assessment of insulin resistance, HOMA-IR) in conjunction with lower and higher levels of HDL cholesterol and triglycerides. The study population consisted of 2,283 men with known coronary heart disease (CHD), treated with either placebo or gemfibrozil, who could be subdivided into groups with diabetes with or without insulin resistance, with no diabetes but insulin resistance, and with neither diabetes nor insulin resistance.

RESULTS

With insulin resistance there was a significantly higher relative risk (RR) of a cardiovascular event both with diabetes (RR of 1.62 with 95% CI of 1.28-2.06) and without diabetes (RR of 1.43 with 95% CI of 1.03-1.98) than without insulin resistance. Throughout both lower and higher ranges of HDL cholesterol and triglycerides, the rate of new cardiovascular events and the reduction of events with gemfibrozil was greater in subjects with insulin resistance than without, despite the finding that an increase in HDL cholesterol and a decrease in triglycerides with gemfibrozil was less with insulin resistance than without insulin resistance.

CONCLUSIONS

Results show that in VA-HIT the occurrence of a new cardiovascular event and the benefit of fibrate therapy was much less dependent on levels of HDL cholesterol or triglycerides than on the presence or absence of insulin resistance.

Recurrent hypoglycaemic episodes in a patient with Type 2 diabetes under fibrate therapy

The causal relationship between dyslipidaemia and insulin resistance, two central components of the metabolic syndrome, is still poorly understood. We describe a 76-year-old patient with Type 2 diabetes mellitus and pronounced hypertriglyceridaemia. The patient required a total insulin dose of 148 IU/day for decent glycaemic control. The addition of the fibrate gemfibrozil to her medication resulted in a remarkable reduction in triglyceride levels (from 31.7 to 7.1 mmol/l). Consequently, the patient experienced recurrent hypoglycaemic episodes concurrent with a massive reduction in insulin requirements. Eventually, the insulin dosage was reduced by more than 65% to 48 IU/day, and HbA1c levels dropped from 9% to 6.5% over a period of 5 months without alterations in lifestyle, diet, body weight, or any other blood chemical values. Thus, this case report illustrates that treatment of hypertriglyceridaemia can reduce insulin requirements and harbours the risk of hypoglycaemia in patients with insulin-treated Type 2 diabetes mellitus.

Dyslipidemia and the vulnerable plaque

In the last decade, an increasingly sophisticated understanding of the pathogenesis of atherosclerosis and its cardiovascular consequences has emerged. The characteristics of the unstable atherosclerotic plaque, the substrate for the majority of acute coronary events, have been well defined: mild-to-moderate stenosis, a lipid-rich pool, few smooth muscle cells, a friable fibrous cap, and macrophage infiltration. Lipid modification, an important cardiovascular risk reduction strategy, induces a number of effects at the vascular level that may contribute to the clinical benefits seen in large-scale, prospective prevention trials. New developments in imaging technologies may afford improved opportunities to visualize the at-risk plaque and may provide new insights into the optimal management of the unstable plaque.

Peroxisome proliferator-activated receptor-alpha regulates fatty acid utilization in primary human skeletal muscle cells

In humans, skeletal muscle is a major site of peroxisome proliferator-activated receptor-alpha (PPAR-alpha) expression, but its function in this tissue is unclear. We investigated the role of hPPAR-alpha in regulating muscle lipid utilization by studying the effects of a highly selective PPAR-alpha agonist, GW7647, on [(14)C]oleate metabolism and gene expression in primary human skeletal muscle cells. Robust induction of PPAR-alpha protein expression occurred during muscle cell differentiation and corresponded with differentiation-dependent increases in oleate oxidation. In mature myotubes, 48-h treatment with 10-1,000 nmol/l GW7647 increased oleate oxidation dose-dependently, up to threefold. Additionally, GW7647 decreased oleate esterification into myotube triacylglycerol (TAG), up to 45%. This effect was not abolished by etomoxir, a potent inhibitor of beta-oxidation, indicating that PPAR-alpha-mediated TAG depletion does not depend on reciprocal changes in fatty acid catabolism. Consistent with its metabolic actions, GW7647 induced mRNA expression of mitochondrial enzymes that promote fatty acid catabolism; carnitine palmityltransferase 1 and malonyl-CoA decarboxylase increased approximately 2-fold, whereas pyruvate dehydrogenase kinase 4 increased 45-fold. Expression of several genes that regulate glycerolipid synthesis was not changed by GW7647 treatment, implicating involvement of other targets to explain the TAG-depleting effect of the compound. These results demonstrate a role for hPPAR-alpha in regulating muscle lipid homeostasis.

