Gemfibrozil treatment increases low-density lipoprotein particle size in Type 2 diabetes mellitus but does not alter in vitro oxidizability

Effect of Fibrate Treatment on Circulating Adipokine Levels: A Systematic Review and Meta-analysis of Randomized Clinical Trials

BACKGROUND

Fibrates are widely used in the treatment of dyslipidemia and associated metabolic abnormalities; however, their effects on adipokines are unclear.

AIM OF THE STUDY

This meta-analysis of clinical trials aimed to evaluate the effect of fibrates on circulating adipokine levels.

METHODS

Only randomized controlled trials investigating the impact/effect of fibrate treatment on circulating adipokine levels were included from searches in PubMed-Medline, SCOPUS, ClinicalTrials.gov, Web of Science, and Google Scholar databases. A random effects model and the generic inverse variance method were used for the meta-analysis. Sensitivity analysis was conducted using the leave-one-out method.

RESULTS

This meta-analysis of 22 clinical trials showed a significant reduction on/in leptin (WMD: -1.58 ng/mL, 95% CI: -2.96, -0.20, p = 0.02, I2 = 0%), plasminogen activator inhibitor-1 (PAI-1) (WMD: -13.86 ng/mL, 95% CI: -26.70, -1.03, p = 0.03, I2 = 99%), and visfatin (WMD: -1.52 ng/mL, 95% CI: -2.49, -0.56, p = 0.002, I2 = 0%) after fibrate therapy; no significant effect was observed on adiponectin (WMD: -0.69 µg/ml, 95% CI: -1.40, 0.02, p = 0.06, I2 = 83%) and resistin (WMD: -2.27 ng/mL, 95% CI: -7.11, 2.57, p = 0.36, I2 = 0%). The sensitivity analysis was robust only for visfatin, while the effect size was sensitive to one arm for leptin, four for adiponectin, and two for PAI-1.

CONCLUSION

This meta-analysis showed that fibrate treatment significantly improves adipokine levels with a decrease in leptin, PAI-1, and visfatin, suggesting potential additional clinical therapeutic benefits through/of fibrate treatment on adipose tissue.

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.

The clinical significance of the size of low-density-lipoproteins and the modulation of subclasses by fibrates

BACKGROUND

Beyond total low-density-lipoproteins (LDL) levels, increasing evidence suggests that the 'quality' of LDL exerts a great influence on the cardiovascular risk. Several studies have also shown that the therapeutic modulation of LDL size is of benefit in reducing the risk of cardiovascular events. Hypolipidaemic treatment is able to alter LDL subclass distribution but strong variations have been noticed among different agents. Fibrates have a major impact on triglyceride metabolism and in modulating LDL size and subclasses, but variations exist among the different molecules.

METHODOLOGY

A literature search (by Medline and Scopus) was performed using the following headings: 'small dense LDL', 'LDL size', 'LDL subfractions', 'LDL subclasses', 'LDL distribution' and 'fenofibrate', 'bezafibrate', 'ciprofibrate' and 'gemfibrozil' up to 20 January 2007. The authors also manually reviewed the references of selected articles for any pertinent material.

RESULTS

Analysis of all published studies revealed that treatment with fenofibrate, ciprofibrate, bezafibrate and gemfibrozil is usually beneficial, and fenofibrate may be more efficacious than the other molecules. This is supported by using all the available techniques in subjects with a very wide range of lipid alterations.

CONCLUSION

Among the different agents, fenofibrate has been found to be particularly effective in modulating LDL size and subclasses in patients at higher cardiovascular risk, such as those with type 2 diabetes or the metabolic syndrome.

