Rosiglitazone prevents free fatty acid-induced vascular endothelial dysfunction

Transcriptome-centric approach to the derivation of adverse outcome pathway networks of vascular dysfunction after long-term low-level exposure of human endothelial cells to dibutyl phthalate

Dibutyl phthalate (DBP) is an endocrine disruptor that adversely affects reproduction; however, evidence suggests it can also impact other systems, including vascular function. The mechanisms underlying DBP-induced vascular dysfunction, particularly after long-term low-level exposure of endothelial cells to this phthalate, remain largely unknown. To address this gap, we used experimentally derived data on differentially expressed genes (DEGs) obtained after 12 weeks of exposure of human vascular endothelial cells EA.hy926 to the concentrations of DBP to which humans are routinely exposed (10-9 M, 10-8 M, and 10-7 M) and various computational tools and manual data curation to build the first adverse outcome pathway (AOP) network relevant to DBP-induced vascular toxicity. DEGs were used to infer transcription factors (molecular initiating events) and molecular functions and biological processes (key events, KEs) using the Enrichr database. The AOP-helpFinder 2.0, an artificial intelligence-based web tool, was used to link genes and KEs and assign confidence scores to co-occurred terms. We constructed the AOP networks using Cytoscape and then manually arranged KEs to depict the flow of mechanistic information across different levels of network organization. An AOP network was created for each DBP concentration, revealing several distinct high-confidence subnetworks that could be involved in DBP-induced vascular toxicity: the insulin-like growth factor subnetwork for 10-7 M DBP, the CXCL8-dependent chemokine subnetwork for 10-8 M DBP, and the fatty acid subnetwork for 10-9 M DBP. We also developed an AOP network providing a mechanistic insight into the dose-dependent effects of DBP in endothelial cells leading to vascular dysfunction. In summary, we present novel putative AOP networks describing the mechanistic flow of information involved in DBP-induced vascular dysfunction in a long-term low-level exposure scenario.

Novel lipid biomarkers and ratios as risk predictors for premature coronary artery disease: A retrospective analysis of 2952 patients

This study examined the associations between emerging lipid biomarkers (small dense low-density lipoprotein cholesterol [sdLDL-C), lipoprotein(a) [Lp(a)], and free fatty acids [FFA]), two ratios (sdLDL-C/LDL-C and the triglyceride-glucose [TyG) index), and the Gensini score (GS) in patients with premature coronary artery disease (PCAD) in relation to the extent of coronary stenosis. The authors evaluated a cohort of 2952 individuals undergoing coronary angiography (CAG), encompassing those with PCAD (n = 1749), late-onset coronary artery disease (LCAD; n = 328), and non-coronary artery disease (non-CAD; n = 575). Noteworthy differences were observed in the levels of the novel lipid biomarkers and ratio indexes among the PCAD, LCAD, and non-CAD groups (p < .05). Multiple logistic regression analyses pinpointed Lp(a) (OR = 2.62, 95% CI 1.22-5.63, p = .014) and the TyG index (OR = 2.53, 95% CI 1.08-5.93, p = .033) as independent risk factors for PCAD. Furthermore, these biomarkers and ratio indexes discerned substantial distinctions among PCAD patients with varying GS (p < .05). Consequently, these markers can proficiently anticipate the gravity of coronary artery stenosis (GS > 40) in PCAD patients, as evidenced by the ROC analysis. In conclusion, sdLDL-C, Lp(a), FFA, and the sdLDL-C/LDL-C and TyG indexes have considerable potential as risk and diagnostic markers for coronary artery stenosis in individuals afflicted with PCAD.

Plasma Free Fatty Acid Concentration as a Modifiable Risk Factor for Metabolic Disease

Plasma free fatty acid (FFA) concentration is elevated in obesity, insulin resistance (IR), non-alcoholic fatty liver disease (NAFLD), type 2 diabetes (T2D), and related comorbidities such as cardiovascular disease (CVD). Furthermore, experimentally manipulating plasma FFA in the laboratory setting modulates metabolic markers of these disease processes. In this article, evidence is presented indicating that plasma FFA is a disease risk factor. Elevations of plasma FFA can promote ectopic lipid deposition, IR, as well as vascular and cardiac dysfunction. Typically, elevated plasma FFA results from accelerated adipose tissue lipolysis, caused by a high adipose tissue mass, adrenal hormones, or other physiological stressors. Reducing an individual’s postabsorptive and postprandial plasma FFA concentration is expected to improve health. Lifestyle change could provide a significant opportunity for plasma FFA reduction. Various factors can impact plasma FFA concentration, such as chronic restriction of dietary energy intake and weight loss, as well as exercise, sleep quality and quantity, and cigarette smoking. In this review, consideration is given to multiple factors which lead to plasma FFA elevation and subsequent disruption of metabolic health. From considering a variety of medical conditions and lifestyle factors, it becomes clear that plasma FFA concentration is a modifiable risk factor for metabolic disease.

