Exercise training enhances flow-mediated dilation in spontaneously hypertensive rats

The cardiovascular changes underlying a low cardiac output with exercise in patients with type 2 diabetes mellitus

The significant morbidity and premature mortality of type 2 diabetes mellitus (T2DM) is largely associated with its cardiovascular consequences. Focus has long been on the arterial atheromatosis of DM giving rise to early stroke and myocardial infarctions, whereas less attention has been given to its non-ischemic cardiovascular consequences. Irrespective of ischemic changes, T2DM is associated with heart failure (HF) most commonly with preserved ejection fraction (HFpEF). Largely due to increasing population ages, hypertension, obesity and T2DM, HFpEF is becoming the most prevalent form of heart failure. Unfortunately, randomized controlled trials of HFpEF have largely been futile, and it now seems logical to address the important different phenotypes of HFpEF to understand their underlying pathophysiology. In the early phases, HFpEF is associated with a significantly impaired ability to increase cardiac output with exercise. The lowered cardiac output with exercise results from both cardiac and peripheral causes. T2DM is associated with left ventricular (LV) diastolic dysfunction based on LV hypertrophy with myocardial disperse fibrosis and significantly impaired ability for myocardial blood flow increments with exercise. T2DM is also associated with impaired ability for skeletal muscle vasodilation during exercise, and as is the case in the myocardium, such changes may be related to vascular rarefaction. The present review discusses the underlying phenotypical changes of the heart and peripheral vascular system and their importance for an adequate increase in cardiac output. Since many of the described cardiovascular changes with T2DM must be considered difficult to change if fully developed, it is suggested that patients with T2DM are early evaluated with respect to their cardiovascular compromise.

Maternal physical activity affects yolk sac size and growth in early pregnancy, but girls and boys use different strategies

This longitudinal study investigated the impact of actigraphy-measured maternal physical activity on yolk sac size during early development. The yolk sac, a transient extraembryonic organ, plays a crucial role in embryonic development and is involved in metabolism, nutrition, growth, and hematopoiesis. Prospectively collected data from 190 healthy women indicated that their total daily physical activity, including both light and moderate-vigorous activity, was associated with yolk sac growth dynamics depending on embryonic sex and gestational age. Higher preconception maternal physical activity was linked to a larger yolk sac at 7 weeks (95% CI [0.02-0.13 mm]) and a smaller yolk sac at 10 weeks' gestation (95% CI [- 0.18 to - 0.00]) in male embryos; in female embryos, the yolk sac size was increased at 10 weeks' gestation (95% CI [0.06-0.26]) and was, on average, 24% larger than that in male embryos (95% CI [0.12-0.38]). Considering the pattern of other maternal effects on yolk sac size-e.g., body composition and sleep duration-we suggest that physiological yolk sac adaptations occur in short, sex-specific time windows and can be influenced by various maternal factors.

Prenatal exercise and cardiovascular health (PEACH) study: The remote effect of aerobic exercise training on conduit artery and resistance vessel function

We assessed the impact of a structured lower-limb aerobic exercise training intervention during pregnancy on brachial artery endothelial function, shear rate and patterns, and forearm blood flow and reactive hyperemia. Twenty-seven pregnant women were recruited and randomized into either a control group (n=11; 31.0 ± 0.7 years), or an exercise intervention group (n=16; 32.6 ± 0.9 years; NCT02948439). The exercise group completed 40 minutes of aerobic exercise (50-70% heart rate reserve) 3-4 times per week, between the second and third trimester of pregnancy. Endothelial function was assessed using flow-mediated dilation (FMD, normalized for shear stress) pre- (16-20 weeks) and post-intervention (34-36 weeks). The exercise training group experienced an attenuated increase in mean arterial pressure (MAP) relative to the control group (∆MAP exercise: +2± 2 mmHg vs. control: +7±3 mmHg; p=0.044) from pre- to post-intervention. % FMD change corrected for shear stress was not different between groups (p=0.460); however, the post occlusion mean flow rate (exercise: 437±32 mL/min vs. control: 364±35 mL/min; p=0.001) and post occlusion anterograde flow rate (exercise: 438±32 mL/min vs. control: 364±46 mL/min;p=0.001) were larger for the exercise training group compared to controls, post-intervention. Although endothelial function was not different between groups, we observed an increase in microcirculatory dilatory capacity, as suggested by the augmented reactive hyperemia in the exercise training group. Novelty: • Endothelial function was not altered with exercise training during pregnancy. • Exercise training did contribute to improved cardiovascular outcomes, which may have been associated with augmented reactive hyperaemia, indicative of increased microcirculatory dilatory capacity.

