Fenofibrate raises plasma homocysteine levels in the fasted and fed states

Impact of Statin or Fibrate Therapy on Homocysteine Concentrations: A Systematic Review and Meta-analysis

INTRODUCTION

Statins and fibrates are two lipid-lowering drugs used in patients with dyslipidemia. This systematic review and meta-analysis were conducted to determine the magnitude of the effect of statin and fibrate therapy on serum homocysteine levels.

METHODS

A search was undertaken of the PubMed, Scopus, Web of Science, Embase, and Google Scholar electronic databases up to 15 July 2022. Primary endpoints focused on plasma homocysteine levels. Data were quantitatively analyzed using fixed or random- effect models, as appropriate. Subgroup analyses were conducted based on the drugs and hydrophilic-lipophilic balance of statins.

RESULTS

After screening 1134 papers, 52 studies with a total of 20651 participants were included in the meta-analysis. The analysis showed a significant decrease in plasma homocysteine levels after statin therapy (WMD: -1.388 μmol/L, 95% CI: [-2.184, -0.592], p = 0.001; I2 = 95%). However, fibrate therapy significantly increased plasma homocysteine levels (WMD: 3.459 μmol/L, 95% CI: [2.849, 4.069], p < 0.001; I2 = 98%). The effect of atorvastatin and simvastatin depended on the dose and duration of treatment (atorvastatin [coefficient: 0.075 [0.0132, 0.137]; p = 0.017, coefficient: 0.103 [0.004, 0.202]; p = 0.040, respectively] and simvastatin [coefficient: -0.047 [-0.063, -0.031]; p < 0.001, coefficient: 0.046 [0.016, 0.078]; p = 0.004]), whereas the effect of fenofibrate persisted over time (coefficient: 0.007 [-0.011, 0.026]; p = 0.442) and was not altered by a change in dosage (coefficient: -0.004 [-0.031, 0.024]; p = 0.798). In addition, the greater homocysteine- lowering effect of statins was associated with higher baseline plasma homocysteine concentrations (coefficient: -0.224 [-0.340, -0.109]; p < 0.001).

CONCLUSION

Fibrates significantly increased homocysteine levels, whereas statins significantly decreased them.

Effects of low and high doses of fenofibrate on protein, amino acid, and energy metabolism in rat

A feared adverse effect of dyslipidaemia therapy by fibrates is myopathy. We examined the effect of fenofibrate (FF) on protein and amino acid metabolism. Rats received a low (50 mg/kg, LFFD) or high (300 mg/kg, HFFD) dose of FF or vehicle daily by oral gavage. Blood plasma, liver, and soleus and extensor digitorum longus muscles were analysed after 10 days. The FF-treated rats developed hepatomegaly associated with increased hepatic carnitine and ATP and AMP concentrations, decreased protein breakdown, and decreased concentrations of DNA and triglycerides. HFFD increased plasma ALT and AST activities. The weight and protein content of muscles in the HFFD group were lower compared with controls. In muscles of the LFFD group there were increased ATP and decreased AMP concentrations; in the HFFD group AMP was increased. In both FF-treated groups there were increased glycine, phenylalanine, and citrulline and decreased arginine and branched-chain keto acids (BCKA) in blood plasma. After HFFD there were decreased levels of branched-chain amino acids (BCAA; valine, leucine and isoleucine), methionine, and lysine and increased homocysteine. Decreased arginine and increased glycine concentrations were found in both muscles in FF-treated animals; in HFFD-treated animals lysine, methionine, and BCAA were decreased. We conclude that FF exerts protein-anabolic effects on the liver and catabolic effects on muscles. HFFD causes signs of hepatotoxicity, impairs energy and protein balance in muscles, and decreases BCAA, methionine, and lysine. It is suggested that increased glycine and decreased lysine and methionine levels are due to activated carnitine synthesis; decreased BCAA and BCKA levels are due to increased BCAA oxidation.

Hyperhomocysteinemic Diabetic Cardiomyopathy: Oxidative Stress, Remodeling, and Endothelial-Myocyte Uncoupling

Accumulation of oxidized-matrix (fibrosis) between the endothelium (the endothelial cells embedded among the myocytes) and cardiomyocytes is a hallmark of diabetes mellitus and causes diastolic impairment. In diabetes mellitus, elevated levels of homocysteine activate matrix metalloproteinase and disconnect the endothelium from myocytes. Extracellular matrix functionally links the endothelium to the cardiomyocyte and is important for their synchronization. However, in diabetes mellitus, a disconnection is caused by activated metalloproteinase, with subsequent accumulation of oxidized matrix between the endothelium and myocyte. This contributes to endothelial-myocyte uncoupling and leads to impaired diastolic relaxation of the heart in diabetes mellitus. Elevated levels of homocysteine in diabetes are attributed to impaired homocysteine metabolism by glucose and insulin and decreased renal clearance. Homocysteine induces oxidative stress and is inversely related to the expression of peroxisome proliferators activated receptor (PPAR). Several lines of evidence suggest that ablation of the matrix metalloproteinase (MMP-9) gene ameliorates the endothelial-myocyte uncoupling in diabetes mellitus. Homocysteine competes for, and decreases the PPARγ activity. In diabetes mellitus, endothelial-myocyte uncoupling is associated with matrix metalloproteinase activation and decreased PPARγ activity. The purpose of this review is to discuss the role of endothelial-myocyte uncoupling in diabetes mellitus and increased levels of homocysteine, causing activation of latent metalloproteinases, decreased levels of thioredoxin and peroxiredoxin, and cardiac tissue inhibitor of metalloproteinase (CIMP) in response to antagonizing PPARγ.

A reappraisal of the risks and benefits of treating to target with cholesterol lowering drugs

Atherosclerotic cardiovascular disease (CVD) is the number one cause of death globally, and lipid modification, particularly lowering of low density lipoprotein cholesterol (LDLc), is one of the cornerstones of prevention and treatment. However, even after lowering of LDLc to conventional goals, a sizeable number of patients continue to suffer cardiovascular events. More aggressive lowering of LDLc and optimization of other lipid parameters like triglycerides (TG) and high density lipoprotein cholesterol (HDLc) have been proposed as two potential strategies to address this residual risk. These strategies entail use of maximal doses of highly potent HMG CoA reductase inhibitors (statins) and combination therapy with other lipid modifying agents. Though statins in general are fairly well tolerated, adverse events like myopathy are dose related. There are further risks with combination therapy. In this article, we review the adverse effects of lipid modifying agents used alone and in combination and weigh these effects against the evidence demonstrating their efficacy in reducing cardiovascular events, cardiovascular mortality, and all cause mortality. For patients with established CVD, statins are the only group of drugs that have shown consistent reductions in hard outcomes. Though more aggressive lipid lowering with high dose potent statins can reduce rates of non fatal events and need for interventions, the incremental mortality benefits remain unclear, and their use is associated with a higher rate of drug related adverse effects. Myopathy and renal events have been a significant concern with the use of high potency statin drugs, in particular simvastatin and rosuvastatin. For patients who have not reached target LDL levels or have residual lipid abnormalities on maximal doses of statins, the addition of other agents has not been shown to improve clinical outcomes and carries an increased risk of adverse events. The clinical benefits of drugs to raise HDLc remain unproven. In patients without known cardiovascular disease, there is conflicting evidence as to the benefits of aggressive pursuit of numerical lipid targets, particularly with respect to all cause mortality. Certainly, in statin intolerant patients, alternative agents with a low side effect profile are desirable. Bile acid sequestrants are an effective and safe choice for decreasing LDLc, and omega-3 fatty acids are safe agents to decrease TG. There remains an obvious need to design and carry out large scale studies to help determine which agents, when combined with statins, have the greatest benefit on cardiovascular disease with the least added risk. These studies should be designed to assess the impact on clinical outcomes rather than surrogate endpoints, and require a comprehensive assessment and reporting of safety outcomes.

