Fibrates, dyslipoproteinaemia and cardiovascular disease

MASLD/MASH and type 2 diabetes: Two sides of the same coin? From single PPAR to pan-PPAR agonists

Type 2 diabetes (T2D) and metabolic dysfunction-associated steatotic liver disease (MASLD), mainly related to nutrition and lack of physical activity, are both very common conditions, share several disease pathways and clinical manifestations, and increasingly co-occur with disease progression. Insulin resistance is an upstream node in the biology of both conditions and triggers liver parenchymal injury, inflammation and fibrosis. Peroxisome proliferator-activated receptor (PPAR) nuclear transcription factors are master regulators of energy homeostasis - insulin signaling in liver, adipose and skeletal muscle tissue - and affect immune and fibrogenesis pathways. Among distinct yet overlapping effects, PPARα regulates lipid metabolism and energy expenditure, PPARβ/δ has anti-inflammatory effects and increases glucose uptake by skeletal muscle, while PPARγ improves insulin sensitivity and exerts direct antifibrotic effects on hepatic stellate cells. Together PPARs thus represent pharmacological targets across the entire biology of MASH. Single PPAR agonists are approved for hypertriglyceridemia (PPARα) and T2D (PPARγ), but these, as well as dual PPAR agonists, have shown mixed results as anti-MASH treatments in clinical trials. Agonists of all three PPAR isoforms have the potential to improve the full disease spectrum from insulin resistance to fibrosis, and correspondingly to improve cardiometabolic and hepatic health, as has been shown (phase II data) with the pan-PPAR agonist lanifibranor.

Circadian clock and lipid metabolism disorders: a potential therapeutic strategy for cancer

Recent research has emphasized the interaction between the circadian clock and lipid metabolism, particularly in relation to tumors. This review aims to explore how the circadian clock regulates lipid metabolism and its impact on carcinogenesis. Specifically, targeting key enzymes involved in fatty acid synthesis (SREBP, ACLY, ACC, FASN, and SCD) has been identified as a potential strategy for cancer therapy. By disrupting these enzymes, it may be possible to inhibit tumor growth by interfering with lipid metabolism. Transcription factors, like SREBP play a significant role in regulating fatty acid synthesis which is influenced by circadian clock genes such as BMAL1, REV-ERB and DEC. This suggests a strong connection between fatty acid synthesis and the circadian clock. Therefore, successful combination therapy should target fatty acid synthesis in addition to considering the timing and duration of drug use. Ultimately, personalized chronotherapy can enhance drug efficacy in cancer treatment and achieve treatment goals.

Treating NASH by targeting peroxisome proliferator-activated receptors

The pathophysiology of non-alcoholic steatohepatitis (NASH) encompasses a complex set of intra- and extrahepatic driving mechanisms, involving numerous metabolic, inflammatory, vascular and fibrogenic pathways. The peroxisome proliferator-activated receptors (PPARs) α, β/δ and γ belong to the nuclear receptor family of ligand-activated transcription factors. Activated PPARs modulate target tissue transcriptomic profiles, enabling the body's adaptation to changing nutritional, metabolic and inflammatory environments. PPARs hence regulate several pathways involved in NASH pathogenesis. Whereas single PPAR agonists exert robust anti-NASH activity in several preclinical models, their clinical effects on histological endpoints of NASH resolution and fibrosis regression appear more modest. Simultaneous activation of several PPAR isotypes across different organs and within-organ cell types, resulting in pleiotropic actions, enhances the therapeutic potential of PPAR agonists as pharmacological agents for NASH and NASH-related hepatic and extrahepatic morbidity, with some compounds having already shown clinical efficacy on histological endpoints.

Review article: vascular effects of PPARs in the context of NASH

BACKGROUND

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors known to regulate glucose and fatty acid metabolism, inflammation, endothelial function and fibrosis. PPAR isoforms have been extensively studied in metabolic diseases, including type 2 diabetes and cardiovascular diseases. Recent data extend the key role of PPARs to liver diseases coursing with vascular dysfunction, including nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH).

AIM

This review summarises and discusses the pathobiological role of PPARs in cardiovascular diseases with a special focus on their impact and therapeutic potential in NAFLD and NASH.

RESULTS AND CONCLUSIONS

PPARs may be attractive for the treatment of NASH due to their liver-specific effects but also because of their efficacy in improving cardiovascular outcomes, which may later impact liver disease. Assessment of cardiovascular disease in the context of NASH trials is, therefore, of the utmost importance, both from a safety and efficacy perspective.

Transcriptional Regulation of Hepatic Autophagy by Nuclear Receptors

Autophagy is an adaptive self-eating process involved in degradation of various cellular components such as carbohydrates, lipids, proteins, and organelles. Its activity plays an essential role in tissue homeostasis and systemic metabolism in response to diverse challenges, including nutrient depletion, pathogen invasion, and accumulations of toxic materials. Therefore, autophagy dysfunctions are intimately associated with many human diseases such as cancer, neurodegeneration, obesity, diabetes, infection, and aging. Although its acute post-translational regulation is well described, recent studies have also shown that autophagy can be controlled at the transcriptional and post-transcriptional levels. Nuclear receptors (NRs) are in general ligand-dependent transcription factors consisting of 48 members in humans. These receptors extensively control transcription of a variety of genes involved in development, metabolism, and inflammation. In this review, we discuss the roles and mechanisms of NRs in an aspect of transcriptional regulation of hepatic autophagy, and how the NR-driven autophagy pathway can be harnessed to treat various liver diseases.

Adrenoceptor-related decrease in serum triglycerides is independent of PPARα activation

Adrenoceptor (AR)-linked pathways belong to the major components of the stress response system and are associated with the pathophysiology of diseases within the spectrum of metabolic syndrome. In this study, the role of adrenoceptor stimulation in serum triglyceride (TG) regulation in mice was investigated. For this purpose, α₁ -ARs were activated with phenylephrine (PH) and β_1/2 -ARs with isoprenaline (ISOP). Both AR agonists markedly reduced serum TG levels independently of PPARα activation. These drugs also significantly activated the hormone-sensitive lipase in the white adipose tissue indicating increased mobilization of TGs in this tissue. In addition, PH and ISOP up-regulated Lpl, Nr4A, Dgat1, Mttp, Aadac and Cd36 genes, critical in TG regulation, whereas the observed decrease in serum TG levels was independent of the hepatic very low-density lipoprotein (VLDL)-TG secretion. Interestingly, PH and ISOP also inactivated the hepatic insulin/PI3k/AKT/FoxO1 signaling pathway, holding a critical role in the regulation of genes involved in TG synthesis. Taken together, the findings of the present study indicate that stimulation of α₁ - and β_1/2 -ARs markedly reduced serum TG steady-state levels as a result of alterations in TG synthesis, uptake, transport, hydrolysis, metabolism and clearance, an effect induced by PPARα independent mechanisms.

The olive constituent oleuropein, as a PPARα agonist, markedly reduces serum triglycerides

Oleuropein (OLE), a main constituent of olive, exhibits antioxidant and hypolipidemic effects, while it reduces the infarct size in chow- and cholesterol-fed rabbits. Peroxisome proliferator-activated receptor α (PPARα) has essential roles in the control of lipid metabolism and energy homeostasis. This study focused on the mechanisms underlying the hypolipidemic activity of OLE and, specifically, on the role of PPARα activation in the OLE-induced effect. Theoretical approach using Molecular Docking Simulations and luciferase reporter gene assay indicated that OLE is a ligand of PPARα. The effect of OLE (100 mg/kg, p.o., per day, ×6 weeks) on serum triglyceride (TG) and cholesterol levels was also assessed in adult male wild-type and Ppara-null mice. Molecular Docking Simulations, Luciferase reporter gene assay and gene expression analysis indicated that OLE is a PPARα agonist that up-regulates several PPARα target genes in the liver. This effect was associated with a significant reduction of serum TG and cholesterol levels. In contrast, OLE had no effect in Ppara-null mice, indicating a direct involvement of PPARα in the OLE-induced serum TG and cholesterol reduction. Activation of hormone-sensitive lipase in the white adipose tissue (WAT) and the liver of wild-type mice and up-regulation of several hepatic factors involved in TG uptake, transport, metabolism and clearance may also contribute in the OLE-induced TG reduction. In summary, OLE has a beneficial effect on TG homeostasis via PPARα activation. OLE also activates the hormone sensitive lipase in the WAT and liver and up-regulates several hepatic genes with essential roles in TG homeostasis.

