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Neurofibromatosis type 1 (NF1) is a heritable cancer predisposition syndrome resulting from mutations in the NF1 tumor suppressor gene. Genotype-phenotype correlations for NF1 are rare due to the large number of NF1 mutations and role of modifier genes in manifestations of NF1; however, emerging reports suggest that persons with NF1 display a distinct anthropometric and metabolic phenotype featuring short stature, low body mass index (BMI), increased insulin sensitivity, and protection from diabetes. Nf1 heterozygous (Nf1+/−) mice accurately reflect the dominant inheritance of NF1 and are regularly employed as a model of NF1. Here, we sought to identify whether Nf1+/− mice recapitulate the anthropometric and metabolic features identified in persons with NF1. Littermate 16–20 week-old male wildtype (WT) and Nf1+/− C57B/6J mice underwent nuclear magnetic resonance (NMR), indirect calorimetry, and glucose/insulin/pyruvate tolerance testing. In some experiments, tissues were harvested for NMR and histologic characterization. Nf1+/− mice are leaner with significantly reduced visceral and subcutaneous fat mass, which corresponds with an increased density of small adipocytes and reduced leptin levels. Additionally, Nf1+/− mice are highly reliant on carbohydrates as an energy substrate and display increased glucose clearance and insulin sensitivity, but normal response to pyruvate suggesting enhanced glucose utilization and preserved gluconeogenesis. Finally, WT and Nf1+/− mice subjected to high glucose diet were protected from diet-induced obesity and hyperglycemia. Our data suggest that Nf1+/− mice closely recapitulate the anthropometric and metabolic phenotype identified in persons with NF1, which will impact the interpretation of previous and future translational studies of NF1.

BACKGROUND AND PURPOSE Excess nutrient-induced endothelial cell inflammation is a hallmark in high fat diet (HFD)-induced metabolic syndrome. Pharmacological activation of protein kinase AMP-activated alpha 1(PRKAA1)/5'-Adenosine monophosphate-activated protein kinase alpha1 (AMPKα1) shows its beneficial effects in many studies of cardiometabolic disorders. However, AMPKα1, as a major cellular sensor of energy and nutrients in endothelial cells, has not been studied for its physiological role in excess nutrient-induced endothelial cell (EC) inflammation. EXPERIMENTAL APPROACH Wild-type and EC-specific Prkaa1 knockout mice were fed with an HFD. Body weight, fat mass composition, glucose and lipid levels were monitored regularly. Insulin sensitivity was analyzed systemically and in major metabolic organs/tissues. Inflammation status in metabolic organs/tissues were examined with quantitative RT-PCR and flow cytometry. Additionally, metabolic status, inflammation severity and signaling in cultured ECs were assayed with multiple approaches at the molecular level. KEY RESULTS EC Prkaa1 deficiency unexpectedly alleviated HFD-induced metabolic syndromes including decreased body weight and fat mass, enhanced glucose clearance and insulin sensitivity, and relieved adipose inflammation and hepatic steatosis. Mechanistically, PRKAA1 knockdown in cultured ECs reduced endothelial glycolysis and fatty acid oxidation, decreased the levels of acetyl-coA, and suppressed transcription of inflammatory molecules mediated by ATP citrate lyase (ACLY) and histone acetyltransferase p300. CONCLUSIONS AND IMPLICATIONS This unexpected pro-inflammatory effect of endothelial AMPKα1/PRKAA1 in metabolic context provides additional insight in AMPKα1/PRKAA1 activities, warranting that in-depth study and thoughtful consideration should be applied when AMPKα1/PRKAA1 is used as a therapeutic target in the treatment of metabolic syndrome.

People living with human immunodeficiency virus (HIV) (PLWH) have increased risk for atherosclerosis-related cardiovascular disease (CVD), the main cause of death in this population. Notwithstanding, the mechanisms of HIV-associated vascular pathogenesis are not fully elucidated. Therefore, we sought to determine whether HIV-regulatory protein Tat mediates HIV-induced endothelial dysfunction via NADPH oxidase 1 (Nox1)-dependent mechanisms. Body weight, fat mass, leptin levels, expression of reactive oxygen species (ROS)-producing enzymes and vascular function were assessed in C57BL/6 male mice treated with Tat for 3 days and 4 weeks. Aortic rings and human endothelial cells were also treated with Tat for 2–24 h in ex vivo and in vitro settings. Chronic (4 weeks) but not acute (3 days and 2–24 h) treatment with Tat decreased body weight, fat mass, and leptin levels and increased the expression of Nox1 and its coactivator NADPH oxidase Activator 1 (NoxA1). This was associated with impaired endothelium-dependent vasorelaxation. Importantly, specific inhibition of Nox1 with GKT771 and chronic leptin infusion restored endothelial function in Tat-treated mice. These data rule out direct effects of HIV-Tat on endothelial function and imply the contribution of reductions in adipose mass and leptin production which likely explain upregulated expression of Nox1 and NoxA1. The Nox1 and leptin system may provide potential targets to improve vascular function in HIV infection-associated CVD.

Placental ischemia, an initiating event of preeclampsia (PE), increases plasma leptin levels. We recently developed a model of midgestation (gestation day (GD)11-18) leptin infusion mimicking the midgestation rise in leptin levels of PE patients. Our previous work demonstrates that deletion of endothelial mineralocorticoid receptors (ECMR) improves markers of vascular dysfunction in leptin-infused female mice. We hypothesized vascular function improvement with ECMR deletion ablates hypertension and fetal growth restriction in pregnant leptin-infused mice. Pregnant ECMR +/+ (WT) and ECMR -/- (KO) mice were infused with vehicle or leptin by osmotic pump (lep, 0.9mg/kg/day, s.c.) on GD11-18 while implanted with radiotelemeters for conscious blood pressure (BP) measurement and wire myography of thoracic aorta and 2 nd order mesenteric arteries at GD18 (*=P

The adipokine leptin plays a crucial role in blood pressure (BP) regulation notably by exerting pressor effects centrally via sympatho-activation and depressor effects via direct activation of its receptor (LepR) peripherally resulting in nitric oxide (NO)-mediated vasodilation. However, the predominant effects and cell type responsible for leptin-mediated NO production is not clearly understood. Herein, we examined the effect of selective deletion of LepR in endothelial cells (LepR EC-/- , KO) on BP and vascular function. BP recording via radiotelemetry in male KO and WT (LepR EC+/+ ) mice revealed significant increases in diastolic and mean arterial pressure in KO mice (DBP, WT: 90.2±2.1 vs. KO: 100.1±3.6; MAP, WT: 105.7±2.1 vs. KO: 113.7±2.6 mmHg, n=5, pin vitro and impaired EDR in WT aortic rings ex vivo . Collectively, our data suggest that impaired endothelial leptin receptor signaling induces a PFKFB3-dependent hyper-glycolytic phenotype resulting in NO deficiency and endothelial dysfunction that predisposes to higher BP regardless the reduced sympatho-activation which might prevent the increase in BP induced by exogenous leptin.