Fenofibrate: a review of its use in dyslipidaemia

Fenofibrate is a fibric acid derivative indicated for the treatment of severe hypertriglyceridaemia and mixed dyslipidaemia in patients who have not responded to nonpharmacological therapies. The lipid-modifying effects of fenofibrate are mediated by the activation of peroxisome proliferator-activated receptor-α. Fenofibrate also has nonlipid, pleiotropic effects (e.g. reducing levels of fibrinogen, C-reactive protein and various pro-inflammatory markers, and improving flow-mediated dilatation) that may contribute to its clinical efficacy, particularly in terms of improving microvascular outcomes. Fenofibrate improves the lipid profile (particularly triglyceride [TG] and high-density lipoprotein-cholesterol [HDL-C] levels) in patients with dyslipidaemia. Compared with statin monotherapy, fenofibrate monotherapy tends to improve TG and HDL-C levels to a significantly greater extent, whereas statins improve low-density lipoprotein-cholesterol (LDL-C) and total cholesterol levels to a significantly greater extent. Fenofibrate is also associated with promoting a shift from small, dense, atherogenic LDL particles to larger, less dense LDL particles. Combination therapy with a statin plus fenofibrate generally improves the lipid profile to a greater extent than monotherapy with either agent in patients with dyslipidaemia and/or type 2 diabetes mellitus or the metabolic syndrome. In the pivotal FIELD and ACCORD trials in patients with type 2 diabetes, fenofibrate did not significantly reduce the risk of coronary heart disease events to a greater extent than placebo, and simvastatin plus fenofibrate did not significantly reduce the risk of major cardiovascular (CV) events to a greater extent than simvastatin plus placebo. However, the risk of some nonfatal macrovascular events and the incidence of certain microvascular outcomes were reduced significantly more with fenofibrate than with placebo in the FIELD trial, and in the ACCORD trial, patients receiving simvastatin plus fenofibrate were less likely to experience progression of diabetic retinopathy than those receiving simvastatin plus placebo. Subgroup analyses in the FIELD and ACCORD Lipid trials indicate that fenofibrate is of the greatest benefit in decreasing CV events in patients with atherogenic dyslipidaemia. Fenofibrate is generally well tolerated when administered alone or in combination with a statin. Thus, in patients with dyslipidaemia, particularly atherogenic dyslipidaemia, fenofibrate is a useful treatment option either alone or in combination with a statin.

Synergism in hyperhomocysteinemia and diabetes: role of PPAR gamma and tempol

BACKGROUND

Hyperhomocysteinemia (HHcy) and hyperglycemia cause diabetic cardiomyopathy by inducing oxidative stress and attenuating peroxisome proliferator- activated receptor (PPAR) gamma. However, their synergistic contribution is not clear.

METHODS

Diabetic Akita (Ins2+/-) and hyperhomocysteinemic cystathionine beta synthase mutant (CBS+/-) were used for M-mode echocardiography at the age of four and twenty four weeks. The cardiac rings from WT, Akita and hybrid (Ins2+/-/CBS+/-) of Akita and CBS+/- were treated with different doses of acetylcholine (an endothelial dependent vasodilator). High performance liquid chromatography (HPLC) was performed for determining plasma homocysteine (Hcy) level in the above groups. Akita was treated with ciglitazone (CZ) - a PPAR gamma agonist and tempol-an anti-oxidant, separately and their effects on cardiac remodeling were assessed.

RESULTS

At twenty four week, Akita mice were hyperglycemic and HHcy. They have increased end diastolic diameter (EDD). In their heart PPAR gamma, tissue inhibitor of metalloproteinase-4 (TIMP-4) and anti-oxidant thioredoxin were attenuated whereas matrix metalloproteinase (MMP)-9, TIMP-3 and NADPH oxidase 4 (NOX4) were induced. Interestingly, they showed synergism between HHcy and hyperglycemia for endothelial-myocyte (E-M) uncoupling. Additionally, treatment with CZ alleviated MMP-9 activity and fibrosis, and improved EDD. On the other hand, treatment with tempol reversed cardiac remodeling in part by restoring the expressions of TIMP-3,-4, thioredoxin and MMP-9.

CONCLUSIONS

Endogenous homocysteine exacerbates diabetic cardiomyopathy by attenuating PPAR gamma and inducing E-M uncoupling leading to diastolic dysfunction. PPAR gamma agonist and tempol mitigates oxidative stress and ameliorates diastolic dysfunction in diabetes.

Homocysteine and Hypertension in Diabetes: Does PPARgamma Have a Regulatory Role?

Dysfunction of macro- and microvessels is a major cause of morbidity and mortality in patients with cardio-renovascular diseases such as atherosclerosis, hypertension, and diabetes. Renal failure and impairment of renal function due to vasoconstriction of the glomerular arteriole in diabetic nephropathy leads to renal volume retention and increase in plasma homocysteine level. Homocysteine, which is a nonprotein amino acid, at elevated levels is an independent cardio-renovascular risk factor. Homocysteine induces oxidative injury of vascular endothelial cells, involved in matrix remodeling through modulation of the matrix metalloproteinase (MMP)/tissue inhibitor of metalloproteinase (TIMP) axis, and increased formation and accumulation of extracellular matrix protein, such as collagen. In heart this leads to increased endothelial-myocyte uncoupling resulting in diastolic dysfunction and hypertension. In the kidney, increased matrix accumulation in the glomerulus causes glomerulosclerosis resulting in hypofiltration, increased renal volume retention, and hypertension. PPARγ agonist reduces tissue homocysteine levels and is reported to ameliorate homocysteine-induced deleterious vascular effects in diabetes. This review, in light of current information, focuses on the beneficial effects of PPARγ agonist in homocysteine-associated hypertension and vascular remodeling in diabetes.

Effect of lipopenic and hypotensive treatment on homocysteine levels in type 2 diabetics

AIM

Evaluate the effect of lipopenic and hypotensive treatment on homocysteine levels.

METHODS

We recruited 145 type 2 diabetics and 130 control subjects. Thirty-seven diabetics had no complications, 54 had microvascular complications and 54 had macrovascular complications. We determined the parameters homocysteine of lipid, vitamin B12, triglycerides, and folates for all subjects. Associated treatments used one or more of the following drugs, statin, fibrate, angiotensin-converting enzyme inhibitor and beta-blockers.

RESULTS

Hyperhomocysteinemia was present in 35.6% of patients. Diabetics had elevated serum levels of triglycerides (P < 0.001), homocysteine (P < 0.01), folates (P < 0.01) and vitamin B12 (P < 0.001). A strong association was found between type 2 diabetes and hyperhomocysteinemia (P < 0.001). Diabetics with associated treatment had elevated homocysteine, vitamin B12 and folate levels when compared to diabetes-free controls. For diabetics with macrovascular complications, we found significant differences in homocysteine (P = 0.010) and folate (P = 0.014) between those taking associated drugs and those who did not. For diabetics with microvascular complications, a significant difference was found in folate only (P = 0.012).

CONCLUSION

Drugs used for hypertension and hyperlipidemia may have an effect on homocysteine levels, for this reason the interaction between drug action and homocysteine levels should be taken into consideration.

Lipids, lipid modifying agents and cardiovascular risk: a review of the evidence

It is well-established that serum total-cholesterol, LDL-cholesterol, low HDL-cholesterol and calculated indices such as total cholesterol:HDL-cholesterol ratio or less commonly used indices such as non-HDL cholesterol are strongly predictive of cardiovascular events. Serum triglycerides, by contrast, are only modestly associated with coronary heart disease (CHD) in multivariate analysis and incorporation of triglycerides into prediction algorithms is therefore unlikely to improve their prediction capability. Meta-analysis of studies including > 90,000 subjects has provided robust evidence that statins reduce important clinical end-points. These included a 12% fall in all-cause mortality, 19% fall in CHD mortality and 23% fall in CHD mortality or myocardial infarction. Furthermore there are high quality data showing additional benefit of intensive statin therapy over standard statin therapy for secondary prevention of cardiovascular disease. However, meta-analysis of 10 fibrate trials has shown inconsistent evidence of vascular benefit and non-cardiovascular mortality has been slightly but consistently elevated in most fibrate trials and in meta-analysis. The general use of fibrates for cardiovascular risk reduction can therefore not be supported at present. Other second line agents such as bile acid sequestrants, nicotinic acid and omega-3 fatty acid supplements have been evaluated in a few randomized controlled studies in which cardiovascular benefit has been found but clearly further data are required to properly establish their use in clinical practice. Ongoing studies such as ACCORD, IMPROVE-IT, ASCEND, ORIGIN and HPS2-THRIVE should assist in answering outstanding questions over the next 5 years.

