bluuebunny/crossref_metadata_2025 huggingface dataset:
Protecting Cerebral Microvascular Endothelial Cells in Diabetes Mellitus
Authors: Bidasee Keshore R , Alomar Fadhel , Rozanski George J , Mayhan William , Padanilam Babu , Singh Jaipaul
Published: November 2023

Endothelial cell‐mediated vasodilatation of cerebral arterioles is impaired in individuals with diabetes mellitus (DM). This defect, which compromises hemodynamics can lead to hypoxia, oxidative stress, vascular leakage/microbleeds, inflammation, and exaggerated ischemia‐reperfusion injuries. Excessive production of the mitochondrial toxin methylglyoxal (MG) has emerged as a leading cause for endothelial cell dysfunction in DM. However, why/how MG increases in the brain during DM remains undefined. Here tissue from different brain regions from Type 1 and Type 2 DM patients and from Type 1 DM rats were used to assess expression and activities of the MG synthesizing and degradation enzymes, vascular adhesion protein‐1 (VAP‐1) and glyoxalase‐I (Glo‐I), respectively. Type 1 DM rats were also used to determine if increasing Glo‐I in cerebral microvascular smooth muscle cells (cSMCs) would blunt endothelial cell dysfunction and the resultant cerebral defects. In brains of patients and rats with DM, VAP‐1 was upregulated and Glo‐I was downregulated in cSMCs. MG and its metabolite argpyrimidine were also upregulated. In DM rats, endothelial cell‐mediated vasodilatation of cerebral arterioles was compromised and cerebral microvascular leakage/microbleeds, gliosis, oxidative stress, infiltration of macrophage/neutrophil in brain parenchyma, and inflammation (NF‐kB activation and TNF‐α) were increased. The density of microvessel perfused was also reduced and a transient occlusion of a mid‐cerebral artery resulted in exaggerated ischemia‐reperfusion injuries. Restoring Glo‐I protein in cSMCs of Type 1 DM to control levels using a custom‐designed adeno‐associated virus, lowered MG, its metabolite argpyrimidine and prevented endothelial cell dysfunction. It also attenuated upregulation of VAP‐1 and MG production in cSMCs, blunted oxidative stress, microvascular leakage, gliosis, macrophage/neutrophil infiltration, NF‐κB activation, TNF‐α production, and restored perfusion of cerebral microvessels. From these new data we conclude that the supra‐physiologic level of MG that triggers dysregulation of endothelial cells in the cerebral microvasculature in DM is arising from increased expression of VAP‐1 and decreased Glo‐I in cSMCs. They also suggest that lowering MG in cSMCs could be a viable therapeutic strategy to preserve cECs function and prevent deleterious cerebral deficits in DM.
Elevated Cardiorespiratory Fitness is Associated with Blunted Cerebral Pressure‐Flow Relationships
Authors: Brassard Patrice , Paquette Myriam , Le Blanc Olivier , Malenfant Simon , Rahimaly Kevan , Lucas Samuel JE , Bailey Damian M
Published: November 2023