Background Recent evidence by our laboratory demonstrates that women and female mice endogenously express higher endothelial mineralocorticoid receptor (ECMR) than males. Mounting clinical evidence also indicates that aldosterone production is higher in pathological conditions in females compared to males. However, the role for increased activation of ECMR by aldosterone in the absence of a comorbid condition is yet to be explored. The current study hypothesized that increased ECMR activation induced by elevated aldosterone production predisposes healthy female mice to endothelial dysfunction. Method Vascular reactivity was assessed in aortic rings from wild-type (WT) and ECMR KO (KO) mice fed either a normal salt (NSD, 0.4% NaCl) or sodium-restricted diet (SRD, 0.05% NaCl) for 28 days. Results SRD elevated plasma aldosterone levels as well as adrenal CYP11B2 and angiotensin II type 1 receptor (AT1R) expressions in female, but not male, WT mice. In baseline conditions (NSD), endothelial function, assessed by vascular relaxation to acetylcholine, was higher while vascular contractility to phenylephrine, serotonin, and KCl lower in female than male WT mice. SRD impaired endothelial function and increased vascular contractility in female, but not male, WT mice effectively ablating the baseline sex differences. NOS inhibition with LNAME ablated endothelial relaxation to a higher extent in male than female mice on NSD and ablated differences in acetylcholine relaxation responses between NSD- and SRD-fed females, indicating a role for NO in SRD-mediated endothelial function. In association, SRD significantly reduced vascular NOX4 expression in female, but not male, mice. Lastly, selective deletion of ECMR protected female mice from SRD-mediated endothelial dysfunction and increased vascular contractility. Conclusion Collectively, these data indicate that female mice develop aldosterone-induced endothelial dysfunction via endothelial MR-mediated reductions in NO bioavailability. In addition, these data support a role for ECMR to promote vascular contractility in female mice in response to sodium restriction.

Recent findings from our group demonstrated that females exhibit higher endothelial mineralocorticoid receptor (MR) expression than males, which predisposes them to aldosterone-mediated endothelial dysfunction in the context of metabolic disorders. However, whether the endothelium of female mice presents a higher propensity to MR-mediated dysfunction than that of males in the absence of comorbidities remains unknown. We therefore sought to investigate whether increasing aldosterone production endogenously with sodium restriction impairs endothelial function in otherwise healthy female mice. We fed male and female Balb/C mice a normal (0.4% NaCl; NSD) or sodium-restricted diet (0.05% NaCl; SRD) for 4 wk. Females exhibited higher baseline endothelial function (relaxation to acetylcholine) and lower vascular contractility (constriction to phenylephrine, serotonin, and KCl). However, SRD impaired endothelial-dependent relaxation and increased vascular contractility in female mice, effectively ablating the baseline sex difference. Female sex also increased baseline adrenal CYP11B2 expression; however, SRD significantly enhanced CYP11B2 expression in male and female mice and ablated the sex difference. Nitric oxide synthase (NOS) inhibition with N(ω)-nitro-l-arginine methyl ester hydrochloride eliminated both sex as well as diet-induced differences in endothelial dysfunction. In accordance, females demonstrated higher vascular endothelial NOS expression at baseline, which SRD significantly decreased. In addition, SRD diminished vascular NOX4 expression in female mice only. MR blockade with spironolactone-protected female mice from decreases in endothelial-dependent relaxation but not increases in vascular contractility. Utilizing sodium restriction as a method to increase plasma aldosterone levels in healthy female mice, we demonstrated that female mice are more susceptible to vascular damage via MR activation in the vascular endothelium only. NEW & NOTEWORTHY Female sex confers improved endothelial relaxation and vascular constriction responses in female Balb/C mice compared with males under baseline conditions. Sodium restriction impairs endothelial function, which is nitric oxide dependent, and increases vascular contractility in association with reduced vascular endothelial nitric oxide synthase and NOX4 expression in female mice ablating the baseline sex difference. Mineralocorticoid receptor antagonism ablates sodium restriction-induced endothelial dysfunction, but not increased vascular contractility, in female mice.

PURPOSE OF REVIEW: High dietary salt is a significant contributor to essential hypertension in clinical populations. However, although clinical studies indicate a higher prevalence of salt sensitivity in women over men, knowledge of salt-sensitive mechanisms is largely restricted to males, and female-specific mechanisms are presently being elucidated. RECENT FINDINGS: Male-specific mechanisms of salt-sensitive hypertension are well published and predominantly appear to involve dysfunctional renal physiology. However, emerging novel evidence indicates that aldosterone production is sex-specifically heightened in salt-sensitive hypertensive women and female rodent models, which may be regulated by intra-adrenal renin-angiotensin system activation and sex hormone receptors. In addition, new evidence that young females endogenously express higher levels of endothelial mineralocorticoid receptors (MRs) and that endothelial MR is a crucial mediator of endothelial dysfunction in females indicates that the aldosterone-endothelial MR activation pathway is a novel mediator of salt-sensitive hypertension. SUMMARY: Heightened aldosterone levels and endothelial MR expression provide a 2-fold sex-specific mechanism that may underlie the pathology of salt-sensitive hypertension in women. This hypothesis indicates that MR antagonists may be a preferential treatment for premenopausal women diagnosed with salt-sensitive hypertension.