5-aminosalicylic acid improves lipid profile in mice fed a high-fat cholesterol diet through its dual effects on intestinal PPARγ and PPARα

Obesity is associated with a series of metabolic complications, including dyslipidemia and insulin resistance (IR) that lack effective therapies. In recent years, intestinal inflammation has been suggested to contribute to obesity related metabolic syndrome and targeting gut inflammation with 5-ASA improves diet induced IR, however, its role in dyslipidemia is unknown and has never been explored. In the present study, we reported for the first time that administration of 5-ASA for 12 weeks significantly improved lipid profile by repressing plasma triglycerides and free cholesterol levels in mice fed high-fat cholesterol diet (HFC). In addition, liver lipids were significantly reduced by 5-ASA treatment in HFC-fed mice. Mechanistically, anti-inflammatory genes peroxisome proliferator-activated receptor-γ (Pparγ) and M2 marker, such as Mrc1 and Ym1, were remarkably upregulated, while pro-inflammation gene monocyte chemoattractant protein-1 (Mcp-1) were downregulated in small intestine of mice treated by 5-ASA. Further, 5-ASA improved gastrointestinal barrier by increasing the expression of the tight junction marker ZO-1. 5-ASA also enhanced cholesterol translocation by elevating genes expression of Npc1l1 and Abcg5/8. Moreover, mice fed HFC 5-ASA expressed increased Pparα in small intestinal and its target genes function in lipid oxidation and hydrolysis were remarkable elevated. Taken together, we reported a novel role of 5-ASA which may serve as a therapy target intestinal inflammation induced dyslipidemia.

Implications of a peroxisome proliferator-activated receptor alpha (PPARα) ligand clofibrate in breast cancer

Inflammatory and invasive breast cancers are aggressive and require better understanding for the development of new treatments and more accurate prognosis. Here, we detected high expression of PPARα in human primary inflammatory (SUM149PT) and highly invasive (SUM1315MO2) breast cancer cells, and tissue sections of human breast cancer. PPARα ligands are clinically used to treat dyslipidemia. Among lipid lowering drugs clofibrate, fenofibrate and WY14643, clofibrate showed high chemo-sensitivity towards breast cancer cells. Clofibrate treatment significantly induced PPARα DNA binding activity, and remarkably reduced cyclooxygenase-2/PGE2 and 5-lipoxygenase/LTB4 inflammatory pathways. Clofibrate treatment reduced the proliferation of breast cancer cells probably by inhibiting NF-κB and ERK1/2 activation, reducing cyclinD1, cyclinA, cyclinE, and inducing pro-apoptotic P21 levels. Surprisingly, the expression of lipogenic pathway genes including SREBP-1c (sterol regulatory element-binding protein-1c), HMG-CoA synthase, SPTLC1 (serine palmitoyltransferase long-chain), and Acyl-CoA oxidase (ACO) decreased with a concurrent increase in fatty acid oxidation genes such as CPT-1a (carnitine palmitoyltransferase 1a) and SREBP-2 (Sterol regulatory element-binding protein-2). Clofibrate treatment induced secretion of free fatty acids and effectively decreased the level of phosphorylated active form of fatty acid synthase (FASN), an enzyme catalyzing de novo synthesis of fatty acids. High level of coactivators steroid receptor coactivator-1 (SRC-1) and histone acetylase CBP-300 (CREB binding protein-300) were observed in the nuclear complexes of clofibrate treated breast cancer cells. These findings implicate that stimulating PPARα by safe, well-tolerated, and clinically approved clofibrate may provide a safer and more effective strategy to target the signaling, lipogenic, and inflammatory pathways in aggressive forms of breast cancer.

Nutrient-sensing nuclear receptors PPARα and FXR control liver energy balance

The nuclear receptors PPARα (encoded by NR1C1) and farnesoid X receptor (FXR, encoded by NR1H4) are activated in the liver in the fasted and fed state, respectively. PPARα activation induces fatty acid oxidation, while FXR controls bile acid homeostasis, but both nuclear receptors also regulate numerous other metabolic pathways relevant to liver energy balance. Here we review evidence that they function coordinately to control key nutrient pathways, including fatty acid oxidation and gluconeogenesis in the fasted state and lipogenesis and glycolysis in the fed state. We have also recently reported that these receptors have mutually antagonistic impacts on autophagy, which is induced by PPARα but suppressed by FXR. Secretion of multiple blood proteins is a major drain on liver energy and nutrient resources, and we present preliminary evidence that the liver secretome may be directly suppressed by PPARα, but induced by FXR. Finally, previous studies demonstrated a striking deficiency in bile acid levels in malnourished mice that is consistent with results in malnourished children. We present evidence that hepatic targets of PPARα and FXR are dysregulated in chronic undernutrition. We conclude that PPARα and FXR function coordinately to integrate liver energy balance.

Exploration and analysis of drug modes of action through feature integration

Identifying drug modes of action (MoA) is of paramount importance for having a good grasp of drug indications in clinical tests.

Dual Peroxisome Proliferator-Activated Receptor-alpha/gamma Agonists : In the Treatment of Type 2 Diabetes Mellitus and the Metabolic Syndrome

The metabolic syndrome consists of a combination of cardiovascular risk factors that include hyperglycemia with or without type 2 diabetes mellitus, visceral obesity, elevated blood pressure, and atherogenic dyslipidemia. These interrelated disorders and their associated lipotoxicity, oxidative stress, and inflammatory state predispose to a constellation of cardiovascular conditions leading to high risk of heart attack, stroke, renal failure, blindness, and lower extremity amputation. Visceral obesity, a prime risk factor for type 2 diabetes and a major component of the metabolic syndrome, potentiates atherogenesis, atherosclerosis, organ lipotoxicity, and oxidative tissue damage.Peroxisome proliferator-activated receptors (PPARs) are relatively recently discovered nuclear transcription factors that are modulated by dietary fatty acids, including the essential polyunsaturated fatty acids, arachidonic acid and its metabolites, and are essential to the control of energy metabolism. Of the three PPAR isoforms (alpha, gamma, and delta), synthetic pharmaceutical ligands that activate PPARalpha (the antidyslipidemic fibric acid derivatives ['fibrates']) and PPARgamma (the antidiabetic thiazolidinediones) have been studied extensively. Recently developed dual PPARalpha/gamma agonists may combine the therapeutic effects of these drugs, creating the expectation of greater efficacy, and perhaps other advantages in the treatment of type 2 diabetes and the metabolic syndrome. However, thiazolidinediones are hampered by adverse effects related to increased weight gain and fluid overload. It remains to be seen whether the dual PPARalpha/gamma agonists currently under development have similar limitations. Nevertheless, existing clinical data imply that the combined effects of thiazolidinediones and fibrates are likely to be emulated by dual PPARalpha/gamma agonists, providing superior efficacy to these classes for the treatment of type 2 diabetes, the metabolic syndrome, and their cardiovascular and other end-organ complications.

