Microvascular Endothelial Dysfunction Research Articles

Abstract 4123637: Prevalence of Invasively Diagnosed Coronary Endothelial Dysfunction in Patients with Chest Pain and Normal Coronary Flow Reserve: The Systematically Missed Diagnosis on Non-invasive Testing

Background: Invasive coronary reactivity testing (CRT) is the gold standard for comprehensive assessment of coronary endothelial and microvascular dysfunction in patients with angina and non-obstructive CAD (ANOCA). Non-invasive imaging modalities (PET and CMR) have emerged as potential alternatives. However, due to the inability to systemically administer acetylcholine, patients with normal coronary flow reserve (CFR) but abnormal endothelial function on invasive Ach testing are systemically missed on non-invasive testing. We aimed to assess the prevalence of coronary endothelial dysfunction in ANOCA patients with normal CFR. Methods: Consecutive patients undergoing CRT at our institution were included. Those with normal adenosine-based CFR (>2.5), were further stratified as having normal coronary endothelial function (NEF, <20% epicardial coronary diameter constriction and >50% increase in coronary blood flow in response to ACh) vs abnormal endothelial function (AEF, >20% epicardial coronary diameter constriction and/or <50% increase in coronary blood flow in response to Ach). We then assessed the proportion of AEF patients who would have been otherwise diagnosed with normal coronary physiology based on CFR alone on non-invasive testing. Results: 37 patients underwent CRT. Mean age was 55 years ± 25, 68% were females. 25 out of 37 patients (68%) had normal CFR. Of those patients, 17 (68%) patients had AEF. Distribution of coronary epicardial vs microvascular endothelial dysfunction is represented in Fig. 1. Conclusion: 68% of ANOCA patients with normal CFR had coronary epicardial and/or microvascular endothelial dysfunction and would have otherwise been labeled as ‘normal coronary physiology’ by non-invasive microvascular function testing. Our findings re-enforce the need for comprehensive invasive CRT for accurate comprehensive diagnosis of patients with ANOCA.

Skeletal muscle reactive oxygen species and microvascular endothelial function in age-related hypertension: a study protocol using a microdialysis technique.

Increased reactive oxygen species (ROS) generation and microvascular endothelial disruptions occur with natural ageing, but often transpire before the detection of cardiometabolic conditions including hypertension. Age-related increases in blood pressure are driven by complex systemic changes with poorly understood integrated mechanisms. The deconditioning experienced by ageing skeletal muscle from mid-life is associated with reduced microvascular blood flow and increased peripheral resistance, suggesting that vasodilatory decrements in the muscle may precede the age-related increases in blood pressure. Structural and functional changes within the vascular and skeletal muscle systems with advancing age can influence redox homeostasis, and vice versa, further compounding microvascular endothelial dysfunction. Therefore, comparisons between the microvascular environments of healthy and hypertensive cohorts can provide insights into the changes that occur during significant periods of functional decline. This comprehensive study protocol describes a microdialysis technique to assess the interactions of microvascular health and functional changes in the muscle, which currently cannot be otherwise addressed. Here, we detail an experimental protocol to simultaneously detect skeletal muscle ROS (H2O2 and indirect O2 -), determine nutritive blood flow and assess microvascular endothelial function in response to acetylcholine stimulation. We expect that healthy middle-aged individuals should not have increased ROS generation in the muscle at rest, compared to their hypertensive or older counterparts, but may exhibit perturbed microvascular function. The described technique allows for intricate exploration of microvascular physiology that will provide a critically novel insight into benchmarking potential age-related mechanisms involved in the development of age-related hypertension, and aid in early identification and prevention. KEY POINTS: Increased reactive oxygen species (ROS) production and microvascular endothelial dysfunction precede the onset of age-related cardiometabolic and vascular conditions such as hypertension. The profound structural and functional changes that occur within the vasculature and in skeletal muscle from middle age prompt a need to mechanistically explore the microvascular environment in healthy and hypertensive individuals. Using a novel microdialysis technique, we detail an experimental protocol to simultaneously detect skeletal muscle ROS (H2O2 and indirect O2 -), determine nutritive blood flow and assess microvascular endothelial function in response to acetylcholine stimulation. With this technique and study protocol, we can reveal functional insights into potential perturbations in ROS generation at rest and the microvascular endothelium, which play important roles in the development of age-related hypertension.

Distribution of microvascular endothelial function in different clinical and non-clinical settings in the united states and china

Abstract Background Despite the fact that microvascular (endothelial) dysfunction is associated with various diseases from cardiovascular to kidney, lung, liver, and other medical conditions, it has not been extensively studied in various clinical and non-clinical settings as blood pressure has. Digital Thermal Flowmetry (DTF) of microvascular endothelial function is a new and automated technique based on monitoring fingertip temperature fall and rebound during reactive hyperemia. Here we report distributions of microvascular function across (1) CVD patients, (2) wellness and internal medicine clinics, (3) college students, and (4) community-based healthy volunteers in China. Methods A total of 7,907 endothelial function test results were collected from various settings. Blood pressure and heart rate were measured before the tests. The tests were conducted using FDA-approved automated VENDYS devices (Endothelix Inc., Palo Alto, CA). Adjusted maximum temperature rebound was reported as Vascular Reactivity Index (VRI) and compared across different settings. Results VRI in CVD patients, wellness and internal medicine clinics, college students, and Chinese volunteers were (1.25±0.34) (1.53±0.5) (1.86±0.5) (1.95±0.44.) respectively P<0.01. Age was weakly correlated with VRI with the equation age=-0.01 VRI+2.01 (r=0.17 p<0.001) Conclusions To our knowledge, this is the largest database of finger-based endothelial function testing. VRI showed distinct distributions across various clinical and non-clinical settings with CVD patients exhibiting the lowest and Chinese healthy volunteers the highest values. The VRI trend mimics the statistically expected risk trend with CVD patients having the highest and Chinese healthy volunteers having the lowest CVD events risk.Figure 1.

