<p>The vasculature has a crucial function in normal physiology, enabling the transport of oxygen and nutrients to cells throughout the body. In turn, endothelial cells, which form the inner-most lining of blood vessels, are key regulators of vascular function. In addition to forming a barrier which separates the circulation from underlying tissues, endothelial cells respond to diverse extracellular cues and produce a variety of biologically-active mediators in order to maintain vascular homeostasis. Disruption of normal vascular function is a prominent feature of a variety of pathological conditions. Thus, elucidating the signaling pathways regulating endothelial function is critical for understanding the role of endothelial cells in both normal physiology and pathology, as well as for potential development of therapeutic interventions.</p><p>In this dissertation, we use a combination of pharmacological inhibition and knockdown studies, along with generation of endothelial conditional knockout mice, to demonstrate an important role of the Abelson (Abl) family of non-receptor tyrosine kinases (Abl and Arg) in vascular function. Specifically, loss of endothelial expression of the Abl kinases leads to late-stage embryonic and perinatal lethality in conditional knockout mice, indicating a crucial requirement for Abl/Arg kinases in normal vascular development and function. Endothelial <italic>Abl</italic>/<italic>Arg</italic>-null embryos display focal regions of vascular loss and tissue damage, as well as increased endothelial cell apoptosis. An important pro-survival function for the Abl kinases is further supported by our finding that either microRNA-mediated <italic>Abl</italic>/<italic>Arg</italic> depletion or pharmacological inhibition of the Abl kinases increases endothelial cell susceptibility to stress-induced apoptosis <italic>in vitro</italic>. The Abl kinases are activated in response to treatment with the pro-angiogenic growth factors vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF). We show that both VEGF- and bFGF-mediated endothelial cell survival is impaired following Abl kinase inhibition.</p><p>These studies have uncovered a previously unappreciated role for the Abl kinases in the regulation of the angiopoietin/Tie2 signaling pathway, which functions to support endothelial cell survival and vascular stability. Loss of Abl/Arg expression leads to reduced mRNA and protein levels of the Tie2 receptor, resulting in impaired activation of intracellular signaling pathways by the Tie2 ligand angiopoietin-1 (Angpt1), as well as decreased Angpt1-mediated endothelial cell survival following serum-deprivation stress. Notably, we found that the Abl kinases are activated following Angpt1 stimulation, suggesting a unique dual role for Abl and Arg in Angpt/Tie2 signaling, potentially modulating Tie2 downstream signaling responses, as well as regulating Tie2 receptor expression.</p><p>Further, we show an important contribution of the Abl family kinases to the regulation of endothelial permeability responses both <italic>in vitro</italic> and <italic>in vivo</italic>. The Abl kinases are activated in response to a diverse group of permeability-inducing factors, including VEGF and the inflammatory mediators thrombin and histamine. We show that inhibition of Abl kinase activity, using either the ATP-competitive inhibitor imatinib or the allosteric inhibitor GNF-2, protects against disruption of endothelial barrier function by the permeability-inducing factors <italic>in vitro</italic>. VEGF-induced vascular permeability similarly is decreased in conditional knockout mice lacking endothelial Abl expression, as well as following treatment with Abl kinase inhibitors <italic>in vivo</italic>. Mechanistically, we show that loss of Abl kinase activity is accompanied by activation of the barrier-stabilizing GTPases (guanosine triphosphatases) Rac1 and Rap1, as well as inhibition of agonist-induced Ca<super>2+</super> mobilization and generation of acto-myosin contractility.</p><p>Taken together, these results demonstrate involvement of the Abl family kinases in the regulation of endothelial cell responses to a broad range of pro-angiogenic and permeability-inducing factors, as well as a critical requirement for the endothelial Abl kinases in normal vascular development and function <italic>in vivo</italic>. These findings have implications for the clinical use of Abl kinase inhibitors.</p> / Dissertation