Obesity increases preeclampsia (PE) risk. Plasma leptin levels increase with body weight in women with PE, and in addition, placental ischemia, an initiating event of PE, also increases plasma leptin. Our lab has shown that hyperleptinemia induces endothelial dysfunction and hypertension in female mice via endothelial mineralocorticoid receptor (ECMR) activation and that high progesterone levels of pregnancy increases ECMR expression. We hypothesized that leptin infusion induces PE-like endothelial dysfunction in pregnant mice, which is abrogated by ECMR deletion. Pregnant mice were infused with leptin by miniosmotic pump (0.9mg/kg/day, s.c.) on gestation day (GD) 11-18. Leptin decreased pup wt (0.86±0.04g ECMR +/+ vs 0.52±0.11 ECMR +/+ +leptin, *P+/+ vs 42±32 ECMR +/+ +leptin, P=0.09). ECMR deletion rescued pup weight (0.91±0.06g ECMR -/- vs 1.0±0.07 ECMR -/- +leptin) and protected fetal resorptions (2±2% ECMR -/- vs 0±0 ECMR -/- +leptin) in leptin-infused pregnant mice. In association, placental efficiency (pup/placenta ratio) decreased with leptin in ECMR +/+ (9.7±0.7 ECMR +/+ vs 7.9±0.6 ECMR +/+ +leptin, *P-/- (9.6±0.5 ECMR -/- vs 9.4±1.2 ECMR -/- +leptin) mice. Leptin infusion reduced endothelial function (acetylcholine-mediated relaxation) in aortas of ECMR +/+ , but not ECMR -/- , pregnant mice (2-way ANOVA, repeated measures, *P-/- +leptin mice was due to preserved NO bioavailability. No changes in endothelial-independent sodium nitroprusside or contractile responses to phenylephrine, serotonin or KCl were observed. ECMR deletion reduced aorta IL-1β mRNA (0.5±0.1-fold change ECMR +/+ +leptin vs 0.2±0.1-fold change ECMR -/- +leptin, P=0.06) levels and also placental growth factor mRNA (1.0±0.3-fold change ECMR +/+ +leptin vs 01.3±0.1 ECMR -/- +leptin, P=0.05) in placental tissues. Collectively, these data indicate that ECMR deletion protects pregnant mice from adverse fetal growth and demise in association with increasing NO vascular bioavailability, reducing vascular inflammation and improving placental function in a leptin-infused model of PE.

Our group has previously reported that lack of adipose tissue (lipodystrophy) leads to glucose intolerance and impaired endothelial-dependent vasorelaxation (EDR) via reduced signaling of the adipokine, leptin in the endothelium. However, the identity of the adipose depot responsible for endothelial leptin signaling activation and the underlying mechanism remains ill-defined. Our new data indicate that the perivascular adipose tissue (PVAT) is an important source of leptin. Thus, we hypothesized that leptin specifically derived from PVAT restores EDR and glucose tolerance in a mouse model with global deficiency in adipose tissue (lipodystrophic, BSCL2 -/- ). Restoration of PVAT in BSCL2 -/- mice corrected systemic glycemic status (GTT AUC, BSCL2 -/- + PVAT 635.3 ± 31.28 vs sham 741.6 ± 45.87, p-/- + PVAT 224.9 ± 23.97 vs 109 ± 19, P-/- + PVAT 143.8 ± 22.29 vs sham 131.3 ± 11.54, P-/- mice showed a trend towards an increase in PFKFB3 mRNA expression compared to WT mice. Moreover, we found that overexpression of PFKFB3 in aortic rings and endothelial cells impaired EDR and increased the ROS generating enzyme, Nox1 expression, respectively. Collectively, our results showed the critical role of PVAT-driven leptin and endothelial leptin receptor signaling in regulating systemic glucose disposal as well as endothelial function via a mechanism that potentially regulates endothelial glycolysis and oxidative stress-mediated via PFKFB3/NOX1.

Recent advances in the field of mineralocorticoid receptor (MR) and its ligand aldosterone expanded the role of this hormone and its receptor far beyond their initial function as a regulator of Na+ and K+ homeostasis in epithelial cells. The symposium “New Roles of Aldosterone and Mineralocorticoid Receptors in Cardiovascular Disease: Translational and Sex-Specific Effects” presented at the 38th World Congress of the International Union of Physiological Sciences (Rio de Janeiro, Brazil) highlighted the contribution of extrarenal MRs to cardiovascular disease. This symposium showcased how MRs expressed in endothelial, vascular smooth muscle, and immune cells plays a critical role in the development of vascular disease associated with aging, obesity, and chronic aldosterone stimulation and demonstrated that MR antagonism prevents the acute renal dysfunction and tubular injury induced by ischemia-reperfusion injury. It was also shown that the adipocyte-derived hormone leptin is a new direct regulator of aldosterone secretion and that leptin-mediated aldosterone production is a major contributor to obesity-associated hypertension in women. Sex differences in the role of aldosterone and of endothelial MR in the cardiovascular outcomes of obesity were highlighted. This review summarizes these important emerging concepts regarding the contribution of aldosterone and cell-specific MR to cardiovascular disease in male and female subjects and further supports sex-specific benefits of MR antagonist drugs to be tested in additional populations.

The adipokine leptin, which is best-known for its role in the control of metabolic function, is also a master regulator of cardiovascular function. While leptin has been approved for the treatment of metabolic disorders in patients with congenital generalized lipodystrophy (CGL), the effects of chronic leptin deficiency and the treatment on vascular contractility remain unknown. Herein, we investigated the effects of leptin deficiency and treatment (0.3 mg/day/7 days) on aortic contractility in male Berardinelli-Seip 2 gene deficient mice (gBscl2-/-, model of CGL) and their wild-type control (gBscl2+/+), as well as in mice with selective deficiency in endothelial leptin receptor (LepREC-/-). Lipodystrophy selectively increased vascular adrenergic contractility via NO-independent mechanisms and induced hypertrophic vascular remodeling. Leptin treatment and Nox1 inhibition blunted adrenergic hypercontractility in gBscl2-/- mice, however, leptin failed to rescue vascular media thickness. Selective deficiency in endothelial leptin receptor did not alter baseline adrenergic contractility but abolished leptin-mediated reduction in adrenergic contractility, supporting the contribution of endothelium-dependent mechanisms. These data reveal a new direct role for endothelial leptin receptors in the control of vascular contractility and homeostasis, and present leptin as a safe therapy for the treatment of vascular disease in CGL.

Rationale: Early vascular changes in metabolic disease that precipitate the development of cardiovascular complications are largely driven by reactive oxygen species accumulation, yet the extent to which excess reactive oxygen species derive from specific NADPH oxidase isoforms remains ill defined. Objective: Identify the role of Nox1 in the development of microvascular dysfunction in metabolic disease. Methods and Results: Four genotypes were generated by breeding Nox1 knockout mice with db/db mice: lean (H db W nox1 ), lean Nox1 knockout (H db K nox1 ), obese (K db W nox1 ), and obese KK (K db K nox1 ). The degree of adiposity, insulin resistance, and dyslipidemia in KW mice was not influenced by Nox1 deletion as determined by nuclear magnetic resonance spectroscopy, glucose tolerance tests, and plasma analyses. Endothelium-dependent responses to acetylcholine in pressurized mesenteric arteries were reduced in KW versus HW ( P P Conclusions: Nox1 deletion reduces oxidant load and restores microvascular health in db/db mice without influencing the degree of metabolic dysfunction. Therefore, targeted Nox1 inhibition may be effective in the prevention of vascular complications.