Effects of statins, fibrates, rosuvastatin, and ezetimibe beyond cholesterol: the modulation of LDL size and subclasses in high-risk patients

Increasing evidence suggests that the quality-rather than just the quantity-of low-density lipoproteins (LDLs) exerts a great influence on cardiovascular risk. LDLs comprise multiple subclasses with discrete size and density, and different physicochemical composition, metabolic behaviors, and atherogenicity. Individuals generally cluster into 2 broad subgroups. Most have a predominance of large LDLs, and some have a higher proportion of small particles. Small, dense LDLs are good predictors of cardiovascular events and progression of coronary artery disease. Their predominance has been accepted as an emerging cardiovascular risk factor by the National Cholesterol Education Program Adult Treatment Panel III. Several studies have shown that therapeutic modulation of LDL size and subclass is of great benefit in reducing the risk of cardiovascular events. This seems particularly true for statins and fibrates when they are administered to higher-risk patients, such as those with type 2 diabetes or vascular disease. Data reporting outcomes with the use of rosuvastatin, the latest statin molecule introduced to the market, and ezetimibe, a cholesterol absorption inhibitor, are promising.

Efficacy and safety of high-density lipoprotein cholesterol-increasing compounds: a meta-analysis of randomized controlled trials

OBJECTIVES

The aim of this research was to estimate the efficacy and safety of current high-density lipoprotein cholesterol (HDL-C)-increasing drugs.

BACKGROUND

Epidemiologic evidence has shown that HDL-C is inversely related to coronary heart disease (CHD) risk. However, the evidence for reducing CHD risk by raising HDL-C is thin, predominantly due to the paucity of effective and safe HDL-increasing drugs.

METHODS

Randomized controlled trials with fibrates and niacin, published between 1966 through February 2004 (MEDLINE), were retrieved. Information on treatment, baseline characteristics, serum lipids, end points, and side-effects were independently abstracted by two authors using a standardized protocol.

RESULTS

Data from 53 trials (16,802 subjects) using fibrates and 30 trials (4,749 subjects) using niacin were included. Random-effects model showed 11% versus 10% reduction in total cholesterol, 36% versus 20% reduction in triglycerides, 8% versus 14% reduction in low-density lipoprotein cholesterol, and 10% versus 16% increase in HDL-C for fibrates and niacin, respectively. Apart from flushes in the niacin group, both fibrates and niacin were shown to be well-tolerated and safe. Fibrates reduced the risk for major coronary events by 25% (95% confidence interval 10% to 38%), whereas current available data for niacin indicate a 27% reduction.

CONCLUSIONS

Fibrates reduce major coronary events and increase HDL-C levels without significant toxicity. Niacin has a more potent effect on HDL-C levels, whereas data on cardiovascular event rate reduction are limited. Future studies need to evaluate whether additional HDL increase by fibrates or particularly newer niacin formulations on top of statin therapy translates into further event reduction in high-risk subjects, without significant toxicity.

Peroxisome Proliferator-Activated Receptor-γ Agonist Increases Both Low-Density Lipoprotein Cholesterol Particle Size and Small High-Density Lipoprotein Cholesterol in Patients with Type 2 Diabetes Independent of Diabetic Control

OBJECTIVE

To ascertain whether troglitazone, independent of control of diabetes, increases low-density lipoprotein (LDL) particle size.

METHODS

We administered 600 mg of troglitazone (a peroxisome proliferator-activated receptor-gamma agonist) daily for 8 weeks to 10 patients with type 2 diabetes (8 of whom completed the study). Then troglitazone therapy was discontinued, and alternative medication for diabetic control was used for another 4 weeks. The LDL, very-low-density lipoprotein (VLDL), and high-density lipoprotein (HDL) concentrations and subpopulations, as well as blood glucose and hemoglobin A1c (HbA1c), were determined at weeks 0, 4, 8, and 12 and analyzed statistically.

