Endothelial Insulin Resistance Research Articles

Abstract 340: Psychological Stress Impairs Both Endothelial Function and Insulin Sensitivity via Activation of Inflammation and ER Stress Pathways Mediated by Corticotropin-Releasing Hormone

Background: Psychological stress may contribute to atherogenesis, although the underlying mechanism is poorly understood yet. We studied the role of corticotropin-releasing hormone (CRH) in the pathogenesis of stress-induced endothelial dysfunction and insulin resistance with specific focus on inflammation and ER stress pathways. Methods and Results: Immobilization stress (IS) was applied (2 hr/d) for 14 d to male 8-wk OLETF rats, whereas control groups comprised of rats without IS (n≥7 for each). 14d-IS decreased acetylcholine (Ach)-induced NO production, measured by direct NO electrochemical microsensor, from the aorta along with decreased expression of eNOS mRNA compared with control group. 14d-IS did not significantly change plasma glucose, but increased plasma insulin (342.5±6.3 vs. 496.0±51.6 pg/ml, p<0.05) and HOMA-IR (3.1±0.2 vs.4.7±0.5 mmol/LxμIU/mL, p<0.05) compared with control group. IS increased phosphorylation of both IRS1 serine and ERK, and increased expression of ER stress marker BiP. IS also increased translocation of NF-kB subunit p65 into nucleal fraction, and increased mRNA expression of both TNF-α and MCP-1 in the liver. Real-time RT-qPCR study showed that 1d IS increased expression of CRH mRNA and urocortin 2 mRNA in the hypothalamus by 2.5 folds and expression of CRH receptor type 2 mRNA in the aorta by 7.8 folds compared with control group. In cultured monocyte U937 cells, CRH induced translocation of NF-kB subunit p65 into nuclear fraction, and increased expression of BiP, phosphorylated inositol requiring enzyme 1, and MCP-1 mRNA. In cultured HUVECs, CRH pretreatment inhibited insulin-stimulated eNOS phosphorylation at Ser 1177 . Conclusions: Psychological stress impairs both endothelial function and insulin sensitivity probably via activation of NF-kB-mediated inflammation and ER stress pathways by CRH.

Methylglyoxal impairs endothelial insulin sensitivity both in vitro and in vivo.

Insulin exerts a direct action on vascular cells, thereby affecting the outcome and progression of diabetic vascular complications. However, the mechanism through which insulin signalling is impaired in the endothelium of diabetic individuals remains unclear. In this work, we have evaluated the role of the AGE precursor methylglyoxal (MGO) in generating endothelial insulin resistance both in cells and in animal models. Time course experiments were performed on mouse aortic endothelial cells (MAECs) incubated with 500 μmol/l MGO. The glyoxalase-1 inhibitor S-p-bromobenzylglutathione-cyclopentyl-diester (SpBrBzGSHCp2) was used to increase the endogenous levels of MGO. For the in vivo study, an MGO solution was administrated i.p. to C57BL/6 mice for 7 weeks. MGO prevented the insulin-dependent activation of the IRS1/protein kinase Akt/endothelial nitric oxide synthase (eNOS) pathway, thereby blunting nitric oxide (NO) production, while extracellular signal-regulated kinase (ERK1/2) activation and endothelin-1 (ET-1) release were increased by MGO in MAECs. Similar results were obtained in MAECs treated with SpBrBzGSHCp2. In MGO- and SpBrBzGSHCp2-exposed cells, inhibition of ERK1/2 decreased IRS1 phosphorylation on S616 and rescued insulin-dependent Akt activation and NO generation, indicating that MGO inhibition of the IRS1/Akt/eNOS pathway is mediated, at least in part, by ERK1/2. Chronic administration of MGO to C57BL/6 mice impaired whole-body insulin sensitivity and induced endothelial insulin resistance. MGO impairs the action of insulin on the endothelium both in vitro and in vivo, at least in part through an ERK1/2-mediated mechanism. These findings may be instrumental in developing novel strategies for preserving endothelial function in diabetes.

