Fat intake modifies vascular responsiveness and receptor expression of vasoconstrictors: implications for diet-induced obesity

Impact of Highly Saturated versus Unsaturated Fat Intake on Carbohydrate Metabolism and Vascular Reactivity in Rat

Palm olein (PO) and lard are considered harmful to health because of their highly saturated fatty acid content. On the contrary, olive oil (OO) with its high level of polyunsaturated fatty acids is considered healthier. This study aims to evaluate the effects of high consumption of these oils on carbohydrate metabolism and vascular function. Male Wistar rats were fed ad libitum for 12 weeks with different high fat diets (HFD) containing 30% of each oil. Systemic glycemia, insulinemia, and lipidemia were assessed by routine methods or by ELISA. GLUT4 muscular expression and hepatic and muscular Akt phosphorylation were analyzed by western blot. Vascular function was evaluated, ex vivo, on aortic rings and on the variations of isometric tensions. The results show that fasting blood glucose was increased with PO and OO diets and decreased with lard. Compared to control diet, this increase was significant only with PO diet. The area under the curve of IPGTT was increased in all HFD groups. Compared to control diet, this increase was significant only with PO. In contrast, stimulation of the pathway with insulin showed a significant decrease in Akt phosphorylation in all HFD compared to control diet. KCl and phenylephrine induced strong, dose-dependent vasoconstriction of rat aortas in all groups, but KCl EC₅₀ values were increased with lard and OO diets. The inhibitory effect of tempol was absent in PO and lard and attenuated in OO. Vascular insulin sensitivity was decreased in all HFD groups. This decreased sensitivity of insulin was more important with PO and lard when compared to OO diet. In conclusion, the results of this study clearly show that high consumption of palm olein, olive oil, and lard can compromise glucose tolerance and thus insulin sensitivity. Furthermore, palm olein and lard have a more deleterious effect than olive oil on the contractile function of the aorta. Excessive consumption of saturated or unsaturated fatty acids is harmful to health, regardless of their vegetable or animal origin.

The impact of maternal high-fat diet on offspring neurodevelopment

A maternal high-fat diet affects offspring neurodevelopment with long-term consequences on their brain health and behavior. During the past three decades, obesity has rapidly increased in the whole human population worldwide, including women of reproductive age. It is known that maternal obesity caused by a high-fat diet may lead to neurodevelopmental disorders in their offspring, such as autism spectrum disorder, attention deficit hyperactivity disorder, anxiety, depression, and schizophrenia. A maternal high-fat diet can affect offspring neurodevelopment due to inflammatory activation of the maternal gut, adipose tissue, and placenta, mirrored by increased levels of pro-inflammatory cytokines in both maternal and fetal circulation. Furthermore, a maternal high fat diet causes gut microbial dysbiosis further contributing to increased inflammatory milieu during pregnancy and lactation, thus disturbing both prenatal and postnatal neurodevelopment of the offspring. In addition, global molecular and cellular changes in the offspring's brain may occur due to epigenetic modifications including the downregulation of brain-derived neurotrophic factor (BDNF) expression and the activation of the endocannabinoid system. These neurodevelopmental aberrations are reflected in behavioral deficits observed in animals, corresponding to behavioral phenotypes of certain neurodevelopmental disorders in humans. Here we reviewed recent findings from rodent models and from human studies to reveal potential mechanisms by which a maternal high-fat diet interferes with the neurodevelopment of the offspring.

Endothelin-1-mediated miR-let-7g-5p triggers interlukin-6 and TNF-α to cause myopathy and chronic adipose inflammation in elderly patients with diabetes mellitus

Background: Diabetes and sarcopenia are verified as mutual relationships, which seriously affect the quality of life of the elderly. Endothelin-1 is well investigated, is elevated in patients with diabetes, and is related to muscle cellular senescence and fibrosis. However, the mechanism of ET-1 between diabetes and myopathy is still unclear. The aim of this study was to evaluate the prevalence of sarcopenia in the elderly with diabetes and to clarify its relationship with ET-1 molecular biological mechanism, progress as well as changes in muscle and fat.

Methods: We recruited 157 type 2 diabetes patients over 55 years old and investigated the prevalence of sarcopenia in diabetes patients and examined the association of ET-1 alterations with HbA1c, creatinine, or AMS/ht2. Next, sought to determine how ET-1 regulates inflammation in muscle cells by western blot and qPCR assay. Using XF Seahorse Technology, we directly quantified mitochondrial bioenergetics in 3T3-L1 cells.

Results: ET-1 was positively correlated with HbA1c, creatinine levels, and duration of disease, and negatively correlated with AMS/ht2. We found that ET-1 dose-dependently induces tumor necrosis factor-α (TNF-α) and interleukin (IL)-6β expression through the PI3K/AKT, and NF-κB signaling pathways in C2C12 cells. Also identified that TNF-α, IL-6β, and visfatin releases were found in co-cultured with conditioned medium of ET-1/C2C12 in 3T3-L1 cells. ET-1 also reduces the energy metabolism of fat and induces micro-environment inflammation which causes myopathy. ET-1 also suppresses miR-let-7g-5p expression in myocytes and adipocytes.

Conclusion: We describe a new mechanism of ET-1 triggering chronic inflammation in patients with hyperglycemia.

Repeated glucose spikes and insulin resistance synergistically deteriorate endothelial function and bardoxolone methyl ameliorates endothelial dysfunction

Background

Both insulin resistance and postprandial glucose spikes are known for their potential to induce vascular endothelial dysfunction in individuals with metabolic syndrome. However, these factors are inextricable, and therefore, their relative contributions to inducing endothelial dysfunction remain elusive. In this study, we aimed to disentangle the effects of these factors and clarify whether bardoxolone methyl (CDDO-Me), a novel nuclear factor erythroid 2-related factor 2 (Nrf2) activator, protects against glucose spike-induced endothelial dysfunction.

Methods

We induced glucose spikes twice daily for a duration of 1 week to rats fed a standard/control diet (CD) and Western-type diet (WTD). Endothelium-dependent relaxation (EDR) was evaluated using isolated thoracic aortas. Gene expression and dihydroethidium (DHE)-fluorescence studies were carried out; the effect of CDDO-Me on aortic endothelial dysfunction in vivo was also evaluated.

Results

Neither WTD-induced insulin resistance nor pure glucose spikes significantly deteriorated EDR. However, under high-glucose (20 mM) conditions, the EDR of thoracic aortas of WTD-fed rats subjected to glucose spikes was significantly impaired. In this group of rats, we observed significantly enhanced DHE fluorescence as a marker of reactive oxygen species, upregulation of an oxidative stress-related gene (NOX2), and downregulation of an antioxidant gene (SOD2) in the thoracic aortas. As expected, treatment of the thoracic aorta of this group of rats with antioxidant agents significantly improved EDR. We also noted that pretreatment of aortas from the same group with CDDO-Me attenuated endothelial dysfunction, accompanied by a correction of the redox imbalance, as observed in gene expression and DHE fluorescence studies.

Conclusions

For the first time, we showed that insulin resistance and glucose spikes exert a synergistic effect on aortic endothelial dysfunction. Furthermore, our study reveals that CDDO-Me ameliorates endothelial dysfunction caused by glucose spikes in a rat model of metabolic syndrome.

Postprandial vascular-inflammatory and thrombotic responses to high-fat feeding are augmented by manipulating the lipid droplet size distribution

BACKGROUND AND AIMS

Postprandial responses are influenced not only by the type and amount of fat ingested, but also lipid droplet size distribution. However, little research has investigated the impact of differential lipid size distributions within a mixed-macronutrient meal context on postprandial vascular health. Therefore, we examined whether manipulating the lipid droplet size distribution within a mixed-macronutrient meal impacts vascular-inflammatory and thrombotic parameters.

METHODS AND RESULTS

In a randomised and counterbalanced fashion, sixteen adults (8 males; age 34 ± 7 years; BMI of 25.3 ± 4.5 kg/m²) completed three separate fasted morning-time feeding challenges, each separated by a minimum washout of 7-days. On each occasion, test-meals matched for carbohydrate and protein content differing only in fat amount and the lipid droplet size distribution were administered, such that participants consumed (1) a low-fat meal (LF) with negligible fat content, (2) an emulsified-high-fat meal with a fine lipid droplet size (FE), or (3) an emulsified-high-fat meal with a coarse lipid droplet size (CE). Periodic blood samples were retrospectively analysed for plasma triglycerides, tumour necrosis factor alpha (TNFα), tissue factor (TF), fibrinogen, and plasminogen activator inhibitor-1 (PAI-1). Triglyceride concentrations increased rapidly overtime under FE (P-time<0.05); this rise was attenuated under CE (P-time>0.05) and was comparable to LF (P-condition>0.05). Similarly, FE induced a significant rise in TNFα, TF, fibrinogen, and PAI-1 (P-time<0.05); these parameters remained unchanged under LF and CE (P-time>0.05).

CONCLUSION

A high-fat mixed-macronutrient meal with a larger lipid droplet size distribution ameliorates the associated rise in vascular-inflammatory and thrombotic parameters.

TRIAL REGISTRATION

ISRCTN88881254.

