Obesity-induced Vascular Dysfunction Research Articles

Therapeutic modulation of epigenetic readers rescues obesity-induced vascular dysfunction: role of endothelium and perivascular adipose tissue

Abstract Background/Introduction Bromodomain and extraterminal proteins (BET), particularly BRD4, are epigenetic readers modulating transcriptional programs implicated in inflammation, cancer and renal disease. Therapeutic potential of BRD4 modulation in cardiometabolic disorders remains elusive. Purpose We investigate BRD4-related transcriptional programs and therapeutic modulation in mouse and human models of cardiometabolic disease. Methods Small arteries (100-300 μM) from healthy subjects (n=13) and patients with obesity (n=13) were dissected from visceral fat biopsies collected during elective laparoscopy and mounted on a pressurised myograph to assess the ex-vivo effects of BRD4 inhibition on vascular function. Vasorelaxation to acetylcholine and acetylcholine+L-NAME were evaluated at baseline and after incubation with the BRD4 inhibitor RVX-208. Anti-IL-1β, anti-IL-6 receptor and anti-TNF-α were also employed to assess the relative contribution of distinct BRD4-related pathways. Vasorelaxation was performed in the presence or in the absence of perivascular adipose tissue (PVAT). An experimental mouse model of cardiometabolic disease (high-fat diet+L-NAME supplementation) was orally administered RVX-208 (150 mg/kg) or vehicle for 10 days (n=6 each group) to test in vivo effect of chronic BRD4 inhibition on endothelial and PVAT functions. Vascular and PVAT levels of cytosolic and mitochondrial ROS and nitric oxide were assessed by confocal microscopy; protein and gene expression was measured by Western blot and qPCR. Transcriptional changes upon BRD4 inhibition were investigated by a custom PCR array. Results In patients with obesity, endothelial-dependent vasorelaxation and vascular nitric oxide availability were impaired. ROS levels, as well as TNF-α, IL-1β and IL-6, were increased in the vessel wall and PVAT. In these subjects, RVX-208 substantially attenuated ex-vivo vascular dysfunction. The effect was more pronounced in vessels with intact PVAT, suggesting a restoration of the PVAT anti-contractile phenotype (Figure 1). Distinct ex-vivo modulation of well-established inflammatory pathways showed that the effect observed with BRD4 inhibition was stronger than with anti-IL-1β, anti-IL-6 receptor and anti-TNF-α. In vivo, chronic treatment with RVX-208 restored endothelial vasorelaxation by rescuing PVAT dysfunction. Gene expression profiling in PVAT from cardiometabolic mice unveiled hexokinase-2 (HK2) - a glycolytic enzyme implicated in mitochondrial dysfunction and inflammation - as the top downregulated gene by RVX-208 treatment (Figure 2). Conclusions Therapeutic modulation of BRD4 restores cardiometabolic-related vascular dysfunction and PVAT anti-contractile properties. These effects are explained by a suppression of PVAT inflammation (IL-1β, IL-6 and TNF-α), likely driven by HK2 activation. BET inhibitors might represent promising epi-drugs for the prevention and treatment of vascular dysfunction, a hallmark of cardiometabolic disease.

Endothelial Nitric Oxide Synthase in the Perivascular Adipose Tissue.

Perivascular adipose tissue (PVAT) is a special type of ectopic fat depot that adheres to most vasculatures. PVAT has been shown to exert anticontractile effects on the blood vessels and confers protective effects against metabolic and cardiovascular diseases. PVAT plays a critical role in vascular homeostasis via secreting adipokine, hormones, and growth factors. Endothelial nitric oxide synthase (eNOS; also known as NOS3 or NOSIII) is well-known for its role in the generation of vasoprotective nitric oxide (NO). eNOS is primarily expressed, but not exclusively, in endothelial cells, while recent studies have identified its expression in both adipocytes and endothelial cells of PVAT. PVAT eNOS is an important player in the protective role of PVAT. Different studies have demonstrated that, under obesity-linked metabolic diseases, PVAT eNOS may be even more important than endothelium eNOS in obesity-induced vascular dysfunction, which may be attributed to certain PVAT eNOS-specific functions. In this review, we summarized the current understanding of eNOS expression in PVAT, its function under both physiological and pathological conditions and listed out a few pharmacological interventions of interest that target eNOS in PVAT.

