Enhancement of insulin sensitivity by troglitazone lowers blood pressure in diabetic hypertensives

PPARγ Agonist Rosiglitazone and Antagonist GW9662: Antihypertensive Effects on Chronic Intermittent Hypoxia-Induced Hypertension in Rats

The increased incidence of hypertension associated with obstructive sleep apnea (OSA) presents significant physical, psychological, and economic challenges. Peroxisome proliferator-activated receptor gamma (PPARγ) plays a role in both OSA and hypertension, yet the therapeutic potential of PPARγ agonists and antagonists for OSA-related hypertension remains unexplored. Therefore, we constructed a chronic intermittent hypoxia (CIH)-induced hypertension rat model that mimics the pathogenesis of OSA-related hypertension in humans. The model involved administering PPARγ agonist rosiglitazone (RSG), PPARγ antagonist GW9662, or normal saline, followed by regular monitoring of blood pressure and thoracic aorta analysis using staining and electron microscopy. Intriguingly, our results indicated that both RSG and GW9662 appeared to potently counteract CIH-induced hypertension. In silico study suggested that GW9662's antihypertensive effect might mediated through angiotensin II receptor type 1 (AGTR1). Our findings provide insights into the mechanisms of OSA-related hypertension and propose novel therapeutic targets.

The 2023 Walter B. Cannon Award Lecture: Mechanisms Regulating Vascular Function and Blood Pressure by the PPARγ-RhoBTB1-CUL3 Pathway

Human genetic and clinical trial data suggest that peroxisome proliferator activated receptor γ (PPARγ), a nuclear receptor transcription factor plays an important role in the regulation of arterial blood pressure. The examination of a series of novel animal models, coupled with transcriptomic and proteomic analysis, has revealed that PPARγ and its target genes employ diverse pathways to regulate vascular function and blood pressure. In endothelium, PPARγ target genes promote an antioxidant state, stimulating both nitric oxide (NO) synthesis and bioavailability, essential components of endothelial-smooth muscle communication. In vascular smooth muscle, PPARγ induces the expression of a number of genes that promote an antiinflammatory state and tightly control the level of cGMP, thus promoting responsiveness to endothelial-derived NO. One of the PPARγ targets in smooth muscle, Rho related BTB domain containing 1 (RhoBTB1) acts as a substrate adaptor for proteins to be ubiquitinated by the E3 ubiquitin ligase Cullin-3 and targeted for proteasomal degradation. One of these proteins, phosphodiesterase 5 (PDE5) is a target of the Cullin-3/RhoBTB1 pathway. Phosphodiesterase 5 degrades cGMP to GMP and thus regulates the smooth muscle response to NO. Moreover, expression of RhoBTB1 under condition of RhoBTB1 deficiency reverses established arterial stiffness. In conclusion, the coordinated action of PPARγ in endothelium and smooth muscle is needed to maintain NO bioavailability and activity, is an essential regulator of vasodilator/vasoconstrictor balance, and regulates blood vessel structure and stiffness.

The Role of Peroxisome Proliferator-Activated Receptors in Preeclampsia

Preeclampsia is a common pregnancy-related hypertensive disorder. Often presenting as preexisting or new-onset hypertension complicated by proteinuria and/or end-organ dysfunction, preeclampsia significantly correlates with maternal and perinatal morbidity and mortality. Peroxisome proliferator-activated receptors (PPARs) are nuclear receptor proteins that regulate gene expression. In order to investigate the role of PPARs in the pathophysiology of preeclampsia, we conducted a literature review using the MEDLINE and LIVIVO databases. The search terms "peroxisome proliferator-activated receptor", "PPAR", and "preeclampsia" were employed and we were able to identify 35 relevant studies published between 2002 and 2022. Different study groups reached contradictory conclusions in terms of PPAR expression in preeclamptic placentae. Interestingly, PPARγ agonists alone, or in combination with well-established pharmaceutical agents, were determined to represent novel, potent anti-preeclamptic treatment alternatives. In conclusion, PPARs seem to play a significant role in preeclampsia.

Role of the Peroxisome Proliferator Activated Receptors in Hypertension

Nuclear receptors represent a large family of ligand-activated transcription factors which sense the physiological environment and make long-term adaptations by mediating changes in gene expression. In this review, we will first discuss the fundamental mechanisms by which nuclear receptors mediate their transcriptional responses. We will focus on the PPAR (peroxisome proliferator-activated receptor) family of adopted orphan receptors paying special attention to PPARγ, the isoform with the most compelling evidence as an important regulator of arterial blood pressure. We will review genetic data showing that rare mutations in PPARγ cause severe hypertension and clinical trial data which show that PPARγ activators have beneficial effects on blood pressure. We will detail the tissue- and cell-specific molecular mechanisms by which PPARs in the brain, kidney, vasculature, and immune system modulate blood pressure and related phenotypes, such as endothelial function. Finally, we will discuss the role of placental PPARs in preeclampsia, a life threatening form of hypertension during pregnancy. We will close with a viewpoint on future research directions and implications for developing novel therapies.

[Role of PPARγ, a transcription factor in cardiovascular disease]

Peroxisome proliferator-activated receptor γ (PPARγ) is a ligand activated transcription factor known to regulate fatty acid metabolism. Thiazolidinediones (TZDs), PPARγ synthetic agonists, currently used to treat patients with type 2 diabetes, have been shown to lower the blood pressure and protect against vascular diseases such as atherosclerosis. In line with these findings, it has been reported that individuals with loss-of-function mutations of PPARγ developed sever early-onset hypertension in addition to metabolic abnormalities. Accumulating evidences suggest PPARγ in the vasculature has protective effects on cardiovascular disease despite unclear mechanism. Because of ubiquitous expression of PPARγ, TZDs are well-known to be associated with serious side effects such as weight gain, fluid retention, and bone fractures. Thus identification of mechanisms on tissue-specific PPARγ activity may lead to the development of targeted treatment which is characterized by no deleterious effects. This review discusses role of PPARγ in cardiovascular disease.

Chronic neuromuscular electrical stimulation improves muscle mass and insulin sensitivity in a mouse model

Muscle wasting reduces functional capacity and increases cardiometabolic risk in chronic disease. Neuromuscular electrical stimulation (NMES) of the lower limb has been shown to reverse muscle wasting in these patients but its effect on cardiometabolic health is unclear. We investigated a mouse model of in-vivo non-invasive chronic NMES on muscle mass, insulin sensitivity and arterial blood pressure (BP). Twenty-three C57BL6 mice underwent unilateral NMES or sham training over 2.5 weeks while anesthetized by isoflurane. Lower limb muscle mass and the stimulated limb to non-stimulated limb muscle mass ratio were compared between groups (NMES vs. sham). Insulin sensitivity was assessed 48 h after training using an intraperitoneal insulin tolerance test (ITT) and BP was assessed before and after training using the tail-cuff technique. After training, muscle mass increased in NMES vs. sham (416 ± 6 vs. 397 ± 6 mg, p = 0.04) along with the ratio of muscle mass (+3 ± 1% vs. −1 ± 1% p = 0.04). Moreover, insulin sensitivity improved in NMES vs. sham (average blood glucose during ITT: 139.6 ± 8.5 vs. 161.9 ± 9.0 mg/dl blood, p = 0.01). BP was decreased in both groups, although it is likely that the effect of NMES on BP was dampened by repetitive anesthesia. The metabolic benefit of NMES training could be of great utility in patients with chronic disease. Moreover, the clinical-like mouse model of NMES is an effective tool to investigate the systemic effects of local muscle strengthening.