N,N-Dimethlyacetamide Prevents the High-Fat Diet-Induced Increase in Body Weight

Increased body weight caused by visceral fat accumulation is on the rise and is reaching epidemic proportions worldwide. Hence, means and ways to tackle the problem of increased adiposity is of utmost importance. In this work, we report the effect of a water-soluble small molecule N,N-Dimethlyacetamide (DMA) on weight gain and adiposity in vitro and in vivo. To monitor the in vitro effect of DMA on adipogenesis, 3T3-L1 preadipocytes and pluripotent C2C12 cells were differentiated to adipocytes in the presence of DMA (5 mM and 10 mM). Oil red O staining and reverse transcriptase polymerase chain reaction (RT-PCR) were performed to evaluate the differentiation to adipocytes. To study the in vivo effect of DMA on body weight, experiments were done with C57BL/6J male mice (6 weeks old). The mice were randomly assigned to receive either high-fat diet (HFD; 45% fat) or a normal diet (7% fat) and were either intraperitoneally injected with DMA or phosphate-buffered saline (PBS) once a week for 20 weeks. Glucose tolerance test was performed on living mice. Post-experiment, the epididymal and subcutaneous adipose tissue were excised from the sacrificed animal, and histology, RT-PCR and plasma triglyceride assay were performed. DMA had no inhibitory effect on adipocyte differentiation when applied only once. However, sustained treatment with DMA inhibited the adipocyte differentiation in both 3T3-L1 and C2C12 cells, and significantly lowered the expression of adipocyte markers, in particular, fatty acid-binding protein 4 (fabp4). Under HFD, C57BL/6J mice treated with DMA had lower body weight compared with PBS treatment. Moreover, the HFD-induced higher body weight was controlled when the mice were switched from PBS to DMA treatment. Further, the HFD-mediated adipocyte hypertrophy from epididymal and subcutaneous adipose tissue was significantly reduced with DMA treatment. Interestingly, the glucose clearance and triglyceride levels in the plasma were improved in mice when DMA treatment was initiated early. Taken together, our results show that DMA exhibits a clear potential to prevent weight gain and restricts adiposity in response to high-fat feeding.

High-Fat Diet-Induced Obesity Model Does Not Promote Endothelial Dysfunction via Increasing Leptin/Akt/eNOS Signaling

Experimental studies show that the unsaturated high-fat diet-induced obesity promotes vascular alterations characterized by improving the endothelial L-arginine/Nitric Oxide (NO) pathway. Leptin seems to be involved in this process, promoting vasodilation via increasing NO bioavailability. The aim of this study was to test the hypothesis that unsaturated high-fat diet-induced obesity does not generate endothelial dysfunction via increasing the vascular leptin/Akt/eNOS signaling. Thirty-day-old male Wistar rats were randomized into two groups: control (C) and obese (Ob). Group C was fed a standard diet, while group Ob was fed an unsaturated high-fat diet for 27 weeks. Adiposity, hormonal and biochemical parameters, and systolic blood pressure were observed. Concentration response curves were performed for leptin or acetylcholine in the presence or absence of Akt and NOS inhibitor. Our results showed that an unsaturated high-fat diet promoted a greater feed efficiency (FE), elevation of body weight and body fat (BF), and an adiposity index, characterizing a model of obesity. However, comorbidities frequently associated with experimental obesity were not visualized, such as glucose intolerance, dyslipidemia and hypertension. The evaluation of the endothelium-dependent relaxation with acetylcholine showed no differences between the C and Ob rats. After NOS inhibition, the response was completely abolished in the Ob group, but not in the C group. Furthermore, Akt inhibition completely blunted vascular relaxation in the C group, but not in the Ob group, which was more sensitive to leptin-induced vascular relaxation. L-NAME incubation abolished the relaxation in both groups at the same level. Although Akt inhibitor pre-incubation reduced the leptin response, group C was more sensitive to its effect. In conclusion, the high-unsaturated fat diet-induced obesity improved the vascular reactivity to leptin and does not generate endothelial dysfunction, possibly by the increase in the vascular sensitivity to leptin and increasing NO bioavailability. Moreover, our results suggest that the increase in NO production occurs through the increase in NOS activation by leptin and is partially mediated by the Akt pathway.

Impact of high-fat diet on vasoconstrictor reactivity of white and brown adipose tissue resistance arteries

Blood flow regulation is a critical factor for tissue oxygenation and substrate supply. Increased reactivity of arteries to vasoconstrictors may increase vascular resistance, resulting in reduced blood flow. We aimed to investigate the effect of a high-fat (HF) diet on stiffness and vasoconstrictor reactivity of white adipose tissue (WAT) and brown adipose tissue (BAT) resistance arteries and also investigated the interconversion of both adipose depots in the setting of a HF diet. Vasoconstrictor reactivity and passive morphology and mechanical properties of arteries from B6D2F1 mice (5 mo old) fed normal chow (NC) or a HF diet (8 wk) were measured using pressure myography. Receptor gene expression in WAT and BAT arteries and markers of WAT and BAT were assessed in whole tissue lysates by real-time RT-PCR. Despite greater receptor-independent vasoconstriction (in response to KCl, P < 0.01), vasoconstriction in response to angiotensin II ( P < 0.01) was lower in NC-BAT than NC-WAT arteries and similar in response to endothelin-1 ( P = 0.07) and norepinephrine ( P = 0.11) in NC-BAT and NC-WAT arteries. With the exception of BAT artery reactivity to endothelin-1 and angiotensin II, the HF diet tended to attenuate reactivity in arteries from both adipose depots and increased expression of adipose markers in BAT. No significant differences in morphology or passive mechanical properties were found between adipose types or diet conditions. Alterations in gene expression of adipose markers after the HF diet suggest beiging of BAT. An increase in brown adipocytes in the absence of increased BAT mass may be a compensatory mechanism to dissipate excess energy from a HF diet. NEW & NOTEWORTHY Despite no differences in passive mechanical properties and greater receptor-independent vasoconstriction, receptor-mediated vasoconstriction was either lower in brown than white adipose tissue arteries or similar in brown and white adipose tissue arteries. A high-fat diet has a greater impact on vasoconstrictor responses in white adipose tissue but leads to altered adipose tissue gene expression consistent with beiging of the brown adipose tissue.

Multispecies Probiotic Supplementation Favorably Affects Vascular Function and Reduces Arterial Stiffness in Obese Postmenopausal Women-A 12-Week Placebo-Controlled and Randomized Clinical Study

Obesity in the postmenopausal period is associated with an increased risk of cardiovascular diseases in women. One of the key drivers of cardiovascular risk is endothelial dysfunction; thus, this is also a crucial point for studies on new therapeutic methods of cardioprotective properties. The aim of the current study was to evaluate the effect of two doses of multispecies probiotic Ecologic® Barrier supplement on functional (primary endpoint) and biochemical parameters (secondary endpoint) of endothelial dysfunction in obese postmenopausal women in a 12-week randomized, placebo-controlled clinical trial. A total of 81 obese Caucasian women participated in the trial. The subjects were randomly assigned to three groups that received a placebo, a low dose (LD) (2.5 × 10⁸ colony forming units (CFU) per day), or a high dose (HD) (1 × 1010 CFU per day) of lyophilisate powder containing live multispecies probiotic bacteria. The probiotic supplement was administered each day for 12 weeks in two equal portions. A high dose probiotic supplementation for 12 weeks decreased systolic blood pressure, vascular endothelial growth factor, pulse wave analysis systolic pressure, pulse wave analysis pulse pressure, pulse wave analysis augmentation index, pulse wave velocity, interleukin-6, tumor necrosis factor alpha, and thrombomodulin. Low doses of probiotic supplementation decreased the systolic blood pressure and interleukin-6 levels. The mean changes in the estimated parameters, compared among the three groups, revealed significant differences in the vascular endothelial growth factor, the pulse wave analysis systolic pressure, the pulse wave analysis augmentation index, the pulse wave velocity, the tumor necrosis factor alpha, and thrombomodulin. The post hoc tests showed significant differences for all parameters between HD and the placebo group, and HD and LD (besides pulse wave analysis augmentation index). We show for the first time that supplementation with multispecies probiotic Ecologic® Barrier favorably modifies both functional and biochemical markers of vascular dysfunction in obese postmenopausal women.

Pulmonary vascular dysfunction in metabolic syndrome

Metabolic syndrome is a critically important precursor to the onset of many diseases, such as cardiovascular disease, and cardiovascular disease is the leading cause of death worldwide. The primary risk factors of metabolic syndrome include hyperglycaemia, abdominal obesity, dyslipidaemia, and high blood pressure. It has been well documented that metabolic syndrome alters vascular endothelial and smooth muscle cell functions in the heart, brain, kidney and peripheral vessels. However, there is less information available regarding how metabolic syndrome can affect pulmonary vascular function and ultimately increase an individual's risk of developing various pulmonary vascular diseases, such as pulmonary hypertension. Here, we review in detail how metabolic syndrome affects pulmonary vascular function.

Endothelin-1 differentially directs lineage specification of adipose- and bone marrow-derived mesenchymal stem cells

Blood vessels composed of endothelial cells (ECs) contact with mesenchymal stem cells (MSCs) in different tissues, suggesting possible interaction between these 2 types of cells. We hypothesized that endothelin-1 (ET1), a secreted paracrine factor of ECs, can differentially direct the lineages of adipose-derived stem cells (ASCs) and bone marrow-derived MSCs (BMSCs). Predifferentiated ASCs and BMSCs were treated with ET1 for 2 cell passages and then induced for multilineage differentiation. Our results showed that adipogenesis of ET1-pretreated ASCs and osteogenesis of ET1-pretreated BMSCs were increased compared to those of control cells. The effect of ET1 on enhancing adipogenesis of ASCs and osteogenesis of BMSCs was attenuated by blocking endothelin receptor type A (ETAR) and/or endothelin receptor type B (ETBR). Western blot analysis indicated that regulation by ET1 was mediated through activation of the protein kinase B and ERK1/2 signaling pathways. We analyzed subpopulations of ASCs and BMSCs with or without ETAR and/or ETBR, and we found that ETAR⁺/ETBR^- and ETAR^-/ETBR⁺ subpopulations of ASCs and those of BMSCs pretreated with ET1 were prone to turning into adipocytes and osteoblasts, respectively, after differentiation induction. Our findings provide insight into the differential regulation of MSC specification by ET1, which may help develop viable approaches for tissue regeneration.-Lee, M.-S., Wang, J., Yuan, H., Jiao, H., Tsai, T.-L., Squire, M. W., Li, W.-J. Endothelin-1 differentially directs lineage specification of adipose- and bone marrow-derived mesenchymal stem cells.

