Antiinflammatory and antiarteriosclerotic effects of pioglitazone

Pioglitazone attenuate level of myeloperoxidases and nitic oxide in psoriatic lesion: a proof-of-concept study in a imiquimod induced psoriasis model in rat

OBJECTIVES

Psoriasis is a persistent autoimmune inflammatory condition that is primarily affecting the skin. Pioglitazone (PGZ), a peroxisome proliferator activated receptor gamma (PPARγ) agonist, has been reported to have anti-inflammatory effects. However, the role of PGZ in psoriatic disease remains unclear. In this study, we aimed to repurpose the use of the PGZ for the treatment of psoriasis.

METHODS

To investigate its efficacy, we employed an imiquimod (IMQ)-induced rat model. Wistar rats are randomly allocated to four different groups. Group, I served as a negative control, Group II IMQ control, Group III was treated with pioglitazone hydrogel and Group IV received standard drug betamethasone cream. PASI score was monitored on every alternative day and on day 7 animals were sacrificed and histopathology of skin was performed. Level of nitric oxide (NO) and myeloperoxidase (MPO) was also performed using established methods.

RESULTS

The results of the experiment revealed that treatment with PGZ significantly (p<0.05) reduced redness, scaling, and skin thickening, surpassing the effectiveness of standard drugs. Our result also indicates that PGZ significantly (p<0.05) inhibits the release of both MPO and NO from the psoriatic lesions.

CONCLUSIONS

PGZ effectively reduces the severity of psoriasis possibly by inhibiting the accumulation of neutrophil at the psoriatic area which indirectly regulates the release of NO in the affected area. Our study showed we can repurpose the PGZ for the management of psoriasis.

Electrochemical Assays for the Determination of Antidiabetic Drugs-A Review

This article presents the current state of knowledge regarding electrochemical methods for determining the active substances within drugs that are used in the treatment of type 1 and type 2 diabetes. Electrochemical methods of analysis, due to their sensitivity and easiness, are a great alternative to other, usually more expensive analytical assays. The determination of active substances mentioned in this review is based on oxidation or reduction processes on the surface of the working electrode. A wide variety of working electrodes, often modified with materials such as nanoparticles or conducting polymers, have been used for the highly sensitive analysis of antidiabetic drugs. The presented assays allow us to determine the compounds of interest in various samples, such as pharmaceutical products or different human bodily fluids.

Pioglitazone Protects Tubular Epithelial Cells during Kidney Fibrosis by Attenuating miRNA Dysregulation and Autophagy Dysfunction Induced by TGF-β

Excessive renal TGF-β production and pro-fibrotic miRNAs are important drivers of kidney fibrosis that lack any efficient treatment. Dysfunctional autophagy might play an important role in the pathogenesis. We aimed to study the yet unknown effects of peroxisome proliferator-activated receptor-γ (PPARγ) agonist pioglitazone (Pio) on renal autophagy and miRNA dysregulation during fibrosis. Mouse primary tubular epithelial cells (PTEC) were isolated, pre-treated with 5 µM pioglitazone, and then stimulated with 10 ng/mL TGF-β1 for 24 h. Male 10-week-old C57Bl6 control (CTL) and TGF-β overexpressing mice were fed with regular chow (TGF) or Pio-containing chow (20 mg/kg/day) for 5 weeks (TGF + Pio). PTEC and kidneys were evaluated for mRNA and protein expression. In PTEC, pioglitazone attenuated (p < 0.05) the TGF-β-induced up-regulation of Col1a1 (1.4-fold), Tgfb1 (2.2-fold), Ctgf (1.5-fold), Egr2 (2.5-fold) mRNAs, miR-130a (1.6-fold), and miR-199a (1.5-fold), inhibited epithelial-to-mesenchymal transition, and rescued autophagy function. In TGF mice, pioglitazone greatly improved kidney fibrosis and related dysfunctional autophagy (increased LC3-II/I ratio and reduced SQSTM1 protein content (p < 0.05)). These were accompanied by 5-fold, 3-fold, 12-fold, and 2-fold suppression (p < 0.05) of renal Ccl2, Il6, C3, and Lgals3 mRNA expression, respectively. Our results implicate that pioglitazone counteracts multiple pro-fibrotic processes in the kidney, including autophagy dysfunction and miRNA dysregulation.

Storage Stability of Atheroglitatide, an Echogenic Liposomal Formulation of Pioglitazone Targeted to Advanced Atheroma with a Fibrin-Binding Peptide

We have conducted a stability study of a complex liposomal pharmaceutical product, Atheroglitatide (AGT), stored at three temperatures, 4, 24, and 37 °C, for up to six months. The six parameters measured were functions of liposomal integrity (size and number), drug payload (loading efficiency), targeting peptide integrity (conjugation efficiency and specific avidity), and echogenicity (ultrasound-dependent controlled drug release), which were considered most relevant to the product's intended use. At 4 °C, liposome diameter trended upward, indicative of aggregation, while liposome number per mg lipid and echogenicity trended downward. At 24 °C, peptide conjugation efficiency (CE) and targeting efficiency (TE, specific avidity) trended downward. At 37 °C, CE and drug (pioglitazone) loading efficiency trended downward. At 4 °C, the intended storage temperature, echogenicity, and liposome size reached their practical tolerance limits at 6 months, fixing the product expiration at that point. Arrhenius analysis of targeting peptide CE and drug loading efficiency decay at the higher temperatures indicated complete stability of these characteristics at 4 °C. The results of this study underscore the storage stability challenges presented by complex nanopharmaceutical formulations.

Encapsulation of Pioglitazone into Polymer-Nanoparticles for Potential Treatment of Atherosclerotic Diseases

Atherosclerosis is one of the most urgent global health subjects, causes millions of deaths worldwide, and is associated with enormous healthcare costs. Macrophages are the root cause for inflammatory onset and progression of the disease but are not addressed by conventional therapy. Therefore, we used pioglitazone, which is a drug initially used for diabetes therapies, but at the same time has great potential regarding the mitigation of inflammation. As yet, this potential of pioglitazone cannot be exploited, as drug concentrations at the target site in vivo are not sufficient. To overcome this shortcoming, we established PEG-PLA/PLGA-based nanoparticles loaded with pioglitazone and tested them in vitro. Encapsulation of the drug was analyzed by HPLC and revealed an outstanding encapsulation efficiency of 59% into the nanoparticles, which were 85 nm in size and had a PDI of 0.17. Further, uptake of our loaded nanoparticles in THP-1 macrophages was comparable to the uptake of unloaded nanoparticles. On the mRNA level, pioglitazone-loaded nanoparticles were superior to the free drug by 32% in increasing the expression of the targeted receptor PPAR-γ. Thereby the inflammatory response in macrophages was ameliorated. In this study, we take the first step toward an anti-inflammatory, causal antiatherosclerotic therapy, using the potential of the already established drug pioglitazone, and enable it to enrich at the target site by using nanoparticles. An additional crucial feature of our nanoparticle platform is the versatile modifiability of ligands and ligand density, to achieve an optimal active targeting effect in the future.

Demonstration of ultrasound-mediated therapeutic delivery of fibrin-targeted pioglitazone-loaded echogenic liposomes into the arterial bed for attenuation of peri-stent restenosis

Peri-stent restenosis following stent implantation is a major clinical problem. We have previously demonstrated that ultrasound-facilitated liposomal delivery of pioglitazone (PGN) to the arterial wall attenuated in-stent restenosis. To evaluate ultrasound mediated arterial delivery, in Yucatan miniswine, balloon inflations were performed in the carotid and subclavian arteries to simulate stent implantation and induce fibrin formation. The fibrin-binding peptide, GPRPPGGGC, was conjugated to echogenic liposomes (ELIP) containing dinitrophenyl-L-alanine-labelled pioglitazone (DNP-PGN) for targeting purposes. After pre-treating the arteries with nitroglycerine, fibrin-binding peptide-conjugated PGN-loaded ELIP (PAFb-DNP-PGN-ELIP also termed atheroglitatide) were delivered to the injured arteries via an endovascular catheter with an ultrasound core, either with or without ultrasound application (EKOSTM Endovascular System, Boston Scientific). In arteries treated with atheroglitatide, there was substantial delivery of PGN into the superficial layers (5 µm from the lumen) of the arteries with and without ultrasound, [(1951.17 relative fluorescence units (RFU) vs. 1901.17 RFU; P-value = 0.939)]. With ultrasound activation there was increased penetration of PGN into the deeper arterial layers (up to 35 µm from the lumen) [(13195.25 RFU vs. 7681.00 RFU; P-value = 0.005)]. These pre-clinical data demonstrate ultrasound mediated therapeutic vascular delivery to deeper layers of the injured arterial wall. This model has the potential to reduce peri- stent restenosis.