Familial Hypercholesterolemia: a Review of the Natural History, Diagnosis, and Management

Familial hypercholesterolemia (FH) is an inherited disorder of lipid metabolism characterized by premature cardiovascular disease. It is one of the most common metabolic disorders affecting humans. There are two clinical manifestations: the milder heterozygous form and more severe homozygous form. Despite posing a significant health risk, FH is inadequately diagnosed and managed. As the clinical outcome is related to the degree and duration of exposure to elevated low-density lipoprotein cholesterol (LDL-C) levels, early treatment is vital. Diagnosis can usually be made using a combination of clinical characteristics such as family history, lipid levels, and genetic testing. Mutations in the gene encoding the LDL receptor (LDLR), apolipoprotein B, the pro-protein convertase subtilisin/kexin 9 (PCSK9), and LDLR adaptor protein are the commonest abnormalities. Early identification and treatment of patients, as well as screening of relatives, helps significantly reduce the risk of premature disease. Although statins remain the first-line therapy in most cases, monotherapy is usually inadequate to control elevated LDL-C levels. Additional therapy with ezetimibe and bile acid sequestrants may be required. Newer classes of pharmacotherapy currently under investigation include lomitapide, mipomersen, and monoclonal antibodies to PCSK9. Lipoprotein apheresis may be required when multiple pharmacotherapies are inadequate, especially in the homozygous form. Effective early detection and treatment of the index individual and initiation of cascade screening will help reduce the complications associated with FH. In this article, we review the disease of FH, complexity of diagnosis and management, and the challenges faced in preventing the significant morbidity and mortality associated with it.

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

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

Metabolomics approach reveals effects of antihypertensives and lipid-lowering drugs on the human metabolism

The mechanism of antihypertensive and lipid-lowering drugs on the human organism is still not fully understood. New insights on the drugs’ action can be provided by a metabolomics-driven approach, which offers a detailed view of the physiological state of an organism. Here, we report a metabolome-wide association study with 295 metabolites in human serum from 1,762 participants of the KORA F4 (Cooperative Health Research in the Region of Augsburg) study population. Our intent was to find variations of metabolite concentrations related to the intake of various drug classes and—based on the associations found—to generate new hypotheses about on-target as well as off-target effects of these drugs. In total, we found 41 significant associations for the drug classes investigated: For beta-blockers (11 associations), angiotensin-converting enzyme (ACE) inhibitors (four assoc.), diuretics (seven assoc.), statins (ten assoc.), and fibrates (nine assoc.) the top hits were pyroglutamine, phenylalanylphenylalanine, pseudouridine, 1-arachidonoylglycerophosphocholine, and 2-hydroxyisobutyrate, respectively. For beta-blockers we observed significant associations with metabolite concentrations that are indicative of drug side-effects, such as increased serotonin and decreased free fatty acid levels. Intake of ACE inhibitors and statins associated with metabolites that provide insight into the action of the drug itself on its target, such as an association of ACE inhibitors with des-Arg(9)-bradykinin and aspartylphenylalanine, a substrate and a product of the drug-inhibited ACE. The intake of statins which reduce blood cholesterol levels, resulted in changes in the concentration of metabolites of the biosynthesis as well as of the degradation of cholesterol. Fibrates showed the strongest association with 2-hydroxyisobutyrate which might be a breakdown product of fenofibrate and, thus, a possible marker for the degradation of this drug in the human organism. The analysis of diuretics showed a heterogeneous picture that is difficult to interpret. Taken together, our results provide a basis for a deeper functional understanding of the action and side-effects of antihypertensive and lipid-lowering drugs in the general population.

New insights into the molecular mechanism of intestinal fatty acid absorption

BACKGROUND

Dietary fat is one of the most important energy sources of all the nutrients. Fatty acids, stored as triacylglycerols (also called triglycerides) in the body, are an important reservoir of stored energy and derived primarily from animal fats and vegetable oils.

DESIGN

Although the molecular mechanisms for the transport of water-insoluble amphipathic fatty acids across cell membranes have been debated for many years, it is now believed that the dominant means for intestinal fatty acid uptake is via membrane-associated fatty acid-binding proteins, that is, fatty acid transporters on the apical membrane of enterocytes.

RESULTS

These findings indicate that intestinal fatty acid absorption is a multistep process that is regulated by multiple genes at the enterocyte level, and intestinal fatty acid absorption efficiency could be determined by factors influencing intraluminal fatty acid molecules across the brush border membrane of enterocytes. To facilitate research on intestinal, hepatic and plasma triacylglycerol metabolism, it is imperative to establish standard protocols for precisely and accurately measuring the efficiency of intestinal fatty acid absorption in humans and animal models. In this review, we will discuss the chemical structure and nomenclature of fatty acids and summarize recent progress in investigating the molecular mechanisms underlying the intestinal absorption of fatty acids, with a particular emphasis on the physical chemistry of intestinal lipids and the molecular physiology of intestinal fatty acid transporters.

CONCLUSIONS

A better understanding of the molecular mechanism of intestinal fatty acid absorption should lead to novel approaches to the treatment and the prevention of fatty acid-related metabolic diseases that are prevalent worldwide.

Effects of probiotic Lactobacillus rhamnosus GG and Propionibacterium freudenreichii ssp. shermanii JS supplementation on intestinal and systemic markers of inflammation in ApoE*3Leiden mice consuming a high-fat diet

A high-fat diet disturbs the composition and function of the gut microbiota and generates local gut-associated and also systemic responses. Intestinal mast cells, for their part, secrete mediators which play a role in the orchestration of physiological and immunological functions of the intestine. Probiotic bacteria, again, help to maintain the homeostasis of the gut microbiota by protecting the gut epithelium and regulating the local immune system. In the present study, we explored the effects of two probiotic bacteria, Lactobacillus rhamnosus GG (GG) and Propionibacterium freudenreichii spp. shermanii JS (PJS), on high fat-fed ApoE*3Leiden mice by estimating the mast cell numbers and the immunoreactivity of TNF-α and IL-10 in the intestine, as well as plasma levels of several markers of inflammation and parameters of lipid metabolism. We found that mice that received GG and PJS exhibited significantly lower numbers of intestinal mast cells compared with control mice. PJS lowered intestinal immunoreactivity of TNF-α, while GG increased intestinal IL-10. PJS was also observed to lower the plasma levels of markers of inflammation including vascular cell adhesion molecule 1, and also the amount of gonadal adipose tissue. GG lowered alanine aminotransferase, a marker of hepatocellular activation. Collectively, these data demonstrate that probiotic GG and PJS tend to down-regulate both intestinal and systemic pro-inflammatory changes induced by a high-fat diet in this humanised mouse model.

Regulation of gene transcription by fatty acids

Dietary fat is well recognised as an important macronutrient that has major effects on growth, development and health of all animals including humans. The amount and type of fat in the diet impacts on many aspects of metabolism including lipoprotein pathways, lipid synthesis and oxidation, adipocyte differentiation and cholesterol metabolism. It has become increasingly apparent that many of these effects may be due to direct modulation of expression of key genes through the interaction of fatty acids with certain transcription factors. Peroxisome proliferator-activated receptors (PPARs), the liver X receptors (LXRs), hepatic nuclear factor 4 (HNF-4) and sterol regulatory binding proteins (SREBPs) represent four such factors. This review focuses on emerging evidence that the activity of these transcription factors are regulated by fatty acids and the interactions between them may be responsible for many of the effects of fatty acids on metabolism and the development of chronic disease.