The triterpenoid alpha, beta-amyrin prevents the impaired aortic vascular reactivity in high-fat diet-induced obese mice

To characterize the protective effects of the triterpenoid mixture alpha, beta-amyrin (AMY, 20 mg/kg, during 15 days) on the reactivity of isolated aorta of high-fat diet (HFD)-induced obese mice. Male Swiss mice were fed with HFD or normal diet (ND) for 15 weeks. Contractions of thoracic aorta in response to KCl or phenylephrine (PHE) and relaxation by acetylcholine (ACh) or sodium nitroprusside (SNP) were analyzed. HFD-fed mice developed hyperglycemia, hyperlipidemia, and significant body weight gain, parameters prevented by AMY treatment. Whereas aortic contractility did not differ in response to KCl, contractions induced by PHE (1 μM) as well as relaxation induced by ACh (1-30 μM) or SNP (1 nM-0.1 mM) on PHE-contracted aorta were decreased (p < 0.05) in tissues of HFD compared to ND mice, phenomenon significantly (p < 0.05) diminished in HFD mice treated with AMY. The relaxant actions of ACh and SNP were inhibited (p < 0.05) by tetraethylammonium (TEA, 5 mM), apamin (0.1 μM), and 4-aminopyridine (4-AP; 3 mM) in aortae from ND group, but not from HFD. Treatment of HFD mice with AMY rescued the inhibitory effect of TEA (p < 0.05) on vasorelaxant actions of ACh and SNP. 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) inhibited similarly the relaxant effects of SNP in all groups. 8-Br-cGMP relaxed with similar profile aortae of all groups. By preventing HFD-induced obesity in mice, AMY rescued the blunted contractile response to PHE, and the attenuated vasorelaxation and K⁺ channel activation (opening) induced by ACh and SNP in isolated aorta.

Endothelial dysfunction and vascular disease - a 30th anniversary update

The endothelium can evoke relaxations of the underlying vascular smooth muscle, by releasing vasodilator substances. The best-characterized endothelium-derived relaxing factor (EDRF) is nitric oxide (NO) which activates soluble guanylyl cyclase in the vascular smooth muscle cells, with the production of cyclic guanosine monophosphate (cGMP) initiating relaxation. The endothelial cells also evoke hyperpolarization of the cell membrane of vascular smooth muscle (endothelium-dependent hyperpolarizations, EDH-mediated responses). As regards the latter, hydrogen peroxide (H₂ O₂ ) now appears to play a dominant role. Endothelium-dependent relaxations involve both pertussis toxin-sensitive G_i (e.g. responses to α₂ -adrenergic agonists, serotonin, and thrombin) and pertussis toxin-insensitive G_q (e.g. adenosine diphosphate and bradykinin) coupling proteins. New stimulators (e.g. insulin, adiponectin) of the release of EDRFs have emerged. In recent years, evidence has also accumulated, confirming that the release of NO by the endothelial cell can chronically be upregulated (e.g. by oestrogens, exercise and dietary factors) and downregulated (e.g. oxidative stress, smoking, pollution and oxidized low-density lipoproteins) and that it is reduced with ageing and in the course of vascular disease (e.g. diabetes and hypertension). Arteries covered with regenerated endothelium (e.g. following angioplasty) selectively lose the pertussis toxin-sensitive pathway for NO release which favours vasospasm, thrombosis, penetration of macrophages, cellular growth and the inflammatory reaction leading to atherosclerosis. In addition to the release of NO (and EDH, in particular those due to H₂ O₂ ), endothelial cells also can evoke contraction of the underlying vascular smooth muscle cells by releasing endothelium-derived contracting factors. Recent evidence confirms that most endothelium-dependent acute increases in contractile force are due to the formation of vasoconstrictor prostanoids (endoperoxides and prostacyclin) which activate TP receptors of the vascular smooth muscle cells and that prostacyclin plays a key role in such responses. Endothelium-dependent contractions are exacerbated when the production of nitric oxide is impaired (e.g. by oxidative stress, ageing, spontaneous hypertension and diabetes). They contribute to the blunting of endothelium-dependent vasodilatations in aged subjects and essential hypertensive and diabetic patients. In addition, recent data confirm that the release of endothelin-1 can contribute to endothelial dysfunction and that the peptide appears to be an important contributor to vascular dysfunction. Finally, it has become clear that nitric oxide itself, under certain conditions (e.g. hypoxia), can cause biased activation of soluble guanylyl cyclase leading to the production of cyclic inosine monophosphate (cIMP) rather than cGMP and hence causes contraction rather than relaxation of the underlying vascular smooth muscle.

Icariin improves eNOS/NO pathway to prohibit the atherogenesis of apolipoprotein E-null mice

Impaired endothelial nitric oxide synthase (eNOS)/nitric oxide (NO) pathway induces atherogenesis. The present study examined whether icariin improves the eNOS/NO pathway to prohibit the atherogenesis of apolipoprotein E-null (ApoE^-/-) mice. In vitro, primary human umbilical vein endothelial cells (HUVECs) were randomly divided into 7 groups: control; vehicle; icariin 10; lyphosphatidylcholine (LPC) group; LPC + icariin 1; LPC + icariin 3; and LPC + icariin 10. In vivo, 80 mice were separated randomly into 4 groups (n = 20): control, ApoE^-/-, ApoE^-/- + icariin 10, and ApoE^-/- + icariin 30. ApoE^-/- mice had significantly more atherosclerosis in the aortic root together with increased aortic ROS production, body mass, plasma triglyceride (TG) and total cholesterol (TC) concentration, decreased aortic eNOS expression, and plasma NO concentration. LPC (10 μg/mL) treatment induced a big decline in NO level in the conditioned medium and eNOS expression, and an increase in intracellular reactive oxygen species (ROS) production in HUVECs. Icariin treatment decreased atherogenesis, ROS production, body mass, plasma TG concentration, and plasma TC concentration, and increased NO concentration and eNOS expression. These findings suggested icariin could improve eNOS/NO-pathway to prohibit the atherogenesis of apolipoprotein E-null mice by restraining oxidative stress.

Obesity, type 2 diabetes, and impaired insulin-stimulated blood flow: role of skeletal muscle NO synthase and endothelin-1

Increased endothelin-1 (ET-1) and reduced endothelial nitric oxide phosphorylation (peNOS) are hypothesized to reduce insulin-stimulated blood flow in type 2 diabetes (T2D), but studies examining these links in humans are limited. We sought to assess basal and insulin-stimulated endothelial signaling proteins (ET-1 and peNOS) in skeletal muscle from T2D patients. Ten obese T2D [glucose disposal rate (GDR): 6.6 ± 1.6 mg·kg lean body mass (LBM)^-1·min^-1] and 11 lean insulin-sensitive subjects (Lean GDR: 12.9 ± 1.2 mg·kg LBM^-1·min^-1) underwent a hyperinsulinemic-euglycemic clamp with vastus lateralis biopsies taken before and 60 min into the clamp. Basal biopsies were also taken in 11 medication-naïve, obese, non-T2D subjects. ET-1, peNOS (Ser1177), and eNOS protein and mRNA were measured from skeletal muscle samples containing native microvessels. Femoral artery blood flow was assessed by duplex Doppler ultrasound. Insulin-stimulated blood flow was reduced in obese T2D (Lean: +50.7 ± 6.5% baseline, T2D: +20.8 ± 5.2% baseline, P < 0.05). peNOS/eNOS content was higher in Lean under basal conditions and, although not increased by insulin, remained higher in Lean during the insulin clamp than in obese T2D (P < 0.05). ET-1 mRNA and peptide were 2.25 ± 0.50- and 1.52 ± 0.11-fold higher in obese T2D compared with Lean at baseline, and ET-1 peptide remained 2.02 ± 1.9-fold elevated in obese T2D after insulin infusion (P < 0.05) but did not increase with insulin in either group (P > 0.05). Obese non-T2D subjects tended to also display elevated basal ET-1 (P = 0.06). In summary, higher basal skeletal muscle expression of ET-1 and reduced peNOS/eNOS may contribute to a reduced insulin-stimulated leg blood flow response in obese T2D patients.

NEW & NOTEWORTHY

Although impairments in endothelial signaling are hypothesized to reduce insulin-stimulated blood flow in type 2 diabetes (T2D), human studies examining these links are limited. We provide the first measures of nitric oxide synthase and endothelin-1 expression from skeletal muscle tissue containing native microvessels in individuals with and without T2D before and during insulin stimulation. Higher basal skeletal muscle expression of endothelin-1 and reduced endothelial nitric oxide phosphorylation (peNOS)/eNOS may contribute to reduced insulin-stimulated blood flow in obese T2D patients.

Endothelin-1 contributes to endothelial dysfunction and enhanced vasoconstriction through augmented superoxide production in penile arteries from insulin-resistant obese rats: role of ET(A) and ET(B) receptors

BACKGROUND AND PURPOSE

We assessed whether endothelin-1 (ET-1) inhibits NO and contributes to endothelial dysfunction in penile arteries in a model of insulin resistance-associated erectile dysfunction (ED).

