Short-term regular aerobic exercise reduces oxidative stress produced by acute in the adipose microvasculature

Physiological Mechanisms Driving Microcirculatory Enhancement: the Impact of Physical Activity

Background

Physical activity induces many beneficial adaptive changes to blood vessel microcirculation, ultimately improving both health and exercise performance. This positions it an effective non-pharmacological therapeutic approach for the rehabilitation of patients with various chronic diseases. Understanding the impact of different types of physical activities on microcirculation and elucidating their physiological mechanisms is crucial for optimizing clinical practice.

Methods

A comprehensive literature search was performed across multiple databases including PubMed, EBSCO, ProQuest, and Web of Science. Following a rigorous screening process, 48 studies were selected for inclusion into the study.

Results

Existing studies demonstrate that various forms of physical activity facilitate multiple positive adaptive changes at the microcirculation level. These include enhanced microvascular dilation-driven by endothelial cell factors and mechanical stress on blood vessels-as well as increased capillary density. The physiological mechanisms behind these improvements involve the neurohumoral regulation of endothelial cell factors and hormones, which are crucial for these positive effects. Physical activity also ameliorates inflammation markers and oxidative stress levels, upregulates the expression of silent information regulator 2 homolog 3, genes for hypoxia-inducible factors under hypoxic conditions, and induces favorable changes in multiple hemodynamic and hemorheological parameters. These structural and functional adaptations optimize myocardial blood flow regulation during exercise and improve both oxygen transport and utilization capacity, which are beneficial for the rehabilitation of chronic disease patients.

Conclusions

Our provides a reference for using physical activity as a non-pharmacological intervention for patients with chronic conditions. This framework includes recommendations on exercise types, intensity, frequency, and duration. Additionally, we summarize the physiological mechanisms through which physical activity improves microcirculation, which can inform clinical decision-making.

Impairment of microvascular endothelial Kir2.1 channels contributes to endothelial dysfunction in human hypertension

Hypertension is associated with decreased endothelial function through reduced contributions of nitric oxide (NO). We previously discovered that flow-induced NO production in resistance arteries of mice and humans critically depends on endothelial inwardly rectifying K+ (Kir2.1) channels. The goal of this study was to establish whether these channels contribute to the impairment of endothelial function, measured by flow-induced vasodilation (FIV) in peripheral resistance arteries of humans with hypertension. We measured FIV in vessels isolated from subcutaneous fat biopsies from 32 subjects: normotensive [n = 19; 30.6 ± 9.8 yr old; systolic blood pressure (SBP): 115.2 ± 7 mmHg; diastolic blood pressure (DBP): 75.3 ± 5.7 mmHg] and hypertensive (n = 13; 45.3 ± 15.3 yr old; SBP: 146.1 ± 15.2 mmHg; DBP: 94.4 ± 6.9 mmHg). Consistent with previous studies, we find that FIV is impaired in hypertensive adults as demonstrated by a significant reduction in FIV when compared with the normotensive adults. Furthermore, our data suggest that the impairment of FIV in hypertensive adults is partially attributed to a reduction in Kir2.1-dependent vasodilation. Specifically, we show that blocking Kir2.1 with ML133 or functionally downregulating Kir2.1 with endothelial-specific adenoviral vector containing dominant-negative Kir2.1 (dnKir2.1) result in a significant reduction in FIV in normotensive subjects but with a smaller effect in hypertensive adults. The Kir2.1-dependent vasodilation was negatively correlated to both SBP and DBP, indicating that the Kir2.1 contribution to FIV decreases as blood pressure increases. In addition, we show that exposing vessels from normotensive adults to acute high-pressure results in loss of Kir2.1 contribution, as high pressure impairs vasodilation. No effect is seen when these vessels were incubated with dnKir2.1. Overexpressing wtKir2.1 in the endothelium resulted in some improvement in vasodilation in arteries from all participants, with a greater recovery in hypertensive adults. Our data suggest that hypertension-induced suppression of Kir2.1 is an important mechanism underlying endothelial dysfunction in hypertension.NEW & NOTEWORTHY Impairment of endothelial function under high blood pressure is linked to the loss of inwardly rectifying K+ (Kir2.1) channels activity in human resistance arteries, leading to a reduction in flow-induced vasodilation and possibly leading to a vicious cycle between elevation of blood pressure, and further impairment of Kir2.1 function and flow-induced vasodilation.