Post-acute COVID-19 syndrome: prevalence of peripheral microvascular endothelial dysfunction and associations with NT-proBNP dynamics

BackgroundPost-acute COVID-19 syndrome (PACS) has been linked to microvascular endothelial dysfunction as a potential underlying pathomechanism and can manifest even following a mild course of the initial infection. Prevalence of microvascular endothelial dysfunction and circulating natriuretic peptides in such PACS patients remains unknown. Methods and resultsThis prospective, cross-sectional cohort study enrolled 92 patients (82% females, median age 48 years) with PACS. Reactive hyperemia index (RHI) was evaluated with peripheral arterial tonometry where <1.67 was defined as microvascular endothelial dysfunction, 1.67-2.0 impaired- and >2 normal endothelial function, on average 31 months after the acute infection. N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels were collected at two different time points within over 1-year span. In total, 41% of PACS subjects had microvascular endothelial dysfunction and 20% had impaired RHI. No major differences in clinical characteristics, routine chemistry laboratory testing or symptom burden were observed across the groups. Only subjects with microvascular endothelial dysfunction and impaired endothelial function had a significant increase in NT-proBNP levels over time and those with larger increase in NT-proBNP had significantly lower RHI. There was a significant correlation between relative or absolute increase in NT-proBNP and RHI, which remained significant in a multivariable adjusted linear regression. ConclusionsPeripheral microvascular endothelial dysfunction was prevalent in a symptomatic PACS population long after recovery from a mild acute infection. Increases in NT-proBNP levels were associated with microvascular endothelial dysfunction, suggesting a link between and providing a foundation for future studies on post viral microvascular endothelial dysfunction in PACS.

Impaired microvascular insulin-dependent dilation in women with a history of gestational diabetes.

Women with a history of gestational diabetes mellitus (GDM) have a significantly greater lifetime risk of developing cardiovascular disease and type 2 diabetes compared with women who had an uncomplicated pregnancy (HC). Microvascular endothelial dysfunction, mediated via reduced nitric oxide (NO)-dependent dilation secondary to increases in oxidative stress, persists after pregnancy complicated by GDM. We examined whether this microvascular dysfunction reduces insulin-mediated vascular responses in women with a history of GDM. We assessed in vivo microvascular endothelium-dependent vasodilator function by measuring cutaneous vascular conductance responses to graded infusions of acetylcholine (10-10-10-1 M) and insulin (10-8-10-4 M) in control sites and sites treated with 15 mM l-NAME [NG-nitro-l-arginine methyl ester; NO-synthase (NOS) inhibitor] or 5 mM l-ascorbate. We also measured protein expression of total endothelial NOS (eNOS), insulin-mediated eNOS phosphorylation, and endothelial nitrotyrosine in isolated endothelial cells from GDM and HC. Women with a history of GDM had reduced acetylcholine (P < 0.001)- and insulin (P < 0.001)-mediated dilation, and the NO-dependent responses to both acetylcholine (P = 0.006) and insulin (P = 0.006) were reduced in GDM compared with HC. Insulin stimulation increased phosphorylated eNOS content in HC (P = 0.009) but had no effect in GDM (P = 0.306). Ascorbate treatment increased acetylcholine (P < 0.001)- and insulin (P < 0.001)-mediated dilation in GDM, and endothelial cell nitrotyrosine expression was higher in GDM compared with HC (P = 0.014). Women with a history of GDM have attenuated microvascular vasodilation responses to insulin, and this attenuation is mediated, in part, by reduced NO-dependent mechanisms. Our findings further implicate increased endothelial oxidative stress in this microvascular insulin resistance.NEW & NOTEWORTHY Women who have gestational diabetes during pregnancy are at a greater risk for cardiovascular disease and type 2 diabetes in the decade following pregnancy. The mechanisms mediating this increased risk are unclear. Herein, we demonstrate that insulin-dependent microvascular responses are reduced in women who had gestational diabetes, despite the remission of glucose intolerance. This reduced microvascular sensitivity to insulin may contribute to increased cardiovascular disease and type 2 diabetes risk in these women.

Multiscale optoacoustic assessment of skin microvascular reactivity in carotid artery disease

Microvascular endothelial dysfunction may provide insights into systemic diseases, such as carotid artery disease. Raster-scan optoacoustic mesoscopy (RSOM) can produce images of skin microvasculature during endothelial dysfunction challenges via numerous microvascular features. Herein, RSOM was employed to image the microvasculature of 26 subjects (13 patients with single carotid artery disease, 13 healthy participants) to assess the dynamics of 18 microvascular features at three scales of detail, i.e., the micro- (<100μm), meso- (≈100-1000μm) and macroscale (>1000μm), during post-occlusive reactive hyperemia challenges. The proposed analysis identified a subgroup of 9 features as the most relevant to carotid artery disease because they achieved the most efficient classification (AUC of 0.93) between the two groups in the first minute of hyperemia (sensitivity/specificity: 0.92/0.85). This approach provides a non-invasive solution to microvasculature quantification in carotid artery disease, a main form of cardiovascular disease, and further highlights the possible link between systemic disease and microvascular dysfunction.