EXPERIMENTAL APPROACH

Vascular function was assessed in penile arteries, from obese (OZR) and lean (LZR) Zucker rats, mounted in microvascular myographs. Changes in basal and stimulated levels of superoxide (O2 (-) ) were detected by lucigenin-enhanced chemiluminescence and ET receptor expression was determined by immunohistochemistry.

KEY RESULTS

ET-1 stimulated acute O2 (-) production that was blunted by tempol and the NADPH oxidase inhibitor, apocynin, but markedly enhanced in obese animals. ET-1 inhibited the vasorelaxant effects of ACh and of the NO donor S-nitroso-N-acetyl-DL-penicillamine in arteries from both LZR and OZR. Selective ETA (BQ123) or ETB receptor (BQ788) antagonists reduced both basal and ET-1-stimulated superoxide generation and reversed ET-1-induced inhibition of NO-mediated relaxations in OZR, while only BQ-123 antagonized ET-1 actions in LZR. ET-1-induced vasoconstriction was markedly enhanced by NO synthase blockade and reduced by endothelium removal and apocynin. In endothelium-denuded penile arteries, apocynin blunted augmented ET-1-induced contractions in OZR. Both ETA and ETB receptors were expressed in smooth muscle and the endothelial layer and up-regulated in arteries from OZR.

CONCLUSIONS AND IMPLICATIONS

ET-1 stimulates ETA -mediated NADPH oxidase-dependent ROS generation, which inhibits endothelial NO bioavailability and contributes to ET-1-induced contraction in healthy penile arteries. Enhanced vascular expression of ETB receptors contributes to augmented ROS production, endothelial dysfunction and increased vasoconstriction in erectile tissue from insulin-resistant obese rats. Hence, antagonism of ETB receptors might improve the ED associated with insulin-resistant states.

Role of nitric oxide synthases in early blood-brain barrier disruption following transient focal cerebral ischemia

The role of nitric oxide synthases (NOSs) in early blood-brain barrier (BBB) disruption was determined using a new mouse model of transient focal cerebral ischemia. Ischemia was induced by ligating the middle cerebral artery (MCA) at its M2 segment and reperfusion was induced by releasing the ligation. The diameter alteration of the MCA, arterial anastomoses and collateral arteries were imaged and measured in real time. BBB disruption was assessed by Evans Blue (EB) and sodium fluorescein (Na-F) extravasation at 3 hours of reperfusion. The reperfusion produced an extensive vasodilation and a sustained hyperemia. Although expression of NOSs was not altered at 3 hours of reperfusion, L-NAME (a non-specific NOS inhibitor) abolished reperfusion-induced vasodilation/hyperemia and significantly reduced EB and Na-F extravasation. L-NIO (an endothelial NOS (eNOS) inhibitor) significantly attenuated cerebral vasodilation but not BBB disruption, whereas L-NPA and 7-NI (neuronal NOS (nNOS) inhibitors) significantly reduced BBB disruption but not cerebral vasodilation. In contrast, aminoguanidine (AG) (an inducible NOS (iNOS) inhibitor) had less effect on either cerebral vasodilation or BBB disruption. On the other hand, papaverine (PV) not only increased the vasodilation/hyperemia but also significantly reduced BBB disruption. Combined treatment with L-NAME and PV preserved the vasodilation/hyperemia and significantly reduced BBB disruption. Our findings suggest that nNOS may play a major role in early BBB disruption following transient focal cerebral ischemia via a hyperemia-independent mechanism.

Obesity and heterozygous endothelial overexpression of prepro-endothelin-1 modulate responsiveness of mouse main and segmental renal arteries to vasoconstrictor agents

AIMS

Levels of the endothelium-derived peptide endothelin-1 (ET-1) are elevated in obese humans, and ET-1 mediated vascular tone is increased. Renal arterial smooth muscle is highly responsive to ET-1. Whether or not endothelium-derived ET-1 affects contractions of the renal artery under normal conditions or in obesity is unknown. The present study was designed to investigate whether or not overexpression of endogenous ET-1 in the endothelium affects the responsiveness of the main and segmental renal arteries differently in obesity.

MAIN METHODS

Mice with tie-1 promoter-driven endothelium-restricted heterozygous overexpression of preproendothelin-1 were used (TET(het)). Obesity was induced in TET(het) mice and wild-type (WT) littermates by feeding a high fat diet for 30 weeks; lean controls were kept on standard chow. The renal arteries were studied in wire myographs testing contractions (in the presence of l-NAME) to ET-1, serotonin, and U46619.

KEY FINDINGS

Contractions to ET-1 were comparable between groups in main renal arteries, but augmented in segmental preparations from obese mice. Serotonin-induced responses were enhanced in obese TET(het) mice renal arteries compared to lean controls. Concentration-contraction curves to U46619 were shifted significantly to the left in main renal arteries of obese animals, and the maximal response was significantly increased between lean and obese TET(het) mice.

SIGNIFICANCE

These results indicate an augmented responsiveness of main renal arteries in obesity particularly to TP receptor activation. When combined with endothelial ET-1 overexpression this effect is even more pronounced, which may help to gain further insights into the mechanisms of hypertension in obesity.

Effects of the green tea polyphenol epigallocatechin-3-gallate on high-fat diet-induced insulin resistance and endothelial dysfunction

Insulin resistance, a hallmark of metabolic disorders, is a risk factor for diabetes and cardiovascular disease. Impairment of insulin responsiveness in vascular endothelium contributes to insulin resistance. The reciprocal relationship between insulin resistance and endothelial dysfunction augments the pathophysiology of metabolism and cardiovascular functions. The most abundant green tea polyphenol, epigallocatechin-3-gallate (EGCG), has been shown to have vasodilator action in vessels by activation of endothelial nitric oxide synthase (eNOS). However, it is not known whether EGCG has a beneficial effect in high-fat diet (HFD)-induced endothelial dysfunction. Male C57BL/6J mice were fed either a normal chow diet (NCD) or HFD with or without EGCG supplement (50 mg·kg(-1)·day(-1)) for 10 wk. Mice fed a HFD with EGCG supplement gained less body weight and showed improved insulin sensitivity. In vehicle-treated HFD mice, endothelial function was impaired in response to insulin but not to acetylcholine, whereas the EGCG-treated HFD group showed improved insulin-stimulated vasodilation. Interestingly, EGCG intake reduced macrophage infiltration into aortic tissues in HFD mice. Treatment with EGCG restored the insulin-stimulated phosphorylation of eNOS, insulin receptor substrate-1 (IRS-1), and protein kinase B (Akt), which was inhibited by palmitate (200 μM, 5 h) in primary bovine aortic endothelial cells. From these results, we conclude that supplementation of EGCG improves glucose tolerance, insulin sensitivity, and endothelial function. The results suggest that EGCG may have beneficial health effects in glucose metabolism and endothelial function through modulating HFD-induced inflammatory response.

Western-style diet modulates contractile responses to phenylephrine differently in mesenteric arteries from senescence-accelerated prone (SAMP8) and resistant (SAMR1) mice

The influence of two known cardiovascular risk factors, aging and consumption of a high-fat diet, on vascular mesenteric artery reactivity was examined in a mouse model of accelerated senescence (SAM). Five-month-old SAM prone (SAMP8) and resistant (SAMR1) female mice were fed a Western-type high-fat diet (WD; 8 weeks). Mesenteric arteries were dissected, and vascular reactivity, protein and messenger RNA expression, superoxide anion (O 2 (·-) ) and hydrogen peroxide formation were evaluated by wire myography, immunofluorescence, RT-qPCR, ethidium fluorescence and ferric-xylenol orange, respectively. Contraction to KCl and relaxation to acetylcholine remained unchanged irrespective of senescence and diet. Although similar contractions to phenylephrine were observed in SAMR1 and SAMP8, accelerated senescence was associated with decreased eNOS and nNOS and increased O 2 (·-) synthesis. Senescence-related alterations were compensated, at least partly, by the contribution of NO derived from iNOS and the enhanced endogenous antioxidant capacity of superoxide dismutase 1 to maintain vasoconstriction. Administration of a WD induced qualitatively different alterations in phenylephrine contractions of mesenteric arteries from SAMR1 and SAMP8. SAMR1 showed increased contractions partly as a result of decreased NO availability generated by decreased eNOS and nNOS and enhanced O 2 (·-) formation. In contrast, WD feeding in SAMP8 resulted in reduced contractions due to, at least in part, the increased functional participation of iNOS-derived NO. In conclusion, senescence-dependent intrinsic alterations during early stages of vascular senescence may promote vascular adaptation and predispose to further changes in response to high-fat intake, which may lead to the progression of aging-related cardiovascular disease, whereas young subjects lack the capacity for this adaptation.

The flavonoid luteolin induces nitric oxide production and arterial relaxation

PURPOSE

Luteolin, a flavone present in many foods and medicinal plants, may have beneficial effects on various human chronic diseases. In the present study, we investigated the hypothesis that luteolin can directly act on vascular endothelial cells (ECs), leading to nitric oxide (NO) production and subsequent vascular relaxation.

METHODS

Rat aortic rings were mounted in organ bath. Luteolin was added cumulatively, and vessel relaxation of rat aortic rings precontracted with phenylephrine (PE) or potassium was recorded. Endothelial nitric oxide synthase (eNOS) phosphorylation at Ser1177 and NO production from aortic rings and primary human aortic endothelial cells (HAECs) exposed to luteolin were measured by using Western blot and fluorometric assay, respectively.