Visceral adipose of obese mice inhibits endothelial inwardly rectifying K+ channels in a CD36-dependent fashion

Obesity imposes deficits on adipose tissue and vascular endothelium, yet the role that distinct adipose depots play in mediating endothelial dysfunction in local arteries remains unresolved. We recently showed that obesity impairs endothelial Kir2.1 channels, mediators of nitric oxide production, in arteries of visceral adipose tissue (VAT), while Kir2.1 function in subcutaneous adipose tissue (SAT) endothelium remains intact. Therefore, we determined if VAT versus SAT from lean or diet-induced obese mice affected Kir2.1 channel function in vitro. We found that VAT from obese mice reduces Kir2.1 function without altering channel expression whereas AT from lean mice and SAT from obese mice had no effect on Kir2.1 function as compared to untreated control cells. As Kir2.1 is well known to be inhibited by fatty acid derivatives and obesity is strongly associated with elevated circulating fatty acids, we next tested the role of the fatty acid translocase CD36 in mediating VAT-induced Kir2.1 dysfunction. We found that the downregulation of CD36 restored Kir2.1 currents in endothelial cells exposed to VAT from obese mice. In addition, endothelial cells exposed to VAT from obese mice exhibited a significant increase in CD36-mediated fatty acid uptake. The importance of CD36 in obesity-induced endothelial dysfunction of VAT arteries was further supported in ex vivo pressure myography studies where CD36 ablation rescued the endothelium-dependent response to flow via restoring Kir2.1 and endothelial nitric oxide synthase function. These findings provide new insight into the role of VAT in mediating obesity-induced endothelial dysfunction and suggest a novel role for CD36 as a mediator of endothelial Kir2.1 impairment.NEW & NOTEWORTHY Our findings suggest a role for visceral adipose tissue (VAT) in the dysfunction of endothelial Kir2.1 in obesity. We further reveal a role for CD36 as a major contributor to VAT-mediated Kir2.1 and endothelial dysfunction, suggesting that CD36 offers a potential target for preventing the early development of obesity-associated cardiovascular disease.

Effects of shear stress on vascular endothelial functions in atherosclerosis and potential therapeutic approaches

Different blood flow patterns in the arteries can alter the adaptive phenotype of vascular endothelial cells (ECs), thereby affecting the functions of ECs and are directly associated with the occurrence of lesions in the early stages of atherosclerosis (AS). Atherosclerotic plaques are commonly found at curved or bifurcated arteries, where the blood flow pattern is dominated by oscillating shear stress (OSS). OSS can induce ECs to transform into pro-inflammatory phenotypes, increase cellular inflammation, oxidative stress response, mitochondrial dysfunction, metabolic abnormalities and endothelial permeability, thereby promoting the progression of AS. On the other hand, the straight artery has a stable laminar shear stress (LSS), which promotes the transformation of ECs into an anti-inflammatory phenotype, improves endothelial cell function, thereby inhibits atherosclerotic progression. ECs have the ability to actively sense, integrate, and convert mechanical stimuli by shear stress into biochemical signals that further induces intracellular changes (such as the opening and closing of ion channels, activation and transcription of signaling pathways). Here we not only outline the relationship between functions of vascular ECs and different forms of fluid shear stress in AS, but also aim to provide new solutions for potential atherosclerotic therapies targeting intracellular mechanical transductions.

Differential effects of obesity on visceral versus subcutaneous adipose arteries: role of shear-activated Kir2.1 and alterations to the glycocalyx

Obesity imposes well-established deficits to endothelial function. We recently showed that obesity-induced endothelial dysfunction was mediated by disruption of the glycocalyx and a loss of Kir channel flow sensitivity. However, obesity-induced endothelial dysfunction is not observed in all vascular beds: visceral adipose arteries (VAAs), but not subcutaneous adipose arteries (SAAs), exhibit endothelial dysfunction. To determine whether differences in SAA versus VAA endothelial function observed in obesity are attributed to differential impairment of Kir channels and alterations to the glycocalyx, mice were fed a normal rodent diet, or a high-fat Western diet to induce obesity. Flow-induced vasodilation (FIV) was measured ex vivo. Functional downregulation of endothelial Kir2.1 was accomplished by transducing adipose arteries from mice and obese humans with adenovirus containing a dominant-negative Kir2.1 construct. Kir function was tested in freshly isolated endothelial cells seeded in a flow chamber for electrophysiological recordings under fluid shear. Atomic force microscopy was used to assess biophysical properties of the glycocalyx. Endothelial dysfunction was observed in VAAs of obese mice and humans. Downregulating Kir2.1 blunted FIV in SAAs, but had no effect on VAAs, from obese mice and humans. Obesity abolished Kir shear sensitivity in VAA endothelial cells and significantly altered the VAA glycocalyx. In contrast, Kir shear sensitivity was observed in SAA endothelial cells from obese mice and effects on SAA glycocalyx were less pronounced. We reveal distinct differences in Kir function and alterations to the glycocalyx that we propose contribute to the dichotomy in SAA versus VAA endothelial function with obesity.NEW & NOTEWORTHY We identified a role for endothelial Kir2.1 in the differences observed in VAA versus SAA endothelial function with obesity. The endothelial glycocalyx, a regulator of Kir activation by shear, is unequally perturbed in VAAs as compared with SAAs, which we propose results in a near complete loss of VAA endothelial Kir shear sensitivity and endothelial dysfunction. We propose that these differences underly the preserved endothelial function of SAA in obese mice and humans.

