Therapeutic role of peroxisome proliferator-activated receptors in obesity, diabetes and inflammation

PPARα Regulates the Proliferation of Human Glioma Cells through miR-214 and E2F2

Peroxisome proliferator-activated receptor α (PPARα) is a member of the nuclear hormone receptor superfamily and functions as a transcription factor. Previous work showed that PPARα plays multiple roles in lipid metabolism in tissues such as cardiac and skeletal muscle, liver, and adipose tissue. Recent studies have discovered additional roles for PPARα in cell proliferation and metabolism, as well as tumor progression. PPARα is aberrantly expressed in various cancers, and activated PPARα inhibits the proliferation of some tumor cells. However, there have been no studies of PPARα in human gliomas. Here, we show that PPARα is expressed at lower levels in anaplastic gliomas and glioblastoma multiforme (GBM) tissue compared with low-grade gliomas tissue, and low expression is associated with poor patient prognosis. PPARα activates transcription of dynamin-3 opposite strand (DNMO3os), which encodes a cluster of miR-214, miR-199a-3p, and miR-199a-5p microRNAs. Of these, miR-214 is transcribed at particularly high levels. PPARα-induced miR-214 expression causes downregulation of its target E2F2. Finally, miR-214 overexpression inhibits glioma cell growth in vitro and in vivo by inducing cell cycle arrest in G0/G1. Collectively, these data uncover a novel role for a PPARα-miR-214-E2F2 pathway in controlling glioma cell proliferation.

Prospective QSAR-Based Prediction Models with Pharmacophore Studies of Oxadiazole-Substituted α-Isopropoxy Phenylpropanoic Acids with Dual Activators of PPARα and PPARγ

A series of oxadiazole-substituted [Formula: see text]-isopropoxy phenylpropanoic acids with dual activators of PPARα and PPARγ derivatives were subjected to two-dimensional and k-Nearest Neighbors molecular field analysis. The statistically significant best 2D-QSAR (PPARα ) model having good predictive ability with statistical values of r(2) = 0:8725; q(2) = 0:7957and pred_r(2) = 0:8136 was developed by GA-PLS with the descriptors like SsClcount, SddsN (nitro) count and SsOHcount that contribute significantly to the biological activity. The best 3D-QSAR studies (PPARα ) were performed using the genetic algorithm selection k-nearest neighbor molecular field analysis approach; a leave-one-out cross-validated correlation coefficient q(2) = 0:7188 and predicate activity pred_r(2) = 0.7508 were obtained. The influences of steric and electrostatic field effects generated by the contribution plots are discussed. The best pharmacophore model includes three features, viz. hydrogen bond donor, hydrogen bond acceptor and aromatic features. The information rendered by 2D-QSAR and 3D-QSAR models may lead to a better understanding of structural requirements of substituted α-isopropoxy phenylpropanoic derivatives and also aid in designing novel potent PPARα and PPARγ for antihyperglycemic molecules.

Benzotriazole: An overview on its versatile biological behavior

Discovered in late 1960, azoles are heterocyclic compounds class which constitute the largest group of available antifungal drugs. Particularly, the imidazole ring is the chemical component that confers activity to azoles. Triazoles are obtained by a slight modification of this ring and similar or improved activities as well as less adverse effects are reported for triazole derivatives. Consequently, it is not surprising that benzimidazole/benzotriazole derivatives have been found to be biologically active. Since benzimidazole has been widely investigated, this review is focused on defining the place of benzotriazole derivatives in biomedical research, highlighting their versatile biological properties, the mode of action and Structure Activity Relationship (SAR) studies for a variety of antimicrobial, antiparasitic, and even antitumor, choleretic, cholesterol-lowering agents.

Prospective QSAR-based prediction models with pharmacophore studies of oxadiazole-substituted α-isopropoxy phenylpropanoic acids on with dual activators of PPARα and PPARγ

A series of oxadiazole-substituted α-isopropoxy phenylpropanoic acids with dual activators of PPARα and PPARγ derivatives were subjected to two dimensional and k-nearest neighbour Molecular field analysis. The statistically significant best 2D-QSAR (PPARα) model having good predictive ability with statistical values of r2 = 0.8725, q2 = 0.7957 and pred_r2 = 0.8136, was developed by GA-PLS with the descriptors like SsClcount, SddsN (nitro) count and SsOHcount contribute significantly to the biological activity. The best 3D-QSAR studies (PPARα) were performed using the genetic algorithm selection k-nearest neighbor molecular field analysis approach; a leave-one-out cross-validated correlation coefficient q2=0.7188 and predicate activity pred_r2 =0.7508 were obtained. The influences of steric and electrostatic field effects generated by the contribution plots are discussed. The best pharmacophore model includes three features viz. hydrogen bond donor, hydrogen bond acceptor, and aromatic features were developed. The information rendered by 2D, 3D QSAR models may lead to a better understanding of structural requirements of substituted α-isopropoxy phenylpropanoic derivatives and also aid in designing novel potent PPARα and PPARγ for antihyperglycemic molecules.