Relationship between peripheral and intracoronary blood flow in patients with angina and nonobstructive coronary arteries.

Coronary vasomotor dysfunction, an important underlying cause of angina and nonobstructive coronary arteries (ANOCA), encompassing coronary vasospasm, coronary endothelial dysfunction, and/or coronary microvascular dysfunction, is clinically assessed by invasive coronary function testing (ICFT). As ICFT imposes a high burden on patients and carries risks, developing noninvasive alternatives is important. We evaluated whether coronary vasomotor dysfunction is a component of systemic microvascular endothelial and smooth muscle dysfunction and can be detected using laser speckle contrast analysis (LASCA). Forty-three consecutive patients with ANOCA underwent ICFT, with intracoronary acetylcholine, adenosine, and flow measurements, to assess coronary vasomotor dysfunction. Cutaneous microvascular function was assessed using LASCA in the forearm, combined with vasodilators acetylcholine, sodium nitroprusside, and insulin and using EndoPAT, by measuring the reactive hyperemia index (RHI). Of the 43 included patients with ANOCA (79% women, 59 ± 9 yr old), 38 patients had coronary vasomotor dysfunction, including 28 with coronary vasospasm, 26 with coronary endothelial dysfunction, and 18 with coronary microvascular dysfunction, with overlapping endotypes. Patients with and without coronary vasomotor dysfunction had similar peripheral flow responses to acetylcholine, insulin, and RHI. In contrast, coronary vasomotor dysfunction was associated with lower peripheral flow responses to sodium nitroprusside (P < 0.001). An absolute flow response to sodium nitroprusside of 83.95 APU resulted in 86.1% sensitivity and 80.0% specificity for coronary vasomotor dysfunction (area under the ROC curve, 0.883; P = 0.006). In conclusion, this study provides evidence of systemic vascular smooth muscle dysfunction in patients with ANOCA with coronary vasomotor dysfunction and the diagnostic value of peripheral microvascular function testing as a noninvasive tool for detecting coronary vasomotor dysfunction.NEW & NOTEWORTHY This study provides proof of concept that assessment of the peripheral vasculature, particularly vascular smooth muscle cells measured using the LASCA technology holds potential as a noninvasive tool for detecting coronary vasomotor dysfunction. This finding highlights the potential of the LASCA technology in, for example, medication studies for coronary vasomotor dysfunction, especially when investigating whether medication improves vascular function, as repeated peripheral measurements are less invasive than invasive coronary function testing, the current gold standard.

Follow-up assessment of the microvascular function in patients with long COVID

Long COVID is a complex pathophysiological condition. However, accumulating data suggests that COVID-19 is a systemic microvascular endothelial dysfunction with different clinical manifestations. In this study, a microvascular function was assessed in long COVID patients (n = 33) and healthy controls (n = 30) using flow-mediated skin fluorescence technique (FMSF), based on measurements of nicotinamide adenine dinucleotide fluorescence intensity during brachial artery occlusion (ischemic response, IR) and immediately after occlusion (hyperemic response, HR). Microcirculatory function readings were taken twice, 3 months apart. In addition, we quantified biochemical markers such as the serum L-arginine derivatives and hypoxia-inducible factor 1α (HIF1α) to assess their relation with microvascular parameters evaluated in vivo. In patients with long COVID, serum HIF1α was significantly correlated to IRindex (r = −0.375, p < 0.05). Similarly, there was a significant inverse correlation of serum asymmetric dimethyl-L-arginine levels to both HRmax (r = −0.343, p < 0.05) and HRindex (r = −0.335, p < 0.05). The IR parameters were found lower or negative in long COVID patients and recovered in three-month follow-up. Hypoxia sensitivity value was significantly higher in long COVID patients examined after three months of treatment based on the combination of ACE-inhibitors and beta-adrenolytic compared to baseline condition (85.2 ± 73.8 vs. 39.9 ± 51.7 respectively, p = 0.009). This study provides evidence that FMSF is a sensitive, non-invasive technique to track changes in microvascular function that was impaired in long COVID and recovered after 3 months, especially in patients receiving a cardioprotective therapy.

Anti TNF-Alpha Treatment Improves Microvascular Endothelial Dysfunction in Rheumatoid Arthritis Patients.

Nailfold capillaroscopy is a non-invasive investigation, which allows for the study of the microvasculature (anatomical and functional). Rheumatoid arthritis (RA) is associated with a high risk of cardiovascular atherosclerotic diseases, with endothelial dysfunction (macrovascular and microvascular) representing the first step in atherosclerosis development. The aim of this study is represented by the assessment of microvascular endothelial dysfunction in RA patients by means of nailfold capillaroscopy and to assess its evolution after a period of 12 months of anti TNF-alpha treatment. The study included 70 consecutive patients with RA and 70 healthy subjects, matched for age and gender, as the control group. Rheumatoid factor, anti-cyclic citrullinated peptide antibodies, serum TNF-α, C reactive protein, and erythrocytes sedimentation rate were evaluated in all patients, but in controls, only rheumatoid factor, serum TNF-α, C reactive protein, and erythrocytes sedimentation rate were measured. The RA activity was measured by DAS28. Nailfold capillaroscopy was carried out in all patients and controls, determining the baseline nailfold capillary density (Db), nailfold capillary density during reactive hyperemia (Dh), and nailfold capillary density after venous congestion (Dc). Data were presented as mean ± standard deviation. Statistical analysis was performed using ANOVA and Pearson's correlation, with p < 0.05 being statistically significant. Db, Dh, and Dc were lower in RA patients than in controls (p < 0.0001), correlating with RA activity and TNF-α (p < 0.05). After 12 months of anti TNF-α treatment, microvascular endothelial dysfunction improved (p < 0.0001). Microvascular endothelial dysfunction can be assessed by nailfold capillaroscopy, with anti TNF-α medication contributing to its improvement.