Nonesterified fatty acids, cognitive decline, and dementia

PURPOSE OF REVIEW

Dementia is rapidly growing as sources of morbidity and mortality as the US population ages, but its pathophysiology remains poorly understood. As a result, no disease-modifying treatments currently exist. We review the evidence that nonesterified fatty acids may play a key role in this condition.

RECENT FINDINGS

Nonesterified fatty acids appear to influence several pathways leading to dementia. In addition to their vascular effects, these moieties cross the blood-brain barrier, where they are toxic to several cell types. They may also influence insulin metabolism in the brain directly and indirectly, and some drugs that lower circulating levels appear to slow cognitive decline and brain atrophy in diabetes.

SUMMARY

Nonesterified fatty acids may contribute to dementia, much as they do to diabetes and cardiovascular disease. Several therapeutic agents lower circulating levels of nonesterified fatty acids and should be tested for their potential preventive effects on cognitive decline in healthy populations before irreversible neuronal attrition occurs.

Impact of Acipimox Therapy on Free Fatty Acid Efflux and Endothelial Function in the Metabolic Syndrome: A Randomized Trial

OBJECTIVE

Insulin resistance is associated with increased lipolysis and elevated concentrations of free fatty acids (FFA), which in turn contribute to impaired vascular function. It was hypothesized that lowering FFA with acipimox, a nicotinic acid derivative that impairs FFA efflux, would improve endothelial function, measured by flow-mediated dilation (FMD), in individuals with metabolic syndrome.

METHODS

A total of 18 participants with metabolic syndrome and 17 healthy controls were enrolled and treated with acipimox 250 mg orally every 6 hours or placebo for 7 days in a randomized, double-blind, crossover trial.

RESULTS

Acipimox reduced FFA concentrations among individuals with metabolic syndrome to near normal levels (P = 0.01), but there was no change among healthy controls (P = 0.17). Acipimox did not improve endothelial-dependent FMD in either group (metabolic syndrome: P = 0.42; healthy controls: P = 0.16), although endothelial-independent nitroglycerin-mediated dilation among those with metabolic syndrome tended to increase (20.3%, P = 0.06). There were no changes in blood lipids or markers of inflammation following therapy. There was minimal correlation between change in FMD and baseline measures of BMI ( ρ = -0.09) or waist circumference ( ρ = -0.15).

CONCLUSIONS

In groups with normal or elevated baseline FFA, short-term reductions do not improve endothelial function assessed by FMD.

Exploration and Development of PPAR Modulators in Health and Disease: An Update of Clinical Evidence

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors that govern the expression of genes responsible for energy metabolism, cellular development, and differentiation. Their crucial biological roles dictate the significance of PPAR-targeting synthetic ligands in medical research and drug discovery. Clinical implications of PPAR agonists span across a wide range of health conditions, including metabolic diseases, chronic inflammatory diseases, infections, autoimmune diseases, neurological and psychiatric disorders, and malignancies. In this review we aim to consolidate existing clinical evidence of PPAR modulators, highlighting their clinical prospects and challenges. Findings from clinical trials revealed that different agonists of the same PPAR subtype could present different safety profiles and clinical outcomes in a disease-dependent manner. Pemafibrate, due to its high selectivity, is likely to replace other PPARα agonists for dyslipidemia and cardiovascular diseases. PPARγ agonist pioglitazone showed tremendous promises in many non-metabolic disorders like chronic kidney disease, depression, inflammation, and autoimmune diseases. The clinical niche of PPARβ/δ agonists is less well-explored. Interestingly, dual- or pan-PPAR agonists, namely chiglitazar, saroglitazar, elafibranor, and lanifibranor, are gaining momentum with their optimistic outcomes in many diseases including type 2 diabetes, dyslipidemia, non-alcoholic fatty liver disease, and primary biliary cholangitis. Notably, the preclinical and clinical development for PPAR antagonists remains unacceptably deficient. We anticipate the future design of better PPAR modulators with minimal off-target effects, high selectivity, superior bioavailability, and pharmacokinetics. This will open new possibilities for PPAR ligands in medicine.