Therapeutic effects of fibrates in postprandial lipemia

Hypertriglyceridemia is observed in many metabolic diseases such as the metabolic syndrome, diabetes mellitus, or mixed dyslipidemia frequently leading to premature coronary heart disease (CHD). Additionally, several studies have shown that postprandial hypertriglyceridemia is pronounced in patients with CHD, metabolic syndrome, hypertension, and other pathologic conditions. The triglyceride-rich lipoprotein remnants accumulating in the postprandial state seem to be involved in atherogenesis and in events leading to thrombosis. Since abnormal postprandial lipemia is associated with pathologic conditions, its treatment is of clinical importance.Fibrates are of significant help in managing hypertriglyceridemia. This review summarizes the effect of fibric acid derivatives on postprandial lipemia. Fibrates decrease the production of and enhance the catabolism of triglyceride-rich lipoproteins through the activation of peroxisome proliferator-activated receptor-alpha. Results of clinical studies with fibrates have confirmed their action in decreasing postprandial triglyceride levels by increasing lipoprotein lipase activity, decreasing apolipoprotein CIII production, and by increasing fatty acid oxidation in the liver.It is concluded that fibrates are effective agents in lowering the postprandial increase in remnant lipoprotein particles and retinyl palmitate. Furthermore, fibrates can also affect the postprandial lipid profile by increasing hepatic lipase levels and in some cases, by reducing cholesterol ester transfer protein activity. The main target of fibrate therapy is to improve fasting hypertriglyceridemia, which is an essential component associated with improving postprandial lipemia. Fibrates are well tolerated by patients and adverse effects have been reported rarely after their administration.

Treatment of hyperlipidaemia with fenofibrate and related fibrates

BACKGROUND

Fenofibrate is the most widely used fibrate. Its efficacy and tolerability in the treatment of hypertriglyceridaemia and combined hyperlipidaemia have been demonstrated in several clinical trials.

OBJECTIVE

To review the pharmacology, lipid-lowering and extra-lipid effects of fenofibrate and to preview ABT-335, an investigational new fenofibric acid molecule.

RESULTS

The effects of fenofibrate are mediated through the active metabolite fenofibric acid, and are described in detail in the paper. ABT-335 is a salt of fenofibric acid and, unlike fenofibrate, does not require first pass metabolism to the active moiety. ABT-335 is being developed for combination use with statins, and has recently completed three large Phase III randomised controlled trials in which the efficacy and safety of ABT-335 in combination with the three most commonly prescribed statins, atorvastatin, simvastatin and rosuvastatin, was evaluated in patients with mixed dyslipidaemia.

CONCLUSION

ABT-335 in combination with statins may provide a safe and efficacious treatment modality that enables achievement of several therapeutic goals in patients with mixed dyslipidaemia who have high cardiovascular risk.

Ciglitazone, a PPARgamma agonist, ameliorates diabetic nephropathy in part through homocysteine clearance

Diabetes and hyperhomocysteinemia (HHcy) are two independent risk factors for glomeruloslerosis and renal insufficiency. Although PPARgamma agonists such as ciglitazone (CZ) are known to modulate diabetic nephropathy, the role of CZ in diabetes-associated HHcy and renopathy is incompletely defined. We tested the hypothesis that induction of PPARgamma by CZ decreases tissue Hcy level; this provides a protective role against diabetic nephropathy. C57BL/6J mice were administered alloxan to create diabetes. Mice were grouped to 0, 1, 10, 12, and 16 wk of treatment; only 12- and 16-wk animals received CZ in drinking water after a 10-wk alloxan treatment. In diabetes, PPARgamma cDNA, mRNA, and protein expression were repressed, whereas an increase in plasma and glomerular Hcy levels was observed. CZ normalized PPARgamma mRNA and protein expression and glomerular level of Hcy, whereas plasma level of Hcy remained unchanged. GFR was dramatically increased at 1-wk diabetic induction, followed by hypofiltration at 10 wk, and was normalized by CZ treatment. This result corroborated with glomerular and preglomerular arteriole histology. A steady-state increase of RVR in diabetic mice became normal with CZ treatment. CZ ameliorated decrease bioavailability of NO in the diabetic animal. Glomerular MMP-2 and MMP-9 activities as well as TIMP-1 expression were increased robustly in diabetic mice and normalized with CZ treatment. Interestingly, TIMP-4 expression was opposite to that of TIMP-1 in diabetic and CZ-treated groups. These results suggested that diabetic nephropathy exacerbated glomerular tissue level of Hcy, and this caused further deterioration of glomerulus. CZ, however, protected diabetic nephropathy in part by activating PPARgamma and clearing glomerular tissue Hcy.

Therapies to increase high-density lipoprotein cholesterol and their effect on cardiovascular outcomes and regression of atherosclerosis

Epidemiological studies have shown that decreased level of high-density lipoprotein (HDL) cholesterol (C) is an independent inverse predictor of coronary artery disease (CAD) even in patients with normal levels of low-density lipoprotein (LDL)-C. There is an abundance of evidence in favor of statins and aggressive LDL-C lowering therapy for both primary and secondary prevention of CAD. In contrast, the evidence for reduction of CAD risk with HDL-C raising therapy is relatively thin, partly due to the paucity of effective and safe drugs for increasing HDL-C level. However, there are emerging new therapies for raising HDL-C level and growing evidence in favor of pharmacologic therapies to raise HDL-C level. We present in this article a review of pharmacologic therapies that are currently available to increase HDL-C level, their safety and efficacy in relation to cardiovascular endpoints.

Reduced folate carrier 80A-->G polymorphism, plasma folate, and risk of placental abruption

Folate deficiency and maternal smoking are strong risk factors for placental abruption. We assessed whether the reduced folate carrier [NM_194255.1: c.80A-->G (i.e., p.His27Arg)] (RFC-1) polymorphism was associated with placental abruption, and evaluated if maternal smoking modified the association between plasma folate and abruption. Data were derived from the New Jersey-Placental Abruption Study--a multicenter, case-control study of placental abruption (2002-2007). Maternal DNA was assayed for the RFC-1 c.80A-->G polymorphism using a PCR-dependent diagnostic test. Maternal folate (nmol/l) was assessed from maternal plasma, collected immediately following delivery. Due to assay limitations, folate levels at > or =60 nmol/l were truncated at 60 nmol/l. Therefore, case-control differences in folate were assessed from censored log-normal regression models following adjustment for potential confounders. Distribution of the mutant allele (G) of the RFC-1 c.80A-->G polymorphism was similar between cases (52.3%; n = 196) and controls (50.5%; n = 191), as was the homozygous mutant (G/G) genotype (OR 1.1, 95% CI 0.6-2.2). In a sub-sample of 136 cases and 140 controls, maternal plasma folate levels (mean +/- standard error) corrected for assay detection limits were similar between placental abruption cases (63.6 +/- 5.1 nmol/l) and controls (58.3 +/- 4.7 nmol/l; P = 0.270), and maternal smoking did not modify this relationship (interaction P = 0.169). We did not detect any association between the RFC-1 c.80A-->G polymorphism and placental abruption, nor was an association between plasma folate and abruption risk evident. These findings may be the consequence of high prevalence of prenatal multivitamin and folate supplementation in this population (over 80%). It is therefore not surprising that folate deficiency may be rare and that the RFC-1 c.80A-->G polymorphism is less biologically significant for placental abruption.

Does the addition of fibrates to statin therapy have a favorable risk to benefit ratio?

Statins effectively lower low-density lipoprotein cholesterol levels and the risk of cardiovascular disease (CVD) events, and because of this they have become a standard treatment for dyslipidemia and atheroprevention. Unfortunately, statin monotherapy may fail to normalize high triglycerides and low high-density lipoprotein cholesterol, and it prevents only a minority of CVD events. Further treatment of lipid disorders that remain after statin monotherapy should help reduce the residual CVD risk. Fibrate monotherapy lowers high triglyceride levels, raises low high-density lipoprotein cholesterol, and reduces CVD risk; therefore, fibrates are recommended as an adjunct to statins for treatment of residual dyslipidemia and residual CVD risk. This review provides an update on the benefits and risks of fibrate monotherapy and addresses the benefits and risks of adding fibrates to statins.

Serum total homocysteine concentrations and risk of mortality from stroke and coronary heart disease in Japanese: The JACC study

Evidence for association between serum total homocysteine (tHcy) level and cardiovascular disease is limited in Asian populations. We conducted a nested case-control study under JACC Study. A total of 39,242 subjects aged 40-79 years provided serum samples at baseline surveys between 1988 and 1990. Control subjects were selected by matching for sex, age, community and year of serum storage. Serum tHcy levels were measured by high-performance liquid chromatography. During the 10-year follow-up, there were 444 deaths due to total cardiovascular disease, including 310 total stroke (131 hemorrhage and 101 ischemic strokes) and 134 coronary heart diseases. The risks of mortality from ischemic stroke, coronary heart disease, and total cardiovascular disease were significantly higher in individuals with the highest serum tHcy quartile (>or=15.3micromol/L) than in those with the lowest quartile (<10.5micromol/L); the respective multivariable odds ratios (95% CI) were 4.35 (1.12-16.9), 3.40 (1.17-9.86), and 1.68 (1.02-2.77). The multivariable odds ratios associated with a 5-micromol/L increase in tHcy were 1.49 (1.01-2.18), 2.01 (1.21-3.35), and 1.15 (1.00-1.32), respectively. High serum tHcy levels were associated with increased mortality from ischemic stroke, coronary heart disease and total cardiovascular disease among Japanese.