Abstract Tu042: Fatty Acid Dysregulation Drives Cardio-Hepatic Crosstalk in Heart Failure with Preserved Ejection Fraction (HFpEF)

Introduction: Heart failure with preserved ejection fraction (HFpEF) is a heterogenous clinical syndrome that accounts for nearly half of all heart failure cases world-wide. The pathophysiological mechanisms underlying HFpEF include a variety of extracardiac abnormalities such as metabolic derangements, arterial hypertension, and microvascular endothelial dysfunction, that all drive left ventricular remodeling and dysfunction. The phenotypic diversity presented in HFpEF involves functional and structural changes in several organs including the liver. As a highly vascularized organ, the liver is highly sensitive to any hemodynamic changes in the heart and clinical studies have established the presence of liver injury in HFpEF patients. However, there is limited evidence of this relationship in preclinical mouse models, thereby hindering the exploration of the pathological mechanisms linking the two organs. Cardio-hepatic interactions are poorly understood yet play a critical role in the pathophysiology of HFpEF where aberrant metabolic signaling pathways such as insulin resistance, inflammation and oxidative stress significantly contribute to disease progression and further perpetuate a vicious cycle of cardio-hepatic deterioration. Hypothesis: With limited preclinical data in the field, we sought to elucidate the potential pathophysiological mechanisms driving cardio-hepatic crosstalk in HFpEF. Methods: We used a two-hit preclinical mouse model that recapitulates cardiometabolic HFpEF to characterize the coexistence of cardiac and hepatic dysfunction in HFpEF. Male mice were kept on the HFpEF model for 15 weeks and subjected to echocardiography, glucose tolerance tests, histopathology, and multi-omics analyses. Results: We report that markers of HFpEF severity such as diastolic dysfunction and left ventricular hypertrophy, significantly correlated with hepatic injury and dysfunction that exacerbated metabolic dysfunction-associated fatty liver disease (MAFLD) progression. Impaired energy substrate utilization due to fatty acid dysregulation was a major mechanism underlying cardio-hepatic crosstalk in HFpEF. Conclusion: Our findings highlight fatty acid metabolism as a potential target to mitigate inter-organ dysfunction in HFpEF, representing a promising opportunity to create new treatment paradigms and drive positive outcomes in HFpEF.

Identification and transcriptomic assessment of latent profile pediatric septic shock phenotypes

BackgroundSepsis poses a grave threat, especially among children, but treatments are limited owing to heterogeneity among patients. We sought to test the clinical and biological relevance of pediatric septic shock subclasses identified using reproducible approaches.MethodsWe performed latent profile analyses using clinical, laboratory, and biomarker data from a prospective multi-center pediatric septic shock observational cohort to derive phenotypes and trained a support vector machine model to assign phenotypes in an internal validation set. We established the clinical relevance of phenotypes and tested for their interaction with common sepsis treatments on patient outcomes. We conducted transcriptomic analyses to delineate phenotype-specific biology and inferred underlying cell subpopulations. Finally, we compared whether latent profile phenotypes overlapped with established gene-expression endotypes and compared survival among patients based on an integrated subclassification scheme.ResultsAmong 1071 pediatric septic shock patients requiring vasoactive support on day 1 included, we identified two phenotypes which we designated as Phenotype 1 (19.5%) and Phenotype 2 (80.5%). Membership in Phenotype 1 was associated with ~ fourfold adjusted odds of complicated course relative to Phenotype 2. Patients belonging to Phenotype 1 were characterized by relatively higher Angiopoietin-2/Tie-2 ratio, Angiopoietin-2, soluble thrombomodulin (sTM), interleukin 8 (IL-8), and intercellular adhesion molecule 1 (ICAM-1) and lower Tie-2 and Angiopoietin-1 concentrations compared to Phenotype 2. We did not identify significant interactions between phenotypes, common treatments, and clinical outcomes. Transcriptomic analysis revealed overexpression of genes implicated in the innate immune response and driven primarily by developing neutrophils among patients designated as Phenotype 1. There was no statistically significant overlap between established gene-expression endotypes, reflective of the host adaptive response, and the newly derived phenotypes, reflective of the host innate response including microvascular endothelial dysfunction. However, an integrated subclassification scheme demonstrated varying survival probabilities when comparing patient endophenotypes.ConclusionsOur research underscores the reproducibility of latent profile analyses to identify pediatric septic shock phenotypes with high prognostic relevance. Pending validation, an integrated subclassification scheme, reflective of the different facets of the host response, holds promise to inform targeted intervention among those critically ill.Graphical abstract

Chronic β3 adrenergic agonist treatment improves brain microvascular endothelial function and cognition in aged mice.

