Rapid effect of single-dose rosiglitazone treatment on endothelial function in healthy men with normal glucose tolerance: data from a randomised, placebo-controlled, double-blind study

The impact of acute rosiglitazone on insulin pharmacokinetics at the blood-brain barrier

INTRODUCTION

CNS insulin levels are decreased and insulin receptor signalling is dampened in Alzheimer's disease (AD). Increasing CNS insulin levels through a variety of methods has been shown to improve memory. Indeed, medications routinely used to improve insulin resistance in type 2 diabetes are now being repurposed for memory enhancement. CNS insulin is primarily derived from the circulation, by an active transport system at the blood-brain barrier (BBB). The goal of this study was to determine whether rosiglitazone (RSG), a drug used to improve insulin sensitivity in type 2 diabetes, could enhance insulin transport at the BBB, as a potential therapeutic for improving memory.

METHODS

Using radioactively labelled insulin and the multiple-time regression analysis technique, we measured the rate of insulin BBB transport and level of vascular binding in mice pretreated with vehicle or 10 µg RSG in the presence or absence of an insulin receptor inhibitor.

RESULTS

Although we found acute RSG administration does not affect insulin transport at the BBB, it does restore BBB vascular binding of insulin in an insulin receptor-resistant state.

CONCLUSIONS

Acute RSG treatment does not alter insulin BBB transport in healthy mice but can restore insulin receptor binding at the BBB in an insulin-resistant state.

Fibroblast growth factor 21 attenuates hypoxia-induced pulmonary hypertension by upregulating PPARγ expression and suppressing inflammatory cytokine levels

Hypoxia-induced pulmonary hypertension (HPH) is a progressive disease characterized by a sustained, elevated pulmonary arterial pressure and vascular remodeling. The latter pathogenesis mainly involves overproliferation of pulmonary artery smooth muscle cells (PASMCs). Fibroblast growth factor 21 (FGF21) has recently emerged as a novel regulator that prevents cardiac hypertrophic remodeling. However, its possible role in pulmonary remodeling remains unclear. The activation of peroxisome proliferator activated receptor γ (PPARγ) is reported to attenuate HPH by suppressing proliferative signals. Loss of PPARγ in the lung contributes to abnormal proliferation of PASMCs. FGF21 is a key regulator of PPARγ activity in adipocytes, but its role has not been elucidated in PASMCs. Therefore, we hypothesized that FGF21 may confer therapeutic effects in HPH by upregulating the expression of PPARγ. Sprague-Dawley rats were exposed to hypoxia and treated with FGF21 for 4 weeks. In parallel, hypoxic conditions and FGF21 were administered to rat PASMCs for 48 h. FGF21 attenuated the hypoxia-induced elevation in mean pulmonary arterial pressure (mPAP), right ventricular hypertrophy (RVH), medial thickening and overproliferation of PASMCs. Furthermore, FGF21 abrogated the reductions in PPARγ expression and increases in TNF-α, IL-1 and IL-6 levels in PASMC culture media. Collectively, these results demonstrate that FGF21 could potentially attenuate the pathogenic derangements of HPH by targeting PPARγ and inflammatory cytokines.

Thiazolidinediones improve flow-mediated dilation: a meta-analysis of randomized clinical trials

AIMS

Thiazolidinediones administration is assumed to be related with an improvement of endothelial dysfunction (ED); nevertheless, previous studies have been inconsistent. For this reason, the present meta-analysis was directed to estimate if thiazolidinediones were related to endothelial dysfunction improvement by using flow-mediated dilation (FMD) measurement.

METHODS

Literature search of the PubMed, the Cochrane Library, the Web of Science, and the Scopus databases was performed covering the period until July 01, 2015, for randomized clinical trials that investigated an influence of thiazolidinediones on FMD. For the calculation of the pooled overall effect, a random effect model was used. Meta-regression and subgroup analyses were performed to evaluate the impact of study characteristics on the effect of thiazolidinediones administration on FMD.

RESULTS

This meta-analysis included 16 studies with 812 subjects. The obtained results demonstrated an improvement of endothelial dysfunction measured with FMD (16 studies, 812 subjects; WMD: 2.4 %, 95 % CI = 1.1 to 3.69 %; p = 0.0003). The significant heterogeneity was noted (I (2) = 95 %, p < 0.00001). Subgroup analysis demonstrated that pioglitazone and rosiglitazone were able to improve FMD. Also, thiazolidinediones improved FMD if treatment was longer than 12 weeks and if patients were younger than 65 years. Additionally, a lipid profile was found to influence thiazolidinediones effect on FMD.

CONCLUSION

The results of this meta-analysis demonstrated that thiazolidinediones were able to improve FMD, which in clinical terms can be further translated to the improvement of an impaired endothelial function. Nevertheless, the link between FMD and its predictive clinical relevance still requires further clarification.