Is There a Role for Fibrates in the Management of Dyslipidemia in the Metabolic Syndrome?

The outcomes of fibrate trials have varied: positive with gemfibrozil in the primary prevention Helsinki Heart Study and the secondary prevention VA-HIT trial; positive with reservations in the primary prevention WHO trial (clofibrate); and mixed with bezafibrate in the secondary prevention BIP study and with fenofibrate in the combined primary and secondary prevention FIELD study. Overall, the mixed results, combined with potential for adverse effects when given in combination with statins, have limited the use of these fibrates as cardioprotective agents. However, post hoc analyses of several of the fibrate studies have shown that people with features of the metabolic syndrome, particularly overweight people with high plasma triglyceride levels and low levels of HDL cholesterol, derive a disproportionately large reduction in cardiovascular events when treated with these agents. Thus, there is a strong case for the use of a fibrate to reduce the cardiovascular risk in overweight people with high triglyceride and low HDL-C. However, it should be noted that such people also have their cardiovascular risk reduced by statin therapy. It remains to be determined whether the combination of a fibrate plus statin reduces the risk beyond that achieved with a statin alone.

Associations between 2 polymorphisms in the methylenetetrahydrofolate reductase gene and placental abruption

OBJECTIVE

Heritable thrombophilias have been implicated as a potential cause of abruption by vascular disruption at the uteroplacental interface. Polymorphisms of the methylenetetrahydrofolate reductase (MTHFR) gene have been linked to vascular complications outside of pregnancy, which includes stroke. Given the underlying thrombotic nature of abruption, we hypothesized that polymorphisms in the MTHFR gene are associated with abruption.

STUDY DESIGN

We examined 2 variants in MTHFR: 677C-->T and 1298A-->C in genomic DNA extracted from maternal blood from the New Jersey-Placental Abruption Study, an ongoing, multicenter case-controlled study. We identified 195 women with a clinical diagnosis of abruption (cases) and 189 control subjects who were matched on race/ethnicity and parity. We assessed allele and genotype frequencies and their associations with abruption risk after adjusting for confounders through multivariable logistic regression analysis.

RESULTS

The wild-type allele (C) frequency of the 677C-->T variant of MTHFR among cases and control subjects was 69.0% and 64.3%, respectively; the wild-type allele (A) of the 1298A-->C variant was 75.9% and 79.4%, respectively. Distributions of the 677C-->T alleles among control subjects violated the Hardy-Weinberg equilibrium (P = .007); distributions of the 1298A-->C alleles were in equilibrium (P = .825). In comparison to the wild-type genotype (C/C), the homozygous mutant form (T/T) of 677C-->T was not associated with abruption (odds ratio, 0.60; 95% confidence interval [CI], 0.33-1.18). Similarly, the homozygous mutant form (C/C) of the 1298A-->C polymorphism was distributed equally between cases and control subjects (odds ratio, 2.28; 95% CI, 0.82-6.35). Plasma homocysteine and vitamin B12, but not folate, concentrations were elevated in cases compared with control subjects among women with the wild-type genotype of MTHFR 677C-->T (P = .039 for homocysteine; P = .048 for B12; P = .224 for folate).

CONCLUSION

In this population, neither heterozygosity nor homozygosity for the 677C-->T and 1298A-->C variants in MTHFR was associated with placental abruption.

Cardiac synchronous and dys-synchronous remodeling in diabetes mellitus

Glucose-mediated impairment of homocysteine (Hcy) metabolism and decrease in renal clearance contribute to hyperhomocysteinemia (HHcy) in diabetes. The Hcy induces oxidative stress, inversely relates to the expression of peroxisome proliferators activated receptor (PPAR), and contributes to diabetic complications. Extracellular matrix (ECM) functionally links the endothelium to the myocyte and is important for cardiac synchronization. However, in diabetes and hyperhomocysteinemia, a "disconnection" is caused by activated matrix metalloproteinase with subsequent accumulation of oxidized matrix (fibrosis) between the endothelium and myocyte (E-M). This contributes to "endothelial-myocyte uncoupling," attenuation of cardiac synchrony, leading to diastolic heart failure (DHF), and cardiac dys-synchronizatrion. The decreased levels of thioredoxin and peroxiredoxin and cardiac tissue inhibitor of metalloproteinase are in response to antagonizing PPARgamma.

[Case-control study evaluating the incidence of hyperhomocysteinemia in cancer patients in an internal medicine department]

PURPOSE

Cancer is a cause of venous thromboembolism. However, the physiopathology remains unknown. Hyperhomocysteinemia could be a promoting factor.

METHOD

We built a case-control study of 65 patients followed for 2 years to compare levels of homocystéinémie in cancer bearing patients with that in matched cancer free control patients.

RESULTS

Fifty per cent of cancer bearing patients had significantly increased blood serum levels of homocystéine (P=0.006). This increase did not correlate with any deficiency in blood serum levels of folate or vitamin B12.

CONCLUSION

High levels of homocystéinémie could be linked to tumor proliferation.

Polymorphisms in methionine synthase reductase and betaine-homocysteine S-methyltransferase genes: risk of placental abruption

OBJECTIVES

Methionine synthase reductase (MTRR) and betaine-homocysteine S-methyltransferase (BHMT) are two enzymes that regulate homocysteine metabolism. Elevated homocysteine (hyperhomocysteinemia) is associated with adverse pregnancy outcomes and vascular disease. We assessed whether polymorphisms in MTRR (66A-->G; I22M) and BHMT (742G-->A; R239Q) were associated with abruption. We further evaluated whether homocysteine levels differed between cases and controls for MTRR and BHMT genotypes.

METHODS

Data were derived from the New Jersey Placental Abruption Study (NJ-PAS)-an ongoing, multicenter, case-control study since August 2002. Women with a clinical diagnosis of abruption were recruited as incident cases (n=196), and controls (n=191) were matched to cases based on maternal race/ethnicity and parity. Total plasma homocysteine concentrations were evaluated in a subset of 136 cases and 136 controls. DNA was genotyped for the MTRR and BHMT polymorphisms.

RESULTS

Frequencies of the minor allele of MTRR were 40.8% and 42.2% in cases and controls, respectively (adjusted OR 0.79, 95% CI 0.45, 1.40). The corresponding rates for BHMT were 33.9% and 31.7%, respectively (adjusted OR 1.93, 95% CI 0.99, 4.09). Distributions for the homozygous mutant form of MTRR were similar between cases and controls (OR 1.18, 95% CI 0.62, 2.24). The rate of homozygous mutant BHMT genotype was 2.8-fold (OR 2.82, 95% CI 1.84, 4.97) higher in cases than controls. Stratification of analyses based on maternal race did not reveal any patterns in association.

CONCLUSIONS

In this population, there was an association between the homozygous mutant form of BHMT (742G-->A) polymorphism and increased risk for placental abruption.

Safety considerations with fibrate therapy

Fibrates are an important class of drugs for the management of dyslipidemia. This class of drugs is generally well tolerated but is infrequently associated with several safety issues. Fibrates, most likely by an effect mediated by peroxisome proliferator-activated receptor-alpha, may reversibly increase creatinine and homocysteine but are not associated with an increased risk for renal failure in clinical trials. Fibrates are associated with a slightly increased risk (<1.0%) for myopathy, cholelithiasis, and venous thrombosis. In clinical trials, patients without elevated triglycerides and/or low high-density lipoprotein cholesterol (HDL) levels, fibrates are associated with an increase in noncardiovascular mortality. In combination with statins, gemfibrozil generally should be avoided. The preferred option is fenofibrate, which is not associated with an inhibition of statin metabolism. Clinicians are advised to measure serum creatinine before fibrate use and adjust the dose accordingly for renal impairment. Routine monitoring of creatinine is not required, but if a patient has a clinically important increase in creatinine, and other potential causes of creatinine increase have been excluded, consideration should be given to discontinuing fibrate therapy or reducing the dose.