Grâce à leurs propriétés antioxydantes, les phénols de l’huile d’olive sont reconnus comme les acteurs principaux de la réduction de la mortalité cardiovasculaire et du diabète de type 2 associée au régime méditerranéen. Cependant, la forte métabolisation de l’hydroxytyrosol, principal composé phénolique de l’huile d’olive, en glucuronides, remet en question son activité biologique.Un premier objectif de ce travail de thèse a été de mettre en évidence l’importance des glucuronides dans l’amélioration de la fonction vasculaire grâce à un effet antioxydant. Néanmoins et contrairement à l’hydroxytyrosol, qui peut être transporté directement par la bilitranslocase, les glucuronides doivent, dans un premier temps, être déconjugués par la &#946;-glucuronidase afin d’exercer leur activité biologique.Un deuxième objectif de ce travail de thèse a été de mettre en évidence leurs effets chez des rats atteints de syndrome métabolique. Nous avons pu constater que ni l’hydroxytyrosol, ni ses glucuronoconjugués ne modulaient la fonction vasculaire.Enfin, un troisième objectif a été de regarder la répercussion d’une supplémentation en hydroxytyrosol, sur les facteurs de risque cardiovasculaire dans un modèle de souris atteintes de diabète de type 2. La supplémentation en hydroxytyrosol a réduit la prise de poids, les masses adipeuses et a eu des effets hypotenseurs. Ces effets hypotenseurs semblent être dus à une de la fonction des cellules musculaires lisses puisque nos travaux montrent une relaxation endothélium-indépendante améliorée. Nos travaux donnent un nouvel éclairage sur les effets de l’hydroxytyrosol et ses métabolites, tous deux contribuant, potentiellement, à la réduction de l’incidence des maladies cardiovasculaires et du diabète de type 2. / Olive oil polyphenols are well-known to lower cardiovascular mortality and type 2 diabetes incidence associated to the Mediterranean diet. However, the high metabolization rate of hydroxytyrosol, the main phenolic compound of olive oil, into glucuronides, questions its real biological effect. The first objective of this thesis was to evidence the importance of glucuronides of Hydroxytyrosol in the enhancement of vascular function through antioxidative properties. It was found that, unlike to hydroxytyrosol that can be directly transported with bilitranslocase glucuronides have to be deconjugated by β-glucuronidase to exert their biological activity. A second objective was to evidence the effects of Hydroxytyrosol and glucuronides on vascular function in diet-induced metabolic syndrome rats. Neither hydroxytyrosol nor glucuronides modulated vascular function in this pathological context. A third objective was to show the effect of a chronic Hydroxytyrosol supplementation in refined olive oil on cardiovascular risk factors in a mice model of Metabolic Syndrome. Hydroxytyrosol supplementation was able to reduce weight gain, white adipose tissues mass and to lower blood pressure. These hypotensive effects seem to be due in smooth muscle cells function. In conclusion, our works highlight the importance of Hydroxytyrosol and its glucuronoconjugated metabolites, both contributing to the reduction of the incidence of cardiovascular risk factors associated to type 2 diabetes and Metabolic syndrome.