High fat feeding induces exaggerated endothelial dysfunction and insulin resistance in rats exposed to maternal separation (1085.7)

We previously reported that adult male rats exposed to MatSep (3 hrs/day from day 2 to 14 of life) display normal baseline cardiovascular parameters but enhanced responses to angiotensin II (AngII) compared to controls (C, non‐MatSep littermates). We tested the hypothesis that a chronic HF diet (60% fat cal., 0.4 salt; 6 months) exaggerates metabolic and/or cardiovascular indices in MatSep rats. Plasma fasting glucose and insulin were higher in MatSep vs. C rats (p<0.05), showing a greater HOMA index in MatSep than C rats (1.0±0.1 vs. 1.7±0.1, p<0.05). Plasma adiponectin was lower in MatSep vs. C rats (19±2 vs. 28±2 ug/ml, p<0.05), although body weight and leptin were similar between groups. No differences in mean arterial pressure or heart rate were observed between MatSep and C rats (105±2 vs. 102±2mmHg; 326±6 vs. 317±3 bpm; n=6). Wire myography of thoracic aortae showed a greater vasoconstrictive response (%max constriction) to AngII (17±2 vs. 6±1, p<0.05) and phenylephrine (59±4 vs. 29±5, p<0.05) from MatSep rats. L‐NAME pre‐incubation revealed a loss of NO buffering capacity to AngII in MatSep aortae only (p<0.05). Impaired acetylcholine‐induced relaxation was greater in aortae from MatSep rats (49±6 vs. 27±3 % relax, p<0.05). These data reveal that MatSep followed by HF feeding induces a synergistic effect on disrupting vascular function and glucose homeostasis increasing the risk to cardiovascular disease.Grant Funding Source: HL111354 and PO1 HL69999

The dipeptidyl peptidase-4 inhibitor teneligliptin improved endothelial dysfunction and insulin resistance in the SHR/NDmcr-cp rat model of metabolic syndrome

Diabetes mellitus, hypertension and metabolic syndrome are major risk factors for the occurrence of cardiovascular events. In this study, we used spontaneous hypertensive rat (SHR)/NDmcr-cp (cp/cp) (SHRcp) rats as a model for metabolic syndrome to examine the effects of dipeptidyl peptidase (DPP)-4 inhibition on hypertension, glucose metabolism and endothelial dysfunction. First, we confirmed that SHRcp rats showed very severe obesity, hypertension and endothelial dysfunction phenotypes from 14 to 54 weeks of age. Next, we examined whether the DPP-4 inhibitor teneligliptin (10 mg kg(-1) per day per os for 12 weeks) could modify any of these phenotypes. Treatment with teneligliptin significantly improved hyperglycemia and insulin resistance, as evidenced by an oral glucose tolerance test and homeostasis model assessment for insulin resistance, respectively. Teneligliptin showed no effects on systolic blood pressure or heart rate. In regard to endothelial function, the vasodilator response to acetylcholine was significantly impaired in SHRcp rats when compared with WKY rats. Long-term treatment with teneligliptin significantly attenuated endothelial dysfunction through the upregulation of endothelium-derived nitric oxide synthase mRNA. These results demonstrate that long-term treatment with teneligliptin significantly improved endothelial dysfunction and glucose metabolism in a rat model of metabolic syndrome, suggesting that teneligliptin treatment might be beneficial for patients with hypertension and/or diabetes.

Microvascular dysfunction in the course of metabolic syndrome induced by high-fat diet

BackgroundMetabolic syndrome (MetS) is associated with increased risk of cardiovascular disease (CVD). One important feature underlying the pathophysiology of many types of CVD is microvascular dysfunction. Although components of MetS are themselves CVD risk factors, the risk is increased when the syndrome is considered as one entity. We aimed to characterize microvascular function and some of its influencing factors in the course of MetS development.MethodsDevelopment of MetS in C57BL/6 mice on a high-fat diet (HFD, 51% of energy from fat) was studied. The initial phase of MetS (I-MetS) was defined as the first 2 weeks of HFD feeding, with the fully developed phase occurring after 8 weeks of HFD. We characterized these phases by assessing changes in adiposity, blood pressure, and microvascular function. All data are presented as mean ± standard error (SEM). Differences between cumulative dose–response curves of myograph experiments were calculated using non-linear regression analysis. In other experiments, comparisons between two groups were made with Student’s t-test. Comparisons between more than two groups were made using one-way ANOVA with Tukey post-hoc test. A probability value <0.05 was considered statistically significant.ResultsI-MetS mice presented with weight gain, blood pressure elevation, and microvascular dysfunction characterized by augmented vasoconstriction. This finding, contrary to those in mice with fully developed MetS, was not associated with endothelial dysfunction, insulin resistance, or systemic inflammation. In the initial phase, perivascular adipose tissue showed no sign of inflammation and had no influence on the pattern of vasoconstriction. These findings suggest that the onset of hypertension in MetS is strongly influenced by vascular smooth muscle cell dysfunction and independent of important factors known to influence microvascular function and consequently blood pressure levels.ConclusionWe identified in I-MetS the occurrence of isolated augmented vasoconstriction along with blood pressure elevation, but not the presence of classical MetS components known to influence microvascular function. These findings increase our understanding of the pathophysiology of CVD risk associated with MetS.