RESULTS

Small, dense LDL cholesterol is commonly seen in patients with diabetes and is thought to be associated with an increased risk for coronary artery disease. After both 4 and 8 weeks of troglitazone therapy, control of diabetes was significantly improved (mean HbA1c values at baseline, week 4, and week 8 were 8.0 +/- 0.7%, 7.4 +/- 0.5%, and 7.0 +/- 0.7%, respectively; P<0.05). HbA1c (6.5 +/- 0.6% at 12 weeks) and blood glucose levels (126 +/- 19 mg/dL at 8 weeks versus 145 +/- 9 mg/dL at 12 weeks) were not significantly different 4 weeks after troglitazone therapy was discontinued. Troglitazone treatment increased the large LDL particle at 4 and 8 weeks, a change that significantly (P<0.05) enlarged the LDL particle size (20.5 +/- 0.3 nm, 21.2 +/- 0.3 nm, and 21.3 +/- 0.2 nm at baseline, week 4, and week 8, respectively). After 8 weeks of troglitazone therapy, VLDL triglycerides were reduced (195 +/- 37 mg/dL versus 136 +/- 28 mg/dL; P<0.05) and HDL was increased (31.6 +/- 2.4 mg/dL versus 35.5 +/- 2.9 mg/dL; P<0.05). This greater HDL value was due to an increase in the small HDL particles. A decrease in the larger VLDL particles (V5 and V6) resulted in a reduction in the mean VLDL particle size (59 +/- 3 nm versus 46 +/- 2 nm; P<0.05). Despite the fact that control of diabetes remained significantly improved after troglitazone therapy was discontinued, the LDL particle size decreased to the baseline value. This change was due to a reduction in the large LDL cholesterol particle (L3).

CONCLUSION

This study shows that troglitazone therapy increases LDL particle size, reduces VLDL particle size, and increases small HDL particles. These changes may lower the risk for coronary artery disease.

A cross-sectional study of the effects of type 2 diabetes and other cardiovascular risk factors on structure and function of nonstenotic arteries of the lower limb

OBJECTIVE

To compare intimal-medial thickness (IMT) and pulse wave conduction velocity (PWCV) in unstenosed arteries of the lower limb in subjects with and without type 2 diabetes and to determine the contribution of a range of cardiovascular risk factors.

RESEARCH DESIGN AND METHODS

IMT and PWCV were determined in lower-limb arteries of 79 subjects with diabetes and 77 euglycemic subjects. Plasma lipids were determined by enzymatic assays, and LDL particle size was measured by gradient gel electrophoresis. Lag time for copper-induced oxidation of LDL was determined. alpha-Tocopherol, retinol, and ascorbate levels were determined by high-performance liquid chromatography, soluble E-selectin by enzyme-linked immunosorbent assay, and fibrinogen and factor VII by automated assays.

RESULTS

Subjects with diabetes had greater superficial femoral artery (SFA) IMT, popliteal artery (PA) IMT, and SFA PWCV (all P < 0.0001). In univariate analysis, IMT and PWCV correlated with increased waist-to-hip ratio, triglycerides, and fibrinogen and inversely with HDL cholesterol and LDL size. Ascorbate was inversely associated with IMT, and LDL lag time was inversely correlated with PWCV. Subjects with the greatest number of features of the metabolic syndrome had the highest IMT and PWCV.

CONCLUSIONS

Adverse changes in the structure and function of unstenosed lower-limb arteries are present in type 2 diabetes and are associated with features of the metabolic syndrome.

Gemfibrozil lowers plasma lipids and increases polyunsaturated fatty acid content and oxidative susceptibility of lipoproteins in hypertriglyceridemia

BACKGROUND

Gemfibrozil is an effective drug in the treatment of hypertriglyceridemia and its effects on morbidity and mortality seem out of proportion to its lipid lowering actions. There is considerable interest in its potential effects on lipoprotein fatty acid composition and consequent effect on oxidative susceptibility. Experimental results are not conclusive regarding whether gemfibrozil alters lipid composition or oxidative susceptibility of lipoproteins in humans. Here we investigate this question using different methodology than employed in previous investigations.

METHODS

Eleven hypertriglyceridemic individuals completed a 12-week course of gemfibrozil therapy (600 mg twice daily) intended to primarily evaluate a new way of assessing lipoprotein susceptibility to oxidation in relation to changes in the fatty acid profile. We measured susceptibility of lipoproteins in the plasma macromolecule fraction to copper-mediated oxidation. In addition, plasma lipids were separated into phospholipid (PL), cholesterol ester (CE) and triglyceride (TG) fractions and the fatty acid composition of these classes determined by gas-liquid chromatography. The relation between changes in lipid concentration, fatty acid composition and oxidative parameters (principally lag time) was examined by correlational analysis.

