Mechanism of antiplatelet action of hypolipidemic,antidiabetic and antihypertensive drugs by PPAR activation: PPAR agonists: New antiplatelet agents

Given the prevalence of cardiovascular disease in patients with cardiovascular risk factors (i.e., hypertension, diabetes, smoking and obesity) and that platelet activation plays an important pathogenic role in cardiovascular diseases, it is very important to identify the drugs that have multiple targets. In this sense, the present article describes the mechanism of antiplatelet action of hypolipidemic (statins and fibrates), antidiabetic (thiazolidinediones) and antihypertensive (nifedipine) drugs via peroxisome proliferator-activated receptor (PPAR) activation. The mechanism of antiplatelet action of the drugs is by direct activation of PPARs with the inhibition of cyclooxygenase-1, protein kinase C-alpha, calcium mobilization, thromboxane A2, sCD40L, platelet microparticles and cAMP-phosphodiesterase, and the stimulation of proteins kinase G and A. Thus, these observations highlight PPARs as a novel therapeutic target for the treatment and prevention of cardiovascular diseases.     

Quinoline-based derivatives of pirinixic acid as dual PPAR alpha/gamma agonists

Pirinixic acid is known for its peroxisome proliferator-activated receptor (PPAR) agonistic action. In a recent publication, we have shown that aliphatic alpha-substitution of pirinixic acid enhances both PPARalpha and PPARgamma agonism. The goal of this study was to evaluate, whether the PPAR agonism of pirinixic acid may be also maintained in quinoline-based derivatives. The present study revealed that the mere substitution of the dimethyl aniline moiety of pirinixic acid by quinoline leads to a total loss of PPARalpha/gamma agonism, whereas concomitant alpha-substitution with n-butyl or n-hexyl groups restores and even enforces PPAR activation, leading to potent dual PPARalpha/gamma agonists. In the following we report the synthesis of quinoline-based derivatives of pirinixic acid, which in a Gal4-based luciferase-reporter gene assay proved to be potent dual PPARalpha/gamma agonists. Molecular docking of compound 4 with FlexX suggests a binding mode resembling to that of tesaglitazar.     

Rodent carcinogenicity profile of the antidiabetic dual PPAR alpha and gamma agonist muraglitazar.

The carcinogenic potential of muraglitazar, a dual human peroxisome proliferator-activated receptor alpha/gamma agonist, was evaluated in 2-year studies in mice (1, 5, 20, and 40 mg/kg) and rats (1, 5, 30, and 50 mg/kg). Benign gallbladder adenomas occurred at low incidences in male mice at 20 and 40 mg/kg (area under the curve [AUC] exposures > or = 62 times human exposure at 5 mg/day) and were considered drug related due to an increased incidence of gallbladder mucosal hyperplasia at these doses. There was a dose-related increased incidence of transitional cell papilloma and carcinoma of the urinary bladder in male rats at 5, 30, and 50 mg/kg (AUC exposures > or = 8 times human exposure at 5 mg/day). At 30 and 50 mg/kg, the urinary bladder tumors were accompanied by evidence of increased urine solids. Subsequent investigative studies established that the urinary bladder carcinogenic effect was mediated by urolithiasis rather than a direct pharmacologic effect on urothelium. Incidences of subcutaneous liposarcoma in male rats and subcutaneous lipoma in female rats were increased at 50 mg/kg (AUC exposures > or = 48 times human exposure at 5 mg/day) and attributed, in part, to persistent pharmacologic stimulation of preadipocytes. Toxicologically relevant nonneoplastic changes in target tissues included thinning of cortical bone in mice and hyperplastic and metaplastic adipocyte changes in mice and rats. Considering that muraglitazar is nongenotoxic, the observed tumorigenic effects in mice and rats have no established clinical relevance since they occurred at either clinically nonrelevant exposures (gallbladder and adipose tumors) or by a species-specific mechanism (urinary bladder tumors).     