Discovery of biaryl-4-carbonitriles as antihyperglycemic agents that may act through AMPK-p38 MAPK pathway

A series of functionalized biaryl-4-carbonitriles was synthesized in three steps and evaluated for PTP-1B inhibitory activity. Among the synthesized compounds, four biaryls 6a-d showed inhibition (IC50 58-75 μM) against in vitro PTP-1B assay possibly due to interaction with amino acid residues Lys120, Tyr46 through hydrogen bonding and aromatic-aromatic interactions, respectively. Two biaryl-4-carbonitriles 6b and 6c showed improved glucose tolerance, fasting as well as postprandial blood glucose, serum total triglycerides, and increased high-density lipoprotein-cholesterol in SLM, STZ, STZ-S and C57BL/KsJ-db/db animal models. The bioanalysis of 4'-bromo-2,3-dimethyl-5-(piperidin-1-yl)biphenyl-4-carbonitrile (6b) revealed that like insulin, it increased 2-deoxyglucose uptake in skeletal muscle cells (L6 and C2C12 myotubes). The compound 6b significantly up-regulated the genes related to the insulin signaling pathways like AMPK, MAPK including glucose transporter-4 (GLUT-4) gene in muscle tissue of C57BL/KsJ-db/db mice. Furthermore, it was observed that the compound 6b up-regulated PPARα, UCP2 and HNF4α, which are key regulator of glucose, lipid, and fatty acid metabolism. Western blot analysis of the compound 6b showed that it significantly increased the phosphorylation of AMPK and p38 MAPK and ameliorated glucose uptake in C57BL/KsJ-db/db mice through the AMPK-p38 MAPK pathway.

Peroxisome proliferator-activated receptor delta and cardiovascular disease

Recent reports have shown that peroxisome proliferator-activated receptor delta (PPARD) plays an important role in different vascular processes suggesting that PPARD is a significant modulator of cardiovascular disease. This review will focus on PPARD in relation to cardiovascular risk factors based on cell, animal and human data. Mouse studies suggest that Ppard is an important metabolic modulator that may have implications for cardiovascular disease (CVD). Specific human PPARD gene variants show no clear association with CVD but interactions between variants and lifestyle factors might influence disease risk. During recent years, development of specific and potent PPARD agonists has also made it possible to study the effects of PPARD activation in humans. PPARD agonists seem to exert beneficial effects on dyslipidemia and insulin-resistant syndromes but safety issues have been raised due to the role that PPARD plays in cell proliferation. Thus, large long term outcome as well as detailed safety and tolerability studies are needed to evaluate whether PPARD agonists could be used to treat CVD in humans.

Generation and characterization of a humanized PPARδ mouse model

BACKGROUND AND PURPOSE

Humanized mice for the nuclear receptor peroxisome proliferator-activated receptor δ (PPARδ), termed PPARδ knock-in (PPARδ KI) mice, were generated for the investigation of functional differences between mouse and human PPARδ and as tools for early drug efficacy assessment.

EXPERIMENTAL APPROACH

Human PPARδ function in lipid metabolism was assessed at baseline, after fasting or when challenged with the GW0742 compound in mice fed a chow diet or high-fat diet (HFD).

KEY RESULTS

Analysis of PPARδ mRNA levels revealed a hypomorph expression of human PPARδ in liver, macrophages, small intestine and heart, but not in soleus and quadriceps muscles, white adipose tissue and skin. PPARδ KI mice displayed a small decrease of high-density lipoprotein-cholesterol whereas other lipid parameters were unaltered. Plasma metabolic parameters were similar in wild-type and PPARδ KI mice when fed chow or HFD, and following physiological (fasting) and pharmacological (GW0742 compound) activation of PPARδ. Gene expression profiling in liver, soleus muscle and macrophages showed similar gene patterns regulated by mouse and human PPARδ. The anti-inflammatory potential of human PPARδ was also similar to mouse PPARδ in liver and isolated macrophages.

CONCLUSIONS AND IMPLICATIONS

These data indicate that human PPARδ can compensate for mouse PPARδ in the regulation of lipid metabolism and inflammation. Overall, this novel PPARδ KI mouse model shows full responsiveness to pharmacological challenge and represents a useful tool for the preclinical assessment of PPARδ activators with species-specific activity.