DPP-4 Inhibitors as Potential Candidates for Antihypertensive Therapy: Improving Vascular Inflammation and Assisting the Action of Traditional Antihypertensive Drugs

Dipeptidyl peptidase-4 (DPP-4) is an important protease that is widely expressed on the surface of human cells and plays a key role in immune-regulation, inflammation, oxidative stress, cell adhesion, and apoptosis by targeting different substrates. DPP-4 inhibitors (DPP-4i) are commonly used as hypoglycemic agents. However, in addition to their hypoglycemic effect, DPP-4i have also shown potent activities in the cardiovascular system, particularly in the regulation of blood pressure (BP). Previous studies have shown that the regulatory actions of DPP-4i in controlling BP are complex and that the mechanisms involved include the functional activities of the nerves, kidneys, hormones, blood vessels, and insulin. Recent work has also shown that inflammation is closely associated with the elevation of BP, and that the inhibition of DPP-4 can reduce BP by regulating the function of the immune system, by reducing inflammatory reactions and by improving oxidative stress. In this review, we describe the potential anti-hypertensive effects of DPP-4i and discuss potential new anti-hypertensive therapies. Our analysis indicated that DPP-4i treatment has a mild anti-hypertensive effect as a monotherapy and causes a significant reduction in BP when used in combined treatments. However, the combination of DPP-4i with high-dose angiotensin converting enzyme inhibitors (ACEI) can lead to increased BP. We suggest that DPP-4i improves vascular endothelial function in hypertensive patients by suppressing inflammatory responses and by alleviating oxidative stress. In addition, DPP-4i can also regulate BP by activating the sympathetic nervous system, interfering with the renin angiotensin aldosterone system (RAAS), regulating Na/H2O metabolism, and attenuating insulin resistance (IR).

RhoBTB1 protects against hypertension and arterial stiffness by restraining phosphodiesterase 5 activity

Mice selectively expressing PPARγ dominant negative mutation in vascular smooth muscle exhibit RhoBTB1-deficiency and hypertension. Our rationale was to employ genetic complementation to uncover the mechanism of action of RhoBTB1 in vascular smooth muscle. Inducible smooth muscle-specific restoration of RhoBTB1 fully corrected the hypertension and arterial stiffness by improving vasodilator function. Notably, the cardiovascular protection occurred despite preservation of increased agonist-mediated contraction and RhoA/Rho kinase activity, suggesting RhoBTB1 selectively controls vasodilation. RhoBTB1 augmented the cGMP response to nitric oxide by restraining the activity of phosphodiesterase 5 (PDE5) by acting as a substrate adaptor delivering PDE5 to the Cullin-3 E3 Ring ubiquitin ligase complex for ubiquitination inhibiting PDE5. Angiotensin-II infusion also caused RhoBTB1-deficiency and hypertension which was prevented by smooth muscle specific RhoBTB1 restoration. We conclude that RhoBTB1 protected from hypertension, vascular smooth muscle dysfunction, and arterial stiffness in at least two models of hypertension.

Endothelial Cell-Targeted Deletion of PPARγ Blocks Rosiglitazone-Induced Plasma Volume Expansion and Vascular Remodeling in Adipose Tissue

Thiazolidinediones (TZDs) are peroxisome proliferator-activated receptor γ (PPARγ) agonists that represent an effective class of insulin-sensitizing agents; however, clinical use is associated with weight gain and peripheral edema. To elucidate the role of PPARγ expression in endothelial cells (ECs) in these side effects, EC-targeted PPARγ knockout (Pparg ΔEC) mice were placed on a high-fat diet to promote PPARγ agonist-induced plasma volume expansion, and then treated with the TZD rosiglitazone. Compared with Pparg-floxed wild-type control (Pparg f/f) mice, Pparg ΔEC treated with rosiglitazone are resistant to an increase in extracellular fluid, water content in epididymal and inguinal white adipose tissue, and plasma volume expansion. Interestingly, histologic assessment confirmed significant rosiglitazone-mediated capillary dilation within white adipose tissue of Pparg f/f mice, but not Pparg ΔEC mice. Analysis of ECs isolated from untreated mice in both strains suggested the involvement of changes in endothelial junction formation. Specifically, compared with cells from Pparg f/f mice, Pparg ΔEC cells had a 15-fold increase in focal adhesion kinase, critically important in EC focal adhesions, and >3-fold significant increase in vascular endothelial cadherin, the main component of focal adhesions. Together, these results indicate that rosiglitazone has direct effects on the endothelium via PPARγ activation and point toward a critical role for PPARγ in ECs during rosiglitazone-mediated plasma volume expansion.

Effects of Low-Molecular-Weight Fucoidan and High Stability Fucoxanthin on Glucose Homeostasis, Lipid Metabolism, and Liver Function in a Mouse Model of Type II Diabetes

The combined effects of low-molecular-weight fucoidan (LMF) and fucoxanthin (Fx) in terms of antihyperglycemic, antihyperlipidemic, and hepatoprotective activities were investigated in a mouse model of type II diabetes. The intake of LMF, Fx, and LMF + Fx lowered the blood sugar and fasting blood sugar levels, and increased serum adiponectin levels. The significant decrease in urinary sugar was only observed in LMF + Fx supplementation. LMF and Fx had ameliorating effects on the hepatic tissue of db/db mice by increasing hepatic glycogen and antioxidative enzymes, and LMF was more effective than Fx at improving hepatic glucose metabolism. As for glucose and lipid metabolism in the adipose tissue, the expression of insulin receptor substrate (IRS)-1, glucose transporter (GLUT), peroxisome proliferator-activated receptor gamma (PPARγ), and uncoupling protein (UCP)-1 mRNAs in the adipose tissue of diabetic mice was significantly upregulated by Fx and LMF + Fx, and levels of inflammatory adipocytokines, such as adiponectin, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6), were significantly modulated only by LMF + Fx supplementation. The efficacy of LMF + Fx supplementation on the decrease in urinary sugar and on glucose and lipid metabolism in the white adipose tissue of db/db mice was better than that of Fx or LMF alone, indicating the occurrence of a synergistic effect of LMF and Fx.

PPARγ Regulation in Hypertension and Metabolic Syndrome

Dysregulation of peroxisome proliferator-activated receptor gamma (PPARγ) activity leads to significant alterations in cardiovascular and metabolic regulation. This is most keenly observed by the metabolic syndrome-like phenotypes exhibited by patients carrying mutations in PPARγ. We will summarize recent findings regarding mechanisms of PPARγ regulation in the cardiovascular and nervous systems focusing largely on PPARγ in the smooth muscle, endothelium, and brain. Canonically, PPARγ exerts its effects by regulating the expression of target genes in these cells, and we will discuss mechanisms by which PPARγ targets in the vasculature regulate cardiovascular function. We will also discuss emerging evidence that PPARγ in the brain is a mediator of appetite and obesity. Finally, we will briefly review how novel PPARγ activators control posttranslational modifications of PPARγ and their prospects to offer new therapeutic options for treatment of metabolic diseases without the adverse side effects of thiazolidinediones which strongly activate transcriptional activity of PPARγ.

Safety and effectiveness of a fixed-dose combination of olmesartan, amlodipine, and hydrochlorothiazide in clinical practice

Background

Clinical trials indicate that the use of fixed-dose combinations (FDCs) is associated with a higher level of treatment adherence and prolonged blood pressure (BP) control. The aim of this study was to document the safety and effectiveness of the FDC olmesartan/amlodipine/hydrochlorothiazide in patients with essential hypertension in clinical practice.