Changes in Plasma Free Fatty Acids Associated with Type-2 Diabetes

Type 2 diabetes mellitus (T2DM) is associated with increased total plasma free fatty acid (FFA) concentrations and an elevated risk of cardiovascular disease. The exact mechanisms by which the plasma FFA profile of subjects with T2DM changes is unclear, but it is thought that dietary fats and changes to lipid metabolism are likely to contribute. Therefore, establishing the changes in concentrations of specific FFAs in an individual’s plasma is important. Each type of FFA has different effects on physiological processes, including the regulation of lipolysis and lipogenesis in adipose tissue, inflammation, endocrine signalling and the composition and properties of cellular membranes. Alterations in such processes due to altered plasma FFA concentrations/profiles can potentially result in the development of insulin resistance and coagulatory defects. Finally, fibrates and statins, lipid-regulating drugs prescribed to subjects with T2DM, are also thought to exert part of their beneficial effects by impacting on plasma FFA concentrations. Thus, it is also interesting to consider their effects on the concentration of FFAs in plasma. Collectively, we review how FFAs are altered in T2DM and explore the likely downstream physiological and pathological implications of such changes.

ADMA and NT pro-BNP are associated with overall mortality in elderly

BACKGROUND

Increased asymmetrical dimethylarginine (ADMA) and NT pro-BNP concentrations have been associated with mortality in patients with cardiovascular (CV) disease and the general population. The use of these prognostic markers in an older population is not established yet. The aim of the present study was to investigate the prognostic value of age, sex, BMI, co-medication and CV laboratory risk markers in geriatric care patients.

MATERIALS AND METHODS

In this prospective observational single-centre cohort study data of long-term geriatric care patients were collected. Blood samples were collected between 14.09.2009 and 16.12.2009, and mortality was recorded up to 90 months. ADMA, its symmetric isomer SDMA, L-arginine, NT pro-BNP and CRP were determined at study entry. Simple associations of risk factors for survival period were explored by Spearman correlation coefficient. Significant univariate predictors for survival period were used in the Cox proportional hazard model.

RESULTS

A total of 481 patients were screened, and data from 449 patients were analysed. A total of 381 patients died during the observation period. Full data sets from 344 patients were used for Cox regression analysis. Male sex, older age, lower BMI, use of neuroleptic medicine, peripheral artery disease, and elevated plasma concentrations of ADMA, NT pro-BNP, and CRP were significant predictors of mortality.

CONCLUSION

The concentration of ADMA and NT pro-BNP may be used as an early risk marker for overall mortality in geriatric care. Neuroleptic medicine is associated with increased mortality in this population.

Modulating DDAH/NOS Pathway to Discover Vasoprotective Insulin Sensitizers

Insulin resistance syndrome (IRS) is a configuration of cardiovascular risk factors involved in the development of metabolic disorders including type 2 diabetes mellitus. In addition to diet, age, socioeconomic, and environmental factors, genetic factors that impair insulin signaling are centrally involved in the development and exacerbation of IRS. Genetic and pharmacological studies have demonstrated that the nitric oxide (NO) synthase (NOS) genes are critically involved in the regulation of insulin-mediated glucose disposal. The generation of NO by the NOS enzymes is known to contribute to vascular homeostasis including insulin-mediated skeletal muscle vasodilation and insulin sensitivity. By contrast, excessive inhibition of NOS enzymes by exogenous or endogenous factors is associated with insulin resistance (IR). Asymmetric dimethylarginine (ADMA) is an endogenous molecule that competitively inhibits all the NOS enzymes and contributes to metabolic perturbations including IR. The concentration of ADMA in plasma and tissue is enzymatically regulated by dimethylarginine dimethylaminohydrolase (DDAH), a widely expressed enzyme in the cardiovascular system. In preclinical studies, overexpression of DDAH has been shown to reduce ADMA levels, improve vascular compliance, and increase insulin sensitivity. This review discusses the feasibility of the NOS/DDAH pathway as a novel target to develop vasoprotective insulin sensitizers.

Pioglitazone decreases asymmetric dimethylarginine levels in patients with impaired glucose tolerance or type 2 diabetes

BACKGROUND AND AIMS

Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, is a biomarker and mediator of cardiovascular disease in patients with impaired glucose tolerance (IGT) or diabetes mellitus (DM). Advanced glycation end products (AGEs) and their receptor (RAGE) axis is involved in ADMA generation as well. However, it remains unclear whether pioglitazone could decrease ADMA levels by reducing RAGE expression in humans.