There appears to be a “hemodynamic paradox” associated with elevated cardiorespiratory fitness; in that it has a differential impact on cerebral blood flow and orthostatic tolerance. A reduction in orthostatic tolerance with high cardiorespiratory fitness may be related to a blunted cerebral pressure‐flow relationship during rapid changes in blood pressure, and not only a consequence of inadequate cerebral perfusion. However, research on how cardiorespiratory fitness influences cerebral pressure‐flow relationships during rapid changes in blood pressure, and the consequences for orthostatic tolerance remain equivocal. Mean arterial pressure (MAP; finger photoplethysmography) and middle cerebral artery flow velocity (MCAv; transcranial Doppler ultrasound) were continuously monitored in 19 male endurance athletes (V̇O2max: 56±5 mL·kg−1·min−1) and 8 inactive/moderately active control participants (39±5 mL·kg−1·min−1, P<0.01). Orthostatic tolerance was assessed by the prevalence of presyncope during a 20‐min 70° head‐up tilt. Cerebral pressure‐flow relationships were assessed by: [1] the time delay before onset of regulation (increase in the cerebrovascular conductance index (MCAvmean/MAP)) and [2] rate of regulation, after transient hypotension induced by bilateral thigh‐cuff release and sit‐to‐stand, and transfer function analysis (TFA) of blood pressure and MCAv responses during [3] spontaneous and [4] forced oscillations induced via 5‐min of repeated squat‐stand maneuvers at both 0.05 and 0.10 Hz. Prevalence of presyncope was not different between groups (p=0.41). The time delay before onset of regulation tended to be longer in athletes compared to controls after thigh‐cuff deflation (p=0.11) and prolonged after sit‐to‐stand (3.2 ± 1.6 vs. 1.4 ± 1.1 s; p=0.01), and the latter correlated with V̇O2max (r=0.46, p=0.03). Rate of regulation was similar between groups irrespective of the technique employed. Athletes had lower TFA phase in the low frequency (p<0.01) range and higher TFA gain during 0.1 Hz squat‐stand compared to controls (p=0.01). Metrics describing cerebral pressure‐flow relationships did not correlate with orthostatic tolerance. These results indicate an attenuated ability of the cerebral vasculature to react to slow rhythmical oscillations as well as rapid and large changes in blood pressure in fit individuals. However, these functional cerebrovascular adaptations do not influence orthostatic tolerance.

Support or Funding Information

The present study was funded by the Ministère de l'Education, du Loisir et du Sport du Québec, and the Foundation of the Institut universitaire de cardiologie et de pneumologie de Québec
The Effect of Alcohol Exposure in Utero on The Cerebral Circulation
Authors: Cananzi Sergio , Mayhan William
Published: November 2023

Fetal alcohol spectrum disorders (FASD) comprises several syndromes and permanent birth defects caused by in utero exposure to alcohol. FASD is linked to growth deficiencies, craniofacial abnormalities, and central nervous system damage. Although there is some evidence that FASD might be linked to cerebral vascular dysfunction in the fetal stage of development and into adulthood, very few studies have examined this possibility. The overall goal of our studies is to examine the influence of in utero exposure to alcohol on the cerebral microcirculation. We speculated that in utero exposure to alcohol would have a negative influence on cerebral blood vessels and this might be linked to neurological deficits observed in adults that suffer from FASD. The mechanism by which in utero exposure to alcohol affects brain development is not clear, but it may be related to the effect of alcohol on oxidative stress. Thus, our central hypothesis is that in utero exposure to alcohol produces an increase in oxidative stress to impair reactivity of cerebral arterioles and increase brain damage following cerebral ischemia/reperfusion. We suggest our studies will help fill a void in our understanding of the influence of in utero exposure to alcohol on cerebral blood vessels and how these factors may influence the deficits observed in individuals affected by FASD.

Support or Funding Information

Malcolm Feist Cardiovascular Fellowship, LSUHSC Shreveport LA.
Akt activation improves microregional oxygen supply/consumption balance after cerebral ischemia‐reperfusion
Authors: Weiss Harvey , Chi Oak Za , Liu Xia
Published: November 2023