Fenofibrate

Fenofibrate is a fibric acid derivative indicated for use in the treatment of primary hypercholesterolaemia, mixed dyslipidaemia and hypertriglyceridaemia in adults who have not responded to nonpharmacological measures. Its lipid-modifying effects are mediated by activation of peroxisome proliferator-activated receptor-alpha. Fenofibrate also has nonlipid (i.e. pleiotropic) effects (e.g. it reduces fibrinogen, C-reactive protein and uric acid levels and improves flow-mediated dilatation). Fenofibrate improves lipid levels (in particular triglyceride [TG] and high-density lipoprotein-cholesterol [HDL-C] levels) in patients with primary dyslipidaemia. Its lipid-lowering profile means that fenofibrate is particularly well suited for use in atherogenic dyslipidaemia (characterised by high TG levels, low HDL-C levels and small, dense low-density lipoprotein [LDL] particles), which is commonly seen in patients with the metabolic syndrome and type 2 diabetes mellitus. Indeed, fenofibrate improves the components of atherogenic dyslipidaemia in patients with these conditions, including a shift from small, dense LDL particles to larger, more buoyant LDL particles. Greater improvements in lipid levels are seen when fenofibrate is administered in combination with an HMG-CoA reductase inhibitor (statin) or in combination with ezetimibe, compared with monotherapy with these agents. In the DAIS study, fenofibrate significantly slowed the angiographic progression of focal coronary atherosclerosis in patients with type 2 diabetes. In terms of clinical outcomes, although no significant reduction in the risk of coronary events was seen with fenofibrate in the FIELD trial in patients with type 2 diabetes, treatment was associated with a significantly reduced risk of total cardiovascular disease (CVD) events, primarily through the prevention of non-fatal myocardial infarction and coronary revascularisation. Subgroup analyses revealed significant reductions in total CVD events and coronary heart disease events in patients with no previous CVD, suggesting a potential role for primary prevention with fenofibrate in patients with early type 2 diabetes. Improvements were also seen in microvascular outcomes with fenofibrate in the FIELD trial. Fenofibrate is generally well tolerated, both as monotherapy and when administered in combination with a statin. Combination therapy with fenofibrate plus a statin appears to be associated with a low risk of rhabdomyolysis; no cases of rhabdomyolysis were reported in patients receiving such therapy in the FIELD trial. Thus, fenofibrate is a valuable lipid-lowering agent, particularly in patients with atherogenic dyslipidaemia.

N-3 fatty acid supplementation decreases plasma homocysteine in diabetic dyslipidemia treated with statin–fibrate combination

The aim of this study was to study the effect of adding polyunsaturated fatty acid (PUFA) n-3 or placebo (containing oleic acid) to a combined statin-fibrate treatment on plasma lipoproteins, lipoperoxidation, glucose homeostasis, total homocysteine (tHcy) and microalbuminuria (MA) in patients with diabetic dyslipidemia (DDL). Twenty-four patients, who did not fulfill the recommended target lipid values with combined hypolipidemic therapy (pravastatin 20 mg+micronized fenofibrate 200 mg daily), were supplemented with 3.6 g PUFA n-3 daily for 3 months or placebo (olive oil) for the next 3 months. The concentrations of plasma lipids, fatty acid (FA) profiles of phosphatidylcholine (PC), cholesteryl esters (CE) and triglycerides (TG), tHcy levels, concentrations of conjugated dienes (CD) in low-density lipoprotein (LDL), and MA were determined in baseline state, after the PUFA n-3 and placebo treatment period. Supplementation with PUFA n-3 led to a significant decrease in plasma tHcy (-29%, P < .01) and TG (-28%, P < .05) levels, as well as to a significant decrease in MA (-24%, P < .05). The decrease in MA correlated significantly with the increase in total PUFA n-3 (r = -.509, P < or = .05) and docosahexaenoic acid (r = -.52, P < .01) in TG. The concentrations of CD in LDL increased significantly (+15%, P < .05). The supplementation with PUFA n-3 to the combined statin-fibrate treatment in patients with DDL decreased the TG and tHcy levels as well as MA. It could lead to decreased risk of atherothrombosis and delay of diabetic nephropathy onset and progression.

Pioglitazone mitigates renal glomerular vascular changes in high-fat, high-calorie-induced type 2 diabetes mellitus

Our hypothesis is that impairment of peroxisome proliferator-activated receptor-gamma (PPARgamma) initiates renal dysfunction by increasing renal glomerular matrix metalloproteinase-2 (MMP-2) activity because of increased renal homocysteine (Hcy) and decreased nitric oxide (NO) levels. C57BL/6J mice were made diabetic (D) by being fed a high-fat-calorie diet, and an increase in PPARgamma activity was induced by adding pioglitazone (Pi) to the diet. Mice were grouped as follows: normal calorie diet (N), D, N+Pi, and D+Pi (n = 6/group). The glomerular filtration rate (GFR), renal artery blood flow and pressure, and plasma glucose were measured. Renal glomeruli and preglomerular arterioles were isolated. Plasma and glomerular levels of NO, Hcy, and MMP activity were measured. The contractile response to phenylephrine and the dilatation response to acetylcholine in renal arteriolar rings were measured in a tissue myobath. In N, D, N+Pi, and D+Pi groups, respectively, GFR was 9.4 +/- 1.2, 3.9 +/- 1.1, 9.2 +/- 1.6, and 8.4 +/- 1.4 microl x min(-1) x g body wt(-1). Renovascular resistance was 140 +/- 3, 367 +/- 21, 161 +/- 9, and 153 +/- 10 mmHg x ml x min(-1). Levels of Hcy were increased from 5.8 +/- 1.5 in the N to 18.0 +/- 4.0 micromol/l in the D group. Glomerular levels of MMP-2 were increased in D mice compared with N mice, and there was no change in levels of MMP-9. Treatment with Pi ameliorated glomerular levels of MMP-2 and Hcy in the D group. Renal artery ring contraction and relaxation by phenylephrine and acetylcholine, respectively, were attenuated in the D groups compared with the N groups. Results suggest that a PPARgamma agonist ameliorates preglomerular arteriole remodeling in diabetes by decreasing tissue levels of Hcy and MMP-2 activity and increasing NO.

Homocysteine-dependent cardiac remodeling and endothelial-myocyte coupling in a 2 kidney, 1 clip Goldblatt hypertension mouse model

Accumulation of interstitial collagen (fibrosis) between the endothelium and myocytes is one of the hallmarks of cardiac failure in renovascular hypertension (RVH). Renal insufficiency increases plasma homocysteine (Hcy), and levels of peroxisome proliferator-activated receptor-γ (PPAR-γ) are inversely related to plasma Hcy levels. We hypothesize that in RVH, accumulation of collagen between the endothelium and myocytes leads to endothelial-myocyte disconnection and uncoupling, in part, by hyperhomocysteinemia. Furthermore, we hypothesize that Hcy increases reactive oxygen species, generates nitrotyrosine, activates latent matrix metalloproteinase, and decreases the levels of endothelial nitric oxide in response to antagonizing PPAR-γ. To create RVH in mice, the left renal artery was clipped with 0.4-mm sliver wire for the 2 kidney, 1 clip (2K1C) method. Sham surgery was used as a control. To induce PPAR-γ, 8 µg/mL ciglitazone (CZ) was administered to drinking water 2 days before surgery and continued for 4 weeks. Mice were grouped as 2K1C, sham, 2K1C+CZ, or sham+CZ (n = 6 in each group). Plasma Hcy increased 2-fold in the 2K1C-treated group (p < 0.05) as compared with the sham, and CZ had no effect on Hcy levels as compared to the 2K1C-treated group. Hcy binding in cardiac tissue homogenates decreased in the 2K1C-treated group but was substantially higher in the CZ-treated group. Cardiac reactive oxygen species levels were increased and endothelial nitric oxide were decreased in the 2K1C-treated group. Matrix metalloproteinase-2 and -9 activities were increased in the 2K1C-treated group compared with the control. Levels of cardiac inhibitor of metallopoteinase were decreased, whereas there was no change in tissue inhibitor of metalloproteinase-1 expression in the 2K1C-treated group vs. the sham-treated group. Collagen and nitrotyrosine levels were increased in the 2K1C-treated group, but mice treated with CZ showed lower levels comparatively. Cardiac transferase deoxyuridine nick-end labeling-positive cells were increased, and muscle cells were impaired in the 2K1C-treated mice vs. the sham-control mice. This was associated with decreased acetylcholine and bradykinin responses, which suggests endothelial-myocyte uncoupling in 2K1C-treated mice. Our results suggest that fibrosis between the endothelium and myocytes leads to an endothelial-myocyte disconnection and uncoupling by Hcy accumulation secondary to increased reactive oxygen species, nitrotyrosine, matrix metalloproteinase, and decreased endothelial nitric oxide in response to antagonizing PPAR-γ. Key words: ECM, collagen, elastin, cystathione β synthase, nitric oxide, arteriosclerosis, renal mechanism.