Cardiovascular Risk in Diabetes Mellitus: Complication of the Disease or of Antihyperglycemic Medications

Cardiovascular disease is the principal complication and the leading cause of death for patients with diabetes (DM). The efficacy of antihyperglycemic treatments on cardiovascular disease risk remains uncertain. Cardiovascular risk factors are affected by antihyperglycemic medications, as are many intermediate markers of cardiovascular disease. Here we summarize the evidence assessing the cardiovascular effects of antihyperglycemic medications with regard to risk factors, intermediate markers of disease, and clinical outcomes.

Rosiglitazone Influences the Expression of Leukocyte Adhesion Molecules and CD14 Receptor in Type 2 Diabetes Mellitus Patients

Diabetes mellitus is associated with increased inflammatory response, which may contribute to atherosclerosis progression. Experimental results demonstrated anti-inflammatory activity of glitazones; their effect on leukocyte adhesion molecules has not been studied to date. We therefore studied the effect of rosiglitazone treatment on leukocyte surface expression of adhesion molecules in patients with type 2 diabetes mellitus and compared our results with findings in healthy subjects. 33 subjects with type 2 diabetes and 32 healthy controls were included; patients were examined at baseline and after 5 months of rosiglitazone treatment (4 mg/d). Leukocyte expression of adhesion molecules LFA-1, CD18 and ICAM-1 was quantified using flow cytometry; in addition, CD14 (lipopolysaccharide receptor) expression was analyzed as a marker of nonspecific immunity. The expression of examined molecules at baseline was higher in patients compared to controls. Despite only mild decrease in blood glucose, rosiglitazone treatment induced substantial decrease of CD18 and CD14 expression and borderline decrease of LFA-1 and ICAM-1 expression (on monocytes only). We thus observed improvement in the expression of leukocyte inflammatory markers after rosiglitazone treatment. This effect is supposed to be mediated by direct effect of rosiglitazone on PPAR-γ receptors on leukocytes.

Effects of age on noninvasive assessments of vascular function in nonhuman primates: implications for translational drug discovery

BACKGROUND

Endothelium-dependent flow mediated dilation (FMD) and pulse-wave velocity (PWV), are used as measures of vascular health and predictors of cardiovascular risk in clinical studies, and both are age-dependent. Numbers of circulating endothelial microparticles (EMPs) and endothelial progenitor cells (EPCs) are also associated with cardiovascular risk, but independent of age in humans. The use of these measurements for pre-clinical assessment of drug cardiovascular safety and efficacy in non-human primates (NHPs) may promote the translation of drug-induced effects on vascular function to clinic outcomes. However, in NHPs, the age effects on the non-invasive measurements of FMD and PWV and the relationship of EMPs/EPCs with FMD are unknown.

METHODS

A non-invasive, clinically-relevant approach to assess FMD and PWV was used to examine their relationship with age and with EMPs/EPCs in NHPs. The effects on FMD of nicotine and rosiglitazone were evaluated in senescent primates in an effort to validate our FMD method for pre-clinical assessment of vascular function.

RESULTS

FMD and PWV methods were established in a colony (n = 25) of metabolically healthy, cynomolgus monkeys ranging in age from 6 to 26 years. FMD, defined as the percent change, at 1 min of cuff release, from baseline vascular diameter (0.15 ± 0.03 cm), had a strong, negative correlation with age (r = -0.892, p < 0.0001), ranging from 6% to 33%. PWV positively correlated with age (r = 0.622, p < 0.002) in the same healthy monkeys. Nicotine and rosiglitazone, were evaluated in subsets of senescent primates (mean age 16.3 ± 1.5[SEM] years). Rosiglitazone significantly improved FMD (21.0 ± 1.6% vs. vehicle 16.3 ± 1.6%, p < 0.01) without changing baseline diameters, and coincided with a significant increase in circulating numbers of endothelial progenitor cells (CD45-CD31 + CD34 + VEGFR2+ 7.1 ± 1.3 vs. 4.8 ± 1.1 counts/μl) and a decrease in endothelial microparticles (CD45-CD42a-CD54+ 26.7 ± 11.1 vs. 62.2 ± 9.8 counts/μl)(p < 0.05). Conversely, FMD was significantly reduced with nicotine (8.7 ± 1.4% vs. vehicle 20.1 ± 2.2%, p < 0.05).

CONCLUSIONS

Adult NHPs demonstrate the characteristic linear relationship between age and vascular function using the non-invasive clinically-related measurements of FMD and PWV. However, numbers of circulating EMPs and EPCs did not correlate with age. Endothelial function assessed with FMD, together with EMPs/EPCs assessment, may serve as a novel approach for translational research and therapeutic discovery. Age should be considered in the study design or data analyses when FMD or PWV is used in NHPs.