Cholesterol-Induced Suppression of Endothelial Kir Channels Is a Driver of Impairment of Arteriolar Flow-Induced Vasodilation in Humans

Dyslipidemia-induced endothelial dysfunction is an important factor in the progression of cardiovascular disease; however, the underlying mechanisms are unclear. Our recent studies demonstrated that flow-induced vasodilation (FIV) is regulated by inwardly rectifying K⁺ channels (Kir2.1) in resistance arteries. Furthermore, we showed that hypercholesterolemia inhibits Kir2.1-dependent vasodilation. In this study, we introduced 2 new mouse models: (1) endothelial-specific deletion of Kir2.1 to demonstrate the role of endothelial Kir2.1 in FIV and (2) cholesterol-insensitive Kir2.1 mutant to determine the Kir2.1 regulation in FIV under hypercholesterolemia. FIV was significantly reduced in endothelial-specific Kir2.1 knock-out mouse mesenteric arteries compared with control groups. In cholesterol-insensitive Kir2.1 mutant mice, Kir2.1 currents were not affected by cyclodextrin and FIV was restored in cells and arteries, respectively, with a hypercholesterolemic background. To extend our observations to humans, 16 healthy subjects were recruited with LDL (low-density lipoprotein)-cholesterol ranging from 51 to 153 mg/dL and FIV was assessed in resistance arteries isolated from gluteal adipose. Resistance arteries from participants with >100 mg/dL LDL (high-LDL) exhibited reduced FIV as compared with those participants with <100 mg/dL LDL (low-LDL). A significant negative correlation was observed between LDL cholesterol and FIV in high-LDL. Expressing dominant-negative Kir2.1 in endothelium blunted FIV in arteries from low-LDL but had no further effect on FIV in arteries from high-LDL. The Kir2.1-dependent vasodilation more negatively correlated to LDL cholesterol in high-LDL. Overexpressing wild-type Kir2.1 in endothelium fully recovered FIV in arteries from participants with high-LDL. Our data suggest that cholesterol-induced suppression of Kir2.1 is a major mechanism underlying endothelial dysfunction in hypercholesterolemia.

Differential responses of resistance arterioles to elevated intraluminal pressure in blacks and whites

Black Americans have an earlier onset, higher average blood pressure, and higher rates of hypertension-related mortality and morbidity, compared to whites. The racial difference may be related to microvasculature, the major regulatory site of blood pressure. The goal of this study was to compare the response of resistance vessels to high intraluminal pressure between black and white participants. A total of 38 vessels were obtained from human fat samples [21 black, 17 white; mean age 32 ± 12 yr and body mass index (BMI) 26.9 ± 4.9; between-group P ≥ 0.05] and included in this study. Internal diameter was measured in response to the flow induced by various pressure gradients (Δ10, Δ20, Δ40, Δ60, and Δ100 cmH₂O), and flow-induced dilation (FID) was calculated before and after high intraluminal pressure (150 cmH₂O). Before high intraluminal pressure, FID was not different between blacks and whites (P = 0.112). After exposure to high intraluminal pressure, FID was reduced at every pressure gradient in vessels from blacks (P < 0.001), whereas FID did not change in white participants except at Δ100 cmH₂O. When incubated with the hydrogen peroxide (H₂O₂) scavenger polyethylene glycol-catalase (PEG-catalase), the FID response in vessels from black, but not white, individuals was significantly reduced and the magnitude was higher at normal pressure relative to high pressure. Our findings suggest that the vessels from self-identified black individuals are more susceptible to microvascular dysfunction following transient periods of high intraluminal pressure compared to whites and show greater dependence on H₂O₂ as a main contributor to FID at normal pressures.NEW & NOTEWORTHY Microvascular function regulates blood pressure and may contribute to racial differences in the incidence and prevalence of hypertension and other cardiovascular diseases. Here, we show that using an ex vivo model of resistance arterioles isolated from human gluteal fat tissue, flow-induced dilation is not different between black and white participants. However, when exposed to transient increases in intraluminal pressure, the flow-induced dilation in resistance arterioles from black participants demonstrated greater reductions relative to their white counterparts, indicating a higher sensitivity to pressure change in the microvasculature.