RESULTS

Triglyceride concentrations and total cholesterol concentrations responded appropriately to gemfibrozil (lowered by 55% and 15%, respectively). Polyunsaturated fatty acid (PUFA) proportion increased significantly in cholesterol ester and phospholipid fractions of plasma lipids at the expense of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA). Oxidative parameters also changed significantly. Lag time (LT) and maximal extent of oxidation showed the most significant changes. Lag time, the principle measure of lipoprotein susceptibility to oxidation, was decreased by gemfibrozil. The increase in polyunsaturated fatty acid content in phospholipid and cholesterol ester significantly correlated with decreased lag time.

CONCLUSION

These data support the notion that gemfibrozil increases the proportion of polyunsaturated fatty acids in plasma lipids and that this increase is associated with an increase in lipoprotein oxidative susceptibility as measured by lag time in hypertriglyceridemia.

Gemfibrozil improves insulin sensitivity and flow-mediated vasodilatation in type 2 diabetic patients

BACKGROUND

Endothelial dysfunction is an early feature of atherosclerosis. The relationship between insulin action and hypertriglyceridaemia on endothelial function is still debated.

MATERIALS AND METHODS

This study was designed to determine the effect of a 3 month treatment with Gemfibrozil (GF) on flow-mediated vasodilatation and insulin sensitivity. Ten type 2 diabetic patients were randomised in crossover, double blind fashion, either to GF, 600 mg b.i.d. or placebo, for 12 weeks. Lipid profile, low-density lipoprotein (LDL) distribution and flotation properties, insulin action and flow-mediated vasodilatation (FMD) by brachial artery ultrasound, were assessed.

RESULTS

GF decreased serum triglyceride (TG) concentration with an absolute difference of 1.79 +/- 1.28 mmol L-1 (P < 0.0016) between active treatment and placebo, and significantly increased serum high-density lipoprotein (HDL) cholesterol (P = 0.0233). No differences were observed in total, intermediate-density lipoproteins (IDL), LDL cholesterol concentration and LDL peak buoyancy between treatments. GF also improved SI, an index of insulin action (P = 0.005). The FMD was 7 +/- 3% in the baseline condition, 7 +/- 2% during placebo and 14 +/- 3% after GF (P < 0.006).

CONCLUSIONS

GF treatment improves both insulin action and flow-mediated vasodilatation in type 2 diabetic patients. The reduction of TG concentration allows the simultaneous correction of two important components of the metabolic syndrome.

Diabetic dyslipidaemia: current treatment recommendations

Insulin deficiency and hyperglycaemia in type 1 (insulin-dependent) diabetes mellitus produce lipid abnormalities, which can be corrected by appropriate insulin therapy. Diabetic nephropathy, which is the main risk factor for coronary heart disease (CHD) in type 1 diabetes, causes pro-atherosclerotic changes in lipid metabolism. Detection and treatment of elevated cholesterol levels is likely to be of benefit in these patients. Type 2 (noninsulin-dependent) diabetes mellitus is associated with abnormal lipid metabolism, even when glycaemic control is good and nephropathy absent. Elevated triglyceride levels, reduced high density lipoprotein (HDL) cholesterol and a preponderance of small, dense low density lipoprotein (LDL) particles are the key abnormalities that constitute diabetic dyslipidaemia. The prevalence of hypercholesterolaemia is the same as for the nondiabetic population, but the relative risk of CHD is greatly increased at every level of cholesterol. Based on effectiveness, tolerability and clinical trial results, treatment with HMG-CoA reductase inhibitors to lower LDL cholesterol is recommended as primary therapy. These agents are also moderately effective at reducing triglyceride and increasing HDL cholesterol levels. If hypertriglyceridaemia predominates, treatment with fibric acid derivatives is appropriate, although there is currently only limited clinical trial evidence that the risk of CHD will be reduced. In type 1 diabetes, but particularly in type 2 diabetes, lipid disorders are likely to contribute significantly to the increased risk of macrovascular complications. especially CHD. Management of the disordered lipid metabolism should be given a high priority in the clinical care of all patients with diabetes.