Effect of pharmacological treatments for diabetes on homocysteine

Hyperhomocysteinemia is a well-established risk factor for cardiovascular disease. The association of hyperhomocysteinemia with diabetes mellitus is complex and may explain some of the risk of CVD in diabetics not explained by traditional risk factors. Both modifiable and non-modifiable factors interact with homocysteine metabolism and determine the plasma homocysteine concentrations. These include genetic abnormalities, age, sex, and various nutritional and hormonal determinants, all of which play a role in atherosclerosis and accelerated peripheral and cardio-vascular disease (CVD). Several medications modulate homocysteine metabolism and hence may play a role in the pathogenesis of CVD. Changes in renal function and interference with the homocysteine metabolism account for some of these drug effects. While a few of these drugs raise plasma homocysteine concentrations, others are beneficial and may counter some of the deleterious effects of hyperhomocysteinemia. Treatment of hyperhomocysteinemia with vitamins lowers plasma homocysteine concentrations and also reverses many of these drug effects. Little data is available on the effect of this intervention on cardiovascular outcomes. This review briefly outlines the effect of various medications used in the management of type 2 diabetes mellitus and metabolic syndrome.

Efficacy, safety and tolerability of combined low-dose simvastatin-fenofibrate treatment in primary mixed hyperlipidaemia

OBJECTIVE

In order to assess the long-term (12 months) efficacy and safety of fenofibrate administered with simvastatin in the treatment of primary mixed hyperlipidaemia, we conducted a study that compared increasing dosages of these drugs in subgroups of men and women belonging to a clinical sample of out-patients.

DESIGN

This was an open study carried out in patients with primary mixed hyperlipidaemia (lipoprotein phenotype IIb) who needed a combined therapeutic approach because of their poor response to a single-drug regimen with an HMG-CoA reductase inhibitor (simvastatin). Thus, a fibrate (fenofibrate) was added to the therapy. The study lasted 12 months.

PATIENTS

Forty-five patients (mean age: 58.9 +/- 11.3 years) with primary mixed hyperlipidaemia who showed a poor response to the single-drug hypolipidaemic treatment were enrolled. Their average plasma triglyceride level was consistently above 300 mg/dL and low-density lipoprotein cholesterol (LDL-C) was over 160 mg/dL after at least 6 months of a single hypolipidaemic drug (simvastatin) regimen plus antiatherogenic dietary treatment.

INTERVENTIONS

Five patients received simvastatin 10mg once daily in addition to fenofibrate 200mg; 26 patients received simvastatin 20mg once daily plus fenofibrate 200mg; 11 patients received simvastatin 20mg once daily plus fenofibrate 300mg; and three patients received simvastatin 30mg once daily plus fenofibrate 200mg. The patients were allocated to treatment groups on the basis of their relative response to the therapy. Those making up the progressively higher agent/dose groups were the individuals at higher cardiovascular risk according to the total cholesterol and non-high-density lipoprotein cholesterol (HDL-C) values.

RESULTS

The double-drug regimen given for 12 months to four different groups, according to the different combined dosages of simvastatin and fenofibrate, resulted in a reduction in total cholesterol of 18% (p </= 0.05) to 39% (p </= 0.05), in LDL-C of 21% (not significant) to 39% (p </= 0.05) and in triglycerides of 35% (p </= 0.05) to 56% (p </= 0.01), and an increase in HDL-C of 8% (p </= 0.05) to 30% (not significant). The cardiovascular risk ratio (total cholesterol/HDL-C) at the end of the study was reduced by 33-60%, whereas the non-HDL-C decreased by 25-38%. No serious adverse effects were reported by the patients. Neither liver biochemistry nor creatine kinase serum concentration were significantly changed. Discontinuation of treatment, if necessary, in case of the occurrence of clinically subjective or objective evidence of adverse effects was assured.

CONCLUSION

The results confirmed the efficacy of the combination of fenofibrate and simvastatin. The combined therapeutic approach was shown to be safe for the treatment of primary mixed hyperlipidaemia, at least in patients with normal hepatic and renal function.

Peroxisome proliferator-activated receptorα agonists differentially regulate inhibitor of DNA binding expression in rodents and human cells

Inhibitor of DNA binding (Id2) is a helix-loop-helix (HLH) transcription factor that participates in cell differentiation and proliferation. Id2 has been linked to the development of cardiovascular diseases since thiazolidinediones, antidiabetic agents and peroxisome proliferator-activated receptor (PPAR) gamma agonists, have been reported to diminish Id2 expression in human cells. We hypothesized that PPARα activators may also alter Id2 expression. Fenofibrate diminished hepatic Id2 expression in both late pregnant and unmated rats. In 24 hour fasted rats, Id2 expression was decreased under conditions known to activate PPARα. In order to determine whether the fibrate effects were mediated by PPARα, wild-type mice and PPARα-null mice were treated with Wy-14,643 (WY). WY reduced Id2 expression in wild-type mice without an effect in PPARα-null mice. In contrast, fenofibrate induced Id2 expression after 24 hours of treatment in human hepatocarcinoma cells (HepG2). MK-886, a PPARα antagonist, did not block fenofibrate-induced activation of Id2 expression, suggesting a PPARα-independent effect was involved. These findings confirm that Id2 is a gene responsive to PPARα agonists. Like other genes (apolipoprotein A-I, apolipoprotein A-V), the opposite directional transcriptional effect in rodents and a human cell line further emphasizes that PPARα agonists have different effects in rodents and humans.

Comparative transcriptomic and metabolomic analysis of fenofibrate and fish oil treatments in mice

Elevated circulating triglycerides, which are considered a risk factor for cardiovascular disease, can be targeted by treatment with fenofibrate or fish oil. To gain insight into underlying mechanisms, we carried out a comparative transcriptomics and metabolomics analysis of the effect of 2 wk treatment with fenofibrate and fish oil in mice. Plasma triglycerides were significantly decreased by fenofibrate (−49.1%) and fish oil (−21.8%), whereas plasma cholesterol was increased by fenofibrate (+29.9%) and decreased by fish oil (−32.8%). Levels of various phospholipid species were specifically decreased by fish oil, while levels of Krebs cycle intermediates were increased specifically by fenofibrate. Plasma levels of many amino acids were altered by fenofibrate and to a lesser extent by fish oil. Both fenofibrate and fish oil upregulated genes involved in fatty acid metabolism and downregulated genes involved in blood coagulation and fibrinolysis. Significant overlap in gene regulation by fenofibrate and fish oil was observed, reflecting their property as high or low affinity agonist for peroxisome proliferator-activated receptor-α, respectively. Fenofibrate specifically downregulated genes involved in complement cascade and inflammatory response. Fish oil specifically downregulated genes involved in cholesterol and fatty acid biosynthesis and upregulated genes involved in amino acid and arachidonic acid metabolism. Taken together, the data indicate that despite being similarly potent toward modulating plasma free fatty acids, cholesterol, and triglyceride levels, fish oil causes modest changes in gene expression likely via activation of multiple mechanistic pathways, whereas fenofibrate causes pronounced gene expression changes via a single pathway, reflecting the key difference between nutritional and pharmacological intervention.