Effects of PPAR gamma agonists on cardiovascular function in obese, non-diabetic patients

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors, and when activated by their ligands, they induce perixosome proliferation. Three receptors have been identified: PPAR gamma, PPAR delta, and PPAR alpha, all with different tissue expression. PPAR gamma is predominantly expressed in adipose tissue and regulates the formation of fat cells and their function. The effect of PPAR gamma activation is to enhance the action of insulin in insulin-sensitive tissue by increasing peripheral glucose disposal and decreasing hepatic glucose production. The thiazolidinediones (TZDs) are a class of medications used for treatment and possibly the prevention of type 2 diabetes, which are potent agonists for the PPAR gamma receptor. Because the thiazolidinediones target insulin resistance, these agents may improve many of the risk factors associated with obesity and insulin resistance including dyslipidemia, hypertension, impaired fibrinolysis, and atherosclerosis. The impact of the thiazolidinediones on cardiovascular mortality is currently unclear but it appears that the thiazolidinediones exert numerous non-glycemic effects that may improve cardiovascular outcomes. Several non-TZD PPAR gamma agonists and combined PPAR gamma/alpha effect on cardiovascular disease are also being evaluated. These drugs have anti-inflammatory and vascular properties and are currently the subject of numerous studies targeting the primary and secondary prevention of macrovascular disease in patients with diabetes and insulin resistance and might be developed as anti-atherogenic agents on the basis of their actions.     

Therapeutic assessment of glucagon-like peptide-1 agonists compared with dipeptidyl peptidase IV inhibitors as potential antidiabetic drugs

The most prevalent form of diabetes is non-insulin-dependent or Type 2 diabetes. Innovative strategies to enhance insulin secretion and thereby improve glucose tolerance in patients with this type of diabetes are currently under preclinical and clinical investigation. These therapies include the applications of incretin hormones; gut hormones released postprandially that stimulate insulin secretion in pancreatic beta-cells. Because incretin actions are rapidly terminated by N-terminal cleavage of these peptide hormones by the amino-peptidase dipeptidyl peptidase IV (DPP IV, CD26), the utility of DPP IV inhibitors for the treatment of Type 2 diabetes is also under investigation. This review compares the therapeutic potential and possible side effects of metabolically stable analogues/peptide agonists of the incretin glucagon-like peptide-1 (GLP-1) with the application of DPP IV inhibitors that reduce the rate of endogenous degradation of GLP-1 and other incretins. GLP-1 analogues have been shown to be highly efficacious in the treatment of Type 2 diabetes, with minimal side effects. Of particular importance is the fact that they do not induce hypoglycaemia. However, they are currently available only in an injectable form. In contrast, DPP IV inhibitors have the clear advantage of oral application resulting in better patient compliance. Furthermore, they also potentiate the actions of other incretins normally degraded by the action of DPP IV. However, they possess more potential side effects. Taken together, both approaches offer promising new drugs for the treatment of Type 2 diabetes.     

噻唑烷二酮和芳酮酸类PPARγ激动剂三维定量构效关系研究

目的建立PPARγ激动剂-噻唑烷二酮和芳酮酸类化合物的三维定量构效关系,为设计高活性PPARγ激动剂提供结构信息。方法与结果用比较分子力场分析方法得到噻唑烷二酮和芳酮酸类化合物CoMFA模型,其交叉验证相关系数R²=0.656,非交叉验证相关系数R²=0.982,F_10,37=201.1,绝对误差SE=0.115。结论从CoMFA系数等势图中揭示芳酮酸类化合物较噻唑烷二酮类化合物活性更高的原因,提示芳酮酸类化合物与PPARγ结合时形成了不同于BRL-PPARγ复合物晶体的结合腔。     

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

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

Incretins and their analogues as new antidiabetic drugs

Glucagon-like peptide 1 (GLP-1) is a gut (incretin) hormone with multiple actions that could potentially contribute to an antidiabetic effect. This includes: (a) glucose-dependent insulinotropic actions; (b) glucagonostatic actions; (c) a reduction in appetite/promotion of satiety leading to reduced food intake and weight reduction; (d) the deceleration of gastric emptying; and (e) the stimulation of islet growth, differentiation and regeneration. Thus, multiple aspects of the type 2 diabetic phenotype can potentially be improved or even corrected by GLP-1. The native gut hormone, however, after intravenous injection or absorption from subcutaneous depots, is proteolytically degraded and eliminated from the circulation too quickly to be useful for the treatment of diabetes. GLP-1 derivatives (receptor agonists) with prolonged pharmacokinetics that promise a potential for clinical use in the near future are being developed.     