Statins and Renin-Angiotensin System Inhibitor Combination Treatment to Prevent Cardiovascular Disease

Hypercholesterolemia and hypertension are common risk factors for cardiovascular disease (CVD). Updated guidelines emphasize target reductions of overall cardiovascular risks. Experimental studies have shown reciprocal relationships between insulin resistance (IR) and endothelial dysfunction. Hypercholesterolemia and hypertension have a synergistic deleterious effect on IR and endothelial dysfunction. Unregulated renin-angiotensin system (RAS) is important in the pathogenesis of atherosclerosis and hypertension. Various strategies with different classes of antihypertensive medications to reach target goals have failed to reduce residual CVD risk further. Of interest, treating moderate cholesterol elevations with low-dose statins in hypertensive patients reduced CVD risk by 35-40% further. Therefore, statins are important in reducing CVD risk. Unfortunately, statin therapy causes IR and increases the risk of type 2 diabetes mellitus. RAS inhibitors improve both endothelial dysfunction and IR. Further, cross-talk between hypercholesterolemia and RAS exists at multiple steps of IR and endothelial dysfunction. In this regard, combined therapy with statins and RAS inhibitors demonstrates additive/synergistic effects on endothelial dysfunction and IR in addition to lowering cholesterol levels and blood pressure when compared with either monotherapy in patients. This is mediated by both distinct and interrelated mechanisms. Therefore, combined therapy with statins and RAS inhibitors may be important in developing optimal management strategies in patients with hypertension, hypercholesterolemia, diabetes, metabolic syndrome, or obesity to prevent CVD.

Endothelial dysfunction and insulin resistance in young women with polycystic ovarian syndrome.

To evaluate whether there is a correlation between insulin resistance and nitric oxide-related endothelial dysfunction in patients with polycystic ovarian syndrome (PCOS). The study was conducted with 25 young women with PCOS and 25 young healthy women, between 18 and 35 years of age. Plasma asymmetric dimethylarginine (ADMA) levels, serum nitric oxide (NO) levels, and homeostatic model assessment of insulin resistance (HOMA-IR) rates were measured in both the patient and control groups. Plasma ADMA levels were significantly higher in PCOS patients than in the controls (P = 0.001). Serum NO levels were significantly lower in patients than in the controls (P = 0.008). The HOMA-IR rates, accepted as an insulin resistance parameter, were significantly higher in patients than in the controls (P = 0.001). Results of the present study indicate that, independent of age, body mass index, and blood lipid profile, there is significant insulin resistance in PCOS patients. However, no correlation was found between HOMA-IR as an insulin resistance determinant and altered ADMA and NO levels. This finding may indicate that there are additional mechanisms of cardiovascular risks in PCOS patients other than insulin resistance.

Correlation between Homeostatic Model Assessment-estimated Insulin Resistance (HOMA-IR) with Asymmetric Dimethylarginine (ADMA) in Prehypertension

BACKGROUND: Not only hypertension, prehypertension has been reported to be linked with increased cardiovascular morbidity and mortality risks as well. Prehypertension has three-fold hypertension and two-fold cardiovascular risks. Pathomechanism that links hypertension with cardiovascular is related with endothelial dysfunction and insulin resistance. Endothelial dysfunction occurs when nitric oxide (NO) biological function was impaired, whereas shown by asymmetric dimethylarginine (ADMA). Subjects with prehypertension had higher insulin resistance events than normotension, whereas shown by homeostatic model assessment-estimated insulin resistance (HOMA-IR). This research was conducted to investigate the correlation of HOMA-IR with ADMA in prehyper- and normo-tension.METHODS: A cross-sectional comparative research was designed. Subjects were recruited and divided into prehyper- and normo-tensive groups. ADMA was measured using ELISA method, while HOMA-IR was calculated by the ratio of fasting insulin and glucose. Spearman 1-tail and Mann Whitney statistical analyses were performed.RESULTS: Comparing to normotensive group, elevated levels of HOMA-IR and ADMA in prehypertensive group were shown, but not significant. In prehypertensive group, we found significant correlation between HOMA-IR and ADMA.CONCLUSION: Insulin resistance and endothelial dysfunction was elevated in prehyper-compared to normotension.KEYWORDS: prehypertension, insulin resistance, endothelial dysfunction, HOMA-IR, ADMA