Effects of prescription omega-3-acid ethyl esters on fasting lipid profile in subjects with primary hypercholesterolemia

This double-blind, randomized crossover study investigated the effects of 6 weeks of treatment with prescription omega-3-acid ethyl esters (POM3, 4 g/day) versus placebo (soy oil) on low-density lipoprotein cholesterol (LDL-C) and other aspects of the fasting lipid profile in 31 men and women with primary, isolated hypercholesterolemia (LDL-C 130-220 mg/dL and triglycerides less than 150 mg/dL while free of lipid-altering therapies). Mean ± standard error of the mean baseline concentrations of total cholesterol, LDL-C, high-density lipoprotein cholesterol (HDL-C), very-low-density lipoprotein cholesterol, and triglycerides were 229 ± 3, 146 ± 3, 60 ± 2, 23 ± 2, and 113 ± 8 mg/dL, respectively. POM3 produced a modest increase from baseline in LDL-C (3.4%) versus the placebo response (-0.7%, P = 0.010). Significant changes (P < 0.05) for POM3 (placebo-corrected) were observed for very-low-density lipoprotein cholesterol (-18.8%), triglycerides (-18.7%), and HDL-C (3.3%). Nuclear magnetic resonance-determined very-low-density lipoprotein particle concentration and size and HDL particle concentration decreased significantly more with POM3 versus placebo, whereas LDL and HDL particle sizes increased significantly more with POM3 versus placebo. Total cholesterol, non-HDL-C, apolipoproteins A1 and B, and LDL particle concentration responses did not differ between treatments. These results did not confirm the hypothesis that POM3 treatment would lower LDL-C in primary, isolated hypercholesterolemia. Effects on other variables were consistent with prior results in mixed dyslipidemia.

Scavenger receptor class B member 1 protein: hepatic regulation and its effects on lipids, reverse cholesterol transport, and atherosclerosis

Scavenger receptor class B member 1 (SR-BI, also known as SCARB1) is the primary receptor for the selective uptake of cholesterol from high-density lipoprotein (HDL). SR-BI is present in several key tissues; however, its presence and function in the liver is deemed the most relevant for protection against atherosclerosis. Cholesterol is transferred from HDL via SR-BI to the liver, which ultimately results in the excretion of cholesterol via bile and feces in what is known as the reverse cholesterol transport pathway. Much of our knowledge of SR-BI hepatic function and regulation is derived from mouse models and in vitro characterization. Multiple independent regulatory mechanisms of SR-BI have been discovered that operate at the transcriptional and post-transcriptional levels. In this review we summarize the critical discoveries relating to hepatic SR-BI cholesterol metabolism, atherosclerosis, and regulation of SR-BI, as well as alternative functions that may indirectly affect atherosclerosis.

Synthesis and antidyslipidemic activity of chalcone fibrates

A series of chalcone based PPAR-α agonists were synthesized and evaluated for their antidyslipidemic activity in high fructose high fat fed dyslipidemic Syrian golden hamsters. Most of the compounds exhibited antidyslipidemic activity. The compounds 4c and 4f have been identified as most potent antidyslipidemics. A definite structure-activity relationship was observed while varying the nature as well as the position of the substituent.

9-oxo-10(E),12(E)-Octadecadienoic acid derived from tomato is a potent PPAR α agonist to decrease triglyceride accumulation in mouse primary hepatocytes

SCOPE

Tomato is one of the most common crops worldwide and contains many beneficial compounds that improve abnormalities of lipid metabolism. However, the molecular mechanism underlying the effect of tomato on lipid metabolism is unclear. It has been commonly accepted that peroxisome proliferator-activated receptor α (PPARα) is one of the most important targets for ameliorating abnormalities of lipid metabolism. Therefore, we focused on the activation of PPARα and attempted to detect active compounds activating PPARα in tomato.

METHODS AND RESULTS

To identify such active compounds, we screened fractions of tomato extracts using PPARα luciferase reporter assay. One fraction, rechromatographed-fraction eluted in 57 min (RF57), significantly increased PPARα reporter activity, in which a single compound is detected by LC/MS analysis. On the basis of LC/MS and NMR analyses, we determined the chemical structure of the active compound in RF57 as 9-oxo-10(E),12(E)-octadecadienoic acid (9-oxo-ODA). The RF57 fraction significantly increased the mRNA expression levels of PPARα target genes involved in fatty acid oxidation and O(2) consumption in mouse primary hepatocytes. Furthermore, RF57 inhibited cellular triglyceride accumulation in the hepatocytes.

CONCLUSION

These findings suggest that tomatoes containing 9-oxo-ODA that acts on PPARα are valuable for ameliorating abnormalities of lipid metabolism.

Review article: omega-3 fatty acids - a promising novel therapy for non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease affects 10-35% of the adult population worldwide; there is no consensus on its treatment. Omega-3 fatty acids have proven benefits for hyperlipidaemia and cardiovascular disease, and have recently been suggested as a treatment for non-alcoholic fatty liver disease.

AIMS

To review the evidence base for omega-3 fatty acids in non-alcoholic fatty liver disease and critically appraise the literature relating to human trials.

METHODS

A Medline and PubMed search was performed to identify relevant literature using search terms 'omega-3', 'N-3 PUFA', 'eicosapentaenoic acid', 'docosahexaenoic acid', 'non-alcoholic fatty liver disease' and 'NAFLD'.

RESULTS

Omega-3 fatty acids are important regulators of hepatic gene transcription. Animal studies demonstrate that they reduce hepatic steatosis, improve insulin sensitivity and reduce markers of inflammation. Clinical trials in human subjects generally confirm these findings, but have significant design inadequacies.

CONCLUSIONS

Omega-3 fatty acids are a promising treatment for non-alcoholic fatty liver disease which require to be tested in randomized placebo-controlled trials.

How do we achieve optimal cardiovascular risk reduction?

Optimizing coronary heart disease (CHD) risk reduction requires the application of clinical evidence to patient care, as well as the refinement of risk assessment. Clinical evidence indicates that most patients are not treated to optimal low-density lipoprotein (LDL) cholesterol goals. Despite the efficacy of statin therapy in reducing the incidence of CHD, many treated patients still experience CHD events. Targeting other lipid factors such as high-density lipoprotein cholesterol and triglycerides may augment the risk reduction achieved by lowering LDL cholesterol. Refined global risk assessment can lead to more accurate determinations of absolute risk and to the identification both of high-risk patients needing aggressive intervention and intermediate-risk patients who appear to be at low risk. Previous global risk assessment measures failed to identify a substantial proportion of primary prevention patients who would benefit from therapy. However, revised guidelines issued by the National Cholesterol Education Program introduce new criteria for more precise risk assessment and advocate use of the Framingham scoring system to calculate absolute risk. Although intensified treatment is recommended for high-risk patients, cost considerations may limit drug therapy for some lower-risk individuals.

Pharmacogenetic association of the APOA1/C3/A4/A5 gene cluster and lipid responses to fenofibrate: the genetics of lipid-lowering drugs and diet network study

BACKGROUND

The apolipoproteins (APOA1/C3/A4/A5) are key components in modulating lipoprotein metabolism. It is unknown whether variants at the APOA1/C3/A4/A5 gene cluster are associated with lipid response to pharmacologic intervention.

METHODS AND RESULTS

Plasma triglycerides (TGs) and high-density lipoprotein (HDL) levels were measured in 861 Genetics of Lipid-Lowering Drugs and Diet Network study participants who underwent a 3-week fenofibrate trial. We examined 18 common single nucleotide polymorphisms (SNPs) spanning the APOA1/C3/A4/A5 genes to investigate the effects of variants at the gene cluster on lipid response to fenofibrate treatment. We found that the minor alleles of the SNPs rs3135506 (APOA5_S19W), rs5104 (APOA4_N147S), rs4520 (APOC3_G34G), and rs5128 (APOC3_3U386) were associated with enhanced TG response to fenofibrate treatment (P= 0.0004-0.018). The minor allele of SNP rs2854117 (APOC3_M482) was associated with reduced rather than enhanced TG response (P= 0.026). The SNP rs3135506 (APOA5_S19W) was associated with HDL response, with minor allele related to reduced HDL response to fenofibrate (P= 0.002). Association analyses on haplotype provided corroborative evidence to single SNP association analyses. The common haplotypes H2, H3, and H5 were significantly associated with reduced TG response to fenofibrate.