RESULTS

Luteolin dose-dependently (10-100 μmol/L) elicited relaxation of PE- or potassium-contracted aortic rings. The vasorelaxation effect of luteolin was attenuated by the eNOS inhibitor, N-nitro-L-arginine methyl ester, suggesting that this luteolin action is at least partially mediated by activating eNOS activity. We further found that luteolin dose-dependently (10-100 μmol/L) increased eNOS phosphorylation at Ser1177 (up to 1.9-fold) in isolated rat rings. Consistently, exposure of HAECs to luteolin also increased eNOS phosphorylation and NO production.

CONCLUSIONS

Luteolin may be a vascular protective agent by directly acting on vascular ECs to stimulate NO-dependent vascular dilatation.

Mice long-term high-fat diet feeding recapitulates human cardiovascular alterations: an animal model to study the early phases of diabetic cardiomyopathy

Background/Aim

Hypercaloric diet ingestion and sedentary lifestyle result in obesity. Metabolic syndrome is a cluster of clinical features secondary to obesity, considered as a pre-diabetic condition and recognized as an independent risk factor for cardiovascular diseases. To better understand the relationship between obesity, metabolic syndrome and cardiovascular disease as well as for the development of novel therapeutic strategies, animal models that reproduce the etiology, course and outcomes of these pathologies are required. The aim of this work was to characterize the long-term effects of high-fat diet-induced obesity on the mice cardiovascular system, in order to make available a new animal model for diabetic cardiomyopathy.

Methods/Results

Male C57BL/6 mice were fed with a standardized high-fat diet (obese) or regular diet (normal) for 16 months. Metabolic syndrome was evaluated testing plasma glucose, triglycerides, cholesterol, insulin, and glucose tolerance. Arterial pressure was measured using a sphygmomanometer (non invasive method) and by hemodynamic parameters (invasive method). Cardiac anatomy was described based on echocardiography and histological studies. Cardiac function was assessed by cardiac catheterization under a stress test. Cardiac remodelling and metabolic biomarkers were assessed by RT-qPCR and immunoblotting. As of month eight, the obese mice were overweight, hyperglycaemic, insulin resistant, hyperinsulinemic and hypercholesterolemic. At month 16, they also presented normal arterial pressure but altered vascular reactivity (vasoconstriction), and cardiac contractility reserve reduction, heart mass increase, cardiomyocyte hypertrophy, cardiac fibrosis, and heart metabolic compensations. By contrast, the normal mice remained healthy throughout the study.

Conclusions

Mice fed with a high-fat diet for prolonged time recapitulates the etiology, course and outcomes of the early phases of human diabetic cardiomyopathy.

Short-term hypercaloric diet induces blunted aortic vasoconstriction and enhanced vasorelaxation via increased nitric oxide synthase 3 activity and expression in Dahl salt-sensitive rats

AIM

To elucidate the role of the O(2)(-), H(2)O(2) or NO pathways in aortic angiotensin (Ang)II-induced vasoconstriction in Dahl salt-sensitive (SS) rats compared with control SS-13(BN) rats on a normal or hypercaloric diet.

METHODS

Aortic function was assessed using wire myography in 16-week-old rats maintained on a normal diet or a 4-week hypercaloric diet. Nitric oxide synthase (NOS) activity and expression was determined by the conversion of radio-labelled arginine to citrulline and Western blot analysis respectively.

RESULTS

On normal diet, AngII-induced vasoconstriction was greater in SS than SS-13(BN) rats. Polyethylene glycol superoxide dismutase (PEG-SOD) reduced the aortic AngII response similarly in both strains on normal diet. Catalase blunted, whereas N(ω)-Nitro-L-arginine methyl ester (L-NAME) did not affect the AngII response in SS rats. In SS-13(BN) rats, catalase had no effect and L-NAME enhanced AngII response. On hypercaloric diet, aortic AngII responsiveness was reduced in SS but unaltered in SS-13(BN) rats compared with their normal diet counterparts. PEG-SOD reduced the AngII response in both rats on hypercaloric diet. Catalase treatment did not alter aortic AngII response, while L-NAME increased the response in SS rats on hypercaloric diet. In SS-13(BN) rats on hypercaloric diet, catalase reduced and L-NAME did not alter the AngII response. Furthermore, aortic endothelial-dependent vasorelaxation was increased in SS rats on hypercaloric diet compared with normal diet and aortic NOS3 activity and expression was increased.

CONCLUSION

A short-term hypercaloric diet induces a blunted vasoconstrictive and enhanced vasodilatory phenotype in SS rats, but not in SS-13(BN) rats, via reduced H(2)O(2) and increased NOS3 function.

Effect of celecoxib on cyclooxygenase-1-mediated prostacyclin synthesis and endothelium-dependent contraction in mouse arteries

This study aimed to determine whether a cyclooxygenase-2 (COX-2) inhibitor celecoxib influences endothelium-dependent contraction independent of its action on COX-2 and, if so, the underlying mechanism(s). Abdominal aortas and/or carotid arteries from C57BL/6 mice or those with genetic COX-2 deficiency (COX-2(-/-)) were isolated for functional and/or biochemical analyses. Result showed that following NO synthase inhibition celecoxib not only reduced the contraction evoked by acetylcholine in C57BL/6 abdominal aorta, but also that in COX-2 (-/-) mice showing a comparable magnitude. Notably, the IC(50) of celecoxib obtained in COX-2 (-/-) abdominal aorta was only ~0.364 μM. Also, celecoxib exhibited a similar effect on COX-2 (-/-) carotid arteries. Interestingly, celecoxib was not only found to inhibit the production of the prostacyclin (PGI(2)) metabolite 6-keto-PGF (1α) in COX-2 (-/-) aortas, but also caused a reduction in the contraction evoked by PGI(2), by the α(1)-adrenergic agonist phenylephrine, or by 30 mM K(+)-induced depolarization in COX-2 (-/-) and/or C57BL/6 abdominal aorta. Moreover, N-[2-(cyclohexyloxy)-4-nitrophenyl]-methanesulfonamide (NS398), another COX-2 inhibitor, also reduced the contraction evoked by acetylcholine or by 30 mM K(+)-induced depolarization in COX-2 (-/-) mice. These results demonstrate explicitly that in mouse arteries celecoxib not only inhibits COX-1-mediated synthesis of PGI(2) and probably some other prostanoids, but also causes a reduction in vessel contractility that is independent of either COX-2 or COX-1, leading to an inhibition of COX-1-mediated endothelium-dependent contraction with an IC(50) value far below that of it considered for COX-1 . Also, our data suggest that such effects of celecoxib could be possibly shared by some other COX-2 inhibitors, such as NS398.

Vascular hyporeactivity to angiotensin II and noradrenaline in a rabbit model of obesity

This study was conducted to explore the vascular reactivity of angiotensin II and noradrenaline and their relationship with endothelial function in rabbits fed a high-fat diet (HFD). The animals were fed either an HFD or regular chow [control diet (CD)]. After 12 weeks, the rabbits fed the HFD showed higher blood pressure, body weight, and insulin levels. Glucose tolerance was impaired and positively related to blood pressure. An endothelium-independent decrease of the sensitivity to angiotensin II [pD2 endothelium-intact aortic rings (E+) in CD: 8.02 ± 0.07 vs. HFD: 7.60 ± 0.01; pD2 endothelium-removed aortic rings (E-) in CD: 8.16 ± 0.11 vs. HFD: 7.83 ± 0.16] and noradrenaline (pD2 E+ in CD: 6.36 ± 0.06 vs. HFD: 5.29 ± 0.06; pD2 E- in CD: 6.11 ± 0.08 vs. HFD: 5.80 ± 0.08) was found. Noradrenaline desensitized the angiotensin II response (pD2 with noradrenaline pretreatment in E+: 7.03 ± 0.16; in E-: 7.10 ± 0.02), but angiotensin II did not change the noradrenaline response. Acetylcholine maximal relaxation and basal nitric oxide (NO) release were comparable in both diet groups. The efficacy of angiotensin II (Rmax CD: 4604 ± 574 mg vs. HFD: 3251 ± 533 mg) and noradrenaline (Rmax CD: 11,675 ± 804 mg vs. HFD: 7975 ± 960 mg) was reduced in E+. L-N-nitroarginine methyl ester (L-NAME) recovered the efficacy of noradrenaline (Rmax L-NAME: 12,015 ± 317 mg). In contrast, L-NAME had no effect on the angiotensin II response. Noradrenaline enhanced NO levels, but angiotensin II did not. Therefore, NO was associated with hyporeactivity to noradrenaline. The resting potential was more negative in E+, and the endothelium diminished the angiotensin II-induced depolarization. These findings demonstrated that the crosstalk and the endothelium may induce hyporeactivity to angiotensin II and noradrenaline as a mechanism to compensate the increase in the blood pressure in HFD-induced obesity.

Obesity and risk of vascular disease: importance of endothelium-dependent vasoconstriction

Obesity has become a serious global health issue affecting both adults and children. Recent devolopments in world demographics and declining health status of the world's population indicate that the prevalence of obesity will continue to increase in the next decades. As a disease, obesity has deleterious effects on metabolic homeostasis, and affects numerous organ systems including heart, kidney and the vascular system. Thus, obesity is now regarded as an independent risk factor for atherosclerosis-related diseases such as coronary artery disease, myocardial infarction and stroke. In the arterial system, endothelial cells are both the source and target of factors contributing to atherosclerosis. Endothelial vasoactive factors regulate vascular homeostasis under physiological conditions and maintain basal vascular tone. Obesity results in an imbalance between endothelium-derived vasoactive factors favouring vasoconstriction, cell growth and inflammatory activation. Abnormal regulation of these factors due to endothelial cell dysfunction is both a consequence and a cause of vascular disease processes. Finally, because of the similarities of the vascular pathomechanisms activated, obesity can be considered to cause accelerated, 'premature' vascular aging. Here, we will review some of the pathomechanisms involved in obesity-related activation of endothelium-dependent vasoconstriction, the clinical relevance of obesity-associated vascular risk, and therapeutic interventions using 'endothelial therapy' aiming at maintaining or restoring vascular endothelial health.