Leptin is the current treatment for metabolic disorders associated with acquired and congenital generalized lipodystrophy (CGL). Although excess leptin levels have been associated with vascular inflammation and cardiovascular disease in the context of obesity, the effects of chronic leptin treatment on vascular function remain unknown in CGL. Here, we hypothesized that leptin treatment will improve endothelial function via direct vascular mechanisms. We investigated the cardiovascular consequences of leptin deficiency and supplementation in male gBscl2 −/− ( Berardinelli-Seip 2 gene–deficient) mice—a mouse model of CGL. CGL mice exhibited reduced adipose mass and leptin levels, as well as impaired endothelium-dependent relaxation. Blood vessels from CGL mice had increased NADPH Oxidase 1 (Nox1) expression and reactive oxygen species production, and selective Nox1 inhibition restored endothelial function. Remarkably, chronic and acute leptin supplementation restored endothelial function via a PPARγ-dependent mechanism that decreased Nox1 expression and reactive oxygen species production. Selective ablation of leptin receptors in endothelial cells promoted endothelial dysfunction, which was restored by Nox1 inhibition. Lastly, we confirmed in aortic tissue from older patients undergoing cardiac bypass surgery that acute leptin can promote signaling in human blood vessels. In conclusion, in gBscl2 −/− mice, leptin restores endothelial function via peroxisome proliferator activated receptor gamma-dependent decreases in Nox1. Furthermore, we provide the first evidence that vessels from aged patients remain leptin sensitive. These data reveal a new direct role of leptin receptors in the control of vascular homeostasis and present leptin as a potential therapy for the treatment of vascular disease associated with low leptin levels.

Perivascular adipocytes residing in the vascular adventitia are recognized as distinct endocrine cells capable of responding to inflammatory stimuli and communicating with the sympathetic nervous system and adjacent blood vessel cells, thereby releasing adipocytokines and other signaling mediators to maintain vascular homeostasis. Perivascular adipocytes exhibit phenotypic heterogeneity (both white and brown adipocytes) and become dysfunctional in conditions, such as diet-induced obesity, thus promoting vascular inflammation, vasoconstriction, and smooth muscle cell proliferation to potentially contribute to the development of vascular diseases, such as atherosclerosis, hypertension, and aortic aneurysms. Although accumulating data have advanced our understanding of the role of perivascular adipocytes in modulating vascular function, their impact on vascular disease, particularly in humans, remains to be fully defined. This brief review will discuss the mechanisms whereby perivascular adipocytes regulate vascular disease, with a particular emphasis on recent findings and current limitations in the field of research.

PURPOSE OF REVIEW: To review the latest reports of the contributions of the endothelial mineralocorticoid receptor to endothelial dysfunction and hypertension to begin to determine the clinical potential for this pathway for hypertension treatment. RECENT FINDINGS: Endothelial mineralocorticoid receptor expression is sex-specifically increased in female mice and humans compared with males. Moreover, the expression of endothelial mineralocorticoid receptors is increased by endothelial progesterone receptor activation and naturally occurring fluctuations in progesterone levels (estrous, pregnancy) predict endothelial mineralocorticoid receptor expression levels in female mice. These data follow many previous reports that have indicated that endothelial mineralocorticoid receptor deletion is protective in the development of obesity- and diabetes-associated endothelial dysfunction in female mouse models. These studies have more recently been followed up by reports indicating that both intact endothelial mineralocorticoid receptor and progesterone receptor expression are required for obesity-associated, leptin-mediated endothelial dysfunction in female mice. In addition, the intra-endothelial signaling pathway for endothelial mineralocorticoid receptors to induce dysfunction requires the intact expression of α-epithelial sodium channels (αENaC) in endothelial cells in females. SUMMARY: Endothelial mineralocorticoid receptors are sex-specifically upregulated in the vasculature of females, a sex difference which is driven by endothelial progesterone receptor activation, and increased activity of these endothelial mineralocorticoid receptors is a crucial mediator of endothelial dysfunction, and potentially hypertension, in obese female experimental models.

Leptin which has been associated with cardiovascular disease in the context of obesity, is the current treatment for the metabolic disorders associated with congenital generalized lipodystrophy (CGL). However, the effects of chronic leptin infusion on vascular function and arterial pressure remain unknown in CGL. Here, we hypothesized that deletion in leptin will alter while leptin infusion will restore cardiovascular function via direct vascular mechanisms in CGL in male Berardinelli-Seip 2 gene deficient mice (gBscl2-/-), a mouse model of CGL. CGL mice exhibited reduced adipose mass and leptin levels (gBscl2+/+: 4.03 ± 0.3 vs gBscl2-/-: 0.38 ± 0.1*, ng/dL *P-5 M) or PPARγ activator (Pioglitazone 10 -5 M) restored endothelial function. Remarkably, chronic (0.3mg/day/7 days) and acute leptin supplementation restored endothelial function and decreased Nox1 expression and ROS production. Selective genetic ablation of leptin receptors in endothelial cells promoted endothelial dysfunction, via Nox-1 dependent mechanisms. Furthermore, leptin reduced vascular adrenergic contractility, but did not reduce MAP, nor PWV or vascular fibrosis in CGL. In conclusion, leptin restores endothelial function via PPARγ-dependent decreases in Nox1, reduces vascular adrenergic contractility, but does not affect the blood pressure and vascular structure, in gBscl2-/- mice. These data reveal a new direct role of leptin receptors in the control of vascular homeostasis and present leptin as a potential therapy for the treatment of vascular disease associated with low leptin levels.

Obesity is a risk factor for endothelial dysfunction and hypertension in pregnancy. Our lab has demonstrated that obesity-associated hypertension in female animal models develops via leptin-mediated, aldosterone-induced endothelial dysfunction (ED). We also showed that female mice are more sensitive to leptin-induced aldosterone activation of endothelial mineralocorticoid receptors (ECMR) due to an endogenous sex-specific upregulation of ECMR in females. Our previous data demonstrates that endothelial progesterone receptor activation increases ECMR expression and that ECMR deletion protects female mice from obesity-associated, leptin-mediated ED. However, whether ECMR play a role in ED in pregnancy is unknown. Therefore, we hypothesized that high progesterone levels increase ECMR expression in pregnant mice and that ECMR deletion protects pregnant mice from obesity-associated, leptin-mediated ED. Endothelial cells were isolated from aorta of timed-pregnant Balb/C mice (gestation day (GD) 17) and assessed for ECMR expression via RT-PCR. ECMR mRNA expression increased 9.2±0.2-fold (*P

Compelling clinical evidence indicates that obesity and its associated metabolic abnormalities supersede the protective effects of female sex-hormones and predisposes premenopausal women to cardiovascular disease. The underlying mechanisms remain poorly defined; however, recent studies have implicated overactivation of the aldosterone-mineralocorticoid receptor (MR) axis as a cause of sex-specific cardiovascular risk in obese females. Experimental evidence indicates that the MR on endothelial cells contributes to obesity-associated, leptin-induced endothelial dysfunction in female experimental models, however, the vascular-specific mechanisms via which females are predisposed to heightened endothelial MR activation remain unknown. Therefore, we hypothesized that endogenous expression of endothelial MR is higher in females than males which predisposes them to obesity-associated, leptin-mediated endothelial dysfunction. We found that endothelial MR expression is higher in blood vessels from female mice and humans compared to those of males, and further, that progesterone receptor activation in endothelial cells is the driving mechanism for sex-dependent increases in endothelial MR expression in females. In addition, we show that genetic deletion of either the endothelial MR or progesterone receptor in female mice prevents leptin-induced endothelial dysfunction, providing direct evidence that interaction between the progesterone receptor and MR mediates obesity-associated endothelial impairment in females. Collectively, these novel findings suggest that progesterone drives sex-differences in endothelial MR expression and predisposes female mice to leptin-induced endothelial dysfunction, which indicates that MR antagonists may be a promising sex-specific therapy to reduce the risk of cardiovascular diseases in obese premenopausal women.