CONCLUSION

The genetic variants at APOA1/C3/A4/A5 gene cluster may be useful markers to predict response of lipid-lowering therapy with fenofibrate. Further studies to replicate/confirm our findings are warranted.

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.

Combination therapy with an HMG-CoA reductase inhibitor and a fibric acid derivative: a critical review of potential benefits and drawbacks

It has been clearly shown that lowering low density lipoprotein-cholesterol (LDL-C) [most often with an HMG-CoA reductase inhibitor] decreases the risk of a cardiovascular event. However, this risk reduction was, at most, 35% in clinical trials, meaning that many events could not be prevented. Moreover, reaching target lipid values as recommended by the current guidelines is often difficult, mainly in high-risk situations such as secondary prevention or type 2 diabetes mellitus. As the two main classes of lipid-lowering drugs (HMG-CoA reductase inhibitors and fibric acid derivatives) have complementary effects on lipid parameters, it seems logical to combine both treatments particularly in patients with combined hyperlipidemia. In fact, combination therapy with an HMG-CoA reductase inhibitor and a fibric acid derivative induces a further decrease in LDL-C levels compared with monotherapy and improves other lipid values such as high density lipoprotein-cholesterol (HDL-C) and triglyceride (TG) levels. Unfortunately, there are currently no available randomized, prospective clinical data on the reduction of the incidence of cardiovascular events with such a combination. This is mainly because the use of HMG-CoA reductase inhibitor and fibric acid derivative combinations was initially described as dangerous. It is true that such a combination increases the risk of muscle toxicity that already exists with monotherapy. Muscle toxicity can eventually lead to life-threatening rhabdomyolysis and some precautions of use are required; however, the risk seems actually lower than what has been initially reported. The use of combined therapy with an HMG-CoA reductase inhibitor and a fibric acid derivative requires the respect of some rules such as avoiding the prescription in patients with concomitant conditions like renal failure and avoiding the use of gemfibrozil as a fibric acid derivative in such a combination. It is now imperative to design clinical trials to determine the clinical efficacy and precise safety of this combined treatment especially in patients with abnormalities in every parameter of the lipid triad (LDL, HDL and TG) and a high vascular risk such as patients with type 2 diabetes mellitus.

Hypolipidemic effects of silymarin are not mediated by the peroxisome proliferator-activated receptor alpha

Silymarin is widely used in supportive therapy of liver diseases. It has been shown lately that silymarin has beneficial effects on some risk factors of atherosclerosis owing to its hypolipidemic properties. PPARalpha plays a key role in lipid metabolism and homeostasis as its target genes are involved in catabolism of fatty acids by beta-oxidation (e.g. acyl-CoA oxidase) and by omega-oxidation (e.g. cytochrome P4504A). Here we studied the possibility that hypolipidemic effects of silymarin may be mediated by PPARalpha. Rats fed with a high-cholesterol diet with either silymarin or fenofibrate (as a positive control both for PPARalpha expression as well as for lipid determination) were used. The effects of silymarin on expression of PPARalpha both at the mRNA (including selected target genes) as well as the protein level were determined. In parallel, the levels of cholesterol and triacylglycerols were determined. Our results confirmed the hypolipidemic effects of silymarin and demonstrated that these effects are probably not mediated by PPARalpha because of unchanged mRNA levels of PPARalpha target genes. Furthermore, this work shows for the first time that cholesterol itself inhibits expression of CYP4A mRNA.

PAR-5359, a well-balanced PPARalpha/gamma dual agonist, exhibits equivalent antidiabetic and hypolipidemic activities in vitro and in vivo

Peroxisome proliferator-activated receptor (PPAR) alpha and gamma are key regulators of lipid homeostasis and insulin resistance. In this study, we characterize the pharmacological profiles of PAR-5359, a dual agonist of PPARalpha and gamma with well-balanced activities. In transient transactivation assay, PAR-5359 (3-(4-(2[4-(4chloro-phenyl)-3,6-dihydro-2H-pyridin-1-yl]-ethoxy)-phenyl)-(2S)-ethoxy-propionic acid) significantly activated human and mouse PPARalpha and gamma without activating PPARdelta. In functional assays using human mesenchymal stem cells and human hepatoma HepG2 cells, PAR-5359 significantly induced adipocyte differentiation and human ApoA1 secretion, which coincided with its transactivation potencies against the corresponding human receptor subtypes. Interestingly, PAR-5359 showed equivalent potencies against the mouse receptor subtypes (alpha and gamma; 2.84 microM and 3.02 microM, respectively), which suggests the possibility that PAR-5359 could simultaneously activates each subtype of receptors subtype in under physiological conditions. In an insulin-resistant ob/ob mouse model, PAR-5359 significantly reduced plasma insulin levels, improved insulin sensitivity (HOMA-IR), and completely normalized plasma glucose levels. In a severe diabetic db/db mouse model, PAR-5359 dose-dependently reduced the plasma levels of glucose (ED(30) = 0.07 mg/kg). Furthermore, it lowered plasma levels of non HDL- (ED(30) = 0.13 mg/kg) and total cholesterol (ED(30) = 0.03 mg/kg) in high cholesterol diet-fed rats for 4 days treatment. These results suggest that PAR-5359 has the balanced activities for PPARalpha and PPARgamma in vivo as well as in vitro. And its balanced activities may render PAR-5359 as a pharmacological tool in elucidating the complex roles of PPARalpha/gamma dual agonists.

Fenofibrate improves endothelial function and decreases thrombin-activatable fibrinolysis inhibitor concentration in metabolic syndrome

Procoagulant state, inflammation, and endothelial dysfunction have been documented in metabolic syndrome. Endothelial dysfunction is a strong predictor of cardiovascular events. Studies on the association of thrombin-activatable fibrinolysis inhibitor and thrombosis are still controversial, but substantial evidence suggests that increased thrombin-activatable fibrinolysis inhibitor or thrombin-activatable fibrinolysis inhibits or protects against arterial thrombosis. This study aimed to assess concomitantly the effects of fenofibrate therapy on thrombin-activatable fibrinolysis inhibitor concentrations and endothelial functions in patients with metabolic syndrome. Twenty-five patients (16 women; mean age 50.4 +/- 7.0) were enrolled in the study. Plasma thrombin-activatable fibrinolysis inhibitor, C-reactive protein, and fibrinogen levels were measured before fenofibrate administration and after 8 weeks of fenofibrate treatment. Endothelial function was assessed by endothelial-dependent flow-mediated dilatation from brachial artery. Pretreatment (baseline) thrombin-activatable fibrinolysis inhibitor level was 52.3 (1.2-119.7) decreasing to 7.7 (0.9-51.2; P < 0.001) after 8 weeks of fibrate treatment. Endothelial functions, which were measured with flow-mediated dilatation, were significantly improved after treatment (mean flow-mediated dilatation was 6.76 +/- 2.21 at baseline and 10.66 +/- 1.17% after 8 week of fenofibrate treatment, P < 0.001). Fenofibrate decreases thrombin-activatable fibrinolysis inhibitor levels and improves endothelial function in metabolic syndrome and, thus, suggests a potential for protection against cardiovascular effects. Further studies are warranted to confirm the effects of fibrates on thrombin-activatable fibrinolysis inhibitor and for conclusive evidence on the association between thrombin-activatable fibrinolysis inhibitor and thrombosis.

Atorvastatin and fenofibrate have comparable effects on VLDL-apolipoprotein C-III kinetics in men with the metabolic syndrome

OBJECTIVE

The metabolic syndrome (MetS) is characterized by insulin resistance and dyslipidemia that may accelerate atherosclerosis. Disturbed apolipoprotein (apo) C-III metabolism may account for dyslipidemia in these subjects. Atorvastatin and fenofibrate decrease plasma apoC-III, but the underlying mechanisms are not fully understood.