Microvascular endothelial dysfunction, characterized by impaired neurovascular coupling, reduced glucose uptake, blood-brain barrier disruption, and microvascular rarefaction, plays a critical role in the pathogenesis of age-related vascular cognitive impairment (VCI). Emerging evidence points to non-cell autonomous mechanisms mediated by adverse circulating milieu (an increased ratio of pro-geronic to anti-geronic circulating factors) in the pathogenesis of endothelial dysfunction leading to impaired cerebral blood flow and cognitive decline in the aging population. In particular, age-related adipose dysfunction contributes, at least in part, to an unfavorable systemic milieu characterized by chronic hyperglycemia, hyperinsulinemia, dyslipidemia, and altered adipokine profile, which together contribute to microvascular endothelial dysfunction. Hence, in the present study, we aimed to test whether thermogenic stimulation, an intervention known to improve adipose and systemic metabolism by increasing cellular energy expenditure, could mitigate brain endothelial dysfunction and improve cognition in the aging population. Eighteen-month-old old C57BL/6J mice were treated with saline or CL (β3-adrenergic agonist) for 6 weeks followed by functional analysis to assess endothelial function and cognition. CL treatment improved neurovascular coupling responses and rescued brain glucose uptake in aged animals. In addition, CL treatment also attenuated blood-brain barrier leakage and associated neuroinflammation in the cortex of aged animals. More importantly, these beneficial changes in microvascular function translated to improved cognitive performance in radial arm water maze and Y-maze tests. Our results suggest that β3-adrenergic agonist treatment improves multiple aspects of brain microvascular endothelial function and can be potentially repurposed for treating age-associated cognitive decline.

Adiponectin and Paraoxonase-1 Correlation With Thrombolysis in Myocardial Infarction Frame Count With Coronary Slow Flow Phenomenon

Objectives: Coronary slow flow phenomenon (CSFP) is an important angiographic entity, with no clear-cut etiology. The effects of adiponectin (APN) and paraoxonase-1 (PON-1) have been proven in microvascular disease pathophysiology, endothelial dysfunction and atherosclerosis. The present study aimed to determine the correlation between APN and PON-1 and CSFP. Methods: Subjects who were undergone coronary angiography and met the inclusion and exclusion criteria were included in this study. The study subjects were divided into the following groups: 40 subjects without coronary artery disease (CAD) and CSFP, 22 patients without CAD but with CSFP, 29 patients with CAD &lt; 50% and without CSFP, 22 patients with CAD (50-90%) but without CSFP and 16 patients with CAD and CSFP. Coronary flow rates of the participants with slow flow diagnosis were determined by thrombolysis in myocardial infarction (TIMI) frame count method. The serum levels of APN and PON-1 were measured by ELISA kit. Results: There were no significant differences between groups in serum levels of APN. No significant correlation was observed between APN serum concentration and corrected TIMI frame count (TFC) (r=0.17, P=0.29). The PON-1 serum concentration in patients with CAD (50-90%) and without CSFP was significantly lower than the other groups (P&lt;0.01). There was a near significant correlation between PON-1 serum levels and corrected TFC in left anterior descending coronary artery (r=0.32, P=0.08). Discussion: The present study has demonstrated no significant correlation between the serum concentration of APN and PON-1 and corrected TFC, so we need more extensive studies in this regard with larger sample size.

The association of microvascular disease and endothelial dysfunction with vertebral trabecular bone mineral density : The MESA study.

Microvascular diseases of the eye, kidney, and brain are associated with endothelial dysfunction and increased hip fracture risk. To explore the basis for higher hip fracture risk, we comprehensively examined whether markers of microvascular disease and/or endothelial dysfunction are related to trabecular bone mineral density (BMD), a proximate risk factor for osteoporotic fractures. Among 6814 participants in the Multi-Ethnic Study of Atherosclerosis study (MESA), we derived thoracic vertebral trabecular BMD from computed tomography of the chest and measured urine albumin to creatinine ratios (UACR), retinal arteriolar and venular widths, flow mediated dilation (FMD) of the brachial artery after 5min of ischemia; and levels of five soluble endothelial adhesion markers (ICAM-1, VCAM-1, L-selectin, P-selectin, and E-selectin). Linear regression models were used to examine the association of trabecular BMD with markers of microvascular disease and with markers of endothelial dysfunction. We observed no significant associations of UACR, retinal arteriolar or venular widths, or FMD with BMD. We also observed no statistically significant association of spine trabecular BMD with levels of endothelial adhesion markers. Men and women had largely similar results. We conclude that there is little evidence to connect thoracic spine trabecular BMD to microvascular disorders or to endothelial dysfunction among multi-ethnic middle-aged and older adults. Other factors beyond trabecular BMD (e.g., bone quality or predisposition to falling) may be responsible for the associations of microvascular disease with osteoporotic fractures.