O mecanismo hemodinâmico responsável pela hipotensão pós-exercício aeróbico varia entre os indivíduos, sendo interessante avaliar a possível influência da capacidade de vasodilatação periférica nesses mecanismos. Para tanto, 22 homens normotensos submeteram-se a 2 sessões experimentais: Controle (C - repouso) e Exercício (E- cicloergômetro, 45 min, 50% VO2pico). Antes e 60 min após as intervenções, a pressão arterial (PA) sistólica (PAS), diastólica (PAD) e média (PAM), o débito cardíaco (DC), a resistência vascular periférica (RVP), o volume sistólico (VS), a frequência cardíaca (FC), o fluxo sanguíneo muscular (FS) e a capacidade vasodilatadora periférica (avaliada pelo FS máximo póshiperemia - FSMax e pela área sob a curva pós-hiperemia - ASC) foram medidos. A ANOVA de 2 fatores para amostras repetidas foi empregada. A correlação de Pearson foi calculada entre os índices de capacidade vasodilatadora medidos préexercício e respostas ao exercício (pós-pré). O exercício diminuiu a PAS, PAM e impediu o aumento da PAD. Após o exercício, o DC diminuiu em alguns indivíduos e a RVP diminuiu em outros. O VS diminuiu pós-exercício, enquanto que a FC aumentou em alguns indivíduos e diminuiu em outros. O FS da região inativa e o FSMax da região ativa aumentaram após o exercício. Os índices de capacidade vasodilatadora (FSmax e ASC) não se correlacionaram com as respostas dos mecanismos hemodinâmicos avaliados pós-exercício, mas o FS pré-exercício da região inativa se correlacionou negativamente com a resposta da PA pós-exercício e o FS pré-exercício da região ativa se correlacionou negativamente com a resposta do FS dessa região, do VS e do DC, e positivamente com a resposta da RVP e da FC pós-exercício. Dessa forma, é possível concluir que a sessão de exercício físico proposta promove hipotensão pós-exercício cujos determinantes hemodinâmicos diferem entre os indivíduos. A xvii capacidade vasodilatadora avaliada pela resposta à hiperemia não se relaciona aos determinantes hemodinâmicos da hipotensão pós-exercício. Porém, o FS da região ativa se relaciona, de modo quanto maior for esse fluxo pré-exercício, menor é o aumento dele pós-exercício, menor a redução a RVP e maior a redução do DC e do VS / The hemodynamic mechanism responsible for post-aerobic exercise hypotension varies among individuals, which makes it interesting to evaluate the possible influence of peripheral vasodilatory capacity on them. For this purpose, 22 normotensive men underwent two experimental sessions: control (C rest) and Exercise (E cycle ergometer, 45 min, 50% VO2peak). Both prior to and 60 min after the interventions, systolic (SBP), diastolic (DBP) and mean (MBP) blood pressures (BP), cardiac output (CO), systemic vascular resistance (SVR), stroke volume (SV), heart rate (HR), muscle blood flow (BF) and peripheral vasodilatory capacity (assessed by the maximum BF after hyperemic maneuver BFMax, and the area under the curve after reactive hyperemia AUC) were measured. A two way ANOVA for repeated measures was employed. The Pearson correlation coefficient was calculated between the vasodilatory capacity measured pre exercise and the responses observed after exercise (post-pre). Exercise decreased both SBP and MBP, and prevented an increase in DBP. After exercise, CO decreased in some individuals, while SVR decreased in others. SV decreased after exercise, while HR increased in some subjects and decreased in others. BF of the inactive limb and BFMax of the active limb increased after exercise. The indices of vasodilatory capacity (BFMax and AUC) did not correlate with the hemodynamic mechanisms evaluated after exercise. However, pre-exercise BF measured on the inactive limb correlated negatively with the BP response after exercise, and pre-exercise BF of the active limb correlated negatively with SV, CO and BF of this limb after exercise, and positively with SVR and HR responses after exercise. Thus, we conclude that the exercise bout proposed in this study promotes post-exercise hypotension, but the hemodynamic determinants of this xix response differ between individuals. Vasodilatory capacity assessed by flow responses to hyperemia is not related to the hemodynamic determinants of postexercise hypotension, but the BF of the active limb is. Thus, the greater the preexercise BF of the active limb, the lower the increase in this flow and the reduction in SVR after exercise, and the greater the reduction in CO and SV

No description available.

No description available.

BACKGROUND: Age-related declines in endothelial function have been well documented with larger declines observed in middle-aged. Passive heat exposure has been shown to be a promising method to improve vascular endothelial health, with sauna specifically being linked to reduced risk of cardiovascular disease. Increases in blood flow and shear rates associated with heat exposure are often considered to have a major influence on the observed improved endothelial function following heat exposure. The magnitude of these changes in response to sauna have not yet been defined. Therefore, the purpose of this study is to quantify and compare the vascular response to an acute bout of sauna heating in young and middle-aged individuals. METHODS: 10 young (24.9 ± 4.2 years, 6 males and 4 females) and 8 middle-aged adults (55.6 ± 3.9 years 4 males and 4 females) underwent 40 min of sauna exposure at 80 oC. Esophageal and intramuscular temperatures were recorded throughout the duration of the experiment. Brachial and superficial femoral artery blood flow, artery diameter, and shear rates were recorded at baseline and following heat exposure. Brachial artery flow-mediated dilation (FMD) was measured at baseline and following 90 min of recovery. RESULTS: Core and muscle temperatures significantly increased by 1.5 ± 0.53 and 1.95 ± 0.70 °C, respectively (P < 0.05) and the magnitude of increase did not differ between young and middle-aged participants (P0.867 and 0.488, respectively). Shear rate increased by 170– 200% (P < 0.001), while blood flow increased by 180–390% (P < 0.001) in the superficial femoral and brachial artery, respectively, in both groups. Importantly, the changes in shear and flow did not significantly differ between young and middle-aged subjects for either artery (P = 0.190–0.899.) Systolic blood pressure (SBP) was significantly reduced from 135.25 ± 17.50 to 122.38 ± 19.7 mmHg (P = 0.017) only in middle-aged participants and a decrease in diastolic blood pressure was observed from 81.6 ± 13.0 mmHg at baseline to 69.8 ± 8.4 mmHg (P < .001). Heat-induced dilation was strongly correlated to baseline endothelial function in the young (R = 0.86, P = 0.006), but not the old (R = 0.22, P = 0.631). CONCLUSIONS: These results indicate that young and middle-aged adults have similar shear-rate and blood flow responses to acute sauna heating, which significantly reduces blood pressure in middle-aged, but not young individuals. Future heat therapy studies may elicit meaningful cardiovascular benefits from lower magnitudes of chronic passive heat stress.