Leonurine Attenuates Obesity-Related Vascular Dysfunction and Inflammation.

Oxidative stress in adipose tissue is a crucial pathogenic mechanism of obesity-associated cardiovascular diseases. Chronic low-grade inflammation caused by obesity increases ROS production and dysregulation of adipocytokines. Leonurine (LEO) is an active alkaloid extracted from Herba Leonuri and plays a protective role in the cardiovascular system. The present study tested whether LEO alleviates inflammation and oxidative stress, and improves vascular function in an obese mouse model. Here, we found that obesity leads to inflammation and oxidative stress in epididymal white adipose tissue (EWAT), as well as vascular dysfunction. LEO significantly improved inflammation and oxidative stress both in vivo and in vitro. Obesity-induced vascular dysfunction was also improved by LEO as evidenced by the ameliorated vascular tone and decreased mesenteric artery fibrosis. Using mass spectrometry, we identified YTHDF1 as the direct target of LEO. Taken together, we demonstrated that LEO improves oxidative stress and vascular remodeling induced by obesity and targets YTHDF1, raising the possibility of LEO treating other obesity-related metabolic syndromes.

Thioredoxin deficiency exacerbates vascular dysfunction during diet-induced obesity in small mesenteric artery in mice.

Thioredoxin (Trx) is a small cellular redox protein with established antioxidant and disulfide reductase properties. We hypothesized that Trx deficiency in mice would cause increased oxidative stress with consequent redox imbalance that would exacerbate obesity-induced vascular dysfunction. Non-transgenic (NT, C57BL/6) and dominant-negative Trx (dnTrx-Tg, low levels of redox-active protein) mice were either fed a normal diet (NC) or high fat diet plus sucrose (HFS) diet for 4months (3-month HFD+ 1-month HFS). Weight gain, glucose tolerance test (GTT), insulin tolerance test (ITT), and other metabolic parameters were performed following NC or HFS diet. Arterial structural remodeling and functional parameters were assessed by myography. Our study found that dnTrx mice with lower levels of active Trx exacerbated myogenic tone, inward arterial remodeling, arterial stiffening, phenylephrine-induced contraction, and endothelial dysfunction of MA. Additionally, FeTMPyP, a peroxynitrite decomposition catalyst, acutely decreased myogenic tone and contraction and normalized endothelial function in MA from dnTrx-Tg mice on HFS via increasing nitric oxide (NO)-mediated relaxation. Our results indicate that deficiency of active Trx exacerbates MA contractile and relaxing properties during diet-induced obesity demonstrating that loss of redox balance in obesity is a key mechanism of vascular endothelial dysfunction.

Melatonin reverses the loss of the anticontractile effect of perivascular adipose tissue in obese rats.

Perivascular adipose tissue (PVAT) undergoes functional changes in obesity. Increased oxidative stress is a central mechanism whereby obesity induces loss of the anticontractile effect of PVAT. Melatonin is an antioxidant that displays vasoprotective action in cardiovascular disease. Here, we sought to investigate whether melatonin would restore the anticontractile effect of periaortic PVAT in obesity. Male Wistar Hannover rats were treated for 10weeks with a high-calorie diet. Melatonin (5mg/kg/d, p.o., gavage) was administered for 2weeks. Functional findings showed that obesity-induced loss of the anticontractile effect of PVAT and treatment with melatonin reversed this response. Tiron [a scavenger of superoxide anion (O2 - )] restored the anticontractile effect of PVAT in aortas from obese rats, suggesting a role for reactive oxygen species (ROS) in such response. Decreased superoxide dismutase (SOD) activity and augmented levels of ROS were detected in periaortic PVAT from obese rats. These responses were accompanied by decreased levels of nitric oxide (NO) in PVAT. Treatment with melatonin restored SOD activity, decreased ROS levels, and increased NO bioavailability in PVAT from obese rats. Here, we first reported the beneficial effects of melatonin in periaortic PVAT in obesity. Melatonin reversed the adverse effects of obesity in PVAT that included overproduction of ROS, reduced SOD activity, and decreased bioavailability of NO. Therefore, PVAT may constitute an important target for the treatment of obesity-induced vascular dysfunction and melatonin emerges as a potential tool in the management of the vascular complications induced by obesity.