Role of plasmacytoid dendritic cells in vascular dysfunction in mice with renovascular hypertension

Endothelial dysfunction and inflammation are clinically significant risk factors for cardiovascular diseases in hypertension. Although immune cells play a role in hypertension, the impact of plasmacytoid dendritic cells in established renovascular hypertension-induced cardiovascular complications is not fully understood. We investigated plasmacytoid dendritic cells' contribution to arterial endothelial dysfunction and inflammation in renovascular hypertension.A two-kidney one-clip (2K1C) model for four weeks in both male and female mice was used to induce renovascular hypertension. We treated mice with or without anti-PDCA-1 antibodies for one week to deplete the plasmacytoid dendritic cells. Renovascular hypertension causes cardiac hypertrophy, lung edema, and microvascular endothelial dysfunction associated with inflammation induction in mice. Moreover, renovascular hypertension affects the profile of immune cells, including dendritic cells and macrophages, with variations between male and female mice. Interestingly, the depletion of plasmacytoid dendritic cells significantly reduces blood pressure, cardiac hypertrophy, lung edema, inflammation, and oxidative stress and improves microvascular endothelial function via the endoplasmic reticulum (ER) stress, autophagy, and mTOR-dependent mechanisms.Plasmacytoid dendritic cells significantly contribute to the development of cardiovascular complications in renovascular hypertension by modulating immune cells, inflammation, oxidative stress, and ER stress.

Sphingosine-1-Phosphate Promotes Resiliency to External Stress in the Human Microvasculature

Exposure to external stress (e.g. high pressure, high glucose) promotes human microvascular endothelial dysfunction and reduces the overall magnitude of flow-induced dilation (FID). We have previously shown that treatment with sphingosine-1-phosphate (S1P), a sphingolipid known to activate pro-survival pathways in endothelial cells, restores nitric oxide (NO) as the primary mediator of flow-induced dilation (FID) in arterioles from patients with coronary artery disease. Whether pre-treatment with S1P can prevent stress-induced microvascular endothelial dysfunction remains unknown. Our hypothesis is that pre-conditioning with S1P will promote resiliency to external stress (high intraluminal pressure) and prevent stress-induced reduction of FID. Human resistance arterioles (100-250μm) from otherwise healthy adults (one risk factor or less for coronary artery disease) were dissected from discarded surgical adipose tissue and treated with S1P (1μM) or vehicle control for 16-20 hr prior to the flow experiment. Vessels were cannulated for videomicroscopy and stressed with elevated intraluminal pressure (150mmHg, 30 min) then pre-constricted with endothelin-1 prior to initiating flow to elicit dilation. Arterioles treated with vehicle and exposed to high intraluminal pressure exhibited an overall reduction in vasodilatory capacity to flow (37.3%±8.6) compared to non-stressed, vehicle treated microvessels (66.1%±5.5). However, the ability to dilate to flow was preserved in microvessels pre-treated with S1P and exposed to high pressure (74.8%±6.7) compared to vehicle and high pressure (37.3%±8.6). These data suggest that S1P-activated pathways may foster resilience by reversing stress-induced microvascular endothelial function. Targeting S1P signaling may offer a novel therapeutic strategy to prevent microvascular dysfunction and the myriad diseases it causes, such as large vessel atherosclerosis, and heart failure with preserved ejection fraction. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

L-Citrulline Supplementation Improves Leg Endothelial Function and Blood Flow Responses to Plantarflexion Exercise in Hypertensive Postmenopausal Women

Menopause and hypertension are associated with macro- and microvascular endothelial dysfunction at rest. Arginine deficiency and low nitric oxide (NO) synthesis may contribute to reduced muscle blood flow (BF) and oxygen delivery to exercising muscles. Improving BF to calf muscles may enhance physical activity. L-Citrulline supplementation (CIT) has improved resting macrovascular endothelial function via increased arginine availability for NO synthesis. Thus, the purpose of this study was to examine the effects of CIT on resting microvascular endothelial function and BF responses to plantarflexion exercise (PFE) in hypertensive postmenopausal women. We hypothesized that CIT would improve microvascular function and BF responses to PFE compared to placebo (PL). Twenty-one hypertensive postmenopausal women were randomized to 4 weeks of CIT (10g/day, n=10) or PL ( n=11). Superficial femoral macro- (flow-mediated dilation; FMD) and microvascular function (5s average peak blood velocity and flow during reperfusion) were assessed by ultrasound at 0 and 4 weeks. Femoral artery BF and vascular conductance (VC) were measured via ultrasound at rest and during 3-minute stages of rhythmic PFE at 5%, 15%, and 30% of 1-repetition maximum (1RM) at 0 and 4 weeks. BF and VC responses to PFE were analyzed as the change from rest to the last minute of each stage. There were no differences between groups in FMD, 5s peak velocity and flow during reperfusion, and vascular responses to PFE at 0 weeks. CIT significantly increased FMD (CIT:Δ1.28 ± 0.42 vs PL:Δ0.01 ± 0.40%, p = 0.04) and 5s peak velocity (CIT:Δ17.44 ± 4.21 vs PL:Δ0.09 ± 4.01 cm/s, p = 0.01) and flow (CIT:Δ220 ± 54 vs PL:Δ35 ± 51 mL/min, p = 0.02) during reperfusion compared to PL. CIT had no effect on BF and VC responses to 5% PFE ( p &gt; 0.05). CIT significantly augmented BF responses to 15% PFE (CIT:Δ82 ± 16 vs PL:Δ22 ± 15 mL/min, p &lt; 0.01) and 30% PFE (CIT:Δ156 ± 33 vs PL:Δ38 ± 32 mL/min, p &lt; 0.01) and VC responses to 15% PFE (CIT:Δ0.80 ± 0.16 vs PL:Δ0.11 ± 0.15 mL*100mmHg/min, p &lt; 0.01) and 30% PFE (CIT:Δ1.49 ± 0.29 vs PL:Δ0.24 ± 0.27 mL*100mmHg/min, p &lt; 0.01) compared to PL. Improvements in FMD were not correlated with BF or VC responses to PFE ( p &gt; 0.05). Improvements in 5s peak velocity were positively correlated with BF responses to 15% PFE ( r = 0.498, p = 0.02) and 30% PFE ( r = 0.532, p = 0.01), and with VC responses to 15% PFE ( r = 0.542, p = 0.01) and 30% PFE ( r = 0.633, p &lt; 0.01). Similarly, augmented 5s flow was positively correlated with BF ( r = 0.461, p = 0.04) and VC ( r = 0.558, p = 0.01) responses to 30% PFE. These findings indicate that CIT improved superficial femoral artery macro- and microvascular endothelial function at rest. However, only improvements in microvascular endothelial function influenced vascular function during leg exercise in hypertensive postmenopausal women. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Insulin-Mediated Capillary Recruitment Is Absent in the Cutaneous Microvasculature of Women with a History of Gestational Diabetes Mellitus