Assessment of Efficacy and Safety Using PPAR-γ Agonist-Loaded Nanocarriers for Inflammatory Eye Diseases

Drug-loaded nanocarriers (NCs) are new systems that can greatly improve the delivery and targeting of drugs to specific tissues and organs. In our work, a PPAR-γ agonist loaded into polymeric NCs was prepared, stabilized by spray-drying, and tested in vitro, ex vivo, and in vivo (animal models) to provide a safe formulation for optical anti-inflammatory treatments. The NCs were shown to be well tolerated, and no signs of irritancy or alterations of the eye properties were detected by the in vitro HET-CAM test and in vivo Draize test. Furthermore, no signs of cytotoxicity were found in the NC formulations on retinoblastoma cells (Y-79) analyzed using the alamarBlue assay, and the transmittance experiments evidenced good corneal transparency with the formulations tested. The ocular anti-inflammatory study confirmed the significant prevention efficacy using the NCs, and these systems did not affect the corneal tissue structure. Moreover, the animal corneal structure treated with the NCs was analyzed using X-ray diffraction using synchrotron light. Small-angle X-ray scattering (SAXS) analysis did not show a significant difference in corneal collagen interfibrillar spacing after the treatment with freshly prepared NCs or NCs after the drying process compared to the corresponding negative control when inflammation was induced. Considering these results, the PPAR-γ agonist NCs could be a safe and effective alternative for the treatment of inflammatory ocular processes.

Prophylactic and Ameliorative Effects of PPAR-γ Agonist Pioglitazone in Improving Oxidative Stress, Germ Cell Apoptosis and Inflammation in Gentamycin-Induced Testicular Damage in Adult Male Albino Rats

Peroxisome proliferator-activated receptor gamma (PPAR-γ) is ubiquitously expressed in testicular tissue and plays a crucial role in regulating various physiological processes. Pioglitazone (PIO) is one of the PPAR-γ agonists, having anti-oxidant and anti-inflammatory effects. Patients on gentamycin treatment may undergo serious side effects such as testicular damage. To the best of our knowledge, this was the first study to investigate the possible protective anti-inflammatory and anti-apoptotic effects of PIO on gentamycin-induced testicular damage. Fifty adult male Wistar albino rats included in the study as the control group (CTL) received normal saline; a gentamycin-induced testicular damage group (GM) received gentamycin (100 mg/kg); PIO5, PIO10, PIO20 groups received PIO at a dose of 5, 10, and 20 mg/ kg, respectively, for 21 days, and gentamycin was started at day 15 of the experiment for 6 days. The parameters of spermatozoa and histopathological alterations in the testes were significantly improved in the PIO20 group. Moreover, MDA levels, inflammatory mediators, and apoptotic Bax expression were decreased. The activity of glutathione peroxidase, catalase, total antioxidant capacity, and anti-apoptotic Bcl-2 genes expression were increased. It was concluded that PIO20 could protect against gentamycin-induced testicular damage in Wistar rats through its anti-oxidant, anti-inflammatory, and antiapoptotic effects.

Atherosclerosis: Conventional intake of cardiovascular drugs versus delivery using nanotechnology - A new chance for causative therapy?

Atherosclerosis is the leading cause of death in developed countries. The pathogenetic mechanism relies on a macrophage-based immune reaction to low density lipoprotein (LDL) deposition in blood vessels with dysfunctional endothelia. Thus, atherosclerosis is defined as a chronic inflammatory disease. A plethora of cardiovascular drugs have been developed and are on the market, but the major shortcoming of standard medications is that they do not address the root cause of the disease. Statins and thiazolidinediones that have recently been recognized to exert specific anti-atherosclerotic effects represent a potential breakthrough on the horizon. But their whole potential cannot be realized due to insufficient availability at the pathological site and severe off-target effects. The focus of this review will be to elaborate how both groups of drugs could immensely profit from nanoparticulate carriers. This delivery principle would allow for their accumulation in target macrophages and endothelial cells of the atherosclerotic plaque, increasing bioavailability where it is needed most. Based on the analyzed literature we conclude design criteria for the delivery of statins and thiazolidinediones with nanoparticles for anti-atherosclerotic therapy. Nanoparticles need to be below a diameter of 100 nm to accumulate in the atherosclerotic plaque and should be fabricated using biodegradable materials. Further, the thiazolidinediones or statins must be encapsulated into the particle core, because especially for thiazolidindiones the uptake into cells is prerequisite for their mechanism of action. For optimal uptake into targeted macrophages and endothelial cells, the ideal particle should present ligands on its surface which bind specifically to scavenger receptors. The impact of statins on the lectin-type oxidized LDL receptor 1 (LOX1) seems particularly promising because of its outstanding role in the inflammatory process. Using this pioneering concept, it will be possible to promote the impact of statins and thiazolidinediones on macrophages and endothelial cells and significantly enhance their anti-atherosclerotic therapeutic potential.

Pioglitazone Exposure Reduced the Risk of All-Cause Mortality in Insulin-Treated Patients with Type 2 Diabetes Mellitus

CONTEXT

The long-term safety and benefit of pioglitazone use in combination with insulin are still uncertain.

OBJECTIVE

This study compared the risks of all-cause mortality and major cardiovascular (CV) events between pioglitazone users and nonusers receiving insulin therapy.

DESIGN, SETTING AND PATIENTS

We conducted a 13-year retrospective cohort study by using data from the population-based National Health Insurance Research Database in Taiwan. A total of 20 376 patients with type 2 diabetes mellitus (T2DM) receiving insulin therapy were enrolled during 2000 to 2012. Overall, the incidence rates of all-cause mortality and CV events were compared between 2579 pioglitazone users and 2579 matched nonusers.

RESULTS

After adjustment for age, sex, comorbidities, Diabetes Complications Severity Index scores, and drugs used, mortality rates were 30.26 and 15.02 per 1000 person-years for pioglitazone nonusers and users, respectively. The adjusted hazard ratio (aHR) of mortality was 0.47 (95% confidence interval [CI]: 0.38-0.58, P < 0.001) for pioglitazone users compared with nonusers. The aHRs of CV and non-CV deaths were 0.78 (95% CI: 0.51-1.19) and 0.50 (95% CI: 0.38-0.66), respectively. The aHRs of hospitalized coronary artery disease, hospitalized stroke, and incident heart failure were not significantly different between pioglitazone users and nonusers.

CONCLUSIONS

This nationwide cohort study demonstrated that pioglitazone use reduced the risks of all-cause mortality and non-CV death for patients with T2DM undergoing insulin therapy.

Pioglitazone Modulates the Vascular Contractility in Hypertension by Interference with ET-1 Pathway

Endothelin-1 (ET-1) is an important modulator of the vascular tone and a proinflammatory molecule that contributes to the vascular damage observed in hypertension. Peroxisome-proliferator activated receptors-γ (PPARγ) agonists show cardioprotective properties by decreasing inflammatory molecules such as COX-2 and reactive oxygen species (ROS), among others. We investigated the possible modulatory effect of PPARγ activation on the vascular effects of ET-1 in hypertension. In spontaneously hypertensive rats (SHR), but not in normotensive rats, ET-1 enhanced phenylephrine-induced contraction through ET_A by a mechanism dependent on activation of TP receptors by COX-2-derived prostacyclin and reduction in NO bioavailability due to enhanced ROS production. In SHR, the PPARγ agonist pioglitazone (2.5 mg/Kg·day, 28 days) reduced the increased ET_A levels and increased those of ET_B. After pioglitazone treatment of SHR, ET-1 through ET_B decreased ROS levels that resulted in increased NO bioavailability and diminished phenylephrine contraction. In vascular smooth muscle cells from SHR, ET-1 increased ROS production through AP-1 and NFκB activation, leading to enhanced COX-2 expression. These effects were blocked by pioglitazone. In summary, in hypertension, pioglitazone shifts the vascular ET_A/ET_B ratio, reduces ROS/COX-2 activation and increases NO availability; these changes explain the effect of ET-1 decreasing phenylephrine-induced contraction.