Sex differences in the vascular function and related mechanisms: role of 17β-estradiol

The incidence of cardiovascular disease (CVD) is lower in premenopausal women but increases with age and menopause compared with similarly aged men. Based on the prevalence of CVD in postmenopausal women, sex hormone-dependent mechanisms have been postulated to be the primary factors responsible for the protection from CVD in premenopausal women. Recent Women’s Health Initiative studies, Cochrane Review studies, the Early Versus Late Intervention Trial with Estradiol Study, and the Kronos Early Estrogen Prevention Study have suggested that beneficial effects of hormone replacement therapy (HRT) are seen in women of <60 yr of age and if initiated within <10 yr of menopause. In contrast, the beneficial effects of HRT are not seen in women of >60 yr of age and if commenced after 10 yr of menopause. The higher incidence of CVD and the failure of HRT in postmenopausal aged women could be partly associated with fundamental differences in the vascular structure and function between men and women and in between pre- and postmenopausal women, respectively. In this regard, previous studies from human and animal studies have identified several sex differences in vascular function and associated mechanisms. The female sex hormone 17β-estradiol regulates the majority of these mechanisms. In this review, we summarize the sex differences in vascular structure, myogenic properties, endothelium-dependent and -independent mechanisms, and the role of 17β-estradiol in the regulation of vascular function.

Exercise as a therapeutic intervention to optimize fetal weight

The Developmental Origins of Health and Disease suggest the in utero environment programs offspring obesity and cardiovascular disease. Therefore, there is a need to implement safe therapeutic interventions that do not involve the intake of medications or biological products during pregnancy that can improve maternal and fetal health. Prenatal exercise is established to promote maternal and fetal health. It is generally recommended that women accumulate at least 150 min per week of moderate-intensity exercise. It has been demonstrated that prenatal exercise maintains healthy weight gain and improves maternal glucose control, maternal cardiac autonomic control, placental efficiency (increases angiogenesis, downregulates genes involved in fatty acid transport and insulin transport across the placenta, and upregulates genes involved in amino acid transport across the placenta), and oxidative stress. These adaptations following exercise improve maternal metabolism and provide adequate uteroplacental perfusion. In this review, we will focus on exercise as a therapeutic intervention to optimize fetal weight. It has been established that prenatal exercise does not increase the risk of having a small for gestational age baby. To the contrary, prenatal exercise has been associated with the prevention of excessive fat accumulation in the newborn and the maintenance of fetal muscle mass.

Brain-derived neurotrophic factor of the cerebral microvasculature: a forgotten and nitric oxide-dependent contributor of brain-derived neurotrophic factor in the brain

AIM

Evidence that brain-derived neurotrophic factor (BDNF), a neurotrophin largely involved in cognition, is expressed by cerebral endothelial cells led us to explore in rats the contribution of the cerebral microvasculature to BDNF found in brain tissue and the link between cerebrovascular nitric oxide (NO) and BDNF production.

METHODS

Brain BDNF protein levels were measured before and after in situ removal of the cerebral endothelium that was achieved by brain perfusion with a 0.2% CHAPS (3-[(3-cholamidopropyl) dimethylammonio]-1-propane sulphonate) solution. BDNF protein and mRNA levels as well as levels of endothelial NO synthase phosphorylated at serine 1177 (P-eNOS^ser1177 ) were measured in cerebral microvessel-enriched fractions. These fractions were also exposed to glycerol trinitrate. Hypertension (spontaneously hypertensive rats) and physical exercise training were used as experimental approaches to modulate cerebrovascular endothelial NO production.