Discovery and development of selective PPARγ modulators as safe and effective antidiabetic agents

Importance of the field: PPARγ full agonists (pioglitazone and rosiglitazone) are the mainstay drugs for the treatment of type 2 diabetes; however, mechanism-based side effects have limited their full therapeutic potential. In recent years, much progress has been achieved in the discovery and development of selective PPARγ modulators (SPPARγMs) as safer alternatives to PPARγ full agonists.

Areas covered in this review: This review focuses on the preclinical and clinical data of all the SPPARγMs discovered so far, retrieved by searching PubMed, Prous Integrity database and company news updates from 1999 to date.

What the reader will gain: Here we thoroughly discuss SPPARγMs' mode of action, briefly examine new ways to identify superior SPPARγMs, and finally, compare and contrast the pharmacological and safety profile of various agents.

Take home message: The preclinical and clinical findings clearly suggest that selective PPARγ modulators have the potential to become the next generation of PPARγ agonists: effective insulin sensitizers with a superior safety profile to that of PPARγ full agonists.     

新型降糖药DPP-4抑制剂研究进展

二肽基肽酶-4 (dipeptidyl peptidase-4, DPP-4)是研发新型降糖药物的热门靶点。目前,已经发现许多DPP-4抑制剂,其中一些化合物已经进入临床应用。本文介绍了DPP-4抑制剂在降糖药中的地位及作用机制,综述了近年来不同结构类型DPP-4抑制剂的研究进展。     

苯并间二氧杂环戊烯-2,2-二羧酸衍生物的合成及其PPARδ激动活性研究

目的设计合成苯并间二氧杂环戊烯-2,2-二羧酸衍生物,并研究其PPARδ激动作用,以期发现新颖的PPARδ激动剂。方法以芳香甲酰胺和邻苯二酚为起始原料,经十余步反应制得目标化合物;并用细胞水平的转染激动实验评价目标化合物的PPARδ激动活性。结果与结论合成目标化合物15个,其结构经核磁和质谱确证。初步生物活性评价结果显示,此类化合物对PPARδ具有一定的激动作用,其中XI-c1的最大激动作用达到阳性对照药GW501516的90%。     

Potential antidiabetic drugs affecting the sensitivity of tissues to insulin

Toll-like receptors (TLRs) form a family of pattern recognition receptors that have emerged as key mediators of innate immunity. These receptors sense invading microbes and initiate the immune response. TLR-mediated inflammation is an important pathogenic link between innate immunity and a diverse panel of clinical disorders. Among the processes in which TLRs play a role are cardiovascular disorders such as cardiac ischaemia, coronary artery disease, ventricular remodelling, cancer angiogenesis or transplant rejection. From these, many important opportunities for disease modification through TLR signalling manipulation can be imagined. Their role as potential targets for therapeutic intervention is just beginning to be appreciated and this article reviews the current status of these treatment strategies for cardiovascular disease.     

应用整合方法发现新的抗癌药物和研究肿瘤转移（英文）

Cardiovascular diseases,cancer,diabetes and neurodegenerative diseases are four major life threatening and health damaging diseases that affect a large portion of the world population at present.Although these diseases differ significantly in terms of symptoms and pathogeneses,they have one thing in common-a defect in the process of programmed cell death,mainly apoptosis.For example,resistance to apoptosis results in cancer formation.On the other hand,over-activation of apoptosis in endothelial cells leads to dysfunction of vascular system which can contribute to cardiovascular diseases and complications of diabetes.Therefore,understanding what causes the defects of apoptosis in those disease-related cells will provide new insights in designing target-specific therapies to treat those diseases.In order to develop a method of realtime detection of apoptosis within the target cells,we genetically engineered a fluorescence resonance energy transfer(FRET)-based biosensor.When this biosensor is synthesized in the transfected cells,the sensor protein can detect caspase activation-mediated apoptosis by changing the color from green to blue.We have generated a bank of 32 sensor cell lines consisting of various types of cancer and non-cancerous cells.We also integrated these sensor cells into six model systems including a sensor cell-based high throughput drug screening assay,3Din vitro tumor model,co-culture system,microfluidic system,zebrafish cancer model and xenograft tumor mouse models.In this talk,I will discuss the applications of these sensor cells and model systems in discovering new anti-cancer agents and elucidating the survival mechanisms of metastatic cancer cells in circulation.