Methods

This multicenter, prospective, 24-week, noninterventional study enrolled 5,831 patients from primary care offices in Germany and Austria. Inclusion criteria were a diagnosis of essential hypertension and newly initiated treatment with the FDC.

Results

The mean age of patients was 63.5 years, almost 50% of patients had a time since diagnosis of essential hypertension of over 5 years, and approximately 70% of patients had at least one cardiovascular risk factor, including 29.4% of patients with diabetes mellitus. Following approximately 24 weeks of treatment, the mean reduction in systolic/diastolic BP was 29.0/14.0 mmHg, a BP response was observed by 94.2% of patients, and a target BP of <140/90 mmHg was attained in 67.5% of patients. At least one adverse drug reaction (ADR) was experienced by 1.2% of patients, with the most common being peripheral edema. Subanalyses demonstrated that the following factors did not have a significant influence on the ADR rate: age (<65 years versus ≥65 years), diabetes mellitus (no/yes), cardiovascular risk (low/high), and concomitant medication (no/yes).

Conclusion

This study demonstrates that in clinical practice, treatment with the three-drug combination as an FDC tablet resulted in a very high proportion of patients with a BP response and control, accompanied by a very low rate of ADRs.

Natural product agonists of peroxisome proliferator-activated receptor gamma (PPARγ): a review

Agonists of the nuclear receptor PPARγ are therapeutically used to combat hyperglycaemia associated with the metabolic syndrome and type 2 diabetes. In spite of being effective in normalization of blood glucose levels, the currently used PPARγ agonists from the thiazolidinedione type have serious side effects, making the discovery of novel ligands highly relevant. Natural products have proven historically to be a promising pool of structures for drug discovery, and a significant research effort has recently been undertaken to explore the PPARγ-activating potential of a wide range of natural products originating from traditionally used medicinal plants or dietary sources. The majority of identified compounds are selective PPARγ modulators (SPPARMs), transactivating the expression of PPARγ-dependent reporter genes as partial agonists. Those natural PPARγ ligands have different binding modes to the receptor in comparison to the full thiazolidinedione agonists, and on some occasions activate in addition PPARα (e.g. genistein, biochanin A, sargaquinoic acid, sargahydroquinoic acid, resveratrol, amorphastilbol) or the PPARγ-dimer partner retinoid X receptor (RXR; e.g. the neolignans magnolol and honokiol). A number of in vivo studies suggest that some of the natural product activators of PPARγ (e.g. honokiol, amorfrutin 1, amorfrutin B, amorphastilbol) improve metabolic parameters in diabetic animal models, partly with reduced side effects in comparison to full thiazolidinedione agonists. The bioactivity pattern as well as the dietary use of several of the identified active compounds and plant extracts warrants future research regarding their therapeutic potential and the possibility to modulate PPARγ activation by dietary interventions or food supplements.

Impact of hyperinsulinemia on the development of hypertension in normotensive, nondiabetic adults: a 4-year follow-up study

BACKGROUND AND AIMS

This study aimed to investigate the association between baseline fasting insulin levels, changes in fasting insulin levels, and future development of hypertension in normotensive, non-diabetic, healthy adults.

METHODS

We analyzed data from 11,123 adults, aged 20-65years, who had no history of hypertension or diabetes mellitus at a 2004 medical examination in a health promotion program and had attended a repeat examination in 2008. Subjects were divided into four groups according to baseline quartiles of fasting insulin and dichotomized fasting insulin levels at baseline and after 4years: low-low, low-high, high-low, high-high. We also assessed whether the association differed between the younger (20-40years) and older subjects (41-65years).

RESULTS

In four years, 1142 subjects (10.3%) developed hypertension. The odds ratio (OR) for the development for hypertension increased as the quartiles of baseline fasting insulin levels and changes in fasting insulin levels increased from the first to the fourth quartile (OR 1.15, 1.35, and 1.95 vs. 1.07, 1.22, and 1.41, respectively), after adjusting for multiple factors. The OR for hypertension was 2.0-fold higher in the high-high group and 1.34-fold higher in the low-high group than in the low-low group. In comparing the results by age group, we found that these relationships were more prominent in younger subjects.

CONCLUSION

High baseline and continuously increasing fasting insulin levels appeared to be independent determinants for the future development of hypertension during this 4-year follow-up study in normotensive, non-diabetic, healthy adults.

Hypertension in metabolic syndrome: vascular pathophysiology

METABOLIC SYNDROME IS A CLUSTER OF METABOLIC AND CARDIOVASCULAR SYMPTOMS: insulin resistance (IR), obesity, dyslipemia. Hypertension and vascular disorders are central to this syndrome. After a brief historical review, we discuss the role of sympathetic tone. Subsequently, we examine the link between endothelial dysfunction and IR. NO is involved in the insulin-elicited capillary vasodilatation. The insulin-signaling pathways causing NO release are different to the classical. There is a vasodilatory pathway with activation of NO synthase through Akt, and a vasoconstrictor pathway that involves the release of endothelin-1 via MAPK. IR is associated with an imbalance between both pathways in favour of the vasoconstrictor one. We also consider the link between hypertension and IR: the insulin hypothesis of hypertension. Next we discuss the importance of perivascular adipose tissue and the role of adipokines that possess vasoactive properties. Finally, animal models used in the study of vascular function of metabolic syndrome are reviewed. In particular, the Zucker fatty rat and the spontaneously hypertensive obese rat (SHROB). This one suffers macro- and microvascular malfunction due to a failure in the NO system and an abnormally high release of vasoconstrictor prostaglandins, all this alleviated with glitazones used for metabolic syndrome therapy.

The metabolic syndrome and inflammation

The metabolic syndrome (MS) is a clustering of cardiovascular risk factors, with insulin resistance as a major feature. This syndrome has been variously defined, but generally consists of 3 or more of the following components: hyperglycemia, hypertension, hypertriglyceridemia, low HDL, and increased abdominal circumference and/or BMI at >30 kg/m(2). The WHO criteria require the presence of insulin resistance to make the diagnosis. The current review focuses particularly on the association of the MS and the proinflammatory state as well as treatment options to prevent the development of coronary heart disease (CHD). Chronic inflammation is frequently associated with the MS. Inflammatory markers that have been associated with MS include hs-CRP, TNF-alpha, fibrinogen, and IL-6, among others. The link between inflammation and the MS is not fully understood. One postulated mechanism is that these cytokines are released into the circulation by adipose tissue, stimulating hepatic CRP production. The prothrombotic molecule PAI-1 is also increased in the MS. Adiponectin, produced exclusively by adipocytes, is decreased in obesity. The association of these proinflammatory and prothrombotic markers with the MS is discussed in detail. The general goals of treatment of the MS are prevention of CHD events and diabetes if not already present. The approach to treatment of those with the MS should include lifestyle changes, including weight loss and exercise as well as appropriate pharmacological therapies. Certain medications, which may be used in persons with MS, have been shown to have beneficial effects on clinical outcome and/or anti-inflammatory effects.