Comparative effects of lipid-lowering therapies

The pharmacologic regulation of lipid metabolism in patients with dyslipidemia is unequivocally associated with significant reductions in risk for cardiovascular morbidity and mortality. A number of therapeutic drug classes have been developed in an effort to ever more precisely and intensively modulate lipid metabolism. Statins, fibrates, ezetimibe, and niacin exert their effects via different mechanisms and afford physicians the opportunity to beneficially impact multiple pathways in patients. When used alone or in combination, these drugs decrease risk for the development and progression of atherosclerotic disease. There are strong clinical trial data to support of the use of lipid-lowering therapies in the settings of both primary and secondary prevention. This article (1) discusses the mechanisms of action of antilipidemic medications, (2) reviews dosing regimens and the pharmacokinetic differences among drugs of the same class, (3) assesses risk for drug interactions, and (4) reviews the clinical trial evidence used to support the use of particular antilipidemic medications in specific physiologic settings. The incidence of dyslipidemia is rising worldwide. This trend portends an ever-growing need for the aggressive and judicious use of different antilipidemic medication(s) in patients at risk for all forms of atherosclerotic vascular disease.

Effect of fenofibrate-mediated increase in plasma homocysteine on the progression of coronary artery disease in type 2 diabetes mellitus

The Diabetes Atherosclerosis Intervention Study (DAIS) examined the effects of fenofibrate or placebo on the progression of coronary artery disease (CAD) in 418 type 2 diabetic subjects with dyslipidemia. Fenofibrate use was associated with a 6% increase in high-density lipoprotein cholesterol, a 28% decrease in triglycerides, a 5% decrease in low-density lipoprotein cholesterol, and a 55% increase in plasma homocysteine (tHcy). The purpose of the present study was to determine whether this increase in tHcy in the fenofibrate group was associated with CAD progression or with clinical events. The increase in tHcy with fenofibrate (n = 207) was not related to changes in factors known to modulate tHcy levels (serum levels of Vitamin B(12), folate, or renal function). CAD was quantified by angiography at baseline and after a minimum of 3 years of therapy with fenofibrate or placebo. The primary end point was change in mean segment diameter (MSD), minimal lumen diameter, and percent stenosis. Baseline tHcy level was correlated with percent diameter stenosis (r = 0.111, p = 0.028). Baseline, but not end-of-study elevated tHcy levels, decreased the beneficial effect of fenofibrate. Unexpectedly, the final tHcy levels correlated negatively with CAD progression (r = -0.111, p = 0.031) in the overall group. In the fenofibrate group, there was no significant correlation between tHcy and minimal lumen diameter (r = -0.135, p = 0.069), or percent stenosis. An increase in tHcy levels was not correlated with adverse clinical events in the fenofibrate group. This analysis of the the DAIS reveals that the fenofibrate-mediated increase in tHcy levels does not attenuate the beneficial effects of fenofibrate on CAD progression or clinical events.

Homocysteine induces vascular endothelial growth factor expression in differentiated THP-1 macrophages

Hyperhomocysteinemia has been reported to be an independent risk factor for atherosclerosis and atherothrombosis. However, the molecular mechanism by which hyperhomocysteinemia can lead to atherosclerosis and atherothrombosis has not been completely described. Vascular endothelial growth factor (VEGF) has been proposed to play an important role in the progression of atherosclerosis. In the present study, we hypothesized that hyperhomocysteinemia might be associated with VEGF expression in atherosclerotic lesions. We investigated VEGF mRNA expression and VEGF secretion by homocysteine (Hcy) in differentiated THP-1 macrophages. As a result, it has been revealed that VEGF mRNA was upregulated by Hcy in a dose- and time-dependent manner in THP-1 macrophages with the increase in VEGF secretion. Importantly, other sulfur compounds, such as methionine and cysteine, showed no effect on VEGF expression, indicating that homocysteine specifically induced VEGF. Our findings suggest that hyperhomocysteinemia could promote the development of atherosclerotic lesions through VEGF induction in macrophages.

Comparative effects of atorvastatin, simvastatin, and fenofibrate on serum homocysteine levels in patients with primary hyperlipidemia

Hyperhomocysteinemia is regarded as an independent risk factor for cardiovascular disease. Lipid-lowering agents, such as fibrates, can modify homocysteine levels. However, less is known about the effect of statin therapy on homocysteine. The authors compared the effects of atorvastatin (40 mg/day), simvastatin (40 mg/day), and micronized fenofibrate (200 mg/day) on the serum concentrations of total homocysteine, vitamin B12, and folic acid in patients with primary hyperlipidemia. A total of 128 patients with primary hyperlipidemia (total cholesterol > 240 mg/dL and triglycerides < 350 mg/dL) were assigned to atorvastatin, simvastatin, or fenofibrate. Serum lipid and metabolic parameters were measured at baseline and at 6 and 12 weeks of treatment. Homocysteine correlated positively with serum creatinine and uric acid levels and inversely with serum folic acid levels. All treatment modalities reduced total, low-density lipoprotein (LDL) cholesterol, and triglyceride concentrations. High-density lipoprotein (HDL) cholesterol levels significantly increased only in the fenofibrate-treated patients (47.9 +/- 12.5 vs. 50.7 +/- 12.6 vs. 51.2 +/- 12.8 mg/dL, p < 0.01). Atorvastatin and fenofibrate treatment resulted in a significant reduction of serum uric acid levels (5.3 +/- 1.6 vs. 4.9 +/- 1.4 vs. 4.8 +/- 1.4 mg/dL, p < 0.0001 for atorvastatin; 5.6 +/- 1.6 vs. 4.3 +/- 1.4 vs. 4.4 +/- 1.4 mg/dL, p < 0.0001 for fenofibrate). Homocysteine levels were significantly increased only by fenofibrate (10.3 +/- 3.3 vs. 14.1 +/- 3.8 vs. 14.2 +/- 3.6 microU/L, p < 0.001) but did not change from baseline following statin treatment. Neither statins nor fenofibrate had any effect on serum vitamin B12 and folic acid levels. In contrast to fenofibrate, therapeutic dosages of atorvastatin and simvastatin have a neutral effect on serum homocysteine levels, which is in favor of their "cardioprotective" properties.

Effect of folic acid on fenofibrate-induced elevation of homocysteine and cysteine

BACKGROUND

An elevated total plasma homocysteine (tHcy) level is considered to be an independent risk factor for atherosclerosis. It has been reported that lipid-lowering therapy with fibric acid derivatives (fibrates) increases tHcy and total plasma cysteine (tCys) levels. The aim of this study was to determine whether therapy with folic acid, a potent tHcy-lowering agent, could modify the fenofibrate-induced elevation of plasma aminothiols.

METHODS

Patients with combined hyperlipidemia (n = 37) were randomized to receive 9 weeks of treatment with micronized fenofibrate 200 mg/day (F group) or fenofibrate 200 mg/day plus folic acid 10 mg/every other day (F+F group). tCys and tHcy levels were determined before and after the therapy with high performance liquid chromatography.

RESULTS

The tHcy level increased significantly in the F group by 51.3% and in the F+F group by 14.6% (between-group difference P =.001). Total plasma cysteine (tCys) increased similarly after both treatments (P =.72). The serum creatinine level increased in the F group by 20.7% and in F+F group only by 9.8% (P =.04). The increase of tHcy level in F group correlated with an increase of tCys and creatinine levels (r = 0.74 and 0.64, respectively). The effects on the lipid profile did not differ by treatment group.

CONCLUSIONS

Folic acid effectively reduces the fenofibrate-induced elevation of tHcy and creatinine, but it does not affect the elevation of the tCys. Folic acid has neutral effect on the lipid-lowering action of fenofibrate. Clinical efficacy of fenofibrate might be improved by folic acid coadministration.