Nanostructured Lipid Carriers of Pioglitazone Loaded Collagen/Chitosan Composite Scaffold for Diabetic Wound Healing

Diabetic wound is a major problem that often needs amputation of the concerned organ in patients suffering from diabetes. In diabetes, the prolonged phase of inflammation obstructs the further phases of healing which, in turn, lead to improper healing of the wounds in diabetes. Pioglitazone (Pio) hydrochloride is an antidiabetic drug with reported anti-inflammatory properties. The aim of this study was to develop a Pio-nanostructured lipid carrier (Pio-NLC)-loaded collagen/chitosan (COL-CS) scaffold and evaluate its healing ability in diabetic wounds. The results of characterization of composite scaffolds reveal that cross-linked scaffolds possess optimum porosity, low matrix degradation, and sustained drug release compared with noncross-linked scaffolds. The in vitro studies reveal that the Pio-NLC-COL-CS scaffold was biocompatible and enhanced cell growth compared with control and NLC-COL-CS. Using the streptozotocin-induced diabetic wound model, significantly (p < 0.001) higher rates of wound contraction in Pio-NLC-COL-CS scaffold-treated group were observed in comparison with that in control and NLC-COL-CS-treated group. The enzyme-linked immunosorbent assay results indicate a significant (p < 0.001) decrease of matrix metalloproteinases-9 levels in the Pio-NLC-COL-CS-treated group compared with those in control group. Use of nanostructured lipid carrier (Pio-NLC-COL-CS) scaffold can prove to be a promising strategy for local treatment for diabetic wounds.

Efficacy of anti-inflammatory treatment on major depressive disorder or depressive symptoms: meta-analysis of clinical trials

BACKGROUND

No study has gathered evidence from all randomized clinical trials (RCTs) with anti-inflammatory drugs measuring antidepressant effects including a detailed assessment of side-effects and bias.

METHODS

We performed a systematic review identifying RCTs published prior to January 1, 2018, studying antidepressant treatment effects and side-effects of pharmacological anti-inflammatory intervention in adults with major depressive disorder (MDD) or depressive symptoms. Outcomes were depression scores after treatment, remission, response, and side-effects. Pooled standard mean differences (SMD) and risk ratios (RR) including 95% confidence intervals (95%-CI) were calculated.

RESULTS

We identified 36 RCTs, whereof 13 investigated NSAIDs (N = 4214), 9 cytokine inhibitors (N = 3345), seven statins (N = 1576), 3 minocycline (N = 151), 2 pioglitazone (N = 77), and 2 glucocorticoids (N = 59). Anti-inflammatory agents improved depressive symptoms compared to placebo as add-on in patients with MDD (SMD = -0.64; 95%-CI = -0.88, -0.40; I²  = 51%; N = 597) and as monotherapy (SMD = -0.41; 95%-CI = -0.60, -0.22; I²  = 93%, N = 8825). Anti-inflammatory add-on improved response (RR = 1.76; 95%-CI = 1.44-2.16; I²  = 16%; N = 341) and remission (RR = 2.14; 95%-CI = 1.03-4.48; I²  = 57%; N = 270). We found a trend toward an increased risk for infections, and all studies showed high risk of bias.

CONCLUSION

Anti-inflammatory agents improved antidepressant treatment effects. Future RCTs need to include longer follow-up, identify optimal doses and subgroups of patients that can benefit from anti-inflammatory intervention.

Therapeutic Strategies for Treatment of Inflammation-related Depression

BACKGROUND

Mounting evidence demonstrates enhanced systemic levels of inflammatory mediators in depression, indicating that inflammation may play a role in the etiology and course of mood disorders. Indeed, proinflammatory cytokines induce a behavioral state of conservation- withdrawal resembling human depression, characterized by negative mood, fatigue, anhedonia, psychomotor retardation, loss of appetite, and cognitive deficits. Neuroinflammation also contributes to non-responsiveness to current antidepressant (AD) therapies. Namely, response to conventional AD medications is associated with a decrease in inflammatory biomarkers, whereas resistance to treatment is accompanied by increased inflammation.

METHODS

In this review, we will discuss the utility and shortcomings of pharmacologic AD treatment strategies focused on inflammatory pathways, applied alone or as an adjuvant component to current AD therapies.

RESULTS

Mechanisms of cytokine actions on behavior involve activation of inflammatory pathways in the brain, resulting in changes of neurotransmitter metabolism, neuroendocrine function, and neuronal plasticity. Selective serotonin reuptake inhibitors exhibit the most beneficial effects in restraining the inflammation markers in depression. Different anti-inflammatory agents exhibit AD effects via modulating neurotransmitter systems, neuroplasticity markers and glucocorticoid receptor signaling. Anti-inflammatory add-on therapy in depression highlights such treatment as a candidate for enhancement strategy in patients with moderate-to-severe depression.

CONCLUSION

The interactions between the immune system and CNS are not only involved in shaping behavior, but also in responding to therapeutics. Even though, substantial evidence from animal and human research support a beneficial effect of anti-inflammatory add-on therapy in depression, further research with special attention on safety, particularly during prolonged periods of antiinflammatory co-treatments, is required.

Different Effects of Thiazolidinediones on In-Stent Restenosis and Target Lesion Revascularization after PCI: A Meta-Analysis of Randomized Controlled Trials

In-stent restenosis (ISR) remains the leading problem encountered after percutaneous coronary intervention (PCI). Thiazolidinediones (TZDs) has been shown to be associated with reduced ISR and target lesion revascularization (TLR); however, the results are inconsistent, especially between rosiglitazone and pioglitazone. In this study, fourteen RCTs with a total of 1350 patients were finally included through a systematical literature search of Embase, Pubmed, the Cochrane Library, and ClinicalTrials.gov from inception to January 31, 2017. The follow-up duration of the included trials ranged from 6 months to 18 months. The results demonstrated that TZDs treatment is associated with significantly reduced risk of TLR (RR:0.45, 95%CI 0.30 to 0.67 for pioglitazone, RR:0.68, 95%CI 0.46 to 1.00 for rosiglitazone). Pioglitazone is associated with significantly reduced risks of ISR (RR:0.47, 95%CI 0.27 to 0.81), major adverse cardiac events (MACE) (RR:0.44, 95%CI 0.30 to 0.64) and neointimal area (SMD: −0.585, 95%CI −0.910 to −0.261). No significant relationship was observed between rosiglitazone and ISR (RR:0.91, 95%CI 0.39 to 2.12), MACE (RR:0.73, 95%CI 0.53 to 1.00) and neointimal area (SMD: −0.164, 95%CI −1.146 to 0.818). This meta-analysis demonstrated that TZDs treatment is associated with significant reduction in ISR, TLR and MACE for patients after PCI. Pioglitazone treatment seems to have more beneficial effects than rosiglitazone and no significantly increased cardiovascular risk was detected for both agents.

Pioglitazone Ameliorates Smooth Muscle Cell Proliferation in Cuff-Induced Neointimal Formation by Both Adiponectin-Dependent and -Independent Pathways

The aim of this study is to elucidate to what degree adiponectin is involved in TZD-mediated amelioration of neointimal formation. We investigated the effect of 3- or 8-weeks' pioglitazone on cuff-induced neointimal formation in adiponectin-deficient (APN-KO) and wild-type (WT) mice. Pioglitazone for 3 weeks reduced neointimal formation in the WT mice with upregulation of the plasma adiponectin levels, but failed to reduce neointimal formation in the APN-KO mice, suggesting that pioglitazone suppressed neointimal formation by adiponectin-dependent mechanisms. Pioglitazone for 3 weeks suppressed vascular smooth muscle cell (VSMC) proliferation and increased AdipoR2 expression in the WT mice. In vitro, globular adiponectin activated AMPK through both AdipoR1 and AdipoR2, resulting in the inhibition of VSMC proliferation. Interestingly, 8-weeks' pioglitazone was reduced neointimal formation in APN-KO mice to degree similar to that seen in the WT mice, suggesting that pioglitazone can also suppress neointimal formation via a mechanism independent of adiponectin. Pioglitazone for 8 weeks completely abrogated the increased VSMC proliferation, along with a reduction of cyclin B1 and cyclin D1 expressions and cardiovascular risk profile in the APN-KO mice. In vitro, pioglitazone suppressed these expressions, leading to inhibition of VSMC proliferation. Pioglitazone suppresses neointimal formation via both adiponectin-dependent and adiponectin-independent mechanisms.