LINKED ARTICLES

This article is part of a themed section on Fat and Vascular Responsiveness. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-3.

Blood Pressure-Lowering Mechanisms of the DASH Dietary Pattern

Potential blood pressure- (BP-) lowering mechanisms of the DASH dietary pattern were measured in 20 unmedicated hypertensive adults in a controlled feeding study. At screening, participants averaged 44.3 ± 7.8 years, BMI 33.9 ± 6.6 Kg/m(2), and BP 144.2 ± 9.38/88.5 ± 6.03 mmHg. All consumed a control diet for one week, then were randomized to control or DASH for another two weeks (week one and two). With DASH, but not controls, SBP fell by 10.65 ± 12.89 (P = 0.023) and 9.60 ± 11.23 (P = 0.039) mmHg and DBP by 5.95 ± 8.01 (P = 0.069) and 8.60 ± 9.13 mmHg (P = 0.011) at the end of week one and two, respectively. Univariate regressions showed that changes in urinary sodium/potassium ratio (β = 1.99) and plasma renin activity (β = -15.78) and percent change in plasma nitrite after hyperemia were associated with SBP changes at week one (all P < 0.05). Plasma nitrite following hyperemia showed a treatment effect (P = 0.014) and increased at week two (P = 0.001). Pulse wave velocity decreased over time with DASH (trend P = 0.019), and reached significance at week two (P = 0.026). This response may be mediated by an improvement in upregulation of nitric oxide bioavailability. Early natriuresis and reductions in oxidative stress cannot be ruled out. Future studies are needed to verify these findings, assess the possibility of earlier effects, and examine other potential mediators.

Energy restriction and exercise modulate angiopoietins and vascular endothelial growth factor expression in the cavernous tissue of high-fat diet-fed rats

The purpose of the current study was to evaluate the effect of a high-fat (HF) diet, energy restriction and exercise on the expression of vascular endothelial growth factor (VEGF), angiopoietin (Ang) 1 and 2, and their receptors in rat corpus cavernosum (CC). Male Wistar rats were fed ad libitum with an HF diet for 8 or 16 weeks. After 8 weeks of the HF diet, a group of rats was subjected to energy restriction with or without exercise for 8 weeks. Control animals had free access to standard diet for the same period. After euthanasia, blood was collected and the penises removed for immunofluorescence assays (VEGF, VEGF receptor (VEGFR) 1 and 2, Ang1, Ang2 and Tie2) and semiquantification of VEGF, VEGFR1, VEGFR2, Ang1, Ang2, Tie2, endothelial nitric oxide synthase (eNOS) and Akt/phospho-Akt by Western blotting. HF diet-fed rats exhibited lower high-density lipoprotein cholesterol (HDL-c) levels, higher systolic blood pressure and an increased atherogenic index. A significant increase in Ang2 expression in the CC was verified and coupled to a decrease in VEGF and VEGFRs. The Akt pathway was activated by the HF diet. Energy restriction and exercise increased eNOS expression and restored most HF diet-induced modifications except for VEGFR2 expression. These results emphasize the role of diet on vascular function regulation, demonstrating that cavernous imbalance of VEGF/VEGFRs and Angs/Tie2 systems occurs before serum lipid changes and obesity onset, antedating structural atherosclerotic features.

Involvement of cyclo-oxygenase-1-mediated prostacyclin synthesis in the vasoconstrictor activity evoked by ACh in mouse arteries

This study was to determine whether the endothelium of mouse major arteries produces prostacyclin (PGI(2)) and, if so, to determine how PGI(2) affects vasomotor reactivity and whether cyclo-oxygenase-1 (COX-1) contributes to PGI(2) synthesis. Abdominal aortas, carotid and femoral arteries were isolated from wild-type mice and/or those with COX-1 or -2 deficiency (COX-1(-/-); COX-2(-/-)) for biochemical and/or functional analyses. The PGI(2) metabolite 6-keto-PGF(1α) was analysed with high-performance liquid chromatography-mass spectroscopy, while vasoreactivity was determined with isometric force measurement. Results showed that in the abdominal aorta, ACh evoked endothelium-dependent production of 6-keto-PGF(1α), which was abolished by COX-1(-/-), but not by COX-2(-/-). Interestingly, COX-1(-/-) enhanced the dilatation in response to ACh, while PGI(2), which evoked relaxation of the mesenteric artery, caused contraction that was abolished by antagonizing thromboxane prostanoid (TP) receptors in the abdominal aorta. However, the TP receptor agonist U46619 evoked similar contractions in the abdominal aorta and mesenteric artery. Also, antagonizing TP receptors enhanced the relaxation in response to PGI(2) in mesenteric arteries. Real-time PCR showed that the PGI(2) (IP) receptor mRNA level was lower in the abdominal aorta than in mesenteric arteries. In addition, COX-1(-/-) not only abolished the contraction in response to ACh following NO inhibition in abdominal aorta, but also those in the carotid and femoral arteries. These results demonstrate an explicit role for endothelial COX-1 in PGI(2) synthesis and suggest that in given mouse arteries, PGI(2) mediates not dilatation but rather vasoconstrictor activity, possibly due to a low expression or functional presence of IP receptors, which enables PGI(2) to act mainly on TP receptors.

Obesity, insulin resistance and diabetes: sex differences and role of oestrogen receptors

Obesity increases the risk of coronary artery disease through insulin resistance, diabetes, arterial hypertension and dyslipidemia. The prevalence of obesity has increased worldwide and is particularly high among middle-aged women and men. After menopause, women are at an increased risk to develop visceral obesity due to the loss of endogenous ovarian hormone production. Effects of oestrogens are classically mediated by the two nuclear oestrogen receptors (ERs) α and β. In addition, more recent research has shown that the intracellular transmembrane G-protein-coupled oestrogen receptor (GPER) originally designated as GPR30 also mediates some of the actions attributed to oestrogens. Oestrogen and its receptors are important regulators of body weight and insulin sensitivity not only in women but also in men as demonstrated by ER mutations in rodents and humans. This article reviews the role of sex hormones and ERs in the context of obesity, insulin sensitivity and diabetes as well as the related clinical issues in women and men.

Could a high-fat diet rich in unsaturated fatty acids impair the cardiovascular system?

BACKGROUND

Dyslipidemia results from consumption of a diet rich in saturated fatty acids and is usually associated with cardiovascular disease. A diet rich in unsaturated fatty acids is usually associated with improved cardiovascular condition.

OBJECTIVE

To investigate whether a high-fat diet rich in unsaturated fatty acids (U-HFD) - in which fatty acid represents approximately 45% of the total calories - impairs the cardiovascular system.

METHODS

Male, 30-day-old Wistar rats were fed a standard (control) diet or a U-HFD containing 83% unsaturated fatty acid for 19 weeks. The in vivo electrocardiogram, the spectral analysis of heart rate variability, and the vascular reactivity responses to phenylephrine, acetylcholine, noradrenaline and prazosin in aortic ring preparations were analyzed to assess the cardiovascular parameters.

RESULTS

After 19 weeks, the U-HFD rats had increased total body fat, baseline glucose levels and feed efficiency compared with control rats. However, the final body weight, systolic blood pressure, area under the curve for glucose, calorie intake and heart weight⁄final body weight ratio were similar between the groups. In addition, both groups demonstrated no alteration in the electrocardiogram or cardiac sympathetic parameters. There was no difference in the responses to acetylcholine or the maximal contractile response of the thoracic aorta to phenylephrine between groups, but the concentration necessary to produce 50% of maximal response showed a decrease in the sensitivity to phenylephrine in U-HFD rats. The cumulative concentration- effect curve for noradrenaline in the presence of prazosin was shifted similarly in both groups.

CONCLUSIONS

The present work shows that U-HFD did not impair the cardiovascular parameters analyzed.

Caloric restriction reverses high-fat diet-induced endothelial dysfunction and vascular superoxide production in C57Bl/6 mice

Obesity is frequently associated with endothelial dysfunction. We hypothesized that high-fat feeding dysregulates the balance between endothelial derived nitric oxide and superoxide formation. Furthermore, we examined whether caloric restriction could reverse the detrimental vascular effects related to obesity. Male C57Bl/6 mice were fed with normal-fat diet (fat 17%) or high-fat diet (fat 60%) for 150 days. After establishment of obesity at day 100, a subgroup of obese mice were put on caloric restriction (CR) (70% of ad libitum energy intake) for an additional 50 days. At day 100, aortic rings from obese mice receiving high-fat diet showed impaired endothelium-dependent vasodilation in response to acetylcholine (ACh). Caloric restriction reversed high-fat diet-induced endothelial dysfunction. At day 150, impaired vasodilatory responses to ACh in obese mice without caloric restriction were markedly improved by preincubation with the tetrahydrobiopterin (BH(4)) precursor sepiapterin and L-arginine, a substrate for endothelial nitric oxide synthase (eNOS). Additionally, inhibition of vascular arginase by L-norvaline partially, and superoxide scavenging by Tiron completely, restored endothelial cell function. Obese mice showed increased vascular superoxide production, which was diminished by endothelial denudation, pretreated of the vascular rings with apocynin (an inhibitor of reduced nicotinamide adenine dinucleotide phosphate [NADPH] oxidase), oxypurinol (an inhibitor of xanthine oxidase), N(G)-nitro-L-arginine methyl ester (LNAME; an inhibitor of eNOS), or by adding the BH(4) precursor sepiapterin. Caloric restriction markedly attenuated vascular superoxide production. In obese mice on CR, endothelial denudation increased superoxide formation whereas vascular superoxide production was unaffected by L-NAME. Western blot analysis revealed decreased phosphorylated eNOS (Ser1177)-to-total eNOS expression ratio in obese mice as compared to lean controls, whereas the phospho-eNOS/NOS ratio in obese mice on CR did not differ from the lean controls. In conclusion, the present study suggests that caloric restriction reverses obesity induced endothelial dysfunction and vascular oxidative stress, and underscores the importance of uncoupled eNOS in the pathogenesis.