Fibrates, dyslipoproteinaemia and cardiovascular disease

Recent epidemiological data have reaffirmed that elevated plasma triglyceride and low HDL-cholesterol levels are important risk factors for atherosclerotic vascular disease. The rationale for the clinical use of fibric acid derivatives, which are designed to correct this metabolic nexus, is now on firmer ground. The mechanism of action of fibrates on lipoprotein metabolism has recently been elucidated at the molecular level and involves the activation of peroxisome proliferator-activated receptor-alpha 1 in the liver, with the net effect of improving the plasma transport rates of several lipoproteins. Other potential anti-atherothrombotic effects include the inhibition of coagulation and enhancement of fibrinolysis, as well as the inhibition of inflammatory mediators involved in atherogenesis. These consequences probably underpin the favourable effects of fibrates seen in recent angiographic and clinical trials. Two important clinical trials on the effect of gemfibrozil (Veterans Administration-HDL-Cholesterol Intervention Trial) and bezafibrate (Bezafibrate Infarction Prevention Study) have recently been completed in subjects with elevated triglyceride, low HDL and normal or near-normal LDL-cholesterol levels. The results testify to the efficacy of these agents in decreasing the incidence of cardiovascular events, particularly in patients with multiple risk factors and plasma triglyceride levels of over 2.2 mmol/l. The findings of these trials are compared with the statin-based Air Force/Texas Coronary Atherosclerosis Prevention Study, with a recommendation that future studies in appropriately selected patients should examine the synergistic effect of the fibrate/statin combination. The absolute risk reduction in the incidence of coronary events in the Veterans Administration-HDL-Cholesterol Intervention Trial compares favourably with the statin trials. The therapeutic aspects of the efficacy and safety of fibrates are reviewed. Besides primary mixed hyperlipidaemias, particular indications for the clinical use of fibrates include type 2 diabetes, the metabolic syndrome and renal insufficiency. The St Mary's, Ealing, Northwick Park Diabetes Cardiovascular Disease Prevention Study has suggested that fibrates may decrease the incidence of coronary events in type 2 diabetes, but this hypothesis will be more extensively tested in the Diabetes Atherosclerosis Intervention Study, Fenofibrate in Event Lowering in Diabetes Study and Lipids in Diabetes Study projects. Although significant new knowledge has accrued over the past few years concerning the fundamental and clinical aspects of fibrates, the success of these agents in clinical practice depends on the availability of methods for assessing cardiovascular risk as well as on treatment guidelines, which as presently designed and recommended may be inaccurate and suboptimal.

Atherogenic lipoprotein phenotype in type 2 diabetes: reversal with micronised fenofibrate

BACKGROUND

To assess the short-term effects of a micronised formulation of fenofibrate on lipids, lipoproteins and their composition, reflecting an atherogenic lipoprotein phenotype (ALP), in patients with stable Type 2 diabetes.

METHODS

Thirty-two (18 male, 14 female) patients with Type 2 diabetes were randomised to a double-blind, placebo-controlled parallel group study after a 4-week diet run-in phase to a 12-week treatment period with either daily micronised fenofibrate 200 mg (Lipantil Micro((R))) or placebo.

RESULTS

Baseline mean lipid and lipoproteins were similar in both groups: total cholesterol (TC) 7.5 mmol/l, serum triglyceride (TG) 3. 1 mmol/l, HDL-cholesterol (HDL-c) 1.2 mmol/l, LDL-cholesterol (LDL-c) 4.7 mmol/l, and a predominance (52%) of small dense LDL-III at concentration of 192 mg lipoprotein/100 ml, reflecting an ALP. Treatment with micronised fenofibrate resulted in significant changes in TC (-17%, p<0.001), serum TG (-44%, p<0.05), HDL-c (+20%, p<0.01), LDL-c (-22%, p<0.001), apo-B (-18%, p<0.05) and alterations in LDL subfraction masses (LDL-I +64%, p<0.05; LDL-II +53%, p<0.05; LDL-III -51%, p<0.001) resulting in LDL-III comprising 28% of total LDL (p<0.001). In the placebo group the only significant changes were in TG (+21%, p<0.05) and apo-B (+9%, p<0.05).

CONCLUSIONS

Micronised fenofibrate therapy in patients with Type 2 diabetes improved an establisheded ALP resulting in a more favourable lipid and LDL subfraction profile. The long-term clinical implications of these changes await the results of the major intervention trials of lipid modification in Type 2 diabetes.