Pioglitazone, a PPARγ agonist, attenuates PDGF-induced vascular smooth muscle cell proliferation through AMPK-dependent and AMPK-independent inhibition of mTOR/p70S6K and ERK signaling

Pioglitazone (PIO), a PPARγ agonist that improves glycemic control in type 2 diabetes through its insulin-sensitizing action, has been shown to exhibit beneficial effects in the vessel wall. For instance, it inhibits vascular smooth muscle cell (VSMC) proliferation, a major event in atherosclerosis and restenosis after angioplasty. Although PPARγ-dependent and PPARγ-independent mechanisms have been attributed to its vasoprotective effects, the signaling events associated with PIO action in VSMCs are not fully understood. To date, the likely intermediary role of AMP-activated protein kinase (AMPK) toward PIO inhibition of VSMC proliferation has not been examined. Using human aortic VSMCs, the present study demonstrates that PIO activates AMPK in a sustained manner thereby contributing in part to inhibition of key proliferative signaling events. In particular, PIO at 30μM concentration activates AMPK to induce raptor phosphorylation, which diminishes PDGF-induced mTOR activity as evidenced by decreased phosphorylation of p70S6K, 4E-BP1, and S6 and increased accumulation of p27(kip1), a cell cycle inhibitor. In addition, PIO inhibits the basal phosphorylation of ERK in VSMCs. Downregulation of endogenous AMPK by target-specific siRNA reveals an AMPK-independent effect for PIO inhibition of ERK, which contributes in part to diminutions in cyclin D1 expression and Rb phosphorylation and the suppression of VSMC proliferation. Furthermore, AMPK-dependent inhibition of mTOR/p70S6K and AMPK-independent inhibition of ERK signaling occur regardless of PPARγ expression/activation in VSMCs as evidenced by gene silencing and pharmacological inhibition of PPARγ. Strategies that utilize nanoparticle-mediated PIO delivery at the lesion site may limit restenosis after angioplasty without inducing PPARγ-mediated systemic adverse effects.

Pioglitazone Suppresses CXCR7 Expression To Inhibit Human Macrophage Chemotaxis through Peroxisome Proliferator-Activated Receptor γ

Cardiovascular disease is the leading cause of morbidity and mortality in patients with type 2 diabetes mellitus (T2DM). Pioglitazone, the widely used thiazolidinedione, is shown to be efficient in the prevention of cardiovascular complications of T2DM. In this study, we report that pioglitazone inhibits CXCR7 expression and thus blocks chemotaxis in differentiated macrophage without perturbing cell viability or macrophage differentiation. In addition, pioglitazone-mediated CXCR7 suppression and chemotaxis inhibition occur via activating peroxisome proliferator-activated receptor γ (PPARγ) but not PPARα in differentiated macrophage. More importantly, pioglitazone therapy-induced PPARγ activation suppresses CXCR7 expression in human carotid atherosclerotic lesions. Collectively, our data demonstrate that pioglitazone suppresses CXCR7 expression to inhibit human macrophage chemotaxis through PPARγ.

Glitazones inhibit human monoamine oxidase but their anti-inflammatory actions are not mediated by VAP-1/semicarbazide-sensitive amine oxidase inhibition

Glitazones are peroxisome proliferator-activated receptor gamma (PPARγ) agonists widely used as antidiabetic drugs also known as thiazolidinediones. Most of them exert other effects such as anti-inflammatory actions via mechanisms supposed to be independent from PPARγ activation (e.g., decreased plasma monocyte chemoattractant protein-1 (MCP-1) levels). Recently, pioglitazone has been shown to inhibit the B form of monoamine oxidase (MAO) in mouse, while rosiglitazone and troglitazone were described as non-covalent inhibitors of both human MAO A and MAO B. Since molecules interacting with MAO might also inhibit semicarbazide-sensitive amine oxidase (SSAO), known as vascular adhesion protein-1 (VAP-1), and since VAP-1/SSAO inhibitors exhibit anti-inflammatory activity, our aim was to elucidate whether VAP-1/SSAO inhibition could be a mechanism involved in the anti-inflammatory behaviour of glitazones. To this aim, MAO and SSAO activities were measured in human subcutaneous adipose tissue biopsies obtained from overweight women undergoing plastic surgery. The production of hydrogen peroxide, an end-product of amine oxidase activity, was determined in tissue homogenates using a fluorometric method. The oxidation of 1 mM tyramine was inhibited by pargyline and almost resistant to semicarbazide, therefore predominantly MAO-dependent. Rosiglitazone was more potent than pioglitazone in inhibiting tyramine oxidation. By contrast, benzylamine oxidation was only abolished by semicarbazide: hence SSAO-mediated. Pioglitazone hampered SSAO activity only when tested at 1 mM while rosiglitazone was inefficient. However, rosiglitazone exhibited anti-inflammatory activity in human adipocytes by limiting MCP-1 expression. Our observations rule out any involvement of VAP-1/SSAO inhibition and subsequent limitation of leukocyte extravasation in the anti-inflammatory action of glitazones.

Pioglitazone enhances the blood pressure-lowering effect of losartan via synergistic attenuation of angiotensin II-induced vasoconstriction

INTRODUCTION

This study was designed to investigate the underlying mechanisms of synergistic antihypertensive effect produced by combination therapy of losartan and pioglitazone in metabolic syndrome (MS) rats.

MATERIALS AND METHODS

An MS model was induced by feeding rats a high-fat, high-sodium diet and 20% sucrose solution. Losartan (20 mg/kg/day), pioglitazone (10 mg/kg/day), and their combination were orally administered for eight consecutive weeks. Systolic blood pressure (SBP) and mean arterial pressure (MAP) were measured using the tail-cuff method and carotid arterial catheterization, respectively. The aortas were isolated and in vitro vascular reactivity studies were performed. The protein expression of angiotensin type 1 receptor (AT1), endothelial nitric oxide synthase (eNOS), phosphorylated eNOS and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit p47(phox), level of nitrotyrosine as well as activity of eNOS and NADPH oxidase in aortas of MS rats were detected.

RESULTS

After eight weeks of treatment, the SBP and MAP in the losartan (115 ± 5 and 106 ± 6 mmHg), pioglitazone (130 ± 6 and 118 ± 6 mmHg), and combination therapy (105 ± 6 and 98 ± 5 mmHg) groups were lower than those in the model group (150 ± 8 and 136 ± 9 mmHg). Combination therapy of losartan and pioglitazone reduced BP more than either monotherapy, and showed additive effects on improving endothelial dysfunction and abolishing the increased vascular responsiveness to angiotensin II. These synergistic effects were associated with further reductions in protein expression of p47(phox) and AT1, NADPH oxidase activity, and nitrotyrosine level.

CONCLUSIONS

Our data indicate that combined treatment exerts more beneficial effects on lowering BP and improving vascular lesions.