Aging results in lower exercise tolerance, manifested as decreased Critical Power (PCRIT). Aging is also associated with reduced physical activity, decreased muscle mass, and altered muscle blood flow, all of which may contribute to the age-related decrease in PCRIT. Purpose: The purpose of this study was to determine if the age-related decrease in PCRIT occurs independently of changes in physical activity and muscle mass and if it is related to impaired muscle blood flow. Methods: 10 Old (63.1 ± 2.5 years, 5 female and 5 male) and 10 Young (24.4 ± 4.0 years, 5 female and 5 male) physically active volunteers enrolled in this study. Physical activity was measured with accelerometry. Leg muscle mass was quantified with dual x-ray absorptiometry (DEXA). PCRIT and the maximum power achieved during a graded exercise test (PGXT) during single-leg knee extension exercise were determined over the course of 4 visits. On the fifth visit, vascular function of the leg was assessed with the passive leg movement (PLM) hyperemia. Subsequently, subjects performed knee extension exercise at 10 watts (W), 20 W, 90% PCRIT, and 100% PGXT while blood flow and blood pressure were measured at the femoral artery for each intensity. Results: Young and Old subjects did not differ in daily step count (Old = 13001.1  2464.0 vs Young = 13527.0  3213.8 steps, P = 0.735) or in leg lean mass (9.06  0.62 g/kg, P = 0.901). The Old subjects had a lower mass-specific PCRIT (Old = 3.20  0.94 vs Young = 4.60  0.87 W/kg, P = 0.004), vascular function (mass-specific Passive Leg Movement (PLM): Old = 79.4  38.3 vs Young = 128.8  34.9 ml/min/kg, P = 0.010) and leg blood flow at 90% PCRIT (mass-specific: Old = 378  122 vs Young = 522  124 ml/min/kg, P = 0.014) and 100% PGXT (mass-specific: Old = 391  109 vs Young = 544  136 ml/min/kg, P = 0.013). When normalized for leg muscle mass, PCRIT was strongly correlated to peak leg blood flow in response to PLM (R2 = 0.53; P < 0.001) and leg blood flow during knee extension exercise at 90% PCRIT (R2 = 0.36; P = 0.007). Conclusion: The age-related decline in PCRIT is associated with major decreases in muscle endurance and is correlated with concomitant reductions in vascular function in healthy active adults. Future research should determine if interventions known to improve vascular function can ameliorate exercise tolerance in Old adults.

Recent evidence suggests that heat, a major byproduct of exercise, may be the mediator for many vascular adaptations that come from exercise. Thus, heat therapy that increases muscle temperature in a comparable way to exercise may be an advantageous alternative for enhancing cardiovascular health in individuals where treatment with exercise is either not possible or undesired. PURPOSE: Compare the effects of exercise and heat training on resistance artery function at rest and during exercise. METHODS: Thirty-five (18 female) healthy, untrained subjects completed a 6-week training program utilizing either high intensity knee extension (KE) exercise (40 min), localized heat therapy (pulsed shortwave diathermy; 120 min), or a sham heat therapy protocol (120 min). We randomly selected 8 subjects from each group to have a temperature probe inserted into their vastus lateralis muscle during one of their training sessions to evaluate the effect of the interventions on muscle temperature. We assessed resistance artery function at rest with the passive leg movement technique (PLM) prior to and after completion of the training protocols. We assessed peak exercise blood flow (KE peak flow) and peak power output (KE peak power) during the KE graded exercise test and prior to and after completion of the training protocols. RESULTS: Peak muscle treatment temperature was significantly different between all groups with those assigned to the diathermy heat training exhibiting a higher peak temperature (~40.80°C) than those in the exercise (~37.75°C, P < 0.001) and sham training groups (~36.10°C, P < 0.001). KE peak flow during PLM increased to the same extent (P = 0.625) in both the exercise (~10.5% increase, P = 0.009) and heating groups (~8.5% increase, P = 0.044); but tended to decrease in the sham group (P = 0.087). KE peak flow increased in the exercise group (~19%, P = 0.005), but did not change in the heat group (P = 0.523) and decreased in the sham group (~7%, P = 0.020). Peak vascular conductance during KE significantly increased by ~25% in the exercise (P = 0.030) and heat (P = 0.012) groups. KE peak power increased in the exercise group by ~27% (P = 0.001) but did not significantly change in the heat (P = 0.175) and sham groups (P = 0.111). The change in vascular function, assessed via PLM, showed a correlation with both ∆KE peak flow (R = 0.55, P = 0.01) and ∆KE peak power (R = 0.56, P = .010). Likewise, ∆KE peak flow showed a strong association with ∆KE peak power (R = 0.64, P < 0.001). CONCLUSION: Localized diathermy heat treatment increased resistance artery function at rest and during exercise to a similar extent as single-leg KE exercise training but did not yield significant improvements in performance. Thus, heat training mimics some but not all of the benefits associated with exercise and may be used to replace exercise treatment to some extent.