DESIGN AND METHODS

Forty-eight IGT or type 2 DM (T2DM) patients were assigned to receive either pioglitazone (n=29) or glimepiride (n=19) and evaluated at baseline and 16 weeks of follow-up. We compared the effects of pioglitazone and glimepride on ADMA and soluble form of RAGE (sRAGE) levels and then studied whether the changes in serum ADMA level (ΔADMA) after treatment with pioglitazone were correlated with ΔsRAGE. We further examined which Δclinical variables were independently associated with ΔADMA.

RESULTS

After 16-week treatments, fasting plasma glucose and glycated hemoglobin (HbA1c) values were comparably reduced in both groups. Compared with glimepiride, pioglitazone treatment significantly decreased ADMA levels and improved insulin sensitivity, while it elevated high-density lipoprotein cholesterol (HDL-C) and sRAGE values and increased body weight and waist circumference. In multiple stepwise regression analysis, log-transformed Δfibronectin were a sole independent determinant of log-transformed ΔADMA (r=-0.551, R²=0.303).

CONCLUSIONS

This study demonstrated that pioglitazone decreased serum ADMA levels in a glucose-lowering independent manner. Elevation of fibronectin by pioglitazone may contribute to the reduction of serum levels of ADMA in IGT or T2DM subjects, thus playing a protective role against cardiovascular disease.

Metformin, but not rosiglitazone, attenuates the increasing plasma levels of a new cardiovascular marker, fibulin-1, in patients with type 2 diabetes

OBJECTIVE The extracellular matrix protein fibulin-1 is upregulated in the arterial wall in type 2 diabetes (T2D) and circulates in increased concentrations in diabetes. Metformin is an antidiabetic drug with beneficial cardiovascular disease effects in diabetes. We hypothesized that metformin would influence the increased level of plasma fibulin-1 in diabetes. RESEARCH DESIGN AND METHODS After a 4-week run-in period, 371 eligible patients with T2D were randomized to treatment groups in a factorial design including insulin alone (control), +metformin, +rosiglitazone, or +both metformin and rosiglitazone. Plasma fibulin-1 was analyzed at the beginning of the study and after 18 and 24 months. RESULTS Plasma fibulin-1 increased in all groups throughout the 2-year period; however, the increase was strongly attenuated among patients treated with metformin. A highly significant difference was observed when the mean change in plasma fibulin-1 was compared between metformin- and non-metformin-treated individuals both at 18 and 24 months of treatment, but rosiglitazone had no effect. Metformin and rosiglitazone alone reduced the HbA1c levels to comparable levels and in combination even further. CONCLUSIONS Metformin attenuates the increase in plasma fibulin-1 concentrations in T2D, independently of glycemic effects. Changes in fibulin-1 may reflect an important element in diabetic arteriopathy that can be influenced by metformin.

Soluble epoxide hydrolase inhibition and peroxisome proliferator activated receptor γ agonist improve vascular function and decrease renal injury in hypertensive obese rats

Cardiometabolic syndrome occurs with obesity and consists of pathophysiological factors that increase the risk for cardiovascular events. Soluble epoxide hydrolase inhibition (sEHi) is a novel therapeutic approach that exerts renal and cardiovascular protection. Although sEHi as a therapeutic approach is promising, it could be more effective for the treatment of cardiometabolic syndrome when combined with peroxisome proliferator activated receptor γ (PPARγ) agonists. We hypothesized that the PPARγ agonist, rosiglitazone in combination with a sEHi (tAUCB) will provide synergistic actions to decrease blood pressure, improve vascular function, decrease inflammation, and prevent renal damage in spontaneously hypertensive obese rats (SHROB). SHROB were treated with rosiglitazone, tAUCB or the combination of tAUCB and rosiglitazone for four-weeks and compared with spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats. Blood pressure increased in SHROB (164 ± 7 mmHg) and decreased 10 mmHg when treated with rosiglitazone, tAUCB, or tAUCB and rosiglitazone. Mesenteric artery dilation to the K(ATP) channel opener pinacidil was attenuated in SHROB (E(Max) = 77 ± 7%), compared with WKY (E(Max) = 115 ± 19) and SHR (E(Max) = 93 ± 12%). Vasodilation to pinacidil was improved by rosiglitazone (E(Max) = 92 ± 14%) but not tAUCB. Renal macrophage infiltration increased in SHROB and significantly decreased with rosiglitazone or tAUCB and rosiglitazone treatment. Albuminuria was increased in SHROB (90 ± 20 mg/d) and was significantly decreased by the combination of tAUCB and rosiglitazone (37 ± 9 mg/d). Glomerular injury in SHROB was also significantly decreased by tAUCB and rosiglitazone. These results indicate that even though sEHi or PPARγ agonist have benefits when used individually, the combination is more beneficial for the multidisease features in cardiometabolic syndrome.