Metabolic and other effects of pioglitazone as an add-on therapy to metformin in the treatment of polycystic ovary syndrome (PCOS)

Insulin resistance is a key pathogenic defect of the clustered metabolic disturbances seen in polycystic ovary syndrome (PCOS). Metformin is an insulin sensitizer acting in the liver and the peripheral tissues that ameliorates the metabolic and reproductive defects in PCOS. In addition, pioglitazone is an insulin sensitizer used in diabetes mellitus type 2 (T2DM), improving insulin resistance (IR) in adipose tissue and muscles. In T2DM, these drugs are also used as a combined treatment due to their "add-on effect" on insulin resistance. Although the beneficial role of troglitazone (a member of the thiazolidinediones (TZDs) family) in PCOS has been shown in the past, currently only pioglitazone is available in the market. A few small randomized controlled trials have directly compared the effectiveness of pioglitazone in women with PCOS, while there are a limited number of small studies that support the beneficial metabolic add-on effect of pioglitazone on metformin-treated PCOS women as compared to metformin or pioglitazone monotherapy. These findings suggest a potentially promising role for combined pioglitazone/metformin treatment in the management of PCOS in metformin-resistant patients. In view of recent concerns regarding pioglitazone usage and its associated health risk, we aim to compare the pros and cons of each drug regarding their metabolic and other hormonal effects in women with PCOS and to explore the possible beneficial effect of combined therapy in certain cases, taking into consideration the teratogenic effect of pioglitazone. Finally, we discuss the need for a randomized controlled trial that will evaluate the metabolic and other hormonal effects of combined metformin/pioglitazone treatment in PCOS with selective treatment targets.

Pioglitazone improves in vitro viability and function of endothelial progenitor cells from individuals with impaired glucose tolerance

Background

Evidence suggests that the PPARγ-agonist insulin sensitizer pioglitazone, may provide potential beneficial cardiovascular (CV) effects beyond its anti-hyperglycaemic function. A reduced endothelial progenitor cell (EPC) number is associated with impaired glucose tolerance (IGT) or diabetes, conditions characterised by increased CV risk.

Aim

To evaluate whether pioglitazone can provide benefit in vitro in EPCs obtained from IGT subjects.

Materials and Methods

Early and late-outgrowth EPCs were obtained from peripheral blood mononuclear cells of 14 IGT subjects. The in vitro effect of pioglitazone (10 µM) with/without PPARγ-antagonist GW9662 (1 µM) was assessed on EPC viability, apoptosis, ability to form tubular-like structures and pro-inflammatory molecule expression.

Results

Pioglitazone increased early and late-outgrowth EPC viability, with negligible effects on apoptosis. The capacity of EPCs to form tubular-like structures was improved by pioglitazone in early (mean increase 28%; p = 0.005) and late-outgrowth (mean increase 30%; p = 0.037) EPCs. Pioglitazone reduced ICAM-1 and VCAM-1 adhesion molecule expression in both early (p = 0.001 and p = 0.012 respectively) and late-outgrowth (p = 0.047 and p = 0.048, respectively) EPCs. Similarly, pioglitazone reduced TNFα gene and protein expression in both early (p = 0.034;p = 0.022) and late-outgrowth (p = 0.026;p = 0.017) EPCs compared to control. These effects were prevented by incubation with the PPARγ-antagonist GW9662.

Conclusion

Pioglitazone exerts beneficial effects in vitro on EPCs isolated from IGT subjects, supporting the potential implication of pioglitazone as a CV protective agents.

Pioglitazone treatment increases COX-2-derived prostacyclin production and reduces oxidative stress in hypertensive rats: role in vascular function

BACKGROUND AND PURPOSE

PPARγ agonists, glitazones, have cardioprotective and anti-inflammatory actions associated with gene transcription interference. In this study, we determined whether chronic treatment of adult spontaneously hypertensive rats (SHR) with pioglitazone alters BP and vascular structure and function, and the possible mechanisms involved.

EXPERIMENTAL APPROACH

Mesenteric resistance arteries from untreated or pioglitazone-treated (2.5 mg·kg⁻¹ ·day⁻¹ , 28 days) SHR and normotensive [Wistar Kyoto (WKY)] rats were used. Vascular structure was studied by pressure myography, vascular function by wire myography, protein expression by Western blot and immunohistochemistry, mRNA levels by RT-PCR, prostanoid levels by commercial kits and reactive oxygen species (ROS) production by dihydroethidium-emitted fluorescence.

KEY RESULTS

In SHR, pioglitazone did not modify either BP or vascular structural and mechanical alterations or phenylephrine-induced contraction, but it increased vascular COX-2 levels, prostacyclin (PGI₂) production and the inhibitory effects of NS 398, SQ 29,548 and tranylcypromine on phenylephrine responses. The contractile phase of the iloprost response, which was reduced by SQ 29,548, was greater in pioglitazone-treated and pioglitazone-untreated SHR than WKY. In addition, pioglitazone abolished the increased vascular ROS production, NOX-1 levels and the inhibitory effect of apocynin and allopurinol on phenylephrine contraction, whereas it did not modify eNOS expression but restored the potentiating effect of N-nitro-L-arginine methyl ester on phenylephrine responses.

CONCLUSIONS AND IMPLICATIONS

Although pioglitazone did not reduce BP in SHR, it increased COX-2-derived PGI₂ production, reduced oxidative stress, and increased NO bioavailability, which are all involved in vasoconstrictor responses in resistance arteries. These effects would contribute to the cardioprotective effect of glitazones reported in several pathologies.

Endothelial dysfunction and insulin resistance

In this article, we review several mechanisms by which insulin resistance is related to endothelial dysfunction. The mechanisms we discuss may explain the high prevalence of cardiovascular disease found in people with the metabolic syndrome and diabetes mellitus.

Effect of new thiazolidine derivatives LPSF/GQ-02 and LPSF/GQ-16 on atherosclerotic lesions in LDL receptor-deficient mice (LDLR(-/-))

BACKGROUND

Atherosclerotic cardiovascular disease is a chronic inflammatory condition. Thiazolidinediones (TZDs) are used to enhance sensitivity to insulin and have demonstrated a protective effect over a variety of cardiovascular markers and risk factors. Controversially, the TZDs are associated with the development of heart failure. Thus, lines of research have invested in the search for new molecules in order to obtain more selective and less harmful treatment alternatives for the pathogenesis of atherosclerosis and its risk factors.

METHODS

Animals were fed a diet rich in fat for 10 weeks. In the last 2 weeks, animals received either pioglitazone, LPSF/GQ-02, or LPSF/GQ-16 daily through gavage. At the end of the treatment, blood was collected for biochemical analysis and the aortas were dissected for subsequent analyses.

RESULTS

No changes in the blood lipid profile were found following the use of the drugs in comparison to the control. However, the new thiazolidine derivatives were more efficient in improving insulin resistance in comparison to pioglitazone and the control group. Morphometric analyses revealed that neither pioglitazone nor LPSF/GQ16 led to satisfactory effects over atherosclerosis. However, LPSF/GQ-02 led to a reduction in area of the atherosclerotic lesions. Ultrastructural analyses revealed extensive degeneration of the endothelium and an increase in apoptotic cells in the subendothelial space following the use of pioglitazone and LPSF/GQ-16. However, LPSF/GQ-02 caused minimal cell alterations in the aortic endothelium. Regarding markers, endothelial nitric oxide synthase (eNOS) and matrix metalloproteinase 9 (MMP-9), LPSF/GQ-16, and pioglitazone exerted similar effects, increasing the expression of MMP-9, and had no effect on the expression of eNOS compared with the control group. On the other hand, LPSF/GQ-02 was effective in reducing the expression of MMP-9 and increased eNOS significantly.

CONCLUSIONS

The results suggest that the new thiazolidine derivative LPSF/GQ-02 is a promising candidate for the treatment of atherosclerosis.

Monocyte Chemoattractant Protein 1 (MCP-1) in obesity and diabetes

Monocyte Chemoattractant Protein-1 (MCP-1) is the first discovered and most extensively studied CC chemokine, and the amount of studies on its role in the etiologies of obesity- and diabetes-related diseases have increased exponentially during the past two decades. This review attempted to provide a panoramic perspective of the history, regulatory mechanisms, functions, and therapeutic strategies of this chemokine. The highlights of this review include the roles of MCP-1 in the development of obesity, diabetes, cardiovascular diseases, insulitis, diabetic nephropathy, and diabetic retinopathy. Therapies that specifically or non-specifically inhibit MCP-1 overproduction have been summarized.