Effects of fenofibrate, a PPAR-α ligand, on the haemodynamics of glycerol-induced renal failure in rats

The modulating effect of peroxisome proliferator-activated receptor α ligand on haemodynamic effects of phenylepherine (PE), angiotensin II (AII), endothelin 1 (ET1), acetylcholine (Ach), sodium nitroprusside (SNP) and isoproterenol (ISO) were evaluated in glycerol-induced acute kidney injury in rats. The effect of PE on fenofibrate-treated animals was a dose-dependent increase in mean arterial blood pressure (MAP). For AII and ET1, MAP was also increased for the fenofibrate group but not in a dose-dependent fashion. On the medullary blood flow (MBF), while the lower doses of PE and AII increased the perfusion unit on the fenofibrate-treated group, the higher doses decreased the perfusion unit. The ET1 increased the perfusion unit on this group but not in dose-dependent fashion. The effects of PE and AII on the cortical blood flow (CBF) of fenofibrate-treated group is similar to that of MBF for the same group but not for ET1. The effect of Ach, SNP and ISO in all the groups was the decrease in MAP. ISO caused dose-dependent increase in MBF of fenofibrate-treated group. The effect of Ach, SNP and ISO on the CBF perfusion unit was that of the increase for the fenofibrate-treated group. The study showed that fenofibrate did not attenuate increased blood pressure induced by PE, AII and ET1 but caused enhanced vasodilation by Ach, SNP and ISO.

Peroxisome proliferator-activated receptor-γ and the endothelium: implications in cardiovascular disease

Peroxisome proliferator-activated receptors-γ (PPARγs) are ligand-activated transcription factors that play a crucial regulatory role in the transcription of a large number of genes involved in lipid metabolism and inflammation. In addition to physiological ligands, synthetic ligands (the thiazoledinediones) have been developed. In spite of the much publicized adverse cardiovascular effects of one such thiazoledinedione (rosiglitazone), PPARγ activation may have beneficial cardiovascular effects. In this article we review the effects of PPARγ activation on the endothelium with special emphasis on the possible implications in cardiovascular disease. We discuss its possible role in inflammation, vasomotor function, thrombosis, angiogenesis, vascular aging and vascular rhythm. We also briefly review the clinical implications of these lines of research.

Rosiglitazone reverses increased duodenal inhibitory response in spontaneously hypertensive rats

BACKGROUND

Thiazolidinediones (TZDs) including rosiglitazone (ROSI) are insulin sensitizing agents with beneficial gastrointestinal effects. However, no studies are available on TZDs effect in gastrointestinal motility. We evaluated the effects of ROSI on gastrointestinal inhibitory neurotransmission focusing on the modulatory roles of nitric oxide synthase/nitric oxide (NOS/NO) and heme oxygenase/carbon monoxide (HO/CO) pathways.

METHODS

Spontaneously hypertensive rats (SHR) were used as model of insulin resistance. Duodenal strips were obtained from vehicle-treated SHR, ROSI-treated SHR (5 mg kg(-1) by gavage daily per 6 weeks), and Wistar Kyoto (WKY). Inhibitory responses to electrical field stimulation (EFS) were evaluated in the presence of HO inhibitor zinc protoporphyrin IX (ZnPPIX, 10 μmol L(-1)) or NOS inhibitor N(G)-nitro-L-arginine (L-NNA, 100 μmol L(-1)), alone and in combination. Protein levels of HO and NOS isoforms were evaluated by immunohistochemistry and western blot analysis.

KEY RESULTS

Basal responses to EFS were significantly increased in duodenum strips from vehicle-treated SHR vs WKY. This effect was reversed in ROSI-treated SHR. The EFS-mediated relaxation was comparably reduced by ZnPPIX in WKY and SHR, but not in ROSI-treated SHR animals. The L-NNA reduced EFS response to a similar extent in WKY and ROSI -treated SHR, but its effect was significantly higher in vehicle-treated SHR. Expression of HO-1 protein was significantly lower, whereas HO-2 protein levels were unchanged in ROSI-treated SHR with respect to vehicle-treated SHR. Finally, increased levels of nNOS in vehicle-treated SHR were reduced in ROSI-treated SHR.

CONCLUSIONS & INFERENCES

Chronic ROSI treatment reverses increased SHR duodenal inhibitory response acting on CO and NO components.

Angiotensin II receptor activation in youth triggers persistent insulin resistance and hypertension--a legacy effect?

Although the involvement of angiotensin II (Ang II) in insulin resistance and hypertension has been established, the temporal relationships between Ang II receptor activation and changes in insulin sensitivity and blood pressure are not clear. To better understand this issue, we infused rats with Ang II (200 ng kg(-1) min(-1)) or vehicle for 4 weeks and assessed the residual effects after the discontinuation of the infusion on blood pressure, insulin sensitivity and tissue parameters of inflammation. Four weeks after the discontinuation of the Ang II infusion, the blood pressure was higher by 12.8 mm Hg, and insulin sensitivity as determined by a euglycemic hyperinsulinemic glucose clamp was reduced (glucose infusion rate: 11.1±0.7 vs. 17.6±0.5 mg kg(-1) min(-1)) in the Ang II-treated group compared with controls. The persistent hypertension and insulin resistance were associated with greater than two-fold increases in macrophage chemoattractant protein-1, tumor necrosis factor-α and thiobarbituric acid-reactive substrates in the soleus muscle. Furthermore, total and activated forms of Rac-1, a regulatory subunit of the NADPH oxidase complex, were increased by 144±14% and 277±82%, respectively, in the skeletal muscle of Ang II-treated rats. These residual effects after Ang II infusion were all attenuated by the co-administration of tempol, a free radical scavenger, or candesartan with Ang II. The effects of candesartan were not mimicked by hydralazine at an equidepressant dose. These findings suggest that Ang II receptor activation in youth triggers the upregulation of inflammatory cytokines and the production of reactive oxygen species, thereby inducing later insulin resistance and hypertension.

Cardiovascular risk factors related to the PPARγ Pro12Ala polymorphism in patients with type 2 diabetes are gender dependent

The interaction of the PPARγ Pro12Ala polymorphism with diabetes and cardiovascular risk is controversial. We studied 173 women and 309 men in the observational CARDIPP trial in which determination of left ventricular mass, carotid intima-media thickness (IMT) and pulse wave velocity (PWV) were performed. Blood pressures were measured with 24-h ambulatory technique (ABP). Heterozygotes and homozygotes of Ala were defined as Ala in the analyses. Men with Ala-isoform displayed higher waist circumference (Ala: 107 ± 14 cm, Pro: 104 ± 11 cm, p = 0.045) and body weight (Ala: 95.7 ± 18 kg, Pro: 91.6 ± 14 kg, p = 0.042) than Pro-homozygotes. Men with ALA-isoform also showed higher systolic ABP levels (Ala: 134 ± 15 mmHg, Pro: 130 ± 14 mmHg, p = 0.004), whereas left ventricular mass index, IMT and PWV were unrelated to isoforms. In contrast, carotid-radial PWV was lower in women with the Ala-isoform (Ala: 7.9 ± 1.0 m/s, Pro: 8.5 ± 1.3 m/s, p = 0.01) and levels of apolipoprotein A1 were higher (Ala: 1.43 ± 0.27 g/l, Pro: 1.35 ± 0.17 g/l, p = 0.03). In conclusion, we found that men with type 2 diabetes having the Ala-isoform of PPARγ Pro12Ala had an unfavorable cardiovascular risk profile, whereas women with this isoform had lower carotid-radial PWV and higher apolipoprotein A1 levels suggesting a beneficial prognosis. These differences according to gender of the ALA isoform in type 2 diabetes deserve further attention.

Correlation between changes of blood pressure with insulin resistance in type 2 diabetes mellitus with 4 weeks of pioglitazone therapy

OBJECTIVE:

To examine effects of pioglitazone (PIO) on systolic, diastolic, pulse and mean blood pressures (SBP, DBP, PP and MP, respectively) in type 2 diabetes mellitus (T2DM).