RESULTS

CHAPS perfusion resulted in a marked decrease in brain BDNF levels. Hypertension decreased and exercise increased P-eNOS^ser1177 and BDNF protein levels. However, BDNF mRNA levels that were increased by exercise did not change after hypertension. Finally, in vitro exposure of cerebral microvessel-enriched fractions to glycerol trinitrate enhanced BDNF production.

CONCLUSION

These data reveal that BDNF levels measured in brain homogenates correspond for a large part to BDNF present in cerebral endothelial cells and that cerebrovascular BDNF production is dependent on cerebrovascular endothelial eNOS activity. They provide a paradigm shift in the cellular source of brain BDNF and suggest a new approach to improve our understanding of the link between endothelial function and cognition.

Nitric oxide and the cardiovascular system

Nitric oxide (NO) generated by endothelial cells to relax vascular smooth muscle is one of the most intensely studied molecules in the past 25 years. Much of what is known about NO regulation of NO is based on blockade of its generation and analysis of changes in vascular regulation. This approach has been useful to demonstrate the importance of NO in large scale forms of regulation but provides less information on the nuances of NO regulation. However, there is a growing body of studies on multiple types of in vivo measurement of NO in normal and pathological conditions. This discussion will focus on in vivo studies and how they are reshaping the understanding of NO's role in vascular resistance regulation and the pathologies of hypertension and diabetes mellitus. The role of microelectrode measurements in the measurement of [NO] will be considered because much of the controversy about what NO does and at what concentration depends upon the measurement methodology. For those studies where the technology has been tested and found to be well founded, the concept evolving is that the stresses imposed on the vasculature in the form of flow-mediated stimulation, chemicals within the tissue, and oxygen tension can cause rapid and large changes in the NO concentration to affect vascular regulation. All these functions are compromised in both animal and human forms of hypertension and diabetes mellitus due to altered regulation of endothelial cells and formation of oxidants that both damage endothelial cells and change the regulation of endothelial nitric oxide synthase.

Cardiovascular Adaptations to Exercise Training

Aerobic exercise training leads to cardiovascular changes that markedly increase aerobic power and lead to improved endurance performance. The functionally most important adaptation is the improvement in maximal cardiac output which is the result of an enlargement in cardiac dimension, improved contractility, and an increase in blood volume, allowing for greater filling of the ventricles and a consequent larger stroke volume. In parallel with the greater maximal cardiac output, the perfusion capacity of the muscle is increased, permitting for greater oxygen delivery. To accommodate the higher aerobic demands and perfusion levels, arteries, arterioles, and capillaries adapt in structure and number. The diameters of the larger conduit and resistance arteries are increased minimizing resistance to flow as the cardiac output is distributed in the body and the wall thickness of the conduit and resistance arteries is reduced, a factor contributing to increased arterial compliance. Endurance training may also induce alterations in the vasodilator capacity, although such adaptations are more pronounced in individuals with reduced vascular function. The microvascular net increases in size within the muscle allowing for an improved capacity for oxygen extraction by the muscle through a greater area for diffusion, a shorter diffusion distance, and a longer mean transit time for the erythrocyte to pass through the smallest blood vessels. The present article addresses the effect of endurance training on systemic and peripheral cardiovascular adaptations with a focus on humans, but also covers animal data.

Vascular effects of aerobic exercise training in rat adult offspring exposed to hypoxia-induced intrauterine growth restriction

KEY POINTS

Prenatal hypoxia, one of the most common consequences of complicated pregnancies, leads to intrauterine growth restriction (IUGR) and impairs later-life endothelium-dependent vascular function. Early interventions are needed to ultimately reduce later-life risk for cardiovascular disease. Aerobic exercise training has been shown to prevent cardiovascular diseases. Whether exercise can be used as an intervention to reverse the vascular phenotype of this susceptible population is unknown. Aerobic exercise training enhanced endothelium-derived hyperpolarization-mediated vasodilatation in gastrocnemius muscle arteries in male IUGR offspring, and did not improve nitric oxide-mediated vasodilatation in IUGR offspring. Understanding the mechanisms by which exercise impacts the cardiovascular system in a susceptible population and the consideration of sexual dimorphism is essential to define whether exercise could be used as a preventive strategy in this population.