The prominence of obesity in the clinical population as well as the strong association of cardiovascular risk factors with obesity has prompted the investigation of the adipose tissue and its physiological contribution to cardiovascular health. A notable finding in these investigations was the discovery of the adipocyte-derived hormone leptin. Leptin is secreted from the adipose tissue, increases in linear fashion in the circulation with increased body mass and is implicated in the development of cardiovascular disease in obesity, notably via pro-hypertensive mechanisms. Leptin stimulates the activation of the sympathetic nervous system in male patients and mice, which has been implicated as the pro-hypertensive pathway for leptin in obesity. However, obese premenopausal females do not exhibit increased sympathetic activation in response to hyperleptinemia in obesity, indicating a sex-discrepancy in mechanisms of obesity-associated hypertension. Our lab recently demonstrated that leptin also induces the adrenal production of aldosterone in a direct fashion and that this pathway leads to the hyperaldosteronemia that is characteristic of obesity. We have also published data that indicate that the implications of leptin-induced aldosterone are of particular impact in obese females. Leptin-mediated hypertension and endothelial dysfunction, a significant predictor of hypertension clinically, require activation of the mineralocorticoid receptor in female mice. The clinical potential of this pathway remains under investigation; however, existing data indicate that a sex discrepancy exists in mechanisms of leptin-mediated hypertension between males and females and that leptin-stimulated aldosterone plays a significant role in females.

Protein tyrosine phosphatase 1b (Ptp1b) is a negative regulator of leptin and insulin-signalling pathways. Its targeted deletion in proopiomelanocortin (POMC) neurons protects mice from obesity and diabetes by increasing energy expenditure. Inflammation accompanies increased energy expenditure. Therefore, the present study aimed to determine whether POMC-Ptp1b deletion increases energy expenditure via an inflammatory process, which would impair endothelial function. We characterized the metabolic and cardiovascular phenotypes of Ptp1b+/+ and POMC-Ptp1b−/− mice. Clamp studies revealed that POMC-Ptp1b deletion reduced body fat and increased energy expenditure as evidenced by a decrease in feed efficiency and an increase in oxygen consumption and respiratory exchange ratio. POMC-Ptp1b deletion induced a 2.5-fold increase in plasma tumour necrosis factor α (TNF-α) levels and elevated body temperature. Vascular studies revealed an endothelial dysfunction in POMC-Ptp1b−/− mice. Nitric oxide synthase inhibition [N-nitro-L-arginine methyl ester (L-NAME)] reduced relaxation to a similar extent in Ptp1b+/+ and POMC-Ptp1b−/− mice. POMC-Ptp1b deletion decreased ROS-scavenging enzymes [superoxide dismutases (SODs)] whereas it increased ROS-generating enzymes [NADPH oxidases (NOXs)] and cyclooxygenase-2 (COX-1) expression, in aorta. ROS scavenging or NADPH oxidase inhibition only partially improved relaxation whereas COX-2 inhibition and thromboxane-A2 (TXA2) antagonism fully restored relaxation in POMC-Ptp1b−/− mice. Chronic treatment with the soluble TNF-α receptor etanercept decreased body temperature, restored endothelial function and reestablished aortic COX-2, NOXs and SOD expression to their baseline levels in POMC-Ptp1b−/− mice. However, etanercept promoted body weight gain and decreased energy expenditure in POMC-Ptp1b−/− mice. POMC-Ptp1b deletion increases plasma TNF-α levels, which contribute to body weight regulation via increased energy expenditure and impair endothelial function via COX-2 and ROS-dependent mechanisms.

Clinical studies indicate that salt-sensitive hypertension is more prevalent in women than in men. However, animal models of salt sensitivity have primarily focused on the mechanisms of salt sensitivity in male animals; therefore, elucidation of these mechanisms in female animal models is needed. We have previously shown that female Balb/C mice have higher aldosterone synthase expression and aldosterone production than males. We hypothesized that female Balb/C mice develop salt-sensitive increases in blood pressure. Seven-day feeding of a 4% NaCl high-salt (HS) diet increased blood pressure in female mice without altering blood pressure in males. Females on an HS diet displayed no apparent increases in sodium retention as assessed by 24-hour urine collection, sodium balance measure, and saline loading excretion analysis. Females on an HS diet exhibited lower renin-angiotensin system activity (plasma Ang II [angiotensin II], plasma renin activity, and ACE [angiotensin-converting enzyme] activity) compared with males but developed a salt-induced elevation in adrenal aldosterone synthase expression and retained higher aldosterone levels than males on HS. This resulted in a higher aldosterone/plasma renin activity ratio in females compared with males on HS feeding. Adrenal mRNA expression of angiotensinogen and leptin receptor was increased in female mice on an HS diet. HS impaired endothelium-dependent relaxation in female mice only. MR (mineralocorticoid receptor) inhibition (eplerenone) restored blood pressure and endothelial function in females on an HS diet. Collectively, these data indicate that Balb/C mice develop sex-discrepant salt-sensitive hypertension likely via aldosterone-MR–mediated mechanisms involving impaired endothelium-dependent relaxation in females only. This study presents the first model of spontaneous sex-specific salt sensitivity, which mimics the human pathology.