MATERIALS AND METHODS:

One hundred and six normotensive patients with T2DM with mean fasting blood glucose (FBS; 183 ± 6 mg/dl) were randomly divided into two groups. Test group was treated with 15 mg of PIO in addition to metformin 500 mg three times per day in both groups. SBP, DBP, PP and MP and fasting insulin, FBS and lipid profiles were measured before and after PIO therapy.

RESULTS:

There was a significant reduction in SBP (123 ± 2 vs. 118 ± 2 mmHg, P < 0.05), PP (41 ± 1 vs. 37 ± 1 mmHg, P < 0.05), and MP (95 ± 1 vs. 91 ± 1, P < 0.05). Clinical reduction in DBP was observed but not significant (82 ± 2 vs. 81 ± 1 mmHg, P > 0.05). There was a significant correlation between decline in SBP and DBP with respective baseline values (r = 0.76, P < 0.001 and r = 0.62, P < 0.001, respectively). Changes in PP and MP strongly correlated with baseline values (r = 0.51, P < 0.05 and r = 0.56, P < 0.05, respectively). There was a parallel reduction of FBS (183 ± 2 vs. 121 ± 3, P < 0.001) but reduction in IR or lipid profiles was not significant in test group. Changes in BP were not significant in control group ( P > 0.05).

CONCLUSION:

PIO treatment of T2DM showed early reduction of SBP and MP within first 4 weeks. Results suggest that pharmacodynamic effects of PIO mainly affect the systolic component. We hereby suggest that reduction of BP by PIO is independent from mechanisms of changes in IR and dyslipidaemia in normotensive diabetic patients.

Gender differences in the effects of peroxisome proliferator-activated receptor γ2 gene polymorphisms on metabolic adversity in patients with schizophrenia or schizoaffective disorder

OBJECTIVE

Metabolic syndrome (MS) is a major health problem in schizophrenic patients. Peroxisome proliferator-activated receptor γ2 (PPARγ2) is one of the candidate genes responsible for the liability to metabolic problems. In this study, we investigated the effect of the PPARγ2 gene Pro12Ala and C161T polymorphisms on metabolic adversities in patients with schizophrenia or schizoaffective disorder.

METHODS

Metabolic profiles and PPARγ2 gene polymorphisms were determined in 600 patients (309 men and 291 women) with a clinical diagnosis of schizophrenia or schizoaffective disorder. Metabolic indices and components of MS were compared between patients with different Pro12Ala or C161T genotypes.

RESULTS

In the whole population, the allele frequency of 12Ala and 161T was 4.4% and 24.7% respectively. Both polymorphisms had no significant effect on obesity or metabolic-related traits. However, following gender stratification of the data, we found female 12Ala allele carriers were at greater risk of developing abdominal obesity (OR = 4.0, 95% CI = 1.1-14.2, p = 0.04) and hypertension (OR=2.9, 95% CI = 1.2-7.4, p = 0.02) than female 12Ala allele non-carriers. Male 161T allele carriers had lower insulin levels (p = 0.02) and lower high-density lipoprotein cholesterol (HDL-C) (p = 0.05) levels than male 161T allele non-carriers. Moreover, female 161T allele carriers had higher body weight (p = 0.04), waist circumference (p = 0.05), and systolic blood pressure (p = 0.01), and were at greater risk of developing hypertension (OR = 2.0, 95% CI = 1.1-3.5, p = 0.02). Haplotype analyses showed that PPARγ2 gene polymorphisms were significantly associated with HDL-C level in men and blood pressure in women.

CONCLUSIONS

We did not find an association of PPARγ2 gene polymorphisms with MS or obesity in our schizophrenia sample. But further analyses by gender stratification revealed gender-specific differences in the effect of different PPARγ2 genotypes on certain metabolic adversities in these patients.

Effect of pioglitazone on endothelial function in impaired glucose tolerance

AIM

Flow-mediated dilation (FMD) is a surrogate marker of endothelial function, which has been proposed as a barometer of vascular health. Impaired microvascular response to reactive hyperaemia is thought to be the mechanism behind reduced shear stress and subsequently impaired FMD, which has been associated with cardiovascular events. This study aims to assess the effect of pioglitazone on the vasculature of patients with impaired glucose tolerance (IGT).

MATERIALS AND METHODS

Forty IGT patients with no cardiovascular disease were compared with 24 healthy age- and sex-matched controls. Endothelial function was assessed using FMD of the brachial artery. Adiponectin (ADN) levels were measured and insulin sensitivity was calculated using homeostasis model assessment of insulin resistance (HOMA-IR). A randomised double-blind placebo-controlled trial of the IGT subjects was then performed, with subjects receiving either pioglitazone 30 mg od or matched placebo for 12 weeks before the measurements were repeated.

RESULTS

The IGT subjects had a significantly impaired FMD compared with the controls (p < 0.001). Diastolic shear stress (DSS) was also significantly reduced in IGT (p = 0.04). High molecular weight (HMW) ADN was significantly lower in the IGT group than in controls (p = 0.03). On analysis of the IGT group after 12 weeks treatment, FMD was significantly increased in the pioglitazone group compared with placebo (p = 0.03) as was endothelium-independent dilation (EID) (p = 0.03). A significant increase in total ADN (p < 0.001), HMW ADN (p < 0.001) and HMW/total ratio (p = 0.001) occurred in the pioglitazone group compared with placebo.

CONCLUSIONS

Pioglitazone improved endothelial function in IGT. Treatment with pioglitazone may reduce the risk of cardiovascular disease in this patient group.

Impaired peroxisome proliferator-activated receptor-gamma contributes to phenotypic modulation of vascular smooth muscle cells during hypertension

The phenotypic modulation of vascular smooth muscle cells (VSMCs) plays a pivotal role in hypertension-induced vascular changes including vascular remodeling. The precise mechanisms underlying VSMC phenotypic modulation remain elusive. Here we test the role of peroxisome proliferator-activated receptor (PPAR)-gamma in the VSMC phenotypic modulation during hypertension. Both spontaneously hypertensive rat (SHR) aortas and SHR-derived VSMCs exhibited reduced PPAR-gamma expression and excessive VSMC phenotypic modulation identified by reduced contractile proteins, alpha-smooth muscle actin (alpha-SMA) and smooth muscle 22alpha (SM22alpha), and enhanced proliferation and migration. PPAR-gamma overexpression rescued the expression of alpha-SMA and SM22alpha, and inhibited the proliferation and migration in SHR-derived VSMCs. In contrast, PPAR-gamma silencing exerted the opposite effect. Activating PPAR-gamma using rosiglitazone in vivo up-regulated aortic alpha-SMA and SM22alpha expression and attenuated aortic remodeling in SHRs. Increased activation of phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling was observed in SHR-derived VSMCs. PI3K inhibitor LY294002 rescued the impaired expression of contractile proteins, and inhibited proliferation and migration in VSMCs from SHRs, whereas constitutively active PI3K mutant had the opposite effect. Overexpression or silencing of PPAR-gamma inhibited or excited PI3K/Akt activity, respectively. LY294002 counteracted the PPAR-gamma silencing induced proliferation and migration in SHR-derived VSMCs, whereas active PI3K mutant had the opposite effect. In contrast, reduced proliferation and migration by PPAR-gamma overexpression were reversed by the active PI3K mutant, and further inhibited by LY294002. We conclude that PPAR-gamma inhibits VSMC phenotypic modulation through inhibiting PI3K/Akt signaling. Impaired PPAR-gamma expression is responsible for VSMC phenotypic modulation during hypertension. These findings highlight an attractive therapeutic target for hypertension-related vascular disorders.