ABSTRACT

Hypoxia in utero is a critical insult causing intrauterine growth restriction (IUGR). Adult offspring born with hypoxia-induced IUGR have impaired endothelium-dependent vascular function. We tested whether aerobic exercise improves IUGR-induced endothelial dysfunction. Pregnant Sprague-Dawley rats were exposed to control (21% oxygen) or hypoxic (11% oxygen) conditions from gestational day 15 to 21. Male and female offspring from normoxic and hypoxic (IUGR) pregnancies were randomized at 10 weeks of age to either an exercise-trained or sedentary group. Exercise-trained rats ran on a treadmill for 30 min at 20 m min(-1) , 5 deg gradient, 5 days week(-1) , for 6 weeks. Concentration-response curves to phenylephrine and methylcholine were performed in second order mesenteric and gastrocnemius muscle arteries, in the presence or absence of l-NAME (100 μm), MnTBAP (peroxynitrite scavenger; 10 μm), apamin (0.1 μm) and TRAM-34 (an intermediate-conductance calcium-activated potassium channel blocker; 10 μm), or indomethacin (5 μm). In adult male IUGR offspring, prenatal hypoxia had no effect on total vasodilator responses in either vascular bed. Aerobic exercise training in IUGR males, however, improved endothelium-derived hyperpolarization (EDH)-mediated vasodilatation in gastrocnemius muscle arteries. Female IUGR offspring had reduced NO-mediated vasodilatation in both vascular beds, along with decreased total vasodilator responses and increased prostaglandin-mediated vasoconstriction in gastrocnemius muscle arteries. In contrast to males, aerobic exercise training in IUGR female offspring had no effect on either vascular bed. Exercise may not prove to be a beneficial therapy for specific vascular pathways affected by prenatal hypoxia, particularly in female offspring.

Hypertension alters phosphorylation of VASP in brain endothelial cells

Hypertension impairs cerebral vascular function. Vasodilator-stimulated phosphoprotein (VASP) mediates active reorganization of the cytoskeleton via membrane ruffling, aggregation and tethering of actin filaments. VASP regulation of endothelial barrier function has been demonstrated by studies using VASP(-/-) animals under conditions associated with tissue hypoxia. We hypothesize that hypertension regulates VASP expression and/or phosphorylation in endothelial cells, thereby contributing to dysfunction in the cerebral vasculature. Because exercise has direct and indirect salutary effects on vascular systems that have been damaged by hypertension, we also investigated the effect of exercise on maintenance of VASP expression and/or phosphorylation. We used immunohistochemistry, Western blotting and immunocytochemistry to examine the effect of hypertension on VASP expression and phosphorylation in brain endothelial cells in normotensive [Wistar-Kyoto (WKY)] and spontaneously hypertensive (SH) rats under normal and exercise conditions. In addition, we analyzed VASP regulation in normoxia- and hypoxia-induced endothelial cells. Brain endothelial cells exhibited significantly lower VASP immunoreactivity and phosphorylation at the Ser157 residue in SHR versus WKY rats. Exercise reversed hypertension-induced alterations in VASP phosphorylation. Western blotting and immunocytochemistry indicated reduction in VASP phosphorylation in hypoxic versus normoxic endothelial cells. These results suggest that diminished VASP expression and/or Ser157 phosphorylation mediates endothelial changes associated with hypertension and exercise may normalize these changes, at least in part, by restoring VASP phosphorylation.

Endothelial dysfunction in femoral artery of the hypertensive rats is nitric oxide independent