Aerobic exercise training reduces cardiac function and coronary flow-induced vasodilation in mice lacking adiponectin

We tested the hypothesis that adiponectin deficiency attenuates cardiac and coronary microvascular function and prevents exercise training-induced adaptations of the myocardium and the coronary microvasculature in adult mice. Adult wild-type (WT) or adiponectin knockout (adiponectin KO) mice underwent treadmill exercise training or remained sedentary for 8-10 wk. Systolic and diastolic functions were assessed before and after exercise training or cage confinement. Vasoreactivity of coronary resistance arteries was assessed at the end of exercise training or cage confinement. Before exercise training, ejection fraction and fractional shortening were similar in adiponectin KO and WT mice, but isovolumic contraction time was significantly lengthened in adiponectin KO mice. Exercise training increased ejection fraction (12%) and fractional shortening (20%) with no change in isovolumic contraction time in WT mice. In adiponectin KO mice, both ejection fraction (-9%) and fractional shortening (-12%) were reduced after exercise training and these decreases were coupled to a further increase in isovolumic contraction time (20%). In sedentary mice, endothelium-dependent dilation to flow was higher in arterioles from adiponectin KO mice as compared with WT mice. Exercise training enhanced dilation to flow in WT mice but decreased flow-induced dilation in adiponectin KO mice. These data suggest that compensatory mechanisms contribute to the maintenance of cardiac and coronary microvascular function in sedentary mice lacking adiponectin; however, in the absence of adiponectin, cardiac and coronary microvascular adaptations to exercise training are compromised.NEW & NOTEWORTHY We report that compensatory mechanisms contribute to the maintenance of cardiac and coronary microvascular function in sedentary mice in which adiponectin has been deleted; however, when mice lacking adiponectin are subjected to the physiological stress of exercise training, beneficial coronary microvascular and cardiac adaptations are compromised or absent.

Effects of short-term aerobic training versus CPAP therapy on heart rate variability in moderate to severe OSA patients

We compared the effects of 2-month CPAP or exercise training (ET) therapies on the autonomic balance in moderate to severe obstructive sleep apnea (OSA) through heart rate variability (HRV) analysis. Thirty-nine OSA patients were divided into CPAP (n = 18) and ET (n = 21) groups, being further split into hypertensive and non-hypertensive subgroups. All patients were submitted to continuous ECG recordings for HRV analysis. Hemodynamic parameters were recorded by oscillometry. Excessive daytime sleepiness and sleep quality were assessed through the Epworth Sleepiness Scale and the Pittsburgh questionnaire, respectively. ET decreased systolic arterial pressure in hypertensive and non-hypertensive participants when compared to baseline values, whereas diastolic arterial pressure was decreased only in non-hypertensive ones. CPAP had no effect over hemodynamic parameters in either subgroup. ET significantly increased the HRV parameters SDNN and pNN50 in non-hypertensive participants, while reducing the LF/HF ratio in both subgroups. CPAP significantly decreased SDNN in both subgroups. ET significantly decreased excessive daytime sleepiness in both subgroups, but did not affect sleep quality. CPAP significantly improved sleep quality in both subgroups, although global scores were still those of poor sleepers, while excessive daytime sleepiness was normalized only in hypertensive patients. In conclusion, while short-term ET modulated different HRV parameters, leading to a predominant vagal tone in the cardiac sympathovagal balance and decreasing blood pressure in moderate to severe OSA, short-term CPAP had next to no effect in these parameters. We believe ET should be considered as an adjunct interventional strategy in the conservative management of hypertensive or non-hypertensive OSA patients.