METHODS AND RESULTS

The effects of atorvastatin (40 mg/d) and fenofibrate (200 mg/d) on the kinetics of very-low density lipoprotein (VLDL)-apoC-III were investigated in a crossover trial of 11 MetS men. VLDL-apoC-III kinetics were studied, after intravenous d(3)-leucine administration using gas chromatography-mass spectrometry and compartmental modeling. Compared with placebo, both atorvastatin and fenofibrate significantly decreased (P<0.001) plasma concentrations of triglyceride, apoB, apoB-48, and total apoC-III. Atorvastatin, not fenofibrate, significantly decreased plasma apoA-V concentrations (P<0.05). Both agents significantly increased the fractional catabolic rate (+32% and +30%, respectively) and reduced the production rate of VLDL-apoC-III (-20% and -24%, respectively), accounting for a significant reduction in VLDL-apoC-III concentrations (-41% and -39%, respectively). Total plasma apoC-III production rates were not significantly altered by the 2 agents. Neither treatment altered insulin resistance and body weight.

CONCLUSIONS

Both atorvastatin and fenofibrate have dual regulatory effects on VLDL-apoC-III kinetics in MetS; reduced production and increased fractional catabolism of VLDL-apoC-III may explain the triglyceride-lowering effect of these agents.

Peroxisome proliferator-activated receptor alpha activation regulates lipid metabolism in the feto-placental unit from diabetic rats

Maternal diabetes promotes an overaccumulation of lipids in the feto-placental unit and impairs feto-placental development and growth. Here, we investigated the role played by the nuclear receptor peroxisome proliferator-activated receptor (PPAR)alpha in lipid metabolism in fetuses and placentas from control and neonatal streptozotocin-induced diabetic rats. Placentas and fetuses were studied on day 13.5 of gestation. The concentrations of PPARalpha (by Western blot) and its endogenous agonist leukotriene B(4) (LTB(4)) (by enzyme immunoassay) were analysed. Placental explants and fetuses were cultured with LTB(4) or clofibrate, and then lipid metabolism analysed (concentrations and synthesis from (14)C-acetate of triglycerides, phospholipids, cholesterol and cholesteryl esters; release of glycerol and free fatty acids (FFAs)). We found that maternal diabetes led to increases in placental concentrations of triglycerides and cholesteryl esters, and fetal concentrations of phospholipids. PPARalpha agonists downregulated fetal and placental lipid concentrations in control and diabetic rats. The synthesis of lipids was reduced in the diabetic placenta but increased in fetuses from diabetic animals. PPARalpha agonists reduced the synthesis of lipids in control placenta and in the fetuses from control and diabetic rats. Glycerol and FFA release was enhanced in the diabetic placenta and in control placenta cultured with PPARalpha agonists. Maternal diabetes led to reductions in fetal and placental LTB(4) concentrations and to increases in placental PPARalpha concentrations. Overall, these data support a novel role of PPARalpha as a regulator of lipid metabolism in the feto-placental unit, relevant in maternal diabetes where fetal and placental PPARalpha, LTB(4) and lipid concentrations are altered.

The role of fibrates in the prevention of cardiovascular disease--a pooled meta-analysis of long-term randomized placebo-controlled clinical trials

BACKGROUND

Fibrates are effective antilipidemic agents with peroxisome proliferator-activated receptor agonist activity, but clinical trial data on their role in cardiovascular prevention are conflicting. We conducted a systematic review and meta-analysis of randomized clinical trials to evaluate their role in prevention of cardiovascular events.

METHODS

A total of 36,489 patients from 10 published randomized placebo-controlled trials were analyzed using the Mantel-Haenszel fixed-effects model. Odds ratios were computed for cardiovascular outcomes from data pooled from the selected trials, and statistical significance was tested using the z-test statistic (2-sided alpha error <.05).

RESULTS

Fibrates significantly reduced plasma total cholesterol and triglyceride levels by about 8% and 30%, respectively, and raised high-density lipoprotein cholesterol levels by about 9% compared with placebo. The odds of all-cause mortality tended to be higher (P = .08), and the odds of noncardiovascular mortality were significantly higher (P = .004) with the use of fibrates. However, these significant differences did not persist after exclusion of trials using clofibrate as the study drug. Fibrates did not significantly reduce the odds of cardiovascular mortality (P = .68), fatal myocardial infarction (MI) (P = .76), or stroke (P = .56). On the other hand, fibrates significantly reduced the odds of nonfatal MI by about 22% (P < .00001). The odds of developing cancer were not significantly higher with the use of fibrates (P = .98), nor were the odds of cancer-related death (P = .17).

CONCLUSIONS

In conclusion, our meta-analysis revealed that the long-term use of fibrates significantly reduces the occurrence of nonfatal MI but has no significant effect on other adverse cardiovascular outcomes.

A novel peroxisome proliferator--activated receptor alpha/gamma dual agonist ameliorates dyslipidemia and insulin resistance in prediabetic rhesus monkeys

TAK-559, a newly developed non-thiazolidinedione, activates both peroxisome proliferator-activated receptors alpha and gamma. We investigated the effects of TAK-559 on dyslipidemia and insulin resistance in nonhuman primates. Five adult male obese prediabetic rhesus monkeys were studied on vehicle and after TAK-559 treatment (0.3, 1.0, 3.0 mg/kg per day) for a total of 12 weeks. No significant changes were observed in body weight and fasting plasma glucose, total plasma cholesterol, very low-density lipoprotein-triglyceride, and low-density lipoprotein cholesterol levels. TAK-559 treatment resulted in significant elevation of circulating high-density lipoprotein (HDL) cholesterol levels, consisting of an increase in large HDL particles and a decrease in small dense HDL particles. Nuclear magnetic resonance data exhibited a less atherogenic lipoprotein profile with treatment. Plasma triglyceride and apolipoprotein B-100 levels decreased, whereas apolipoprotein A-I increased during TAK-559 treatment. Hyperinsulinemia and insulin resistance (quantitative insulin sensitivity check index and homeostasis model assessment) were significantly corrected with the highest dose of 3.0 mg/kg per day in these prediabetic monkeys. In addition, no adverse effects on representative liver function parameters were observed during the study period. These results suggest that TAK-559 had beneficial effects on lipoprotein profiles and insulin sensitivity, without any side effect on body weight, which suggests that TAK-559 may provide a potentially safe approach for delaying the onset of type 2 diabetes mellitus and may reduce the risk of cardiovascular disease. The positive effects of TAK-559 in nonhuman primates have led to further clinical trials of TAK-559 in Europe and the United States.

A Randomized Trial of the Effect of Statin and Fibrate Therapy on Arterial Function in CKD

BACKGROUND

Although patients with chronic kidney disease (CKD) are at increased risk of cardiovascular disease (CVD), the roles of lipid-modifying therapies in decreasing CVD risk are unclear. Our aim is to compare the effects of statin and fibrate therapy on arterial function as a risk marker of CVD.

STUDY DESIGN

Double-blind, randomized, placebo-controlled, parallel-group study.

SETTING & PARTICIPANTS

Ambulatory patients with stages 3 to 5 CKD.

INTERVENTION

6 weeks of atorvastatin, 40 mg/d, or gemfibrozil, 600 mg twice daily, with placebo.

OUTCOMES & MEASUREMENTS

Primary outcome was arterial function assessed by means of endothelial-dependent flow-mediated dilatation (FMD) and small-artery compliance (C2). Secondary outcomes included endothelial-independent glyceryl trinitrate-mediated dilatation (GTNMD), large-artery compliance (C1), and levels of lipids, lipoproteins, and oxidized low-density lipoprotein, as well as markers of insulin resistance and inflammation.