Metabolic syndrome components in murine models

Animal models have enriched understanding of the physiological basis of metabolic disorders and advanced identification of genetic risk factors underlying the metabolic syndrome (MetS). Murine models are especially appropriate for this type of research, and are an excellent resource not only for identifying candidate genomic regions, but also for illuminating the possible molecular mechanisms or pathways affected in individual components of MetS. In this review, we briefly discuss findings from mouse models of metabolic disorders, particularly in light of issues raised by the recent flood of human genome-wide association studies (GWAS) results. We describe how mouse models are revealing that genotype interacts with environment in important ways, indicating that the underlying genetics of MetS is highly context dependant. Further we show that epistasis, imprinting and maternal effects each contribute to the genetic architecture underlying variation in metabolic traits, and mouse models provide an opportunity to dissect these aspects of the genetic architecture that are difficult if not impossible to ascertain in humans. Finally we discuss how knowledge gained from mouse models can be used in conjunction with comparative genomic methods and bioinformatic resources to inform human MetS research.

Diet-induced renal changes in Zucker rats are ameliorated by the superoxide dismutase mimetic TEMPOL

Diabetic nephropathy is the leading cause of renal failure in the United States. The obese Zucker rat (OZR; fa/fa) is a commonly used model of type 2 diabetes and metabolic syndrome (MetS), and of the nephropathy and renal oxidative stress commonly seen in these disorders. Heterozygous lean Zucker rats (LZRs; fa/+) are susceptible to high-fat diet (HFD)-induced obesity and MetS. The present study was designed to investigate whether 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPOL), a membrane-permeable radical scavenger, could alleviate the renal effects of MetS in OZR and LZR fed a HFD, which resembles the typical "Western" diet. OZR and LZR were fed a HFD (OZR-HFD and LZR-HFD) or regular diet (OZR-RD and LZR-RD) and allowed free access to drinking water or water containing 1 mmol/l TEMPOL for 10 weeks. When compared to OZR-RD animals, OZR-HFD animals exhibited significantly higher levels of total renal cortical reactive oxygen species (ROS) production, plasma lipids, insulin, C-reactive protein, blood urea nitrogen (BUN), creatinine (Cr), and urinary albumin excretion (P < 0.05); these changes were accompanied by a significant decrease in plasma high-density lipoprotein levels (P < 0.05). The mRNA expression levels of desmin, tumor necrosis factor-alpha (TNF-alpha), nuclear factor kappaB (NFkappaB), and NAD(P)H oxidase-1 (NOX-1) were significantly higher in the renal cortical tissues of OZR-HFD animals; NFkappaB p65 DNA binding activity as determined by electrophoretic mobility shift assay was also significantly higher in these animals. The same trends were noted in LZR-HFD animals. Our data demonstrate that TEMPOL may prove beneficial in treating the early stages of the nephropathy often associated with MetS.

Mechanisms of coronary microvascular adaptation to obesity

The metabolic syndrome (MetS) is associated with clustering of cardiovascular risk factors in individuals that may greatly increase their risk of developing coronary artery disease. Obesity and related metabolic dysfunction are the driving forces in the prevalence of MetS. It is believed that obesity has detrimental effects on cardiovascular function, but its overall impact on the vasomotor regulation of small coronary arteries is still debated. Emerging evidence indicates that in obesity coronary arteries adapt to hemodynamic changes via maintaining and/or upregulating cellular mechanism(s) intrinsic to the vascular wall. Among other factors, endothelial production of cyclooxygenase-2-derived prostacyclin and reactive oxygen species, as well as increased nitric oxide sensitivity and potassium channel activation in smooth muscle cells, have been implicated in maintaining coronary vasodilator function. This review aims to examine studies that have been primarily focused on alterations in coronary vasodilator function in obesity. A better understanding of cellular mechanisms that may contribute to coronary microvascular adaptation may provide insight into the sequence of pathological events in obesity and may allow the harnessing of these effects for therapeutic purposes.

Effects of pyrrolidine dithiocarbamate on high-fat diet-induced metabolic and renal alterations in rats

AIMS

We investigated the effects of the nuclear factor kappa B (NFkappaB) blocker pyrrolidine dithiocarbamate (PDTC) on high-fat diet (HFD)-induced metabolic and renal alterations in obese and lean Zucker rats (OZR and LZR, respectively).

MAIN METHODS

Rats were fed a HFD resembling the typical "Western" diet or a regular diet (RD) and allowed free access to tap water or tap water containing PDTC (150 mg/kg body weight) for 10 weeks; rats were then sacrificed. Total ROS production rates were measured using electron paramagnetic resonance spectroscopy, and superoxide production was measured with lucigenin assay. Blood, plasma, and urine were analyzed. Semi-quantitative reverse transcriptase-polymerase chain reaction and electrophoretic mobility shift assay were conducted to assess NFkappaB mRNA levels and DNA binding activities, respectively; immunofluorescence was performed to assess protein levels.

KEY FINDINGS

OZR-HFD rats exhibited significantly higher levels of total renal cortical reactive oxygen species production, plasma lipids, insulin, C-reactive protein, blood urea nitrogen, creatinine, and urinary albumin excretion than all other groups (p<0.05); these changes were accompanied by a significant decrease in plasma high density lipoprotein levels (p<0.05). Gene expression levels of desmin, cytokine and oxidative stress genes were significantly higher in the renal cortical tissues of OZR-HFD; NFkappaB p65 DNA binding activity was also significantly higher in these animals. PDTC attenuated these changes.

SIGNIFICANCE

Our data suggest that NFkappaB blockade may prove beneficial in treating the nephropathy often associated with metabolic syndrome.

Endothelial dysfunction and vascular disease

The endothelium can evoke relaxations (dilatations) of the underlying vascular smooth muscle, by releasing vasodilator substances. The best characterized endothelium-derived relaxing factor (EDRF) is nitric oxide (NO). The endothelial cells also evoke hyperpolarization of the cell membrane of vascular smooth muscle (endothelium-dependent hyperpolarizations, EDHF-mediated responses). Endothelium-dependent relaxations involve both pertussis toxin-sensitive G(i) (e.g. responses to serotonin and thrombin) and pertussis toxin-insensitive G(q) (e.g. adenosine diphosphate and bradykinin) coupling proteins. The release of NO by the endothelial cell can be up-regulated (e.g. by oestrogens, exercise and dietary factors) and down-regulated (e.g. oxidative stress, smoking and oxidized low-density lipoproteins). It is reduced in the course of vascular disease (e.g. diabetes and hypertension). Arteries covered with regenerated endothelium (e.g. following angioplasty) selectively loose the pertussis toxin-sensitive pathway for NO release which favours vasospasm, thrombosis, penetration of macrophages, cellular growth and the inflammatory reaction leading to atherosclerosis. In addition to the release of NO (and causing endothelium-dependent hyperpolarizations), endothelial cells also can evoke contraction (constriction) of the underlying vascular smooth muscle cells by releasing endothelium-derived contracting factor (EDCF). Most endothelium-dependent acute increases in contractile force are due to the formation of vasoconstrictor prostanoids (endoperoxides and prostacyclin) which activate TP receptors of the vascular smooth muscle cells. EDCF-mediated responses are exacerbated when the production of NO is impaired (e.g. by oxidative stress, ageing, spontaneous hypertension and diabetes). They contribute to the blunting of endothelium-dependent vasodilatations in aged subjects and essential hypertensive patients.

Early atherosclerosis and vascular inflammation in mice with diet-induced type 2 diabetes

BACKGROUND

Obesity and type 2 diabetes increase the risk of atherosclerosis. It is unknown to what extent this reflects direct effects on the arterial wall or secondary effects of hyperlipidaemia.

MATERIALS AND METHODS

The effect of obesity and type 2 diabetes on the development of atherosclerosis and inflammation, in the absence or presence of hyperlipidaemia, was assed in wild-type (n = 36) and human apolipoprotein B (apoB) transgenic mice (n = 27) that were fed normal chow or 60% fat for 12 months.

RESULTS

Fat-feeding caused obesity, glucose intolerance and elevated plasma leptin and soluble vascular cell adhesion molecule-1 (sVCAM-1) in both wild-type and apoB transgenic mice. In wild-type mice, plasma very low-density lipoprotein cholesterol (VLDL-C) and low-density lipoprotein cholesterol (LDL-C) were unaffected by fat-feeding. ApoB transgenic mice had mildly elevated plasma LDL-C (approximately 1 mmol L(-1)), which was slightly increased by fat-feeding. Sixty-four per cent of fat-fed wild-type mice vs. 7% of chow-fed wild-type mice had lipid-staining intimal lesions in the aortic root (P = 0.002). Eighty-six per cent of fat-fed apoB transgenic mice had lipid-staining lesions and the median lesion area was 8.0 times higher than in fat-fed wild-type mice (P = 0.001). Intracellular adhesion molecule-1 staining of the aortic endothelium was most pronounced in the fat-fed apoB transgenic mice.