Impairment of Flow-Sensitive Inwardly Rectifying K+ Channels via Disruption of Glycocalyx Mediates Obesity-Induced Endothelial Dysfunction

OBJECTIVE

To determine if endothelial dysfunction in a mouse model of diet-induced obesity and in obese humans is mediated by the suppression of endothelial Kir (inwardly rectifying K⁺) channels. Approach and Results: Endothelial dysfunction, observed as reduced dilations to flow, occurred after feeding mice a high-fat, Western diet for 8 weeks. The functional downregulation of endothelial Kir2.1 using dominant-negative Kir2.1 construct resulted in substantial reductions in the response to flow in mesenteric arteries of lean mice, whereas no effect was observed in arteries of obese mice. Overexpressing wild-type-Kir2.1 in endothelium of arteries from obese mice resulted in full recovery of the flow response. Exposing freshly isolated endothelial cells to fluid shear during patch-clamp electrophysiology revealed that the flow-sensitivity of Kir was virtually abolished in cells from obese mice. Atomic force microscopy revealed that the endothelial glycocalyx was stiffer and the thickness of the glycocalyx layer reduced in arteries from obese mice. We also identified that the length of the glycocalyx is critical to the flow-activation of Kir. Overexpressing Kir2.1 in endothelium of arteries from obese mice restored flow- and heparanase-sensitivity, indicating an important role for heparan sulfates in the flow-activation of Kir. Furthermore, the Kir2.1-dependent component of flow-induced vasodilation was lost in the endothelium of resistance arteries of obese humans obtained from biopsies collected during bariatric surgery.

CONCLUSIONS

We conclude that obesity-induced impairment of flow-induced vasodilation is attributed to the loss of flow-sensitivity of endothelial Kir channels and propose that the latter is mediated by the biophysical alterations of the glycocalyx.

Tetrahydrobiopterin Restores Microvascular Dysfunction in Young Adult Binge Drinkers

BACKGROUND

Repeated binge drinking is associated with reduced microvascular function. However, microvascular responses to pathophysiological stimulus such as high pressure as well as potential mechanisms that underlie binge-induced microvascular dysfunction are unknown. Therefore, using an ex vivo experimental model, we examined microvascular responses following a brief period of high intraluminal pressure in isolated arterioles from young adults who have a history of repeated binge drinking. In addition, we examined whether the application of the endothelial nitric oxide synthase cofactor, tetrahydrobiopterin, would restore microvascular function in response to flow and high intraluminal pressure in young adult binge drinkers.

METHODS

Isolated subcutaneous adipose arterioles were obtained from young adult binge drinkers (BD; n = 14), moderate drinkers (MODs; n = 10), and alcohol abstainers (ABs; n = 12; mean age: 23.7 ± 0.5 years; and body mass index: 23.4 ± 0.4 kg/m2 ). Arteriolar flow-induced dilation (FID, pressure gradient: ∆10 to 100 cm H2 O) was measured before and after acute high intraluminal pressure with and without tetrahydrobiopterin.

RESULTS

Before high pressure, FID at Δ60 and Δ100 cm H2 O pressure gradient in BDs was 14% lower and 18% lower, respectively, than ABs (p < 0.05), while MODs and ABs had similar FID across all pressure gradients (p ≥ 0.2). After high pressure, FID in BDs was further reduced by 10% (p < 0.0005) and this impairment was ameliorated by the treatment of tetrahydrobiopterin (4 to 26% higher, p < 0.005). In contrast, FID after high pressure did not change in MODs and ABs (p ≥ 0.5).

CONCLUSIONS

Microvascular dysfunction in young adult binge drinkers may be exacerbated with acute pathophysiological stimulus. These binge-induced dysfunctions may be reversed by tetrahydrobiopterin, which suggests a role of oxidative stress and/or uncoupled endothelial nitric oxide synthase in binge drinking.

Hydration Status and Cardiovascular Function

Hypohydration, defined as a state of low body water, increases thirst sensations, arginine vasopressin release, and elicits renin–angiotensin–aldosterone system activation to replenish intra- and extra-cellular fluid stores. Hypohydration impairs mental and physical performance, but new evidence suggests hypohydration may also have deleterious effects on cardiovascular health. This is alarming because cardiovascular disease is the leading cause of death in the United States. Observational studies have linked habitual low water intake with increased future risk for adverse cardiovascular events. While it is currently unclear how chronic reductions in water intake may predispose individuals to greater future risk for adverse cardiovascular events, there is evidence that acute hypohydration impairs vascular function and blood pressure (BP) regulation. Specifically, acute hypohydration may reduce endothelial function, increase sympathetic nervous system activity, and worsen orthostatic tolerance. Therefore, the purpose of this review is to present the currently available evidence linking acute hypohydration with altered vascular function and BP regulation.