Perivascular adipose tissue (PVAT) surrounds the arterial adventitia and plays an important role in vascular homeostasis. PVAT expands in obesity, and inflamed PVAT can locally promote endothelial dysfunction and atherosclerosis. Here, using adipose tissue transplantation, we tested the hypothesis that expansion of PVAT can also remotely exacerbate vascular disease. Fifty milligrams of abdominal aortic PVAT was isolated from high-fat diet (HFD)-fed wild-type mice and transplanted onto the abdominal aorta of lean LDL receptor knockout mice. Subcutaneous and visceral adipose tissues were used as controls. After HFD feeding for 10 weeks, body weight, glucose/insulin sensitivity, and lipid levels were measured. Adipocytokine gene expression was assessed in the transplanted adipose tissues, and the thoracic aorta was harvested to quantify atherosclerotic lesions by Oil-Red O staining and to assess vasorelaxation by wire myography. PVAT transplantation did not influence body weight, fat composition, lipid levels, or glucose/insulin sensitivity. However, as compared with controls, transplantation of PVAT onto the abdominal aorta increased thoracic aortic atherosclerosis. Furthermore, PVAT transplantation onto the abdominal aorta inhibited endothelium-dependent relaxation in the thoracic aorta. MCP-1 and TNF-α expression was elevated, while adiponectin expression was reduced, in the transplanted PVAT tissue, suggesting augmented inflammation as a potential mechanism for the remote vascular effects of transplanted PVAT. These data suggest that PVAT expansion and inflammation in obesity can remotely induce endothelial dysfunction and augment atherosclerosis. Identifying the underlying mechanisms may lead to novel approaches for risk assessment and treatment of obesity-related vascular disease.

Compelling evidence indicates a higher efficacy of mineralocorticoid receptor (MR) blockade for the treatment of cardiovascular disease in females with obesity and diabetes than in males, however, the origin of this sex-specific effect is unknown. We have shown that leptin induces endothelial dysfunction in obese female mice via aldosterone-dependent activation of MR and that only female mice develop endothelial dysfunction (vasorelaxation to acetylcholine) in response to aldosterone ex vivo . Therefore, we hypothesized that females express higher endothelial MR (ECMR) expression than males which predisposes females to obesity-associated endothelial dysfunction. RT-PCR analysis in isolated aortic endothelial cells of Balb/C mice revealed a higher NR3C2 (MR gene) expression in females compared to males (2.9±0.5-fold from male, Pin vitro (P

Background— In obesity, the excessive synthesis of aldosterone contributes to the development and progression of metabolic and cardiovascular dysfunctions. Obesity-induced hyperaldosteronism is independent of the known regulators of aldosterone secretion, but reliant on unidentified adipocyte-derived factors. We hypothesized that the adipokine leptin is a direct regulator of aldosterone synthase ( CYP11B2 ) expression and aldosterone release and promotes cardiovascular dysfunction via aldosterone-dependent mechanisms. Methods and Results— Immunostaining of human adrenal cross-sections and adrenocortical cells revealed that adrenocortical cells coexpress CYP11B2 and leptin receptors. Measurements of adrenal CYP11B2 expression and plasma aldosterone levels showed that increases in endogenous (obesity) or exogenous (infusion) leptin dose-dependently raised CYP11B2 expression and aldosterone without elevating plasma angiotensin II, potassium or corticosterone. Neither angiotensin II receptors blockade nor α and β adrenergic receptors inhibition blunted leptin-induced aldosterone secretion. Identical results were obtained in cultured adrenocortical cells. Enhanced leptin signaling elevated CYP11B2 expression and plasma aldosterone, whereas deficiency in leptin or leptin receptors blunted obesity-induced increases in CYP11B2 and aldosterone, ruling out a role for obesity per se. Leptin increased intracellular calcium, elevated calmodulin and calmodulin-kinase II expression, whereas calcium chelation blunted leptin-mediated increases in CYP11B2 , in adrenocortical cells. Mineralocorticoid receptor blockade blunted leptin-induced endothelial dysfunction and increases in cardiac fibrotic markers. Conclusions— Leptin is a newly described regulator of aldosterone synthesis that acts directly on adrenal glomerulosa cells to increase CYP11B2 expression and enhance aldosterone production via calcium-dependent mechanisms. Furthermore, leptin-mediated aldosterone secretion contributes to cardiovascular disease by promoting endothelial dysfunction and the expression of profibrotic markers in the heart.

Although it has been known for some time that increases in body mass enhance aldosterone secretion, particularly in women, the origin of this elevation in aldosterone production is not well defined. Adipocyte-derived factors have emerged as potential candidates to increase aldosterone production in obesity.Emerging evidence suggests the presence of a mechanistic link in which the adipocyte-derived hormone leptin stimulates aldosterone production in obesity, thereby creating a positive feedback loop for obesity-associated cardiovascular disease. In addition, recent reports give credence to the concept that this leptin-aldosterone stimulation pathway in obesity is an underlying mechanism for sex-discrepancies in obesity-associated cardiovascular disease.Leptin appears as a new direct regulator of adrenal aldosterone production and leptin-mediated aldosterone production is a novel candidate mechanism underlying obesity-associated hypertension, particularly in females.

Obesity is on a fast track to become the most costly and burdensome health epidemic worldwide. Comorbidities associated with obesity include type II diabetes mellitus and cardiovascular disease (CVD), of which hypertension is a highly prevalent and significant risk factor. Rising hypertension rates in both men and women are closely correlated with, and largely attributable to, rising rates of obesity.1,2 Currently, ≤70% of essential hypertension cases are associated with obesity.1 Understanding the mechanisms that lead to obesity-associated hypertension is vital to treat this growing patient population. However, there is a significant deficit of reports examining sex differences in obesity-associated hypertension in the literature to date because research efforts have been overwhelmingly restricted to male animals, and many clinical reports fail to separate results by sex. The National Institutes of Health, American Heart Association, and others have begun to raise awareness of sex discrepancies in research, and as a result, there has been an increase in publications highlighting differences in mechanisms associated with obesity-associated hypertension in females versus males. This review will summarize current knowledge of (1) epidemiological data of sex discrepancies in obesity-associated hypertension, (2) the sex specificity of the effects of obesity on sympathoactivation and its role in hypertension, (3) the potential role of leptin in sex differences in obesity-associated hypertension, (4) the influence of female sex hormones on leptin and obesity-associated hypertension, and (5) sex differences in renin–angiotensin–aldosterone system activation in obesity. Population rates of obesity are not equal between men and women. Data from the NHANES study (National Health and Nutrition Examination Survey),3–5 REGARDS study (Reasons for Geographic and Racial Differences in Stroke),6 and Jackson Heart Study7 demonstrate that women have a higher obesity rate than men. Worldwide, the prevalence of obesity in women is higher than men …