This study examined nitric oxide (NO) production, oxidative load and endothelium-dependent relaxation (NO-dependent and NO-independent) in adult male borderline hypertensive (BHR) and spontaneously hypertensive (SHR) rats as compared to normotensive Wistar-Kyoto (WKY) rats. Systolic blood pressure (BP) was determined by tail-cuff. NO production was determined by conversion of [(3)H]-L-arginine. Conjugated dienes (CD) and concentrations of thiobarbituric acid-reactive substances (TBARS) were measured for assessment of oxidative load. Vascular function was investigated in rings of the femoral artery (FA) using a wire myograph. BP of WKY, BHR and SHR was 106+/-2, 143+/-3 and 191+/-3 mm Hg, respectively (p<0.01 for each). Significant left ventricle (LV) hypertrophy and elevated levels of CD and TBARS in the LV were present in BHR and SHR as compared to WKY. NO production was elevated significantly in the aorta of BHR and SHR vs. WKY as well as in the LV of SHR vs. WKY. Acetylcholine (ACh)-induced relaxation of the FA was reduced significantly in both BHR and SHR vs. WKY. The NO-dependent component of ACh-induced relaxation had increasing tendency in hypertensive groups and it correlated positively with BP. The NO-independent component of vasorelaxation was reduced significantly in BHR and SHR vs. WKY and it correlated negatively with BP. In conclusion, the results showed that endothelial dysfunction in the experimental model of borderline hypertensive and hypertensive rats is NO-independent. The results suggest that borderline hypertension represents a risk of other cardiovascular disorders which is qualitatively similar to that of fully developed hypertension.

Short-term administration of alibernet red wine extract failed to affect blood pressure and to improve endothelial function in young normotensive and spontaneously hypertensive rats

As wine polyphenols were shown to possess many positive effects in mammals, including improvement of vascular function, this study investigated the effect of the Slovak Alibernet red wine extract (AWE) on blood pressure and vascular function in young normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats. Six weeks old, male, WKY and SHR were treated with AWE for three weeks at the dose of 24.2 mg/kg/day. Blood pressure (BP), determined by tail-cuff plethysmography, was significantly elevated in SHR vs. WKY and AWE failed to affect it. Lipid peroxidation was evaluated by determination of thiobarbituric acid-reactive substances. Vascular function was assessed in rings of the femoral artery using Mulvany-Halpern's myograph. Maximal endothelium-dependent acetylcholine (ACh)-induced relaxation was reduced in control SHR vs. WKY rats by approximately 9.3 %, which was associated with a significant decrease of its NO-independent component. AWE failed to affect maximal ACh-induced relaxation, both its NO-dependent and independent components, compared to controls of the same genotype. AWE however reduced lipid peroxidation in the left ventricle of both WKY and SHR and in the liver of SHR. In conclusion, three-week administration of AWE failed to reduce BP and to improve endothelial function in the femoral arteries of both genotypes investigated.

Aerobic exercise reduces oxidative stress and improves vascular changes of small mesenteric and coronary arteries in hypertension

BACKGROUND AND PURPOSE

Regular physical activity is an effective non-pharmacological therapy for prevention and control of hypertension. We investigated the effects of aerobic exercise training in vascular remodelling and in the mechanical and functional alterations of coronary and small mesenteric arteries from spontaneously hypertensive rats (SHR).

EXPERIMENTAL APPROACH

Normotensive Wistar Kyoto (WKY), SHR and SHR trained on a treadmill for 12 weeks were used to evaluate vascular structural, mechanical and functional properties.

KEY RESULTS

Exercise did not affect lumen diameter, wall thickness and wall/lumen ratio but reduced vascular stiffness of coronary and mesenteric arteries from SHR. Exercise also reduced collagen deposition and normalized altered internal elastic lamina organization and expression of MMP-9 in mesenteric arteries from SHR. Exercise did not affect contractile responses of coronary arteries but improved the endothelium-dependent relaxation in SHR. In mesenteric arteries, training normalized the increased contractile responses induced by U46619 and by high concentrations of acetylcholine. In vessels from SHR, exercise normalized the effects of the NADPH oxidase inhibitor apocynin and the NOS inhibitor l-NAME in vasodilator or vasoconstrictor responses, normalized the increased O(2) (-) production and the reduced Cu/Zn superoxide dismutase expression and increased NO production.

CONCLUSIONS AND IMPLICATIONS

Exercise training of SHR improves endothelial function and vascular stiffness in coronary and small mesenteric arteries. This might be related to the concomitant decrease of oxidative stress and increase of NO bioavailability. Such effects demonstrate the beneficial effects of exercise on the vascular system and could contribute to a reduction in blood pressure.