Since the Akt/PI3K/mTOR pathway has produced conflicting results with regard to its benefit after cerebral ischemia, we examined one component of this pathway to determine its effects. We tested the hypothesis that activation of Akt would decrease infarct size and improve microregional O2 supply/consumption balance after cerebral ischemia‐reperfusion. This was tested in isoflurane anesthetized rats with middle cerebral artery blockade for 1 hr and reperfusion for 2 hr with and without SC‐79 (Akt activator, 0.05 mg/kg, three times). Regional cerebral blood flow was determined using a C14‐iodoantipyrine autoradiographic technique. Regional small vessel (20–60 μm diameter) arterial and venous oxygen saturations were determined microspectrophotometrically. There were no significant hemodynamic or blood gas differences between groups. The control ischemic‐reperfused cortex had a similar O2 consumption to the contralateral cortex. However, microregional O2 supply/consumption balance was significantly reduced in the ischemic‐reperfused cortex with many areas of low O2 saturation (42 of 80 veins with O2 saturation below 50%). SC‐79 did not significantly affect cerebral O2 consumption, but significantly improved O2 supply/consumption balance in the reperfused area (18 of 80 veins with O2 saturation below 50%). This was associated with a reduced cortical infarct size after Akt activation (13.3 ± 0.5% control vs 6.7 ± 0.3% SC‐79). This suggests that Akt activation is important for not only cell survival, but also for the control of local oxygen balance after cerebral ischemia‐reperfusion.
Endothelial Pannexin1 can regulate cerebral myogenic tone development and severity of ischemic stroke
Authors: Good Miranda Elizabeth , Bacon Hannah M , Eucker Stephanie A , Lang Susan M , Butcher Joshua T , Johnson Tyler J , Li Jun , Zuo Zhiyi , Isakson Brant E
Published: November 2023

Pannexin1 (Panx1) regulates adrenergic dependent vasoconstriction in peripheral arterioles; however, unlike peripheral arterioles, regulation of cerebral arteriole vasoconstriction is predominantly due to myogenic tone. Because ATP can elicit potent vasoconstriction of cerebral arterioles, we hypothesized that ATP release from Panx1 channels was involved in the development of myogenic tone of cerebral arterioles. Initially we found that myogenic tone in posterior cerebral arteries (PCAs) from wildtype mice was significantly inhibited when arterioles were treated with apyrase. Next we treated PCAs with pannexin pharmacological inhibitors (carbenoxolone, 10Panx1, and spironolactone), which also significantly reduced the development of myogenic tone. Spironolactone, which we found does not inhibit Cx43 hemichannels, had no effect on myogenic tone development in peripheral arterioles (i.e, third order mesenteric arterioles). Next we used a genetic approach to pannexin inhibition and used either mice lacking Panx1 in smooth muscle cells (SMC; SMC‐Cre Panx1fl/fl) or endothelial cells (EC; EC‐Cre Panx1fl/fl). The myogenic tone was not altered in the SMC‐Cre Panx1fl/fl mice, but was significantly reduced in the EC‐Cre Panx1fl/fl mice. In line with the spironolactone data, myogenic tone development in peripheral arterioles of EC‐Cre Panx1fl/fl mice was not different. Consistent with these data, we could detect no difference in blood pressure of EC‐Cre Panx1fl/fl mice compared to control mice. Since myogenic tone regulates the cerebral blood flow and has been suggested to play a role in stroke outcome, we investigated the stroke infarct volume in both SMC‐Cre Panx1fl/fl and EC‐Cre Panx1fl/fl mice. Experimentally we used a 90 min intra‐luminal filament occlusion to induce ischemia of the middle cerebral artery followed by 24 hour reperfusion upon removal. We found that stroke infarct volume was significantly reduced in EC‐Cre Panx1fl/fl mice, while SMC‐Cre Panx1fl/fl mice showed no protection. Since EC‐Cre Panx1fl/fl mice show reduced leukocyte rolling and adhesion following TNFα‐stimulation, we examined if these mice also demonstrate reduced infiltration of leukocytes. Preliminary data indicate that EC‐Cre Panx1fl/fl mice have reduced overall number of leukocytes in the ischemic hemisphere compared to control mice. Our data demonstrate that Panx1 in endothelium may regulate ischemic stroke outcome, possibly through myogenic tone of cerebral arterioles and/or the extent of leukocyte infiltration.