Update on fenofibrate

Fenofibrate is a fibric acid derivative that has been marketed since the mid-1970's (1998 in the United States). Its active metabolite, fenofibric acid, is responsible for the primary pharmacodynamic effects of the drug: reductions in total plasma cholesterol, low density lipoprotein cholesterol, triglycerides, and very low-density lipoprotein concentrations and increases in high-density lipoprotein cholesterol and apolipoproteins AI and AII concentrations. These effects are mediated by activation of peroxisome proliferator-activated receptor-alpha (PPAR(alpha)). The drug has broad spectrum utility, with documented efficacy in Fredrickson types IIa, IIb, III, IV, and V hyperlipidemias. Fenofibrate is well tolerated, with digestive and musculoskeletal side effects similar to those of other fibrates. Results of the initial cardiovascular morbidity/mortality outcomes study with fenofibrate (known as DAIS [Diabetes Atherosclerosis Intervention Study]) were encouraging vis-à-vis slowing of atherosclerotic progression in the coronary vasculature of type II diabetics. The results of other ongoing outcome trials are eagerly awaited. These results will help to establish the overall place of fenofibrate in the hypolipidemic armamentarium.

Combined effect of coenzyme Q10 and fenofibrate on forearm microcirculatory function in type 2 diabetes

Arteriopathy is the principal complication of type 2 diabetes mellitus. It develops from endothelial dysfunction, which we have hypothesised occurs in diabetes primarily as a consequence of dyslipidaemia and oxidative stress. Fenofibrate and CoQ may improve endothelial function by regulating dyslipidaemia and oxidative stress, respectively. We therefore aimed to assess the independent and combined effects of fenofibrate and coenzyme Q(10) (CoQ) on endothelium-dependent and endothelium-independent vasodilator function of the forearm microcirculation in type 2 diabetes. Eighty dyslipidaemic type 2 diabetics were randomized to receive fenofibrate (200 mg/daily), CoQ (200 mg/daily), fenofibrate plus CoQ (200+200 mg daily), or placebo for 12 weeks. Forearm microcirculatory function was assessed with venous occlusion plethysmography during the infusion of acetylcholine (ACh), bradykinin (BK), sodium nitroprusside (SNP) and N(G)-monomethyl-L-arginine (L-NMMA) into the brachial artery. Blood flow responses were calculated as area under the curve (AUC). Fenofibrate significantly lowered plasma cholesterol, triglyceride and fibrinogen (P<0.001), and elevated HDL-cholesterol and homocysteine (P<0.001). CoQ did not change plasma isoprostanes, but significantly lowered systolic blood pressure and HbA(1c) (P<0.05). Fenofibrate plus CoQ significantly improved (P<0.05) the AUC for ACh, BK and SNP without significantly altering basal responses to L-NMMA. Fenofibrate or CoQ alone did not significantly alter blood flow responses. Improvements in blood flow were independent of changes in plasma lipids, blood pressure, homocysteine and isoprostanes, but were correlated (P=0.013) with HbA(1c). In conclusion, in this factorial trial we found that only the combination of fenofibrate and CoQ markedly improved endothelial and non-endothelial forearm vasodilator function in dyslipidemic type 2 diabetic patients. The favourable vascular effect of this therapeutic combination could be due to increase in the bioactivity of and/or responses to endothelium-derived relaxing factors, including nitric oxide, and this may entail synergistic stimulation of peroxisome proliferator-activated receptors.

Fenofibrate-induced hyperhomocysteinaemia: clinical implications and management

Fenofibrate is among the drugs of choice for treatment of hypertriglyceridaemia and low levels of high-density lipoprotein (HDL)-cholesterol, both recognised as risk factors for cardiovascular disease. Recently, a number of studies have shown an elevation of homocysteine levels with fenofibrate or bezafibrate therapy. Homocysteine is an atherogenic amino acid derived from the methionine cycle. At present, the underlying mechanism for this elevation has not been elucidated. While deterioration of vitamin status does not seem to be involved, impairment of renal function or changes in creatine metabolism are regarded as probable mechanisms. In patients not receiving lipid-lowering drugs, vitamin supplementation with folic acid and vitamin B12 effectively reduces the plasma homocysteine level. Two studies have shown that addition of folic acid or a vitamin combination to fenofibrate prevented most of the homocysteine increase associated with fenofibrate. Although the consequence of increasing homocysteine levels for cardiovascular risk has not been proven at present, it has to be considered that fenofibrate will be given for long-term treatment. Therefore, addition of folic acid and vitamin B12 to fenofibrate can be recommended to prevent the increase of homocysteine associated with fenofibrate, or treatment could be changed to gemfibrozil, which does not increase plasma homocysteine levels.

Peroxisome proliferator ameliorates endothelial dysfunction in a murine model of hyperhomocysteinemia

To test the hypothesis that endothelial dysfunction in hyperhomocysteinemia was due to increased levels of nitrotyrosine and matrix metalloproteinase (MMP) activity in response to antagonism of peroxisome proliferator-activated receptor-alpha (PPAR-alpha), cystathionine beta-synthase (CBS) -/+ mice were bred, tail tissue was analyzed for genotype by PCR, and tail vein blood was analyzed for homocysteine (Hcy) by spectrofluorometry. To induce PPAR-alpha, mice were administered 8 microg/ml of ciprofibrate (CF) and grouped: 1) wild type (WT), 2) WT + CF, 3) CBS, 4) CBS + CF (n = 6 in each group). In these four groups of mice, plasma Hcy was 3.0 +/- 0.2, 2.5 +/- 1.2, 15.2 +/- 2.6 (P < 0.05 compared with WT), 11.0 +/- 2.9 micromol/l. Mouse urinary protein was 110 +/- 11, 86 +/- 6, 179 +/- 13, 127 +/- 9 microg.day(-1). kg(-1) by Bio-Rad dye binding assay. Aortic nitrotyrosine was 0.099 +/- 0.012, 0.024 +/- 0.004, 0.132 +/- 0.024 (P < 0.01 compared with WT), 0.05 +/- 0.01 (scan unit) by Western analysis. MMP-2 activity was 0.053 +/- 0.010, 0.024 +/- 0.002, 0.039 +/- 0.009, 0.017 +/- 0.006 (scan unit) by zymography. MMP-9 was specifically induced in CBS -/+ mice and inhibited by CF treatment. Systolic blood pressure (SPB) was 90 +/- 2, 88 +/- 16, 104 +/- 8 (P < 0.05 compared with WT), 96 +/- 3 mmHg. Aortic wall stress [(SPB. radius(2)/wall thickness)/2(radius + wall thickness)] was 10.2 +/- 1.9, 9.7 +/- 0.2, 16.6 +/- 0.8 (P < 0.05 compared with WT), 13.1 +/- 2.1 dyn/cm(2). The results suggest that Hcy increased aortic wall stress by increasing nitrotyrosine and MMP-9 activity.

Role of nitric oxide in matrix remodeling in diabetes and heart failure

Accumulation of oxidized-matrix between the endothelium and myocytes is associated with endocardial endothelial (EE) dysfunction in diabetes and heart failure. High levels of circulating homocysteine (Hcy) have been demonstrated in diabetes mellitus (DM). These high levels of Hcy (hyperhomocysteinemia, HHcy) have a negative correlation with peroxisome proliferator activated receptor (PPAR) expression. Studies have demonstrated that Hcy decreases bioavailability of endothelial nitric oxide (eNO), generates nitrotyrosine, and activates latent matrix metalloproteinase (MMP), instigating EE dysfunction. PPAR ligands ameliorate endothelial dysfunction and DM. In addition Hcy competes with PPAR ligands. The understanding of molecular, cellular, and extracellular mechanisms by which Hcy amplifies DM will have therapeutic ramifications for diabetic cardiomyopathy.

Fenofibrate in the treatment of dyslipidemia: a review of the data as they relate to the new suprabioavailable tablet formulation

BACKGROUND

The fibric acid derivative fenofibrate is indicated as an adjunct to dietary modification in adults with primary hypercholesterolemia or mixed dyslipidemia (types IIa and IIb hyperlipidemia, Fredrickson classification) to reduce levels of low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC), triglycerides (TG), and apolipoprotein (apo) B, and to increase levels of high-density lipoprotein cholesterol (HDL-C) and apo A. It is also indicated as adjunctive therapy to diet for the treatment of hypertriglyceridemia (types IV and V hyperlipidemia). Initially approved in the United States in a micronized capsule formulation, fenofibrate is now available in a new "suprabioavailable" tablet formulation that has increased bioavailability, achieving equivalent plasma concentrations at lower doses. The 67- and 200-mg micronized capsules can be considered equivalent to the 54- and 160-mg suprabioavailable tablets, respectively.

OBJECTIVE

This paper reviews the pharmacologic properties, clinical usefulness, and safety profile of fenofibrate in the management of dyslipidemias.

METHODS

Recent studies, abstracts, reviews, and consensus statements published in the English-language literature were identified through searches of MEDLINE (1966-January 2002), International Pharmaceutical Abstracts (1970-January 2002), and PharmaProjects (1990-January 2002) using the search terms fenofibrate, fibrates, hyperlipidemia, hypertriglyceridemia, and dyslipidemia.