PPAR-γ as a therapeutic target in cardiovascular disease: evidence and uncertainty

Peroxisome proliferator-activated receptor γ (PPAR-γ) is a key regulator of fatty acid metabolism, promoting its storage in adipose tissue and reducing circulating concentrations of free fatty acids. Activation of PPAR-γ has favorable effects on measures of adipocyte function, insulin sensitivity, lipoprotein metabolism, and vascular structure and function. Despite these effects, clinical trials of thiazolidinedione PPAR-γ activators have not provided conclusive evidence that they reduce cardiovascular morbidity and mortality. The apparent disparity between effects on laboratory measurements and clinical outcomes may be related to limitations of clinical trials, adverse effects of PPAR-γ activation, or off-target effects of thiazolidinedione agents. This review addresses these issues from a clinician's perspective and highlights several ongoing clinical trials that may help to clarify the therapeutic role of PPAR-γ activators in cardiovascular disease.

The link between metabolic abnormalities and endothelial dysfunction in type 2 diabetes: an update

Despite abundant clinical evidence linking metabolic abnormalities to diabetic vasculopathy, the molecular basis of individual susceptibility to diabetic vascular complications is still largely undetermined. Endothelial dysfunction in diabetes-associated vascular complications is considered an early stage of vasculopathy and has attracted considerable research interests. Type 2 diabetes is characterized by metabolic abnormalities, such as hyperglycemia, excess liberation of free fatty acids (FFA), insulin resistance and hyperinsulinemia. These abnormalities exert pathological impact on endothelial function by attenuating endothelium-mediated vasomotor function, enhancing endothelial apoptosis, stimulating endothelium activation/endothelium-monocyte adhesion, promoting an atherogenic response and suppressing barrier function. There are multiple signaling pathways contributing to the adverse effects of glucotoxicity on endothelial function. Insulin maintains the normal balance for release of several factors with vasoactive properties. Abnormal insulin signaling in the endothelium does not affect the whole-body glucose metabolism, but impairs endothelial response to insulin and accelerates atherosclerosis. Excessive level of FFA is implicated in the pathogenesis of insulin resistance. FFA induces endothelial oxidative stress, apoptosis and inflammatory response, and inhibits insulin signaling. Although hyperglycemia, insulin resistance, hyperinsulinemia and dyslipidemia independently contribute to endothelial dysfunction via various distinct mechanisms, the mutual interactions may synergistically accelerate their adverse effects. Oxidative stress and inflammation are predicted to be among the first alterations which may trigger other downstream mediators in diabetes associated with endothelial dysfunction. These mechanisms may provide insights into potential therapeutic targets that can delay or reverse diabetic vasculopathy.

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.

DHA-rich fish oil reverses the detrimental effects of saturated fatty acids on postprandial vascular reactivity

BACKGROUND

Experimental elevation of nonesterified fatty acids (NEFAs) impairs endothelial function, but the effect of NEFA composition is unknown.

OBJECTIVE

The objective was to test the effect of acute elevation of NEFAs enriched with either saturated fatty acids (SFAs) or SFAs with long-chain (LC) n-3 (omega-3) PUFAs on vascular function measured via flow-mediated dilatation (FMD), laser Doppler iontophoresis (LDI), and digital volume pulse (DVP).

DESIGN

In 59 subjects (30 men and 29 women), repeated oral fat feeding of either palm stearin (SFA) or palm stearin with DHA-rich fish oil (SFA + LC n-3 PUFA) was performed on 2 separate occasions with continuous heparin infusion to elevate NEFAs for a duration of 60 to 240 min. Vascular function was measured at baseline and at the end of NEFA elevation; venous blood was collected for measurement of lipids and circulating markers of endothelial function.

RESULTS

NEFA elevation during consumption of the SFA-rich drinks was associated with a marked impairment of FMD, whereas consumption of SFAs + LC n-3 PUFAs improved FMD response, with a mean (±SEM) difference of 2.06 ± 0.29% (P < 0.001). Positive correlations were found with percentage weight of LC n-3 PUFAs in circulating NEFAs and change in FMD response [Spearman's rho (r(s)) = 0.460, P < 0.001]. LDI measures increased during both treatments (P ≤ 0.026), and there was no change in DVP indexes.