Women with a history of gestational diabetes mellitus (GDM) have a significantly greater risk of developing cardiovascular disease and type II diabetes compared to women who had an uncomplicated pregnancy (HC). Although the mechanisms underlying this increased risk are unclear, emerging evidence suggests that microvascular endothelial dysfunction, mediated via reduced nitric oxide (NO)-dependent dilation, persists after pregnancy complicated by GDM. Whether this microvascular dysfunction reduces insulin-mediated responses in these women is unexplored. We hypothesized that insulin-mediated capillary recruitment would be attenuated in women with a history of GDM via NO-dependent mechanisms. 24 women (n=12/group; HC: 35±1 years, 24±4 months post-partum; GDM: 33±1 years, 21±3 months postpartum) underwent intradermal microdialysis, which involved the placement of 2 fibers in the ventral forearm for the local delivery of 10−4M insulin alone or 10−4M insulin+15mM NG-nitro-L-arginine methyl ester (L-NAME, NO-synthase inhibitor). The cutaneous blood flow response to post-occlusive reactive hyperemia (PORH; 5 minutes) was assessed before and during insulin perfusion. Red blood cell flux was measured continuously over each microdialysis site by laser-Doppler flowmetry. Cutaneous vascular conductance was calculated (CVC=flux/mean arterial pressure), normalized to maximum (%CVCmax), and presented as PORH area under the curve (AUC, %CVCmax• sec−1). Microvascular capillary recruitment was assessed as ΔAUC (pre-insulin AUC - insulin AUC). Insulin perfusion increased PORH in HC (pre-insulin: 4066±490 vs. insulin: 7848±978 AUC; p=0.03) but had no effect in GDM (pre-insulin: 3765±293 vs. insulin: 6196±779 AUC; p=0.26). Insulin perfusion did not increase PORH at the L-NAME site in either group (p&gt;0.05). Within groups, L-NAME perfusion reduced insulin-mediated capillary recruitment in HC (control: 3781±1109 vs. L-NAME: 470±945 ΔAUC; p=0.04) but not GDM (control: 2431±796 vs. L-NAME: -41±1014 ΔAUC, p=0.11). These data suggest that insulin-mediated capillary recruitment assessed by PORH in the cutaneous circulation is mediated by NO-dependent mechanisms in healthy women with a history of uncomplicated pregnancy and attenuated in healthy women with a history of GDM. This reduction in insulin-mediated microvascular responses may contribute to the increased risk of cardiovascular disease and type II diabetes in these women. UI Fraternal Order of Eagles Diabetes Research Center Catalyst Grant; NIH HL169201. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Endothelial DRP1 mediates microvascular dysfunction in the human and rat microcirculation independent of ROS production

Introduction: Microvascular endothelial dysfunction is a strong, independent, and modifiable risk factor for the development of coronary artery disease (CAD). Under physiological conditions, an increase in blood flow stimulates endothelial cells (EC) to release nitric oxide (NO) which mediates microvascular dilation. Under pathological conditions, such as CAD, NO-mediated dilation is lost but dilator capacity is preserved by mitochondria-derived hydrogen peroxide (H2O2), a reactive oxygen species (ROS). Recent work in rodent models suggests that ATP is required for NO-mediated and increasing evidence suggests that the balance between mitochondrial ATP vs. ROS production contributes to this phenotypic switch. Mitochondrial fission, an autoregulatory process primarily mediated by DRP1, is associated with various cardiometabolic diseases and is a direct contributor to increased reactive oxygen species (ROS) formation and decreased production of ATP. However, the role of DRP1 in the endothelium and it impacts on vascular function is unknown. Hypothesis: We hypothesize that mitochondrial fission, mediated by DRP1, is a critical regulator of microvascular redox balance. Methods: Microvessels (~50-200μm) were obtained from discarded human adipose surgical tissue from individuals with and without CAD or from rat mesentery and subjected to pressure myography (flow-mediated dilation; FMD). A fluorescent mitochondrial-specific ATP probe was measured in vessels after 10 minutes at maximal shear stress. DRP1 overexpression was achieved by adeno-associated viral (AAV) gene transfer and downregulated via DRP1 targeted siRNA (si-DRP1). To show physiologic and translational relevance, a transgenic rat model with a cre-inducible endothelial-specific overexpression of DRP1 (DRP Tg) was created to test the in vivo effects of EC-DRP1 overexpression. To test whether reduction of ROS improved the observed phenotype, vessels were acutely treated ex vivo in the organ chamber with TEMPOL, a cytosolic antioxidant, and mito-tempo, a mitochondrial antioxidant. Two-way ANOVA, post-hoc analysis was performed using PRISM to best understand the effects of the treatment and pressure-gradient. T-test was performed for comparison analyses between patients with/without CAD. Results:Fluorescent analysis of showed that ATP is increased in vessels obtained from patients without CAD compared to those with CAD (6.3 vs 1.1, mean fluorescent intensity, N=3, p&lt;0.05). In vessels obtained from patients without CAD, AAV-mediated DRP1 overexpression switches the mediator of FMD from NO to H2O2 (inhibitable by PEG-Catalase, max dilation 83.2% vs. 20.2%, N=6, p&lt;0.05). Conversely, arterioles obtained from patients with CAD treated with si-DRP1 restores NO-mediated dilation (inhibitable by L-NAME, max dilation 94.6% vs. 41.7%, N=5, p&lt;0.05). In the rat microcirculation, FMD is significantly impaired in EC-DRP1 rats compared to littermate controls (max dilation 41.2% vs. 80.3%, N=9, p&lt;0.05). Scavenging of ROS (TEMPOL and mito-Tempo) does not restore the phenotype in both human and rat microcirculation suggesting DRP1 mediates dysfunction independent of ROS, which is in line with preliminary observations of reduced flow-induced ATP levels in vessels from patients with CAD. Significance: These data indicate that ROS may be secondary to mitochondrial fission rather than causal to the microvascular phenotype observed in patients with CAD. Therefore, targeting endothelial mitochondrial fission may be of therapeutic benefit to treat cardiovascular disease. AHA Diversity Research Pre-Doctoral Award (CGH), 5P30ES030283-04 (AJL), 5R01HL133029-5 (AB), 5R21OD018306-2 (AB). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Acute and chronic hyperglycemia blunts microvascular reactivity in postmenopausal women with type 2 diabetes