Determinants of evolving metabolic and cardiovascular benefit/risk profiles of rosiglitazone therapy during the natural history of diabetes: molecular mechanisms in the context of integrated pathophysiology

Rosiglitazone is a thiazolidinedione, a synthetic PPARγ receptor agonist with insulin-sensitizing properties that is used as an antidiabetic drug. In addition to improving glycemic control through actions in metabolic target tissues, rosiglitazone has numerous biological actions that impact on cardiovascular homeostasis. Some of these actions are helpful (e.g., improving endothelial function), whereas others are potentially harmful (e.g., promoting fluid retention). Since cardiovascular morbidity and mortality are major endpoints for diabetes, it is essential to understand how the natural history of diabetes alters the net benefits and risks of rosiglitazone therapy. This complex issue is an important determinant of optimal use of rosiglitazone and is critical for understanding cardiovascular safety issues. We give special attention to the effects of rosiglitazone in diabetic patients with stable coronary artery disease and the impact of rosiglitazone actions on atherosclerosis and plaque instability. This provides a rational conceptual framework for predicting evolving benefit/risk profiles that inform optimal use of rosiglitazone in the clinical setting and help explain the results of recent large clinical intervention trials where rosiglitazone had disappointing cardiovascular outcomes. Thus, in this perspective, we describe what is known about the molecular mechanisms of action of rosiglitazone on cardiovascular targets in the context of the evolving pathophysiology of diabetes over its natural history.

Preventing the aortic complications of Marfan syndrome: a case-example of translational genomic medicine

The translational path from pharmacological insight to effective therapy can be a long one. We aim to describe the management of Marfan syndrome as a case-example of how pharmacological and genomic insights can contribute to improved therapy. We undertook a literature search for studies of Marfan syndrome, to identify milestones in description, understanding and therapy of the syndrome. From the studies retrieved we then weaved an evidence-based description of progress. Marfan syndrome shows considerable heterogeneity in clinical presentation. It relies on defined clinical criteria with confirmation based on FBN1 mutation testing. Surgical advances have prolonged life in Marfan syndrome. First-line prophylaxis of complications with β-adrenoceptor blockers became established on the basis that reduction of aortic pressure and heart rate would help. Over-activity of proteinases, first suggested in 1980, has since been confirmed by evidence of over-expression of matrix metalloproteinases (MMP), notably MMP-2 and MMP-9. The search for MMP inhibitors led to the evaluation of doxycycline, and both animal studies and small trials, provided early evidence that this widely used antimicrobial agent was useful. Identification of the importance of TGF-β led to evaluation of angiotensin II type I receptor (AT(1) R) blockers with highly promising results. Combination prophylactic therapy would appear rational. Pharmacological and genomic research has provided good evidence that therapy with losartan and doxycycline would prevent the aortic complications of Marfan syndrome. If on-going well designed trials confirm their efficacy, the outlook for Marfan syndrome patients would be improved considerably.

Dietary saturated fat/cholesterol, but not unsaturated fat or starch, induces C-reactive protein associated early atherosclerosis and ectopic fat deposition in diabetic pigs

BACKGROUND

Diabetes is thought to accelerate cardiovascular disease depending on the type of diet. This study in diabetic subjects was performed to investigate the metabolic, inflammatory and cardiovascular effects of nutritional components typically present in a Western, Mediterranean or high glycaemic diet.

METHODS

Streptozotocin-diabetic pigs (~45 kg) were fed for 10 weeks supplemental (40% of dietary energy) saturated fat/cholesterol (SFC), unsaturated fat (UF) or starch (S) in an eucaloric dietary intervention study.

RESULTS

Fasting plasma total, LDL and HDL cholesterol concentrations were 3-5 fold higher (p < 0.01) in SFC compared to UF and S pigs. Fasting plasma NEFA concentrations (mmol/L) were highest (p < 0.05) in SFC (1.09 ± 0.17), intermediate in UF (0.80 ± 0.14) and lowest in S pigs (0.58 ± 0.14) whereas plasma glucose (~13 mmol/L), triglyceride (~0.5 mmol/L) and insulin (~24 pmol/L) concentrations were comparable among SFC, UF and S pigs. The postprandial response area under the curves (AUC, 0-4 h) for glucose but not for insulin and triglyceride responses were intermediate in SFC (617 ± 144) and lowest (p < 0.05) in UF (378 ± 157) compared to S pigs (925 ± 139). Fasting hepatic glucose production, hepatic and peripheral insulin sensitivity and blood pressure were not different among pigs. C-reactive protein (CRP) concentrations (mg/L) were highest (p < 0.05) in SFC (25 ± 4), intermediate in S (21 ± 3) and lowest in UF pigs (14 ± 2). Liver weights, liver and muscle triglyceride concentrations, and the surface area of aorta fatty streaks were highest (p < 0.01) in SFC pigs. A positive correlation between postprandial plasma CRP and aorta fatty streaks was observed in SFC pigs (R(2) = 0.95). Retroperitoneal fat depot weight (g) was intermediate in SFC (260 ± 72), lowest in S (135 ± 51) and highest (p < 0.05) in UF (571 ± 95) pigs.

CONCLUSION

Dietary saturated fat/cholesterol induces inflammation, atherosclerosis and ectopic fat deposition whereas an equally high dietary unsaturated fat load does not induce these abnormalities and shows beneficial effects on postprandial glycaemia in diabetic pigs.

Ocular blood flow analysis detects microvascular abnormalities in impaired glucose tolerance

OBJECTIVE

Waveform analysis has been used to assess vascular resistance and predict cardiovascular events. We aimed to identify microvascular abnormalities in patients with IGT using ocular waveform analysis. The effects of pioglitazone were also assessed.

METHODS

Forty patients with IGT and 24 controls were studied. Doppler velocity recordings were obtained from the central retinal, ophthalmic, and common carotid arteries, and sampled at 200 Hz. A discrete wavelet-based analysis method was employed to quantify waveforms. The RI was also determined. Patients with IGT were randomized to pioglitazone or placebo, and measurements were repeated after 12-week treatment.

RESULTS

In the ocular waveforms, significant differences in power spectra were observed in frequency band 4 (corresponding to frequencies between 6.25 and 12.50 Hz) between groups (p < 0.05). No differences in RI occurred. No association was observed between waveform parameters and fasting glucose or insulin resistance. Pioglitazone had no effect on waveform structure, despite significantly reducing insulin resistance, fasting glucose, and triglycerides (p < 0.05).

CONCLUSIONS

Analysis of ocular Doppler flow waveforms using the discrete wavelet transform identified microvascular abnormalities that were not apparent using RI. Pioglitazone improved glucose, insulin sensitivity, and triglycerides without influencing the contour of the waveforms.

Three-year clinical outcome in type 2 diabetic patients with drug-eluting stents versus bare-metal stents with pioglitazone

AIMS

The aim of this study was to examine outcome subsequent to implantation of bare-metal stents (BMS) with pioglitazone, which are novel insulin-sensitizing agents, and drug-eluting stents (DES) in patients with diabetes.

METHODS AND RESULTS

A total of 139 consecutive Type 2 diabetic patients treated with stent were followed up for 3 years. Data on death, myocardial infarction (MI), target lesion revascularization (TLR), and stent thrombosis were ascertained from January 2003 to January 2006. Eighty-nine patients were treated with a BMS with pioglitazone, and 50 patients were treated with a DES. The incidence of MI was 1.1% in the BMS with pioglitazone group, 4.0% in the DES group [relative risk RR):0.52; 95% CI: 0.10-2.56]. The incidence of TLR was 22.5% in the BMS with pioglitazone group, 28.0% in the DES group (RR 0.89; 95% CI: 0.65-1.22). The incidence of stent thrombosis was 1.0% in the BMS with pioglitazone group, 4.0% in the DES group (RR 0.52; 95% CI: 0.10-2.56). Overall 3-year mortality was similar in the two groups (RR 0.77; 95% CI: 0.34-1.74).

CONCLUSIONS

During 3 years of follow-up, patients treated with BMS with pioglitazone had similar risks of death, TLR, MI, and stent thrombosis compared with patients treated with DES.