Interaction of oxidative stress, nitric oxide and peroxisome proliferator activated receptor gamma in acute renal failure

Oxidative stress has been reported to play a critical role in the pathology of acute renal failure (ARF). An interaction between different reactive species and/or their sources have been the focus of extensive studies. The exact sources of reactive species generated in biological systems under different disease states are always elusive because they are also a part of physiological processes. Exaggerated involvement of different oxidation pathways including NAD(P)H oxidase has been proposed in different models of ARF. An interaction between oxygen species and nitrogen species has drawn extensive attention because of the deleterious effects of peroxynitrite and their possible effects on antioxidant systems. Recent advances in molecular biology have allowed us to understand glomerular function more precisely, especially the organization and importance of the slit diaphragm. Identification of slit diaphragm proteins came as a breakthrough and a possibility of therapeutic manipulation in ARF is encouraging. Transcriptional regulation of the expression of slit diaphragm protein is of particular importance because their presence is crucial in the maintenance of glomerular function. This review highlights the involvement of oxidative stress in ARF, sources of these reactive species, a possible interaction between different reactive species, and involvement of PPARgamma, a nuclear transcription factor in this process.

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.

Vascular smooth muscle cell-selective peroxisome proliferator-activated receptor-gamma deletion leads to hypotension

BACKGROUND

Peroxisome proliferator-activated receptor-gamma (PPARgamma) agonists are commonly used to treat diabetes, although their PPARgamma-dependent effects transcend their role as insulin sensitizers. Thiazolidinediones lower blood pressure (BP) in diabetic patients, whereas results from conventional/tissue-specific PPARgamma experimental models suggest an important pleiotropic role for PPARgamma in BP control. Little evidence is available on the molecular mechanisms underlying the role of vascular smooth muscle cell-specific PPARgamma in basal vascular tone.

METHODS AND RESULTS

We show that vascular smooth muscle cell-selective deletion of PPARgamma impairs vasoactivity with an overall reduction in BP. Aortic contraction in response to norepinephrine is reduced and vasorelaxation is enhanced in response to beta-adrenergic receptor (beta-AdR) agonists in vitro. Similarly, vascular smooth muscle cell-selective PPARgamma knockout mice display a biphasic response to norepinephrine in BP, reversible on administration of beta-AdR blocker, and enhanced BP reduction on treatment with beta-AdR agonists. Consistent with enhanced beta2-AdR responsiveness, we found that the absence of PPARgamma in vascular smooth muscle cells increased beta2-AdR expression, possibly leading to the hypotensive phenotype during the rest phase.

CONCLUSIONS

These data uncovered the beta2-AdR as a novel target of PPARgamma transcriptional repression in vascular smooth muscle cells and indicate that PPARgamma regulation of beta2-adrenergic signaling is important in the modulation of BP.

Endothelium, inflammation, and diabetes

The normal endothelium produces a number of vasodilator substances such as nitric oxide (NO) and prostacyclin (PGI2) that regulate vasomotor tone, reduce platelet aggregation, and inhibit the recruitment and activity of inflammatory cells. The functions of vascular endothelial cells are disturbed in diabetic patients. The major cause for mortality and a great percent of morbidity in patients with diabetes mellitus is atherosclerosis. Insulin has recently been shown to stimulate NO release and the expression of NO synthase by the endothelium. Insulin is thus a vasodilator, has anti-platelet activity, and now has been shown to be anti-inflammatory and thus, potentially anti-atherogenic. Similar anti-inflammatory effects of thiazolidenediones (TZDs), troglitazone, and rosiglitazone suggest that they too may have potential anti-atherogenic effects. These effects of insulin and TZDs are of importance since the two major states of insulin resistance, obesity and type 2 diabetes, are associated with a marked increase in atherosclerosis, coronary heart disease, and stroke. These recent observations have extremely important implications for the understanding of the pathogenesis of atherosclerosis in insulin-resistant states and for a rational approach to their comprehensive treatment, including the prevention of atherosclerosis and its complications. This review challenges the previously proposed hypothesis that hyperinsulinemia represents a common pathophysiological pathway of diabetic complications and advances our hypothesis that insulin, through its effect on the endothelium, leucocytes, and platelets, has anti-inflammatory and thus potentially anti-atherogenic properties. Furthermore, through its anti-inflammatory effects, its use improves clinical outcomes in at least two clinical states characterized by profound inflammation-acute myocardial infarction and sepsis.

Troglitazone up-regulates vascular endothelial argininosuccinate synthase

Vascular endothelial nitric oxide (NO) production via the citrulline-NO cycle not only involves the regulation of endothelial nitric oxide synthase (eNOS), but also regulation of caveolar-localized endothelial argininosuccinate synthase (AS), which catalyzes the rate-limiting step of the cycle. In the present study, we demonstrated that exposure of endothelial cells to troglitazone coordinately induced AS expression and NO production. Western blot analysis demonstrated an increase in AS protein expression. This increased expression was due to transcriptional upregulation of AS mRNA, as determined by quantitative real time RT-PCR and inhibition by 1-d-ribofuranosylbenzimidazole (DRB), a transcriptional inhibitor. Reporter gene assays and EMSA analyses identified a distal PPARgamma response element (PPRE) (-2471 to -2458) that mediated the troglitazone increase in AS expression. Overall, this study defines a novel molecular mechanism through which a thiazolidinedione (TZD) like troglitazone supports endothelial function via the transcriptional up-regulation of AS expression.

Effects of thiazolidinediones on blood pressure

Peroxisome-proliferator-activated receptor-gamma (PPAR-gamma) agonists (known as thiazolidinediones; TDZs) activate nuclear receptors that regulate gene expression; they were developed as insulin-sensitizing drugs to treat type 2 diabetes mellitus. Although the prototypic TZD troglitazone was withdrawn from the market due to hepatic toxicity, rosiglitazone and pioglitazone are mainstays in managing type 2 diabetes mellitus. TZDs exert their hypoglycemic effect by reducing insulin resistance, hence improving insulin sensitivity. However, TZDs also exhibit a broad range of cardiovascular actions, with the clinical consequence of reduction in blood pressure (BP), observed in animal models and human diabetic subjects. The magnitude of reduction appears to be about 4 to 5 mm Hg in systolic and 2 to 4 mm Hg in diastolic BP--sufficient to significantly reduce subsequent cardiovascular event rates. But these BP-reducing properties, which are not present with metformin or sulfonylureas, are particularly important when viewed in conjunction with hypoglycemic effects. A significant proportion of patients with type 2 diabetes mellitus and BP mildly above target range might be successfully treated for both processes with a single drug.

Microalbuminuria in insulin sensitivity in patients with growth hormone-secreting pituitary tumor

CONTEXT

Impaired glucose tolerance and diabetes mellitus are frequently present in acromegalic patients in whom the degree of impaired glucose metabolism seems directly correlated with GH levels. Microalbuminuria is reported to be directly correlated with insulin resistance, and both conditions predict cardiovascular disease mortality.

OBJECTIVE

Our objective was to investigate the microalbuminuria levels as a marker of endothelial dysfunction in acromegalic patients.

DESIGN

We conducted an observational, multicenter, open prospective study.