Effects of aerobic exercise on vascular function in nondialysis chronic kidney disease: a randomized controlled trial

Endothelial dysfunction and arterial stiffness are nontraditional risk factors of chronic kidney disease (CKD)-related cardiovascular disease (CVD) that could be targeted with exercise. This study investigated the effect of moderate to vigorous aerobic exercise on vascular function in nondialysis CKD. In this randomized, controlled trial, 36 nondialysis patients with CKD (means ± SE, age: 58 ± 2 yr, estimated glomerular filtration rate: 44 ± 2 ml·min-1·1.73 m-2) were allocated to an exercise training (EXT) or control (CON) arm. The EXT group performed 3 × 45 min of supervised exercise per week at 60-85% heart rate reserve for 12 wk, whereas the CON group received routine care. Outcomes were assessed at 0 and 12 wk. The primary outcome, microvascular function, was assessed via cutaneous vasodilation during local heating measured by laser-Doppler flowmetry coupled with microdialysis. Participants were instrumented with two microdialysis fibers for the delivery of 1) Ringer solution and 2) the superoxide scavenger tempol. Conduit artery function was assessed via brachial artery flow-mediated dilation. Aortic pressure waveforms and pulse wave velocity were acquired with tonometry and oscillometry. Microvascular function improved after EXT (week 0 vs.week 12, EXT: 87 ± 2% vs. 91 ± 2% and CON: 86 ± 2% vs. 84 ± 3%, P = 0.03). At baseline, pharmacological delivery of tempol improved microvascular function (Ringer solution vs. tempol: 86 ± 1% vs. 90 ± 1%, P = 0.02) but was no longer effective after EXT (91 ± 2% vs. 87 ± 1%, P = 0.2), suggesting that an improved redox balance plays a role in EXT-related improvements. Brachial artery flow-mediated dilation was maintained after EXT (EXT: 2.6 ± 0.4% vs. 3.8 ± 0.8% and CON: 3.5 ± 0.6% vs. 2.3 ± 0.4%, P = 0.02). Central arterial hemodynamics and arterial stiffness were unchanged after EXT. Aerobic exercise improved microvascular function and maintained conduit artery function and should be considered as an adjunct therapy to reduce CVD risk in CKD.

The Effect of 1 Week of a Multi-ingredient Dietary Preworkout Supplement on Resting and Postacute Resistance Exercise Vascular Function

Dietary preworkout supplements are popular among recreational exercisers and athletes. However, the effects of these supplements on the vasculature, both at rest and during exercise, are not well studied. Therefore, the purpose of this study was to determine the effect of 1 week of supplementation with a multi-ingredient dietary preworkout supplement on measures of vascular function at rest and immediately following acute resistance exercise in young, recreationally active adults. Twelve participants (9 males and 3 females; mean ± SD: age = 24.5 ± 3.4 years and body mass index = 24.3 ± 4.7 kg/m²) completed this double-blind, randomized, crossover design study. After familiarization, participants were randomized to either a taste-matched placebo or the preworkout supplement for 1 week preceding the testing visits. Participants underwent measures of vascular function, including brachial artery flow-mediated dilation, measures of central and peripheral blood pressure, and measures of arterial stiffness via pulse wave analysis and pulse wave velocity. All measures were taken at rest and immediately following an acute bilateral leg press exercise session. Resting and postacute exercise flow-mediated dilation, blood pressure, and arterial stiffness were similar between the placebo and the preworkout supplement visits. One week of multi-ingredient preworkout supplementation does not affect vascular function at rest or in response to an acute bout of resistance exercise in young, healthy, recreationally active individuals.

Exercise during hemodialysis does not affect the phenotype or prothrombotic nature of microparticles but alters their proinflammatory function