Evaluation of in-stent restenosis in the APPROACH trial (Assessment on the Prevention of Progression by Rosiglitazone On Atherosclerosis in diabetes patients with Cardiovascular History)

To determine (1) the medium-term effect of rosiglitazone and glipizide on intra-stent neointima hyperplasia, (2) restenosis pattern as assessed by intra-vascular ultrasound (IVUS) and quantitative coronary angiography (QCA) in patients with T2DM and coronary artery disease. A total of 462 patients with T2DM were randomized to rosiglitazone or glipizide for up to 18 months in the APPROACH trial, and had evaluable baseline and follow-up IVUS examinations. There was no significant difference in the size of plaque behind stent between the rosiglitazone and glipizide groups at 18 months among those treated with a bare metal stent (−5.6 mm³ vs. 1.9 mm³; P = 0.61) or with a drug-eluting stent (12.1 mm³ vs. 5.5 mm³; P = 0.09). Similarly, there was no significant difference in percentage intimal hyperplasia volume between the rosiglitazone and glipizide groups at 18 months among those treated with a bare metal stent (24.1% vs. 19.8%; P = 0.38) or with a drug-eluting stent (9.8% vs. 8.3%; P = 0.57). QCA data (intra-stent late loss, intra-stent diameter stenosis or binary restenosis) were not different between the rosiglitazone and glipizide groups. This study suggests that both rosiglitazone and glipizide have a similar effect on neointimal growth at medium term follow-up, a finding that warrants investigation in dedicated randomized trials.

Differential effect of telmisartan and amlodipine on monocyte chemoattractant protein-1 and peroxisome proliferator-activated receptor-gamma gene expression in peripheral monocytes in patients with essential hypertension

Monocyte chemoattractant protein-1 (MCP-1) and peroxisome proliferator-activated receptor-γ (PPAR-γ) play a significant role in monocyte activation, vascular inflammation, and atherogenesis. Angiotensin receptor blockers and calcium channel blockers are antihypertensive drugs with established efficacy and a favorable safety profile. We investigated the effect of telmisartan--an angiotensin receptor blocker with PPAR-γ agonist activity--and amlodipine on the activation state of peripheral blood monocytes with respect to MCP-1 and PPAR-γ gene expression in hypertensives. We recruited 31 previously untreated patients with essential hypertension who were randomly assigned to receive treatment with telmisartan (n = 16) or amlodipine (n = 15). Blood samples were taken before and 3 months after therapy initiation. Mononuclear cells were isolated and mRNAs of MCP-1 and PPAR-γ were estimated by real-time quantitative reverse transcription-polymerase chain reaction each time. The 2 treatments decreased all blood pressure components significantly (p <0.001). In contrast, in the amlodipine group, MCP-1 gene expression was significantly downregulated after treatment with telmisartan (from 21.4 ± 20.5 to 8.1 ± 6.5, p = 0.009), whereas the amlodipine group did not show any significant change (12.5 ± 8.5 vs 17.6 ± 16.4, p = NS). In addition, PPAR-γ mRNA levels showed a significant increase in telmisartan-treated patients (from 20 ± 18.5 to 42.6 ± 36, p = 0.006) and no significant alterations in the amlodipine group (from 29.6 ± 42.5 to 24.2 ± 27.7, p = NS). In conclusion, treatment with telmisartan results in a significant attenuation of MCP-1 gene expression and an increase of PPAR-γ gene expression in peripheral monocytes in patients with essential hypertension. Our findings may provide new insights into the cardiovascular protection of telmisartan in hypertensives.

Rosiglitazone (peroxisome proliferator-activated receptor-gamma) counters hypertension and adverse cardiac and vascular remodeling in 2K1C hypertensive rats

Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonists have been shown controlling blood pressure (BP) in spontaneously hypertensive rats and salt-sensitive hypertensive rats. The present study aims to test the hypothesis that PPAR-gamma agonist rosiglitazone has beneficial effects on cardiac and vascular adverse remodeling in a model of renovascular hypertension (two-kidneys-one-clip, 2K1C model). Wistar rats were divided into four groups (n=6): SHAM group, 2K1C, 2K1C+HYD (treated with hydralazine for 5 weeks) and 2K1C+ROSI (treated with rosiglitazone for 5 weeks). The left ventricle (LV), thoracic aorta (Ao) and common carotid artery (CCA) were analyzed. The BP did not show significant difference at the end of the experiment in groups 2K1C+ROSI, 2K1C+HYD and SHAM. The LV mass was smaller in 2K1C+ROSI compared with the other groups. The intima-media thickness was smaller in 2K1C+ROSI compared with untreated 2K1C ones, but not in 2K1C+HYD; 2K1C and 2K1C+HYD showed smaller Ao and CCA density of smooth muscle cell nuclei, and smaller surface density of the elastic lamellae than SHAM. The Ao and CCA circumferential wall tension and tensile stress were greater in 2K1C than in SHAM. Hypertrophied cardiomyocytes were seen in 2K1C, but not in 2K1C+ROSI and SHAM; 2K1C+ROSI had enhanced volume and length densities of intramyocardial arteries than 2K1C. The volume density of cardiac interstitium was greater in 2K1C and 2K1C+HYD than in SHAM. In conclusion, PPAR-gamma agonist rosiglitazone has beneficial effects controlling BP, reducing vascular adverse remodeling, and preserving intramyocardial vascularization in renovascular hypertensive rats (2K1C model).

Combination therapy for treatment or prevention of atherosclerosis: focus on the lipid-RAAS interaction

Large clinical trials demonstrate that control of blood pressure or hyperlipidemia reduces risk for cardiovascular events by approximately 30%. Factors that may further reduce remaining risk are not definitively established. One potential target is atherosclerosis, a crucial feature in the pathogenesis of cardiovascular diseases whose development is determined by multiple mechanism including complex interactions between endothelial dysfunction and insulin resistance. Reciprocal relationships between endothelial dysfunction and insulin resistance as well as cross-talk between hyperlipidemia and the rennin-angiotensin-aldosterone system may contribute to development of atherosclerosis. Therefore, one appealing strategy for prevention or treatment of atherosclerosis may be to simultaneously address several risk factors with combination therapies that target multiple pathogenic mechanisms. Combination therapy with statins, peroxisome proliferators-activated receptor agonists, and rennin-angiotensin-aldosterone system blockers demonstrate additive beneficial effects on endothelial dysfunction and insulin resistance when compared with monotherapies in patients with cardiovascular risk factors. Additive beneficial effects of combined therapy are mediated by both distinct and interrelated mechanisms, consistent with both pre-clinical and clinical investigations. Thus, combination therapy may be an important concept in developing more effective strategies to treat and prevent atherosclerosis, coronary heart disease, and co-morbid metabolic disorders characterized by endothelial dysfunction and insulin resistance.

Peroxisome proliferator-activated receptor gamma (PPAR) agonism reduces the insulin-stimulated increase in circulating interleukin-6 in GH replaced GH-deficient adults

CONTEXT

Peroxisome proliferator-activated receptor gamma (PPARgamma) agonists modify cardiovascular risk factors and inflammatory markers in patients with type 2 diabetes. GH treatment in GH-deficient (GHD) patients may cause insulin resistance and exerts ambiguous effects on inflammatory markers.

OBJECTIVE

To investigate circulating markers of inflammation and endothelial function in GH replaced GHD patients before and after 12 weeks administration of either pioglitazone 30 mg/day (N = 10) or placebo (N = 10) in a randomized double-blind parallel design.

METHODS

Circulating levels of interleukins (ILs)-1beta, IL-2, IL-4, IL-6, IL-8, IL-10, tumour necrosis factor (TNF)-alpha, high sensitivity C-reactive protein, vascular cell adhesion molecule-I, and osteoprotegerin (OPG) were measured in the basal state and after a 2.5 h hyperinsulinaemic euglycaemic clamp.

RESULTS

Insulin sensitivity improved in the group receiving PPARgamma agonist (P = 0.03). Serum IL-6 levels increased by 114 +/- 31% (mean +/- SE) in the entire group (N = 20) following the hyperinsulinaemic euglycaemic clamp (P = 0.01) performed at study start. Twelve weeks of PPARgamma agonist treatment significantly abrogated this insulin-stimulated increment in IL-6 levels compared to placebo (P = 0.01). Furthermore PPARgamma agonist treatment significantly lowered basal IL-4 levels (P < 0.05).

CONCLUSIONS

(i) IL-6 levels increase during a hyperinsulinaemic clamp in GH replaced patients (ii) This increase in IL-6 is abrogated by PPARgamma agonist treatment (iii) we hypothesize that PPARgamma agonist-induced improvement of insulin sensitivity may obviate a compensatory rise in IL-6.