CONCLUSIONS

The composition of NEFAs can acutely affect FMD. The beneficial effect of LC n-3 PUFAs on postprandial vascular function warrants further investigation but may be mediated by nitric oxide-independent mechanisms. This trial is registered at clinicaltrials.gov as NCT01351324.

The impacts of thiazolidinediones on circulating C-reactive protein levels in different diseases: a meta-analysis

OBJECTIVES

Thiazolidinediones (TZDs), including rosiglitazone and pioglitazone, are widely used as antidiabetic agents. Here we present an updated meta-analysis of the respective effects of rosiglitazone and pioglitazone on the levels of C-reactive protein (CRP), a biomarker and predictor of CAD risks.

METHODS AND RESULTS

PubMed and EMBASE were systematically searched using the terms "C-reactive protein" and "rosiglitazone" or "pioglitazone" or "thiazolidinedione". A total of 59 rosiglitazone studies and 36 pioglitazone studies were included for evaluation. These were classified as 2-group studies and 1-group studies according to their study design. Standard mean difference (SMD) of CRP and 95% CI were calculated to evaluate the effect of TZDs on CRP. The overall SMD for rosiglitazone treatment is -0.392 (95% CI, [-0.446, -0.338]) in 2-group studies and -0.424 (95% CI, [-0.501, -0.346]) in 1-group studies. The overall SMD for pioglitazone treatment is -0.577 (95% CI, [-0.732, -0.421]) in 2-group studies and -0.327 (95% CI, [-0.439, -0.216]) in 1-group studies. Moreover, TZDs were found to significantly reduce CRP levels in both diabetes mellitus (DM) and non-DM patients.

CONCLUSIONS

Our meta-analysis suggested that both rosiglitazone and pioglitazone significantly decrease serum CRP levels. TZDs presented their CRP-lowering effect in both DM and non-DM patients.

Rosiglitazone reverses endothelial dysfunction but not remodeling of femoral artery in Zucker diabetic fatty rats

OBJECTIVES

Endothelial dysfunction precedes atherogenesis and clinical complications in type 2 diabetes. The vascular dysfunction in Zucker diabetic fatty (ZDF) rats was evaluated at different ages along with the effect of treatment with rosiglitazone (Rosi) on endothelial function and mechanical remodeling.

METHODS

The Rosi treatment was given to ZDF rats for 3 weeks. The endothelium-dependent vasodilation and alpha-adrenoceptor-dependent vasoconstriction of femoral arteries were studied using an ex-vivo isovolumic myograph. The biomechanical passive property of the arteries was studied in Ca2+-free condition. The expressions of endothelial nitric oxide synthase (eNOS), alpha-adrenoceptor, matrix metalloproteinase 9 (MMP9), and elastase were evaluated.

RESULTS

Endothelium-dependent vasorelaxation of the femoral artery was blunted at low doses in ZDF rats at 11 weeks of age and attenuated at all doses in ZDF rats at 19 weeks of age. The expression of eNOS was consistent with the endothelium-dependent vasorelaxation. The alpha-adrenoceptor was activated and the mechanical elastic modulus was increased in ZDF rats at 19 weeks of age. The expressions of alpha-adrenoceptor, MMP9, and elastase were up regulated in ZDF rats at 19 weeks of age. Rosi treatment for 3 weeks restored endothelium-dependent vasorelaxation and the expression of eNOS and the adrenoceptor activation at the doses below 10-6 mole/L in ZDF rats at 19 weeks of age. Rosi treatment for 3 weeks did not, however, improve the mechanical properties of blood vessel, the expressions of alpha-adrenoceptor, MMP9, and elastase in ZDF rats.

CONCLUSION

The endothelial dysfunction and mechanical remodeling are observed as early as 19 weeks of age in ZDF rat. Rosi treatment for 3 weeks improves endothelial function but not mechanical properties.