Protective effects of dark chocolate on endothelial function and diabetes

Relationship between cocoa consumption and cardiovascular disease, particularly focusing on clinical implications resulting from the beneficial effects of cocoa consumption on endothelial function and insulin resistance. This could be of clinical relevance and may suggest the mechanistic explanation for the reduced risk of cardiovascular events reported in the different studies after cocoa intake. Increasing evidence supports a protective effect of cocoa consumption against cardiovascular disease. Cocoa and flavonoids from cocoa have been described to improve endothelial function and insulin resistance. A proposed mechanism could be considered in the improvement of the endothelium-derived vasodilator nitric oxide by enhancing nitric oxide synthesis or by decreasing nitric oxide breakdown. The endothelium plays a pivotal role in the arterial homeostasis, and insulin resistance is the most important pathophysiological feature in various prediabetic and diabetic states. Reduced nitric oxide bioavailability with endothelial dysfunction is considered the earliest step in the pathogenesis of atherosclerosis. Further, insulin resistance could account, at least in part, for the endothelial dysfunction. Endothelial dysfunction has been considered an important and independent predictor of future development of cardiovascular risk and events. Cocoa and flavonoids from cocoa might positively modulate these mechanisms with a putative role in cardiovascular protection.

Ranolazine's sweet side – improvement of glycaemic control by the novel mechanism of skeletal muscle microvascular recruitment

Type II diabetes mellitus is a major public health problem afflicting in excess of 250 million individuals worldwide. The presence of this condition in patients with coronary artery disease more than doubles their risk for cardiovascular events. Among the most critical factors are the attendant development of endothelial dysfunction and insulin resistance, which contribute to impaired glycaemic control and acceleration of atherosclerosis. Contemporary therapies have important limitations and safety concerns, as treatment with agents in extensive clinical use, including β-adrenergic receptor blocking agents, thiazide diuretics, and calcium channel antagonists, is associated with increased rates of newly diagnosed diabetes as a result of pro-diabetic effects. These limitations have prompted a search for alternative modalities of drug action. In the current issue of The Journal of Physiology, Fu and colleagues (2013) explored whether ranolazine can improve blood flow and distribution of insulin through α-adrenergic receptor-mediated vasodilatation. Ranolazine is a weak competitive antagonist of α-adrenergic receptors (Allely et al. 1993) and in the conscious dog this antagonism is unmasked by activation of the autonomic nervous system (Zhao et al. 2011). Fu and colleagues (2013) reported that in the therapeutic range of doses ranolazine recruited muscle microvasculature, resulting in a significant >2-fold increase in skeletal muscle blood flow and volume and a substantial enhancement of insulin-mediated whole-body disposal in the range of 30%. In addition, ranolazine improved delivery of insulin into skeletal muscle. Ranolazine increased endothelial nitric oxide synthase (eNOS) phosphorylation and cyclic adenosine monophosphate (cAMP) production without affecting endothelial insulin uptake. Isolated phenylephrine pre-constricted arterial rings were relaxed in the presence of ranolazine, indicating an α-adrenergic receptor-mediated effect. This observation is consistent with evidence obtained in vivo in which the vasoconstrictor effect of intracoronary phenylephrine was abolished by ranolazine (Nieminen et al. 2011) and the vasopressor response to methoxamine was blunted by ranolazine in a dose-dependent manner (Wang et al. 2008). Fu and colleagues (2013) also found that the vasodilatory effects on the pre-capillary arterioles occurred via actions on both the endothelium and smooth muscle cells. Overall, their observations indicate that at therapeutic concentrations ranolazine acutely recruits skeletal muscle microvasculature, increasing microvascular exchange surface area and perfusion. This effect, in combination with the drug's α-adrenergically mediated vasodilatation of pre-capillary arterioles, improves insulin delivery to skeletal muscle and glucose use. This intriguing study by Fu and coworkers (2013) raises important questions relevant to potential clinical applications. As the present studies were performed on an acute basis in normal rats, it remains to be determined whether microvascular recruitment persists following chronic administration in a diabetic animal model. Also, is there evidence that this action of ranolazine on muscle microvasculature operates in patients with various degrees of insulin resistance and early and late stage type 2 diabetes? Clinical trials have demonstrated that ranolazine significantly improves glycaemic control as suggested by reduced levels of glycated haemoglobin (HbA1c) in diabetic as well as non-diabetic subjects (Timmis et al. 2006; Morrow et al. 2009; Chisholm et al. 2010; Kosiborod et al. 2013). Use of ranolazine is also attractive in light of the excellent safety profile shown in the MERLIN-TIMI 36 (Metabolic Efficiency With Ranolazine for Less Ischemia in NonST-Elevation Acute Coronary Syndromes Thrombolysis in Myocardial Infarction 36) trial, which enrolled 6560 patients with cardiovascular disease, 2028 (31%) of whom had pre-existing diabetes (Morrow et al. 2009). However, the mechanisms whereby ranolazine reduces HbA1c remain unknown. The clinical implications of this study are multifold and significant. Essentially, the authors have identified mechanisms that may underlie ranolazine's unique salutary effects, which can potentially improve the cardiovascular health of diabetic patients while reducing myocardial ischaemic events and risk for atrial and ventricular arrhythmias. Although considerable further work will be required to assess fully the clinical applicability of Fu and coworkers’ novel findings (2013), available clinical evidence suggests that the basic concept presented in the current study is promising and worthy of vigorous pursuit.