Type 2 diabetes (T2D) is strongly associated with increased risk of cardiovascular diseases via endothelial dysfunction. Hyperglycemia causes microvascular endothelial dysfunction and reduces muscle perfusion. Near-infrared spectroscopy (NIRS) measures microvascular reactivity in skeletal muscle during vascular occlusion/reperfusion. However, the impact of acute and chronic hyperglycemia on macrovascular endothelial function (brachial flow-mediated dilation, FMD) and microvascular reactivity (NIRS-derived tissue oxygen saturation index, TOI) has not been examined in postmenopausal women with and without T2D. We hypothesized that T2D women would have decreased FMD and TOI responsiveness in the fasted condition and greater vascular impairments during acute hyperglycemia compared to controls.Ten T2D (61 ± 5 years) and 10 normoglycemic postmenopausal women (CON, 62 ± 7 years) participated in the study. Hemoglobin A1C (HbA1C) and blood glucose were measured by finger prick at baseline (fasted condition). Brachial artery FMD was evaluated using ultrasound. Forearm muscle TOI magnitude and slope during arterial occlusion and reperfusion periods were measured using NIRS. An oral glucose tolerance test (OGTT) was performed to induce acute hyperglycemia. Blood glucose, FMD, and TOI were measure at baseline and 1 hour (1-h) after OGTT. Abdominal fat was assessed by waist circumference and visceral adipose tissue (VAT) obtained by a whole-body dual-energy X-ray absorptiometry scan.Fasting HbA1C and glucose, waist circumference, and VAT were higher in T2D compared to CON (all p &lt; 0.05). The increase in blood glucose at 1-h was higher in T2D (Δ143 ± 15 mg/dl) compared to CON (Δ49 ± 5 mg/dl) (p &lt; 0.01). FMD at baseline and the decreases in FMD at 1-h were similar in T2D (Δ-2.2 ± 0.2%) and CON groups (Δ-1.9 ± 0.4%) (all p &lt; 0.01). At baseline, T2D showed blunted TOI occlusion magnitude (T2D: -16 ± 1 vs. CON: -21 ± 2%), TOI occlusion slope (T2D: -0.05 ± 0.01 vs. CON: -0.07 ± 0.01), TOI reperfusion magnitude (T2D: 21 ± 2 vs. CON: 32 ± 3%), and TOI reperfusion slope (T2D: 0.79 ± 0.10 vs. CON: 1.19 ± 0.14) compared to CON (all p &lt; 0.05). At 1-h, T2D exhibited lower TOI occlusion magnitude (T2D: -17 ± 2 vs. CON: -24 ± 3%), TOI occlusion slope (T2D: -0.06 ± 0.01 vs. CON: -0.08 ± 0.01), TOI reperfusion magnitude (T2D: 23 ± 2 vs. CON: 33 ± 4%), and TOI reperfusion slope (T2D: 0.90 ± 0.19 vs. CON: 1.14 ± 0.15) compared to CON (all p &lt; 0.05). HbA1C, a measure of chronic hyperglycemia, was positively correlated with VAT (r = 0.514, p = 0.02) and TOI occlusion slope (r = 0.460, p = 0.04) and negatively correlated with TOI reperfusion magnitude (r = -0.506, p = 0.02) and slope at baseline (r = -0.493, p = 0.03). In conclusion, women with T2D exhibited blunted microvascular reactivity despite similar FMD compared with normoglycemic women in the fasted condition. Acute hyperglycemia further blunted microvascular function, but not macrovascular endothelial function, in women with T2D. Blunted microvascular reactivity was associated with chronic hyperglycemia and elevated VAT in postmenopausal women. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.