Knockout of vascular smooth muscle EGF receptor in a mouse model prevents obesity-induced vascular dysfunction and renal damage in vivo

Aims/hypothesisObesity causes type 2 diabetes leading to vascular dysfunction and finally renal end-organ damage. Vascular smooth muscle (VSM) EGF receptor (EGFR) modulates vascular wall homeostasis in part via serum response factor (SRF), a major regulator of VSM differentiation and a sensor for glucose. We investigated the role of VSM-EGFR during obesity-induced renovascular dysfunction, as well as EGFR–hyperglycaemia crosstalk.MethodsThe role of VSM-EGFR during high-fat diet (HFD)-induced type 2 diabetes was investigated in a mouse model with inducible, VSM-specific EGFR-knockout (KO). Various structural and functional variables as well as transcriptome changes, in vivo and ex vivo, were assessed. The impact of hyperglycaemia on EGFR-induced signalling and SRF transcriptional activity and the underlying mechanisms were investigated at the cellular level.ResultsWe show that VSM-EGFR mediates obesity/type 2 diabetes-induced vascular dysfunction, remodelling and transcriptome dysregulation preceding renal damage and identify an EGFR–glucose synergism in terms of SRF activation, matrix dysregulation and mitochondrial function. EGFR deletion protects the animals from HFD-induced endothelial dysfunction, creatininaemia and albuminuria. Furthermore, we show that HFD leads to marked changes of the aortic transcriptome in wild-type but not in KO animals, indicative of EGFR-dependent SRF activation, matrix dysregulation and mitochondrial dysfunction, the latter confirmed at the cellular level. Studies at the cellular level revealed that high glucose potentiated EGFR/EGF receptor 2 (ErbB2)-induced stimulation of SRF activity, enhancing the graded signalling responses to EGF, via the EGFR/ErbB2–ROCK–actin–MRTF pathway and promoted mitochondrial dysfunction.Conclusions/interpretationVSM-EGFR contributes to HFD-induced vascular and subsequent renal alterations. We propose that a potentiated EGFR/ErbB2–ROCK–MRTF–SRF signalling axis and mitochondrial dysfunction underlie the role of EGFR. This advanced working hypothesis will be investigated in mechanistic depth in future studies. VSM-EGFR may be a therapeutic target in cases of type 2 diabetes-induced renovascular disease.Data availabilityThe datasets generated during and/or analysed during the current study are available in: (1) share_it, the data repository of the academic libraries of Saxony-Anhalt (https://doi.org/10.25673/32049.2); and (2) in the gene expression omnibus database with the study identity GSE144838 (https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE144838).Graphical abstract

NADPH oxidase 4 mediates the protective effects of physical activity against obesity-induced vascular dysfunction.