Hemodialysis patients have dysfunctional immune systems, chronic inflammation and comorbidity-associated risks of cardiovascular disease (CVD) and infection. Microparticles are biologically active nanovesicles shed from activated endothelial cells, immune cells, and platelets; they are elevated in hemodialysis patients and are associated with chronic inflammation and predictive of CVD mortality in this group. Exercise is advocated in hemodialysis to improve cardiovascular health yet acute exercise induces an increase in circulating microparticles in healthy populations. Therefore, this study aimed to assess acute effect of intradialytic exercise (IDE) on microparticle number and phenotype, and their ability to induce endothelial cell reactive oxygen species (ROS) in vitro. Eleven patients were studied during a routine hemodialysis session and one where they exercised in a randomized cross-over design. Microparticle number increased during hemodialysis (2064-7071 microparticles/μL, P < 0.001) as did phosphatidylserine+ (P < 0.05), platelet-derived (P < 0.01) and percentage procoagulant neutrophil-derived microparticles (P < 0.05), but this was not affected by IDE. However, microparticles collected immediately and 60 min after IDE (but not later) induced greater ROS generation from cultured endothelial cells (P < 0.05), suggesting a transient proinflammatory event. In summary IDE does not further increase prothrombotic microparticle numbers that occurs during hemodialysis. However, given acute proinflammatory responses to exercise stimulate an adaptation toward a circulating anti-inflammatory environment, microparticle-induced transient increases of endothelial cell ROS in vitro with IDE may indicate the potential for a longer-term anti-inflammatory adaptive effect. These findings provide a crucial evidence base for future studies of microparticles responses to IDE in view of the exceptionally high risk of CVD in these patients.

Statistical considerations in reporting cardiovascular research

The problem of inadequate statistical reporting is long standing and widespread in the biomedical literature, including in cardiovascular physiology. Although guidelines for reporting statistics have been available in clinical medicine for some time, there are currently no guidelines specific to cardiovascular physiology. To assess the need for guidelines, we determined the type and frequency of statistical tests and procedures currently used in the American Journal of Physiology-Heart and Circulatory Physiology. A PubMed search for articles published in the American Journal of Physiology-Heart and Circulatory Physiology between January 1, 2017, and October 6, 2017, provided a final sample of 146 articles evaluated for methods used and 38 articles for indepth analysis. The t-test and ANOVA accounted for 71% (212 of 300 articles) of the statistical tests performed. Of six categories of post hoc tests, Bonferroni and Tukey tests were used in 63% (62 of 98 articles). There was an overall lack in details provided by authors publishing in the American Journal of Physiology-Heart and Circulatory Physiology, and we compiled a list of recommended minimum reporting guidelines to aid authors in preparing manuscripts. Following these guidelines could substantially improve the quality of statistical reports and enhance data rigor and reproducibility.

Regular Aerobic, Resistance, and Cross-Training Exercise Prevents Reduced Vascular Function Following a High Sugar or High Fat Mixed Meal in Young Healthy Adults

The postprandial state can negatively influence flow mediated dilation (FMD), a predictor of atherosclerosis and cardiovascular disease. This investigation was designed to determine the effect of regular aerobic and/or resistance exercise on postprandial FMD after a high sugar or high fat mixed meal. Forty-five healthy participants were recruited from one of four groups: lean sedentary (SED), runners, weight lifters, and cross-trainers. Participants were randomly crossed over to a high sugar meal (HSM) and a high fat mixed meal (HFMM; both fat and carbohydrate). Pre-and postprandial endothelial function was assessed for both meals using brachial artery FMD. Plasma lipids, insulin, glucose, hs-CRP, and SOD were also measured with both meals. Endothelium-independent dilation was determined via sublingual nitroglycerin. Brachial artery FMD was reduced in SED following the HSM (9.9 ± 0.9% at baseline, peak reduction at 60 min 6.5 ± 1.0%) and the HFMM (9.4 ± 0.9% at baseline, peak reduction at 120 min 5.9 ± 1.2%; P < 0.05 for both, Mean ± SEM). There was no change in FMD after either HSM or HFMM in runners, weight lifters, and cross-trainers. Post-prandial increases in blood glucose, insulin and triglycerides were less pronounced in the exercisers compared to SED. In addition, exercisers presented lower baseline plasma hs-CRP and higher SOD activity. Nitroglycerin responses were similar among groups. These results suggest that endothelial function is reduced in sedentary adults after a HSM or HFMM, but not in regular aerobic or resistance exercisers. This response may be due to favorable postprandial metabolic responses or lower postprandial levels of inflammation and oxidative stress. These findings may help to explain the cardioprotective effect of exercise.

Hypercholesterolemia-Induced Loss of Flow-Induced Vasodilation and Lesion Formation in Apolipoprotein E-Deficient Mice Critically Depend on Inwardly Rectifying K+ Channels

BACKGROUND

Hypercholesterolemia-induced decreased availability of nitric oxide (NO) is a major factor in cardiovascular disease. We previously established that cholesterol suppresses endothelial inwardly rectifying K+ (Kir) channels and that Kir2.1 is an upstream mediator of flow-induced NO production. Therefore, we tested the hypothesis that suppression of Kir2.1 is responsible for hypercholesterolemia-induced inhibition of flow-induced NO production and flow-induced vasodilation (FIV). We also tested the role of Kir2.1 in the development of atherosclerotic lesions.