Obesity-related cardiovascular disease (CVD) involves increased sympathetic activity in men and male animals. Although women exhibit increased visceral fat, metabolic disorders, inflammation and CVD with obesity, whether body weight gain affects autonomic control of cardiovascular function in females remain unknown. Due to the lack of adequate model to mimic the human pathology, this study aimed to develop a murine model, which would allow studying the sex-specificity of the response of the autonomic nervous system to obesity and identifying the origin of potential sex-differences. We tested the hypothesis that sexual dimorphisms in the autonomic response to obesity disappear in mice matched for changes in body weight, metabolic and inflammatory disorders. Male and female C57Bl/6 mice were submitted to control (CD) or high fat diet (HFD) for 24 weeks. Female mice gained more adipose mass and lost more lean mass than males but reached similar visceral adipose mass and body weight, as males, at the end of the diet. 24 weeks of HFD matched male and female mice for visceral adiposity, glycaemia, plasma insulin, lipids, and inflammatory cytokines levels, demonstrating the suitability of the model to study human pathology. HFD did not elevate BP, but similarly increased heart rate (HR) in males (CD: 571 ± 9 vs. HFD: 631 ± 14 bpm, P < 0.05) and females (CD: 589 ± 19 vs. HFD: 642 ± 6 bpm, P < 0.05). Indices of autonomic control of BP and HR were obtained by measuring BP and HR response to ganglionic blockade, β-adrenergic, and muscarinic receptors antagonists. HFD increased vascular but reduced cardiac sympathetic drive in males (CD: –43 ± 4 and HFD: –60 ± 7% drop in BP, P < 0.05). HFD did not alter females' vascular or cardiac sympathetic drive. HFD specifically reduced aortic α-adrenergic constriction in males and lowered HR response to muscarinic receptor antagonism in females. These data suggest that obesity-associated increases in HR could be caused by a reduced cardiac vagal tone in females, while HR increases in males may compensate for the reduced vascular adrenergic contractility to preserve baseline BP. These data suggest that obesity impairs autonomic control of cardiovascular function in males and females, via sex-specific mechanisms and independent of fat distribution, metabolic disorder or inflammation.

Leptin, the adipocyte-derived hormone identified in 1994 for its major role in the control of satiety and body weight regulation, is an adipokine secreted in a sex-specific manner. Although it has clearly been established that females secrete three to four times more leptin than males and that this sexual dimorphism in leptin secretion is exacerbated with overweight and obesity, the origin and the physiological consequences of this sexual dimorphism remain ill-defined. The adipose tissue is the major site of leptin secretion; however, leptin receptors are ubiquitously expressed, conferring to leptin, and indirectly to the adipose tissue, a potential role in the control of numerous physiological functions. Besides its major role in the control of food intake and energy expenditure, leptin has been shown to contribute to the control of immune, bone, reproductive, and cardiovascular functions. The goal of the present chapter is to review and discuss the current knowledge on the contribution of leptin to the control of cardiovascular function while focusing on the impact of the sexual dimorphism in leptin secretion and of the pathological increases in leptin levels induced by overweight and obesity.

Peroxynitrite (ONOO−) contributes to coronary microvascular dysfunction in diabetes mellitus (DM). We hypothesized that in DM, ONOO− interferes with the function of coronary endothelial caveolae, which plays an important role in nitric oxide (NO)-dependent vasomotor regulation. Flow-mediated dilation (FMD) of coronary arterioles was investigated in DM (n = 41) and non-DM (n = 37) patients undergoing heart surgery. NO-mediated coronary FMD was significantly reduced in DM patients, which was restored by ONOO− scavenger, iron-(III)-tetrakis(N-methyl-4'pyridyl)porphyrin-pentachloride, or uric acid, whereas exogenous ONOO− reduced FMD in non-DM subjects. Immunoelectron microscopy demonstrated an increased 3-nitrotyrosine formation (ONOO−-specific protein nitration) in endothelial plasma membrane in DM, which colocalized with caveolin-1 (Cav-1), the key structural protein of caveolae. The membrane-localized Cav-1 was significantly reduced in DM and also in high glucose–exposed coronary endothelial cells. We also found that DM patients exhibited a decreased number of endothelial caveolae, whereas exogenous ONOO− reduced caveolae number. Correspondingly, pharmacological (methyl-β-cyclodextrin) or genetic disruption of caveolae (Cav-1 knockout mice) abolished coronary FMD, which was rescued by sepiapterin, the stable precursor of NO synthase (NOS) cofactor, tetrahydrobiopterin. Sepiapterin also restored coronary FMD in DM patients. Thus, we propose that ONOO− selectively targets and disrupts endothelial caveolae, which contributes to NOS uncoupling, and, hence, reduced NO-mediated coronary vasodilation in DM patients.

Recent studies by our group demonstrated that leptin is a direct regulator of aldosterone secretion and increases blood pressure via sex-specific mechanisms involving leptin-mediated activation of the aldosterone-mineralocorticoid receptor signaling pathway in females and sympatho-activation in males. Although it is well accepted that females secrete more leptin and aldosterone than males, it is unknown whether leptin infusion raises blood pressure similarly in male and female mice and whether higher aldosterone levels sensitize females to salt-induced hypertension. We hypothesized that female mice would be more sensitive to leptin than males and also have a potentiated blood pressure rise in response to high salt diet compared to males. Male and female Balb/C mice were implanted with radiotelemeters for continuous measurement of mean arterial pressure (MAP) at 10 weeks of age. MAP was measured for seven days prior to feeding with a high-salt diet (HS, 4%NaCl) for seven days. Following a recovery period, animals were then implanted with osmotic minipumps containing leptin (0.9mg/kg/day) recorded for seven days. Baseline MAP was similar between males and females (101.3±2.9 vs 99.3±3.7 mmHg, n=4 and 5, respectively), however, HS diet resulted in a greater MAP increase in females (15.0±2.6 mmHg) compared to males (3.1±4.5 mmHg, P

Angiotensin II has a key role in the control of resistance artery tone and local blood flow. Angiotensin II possesses 2 main receptors. Although angiotensin II type 1 receptor is well known and is involved in the vasoconstrictor and growth properties of angiotensin II, the role of the angiotensin II type 2 receptor (AT2R) remains much less understood. Although AT2R stimulation induces vasodilatation in normotensive rats, it induces vasoconstriction in pathological conditions involving oxidative stress and cyclooxygenase 2 expression. Thus, we studied the influence of cyclooxygenase 2 on AT2R-dependent tone in diabetes mellitus. Mesenteric resistance arteries were isolated from Zucker diabetic fatty (ZDF) and lean Zucker rats and studied using in vitro using wire myography. In ZDF rats, AT2R-induced dilation was lower than in lean rats (11% versus 21% dilation). Dilation in ZDF rats returned to the control (lean rats) level after acute superoxide reduction (Tempol and apocynin), cyclooxygenase 2 inhibition (NS398), or thromboxane A 2 synthesis inhibition (furegrelate). Cyclooxygenase 2 expression and superoxide production were significantly increased in ZDF rat arteries compared with arteries of lean rats. After chronic treatment with Tempol, AT2R-dependent dilation was equivalent in ZDF and lean rats. Chronic treatment of ZDF rats with NS398 also restored AT2R-dependent dilation to the control (lean rats) level. Plasma thromboxane B 2 (thromboxane A 2 metabolite), initially high in ZDF rats, was decreased by chronic Tempol and by chronic NS398 to the level found in lean Zucker rats. Thus, in type 2 diabetic rats, superoxide and thromboxane A 2 reduced AT2R-induced dilation. These findings are important to take into consideration when choosing vasoactive drugs for diabetic patients.