Effect of overexpression of PPARgamma on the healing process of corneal alkali burn in mice

Wound healing involves both local cells and inflammatory cells. Alkali burn of ocular surface tissue is a serious clinical problem often leading to permanent visual impairment resulting from ulceration, scarring and neovascularization during healing. Behaviors of corneal cells and inflammatory cells are orchestrated by growth factor signaling networks that have not been fully uncovered. Here we showed that adenoviral gene introduction of peroxisome proliferator-activated receptor-gamma (PPARgamma) inhibits activation of ocular fibroblasts and macrophages in vitro and also induced anti-inflammatory and anti-fibrogenic responses in an alkali-burned mouse cornea. PPARgamma overexpression suppressed upregulation of inflammation/scarring-related growth factors and matrix metalloproteinases (MMPs) in macrophages. It also suppressed expression of such growth factors and collagen Ialpha2 and myofibroblast generation upon exposure to TGFbeta1. Exogenous PPARgamma did not alter phosphorylation of Smad2, but inhibited its nuclear translocation. PPARgamma overexpression enhanced proliferation of corneal epithelial cells, but not of fibroblasts in vitro. Epithelial cell expression of MMP-2/-9 and TGFbeta1 and its migration were suppressed by PPARgamma overexpression. In vivo experiments showed that PPARgamma gene introduction suppressed monocytes/macrophages invasion and suppressed the generation of myofibroblasts, as well as upregulation of cytokines/growth factors and MMPs in a healing cornea. In vivo re-epitheliazation with basement membrane reconstruction in the healing, burned, cornea was accelerated by PPARgamma-Ad expression, although PPARgamma overexpression was considered to be unfavorable for cell migration. Together, these data suggest that overexpression of PPARgamma may represent an effective new strategy for treatment of ocular surface burns.

Synthesis and in vivo antihyperglycemic activity of nature-mimicking furanyl-2-pyranones in STZ-S model

Various nature-mimicking pyranones such as 6-(2,5-dimethylfuran-3-yl)-pyran-2-one and 6-(furan-2-yl)-pyran-2-one derivatives were synthesized and evaluated for their in vivo antihyperglycemic activity in sucrose-loaded streptozotocin-induced diabetic rat model. Five of the test compounds showed significant lowering of plasma glucose level in STZ-S model.

Synthesis of benzofuran scaffold-based potential PTP-1B inhibitors

Protein tyrosine phosphatase 1B (PTP-1B) is an enzyme that plays a critical role in down-regulating insulin signaling through dephosphorylation of the insulin receptor. Studies have shown that PTP-1B knockout mice showed increased insulin sensitivity in muscle and liver as well as resistance to obesity. A series of hydroxy benzofuran methyl ketones and their naturally mimicking dimers and linear and angular furanochalcones and flavones have been evaluated as PTP-1B inhibitors. Screened compounds displayed good inhibitory activity.

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.

[4-(2H-1,2,3-Benzotriazol-2-yl)phenoxy]alkanoic Acids as Agonists of Peroxisome Proliferator-Activated Receptors (PPARs)

A series of [4-(2H-1,2,3-benzotriazol-2-yl)phenoxy]alkanoic acids has been synthesized and tested as agonists of Peroxisome Proliferator-Activated Receptor (PPAR) alpha, gamma, and delta. Three compounds displayed 56 to 96% of maximal activity of the reference drug Wy-14643 on PPARalpha, and two of these, i.e., 1 and 5, exhibited also moderate activity on either PPARgamma or delta with efficacy equal to 50% and 46% of that of rosiglitazone and GW 501516, respectively. Thus, compounds 1 and 5 represent interesting starting point for preparing novel agents for the treatment of dyslipidemia or of dyslipidemic type-2 diabetes.

6-Aryl-4-methylsulfanyl-2H-pyran-2-one-3-carbonitriles as PPAR-γ activators

Various 6-aryl-3-cyano/methoxycarbonyl-4-methylsulfanyl-2H-pyran-2-ones have been synthesized as a potential substitute of 2,4-thiazolidinedione head group to express potent PPAR-gamma transactivation response. Some of the screened compounds have shown promising PPAR-gamma agonistic activity.

Antihyperglycemic activity of 2-methyl-3,4,5-triaryl-1H-pyrroles in SLM and STZ models

Various 3,4,5-triarylpyrroles were synthesized and evaluated for their in vivo antihyperglycemic activity in sucrose-loaded (SLM) and/or streptozotocin-induced (STZ) diabetic rat models. Three of the test compounds, 2-methyl-4,5-diphenyl-3-substituted-phenyl-1H-pyrroles (3c, d and h) showed significant inhibition on postprandial hyperglycemia in normal rats post sucrose loaded. These compounds also showed lowering of plasma glucose level in STZ-induced diabetic rat model.