Prokineticin Receptor‐1 Is a New Regulator of Endothelial Insulin Uptake and Capillary Formation to Control Insulin Sensitivity and Cardiovascular and Kidney Functions

BackgroundReciprocal relationships between endothelial dysfunction and insulin resistance result in a vicious cycle of cardiovascular, renal, and metabolic disorders. The mechanisms underlying these impairments are unclear. The peptide hormones prokineticins exert their angiogenic function via prokineticin receptor‐1 (PKR1). We explored the extent to which endothelial PKR1 contributes to expansion of capillary network and the transcapillary passage of insulin into the heart, kidney, and adipose tissues, regulating organ functions and metabolism in a specific mice model.Methods and ResultsBy combining cellular studies and studies in endothelium‐specific loss‐of‐function mouse model (ec‐PKR1−/−), we showed that a genetically induced PKR1 loss in the endothelial cells causes the impaired capillary formation and transendothelial insulin delivery, leading to insulin resistance and cardiovascular and renal disorders. Impaired insulin delivery in endothelial cells accompanied with defective expression and activation of endothelial nitric oxide synthase in the ec‐PKR1−/− aorta, consequently diminishing endothelium‐dependent relaxation. Despite having a lean body phenotype, ec‐PKR1−/− mice exhibited polyphagia, polydipsia, polyurinemia, and hyperinsulinemia, which are reminiscent of human lipodystrophy. High plasma free fatty acid levels and low leptin levels further contribute to the development of insulin resistance at the later age. Peripheral insulin resistance and ectopic lipid accumulation in mutant skeletal muscle, heart, and kidneys were accompanied by impaired insulin‐mediated Akt signaling in these organs. The ec‐PKR1−/− mice displayed myocardial fibrosis, low levels of capillary formation, and high rates of apoptosis, leading to diastolic dysfunction. Compact fibrotic glomeruli and high levels of phosphate excretion were found in mutant kidneys. PKR1 restoration in ec‐PKR1−/− mice reversed the decrease in capillary recruitment and insulin uptake and improved heart and kidney function and insulin resistance.ConclusionsWe show a novel role for endothelial PKR1 signaling in cardiac, renal, and metabolic functions by regulating transendothelial insulin uptake and endothelial cell proliferation. Targeting endothelial PKR1 may serve as a therapeutic strategy for ameliorating these disorders.

Circulation Research Thematic Synopsis Diabetes and Obesity

<i>Circulation Research</i> Thematic Synopsis Diabetes and Obesity

'Adiposopathy' and cardiovascular disease: the benefits of bariatric surgery.