Support or Funding Information

Funding: HL088554, HL120840, HL007284, HL131399.
Integrative Physiology of Brain Perfusion During Extreme Chemoreflex Manoeuvers
Authors: Shoemaker J. Kevin , Barak Otto F. , Badrov Mark Kevin , Shoemaker Leena N. , Matushewski Bradley Kevin , Mijacika Tanja , Lojpur Mihajlo , Drvis Ivan , Dujic Zeljko
Published: November 2023

Both cerebral perfusion pressure (CPP) and vascular conductance (CVC) contribute to blood flow. Yet, rarely are these factors considered in cerebrovascular reactivity studies, in favour of the change in mean flow velocity (MFV) for a given dilatory stimulus such as carbon dioxide, an approach that can ignore the potential contributions of CPP. We tested the hypothesis that both CVC and CPP facilitate the increase cerebral perfusion during progressive chemoreflex stress. In healthy free divers (n=7; 1 female; age range = 22 to 34 years) middle cerebral artery MFV (transcranial Doppler ultrasound; Multigon), mean arterial pressure (MAP; Finometer), central venous pressure (CVP; dependent antecubital vein), end tidal CO2 (ETCO2; ADInstruments), and hemoglobin saturation (HbSat, pulse oximetry) were measured while CPP (MAP‐CVP) and CVC (MFV/CPP) were calculated. These indices were obtained at baseline, during a 2‐min preparatory phase of rebreathing to establish early effects on CVC and CPP, and then during i) extended rebreathe (RB), ii) apnea at total lung capacity (TLC), or iii) apnea at functional residual capacity (FRC); each stress assigned randomly and continued to volitional tolerance. ETCO2 increased 12–18 mmHg in all conditions (Effect of Time, P<0.001; no Condition effect). The 59% HbSat level attained during RB was lower than FRC (78%) or TLC (80%) (Condition x Time interaction P<0.001). MFV was similar at baseline (TLC, 52±11; FRC, 49±8; RB, 51±11 cm/s) and increased similarly (Time effect, P<0.001) in TLC (111±17 cm/s), FRC (106±18 cm/s) and RB (108±11 cm/s; No Condition effect). CVC increased similarly in each condition (TLC, 49±11; FRC, 57±31; RB, 61±23%; Effect of Time P<0.001; No Condition effect). Also, CPP increased similarly in each condition (TLC, 46±16%; FRC, 42±14%; RB, 36±16%; Time effect P<0.001). The CVC response typically plateaued following the preparatory 2‐min rebreathe phase of each protocol whereas the majority of the CPP response occurred during the Apnea and extended rebreathe phases. Therefore, the determinants of the linear increase in MFV across the preparatory rebreathe phase, and the subsequent RB, TLC, or FRC condition phases, switched from a largely CVC mechanism at lower levels of stress, to increased CPP during the extended Apnea or RB manoeuvres, regardless of differences in HbSat.

Support or Funding Information

NSERC discovery grant # 217916‐2013 awarded to J.K.S.
Testosterone downregulates the Nrf2 system and promotes vascular dysfunction in HFD‐fed mice
Authors: Costa Rafael Menezes , Alves‐Lopes Rheure , Mestriner Fabíola , Tostes Rita
Published: November 2023

Background

Obesity is an important cause of morbidity and mortality worldwide. Mechanisms triggered by the endocrine system justify the increase in body fat depots in obese individuals. Testosterone, the predominant and most active androgen, is linked to the metabolism of insulin, glucose and lipids. In the cardiovascular system, testosterone increases reactive oxygen species (ROS) generation. Considering that 1) obesity leads to vascular oxidative stress, 2) testosterone is a potent ROS inducer, and 3) the nuclear factor E2–related factor 2 (Nrf2) is a redox‐sensitive transcription factor that activates the expression of many key antioxidant genes, we hypothesized that testosterone downregulates the Nrf2 antioxidant system, favoring ROS accumulation and subsequent vascular dysfunction in high fat diet (HFD)‐fed obese mice.

Methods

Four weeks‐old male C57Bl/6J mice were anesthetized and submitted to orchiectomy (the efferent duct of each testicle was ligated and the testicles were removed) or sham‐operation. Mice received control (CD) or high fat diet (HFD) for 18 weeks. Vascular function was assessed in endothelium‐intact thoracic aortic rings and molecular mechanisms by which testosterone contribute to vascular dysfunction were determined.