Relaxation of human pulmonary arteries by PPARγ agonists

It has been suggested that activation of nuclear peroxisome proliferator-activated receptors γ (PPARγ) may represent a new strategy for the treatment of pulmonary arterial hypertension. It has been demonstrated that PPARγ activation relaxed the isolated mouse pulmonary artery. The aims of the present study were to examine whether and to which extent the two PPARγ agonists rosiglitazone and pioglitazone relax the isolated human pulmonary artery and to investigate the underlying mechanism(s). Isolated human pulmonary arteries were obtained from patients without clinical evidence of pulmonary hypertension during resection of lung carcinoma. Vasodilatory effects of PPARγ agonists were examined on endothelium-intact or endothelium-denuded vessels preconstricted with the thromboxane prostanoid receptor agonist U-46619. Rosiglitazone and pioglitazone (0.01–100 μM) caused a concentration- and/or time-dependent full relaxation of U-46619-preconstricted vessels. The rosiglitazone-induced relaxation was attenuated by the PPARγ antagonist GW9662 1 μM, endothelium denudation, the nitric oxide synthase inhibitor L-NAME 300 μM, the cyclooxygenase inhibitor indomethacin 10 μM, and the K_ATP channel blocker glibenclamide 10 μM. The prostacyclin IP receptor antagonist RO1138452 1 μM shifted the concentration–response curve for rosiglitazone to the right. The PPARγ agonists pioglitazone and rosiglitazone relax human pulmonary arteries. The rosiglitazone-induced vasorelaxation is partially endothelium-dependent and involves PPARγ receptors, arachidonic acid degradation products, nitric oxide, and K_ATP channels. Thus, the relaxant effect of PPARγ agonists in human pulmonary arteries may represent a new therapeutic target in pulmonary arterial hypertension.

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.

Rosiglitazone Restores Endothelial Dysfunction in a Rat Model of Metabolic Syndrome through PPARγ- and PPARδ-Dependent Phosphorylation of Akt and eNOS

Vascular endothelial dysfunction has been demonstrated in metabolic syndrome (MS). Chronic administration of rosiglitazone ameliorates endothelial dysfunction through PPARγ-mediated metabolic improvements. Recently, studies suggested that single dose of rosiglitazone also has direct vascular effects, but the mechanisms remain uncertain. Here we established a diet-induced rat model of MS. The impaired vasorelaxation in MS rats was improved by incubating arteries with rosiglitazone for one hour. Importantly, this effect was blocked by either inhibition of PPARγ or PPARδ. In cultured endothelial cells, acute treatment with rosiglitazone increased the phosphorylation of Akt and eNOS and the production of NO. These effects were also abolished by inhibition of PPARγ, PPARδ, or PI3K. In conclusion, rosiglitazone improved endothelial function through both PPARγ- and PPARδ-mediated phosphorylation of Akt and eNOS, which might help to reconsider the complex effects and clinical applications of rosiglitazone.

Acute rosiglitazone treatment is cardioprotective against ischemia-reperfusion injury by modulating AMPK, Akt, and JNK signaling in nondiabetic mice

Rosiglitazone (RGZ), a peroxisome proliferator-activated receptor (PPAR)-γ agonist, has been demonstrated to possess cardioprotective properties during ischemia-reperfusion. However, this notion remains controversial as recent evidence has suggested an increased risk in cardiac events associated with long-term use of RGZ in patients with type 2 diabetes. In this study, we tested the hypothesis that acute RGZ treatment is beneficial during I/R by modulating cardioprotective signaling pathways in a nondiabetic mouse model. RGZ (1 μg/g) was injected intravenously via the tail vein 5 min before reperfusion. Myocardial infarction was significantly reduced in mice treated with RGZ compared with vehicle controls (8.7% ± 1.1% vs. 20.2% ± 2.5%, P < 0.05). Moreover, isolated hearts were subjected to 20 min of global, no-flow ischemia in an ex vivo heart perfusion system. Postischemic recovery was significantly improved with RGZ treatment administered at the onset of reperfusion compared with vehicle ( P < 0.001). Immunoblot analysis data revealed that the levels of both phospho-AMP-activated protein kinase (Thr172) and phospho-Akt (Ser473) were significantly upregulated when RGZ was administered 5 min before reperfusion compared with vehicle. On the other hand, inflammatory signaling [phospho-JNK (Thr183/Tyr185)] was significantly downregulated as a result of RGZ treatment compared with vehicle ( P < 0.05). Intriguingly, pretreatment with the selective PPAR-γ inhibitor GW-9662 (1 μg/g iv) 10 min before reperfusion significantly attenuated these beneficial effects of RGZ on the ischemic heart. Taken together, acute treatment with RGZ can reduce ischemic injury in a nondiabetic mouse heart via modulation of AMP-activated protein kinase, Akt, and JNK signaling pathways, which is dependent on PPAR-γ activation.