RESULTS

Compared with placebo, atorvastatin significantly decreased low-density lipoprotein (-52%), triglyceride (-30%), and oxidized low-density lipoprotein levels (-41%; P < 0.0001). Gemfibrozil significantly decreased triglyceride levels (-40%) and increased high-density lipoprotein levels (+20%; P < 0.0001). Neither atorvastatin nor gemfibrozil had a significant effect on markers of insulin resistance or inflammation. There was no significant change in FMD, GTNMD, or C1 with either atorvastatin or gemfibrozil. There was improvement in C2 with atorvastatin (+1.1 mL/mm Hg x 100) compared with placebo (P = 0.024), but not with gemfibrozil compared with placebo.

LIMITATIONS

Small sample size leading to inadequate power, short duration of therapy, and use of a heterogeneous group of patients with CKD and dialysis patients.

CONCLUSION

In patients with advanced CKD, atorvastatin is associated with improvement in dyslipidemia and small-artery stiffness, but not endothelial function. Gemfibrozil improves dyslipidemia, but has no effect on arterial function.

Inhibitory Effects of Micronized Fenofibrate on Carotid Atherosclerosis in Patients with Essential Hypertension

Background: The coexistence of hypertension and dyslipidemia synergistically increases the risk of cardiovascular events. We investigated the effect of the lipid-lowering agent micronized fenofibrate on inhibition of carotid atherosclerosis in patients with essential hypertension and mild hyperlipidemia.

Methods: We measured serum lipid profiles and inflammatory markers on chemistry or immune analyzers and common or internal carotid intima-media thickness (IMT) and diameter (D) by ultrasonography.

Results: Patients receiving micronized fenofibrate for 24 months in addition to antihypertensive treatment had decreased concentrations of total cholesterol, LDL-cholesterol, triglyceride, apolipoprotein B100, oxidized LDL, high-sensitivity C-reactive protein, P-selectin, and cytokines. These patients had increased concentrations of HDL-cholesterol, apolipoprotein A-I, and nitric oxide. Common carotid artery IMT (CCAIMT) and internal carotid artery IMT (ICAIMT) remained unchanged during the 24-month intervention. Moreover, the mean CCAIMT/D ratio and ICAIMT/D ratio were significantly decreased in the fenofibrate intervention group. In contrast, CCAIMT/D and ICAIMT/D ratios were increased in the control group. The incidence rates of carotid artery plaque formation and stroke in the fenofibrate intervention group were significantly lower than those in the control group.

Conclusion: The combination of antihypertensive agents with micronized fenofibrate can effectively prevent the progression of carotid atherosclerosis and reduce the incidence of stroke in patients with essential hypertension.

Investigational PPAR-gamma agonists for the treatment of Type 2 diabetes

The tremendous increase in the global prevalence of Type 2 diabetes (T2D) and its conglomeration of metabolic disorders has dramatically intensified the search for innovative therapies to fight this emerging epidemic. Over the last decade, the family of nuclear receptors, especially the peroxisome proliferator-activated receptors (PPARs), has emerged as one of the most important drug targets aimed at combating the metabolic syndrome. Consequently, compounds that activate the PPARs have served as potential therapeutics for the treatment of T2D and the metabolic anomalies associated with this disorder. This review focuses on the currently marketed compounds and also describes the discovery and development of the next generation of PPAR ligands that are under investigation for the potential treatment of T2D and the metabolic syndrome.

Triglycerides and remnant particles as risk factors for coronary artery disease

Coronary artery disease (CAD) is the largest cause of morbidity and mortality in the world. A relationship between CAD and elevated levels of low-density lipoprotein cholesterol has been established. However, risk assessment limited to low-density lipoprotein fails to identify a significant portion of patients at risk for CAD. Remnant lipoproteins, derived from very low-density lipoprotein and chylomicrons, have been considered atherogenic. Recently, a simple and reliable immunoaffinity separation method for the isolation of remnant-like particles (RLP) has been developed. It has been shown that RLP cholesterol levels are significantly correlated with CAD, and thus cellular mechanisms have been determined by which RLP cholesterol causes progression of atherosclerosis. Measurement of RLP cholesterol is useful for the assessment of risk and the evaluation of therapy in patients at risk for CAD.

Lipid-lowering drugs

Although a change in life-style is often the method of first choice for lipid lowering, lipid-lowering drugs, in general, help to control elevated levels of different forms of lipids in patients with hyperlipidemia. While one group of drugs, statins, lowers cholesterol, the other group, fibrates, is known to take care of fatty acids and triglycerides. In addition, other drugs, such as ezetimibe, colesevelam, torcetrapib, avasimibe, implitapide, and niacin are also being considered to manage hyperlipidemia. As lipids are very critical for cardiovascular diseases, these drugs reduce fatal and nonfatal cardiovascular abnormalities in the general population. However, a number of recent studies indicate that apart from their lipid-lowering activities, statins and fibrates exhibit multiple functions to modulate intracellular signaling pathways, inhibit inflammation, suppress the production of reactive oxygen species, and modulate T cell activity. Therefore, nowadays, these drugs are being considered as possible therapeutics for several forms of human disorders including cancer, autoimmunity, inflammation, and neurodegeneration. Here I discuss these applications in the light of newly discovered modes of action of these drugs.

Simultaneous determination of rosuvastatin and fenofibric acid in human plasma by LC-MS/MS with electrospray ionization: assay development, validation and application to a clinical study

A simple, sensitive and specific LC-MS/MS method for simultaneous determination of rosuvastatin (RST) and fenofibric acid (FFA) was developed and validated with 500 microL human plasma using carbamazepine as an internal standard (IS). The assay procedure involved a simple one-step liquid/liquid extraction of RST and FFA and IS from plasma into ethyl acetate. The organic layer was separated and evaporated under a gentle stream of nitrogen at 40 degrees C. The residue was reconstituted in the mobile phase and injected onto X-Terra MS C-18 column (4.6 mm x 50 mm, 5.0 microm). Separation of RST, FFA and IS was achieved with a mobile phase consisting of 0.05 M formic acid:acetonitrile (45:55, v/v) at a flow rate of 0.40 ml/min. The API-3000LC-MS/MS was operated under the multiple reaction-monitoring mode (MRM) using the electrospray ionization technique. Positive ion acquisition chromatographic run was used in the present method. Nominal retention times of RST, FFA and IS were 2.35, 4.70 and 2.32 min, respectively. Absolute recovery of RST, FFA and IS was 74, 61 and 69%, respectively. The lower limit of quantification (LLOQ) of RST and FFA was 1.00 ng/ml and 0.50 microg/ml, respectively. Response function was established for the range of concentrations 1.00-50.0 ng/ml and 0.50-20.0 microg/ml for RST and FFA, respectively, with a coefficient of determination (r2) of 0.999 for both the compounds. The inter- and intra-day precision in the measurement of RST quality control (QC) samples 5, 15, 400 and 800 ng/ml, were in the range 8.93-9.37% relative standard deviation (R.S.D.) and 1.74-16.1% R.S.D., respectively. Similarly, the inter- and intra-day precision in the measurement of FFA quality control (QC) samples 0.5, 1.5, 8.0 and 15.0 microg/ml, were in the range 9.78-11.6% relative standard deviation (R.S.D.) and 0.22-17.4% R.S.D., respectively. Accuracy in the measurement of QC samples for RST and FFA were in the range 88.1-108 and 87-115%, respectively, of the nominal values. RST and FFA were stable in the battery of stability studies, viz., bench-top, auto-sampler and freeze/thaw cycles. Stability of RST and FFA was established for 1 month at -80 degrees C. The application of the assay to a clinical study confirmed the utility of the assay.