Results

HFD reduced acetylcholine‐induced vascular relaxation in sham mice [(Relaxation %) CD Sham: 95.3 ± 2.7 vs. HFD Sham: 63.7 ± 1.7, n=6]. However, castration prevented HFD‐induced vascular dysfunction [(Relaxation %) CD Castrated: 94.1 ± 2.5 vs. HFD Castrated: 85.2 ± 2.4, n=7]. CD‐fed castrated mice treated with testosterone propionate exhibited decreased sensitivity to acetylcholine [(pD2) CD Sham: 7.4 ± 0.06 vs. CD Castrated + Testo: 6.7 ± 0.05, n=6]. In addition, the effects of castration in acetylcholine vasodilation in HFD mice were lost after testosterone treatment [(Relaxation %) HFD Castrated 85.2 ± 2.4 vs. HFD Castrated + Testo: 67.1 ± 1.3, n=6]. HFD increased vascular ROS generation, determined by lucigenin and amplex red assays, and castration prevented this increase. HFD increased Nrf2 expression in cytosolic fraction and decreased Nrf2 nuclear accumulation, which was linked to a decrease in mRNA expression of Nrf2‐regulated enzymes, such as catalase, heme oxygenase‐1, peroxiredoxin as well as decreased thioredoxin activity. These events were prevented in HFD‐fed castrated mice. The activation of the Nrf2 system by bardoxolone improved acetylcholine‐induced vascular relaxation in HFD‐fed mice [(Relaxation %) HFD Sham: 63.7 ± 1.7 vs. HFD Sham + Bardoxolone: 77.2 ± 1.8, n=6]. Bardoxolone and castration effects on acetylcholine vasodilation were similar. Bardoxolone increased nuclear accumulation of Nrf2 and decreased ROS generation in HFD‐fed Sham mice.

Conclusion

These results indicate that testosterone downregulates Nrf2, favoring oxidative stress and vascular dysfunction in HFD‐fed obese mice.

Support or Funding Information

CNPq, CAPES and FAPESP
Effects of Reactive Oxygen Species in Endothelial Cells Assessed by Observing Levels of JNK Activation
Authors: Latuska Katelyn , Farwell Sara Lynn , Lowe‐Krentz Linda
Published: November 2023

Heart disease is the leading cause of death around the world, and it is therefore extremely important to understand the molecular signaling and responses that lead to the development of heart disease. It has been found through multiple studies that unlike disturbed flow, laminar flow induces protective effects on endothelial cells. Conversely, the reactive oxygen species that the endothelial cells are exposed to damages the cells. Specifically, this study is evaluating the effects of reactive oxygen species on endothelial cells while subjected to laminar flow. In these studies, bovine aortic endothelial cells were exposed to media containing reactive oxygen species for different time increments using a flow chamber to provide laminar flow. The levels of active JNK, a stress activated kinase, were measured using immunofluorescence microscopy. It was found that the levels of p‐JNK, the activated form of JNK, increased significantly when exposed to higher concentrations from zero to 12%. The levels of pJNK also increased over longer time intervals of reactive oxygen species in static media, from 5 minutes to 25 minutes. Cells that had been treated with hydrogen peroxide prior to laminar flow seemed to be too damaged to remain attached to the surface of the slide after the addition of flow. Hydrogen peroxide was then added to the flow media, which will act during the exposure to laminar flow. Published literature shows evidence that after endothelial cells become acclimated to the addition of laminar flow, these cells are then more resistant to damage. Therefore, we predict that similarly, the acclimated endothelial cells will become more resistant to damage and the effects of the hydrogen peroxide. Further testing of these complex systems is important, as a better understanding of the ways in which these factors interact will provide additional information to help in the prevention and treatment of heart disease.