Physical activity is one of the most potent strategies to prevent endothelial dysfunction. Recent evidence suggests vaso-protective properties of hydrogen peroxide (H2O2) produced by main endothelial NADPH oxidase isoform 4 (Nox4) in the vasculature. Therefore, we hypothesized that Nox4 connects physical activity with vaso-protective effects. Analysis of the endothelial function using Mulvany Myograph showed endothelial dysfunction in wild-type (WT) as well as in C57BL/6J/ Nox4-/- (Nox4-/-) mice after 20 weeks on high-fat diet (HFD). Access to running wheels during the HFD prevented endothelial dysfunction in WT but not in Nox4-/- mice. Mechanistically, exercise led to an increased H2O2 release in the aorta of WT mice with increased phosphorylation of eNOS pathway member AKT serine/threonine kinase 1 (AKT1). Both H2O2 release and phosphorylation of AKT1 were diminished in aortas of Nox4-/- mice. Deletion of Nox4 also resulted in lower intracellular calcium release proven by reduced phenylephrine-mediated contraction, whilst potassium-induced contraction was not affected. H2O2 scavenger catalase reduced phenylephrine-induced contraction in WT mice. Supplementing H2O2 increased phenylephrine-induced contraction in Nox4-/- mice. Exercise-induced peroxisome proliferative-activated receptor gamma, coactivator 1 alpha (Ppargc1a), as key regulator of mitochondria biogenesis in WT but not Nox4-/- mice. Furthermore, exercise-induced citrate synthase activity and mitochondria mass were reduced in the absence of Nox4. Thus, Nox4-/- mice became less active and ran less compared with WT mice. Nox4 derived H2O2 plays a key role in exercise-induced adaptations of eNOS and Ppargc1a pathway and intracellular calcium release. Hence, loss of Nox4 diminished physical activity performance and vascular protective effects of exercise.

Nebivolol Improves Obesity-Induced Vascular Remodeling by Suppressing NLRP3 Activation.

Nebivolol is a novel β-adrenergic receptor (β-AR) blocker with anti-inflammatory and antioxidant properties. The NLRP3 inflammasome plays a pivotal role in the pathogenesis of obesity-induced vascular dysfunction. Our study aimed to explore the effect of nebivolol on the NLRP3 inflammasome and vascular remodeling in diet-induced obese rats. Eight-week-old Sprague-Dawley male rats were fed with either a standard chow diet or a high-fat diet (HFD) for 8 weeks. Next, the obese rats were subdivided into 3 groups as follows: (1) HFD control group, (2) HFD with low doses of nebivolol (5 mg/kg·d), and (3) HFD with high doses of nebivolol (10 mg/kg·d). A 4-week treatment with nebivolol improved acetylcholine-induced vascular relaxation in accordance with an increased aortic endothelial nitric oxide synthase. Nebivolol attenuated NLRP3 inflammasome activation and suppressed autophagy. In parallel, nebivolol enhanced the levels of phase-II detoxifying enzymes, including superoxide dismutase and catalase. These effects were associated with an increased β3-AR level. Moreover, nebivolol treatment significantly increased Adenosine 5'-monophosphate (AMP)-activated protein kinase activity and decreased phosphorylation of the mammalian target of rapamycin. These results demonstrated that nebivolol improves obesity-induced vascular remodeling by attenuating NLRP3 inflammasome activation and restoring the antioxidant defense.

Obesity-induced vascular dysfunction and arterial stiffening requires endothelial cell arginase 1.

Obesity-induced vascular dysfunction and arterial stiffening requires endothelial cell arginase 1.

Obesity-induced vascular dysfunction and arterial stiffening requires endothelial cell arginase 1.

Elevation of arginase activity has been linked to vascular dysfunction in diabetes and hypertension by a mechanism involving decreased nitric oxide (NO) bioavailability due to L-arginine depletion. Excessive arginase activity also can drive L-arginine metabolism towards the production of ornithine, polyamines, and proline, promoting proliferation of vascular smooth muscle cells and collagen formation, leading to perivascular fibrosis. We hypothesized that there is a specific involvement of arginase 1 expression within the vascular endothelial cells in this pathology. To test this proposition, we used models of type 2 diabetes and metabolic syndrome. Studies were performed using wild type (WT), endothelial-specific arginase 1 knockout (EC-A1-/-) and littermate controls(A1con) mice fed high fat-high sucrose (HFHS) or normal diet (ND) for 6 months and isolated vessels exposed to palmitate-high glucose (PA/HG) media. Some WT mice or isolated vessels were treated with an arginase inhibitor, ABH [2-(S)-amino-6-boronohexanoic acid. In WT mice, the HFHS diet promoted increases in body weight, fasting blood glucose, and post-prandial insulin levels along with arterial stiffening and fibrosis, elevated blood pressure, decreased plasma levels of L-arginine, and elevated L-ornithine. The HFHS diet or PA/HG treatment also induced increases in vascular arginase activity along with oxidative stress, reduced vascular NO levels, and impaired endothelial-dependent vasorelaxation. All of these effects except obesity and hypercholesterolemia were prevented or significantly reduced by endothelial-specific deletion of arginase 1 or ABH treatment. Vascular dysfunctions in diet-induced obesity are prevented by deletion of arginase 1 in vascular endothelial cells or arginase inhibition. These findings indicate that upregulation of arginase 1 expression/activity in vascular endothelial cells has an integral role in diet-induced cardiovascular dysfunction and metabolic syndrome.