Tie2-mediated loss of peroxisome proliferator-activated receptor-gamma in mice causes PDGF receptor-beta-dependent pulmonary arterial muscularization

Peroxisome proliferator-activated receptor (PPAR)-gamma is reduced in pulmonary arteries (PAs) of patients with PA hypertension (PAH), and we reported that deletion of PPARgamma in smooth muscle cells (SMCs) of transgenic mice results in PAH. However, the sequelae of loss of PPARgamma in PA endothelial cells (ECs) are unknown. Therefore, we bred Tie2-Cre mice with PPARgamma(flox/flox) mice to induce EC loss of PPARgamma (Tie2 PPARgamma(-/-)), and we assessed PAH by right ventricular systolic pressure (RVSP), RV hypertrophy (RVH), and muscularized distal PAs in room air (RA), after chronic hypoxia (CH), and after 4 wk of recovery in RA (Rec-RA). The Tie2 PPARgamma(-/-) mice developed spontaneous PAH in RA with increased RVSP, RVH, and muscularized PAs vs. wild type (WT); both genotypes exhibited a similar degree of PAH following chronic hypoxia, but Tie2 PPARgamma(-/-) mice had more residual PAH compared with WT mice after Rec-RA. The Tie2 PPARgamma(-/-) vs. WT mice in RA had increased platelet-derived growth factor receptor-beta (PDGF-Rbeta) expression and signaling, despite an elevation in the PPARgamma target apolipoprotein E, an inhibitor of PDGF signaling. Inhibition of PDGF-Rbeta signaling with imatinib, however, was sufficient to reverse the PAH observed in the Tie2 PPARgamma(-/-) mice. Thus the disruption of PPARgamma signaling in EC is sufficient to cause mild PAH and to impair recovery from CH-induced PAH. Inhibition of heightened PDGF-Rbeta signaling is sufficient to reverse PAH in this genetic model.

Effect of fenofibrate on microcirculation and wound healing in healthy and diabetic mice

Objective

Disturbances in wound healing in patients with hyperglycaemic blood sugar values are a common clinical problem. Recent studies identified PPARα-ligands as potential skin therapeutic agents. The aim of this study was to investigate the effects of oral fenofibrate treatment on dermal wound healing and micro-circulatory parameters in diabetic mice.

Methods

Dermal wounds were created in CD-1 mice. Mice were randomized into four treatment groups: diabetic mice treated (dbf) or not-treated with fenofibrate (dbnf). As controls served non-diabetic mice treated (ndf) or not-treated with fenofibrate (ndnf). At various points in time microcirculation was analyzed by intravital fluorescent microscopy to determine wound surface area, vessel diameter, plasma leakage, functional capillary density, and leukocyte/endothelium interaction.

Results

The dbf-mice showed a significantly increased diameter of the venules and the arterioles up to 3 days after wound creation compared to dbnf-mice. However, wound healing was not improved in dbf-compared to dbnf-mice. Surprisingly, all microcirculatory parameter (vessel diameter, plasma leakage and functional capillary density) were not deteriorated in dbnf-compared to ndnf-mice.

Conclusion

We confirm that high blood sugar values lead to a delayed wound healing, but this could not traced back to altered microcirculatory patterns. Furthermore, in dbf-mice an improved vasodilatatory function of small vessels could be detected, but with no substantial effect on wound healing. Further studies are needed to clarify, if topical application of fenofibrate might be beneficial.

Therapeutic interventions and oxidative stress in diabetes

Many therapeutic agents that are used in patients with diabetes mitigate oxidative stress. These agents are of particular interest because oxidative stress is elevated in diabetes and is thought to contribute to vascular dysfunction. Agents that merely quench already formed reactive oxygen species have demonstrated limited success in improving cardiovascular outcomes. Thus, although vitamin E, C, and alpha lipoic acid appeared promising in animal models and initial human studies, subsequent larger trials have failed to demonstrate improvement in cardiovascular outcomes. Drugs that limit the production of oxidative stress are more successful in improving vascular outcomes in patients with diabetes. Thus, although statins, ACE inhibitors, ARBs and thiazolinediones are used for varied clinical purposes, their increased efficacy in improving cardiovascular outcomes is likely related to their success in reducing the production of reactive oxygen species at an earlier part of the cascade, thereby more effectively decreasing the oxidative stress burden. In particular, statins and ACE inhibitors/ ARBs appear the most successful at reducing oxidative stress and vascular disease and have potential for synergistic effects.

An integrated view of insulin resistance and endothelial dysfunction

Endothelial dysfunction and insulin resistance are frequently comorbid states. Vasodilator actions of insulin are mediated by phosphatidylinositol 3-kinase (PI3K)-dependent signaling pathways that stimulate production of nitric oxide from vascular endothelium. This helps to couple metabolic and hemodynamic homeostasis under healthy conditions. In pathologic states, shared causal factors, including glucotoxicity, lipotoxicity, and inflammation selectively impair PI3K-dependent insulin signaling pathways that contribute to reciprocal relationships between insulin resistance and endothelial dysfunction. This article discusses the implications of pathway-selective insulin resistance in vascular endothelium, interactions between endothelial dysfunction and insulin resistance, and therapeutic interventions that may simultaneously improve both metabolic and cardiovascular physiology in insulin-resistant conditions.