Obesity is an independent risk factor for cardiovascular disease (CVD) and promotes CVD risk factors. Bariatric surgery has gained much favor because it ameliorates CVD. This review examines the current evidence for the mechanism behind this, which is currently thought to occur in part by reduction of adiposopathy, or dysfunctional adipose tissue, through modulation of adipokine secretion. Increased visceral fat in obesity leads to adiposopathy, due to the chronic inflammation present in this tissue. Bariatric surgery causes weight loss as well as reduction in insulin resistance, hypertension, dyslipidemia, cardiac hypertrophy, and mortality. It also causes changes in the adipokines adiponectin, leptin, and C-reactive protein, but not in tumor necrosis factor-α. These changes contribute to improved CVD risk, possibly through decrease of chronic inflammation. The modulations in adipokine secretion that occur after bariatric surgery are involved with reduction in CVD risk factors, CVD, and CV mortality. On the basis of the known anti-inflammatory effects of adiponectin and the pro-inflammatory effects of leptin and CRP, reduction in chronic inflammation associated with less visceral fat after surgery may contribute to the reduction in CVD. This may promote improvement of endothelial dysfunction and insulin resistance. Further work is necessary to explore these relationships.

Tectorigenin Attenuates Palmitate-Induced Endothelial Insulin Resistance via Targeting ROS-Associated Inflammation and IRS-1 Pathway.

Tectorigenin is a plant isoflavonoid originally isolated from the dried flower of Pueraria thomsonii Benth. Although its anti-inflammatory and anti-hyperglycosemia effects have been well documented, the effect of tectorigenin on endothelial dysfunction insulin resistance involved has not yet been reported. Herein, this study aims to investigate the action of tectorigenin on amelioration of insulin resistance in the endothelium. Palmitic acid (PA) was chosen as a stimulant to induce ROS production in endothelial cells and successfully established insulin resistance evidenced by the specific impairment of insulin PI3K signaling. Tectorigenin effectively inhibited the ability of PA to induce the production of reactive oxygen species and collapse of mitochondrial membrane potential. Moreover, tectorigenin presented strong inhibition effect on ROS-associated inflammation, as TNF-α and IL-6 production in endothelial cells was greatly reduced with suppression of IKKβ/NF-κB phosphorylation and JNK activation. Tectorigenin also can inhibit inflammation-stimulated IRS-1 serine phosphorylation and restore the impaired insulin PI3K signaling, leading to a decreased NO production. These results demonstrated its positive regulation of insulin action in the endothelium. Meanwhile, tectorigenin down-regulated endothelin-1 and vascular cell adhesion molecule-1 overexpression, and restored the loss of insulin-mediated vasodilation in rat aorta. These findings suggested that tectorigenin could inhibit ROS-associated inflammation and ameliorated endothelial dysfunction implicated in insulin resistance through regulating IRS-1 function. Tectorigenin might have potential to be applied for the management of cardiovascular diseases involved in diabetes and insulin resistance.

A Prospective Case-Controlled Study of Endothelial Function in Patients with Mild to Moderate Psoriasis

Aim: The aim of this study is to investigate endothelial dysfunction in psoriasis patients with non-invasive methods. Materials and Methods: Fifty-three psoriasis patients and 53 healthy individuals were included in the study. Carotid artery intimae-media thickness and brachial artery flow-mediated dilation was measured both in patient and control groups. Results: Mean age, gender, body mass index, smoking habits, anthropometric measurements and arterial blood pressure values were similar in both groups. Mean psoriasis area and severity index score of psoriasis patients was 6.35±6.81. Triglyceride level was significantly higher (p0.05) and high density lipoprotein cholesterol level was significantly lower (p 0.05) in psoriasis patients when compared with the controls. Insulin resistance was found to be statistically higher in psoriasis patients group than the control group (p0.05); but flow-mediated dilation was found to be statistically significantly lower in psoriasis patients than the control group (p0.05). FT3 level was also found to be statistically significantly lower in psoriasis patients than the control group (p=0.05). Conclusion: This study showed endothelial dysfunction and insulin resistance in psoriasis patients with low disease activity even in the absence of clinical cardiovascular disease. Thyroid function tests could supply information about cardiovascular risk.