Obesity-induced vascular inflammation involves elevated arginase activity.

Obesity-induced vascular dysfunction involves pathological remodeling of the visceral adipose tissue (VAT) and increased inflammation. Our previous studies showed that arginase 1 (A1) in endothelial cells (ECs) is critically involved in obesity-induced vascular dysfunction. We tested the hypothesis that EC-A1 activity also drives obesity-related VAT remodeling and inflammation. Our studies utilized wild-type and EC-A1 knockout (KO) mice made obese by high-fat/high-sucrose (HFHS) diet. HFHS diet induced increases in body weight, fasting blood glucose, and VAT expansion. This was accompanied by increased arginase activity and A1 expression in vascular ECs and increased expression of tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), interleukin-10 (IL-10), vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1) mRNA and protein in both VAT and ECs. HFHS also markedly increased circulating inflammatory monocytes and VAT infiltration by inflammatory macrophages, while reducing reparative macrophages. Additionally, adipocyte size and fibrosis increased and capillary density decreased in VAT. These effects of HFHS, except for weight gain and hyperglycemia, were prevented or reduced in mice lacking EC-A1 or treated with the arginase inhibitor 2-(S)-amino-6-boronohexanoic acid (ABH). In mouse aortic ECs, exposure to high glucose (25 mM) and Na palmitate (200 μM) reduced nitric oxide production and increased A1, TNF-α, VCAM-1, ICAM-1, and MCP-1 mRNA, and monocyte adhesion. Knockout of EC-A1 or ABH prevented these effects. HFHS diet-induced VAT inflammation is mediated by EC-A1 expression/activity. Limiting arginase activity is a possible therapeutic means of controlling obesity-induced vascular and VAT inflammation.

The role of perivascular adipose tissue in obesity-induced vascular dysfunction.

Under physiological conditions, perivascular adipose tissue (PVAT) attenuates agonist‐induced vasoconstriction by releasing vasoactive molecules including hydrogen peroxide, angiotensin 1–7, adiponectin, methyl palmitate, hydrogen sulfide, NO and leptin. This anticontractile effect of PVAT is lost under conditions of obesity. The central mechanism underlying this PVAT dysfunction in obesity is likely to be an ‘obesity triad’ (consisting of PVAT hypoxia, inflammation and oxidative stress) that leads to the impairment of PVAT‐derived vasoregulators. The production of hydrogen sulfide, NO and adiponectin by PVAT is reduced in obesity, whereas the vasodilator response to leptin is impaired (vascular leptin resistance). Strikingly, the vasodilator response to acetylcholine is reduced only in PVAT‐containing, but not in PVAT‐free thoracic aorta isolated from diet‐induced obese mice, indicating a unique role for PVAT in obesity‐induced vascular dysfunction. Furthermore, PVAT dysfunction has also been observed in small arteries isolated from the gluteal/visceral fat biopsy samples of obese individuals. Therefore, PVAT may represent a new therapeutic target for vascular complications in obesity. A number of approaches are currently being tested under experimental conditions. Potential therapeutic strategies improving PVAT function include body weight reduction, enhancing PVAT hydrogen sulfide release (e.g. rosiglitazone, atorvastatin and cannabinoid CB1 receptor agonists) and NO production (e.g. arginase inhibitors), inhibition of the renin–angiotensin–aldosterone system, inhibition of inflammation with melatonin or cytokine antagonists, activators of AMP‐activated kinase (e.g. metformin, resveratrol and diosgenin) and adiponectin releasers or expression enhancers.Linked ArticlesThis article is part of a themed section on Molecular Mechanisms Regulating Perivascular Adipose Tissue – Potential Pharmacological Targets? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.20/issuetoc

Erratum. APPL1 Counteracts Obesity-Induced Vascular Insulin Resistance and Endothelial Dysfunction by Modulating the Endothelial Production of Nitric Oxide and Endothelin-1 in Mice. Diabetes 2011;60:3044-3054.