No description available.

Type II Diabetes Mellitus (T2D) and cardiovascular diseases (CVD) are non-communicable chronic diseases that involves impairments in glucose metabolism and vascular function. Multiple factors may increase the risk for T2D, including but not limited to genetics, obesity and lifestyle, such as physical inactivity and diet. The gut microbiota, the human's largest population of microorganisms, plays an essential role in health and disease. The physiology and function of the gastrointestinal tract can be influenced by the diet. Phosphatidylcholine (PC), a source of choline in the diet, is rich in Western-type diets. Gut microbiota metabolize choline to trimethylamine (TMA) which circulates and is oxidized in the liver to form trimethylamine N-oxide (TMAO). As a result, ingestion of PC or choline could increase levels of TMAO. Preclinical studies indicate a role of TMAO in the development of atherosclerosis. Likewise, multiple observations support a potential role of TMAO in the development of insulin resistance and T2D. Much of the research has been conducted on rodent models, while others are observational human studies. Whether acute and short-term increases in TMAO contribute to impairments in insulin sensitivity in humans remains unknown. To address this, we performed two studies utilizing a double-blind, placebo controlled, crossover design. Eligible participants consumed a 1000mg/day dose of choline bitartrate and placebo (maltodextrin) the night before each testing session (for the acute choline study) or for 4 weeks (for the short-term choline ingestion study). Oral glucose tolerance test, continuous glucose monitoring, flow-mediated dilation, and applanation tonometry was performed the day after the acute choline load and before and after the short-term choline ingestion period. We hypothesized that gut microbiota-generated increase in TMAO will impair insulin sensitivity, glucose tolerance, endothelial function and arterial stiffness in healthy sedentary humans. Following acute choline ingestion, significant increases in plasma TMAO (p = 0.013) and choline (p = 0.003) were evident. There was no statistically significant difference in insulin sensitivity, glucose tolerance or in any of the endothelial function and arterial stiffness measurements. Four weeks of 1000mg choline ingestion per day, significantly increased plasma (p = 0.042) and urine (p = 0.008) TMAO concentrations compared to the placebo. However, no significant differences were observed for any other measurements of insulin sensitivity, glucose tolerance, glycemic variability, endothelial function, and arterial stiffness. More research is needed to elucidate the mechanisms behind the mechanistic observations between elevated TMAO concentrations and T2D and CVD. / Doctor of Philosophy / Type 2 diabetes mellitus (T2D) and cardiovascular diseases (CVD) increase the risk of all-cause mortality. Choline is a nutrient that can be found in foods such as red meat, dairy, fish, and eggs. Choline is metabolized from bacteria in our gut and a metabolite called trimethylamine (TMA) is formed. TMA is then oxidized in the liver and trimethylamine-N-oxide (TMAO) is produced. A Western-type diet is rich in red meat, dairy, fish, and eggs and has been shown to increase production of the compound TMAO. Preclinical studies have suggested a causal role of TMAO in atherosclerosis and T2D and elevated plasma TMAO concentrations have been associated with an increased risk for CVD and T2D in observational studies. However, the causal nature of this relationship in humans is unknown. The studies described herein aimed to investigate the effects of increases in TMAO on insulin sensitivity and vascular function in healthy adults. The first study tested the effect of increasing TMAO on insulin sensitivity, glucose tolerance, and vascular function following an acute choline load (1000mg) and placebo (carbohydrate) the night before each testing session. In the second study, we examined the effect of increasing TMAO on insulin sensitivity, glucose tolerance, and vascular function in healthy adults, following a short-term choline load (1000mg/day) and placebo (carbohydrate) for 4 weeks. Acute and short-term choline ingestion significantly increased plasma TMAO concentrations. No significant differences were observed following acute or short-term choline ingestion for any measurement of insulin sensitivity, glucose tolerance 24-hout glycemic variability, vascular function., and arterial stiffness.