Support or Funding Information

This research was supported by a Langer‐Simon undergraduate research award to KL. The LLK laboratory is supported by HL 536104.
MMP‐2 dysfunction in African Americans Endothelial Cells: Potential Biomarker of Hypertension Risk?
Authors: Cook Marc D , Aldokhayyil Maitha , Adeyemo Adelola , Fernhall Bo , Brown Michael
Published: November 2023

Background

MMP‐2 is a biomarker that has been associated with systolic hypertension and arterial stiffness African Americans (AA). Endothelial cells (EC) constitutively express MMP‐2, where it mediates extracellular matrix turnover, and its dysfunction likely has some role in vascular function. In a small cohort of young AA and Caucasian (CA) men, we have data showing an inverse moderate correlation between circulating MMP‐2, carotid BP (r=−0.555), and aortic BP (r=−0.509) in AA (n=14) with no relationship in CA (n=18). In this preliminary in vitro study, we postulated a racial difference concerning MMP‐2 activity which contributes to endothelial dysfunction (EnDy) in AA.

Methods

The present preliminary work evaluated gene and protein expression and activity (via zymography) of secreted MMP‐2 in 4 AA and 4 CA primary human umbilical vein endothelial cells (HUVEC).

Results

MMP‐2 gene (>2‐fold increase, t2.8, 12: p=0.01*; Fig 1a) and protein (~2‐fold increase p=0.07; Fig 1b) expression were higher in AA. However, secreted MMP‐2 activity was significantly lower in AA EC (>2‐fold decrease t2.2, 14: p=0.04; Fig 2).

Conclusion

These in vitro data highlight EnDy in AA primary EC and suggest that blunted MMP‐2 activity may contribute to endothelial‐mediated vascular dysfunction (reduced extracellular matrix maintenance) and subsequent hypertension risk in AA. Further studies are necessary, and underway, to investigate the epigenetic and post‐translational regulation of MMP‐2 and its vasoactive properties in AA EC.

Support or Funding Information

Departmental
Cholesterol loading rescues OxLDL‐induced activation of endothelial Rho/ROCK/Akt/p27kip1 cascade
Authors: Zhang Chongxu , Levitan Irena
Published: November 2023

Oxidized modifications of LDL (oxLDL) are known to activate multiple signaling pathways that lead to impairment and disbalance of endothelial function impairment of the barrier function and including abnormal proliferation. It is generally believed that oxLDL exerts its effects on endothelial function via enhanced loading of cholesterol. Our studies, however, show that this is not the case. In contrast, we show that oxLDL and cholesterol loading have opposite effects on several key signaling events in human aortic endothelial cells (HAECs). Moreover, we show that cholesterol loading may rescue oxLDL‐induced effects on EC signaling. We also we provide comparative analysis of the effects of two major types of oxLDL, copper oxidized LDL (Cu‐oxLDL) and Lipoxygenase oxidized LDL (LPO‐oxLDL). Specifically, we show that both, Cu‐oxLDL or LPO‐oxLDL significantly increase Akt phosphorylation whereas inhibiting Akt with a specific inhibitor MK2206 blocks oxLDL‐induced increase in the proliferation of HAECs. Furthermore, blocking Rho with C3 or its downstream target ROCK with Y27632 significantly inhibits oxLDL‐induced Akt phosphorylation and cell proliferation induced by both Cu‐ and LPO‐oxLDL. In contrast, blocking Rac1 with MSC inhibitor has no effect neither on oxLDL‐induced Akt phosphorylation or cell proliferation of HAECs. Further evidence shows that oxLDL‐induced Rho/Akt pathway leads to downregulation of p27kip1, a well‐known negative regulator of cell proliferation. Most importantly, we also show that preloading cells with cholesterol prevents oxLDL‐induced activation of RhoA and oxLDL‐induced Akt phosphorylation. Furthermore, cholesterol pre‐loading also rescues oxLDL‐induced loss of p27kip1 expression. We propose that oxLDL impairs endothelial function by increasing the cellular content of oxysterols which disrupt the structure of endothelial membrane, an effect that can be repaired by an increase in cellular cholesterol.