In the article listed above, an erroneous duplication was made during the process of image assembly for total ERK1/2 in Fig. 4 A . Lanes 4 and 5 in the original experiment were duplicated by mistake when loading …

Uncoupling of Endothelial Nitric Oxide Synthase in Perivascular Adipose Tissue of Diet-Induced Obese Mice.

The present study was conducted to investigate the contribution of perivascular adipose tissue (PVAT) to vascular dysfunction in a mouse model of diet-induced obesity. Obesity was induced in male C57BL/6J mice with a high-fat diet for 20 weeks, and vascular function was studied with myograph. In PVAT-free aortas isolated from obese mice, the endothelium-dependent, nitric oxide-mediated vasodilator response to acetylcholine remained normal. In contrast, a clear reduction in the vasodilator response to acetylcholine was observed in aortas from obese mice when PVAT was left in place. Adipocytes in PVAT were clearly positive in endothelial nitric oxide synthase (eNOS) staining, and PVAT nitric oxide production was significantly reduced in obese mice. High-fat diet had no effect on eNOS expression but led to eNOS uncoupling, evidenced by diminished superoxide production in PVAT after eNOS inhibition. As mechanisms for eNOS uncoupling, arginase induction and l-arginine deficiency were observed in PVAT. Obesity-induced vascular dysfunction could be reversed by ex vivo l-arginine treatment and arginase inhibition. Diet-induced obesity leads to l-arginine deficiency and eNOS uncoupling in PVAT. The combination therapy with l-arginine and arginase inhibitors may represent a novel therapeutic strategy for obesity-induced vascular disease.

Abstract 179: Targeted Inhibition of Plasminogen Activator Inhibitor-1 Attenuates Weight Gain and Prevents Vascular Dysfunction Following a High Fat Diet

Introduction: Elevated plasminogen activator inhibitor-1 (PAI-1) is associated with obesity, but there is controversy whether PAI-1 causes or is a consequence of obesity. We sought to determine whether targeted PAI-1 inhibition with a novel small molecule antagonist (TM5441) alters the development of obesity and/or obesity-induced vascular dysfunction in a diet-induced obesity model. Methods and Results: C57BL/6J mice were fed control, high fat diet (HFD), or high fat diet with TM5441 (HFD+TM5441) for 12 weeks. The HFD had marked weight gain (77±5%) as compared with control (32±2%). TM5441 significantly attenuated weight gain (49±8%, p=0.0075, Figure). HFD-induced hepatic triglyceride accumulation was attenuated by TM5441 (116±31 vs. 76±35 mg trig/g liver, p=0.03). Energy expenditure was reduced in the HFD compared to control (11.1±0.4 vs. 12.9±0.4 kcal/h/kg, p=0.005). However, HFD+TM5441 maintained a level of energy expenditure that was similar to control (13.2±0.6 kcal/h/kg, p=NS). The HFD group demonstrated higher systolic and diastolic blood pressure (141±3; 112±3 mm Hg) compared with control (122±7, 94±8; P<0.05 for both), while administration of TM5441 prevented diet-associated increase (120±6; 93±7 mm Hg, p=NS compared to control) at week 12. Pressure myography of mesenteric arteries in the HFD showed a significant rightward shift in the constrictor response to phenylephrine as compared to control (EC50: 14.5uM vs. 25.1uM, p=0.002). The HFD+TM5441 was similar to control (p=NS). Conclusions: Inhibition of PAI-1 with TM5441 attenuates weight gain, enhances energy expenditure, and prevents obesity-related vascular dysfunction in a murine model of obesity.