A pharmacoepidemiological assessment of the effect of statins and fibrates on fibrinogen concentration

Plasma fibrinogen is strongly associated with cardiovascular morbi-mortality. We investigated in the large cohort of the D.E.S.I.R. (data from an epidemiological study on the insulin resistance syndrome) study, the relationship between change in fibrinogen concentration over a 3-year follow-up and fibrate and statin use. Fibrinogen concentrations were higher at baseline among individuals treated with statins (n=130) compared to those treated with fibrates (n=251), even after adjustment for confounding factors (including total cholesterol, HDL cholesterol and triglycerides) (mean (S.D.): 2.8 (0.6) vs. 3.1 (0.6), P<0.001). We compared change in fibrinogen concentrations at 3 years of follow-up, between individuals who started fibrate (n=126) or statin (n=127) treatment during the follow-up and individuals (n=3906) who stayed without treatment during this period. After adjustment for baseline fibrinogen level, age, sex and changes in total cholesterol, triglycerides and alcohol intake, fibrinogen concentration decreased after fibrate treatment, while it increased after statin treatment and in those not using lipid lowering drugs (-0.07 (0.54) vs. 0.10 (0.54) vs. 0.08 (0.52) g/l respectively, P=0.01). No differences were observed between different statins or different fibrates. In conclusion, fibrates in contrast with statins may combine lipid-lowering with a beneficial effect on fibrinogen. This effect is independent of changes in cholesterol and triglyceride concentrations.

Effects of fibrates on serum metabolic parameters

Fibric acid derivatives are a class of hypolipidaemic drugs used in the treatment of patients with hypertriglyceridaemia, mixed hyperlipidaemia and diabetic dyslipidaemia. Fibrate therapy results in a significant decrease in serum triglycerides and an increase in high-density lipoprotein (HDL) cholesterol levels. The latest drugs of this class are also effective in lowering low-density (LDL) cholesterol levels and can change the distribution of LDL towards higher and larger particles. The effects of fibrates on lipid metabolism are mostly mediated through the activation of peroxisome proliferator-activated receptors (PPARalpha). A number of angiographic and clinical trials have confirmed that fibrates can slow the progression of atherosclerotic disease and decrease cardiovascular morbidity and mortality. Recently published data suggest that the ability of fibrates to prevent atherosclerosis is not related only to their hypolipidaemic effects but also to other 'pleiotropic effects', such as their anti-inflammatory, antioxidant and antithrombotic effects, as well as their ability to improve endothelial function. Interestingly, fibrates may favourably influence the thrombotic/fibrinolytic system. In fact, most of these drugs can significantly decrease plasma fibrinogen levels and inhibit tissue factor expression and activity in human monocytes and macrophages. Some studies have shown that fibrates can improve carbohydrate metabolism in patients with dyslipidaemia, including diabetic patients. Among fibrates only fenofibrate can significantly decrease serum uric acid levels by increasing renal urate excretion. Fibrates, with the possible exception of gemfibrozil, can significantly increase serum creatinine and homocysteine levels. Finally, a reduction in serum alkaline phosphatase and gamma glutamyltranspeptidase (gammaGT) activity is a well-documented effect of therapy with fibrates. The fibrates are generally well-tolerated drugs with few side-effects. The most important side-effect is myositis, which is observed in patients with impaired renal function or when statins are given concomitantly.