Intensification of oxidative stress and inflammation in type 2 diabetes despite antihyperglycemic treatment

INTRODUCTION

The metabolic deregulation associated with diabetes mellitus (DM) causes secondary pathophysiologic changes in multiple organ systems. Endothelial injury is induced by oxidative stress (OS) and inflammation. We have previously shown that DM type 2 patients are exposed to increased OS and inflammation contributed in part by primed peripheral polymorphonuclear leukocytes (PMNLs).

AIMS

To characterize the effect of oral medication on PMNL priming, on PMNL-related and on systemic inflammation, in correlation to changed diabetes parameters in patient with newly diagnosed type 2 DM.

METHODS

PMNLs were separated from DM patient's prior and following treatment with either metformin (Glucophage), or Thiazolidinedione (rosiglitazone) and from healthy control subjects (HC). Rate of superoxide release from phorbol ester-stimulated PMNLs and CD11b on PMNLs assessed PMNL priming. White blood cells (WBC) and PMNL counts and apoptosis reflected PMNL-related inflammation. CRP, fibrinogen, transferrin and albumin blood levels reflected systemic inflammation.

RESULTS

Both metformin and rosiglitazone treatments reduced significantly the high levels of glucose and HbA1c, and slightly improved lipid profile during 2 months. PMNL priming parameters, higher compared to HC, increased after 2 months of metformin treatment. Rosiglitazone treatment decreased PMNL priming. ALP, higher in DM, significantly decreased following 2 months of both treatments. Systemic inflammation markers (fibrinogen, CRP), higher in DM, decreased following both treatments. Transferrin and albumin were similar to HC. PMNL-related inflammation markers were higher in DM; however, only PMNL apoptosis decreased after both treatments. Monocyte counts, higher in DM compared to HC, decreased following both treatments. Serum insulin levels, higher in DM compared to HC, decreased following both treatments. PMNL-related priming and inflammation parameters positively correlated with HbA1c.

CONCLUSION

The present research adds new facet in evaluating anti-hyperglycemic treatment in type 2 DM patients. Despite sufficient glycemic control using both treatments, some PMNL-related parameters deteriorated. Thus, anti hyperglycemic treatment should be favored due to its combined anti-PMNL priming and anti-inflammatory effect, in addition to its anti-hyperglycemic characteristics, according to the correlation among these parameters. Such combined treatment may reduce morbidity and mortality common in DM patients.

Dichotomous effects of rosiglitazone in transplantation-induced systemic vasodilator dysfunction in rats

BACKGROUND

Transplantation-induced systemic endothelial dysfunction causes severe cardiovascular morbidity and mortality after transplantation. Interventions that improve systemic endothelial function after transplantation and furthermore reduce intragraft vascular dysfunction might improve graft and patient survival. Treatment with the PPARgamma agonist rosiglitazone is an intervention that potentially fulfills these criteria. In this study, we determined the effect of rosiglitazone treatment on transplantation-induced endothelial dysfunction and vasomotor activity in an experimental model for chronic transplant dysfunction in rats.

METHODS

Lewis abdominal aortic allografts were orthotopically transplanted into Brown Norway recipients that received either regular chow or chow containing rosiglitazone (approximately 4.2 mg/day). Endothelium-dependent (response to metacholine) and total (response to sodium nitrite) vasodilatory responses were determined in autologous thoracic aortic rings using an ex vivo organ bath setup. Measurements were performed 8 weeks after transplantation.

RESULTS

Aortic allografting induced systemic endothelial dysfunction as measured by reduced endothelium-dependent vasodilation in the recipient's vascular system. Rosiglitazone treatment restored endothelium-dependent vasodilatory responses to pretransplantation levels. However, rosiglitazone treatment reduced the total dilatory response despite normalized endothelial function, indicating impairment of vascular smooth muscle cell vasomotor activity.

CONCLUSIONS

Rosiglitazone treatment after allogeneic transplantation restores endothelial function but impairs vascular smooth muscle cell vasomotor activity. This dichotomous effect of rosiglitazone might impede use of rosiglitazone after organ transplantation since this potentially increases cardiovascular risk despite improved endothelial cell function.