Enhanced p47 phox NADPH sub‐unit expression impairs conductance and resistance vascular function in obese mice

Metabolic disease is associated with vascular complication. However, the direct contribution and role of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit p47phox in obesity-induced vascular dysfunction is not fully determined. Thus, p47phox-/- and control mice were fed with high fat diet (HFD) for three months. Systolic blood pressure was normal in all groups. HFD increased body weight similarly in all groups; however, blood glucose was significantly increased in control mice compared to p47phox-/- mice. Insulin induced vascular reactivity was significantly impaired in control mice when fed with HFD but not affected in p47phox-/- mice. Vascular contraction in response to phenylephrine was not affected in all groups. Vascular endothelium-dependent relaxation (EDR) was impaired in control group fed with HFD but protected in p47phox-/- mice fed with HFD. The improvement of vascular function was associated with the rescue of eNOS and Akt signaling, and reduction in NOX2 and NOX4 mRNA levels and NADPH oxidase activity. The present study determines that HFD impairs vascular function through the augmented expression and activity of NADPH oxidase subunit p47phox. Therefore, p47phox could be an important target to improve vascular function in metabolic syndrome.

Aging, arterial stiffness, and hypertension.

Although the etiology of essential hypertension remains unknown, it is clear that multiple factors may contribute to the pathogenesis of hypertension. Hypertension is an outcome of the interaction of multiple genetic and environmental factors. Several epidemiological studies indicated that the incidence of arterial stiffness and hypertension and related cardiovascular disease (stroke, myocardial infarction) is higher in the aged than in the young population.1–4 The prevalence of arterial stiffening and hypertension increases with age.1,5 Based on an epidemiological study,6 the prevalence of hypertension is more than doubled in the elderly than in the young population. More than two-thirds of individuals after 65 years of age experience hypertension according to the Seventh Report of the Joint National Committee (JNC-7).7 Therefore, it is generally thought that hypertension is an aging disorder. In recent years, metabolic syndrome and hypertension are increasingly seen in the middle-aged and young populations. In these subpopulations, insulin resistance and overproduction of adipokines impair endothelial and heart function leading to early and accelerated cardiovascular aging. It was reported that premature aging (progeria) is associated with accelerated vascular stiffening or vascular aging.8 Aging is defined as the age-related decline in physiological function essential for survival and fertility. Cardiovascular aging is an important factor that determines life span. The wall of large conduit arteries, especially aorta, thicken and lose elasticity over time, and this process results in an increase in pulse wave velocity, an important and reliable measure of arterial stiffness. The increased arterial stiffness, whatever its underlying causes, would reduce the reservoir/buffering function of the conduit arteries near the heart and increase pulse wave velocity, both of which increase systolic and pulse pressure. Therefore, aging-related hypertension is characterized by a significant increase in systolic blood pressure with no change or even a …

Arginase inhibition restores endothelial function in diet-induced obesity

Arginase may play a major role in the regulation of vascular function in various cardiovascular disorders by impairing nitric oxide (NO) production. In the current study, we investigated whether supplementation of the arginase inhibitor Nω-hydroxy-nor-l-arginine (nor-NOHA) could restore endothelial function in an animal model of diet-induced obesity. Arginase 1 expression was significantly lower in the aorta of C57BL/6J mice fed a high-fat diet (HFD) supplemented with nor-NOHA (40mgkg-1/day) than in mice fed HFD without nor-NOHA. Arginase inhibition led to considerable increases in eNOS expression and NO levels and significant decreases in the levels of circulating ICAM-1. These findings were further confirmed by the results of siRNA-mediated knockdown of Arg in human umbilical vein endothelial cells. In conclusion, arginase inhibition can help restore dysregulated endothelial function by increasing the eNOS-dependent NO production in the endothelium, indicating that arginase could be a therapeutic target for correcting obesity-induced vascular endothelial dysfunction.