SUBJECTS

Subjects included 74 patients with active acromegaly (52 with normal glucose tolerance, 16 with impaired glucose tolerance, and six with diabetes), and 50 healthy subjects matched for age, gender, and body mass index were studied as controls.

RESULTS

In the whole group, mean GH and IGF-I levels were 24.2+/-3.9 ng/ml and 700.1+/-23.0 microg/liter, respectively. The insulin sensitivity index (ISI) in the patients was lower than in the controls (P<0.0005). In impaired glucose tolerance and diabetic patients, microalbuminuria was higher than in normal glucose tolerance patients (P<0.05 and P<0.0005 respectively). Hypertensive patients had higher levels of microalbuminuria than normotensive ones (P<0.005). The levels of microalbuminuria related to creatinine were directly correlated with fasting glucose levels (r=0.27; P=0.0019), fasting insulin levels (r=0.28; P=0.017), and insulin after 90 (r=0.26; P=0.027) and 120 min after glucose load (r=0.26; P=0.023) and indirectly correlated with ISI composite (P<0.0001; r=-0.48). By a multivariate analysis, the log-ISI composite was the strongest predictor of microalbuminuria (t=-3.19; P=0.0021).

CONCLUSIONS

Impairment of glucose tolerance in acromegaly is associated with high levels of microalbuminuria. For this reason, microalbuminuria should be part of cardiovascular risk assessment in these patients.

PPARs and the kidney in metabolic syndrome

The metabolic syndrome (MetS) is defined by a set of metabolic risk factors, including insulin resistance, central obesity, dyslipidemia, hyperglycemia, and hypertension for type 2 diabetes and cardiovascular disease. Although both retrospective and prospective clinical studies have revealed that MetS is associated with chronic renal disease, even with a nondiabetic cause, the cellular and molecular mechanisms in this association remain largely uncharacterized. Recently, increasing evidence suggests that peroxisome proliferator-activated receptors (PPARs), a subgroup of the nuclear hormone receptor superfamily of ligand-activated transcription factors, may play an important role in the pathogenesis of MetS. All three members of the PPAR nuclear receptor subfamily, PPARalpha, -beta/delta, and -gamma, are critical in regulating insulin sensitivity, adipogenesis, lipid metabolism, inflammation, and blood pressure. PPARs have also been implicated in many renal pathophysiological conditions, including diabetic nephropathy and glomerulosclerosis. Ligands for PPARs such as hypolipidemic PPARalpha activators, and antidiabetic thiazolidinedione PPARgamma agonists affect not only diverse aspects of MetS but also renal disease progression. Emerging data suggest that PPARs may be potential therapeutic targets for MetS and its related renal complications. This review focuses on current knowledge of the role of PPARs in MetS and discusses the potential therapeutic utility of PPAR modulators in the treatment of kidney diseases associated with MetS.

Peroxisome proliferator-activated receptor-gamma agonists and diabetes: current evidence and future perspectives

Since their initial availability in 1997, the thiazolidinediones (TZDs) have become one of the most commonly prescribed classes of medications for type 2 diabetes. In addition to glucose control, the TZDs have a number of pleiotropic effects on myriad traditional and non-traditional risk factors for diabetes. TZDs may benefit cardiovascular parameters, such as lipids, blood pressure, inflammatory biomarkers, endothelial function and fibrinolytic state. In this review, we summarise the experimental, preclinical and clinical data regarding the effects of the TZDs in conditions for which they are indicated and discuss their potential in the treatment of other conditions.

Rosuvastatin increases vascular endothelial PPARgamma expression and corrects blood pressure variability in obese dyslipidaemic mice

AIMS

Statins improve atherosclerotic diseases through cholesterol-reducing effects. Whether the latter exclusively mediate similar benefits, e.g. on hypertension, in the metabolic syndrome is unclear. We examined the effects of rosuvastatin on the components of this syndrome, as reproduced in mice doubly deficient in LDL receptors and leptin (DKO).

METHODS AND RESULTS

DKO received rosuvastatin (10 mg/kg/day or 20 mg/kg/day) or saline for 12 weeks. Saline-treated DKO mice had elevated blood pressure (BP) and nitric oxide-sensitive BP variability recorded by telemetry. Compared with saline, rosuvastatin (20 mg/kg/day) had no effect on weight gain and a minor effect on plasma cholesterol. Despite incomplete correction of insulin sensitivity, rosuvastatin fully corrected BP and its variability (P = 0.01), in conjunction with upregulation of PPARgamma (but not PPARalpha) in the aortic arch. Rosuvastatin similarly increased PPARgamma (P = 0.002) and SOD1 (P = 0.01) expression in isolated endothelial cells. Both GW9662, a PPARgamma-specific antagonist, and siRNA raised against PPARgamma abrogated rosuvastatin's effect, which was reproduced in PPARgamma- (but not PPARalpha-) dependent transactivation assays.

CONCLUSION

Beyond partial improvement in insulin sensitivity, rosuvastatin normalized BP homeostasis in obese dyslipidaemic mice independently of changes in body weight or plasma cholesterol. Upregulation of PPARgamma and SOD1 in the endothelium may be involved as a unique vasculoprotective effect of statin treatment.

Effects of pioglitazone and rosiglitazone on aortic vascular function in rat genetic hypertension

Glitazones have beneficial antihypertensive effects independent of their insulin-sensitizing action. We have studied the effects of pioglitazone and rosiglitazone on the endothelial ability to counteract vascular smooth muscle contractility in genetic hypertension. To achieve this, we measured isometric responses of aortic segments obtained from spontaneously hypertensive rats. The effects of glitazones on endothelial function were studied by assessing the endothelial modulation of phenylephrine-induced isometric contractions (10(-9)-10(-5) M) in the presence or absence of pioglitazone or rosiglitazone (10(-5) M), added directly to an organ bath or orally administered to the rats (pioglitazone, 10 mg/kg). The role of both NO and prostanoids was analyzed by performing experiments in the presence of N(G)-nitro-L-arginine methyl ester (L-NAME) and/or indomethacin (both 10(-5) M) in the organ bath. Concentration-dependent contractions to L-NAME (10(-6)-3 x 10(-4) M) in the presence or absence of glitazones were carried out as an estimation of basal NO release. Pioglitazone, but not rosiglitazone, increased contractile responses to phenylephrine in intact vessels. The contractile responses to phenylephrine obtained in the presence of glitazones were markedly diminished by indomethacin, but enhanced by L-NAME. Analogous results were obtained in aortas from pioglitazone-chronically treated animals. L-NAME concentration-dependent contractions were enhanced by both glitazones. Both glitazones lowered the sensitivity to acetylcholine (10(-9)-10(-5) M). In conclusion, pioglitazone and rosiglitazone alter vascular function differentially and through endothelium-dependent mechanisms. These drugs act over the same pathways on the endothelium where they have a dual action, increasing both production of vasoconstrictor prostanoids and NO. The balance between both vasoactive substances determines the vascular response to glitazones.