Obesity is a major risk factor for cardiovascular disease in males and females. Whether obesity triggers cardiovascular disease via similar mechanisms in both the sexes is, however, unknown. In males, the adipokine leptin highly contributes to obesity-related cardiovascular disease by increasing sympathetic activity. Females secrete 3× to 4× more leptin than males, but do not exhibit high sympathetic tone with obesity. Nevertheless, females show inappropriately high aldosterone levels that positively correlate with adiposity and blood pressure (BP). We hypothesized that leptin induces hypertension and endothelial dysfunction via aldosterone-dependent mechanisms in females. Leptin control of the cardiovascular function was analyzed in female mice sensitized to leptin via the deletion of protein tyrosine phosphatase 1b (knockout) and in agouti yellow obese hyperleptinemic mice (Ay). Hypersensitivity to leptin (wild-type, 115±2; protein tyrosine phosphatase 1b knockout, 124±2 mm Hg; P P

Obesity is a major risk factor for hypertension. The copresentation of hypertension and insulin resistance (IR) suggests a role for IR in blood pressure (BP) dysregulation. To test this hypothesis, peripheral IR has been genetically subtracted in a model of obesity by crossing leptin receptor mutant mice (K db H PTP ) with mice lacking protein tyrosine phosphatase 1B (insulin desensitizer, H db K PTP ) to generate obese insulin-sensitive mice (K db K PTP ). BP was recorded in lean (H db H PTP , H db K PTP ) and obese (K db H PTP , K db K PTP ) mice via telemetry, and a frequency analysis of the recording was performed to determine BP variability. Correction of IR in obese mice normalized BP values to baseline levels (H db H PTP : 116±2 mm Hg; K db H PTP : 129±4 mm Hg; K db K PTP : 114±5 mm Hg) and restored BP variability by decreasing its standard deviation and the frequency of BP values over the upper autoregulatory limit of the kidneys. However, although IR-induced increases in proteinuria (versus 53±13 μg/d, H db H PTP ) were corrected in K db K PTP (112±39 versus 422±159 μg/d, K db H PTP ), glomerular hypertrophy was not. IR reduced plasma aldosterone levels ruling out a role for mineralocorticoids in the development of hypertension. Taken together, these data indicate that correction of IR prevents hypertension, BP variability, and microalbuminuria in obese mice. Although the mechanism remains to be fully determined, increases in aldosterone or sympathoactivation of the cardiovascular system seem to be less likely contributors.

Diseases of the coronary circulation remain the leading cause of death in Western society despite impressive advances in diagnosis, pharmacotherapy and post-event management. Part of this statistic likely stems from a parallel increase in the prevalence of obesity and metabolic dysfunction, both significant risk factors for coronary disease. Obesity and diabetes pose unique challenges for the heart and their impact on the coronary vasculature remains incompletely understood. The vascular endothelium is a major interface between arterial function and the physical and chemical components of blood flow. Proper function of the endothelium is necessary to preserve hemostasis, maintain vascular tone and limit the extent of vascular diseases such as atherosclerosis. Given its central role in vascular health, endothelial dysfunction has been the source of considerable research interest in diabetes and obesity. In the current review, we will examine the pathologic impact of obesity and diabetes on coronary function and the extent to which these two factors impact endothelial function. This article is part of a Special Issue entitled “Coronary Blood Flow”.

Background— Obesity causes hypertension and sympathoactivation, a process proposed to be mediated by leptin. Protein tyrosine phosphatase 1B (PTP1B), a major new pharmaceutical target in the treatment of obesity and type II diabetes mellitus, constrains the metabolic actions of leptin, but the extent to which PTP1B regulates its cardiovascular effects is unclear. This study examined the hypothesis that PTP1B is a negative regulator of the cardiovascular effects of leptin. Methods and Results— PTP1B knockout mice had lower body fat but higher mean arterial pressure (116±5 versus 105±5 mm Hg, P P P P 1 -adrenergic receptor subtypes, consistent with blunted constriction to phenylephrine. Conclusions— These data indicate that PTP1B is a key regulator of the cardiovascular effects of leptin and that reduced vascular adrenergic reactivity provides a compensatory limit to the effects of leptin on mean arterial pressure.

Impairment of vascular growth is a hallmark of diabetic complications, but the progression and mechanisms are poorly understood. To determine whether obesity and early diabetes impair endothelium-dependent vasodilatation and vascular response to ischemia, microvascular function as well as angiogenic responses to ischemia were assessed in young (C57) and 6-month-old lean mice (old C57), in obese (db-C57) mice, and in mice suffering an early (db-KsJ) and sustained type 2 diabetes (old db-KsJ). Glycemia gradually increased from the db-C57 to the old db-KsJ. Early and established type II diabetes significantly reduced the level of insulin that was significantly increased in obese mice. Endothelial function was assessed in isolated resistance arteries while the angiogenic response induced by unilateral hindlimb ischemia was analyzed, after 28 days, with a laser Doppler flowmeter and angiography. Aging (-21%), obesity (-45%), as well as early (-58%) and sustained type II diabetes (-69%) induced a progressive impairment of the endothelium-dependent relaxation of the gracilis artery. Laser Doppler measurements demonstrated that only early and sustained type II diabetes impaired skin blood flow recovery. Vascular collateralization was reduced with aging and severely impaired in older db-KsJ mice, the two strains of mice in which ischemia reduced eNOS expression. These results demonstrate that endothelial dysfunction induced by obesity is insufficient to alter the angiogenic response to ischemia. Furthermore, the development of frank type II diabetes or increasing age is required to impair the vascular response to hindlimb ischemia. We conclude that additional risk factors or severe endothelial dysfunction may be requisite to impede the angiogenic response to ischemia.

Obesity is an emerging epidemic worldwide and threatens cardiovascular health due to the complications of accompanying metabolic dysfunction. One potential mechanism by which these complications are advanced is structural alteration in the microcirculation perfusing target organs. In this brief review, the authors focus on the structural adaptations that occur in the microcirculation, with specific focus on changes in basement membrane thickness and vascular structure. By delineating changes in end-stage disease and recent insights from animal studies, they hope to convince the reader (1) that diabetic disease in the limb is associated with profound changes in arteriolar structure and (2) that parallel changes in microvascular architecture precede the onset of frank type II diabetes.