CONCLUSIONS

Our findings suggest that diet-induced type 2 diabetes causes early atherosclerosis in the absence of dyslipidaemia, and that even a moderate level of LDL-C markedly augments this effect.

Endothelin: 20 years from discovery to therapy

Since its identification as an endothelial cell-derived vasoconstrictor peptide in 1988, endothelin-1, the predominant member of the endothelin peptide family, has received considerable interest in basic medical science and in clinical medicine, which is reflected by more than 20 000 scientific publications on endothelin research in the past 20 years. The story of endothelin is unique as the gene sequences of endothelin receptors and the first receptor antagonists became available within only 4 years of the identification of the peptide sequence. The first clinical study in patients with congestive heart failure was published only 3 years thereafter. Yet, despite convincing experimental evidence of a pathogenetic role for endothelin in development, cell function, and disease, many initial clinical studies on endothelin antagonism were negative. In many of these studies, study designs or patient selection were inadequate. Today, for diseases such as pulmonary hypertension, endothelin antagonist treatment has become reality in clinical medicine, and ongoing clinical studies are evaluating additional indications, such as renal disease and cancer. Twenty years after the discovery of endothelin, its inhibitors have finally arrived in the clinical arena and are now providing us with new options to treat disease and prolong the lives of patients. Possible future indications include resistant arterial hypertension, proteinuric renal disease, cancer, and connective tissue diseases.

Differential effects of diet-induced dyslipidemia and hyperglycemia on mesenteric resistance artery structure and function in type 2 diabetes

Type 2 diabetes and dyslipidemia oftentimes present in combination. However, the relative roles of diabetes and diet-induced dyslipidemia in mediating changes in vascular structure, mechanics, and function are poorly understood. Our hypothesis was that addition of a high-fat diet would exacerbate small artery remodeling, compliance, and vascular dysfunction in type 2 diabetes. Vascular remodeling indices [media/lumen (M/L) ratio, collagen abundance and turnover, and matrix metalloproteinase dynamics], mechanical properties (vessel stiffness), and reactivity to pressure and vasoactive factors were measured in third-order mesenteric arteries in control Wistar and type 2 diabetic Goto-Kakizaki (GK) rats fed either a regular or high-fat diet. M/L ratios, total collagen, and myogenic tone were increased in diabetes. Addition of the high-fat diet altered collagen patterns (mature versus new collagen) in favor of matrix accumulation. Addition of a high-fat diet caused increased constriction to endothelin-1 (0.1-100 nM), showed impaired vasorelaxation to both acetylcholine (0.1 nM-1 microM) and sodium nitroprusside (0.1 nM-1 microM), and increased cardiovascular risk factors in diabetes. These results suggest that moderate elevations in blood glucose, as seen in our lean GK model of type 2 diabetes, promote resistance artery remodeling resulting in increased medial thickness, whereas addition of a high-fat diet contributes to diabetic vascular disease predominantly by impairing vascular reactivity in the time frame used for this study. Although differential in their vascular effects, both hyperglycemia and diet-induced dyslipidemia need to be targeted for effective prevention and treatment of diabetic vascular disease.

Diabetic state, high plasma insulin and angiotensin II combine to augment endothelin-1-induced vasoconstriction via ETA receptors and ERK

BACKGROUND AND PURPOSE

Mechanisms associated with the enhanced contractile response to endothelin-1 in hyperinsulinaemic diabetes have been examined using the rat aorta. Functions for angiotensin II, endothelin-1 receptor expression and extracellular signal-regulated kinase (ERK) have been investigated.

EXPERIMENTAL APPROACH

Streptozotocin-induced diabetic rats were infused with angiotensin II or, following insulin treatment, were treated with losartan, an angiotensin II receptor antagonist. Contractions of aortic strips with or without endothelium, in response to endothelin-1 and angiotensin II, were examined in vitro. Aortic ET(A) receptors and ERK/MEK expression were measured by western blotting.

KEY RESULTS

Insulin-treated diabetic rats exhibited increases in plasma insulin, angiotensin II and endothelin-1. The systolic blood pressure and endothelin-1-induced contractile responses in aortae in vitro were enhanced in insulin-treated diabetic rats and blunted by chronic losartan administration. LY294002 (phosphatidylinositol 3-kinase inhibitor) and/or PD98059 (MEK inhibitor) diminished the enhanced contractile response to endothelin-1 in aortae from insulin-treated diabetic rats. ET(A) and ET(B) receptors, ERK-1/2 and MEK-1/2 protein expression and endothelin-1-stimulated ERK phosphorylation were all increased in aortae from insulin-treated diabetic rats. Such increases were blunted by chronic losartan administration. Endothelin-1-induced contraction was significantly higher in aortae from angiotensin II-infused diabetic rats. angiotensin II-infusion increased ERK phosphorylation, but the expression of endothelin receptors and ERK/MEK proteins remained unchanged.

CONCLUSIONS AND IMPLICATIONS

These results suggest that the combination of high plasma angiotensin II and insulin with a diabetic state induced enhancement of endothelin-1-induced vasoconstriction, ET(A) receptor expression and ERK expression/activity in the aorta. Losartan improved both the diabetes-related abnormalities and the diabetic hypertension.

Fat intake and cardiovascular response

High dietary fat intake is a major risk factor for the development of obesity, which is frequently associated with diseases such as hypertension and diabetes and thus accelerated atherosclerosis. Angiotensin II and endothelin-1 are powerful growth factors and vasoconstrictors implicated in regulating vascular tone, vascular structure, and inflammation. Reduced bioactivity of nitric oxide and increased formation of reactive oxygen species (ROS) have been associated with obesity and high dietary fat intake. This article reviews the effects of high-fat diet on vascular functional changes in rodents and humans. Changes include alterations in vasoconstrictor function and receptor expression, and modulators of endothelium-dependent vascular tone (eg, nitric oxide- or endothelium-dependent contracting factor-mediated responses). Novel vasodilator effects of ROS and the anatomic heterogeneity of vascular responses are discussed. The beneficial effects of vasoactive mediators on vascular function could play a role for susceptibility to obesity-dependent hypertension, which is present in many, but not all, obese patients.

Eicosanoids and renal damage in cardiometabolic syndrome

BACKGROUND

Obesity, hypertension and Type 2 diabetes are major contributing factors to the increase in the number of patients that have chronic kidney disease. The clustering of visceral obesity and cardiovascular risk factors has been designated metabolic syndrome or cardiometabolic syndrome. Cardiometabolic syndrome is associated with a complex systemic inflammatory state that has been implicated in medically important complications, including endothelial dysfunction. Inflammation, endothelial dysfunction and insulin resistance are interrelated and have reciprocal relationships that link cardiovascular and metabolic diseases. Ultimately, cardiometabolic syndrome increases the risk for cardiovascular events and end-organ damage. Although the number of patients with cardiometabolic syndrome is escalating, therapeutic approaches have not been developed that provide protection to the kidney.

OBJECTIVE

The objective of this review is to provide an overview of the contribution of eicosanoids to renal damage in cardiometabolic syndrome.

RESULTS/CONCLUSION

Eicosanoids are altered in cardiometabolic syndrome and contribute to the progression of renal injury. The antihypertensive and anti-inflammatory actions of epoxides and soluble epoxide hydrolase inhibitors make these attractive eicosanoid therapeutic targets for chronic kidney disease in patients with cardiometabolic syndrome.

Regional heterogeneity of functional changes in conduit arteries after high-fat diet

OBJECTIVE

To determine effects of dietary fat content on vascular responses in different conduit arteries in mice.

METHODS AND PROCEDURES

Vascular responses to reactive oxygen species (ROS)/hydroxyl radical (.OH), acetylcholine (ACh), endothelin-1 (ET-1), and angiotensin II (Ang II) were determined in carotid and femoral arteries of C57BL/6J mice fed with diets varying in fat content (low fat (LF), 12.3%; high fat (HF), 41%; and very high fat (VHF), 58% (kcal from fat)) for 15 weeks, beginning at 4 weeks of age.

RESULTS

In precontracted rings of carotid and femoral artery, ROS/.OH-induced a rapid, transient vasodilation. In the carotid, but not in femoral artery, ROS/.OH-induced dilation increased with increasing dietary fat intake (P < 0.05 vs. LF diet), while contractile responses to ROS/.OH remained unaffected. In femoral arteries, ROS/.OH-induced contractions were reversed into relaxations after both HF and VHF diet (P < 0.05 vs. LF diet). Both ET-1 and Ang II induced strong contractions in the femoral artery that were unaffected by dietary fat intake. In contrast, in the carotid artery Ang II-induced contraction was attenuated after HF and VHF diets (P < 0.005 vs. LF diet), whereas ET-1-induced vasoconstriction was significantly increased (P < 0.05 VHF vs. LF and HF). Treatment with VHF diet enhanced ACh-mediated endothelium-dependent relaxation only in the femoral artery (P < 0.05 vs. HF).

DISCUSSION

These findings demonstrate that dietary fat content has regional and distinct effects on vascular function in different vascular beds. The data also suggest the possibility that in selected conduit arteries ROS-dependent vasodilator mechanisms become activated in response to increased dietary fat intake.