Targeting PPAR receptors in the airway for the treatment of inflammatory lung disease

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that belong to the nuclear hormone receptor superfamily. PPARgamma regulates several metabolic pathways by binding to sequence-specific PPAR response elements in the promoter region of genes involved in lipid biosynthesis and glucose metabolism. However, more recently PPARgamma, PPARalpha and PPARbeta/delta agonists have been demonstrated to exhibit anti-inflammatory and immunomodulatory properties thus opening up new avenues for research. The actions of PPARgamma and PPARalpha activation are thought to be due to their ability to down regulate pro-inflammatory gene expression and inflammatory cell functions, and as such makes them an attractive target for novel drug intervention. Interestingly, PPARbeta/delta has been shown to be involved in wound healing, angiogenesis, lipid metabolism and thrombosis. In this review we will focus on the data describing the beneficial effects of these ligands in the airway and in the pulmonary vasculature and in vivo in animal models of allergic and occupational asthma, chronic obstructive pulmonary disease and pulmonary fibrosis. A clinical trial is underway to examine the effect of rosiglitazone in asthma patients and the outcome of this trial is awaited with much anticipation. In conclusion, PPARs are novel targets for lung disease and continued work with these ligands may result in a potential new treatment for chronic inflammatory lung diseases.

Pioglitazone inhibits Toll-like receptor expression and activity in human monocytes and db/db mice

Toll-like receptors (TLRs) are key innate immune sensors of endogenous damage signals and play an important role in inflammatory diseases like diabetes and atherosclerosis. Pioglitazone (PIO), a peroxisome proliferator-activated receptor (PPAR)-gamma agonist, has been reported to be an antiinflammatory agent. Thus, in the present study, we examined the antiinflammatory effects of PIO on TLR2 and TLR4 expression in human monocytes exposed to Pam3CSK4 (Pam; TLR2 ligand) and purified lipopolysaccharide (LPS; TLR4 ligand) using flow cytometry and real-time RT-PCR. Monocytes were isolated from healthy human volunteers and pretreated with PIO (1 microM) followed by Pam (170 ng/ml) and LPS (160 ng/ml) challenge. PIO significantly decreased Pam- and LPS-induced TLR2 (-56%) and TLR4 (-78%) expression (P < 0.05). In addition, PIO decreased TLR ligand-induced nuclear factor-kappaB activity (-63%), IL-1beta (-50%), IL-6 (-52%), monocyte chemoattractant protein-1(-83%), and TNF-alpha (-87%) compared with control. Next, PIO-treated db/db mice (n = 6/group) showed decreased TLR2 (-60%) and TLR4 (-45%) expression in peritoneal macrophages compared with vehicle control mice (P < 0.001) with associated decrease in MyD88-dependent signaling and nuclear factor-kappaB activation. Data suggest that Pam- and LPS-induced TLR2 and TLR4 expression are inhibited by PIO in human monocytes and db/db mice. Thus, we define a novel pathway by which PIO could induce antiinflammatory effects.

PPARgamma agonist, rosiglitazone, regulates angiotensin II-induced vascular inflammation through the TLR4-dependent signaling pathway

Atherosclerosis is increasingly recognized as a chronic inflammatory disease. Angiotensin II (Ang II) is a critical factor in inflammatory responses, so as to promote the pathogenesis of atherosclerosis. Toll-like receptor 4 (TLR4) activates signaling pathways leading to the expression of pro-inflammatory cytokines implicated in the etiology of atherosclerosis. Peroxisome proliferator-activated receptor gamma (PPARgamma) agonists are considered to be important in modulating vascular inflammation and atherosclerosis. Herein, we investigated the modulatory effects of rosiglitazone on Ang II-mediated inflammatory responses both in vivo and in vitro. We also examined whether TLR4-dependent signaling pathway was involved in the inhibitory effects of rosiglitazone on Ang II-induced pro-inflammatory responses in vascular smooth muscle cells (VSMCs). Male Sprague-Dawley rats received Ang II by subcutaneous infusion and/or rosiglitazone per os for 7 days. Systolic blood pressure rise in Ang II-infused rats was attenuated by rosiglitazone. Rosiglitazone also reduced Ang II-induced generation of pro-inflammatory mediators (TLR4, matrix metalloproteinase-9 and tumor necrosis factor-alpha), but enhanced production of anti-inflammatory mediators (PPARgamma and 6-keto-PGF(1alpha)) both in vivo and in vitro. Furthermore, treatment of VSMCs with both the TLR4 inhibitor and TLR4 small-interfering RNA (siRNA) showed that the modulatory effects of rosiglitazone on Ang II-mediated inflammatory responses in VSMCs were related to TLR4. Treatment of the cells with rosiglitazone had little effect on Ang II receptors expression (AT1 and AT2), but downregulated AT1-dependent ERK1/2 activation. Then, treatment of VSMCs with TLR4 siRNA, interferon-gamma-inducible protein 10 (IP-10) siRNA and with the special protein kinase C (PKC) inhibitor further revealed that the signaling pathway (TLR4/IP-10/PKC/NF-kappaB) was involved in the inhibitory effects of rosiglitazone on Ang II-induced pro-inflammatory responses in VSMCs. In conclusion, TLR4 may be a drug target involved in the ameliorative effects of PPARgamma agonist, rosiglitazone, on Ang II-mediated inflammatory responses in VSMCs. Moreover, rosiglitazone exerts its anti-inflammatory effect by interfering with the TLR4-dependent signaling pathway (ERK1/2/TLR4/IP-10/PKC/NF-kappaB) to prevent and treat atherosclerotic diseases.

The effects of thiazolidinediones on blood pressure levels – A systematic review

Insulin resistance has been proposed to be the underlying disorder of the so-called metabolic or insulin resistance syndrome, which represents the clustering in the same individual of several cardiovascular risk factors, such as type 2 diabetes mellitus, hypertension, abdominal obesity, elevated triglycerides and low high-density lipoprotein-cholesterol. As far as the connection of insulin resistance and compensatory hyperinsulinaemia with hypertension is concerned, a number of mechanisms possibly linking these disturbances have been described, such as activation of sympathetic nervous system, enhancement of renal sodium reabsorption, or impairment of endothelium-dependent vasodilatation. Thiazolidinediones (TZDs) constitute a class of oral antihyperglycaemic agents that act by decreasing insulin resistance, and apart from their action on glycaemic control, they have been also reported to exert beneficial effects on other parameters of the metabolic syndrome. In particular, during recent years a considerable number of animal and human studies have shown that the use of TZDs was associated with usually small but significant reductions of blood pressure (BP) levels. Since a possible beneficial action of these compounds on BP could be of particular value for patients with the metabolic syndrome, this review aimed to summarize and evaluate the literature data in the field, derived either from studies that just examined BP levels among other parameters or from studies that were specifically designed to determine the effect of a TZD on BP.

Significance of peroxisome proliferator-activated receptors in the cardiovascular system in health and disease

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated nuclear transcription factors that belong to the nuclear receptor superfamily. Three isoforms of PPAR have been identified, alpha, delta and gamma, which play distinct roles in the regulation of key metabolic processes, such as glucose and lipid redistribution. PPARalpha is expressed predominantly in the liver, kidney and heart, and is primarily involved in fatty acid oxidation. PPARgamma is mainly associated with adipose tissue, where it controls adipocyte differentiation and insulin sensitivity. PPARdelta is abundantly and ubiquitously expressed, but as yet its function has not been clearly defined. Activators of PPARalpha (fibrates) and gamma (thiazolidinediones) have been used clinically for a number of years in the treatment of hyperlipidaemia and to improve insulin sensitivity in diabetes. More recently, PPAR activation has been found to confer additional benefits on endothelial function, inflammation and thrombosis, suggesting that PPAR agonists may be good candidates for the treatment of cardiovascular disease. In this regard, it has been demonstrated that PPAR activators are capable of reducing blood pressure and attenuating the development of atherosclerosis and cardiac hypertrophy. This review will provide a detailed discussion of the current understanding of basic PPAR physiology, with particular reference to the cardiovascular system. It will also examine the evidence supporting the involvement of the different PPAR isoforms in cardiovascular disease and discuss the current and potential future clinical applications of PPAR activators.