METHODS AND RESULTS

Kir2.1 currents are significantly suppressed in microvascular endothelial cells exposed to acetylated-low-density lipoprotein or isolated from apolipoprotein E-deficient (Apoe-/- ) mice and rescued by cholesterol depletion. Genetic deficiency of Kir2.1 on the background of hypercholesterolemic Apoe-/- mice, Kir2.1+/-/Apoe-/- exhibit the same blunted FIV and flow-induced NO response as Apoe-/- or Kir2.1+/- alone, but while FIV in Apoe-/- mice can be rescued by cholesterol depletion, in Kir2.1+/-/Apoe-/- mice cholesterol depletion has no effect on FIV. Endothelial-specific overexpression of Kir2.1 in arteries from Apoe-/- and Kir2.1+/-/Apoe-/- mice results in full rescue of FIV and NO production in Apoe-/- mice with and without the addition of a high-fat diet. Conversely, endothelial-specific expression of dominant-negative Kir2.1 results in the opposite effect. Kir2.1+/-/Apoe-/- mice also show increased lesion formation, particularly in the atheroresistant area of descending aorta.

CONCLUSIONS

We conclude that hypercholesterolemia-induced reduction in FIV is largely attributable to cholesterol suppression of Kir2.1 function via the loss of flow-induced NO production, whereas the stages downstream of flow-induced Kir2.1 activation appear to be mostly intact. Kir2.1 channels also have an atheroprotective role.

Microvascular Vasodilator Plasticity After Acute Exercise

Endothelium-dependent vasodilation is reduced after acute exercise or after high intraluminal pressure in isolated arterioles from sedentary adults but not in arterioles from regular exercisers. The preserved vasodilation in arterioles from exercisers is hydrogen peroxide (H2O2) dependent, whereas resting dilation is nitric oxide (NO) dependent. We hypothesize chronic exercise elicits adaptations allowing for maintained vasodilation when NO bioavailability is reduced.

Microvascular Adaptations to Exercise: Protective Effect of PGC-1 Alpha

BACKGROUND

Sedentary behavior and obesity are major risk factors for cardiovascular disease. Regular physical activity has independent protective effects on the cardiovascular system, but the mechanisms responsible remain elusive. Recent studies suggest that the protein peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) participates in the response to exercise training. We hypothesized that the arterioles of athletes maintain dilation to flow despite combined inhibition of multiple vasodilators, but loss of PGC-1α renders these vessels susceptible to inhibition of a single vasodilator pathway. In addition, arterioles from overweight and obese individuals will display an an exercise-like phenotype when PGC-1α is activated.

METHODS

Isolated arterioles from exercise-trained (ET) and from mildly overweight or obese subjects (body mass index >25) were cannulated, and changes in lumen diameter in response to graded increases in flow were recorded in the absence and presence of compounds that inhibit various endothelium-dependent vasodilators.

RESULTS

Microvessels of ET subjects displayed robust dilation that could not be inhibited through targeting the combination of nitric oxide, prostaglandins, and hydrogen peroxide, but were inhibited via interference with membrane hyperpolarization. Loss of PGC-1α (siRNA) in the microcirculation of ET subjects eliminates this vasodilatory robustness rendering vessels susceptible to blockade of H2O2 alone. Pharmacological activation of PGC-1α with alpha-lipoic acid in isolated microvessels from sedentary, overweight, and obese subjects increases arteriolar resistance to vasodilator blockade and protects against acute increases in intraluminal pressure.

CONCLUSIONS

These findings suggest that the microvascular adaptations to exercise training, and the exercise-induced protection against acute vascular stress in overweight/obese subjects, are mediated by PGC-1α.

Guidelines for authors and reviewers on antibody use in physiology studies

Antibody use is a critical component of cardiovascular physiology research, and antibodies are used to monitor protein abundance (immunoblot analysis) and protein expression and localization (in tissue by immunohistochemistry and in cells by immunocytochemistry). With ongoing discussions on how to improve reproducibility and rigor, the goal of this review is to provide best practice guidelines regarding how to optimize antibody use for increased rigor and reproducibility in both immunoblot analysis and immunohistochemistry approaches.

Listen to this article’s corresponding podcast at http://ajpheart.podbean.com/e/guidelines-on-antibody-use-in-physiology-studies/.