SIRT1, heme oxygenase-1 and NO-mediated vasodilation in a human model of endogenous angiotensin II type 1 receptor antagonism: implications for hypertension

Reduced NO availability is associated with endothelial dysfunction, hypertension, insulin resistance and cardiovascular remodeling. SIRT1 upregulates eNOS activity and inhibits endothelial cell senescence, and reduced SIRT1 is related to oxidative stress and reduced NO-dependent dilation. Bartter's/Gitelman's syndromes (BS/GS) are rare diseases that feature a picture opposite to that of hypertension in that they present with normo/hypotension, reduced oxidative stress and a lack of cardiovascular remodeling, notwithstanding high levels of angiotensin II and other vasopressors, upregulation of NO system, and increased NO-dependent vasodilation (FMD), as well as increase in both endothelial progenitor cells and insulin sensitivity. To our knowledge, in BS/GS patients SIRT1 has never been evaluated. BS/GS patients' mononuclear cell SIRT1 (western blot), FMD (B-mode scan of the right brachial artery) and heme oxygenase (HO)-1 (sandwich immunoassay), a potent antioxidant protein, were compared with the levels in untreated stage 1 essential hypertensive patients (HPs) and in healthy subjects (C). SIRT1 (1.86 ± 0.29 vs. 1.18 ± 0.18 (HP) vs. 1.45 ± 0.18 (C) densitometric units, P<0.0001) and HO-1 protein (9.44 ± 3.09 vs. 3.70 ± 1.19 (HP) vs. 5.49 ± 1.04 (C) ng ml⁻¹, P<0.0001) levels were higher in BS/GS patients than in the other groups. FMD was also higher in BS/GS patients: 10.52 ± 2.22% vs. 5.99 ± 1 .68% (HP) vs. 7.99 ± 1.13% (C) (ANOVA: P<0.0001). A strong and significant correlation between SIRT1 and FMD was found only in BS/GS patients (r(2)=0.63, P=0.0026). Increased SIRT1 and its direct relationship with increased FMD in BS/GS patients, while strengthening the relationship among SIRT1, NO and vascular function in humans, point toward a role for reduced SIRT1 in the endothelial dysfunction of hypertension.

Erectile dysfunction may be the first clinical sign of insulin resistance and endothelial dysfunction in young men

The purpose of this study is to investigate the possible underlying pathogenesis of erectile dysfunction (ED) without well-known etiology in young men under the age of 40 years. 192 patients and 33 normal controls were enrolled. ED was evaluated by using the International Index of Erectile Function-5 (IIEF-5) questionnaire. Traditional cardiovascular risk factors, hormone levels, and vascular parameters were measured. Insulin resistance (IR) was measured by homeostasis model assessment (HOMA). Patients with ED had significantly higher levels of systolic blood pressure (SBP), high-sensitivity C-reactive protein (Hs-CRP), high Insulin resistance index (HOMA-IR) and carotid intima-media thickness (IMT), compared with controls. The brachial artery endothelium-dependent flow-mediated vasodilation (FMD) values were significantly lower in ED patients. By multivariate logistic regression analysis, FMD, SBP, Hs-CRP and HOMA-IR were significantly associated with ED. In receiver-operating characteristic (ROC) analysis, FMD was a significant predictor of ED (area under the curve (AUC) 0.933, p < 0.001). The cutoff value of FMD <10.4 % had sensitivity of 81.3 % and specificity of 100 %. HOMA-IR was also proven to be predictor of ED (AUC of HOMA-IR 0.759, p < 0.001). ED may be the first clinical sign of endothelial dysfunction and a clinical marker of cardiovascular and metabolic diseases. Subclinical endothelial dysfunction and insulin resistance may be the underlying pathogenesis of ED in young patients without well-known etiology. Measurement of FMD, HOMA-IR can improve our ability to predict and treat ED, as well as subclinical cardiovascular disease early in young men.