RESULTS

Fenofibrate is well absorbed after oral administration, with peak plasma levels attained in 6 to 8 hours. The absolute bioavailability of fenofibrate cannot be determined due to its being virtually insoluble in aqueous media suitable for injection; however, after oral administration of a single dose of radiolabeled fenofibrate, approximately 60% of the dose appeared in urine, primarily as fenofibric acid and its glucuronated conjugate, and approximately 25% was excreted in the feces. The apparent volume of distribution is 0.89 L/kg in healthy volunteers, and protein binding is approximately 99% in healthy and hyperlipidemic patients. Neither fenofibrate nor fenofibric acid appears to undergo significant oxidative metabolism in vivo. Fenofibric acid has a half-life of 20 hours. Fenofibrate is effective in lowering TG levels and increasing HDL-C levels. Its LDL-C-lowering effect is greater than that of gemfibrozil. Adverse effects of fenofibrate appear to be similar to those of other fibrates, including gastrointestinal symptoms, cholelithiasis, hepatitis, myositis, and rash. Fenofibrate therapy has been associated with increases in serum aminotransferase levels, and clinical monitoring of these markers of liver function should be performed regularly.

CONCLUSIONS

Fenofibrate is effective in reducing levels of TG, TC, and LDL-C, and increasing levels of HDL-C in patients with dyslipidemias. Its efficacy and tolerability in the treatment of hypertriglyceridemia and combined hyperlipidemia have been demonstrated in numerous clinical trials. Its use is accompanied by a low incidence of adverse effects and laboratory abnormalities. Fenofibrate protects against coronary heart disease not only through its effects on lipid parameters but also by producing alterations in LDL structure and, possibly, alterations in the various hemostatic parameters. Its uricosuric property may prove to be a useful adjunctive attribute.

Comparison of gemfibrozil and fenofibrate in patients with dyslipidemic coronary heart disease

STUDY OBJECTIVE

To compare the lipid-lowering effects of gemfibrozil and fenofibrate in patients with dyslipidemic coronary heart disease.

DESIGN

Open label, fixed-dosage, retrospective-prospective, one-way crossover from gemfibrozil to fenofibrate.

SETTING

University-affiliated outpatient clinics.

PATIENTS

Eighty patients with coronary heart disease with a baseline low-density lipoprotein cholesterol (LDL) level above 130 mg/dl or a triglyceride level of 200 mg/dl or higher who had been receiving gemfibrozil 600 mg twice/day. Thirty-nine (49%) patients had received concomitant therapy with a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor (statin) for a minimum of 9 months.

INTERVENTION

All patients received gemfibrozil 600 mg twice/day for at least 3 months before being switched to fenofibrate 201 mg/day. Patients receiving concomitant statin therapy before crossover continued the statin at the same dosage after crossover. Before crossover, a fasting lipid profile was determined and patients were queried about the side effects of lipid-lowering therapy. A repeat fasting lipid profile was obtained 12 weeks after the crossover.

MEASUREMENTS AND MAIN RESULTS

Patients were stratified into those receiving versus those not receiving concomitant statin therapy. In both of these groups, fenofibrate was associated with significantly greater reductions in total cholesterol, LDL, and triglycerides than gemfibrozil (all p < 0.001). In addition, fenofibrate was associated with a significantly greater increase in high-density lipoprotein cholesterol (HDL) than gemfibrozil (p < 0.001). No patients reported new-onset adverse effects after the crossover.

CONCLUSIONS

Compared with gemfibrozil, fenofibrate produced significantly greater reductions in total cholesterol, LDL, and triglycerides and significantly greater increases in HDL. These changes were evident in patients receiving and not receiving concomitant statin therapy.

Peroxisome proliferators compete and ameliorate Hcy-mediated endocardial endothelial cell activation

To determine whether homocysteine (Hcy)-mediated activation of endocardial endothelial (EE) cells is ameliorated by peroxisome proliferator-activated receptor (PPAR), we isolated EE cells from mouse endocardium. Matrix metalloproteinase (MMP) activity and intercellular adhesion molecule (ICAM)-1 in EE cells were measured in the presence and absence of Hcy, and ciprofibrate (CF; PPAR-alpha agonist) or 15-deoxy-Delta(12,14)-prostaglandin J(2) (PGJ(2); PPAR-gamma agonist) by zymography and Western blot analyses, respectively. Results suggest that Hcy-mediated MMP activation and ICAM-1 expression are ameliorated by CF and PGJ(2). To test the hypothesis that Hcy competes with other ligands for binding to PPARalpha and -gamma, we prepared cardiac nuclear extracts. Extracts were loaded onto an Hcy-cellulose affinity column. Bound proteins were eluted with CF and PGJ(2). To determine conformational changes in PPAR upon binding to Hcy, we measured PPAR fluorescence at 334 nm. Dose-dependent increase in PPAR fluorescence demonstrated a primary binding affinity of 0.32 +/- 0.06 microM. There was dose-dependent quenching of PPAR fluorescence by fluorescamine-homocysteine (F-Hcy). PPAR-alpha fluorescence quenching was abrogated by the addition of CF but not by PGJ(2). PPAR-gamma fluorescence quenching was abrogated by the addition of PGJ(2) but not by CF. These results suggest that Hcy competes with CF and PGJ(2) for binding to PPAR-alpha and -gamma, respectively, indicating a role of PPAR in amelioration of Hcy-mediated EE dysfunction.

Polymorphisms in the methylenetetrahydrofolate reductase gene: clinical consequences

5,10-Methylenetetrahydrofolate reductase (MTHFR) plays a key role in folate metabolism by channeling one-carbon units between nucleotide synthesis and methylation reactions. Severe enzyme deficiency leads to hyperhomocysteinemia and homocystinuria, with altered folate distribution and a phenotype that is characterized by damage to the nervous and vascular systems. Two frequent polymorphisms in the human MTHFR gene confer moderate functional impairment of MTHFR activity for homozygous mutant individuals. The C to T change at nucleotide position 677, whose functional consequences are dependent on folate status, has been extensively studied for its clinical consequences. A second polymorphism, an A to C change at nucleotide position 1298, is not as well characterized. Still equivocal are associations between MTHFR polymorphisms and vascular arteriosclerotic or thrombotic disease. Neural tube defects and pregnancy complications appear to be linked to impaired MTHFR function. Colonic cancer and acute leukemia, however, appear to be less frequent in individuals homozygous for the 677T polymorphism.MTHFR polymorphisms influence the homocysteine-lowering effect of folates and could modify the pharmacodynamics of antifolates and many other drugs whose metabolism, biochemical effects, or target structures require methylation reactions. However, only preliminary evidence exists for gene-drug interactions. This review summarizes the biochemical basis and clinical evidence for interactions between MTHFR polymorphisms and several disease entities, as well as potential interactions with drug therapies. Future investigations of MTHFR in disease should consider the influence of other variants of functionally-related genes as well as the medication regimen of the patients. Animal models for genetic deficiencies in folate metabolism will likely play a greater role in our understanding of folate-dependent disorders.

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.

Homocysteine and cardiovascular disease in diabetes mellitus

BACKGROUND

Patients with diabetes mellitus (DM) have 2- to 6-fold increase in the prevalence of cardiovascular disease (CVD) compared to non-DM subjects. Epidemiological data show that DM is synergic with other conventional risk factors. Total plasma homocysteine (tHcy) is an emerging CVD risk factor. We reviewed the literature to explore the relation between tHcy and CVD in patients with DM.

METHODS

We searched the MEDLINE database for articles on homocysteine, DM and CVD published from January 1991 to October 2000.

RESULTS

The mean plasma tHcy level is usually low or normal in DM patients, except when nephropathy is present. Levels in that case tend to be higher than in non-DM patients. An independent association with tHcy and CVD was shown in retrospective studies, for DM patients. Prospective studies showed an association between elevated tHcy and all cause mortality in DM patients. In general, the association between elevated levels of tHcy and the outcome was stronger than in non-DM individuals, for all types of study.

DISCUSSION

To date, there are no prospective work that specifically examined the relationship between levels of tHcy and the presence of CVD in the DM population. Nor are there studies to show that treating elevated tHcy results in a reduction of CVD events. Such studies are ongoing. Nevertheless, since hyperhomocysteinemia is potentially reversible with vitamin therapy, interaction of DM with high levels tHcy on the risk of CVD may have consequences with regard to management of primary and secondary prevention in DM patients who are at particularly high risk of CVD events.