The use of fibrates and of statins in preventing atherosclerosis in diabetes

Atherosclerotic cardiovascular disease is the most common complication of diabetes. Recent guidelines in the USA have underlined the importance of treating lipid abnormalities in people with diabetes in order to reduce the risk of this complication. Should lifestyle approaches not be sufficient drugs will need to be added. The two most common classes of drugs to correct lipoprotein abnormalities are the statins and the fibrates. Each has a role to play and their use depends on the nature of the lipid abnormality that is present. Thus, rather than considering their use as an 'either/or' situation, this review will consider the uses of each class. In addition, as correcting the lipoprotein abnormalities may not account for all of the benefit produced by these agents, their non-lipid, pleotropic effects that may be antiatherogenic will also be reviewed.

High fat fed hamster, a unique animal model for treatment of diabetic dyslipidemia with peroxisome proliferator activated receptor alpha selective agonists

Dyslipidemia, a major risk factor for cardiovascular disease, may be directly linked to diabetic hyperglycemia and insulin resistance. An appropriate dyslipidemic animal model that has diabetes would provide an important tool for research on the treatment of diabetic dyslipidemia. Ten days of high fat feeding in golden Syrian hamsters resulted in a significant increase in insulin resistance and baseline serum lipid levels accompanied by a pronounced dyslipidemia. Thirteen days of treatment with fenofibrate, a peroxisome proliferator-activated receptor alpha (PPARalpha) selective agonist, produced a dose-dependent decrease in serum lipid levels. The pattern observed was characterized by lowered very-low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) and raised high-density lipoprotein (HDL) cholesterol in a fashion similar to that seen in man. Diabetic conditions were also significantly improved by fenofibrate with a normalization of impaired glucose tolerance and an improvement of insulin sensitivity during an oral glucose tolerance test. These data suggest that fenofibrate may correct not only the dyslipidemia but also the insulin resistance caused by a high fat diet, and the high fat fed hamster may be a good animal model for research on the treatment of diabetic dyslipidemia with PPARalpha selective agonists.

Peroxisome proliferator-activated receptor (PPAR)-alpha activation lowers muscle lipids and improves insulin sensitivity in high fat-fed rats: comparison with PPAR-gamma activation

Peroxisome proliferator-activated receptor (PPAR)-alpha agonists lower circulating lipids, but the consequences for muscle lipid metabolism and insulin sensitivity are not clear. We investigated whether PPAR-alpha activation improves insulin sensitivity in insulin-resistant rats and compared the effects with PPAR-gamma activation. Three-week high fat-fed male Wistar rats were untreated or treated with the specific PPAR-alpha agonist WY14643 or the PPAR-gamma agonist pioglitazone (both 3 mg x kg(-1) x day(-1)) for the last 2 weeks of high-fat feeding. Like pioglitazone, WY14643 lowered basal plasma levels of glucose, triglycerides (-16% vs. untreated), and leptin (-52%), and also muscle triglyceride (-34%) and total long-chain acyl-CoAs (LCACoAs) (-41%) (P < 0.05). In contrast to pioglitazone, WY14643 substantially reduced visceral fat weight and total liver triglyceride content (P < 0.01) without increasing body weight gain. WY14643 and pioglitazone similarly enhanced whole-body insulin sensitivity (clamp glucose infusion rate increased 35 and 37% and glucose disposal 22 and 15%, respectively, vs. untreated). Both agents enhanced insulin-mediated muscle glucose metabolic index (Rg') and reduced muscle triglyceride and LCACoA accumulation (P < 0.05). Although pioglitazone had more potent effects than WY14643 on muscle insulin sensitization, this was associated with its greater effect to reduce muscle LCACoA accumulation. Overall insulin-mediated muscle Rg' was inversely correlated with the content of LCACoAs (r = -0.74, P = 0.001) and with plasma triglyceride levels (r = -0.77, P < 0.001). We conclude that even though WY14643 and pioglitazone, representing PPAR-alpha and PPAR-gamma activation, respectively, may alter muscle lipid supply by different mechanisms, both significantly improve muscle insulin action in the high fat-fed rat model of insulin resistance, and this effect is proportional to the degree to which they reduce muscle lipid accumulation.