Dihydropyridine calcium channel blockers inhibit non-esterified-fatty-acid-induced endothelial and rheological dysfunction

Circulating NEFAs (non-esterified fatty acids) from adipose tissue lipolysis lead to endothelial dysfunction and insulin resistance in patients with the metabolic syndrome or Type 2 diabetes mellitus. The aim of the present study was to test the hypothesis that DHP (dihydropyridine) CCBs (calcium channel blockers) prevent NEFA-induced endothelial and haemorheological dysfunction independently of their antihypertensive properties. Using a double-blind cross-over study design, nifedipine, amlodipine, diltiazem or placebo were administered to eight healthy subjects for 2 days before each study day. On the study days, the following were assessed before and after the infusion of lipid and heparin to raise serum NEFAs: endothelial function, by measuring FBF (forearm blood flow) responses to ACh (acetylcholine); leucocyte activation, by ex vivo measurement of plasma MPO (myeloperoxidase) levels, adherent leucocyte numbers and whole blood transit time through microchannels; and oxidative stress, by determining plasma levels of d-ROMs (derivatives of reactive oxygen metabolites). Effects of the CCBs on NF-κB (nuclear factor κB) p65 phospholylation stimulated by NEFAs were assessed in cultured monocytic cells in vitro. Elevated NEFAs reduced the responses to ACh and significantly increased whole blood transit time, adherent leucocyte numbers and d-ROMs. Nifedipine and amlodipine, but not diltiazem, prevented NEFA-induced endothelial dysfunction, leucocyte activation and enhancement of oxidative stress without affecting BP (blood pressure), whereas all these drugs prevented NEFA-induced p65 activation in vitro. These results suggest that DHP CCBs, independent of their antihypertensive properties in humans, prevent NEFA-induced endothelial and haemorheological dysfunction through inhibition of NEFA-induced leucocyte activation, although the sensitivity to drugs of leucocyte Ca2+ channels may differ among cells.

203 MUTATING THE IGF-1 ON THE VASCULAR ENDOTHELIUM: DIVERGENT EFFECTS ON WHOLE BODY AND ENDOTHELIAL INSULIN RESISTANCE

IntroductionEndothelial dysfunction is associated with the onset of atherosclerosis and cardiovascular disease. Whole body and endothelial cell insulin resistance can result in reduced nitric oxide (NO) bioavailability; this is a...

E: TARGETING NOX2 NADPH OXIDASE IN INSULIN RESISTANCE RELATED ENDOTHELIAL DYSFUNCTION

Laboratory based cell culture studies have shown that reactive oxygen species (ROS) induced oxidative stress as an important molecular mechanism in the development and progression of cardiovascular diseases. Despite that, large scale clinical trials have shown that general antioxidants are not only ineffective in treating cardiovascular diseases but also, in some cases, can have harmful effects. In this context, the next logical step is to specifically targeting critical molecules in ROS generation rather than using non-specific antioxidants. Insulin resistance, the antecedent of type 2 diabetes mellitus, can itself initiate various vascular complications of diabetes before the development of clinically diagnosable diabetes. Insulin resistance is characterised by excessive endothelial cell generation of cytotoxic concentrations of ROS. NADPH oxidases (NOX), a group of ROS producing enzymes, have been recently shown as the major source of excessive ROS in insulin resistant endothelial cells. We hypothesised that specific targeting of NOX could be the way forward in developing antioxidant molecules as therapeutic agents for vascular diseases. In this study, we examined the role of NOX enzymes and specifically Nox2 isoform in superoxide generation in 2 complementary in vivo models (endothelial specific and whole body) of human insulin resistance. Using gp91-ds tat peptide, a non-specific NOX inhibitor, we have specifically targeted NOX generated superoxide production. For acute inhibition we have treated cells or tissues with 50 M gp91ds-tat or control peptide for 30 minutes. For chronic inhibition, mice were implanted with osmotic mini-pumps which delivered 10 mg/kg/day of drug for 28 days. The excessive level of superoxide found in insulin resistant endothelial cells was significantly reduced by acute or chronic treatment with gp91ds-tat peptide. Also NO dependent vasorelaxation response, which was impaired in insulin resistance, was improved with gp91ds-tat peptide treatment. Since insulin resistant endothelial cells showed higher expression of Nox2 isoform, Nox2 gene was knocked down using siRNA which significantly reduced superoxide levels. Furthermore, to clearly examine the involvement of Nox2 isoform in this context, double transgenic mice with endothelial specific insulin resistance and Nox2 gene knockout were generated. These mice showed reduced superoxide production and improved vascular function. Thus Nox2 is the critical molecule in insulin resistance induced endothelial dysfunction. In conclusion, our study establishes that pharmacological inhibition of NOX as a novel way to treat insulin resistance related vascular disease.