Female mice are more sensitive to obesity‐induced vascular dysfunction than males (680.14)

Over the last two decades, a three fold increased in the prevalence of cardiovascular disease (CVD) has been reported in premenopausal women and attributed to the recent epidemic of obesity. While the mechanisms involved in obesity‐related CVD are beginning to be understood in males they remain unknown and unstudied in females. We tested the hypothesis that obesity negates the protection of women from CVD by submitting 6‐week old male and female Balb/C mice to a control (CD) or a high fat diet (HFD) for 12 weeks. On CD, females were smaller than males, but exhibited higher adiposity, fasted glycemia and leptin levels than males. On HFD, females had a higher food intake (HFDF: 3.1±0.5 vs. HFDM: 2.7±0.2g/day) but displayed lower increases in body weight (HFDF: +15% vs. HFDM: +35%), adiposity (HFDF: +12% vs. HFDM: +190%), glycemia and leptin levels than males, suggesting that female mice have a higher metabolic rate than males. Aortic ring reactivity was studied via wire myography at the end of the diet. Consistent with the human literature, at baseline, females displayed a better endothelial function than males (CDF: 82±3 vs. CDM: 49±3%, p<0.05). However 12 weeks of HFD impaired endothelial function (12% reduction in relaxation) and reduced the contractility of the aortic rings to phenylephrine (‐35%), serotonin (‐14%) and depolarization (‐13%), in female mice only, suggesting that females are more sensitive to obesity‐induced vascular dysfunction than males. While reduction in vascular contractility might initially protect females from hypertension, reduced endothelial function might predispose females to atherosclerosis and further cardiovascular events.Grant Funding Source: 11SDG5060006

The lifespan determinant p66shc drives obesity-induced oxidative stress, mitochondrial dysfunction and vascular inflammation

Purpose: Leptin deficiency in mice (LepOb/Ob) triggers high caloric intake leading to obesity/insulin resistance and activates several reactive oxygen species (ROS) generating pathways. Recent evidence suggest that mitochondrial adaptor p66Shc is a crucial player in ROS-mediated vascular damage. The present study investigates p66Shc role in obesity-driven vascular dysfunction. Methods: Three groups of male mice were studied (C57/B6, 4-6 months old, n=14 per group): 1) wild-type (WT), 2) leptin-deficient (p66Shc-LepOb/Ob), 3) double-mutant (p66Shc-/-/LepOb/Ob;). Plasma 8-iso-prostaglandin-F2α (8-iso-PGF2α was measured as a systemic marker of oxidative stress. mRNA and protein expression were assessed by real-time PCR and immunoblotting. ESR spectroscopy assessment of superoxide anion (O2-) levels and mitochondrial swelling were performed in mitochondria isolated from mouse aortas. The interaction between p66Shc and cytochrome c was investigated by pull-down assays. Organ chamber experiments were performed to assess endothelium-dependent relaxations to acetylcholine (Ach, 10-9-10-6 mol/L). NF-kB activity was determined as p65 nuclear translocation. Results: Plasma 8-iso-PGF2α as well as mitochondrial O2- levels were significantly higher in LepOb/Ob than WT. This increase was abolished in p66Shc-/-LepOb/Ob mice. Oxidative stress in LepOb/Ob mice was associated with p66Shc upregulation, mitochondrial translocation and swelling. Consistently, co-immunoprecipitation of p66Shc with cytochrome c and impaired Ach-induced relaxations were observed in the aortas of LepOb/Ob but not in WT mice. By contrast, in p66Shc-/-/LepOb/Ob mice endothelial dysfunction and mitochondrial swelling did not occur. In agreement with these findings, a preserved activation of Akt/eNOS pathway was observed. Genetic disruption of p66Shc in obese mice also prevented vascular activation of NF-kB signalling and upregulation of VCAM-.1, ICAM-1, IL-6, IL-8 and MCP-1 mRNAs. Conclusions: Our results suggest that p66Shc is critically involved in obesity-induced oxidative stress and vascular dysfunction. A better understanding of the molecular mechanism responsible for ROS production may provide a novel target to reduce cardiovascular health burden in this setting.