A meta-analysis of 94,492 patients with hypertension treated with beta blockers to determine the risk of new-onset diabetes mellitus

Beta blockers used for the treatment of hypertension may be associated with increased risk for new-onset diabetes mellitus (DM). A search of Medline, PubMed, and EMBASE was conducted for randomized controlled trials of patients taking beta blockers as first-line therapy for hypertension with data on new-onset DM and follow-up for > or =1 year. Twelve studies evaluating 94,492 patients fulfilled the inclusion criteria. Beta-blocker therapy resulted in a 22% increased risk for new-onset DM (relative risk 1.22, 95% confidence interval [CI] 1.12 to 1.33) compared with nondiuretic antihypertensive agents. A higher baseline fasting glucose level (odds ratio [OR] 1.01, 95% CI 1.00 to 1.02, p = 0.004) and greater systolic (OR 1.05, 95% CI 1.05 to 1.08, p = 0.001) and diastolic (OR 1.06, 95% CI 1.01 to 1.10, p = 0.011) blood pressure differences between the 2 treatment modalities were significant univariate predictors of new-onset DM. Multivariate meta-regression analysis showed that a higher baseline body mass index (OR 1.17, 95% CI 1.01 to 1.33, p = 0.034) was a significant predictor of new-onset DM. The risk for DM was greater with atenolol, in the elderly, and in studies in which beta blockers were less efficacious antihypertensive agents and increased exponentially with increased duration on beta blockers. For the secondary end points, beta blockers resulted in a 15% increased risk for stroke, with no benefit for the end point of death or myocardial infarction. In conclusion, beta blockers are associated with an increased risk for new-onset DM, with no benefit for the end point of death or myocardial infarction and with a 15% increased risk for stroke compared with other agents. This risk was greater in patients with higher baseline body mass indexes and higher baseline fasting glucose levels and in studies in which beta blockers were less efficacious antihypertensive agents compared with other treatments.

Thiazolidinediones: effects on insulin resistance and the cardiovascular system

Thiazolidinediones (TZDs) have been used for the treatment of hyperglycaemia in type 2 diabetes for the past 10 years. They may delay the development of type 2 diabetes in individuals at high risk of developing the condition, and have been shown to have potentially beneficial effects on cardiovascular risk factors. TZDs act as agonists of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) primarily in adipose tissue. PPAR-gamma receptor activation by TZDs improves insulin sensitivity by promoting fatty acid uptake into adipose tissue, increasing production of adiponectin and reducing levels of inflammatory mediators such as tumour necrosis factor-alpha (TNF-alpha), plasminogen activator inhibitor-1(PAI-1) and interleukin-6 (IL-6). Clinically, TZDs have been shown to reduce measures of atherosclerosis such as carotid intima-media thickness (CIMT). However, in spite of beneficial effects on markers of cardiovascular risk, TZDs have not been definitively shown to reduce cardiovascular events in patients, and the safety of rosiglitazone in this respect has recently been called into question. Dual PPAR-alpha/gamma agonists may offer superior treatment of insulin resistance and cardioprotection, but their safety has not yet been assured.

Physiology, Genetics, and Cardiovascular Disease: Focus on African Americans

The disproportionate impact of cardiovascular disease in African Americans is well recognized. Not only do risk factors such as obesity occur at a higher rate in the African-American community, but this population experiences a greater mortality from cardiovascular disease than their white counterparts. The cardiovascular system is regulated in part by two opposing mediators linking the risk factors of obesity, vascular dysfunction, and diabetes. One of these mediators--angiotensin II--increases blood pressure, impairs endothelial function, decreases peroxisome proliferator activated-receptor gamma, and is proinflammatory, growth stimulating, profibrotic, and proatherogenic. The other mediator, peroxisome proliferator activated-receptor gamma, lowers blood pressure, improves endothelial function, decreases angiotensin II type 1 receptor function, and is anti-inflammatory, growth-inhibiting, antifibrotic, and antiatherogenic. Genotypic variants have been discovered that affect the functioning of both of these important systems. Some of these variants--like some genotypic variants discovered in the adrenergic system--occur with different frequencies in African Americans than in Americans of European descent and may help to explain racial/ethnic differences in susceptibility to cardiovascular disease and aspects of the response to treatment. Recognition of these genotypic differences may permit the development of therapies tailored to individual patients.

Response to pioglitazone treatment is associated with the lipoprotein lipase S447X variant in subjects with type 2 diabetes mellitus

To investigate the influence of the S447X variant in lipoprotein lipase (LPL) gene on the response rate to therapy with the thiazolidinedione pioglitazone. A total of 113 diabetic patients were treated with pioglitazone 30 mg for 10 weeks. Response to the pioglitazone treatment was defined by either a >10% relative reduction in fasting blood glucose (FBG) or a more than 1% decrease in glycosylated haemoglobin (HbA1c) values after 10 weeks of pioglitazone treatment. The genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism method. Using the criteria >10% relative reduction in FBG after 10 weeks of pioglitaone treatment, responder frequency to pioglitazone treatment in S447S genotype group is significantly higher than S447X genotype group. Meanwhile, the S447X genotype conferred a statistically significant 0.538-fold reduction in response rate to pioglitazone treatment relative to the S447S genotype. Moreover, pioglitazone treatment has significantly beneficial effects on serum lipid profile and blood pressure in S447S genotype carriers. The S447X variant in LPL gene may be a cause for therapy modification by pioglitazone.

Diabetes mellitus and anesthesia

Diabetes mellitus is an extremely common condition with specific associated comorbidity. Its incidence is rising. Diabetic patients have more perioperative complications than nondiabetic patients. These complications may be related to the presence of organ damage secondary to the diabetes, rather than the defects in carbohydrate metabolism themselves, or to perioperative hyperglycemia. Several new drugs are available for the treatment of diabetes, and these are associated with specific and significant side effects, and varying lengths of action with which the anesthetist should be familiar. Few data are available regarding recommendations for fasting in the presence of these newer drugs. In the postoperative period and during cardiac surgery, hyperglycemia has been shown to be detrimental, and should probably be sought and managed aggressively. The incidence of intraoperative hyperglycemia in noncardiac surgery patients is not as well-defined, nor are the effects of aggressive management.

The PPARgamma ligand, rosiglitazone, reduces vascular oxidative stress and NADPH oxidase expression in diabetic mice

Oxidative stress plays an important role in diabetic vascular dysfunction. The sources and regulation of reactive oxygen species production in diabetic vasculature continue to be defined. Because peroxisome proliferator-activated receptor gamma (PPARgamma) ligands reduced superoxide anion (O(2)(-.)) generation in vascular endothelial cells in vitro by reducing NADPH oxidase and increasing Cu/Zn superoxide dismutase (SOD) expression, the current study examined the effect of PPARgamma ligands on vascular NADPH oxidase and O(2)(-.) generation in vivo. Lean control (db(+)/db(-)) and obese, diabetic, leptin receptor-deficient (db(-)/db(-)) mice were treated with either vehicle or rosiglitazone (3 mg/kg/day) by gavage for 7-days. Compared to controls, db(-)/db(-) mice weighed more and had metabolic derangements that were not corrected by treatment with rosiglitazone for 1-week. Aortic O(2)(-.) generation and mRNA levels of the NADPH oxidase subunits, Nox-1, Nox-2, and Nox-4 as well as Nox-4 protein expression were elevated in db(-)/db(-) compared to db(+)/db(-) mice, whereas aortic Cu/Zn SOD protein and PPARgamma mRNA levels were reduced in db(-)/db(-) mice. Treatment with rosiglitazone for 1-week significantly reduced aortic O(2)(-.) production and the expression of Nox-1, 2, and 4 but failed to increase Cu/Zn SOD or PPARgamma in aortic tissue from db(-)/db(-) mice. These data demonstrate that the vascular expression of Nox-1, 2, and 4 subunits of NADPH oxidase is increased in db(-)/db(-) mice and that short-term treatment with the PPARgamma agonist, rosiglitazone, has the potential to rapidly suppress vascular NADPH oxidase expression and O(2)(-.) production through mechanisms that do not appear to depend on correction of diabetic metabolic derangements.