Support or Funding Information

NIH grants HL‐073965 and HL‐083298 to I.L.
Development of a Left Ventricular Diastolic Stress Test
Authors: Samuel Thomas Jake , Beaudry Rhys , Haykowsky Mark , Sarma Satyam , Bhella Paul , Park Suwon , Liew Mooi , Nelson Michael D.
Published: November 2023

Left ventricular diastolic dysfunction is an important predictor of morbidity and mortality, and a major source of dyspnea upon exertion. Abnormal diastolic function, particularly during activities of daily living, is therefore an important contributor to reduced exercise tolerance and quality of life. Until recently, assessment of diastolic function has been limited to the resting condition, which often fails to recapitulate that which is experienced during daily activities. Accordingly, we sought to develop a simple— but effective— diastolic stress test which could easily be implemented into the clinical setting and differentiate patients with varying levels of diastolic dysfunction. For this investigation, we focused our attention on two known cardiovascular stressors: (a) isometric handgrip exercise (IHG), and (b) the cold pressor test (CPT). Both of these stressors are associated with robust and reproducible elevations in heart rate (HR) and arterial blood pressure (BP), without major changes in body and lung movement which are likely to be seen during dynamic exercise. We hypothesized that augmentation of the sympathetic nervous system and its associated cardiovascular response, would serve as a powerful diastolic discriminant. To test this hypothesis, we recruited six young, healthy women (age: 23 ± 4, BMI: 23.0 ± 2.8) and five elderly women without overt heart disease (age: 74 ± 7; BMI: 27.5 ± 3.0; two with Hypertension and one with Hypercholesterolemia). Heart rate, BP, Doppler mitral inflow velocities and annular tissue velocities were assessed at rest, following two minutes of IHG at 40% of maximum voluntary contraction, and following two minutes of a CPT. The major novel findings were two‐fold: First, IHG caused an increase in HR (ΔHR: 26 vs. 20bpm, young vs. old), and systolic BP (ΔSBP: 32 vs. 21mmHg, young vs. old), while the E/E′ ratio (a surrogate measure of left ventricular filling pressure) rose in the elderly population, with very little change in the young subjects (ΔE/E′: 0.87 vs. 1.80, young vs. old). Second, the CPT also increased HR (ΔHR: 6 vs. 10bpm, young vs. old) and systolic BP (ΔSBP: 17 vs. 42mmHg, young vs. old), while similarly differentiating the diastolic response in young vs. older participants (ΔE/E′: −0.07 vs. 1.47, young vs. old). Taken together, these preliminary data demonstrate both feasibility and efficacy of this novel diastolic stress test. More work is needed to apply this work to individuals at risk for or with heart failure and compare this approach to existing stress modalities.

Support or Funding Information

This work was supported by AHA 16SDG27260115 and the Harry S. Moss Heart Trust.
Tsg101 Regulates Rab11FIP3‐Mediated Endosomal Recycling of IGF‐1R in Physiological Cardiac Hypertrophy
Authors: Essandoh Kobina , Wang Xiaohong , Jiang Min , Mu Xingjiang , Peng Jiangtong , Li Yutian , Deng Shan , Salem Esam , Rubinstein Jack , Fan Guochang
Published: November 2023

Background

Development of physiological cardiac hypertrophy has primarily been ascribed to the insulin‐like growth factor 1 (IGF‐1) and its receptor, IGF‐1R and subsequent activation of the Akt pathway. Previous studies have demonstrated the effects of IGF‐1 on both pathological and physiological remodeling whereas IGF‐1R has consistently been linked to only physiological heart growth. Thus, the balance between de novo synthesis and recycling or degradation of IGF‐1R through the endosomal system is critical for physiological heart growth. However, regulation of endosome‐mediated recycling and degradation of IGF‐1R during physiological hypertrophy has not been investigated.

Methods & Results

In the current study, we sought to determine the role of endosome‐mediated recycling and degradation of IGF‐1R on physiological cardiac hypertrophy. Male FVB/n mice (7–8 weeks old) underwent intense treadmill exercise training for 1 week to induce physiological hypertrophy. We observed that mediators of recycling (Rab11a, Rab11FIP3) and degradation (Rab7) of endosomes were enhanced in exercise‐trained mice. Of importance, levels of tumor susceptibility gene 101 (Tsg101), a key member of the Endosomal Sorting Complex required for Transport (ESCRT), were dramatically elevated in hearts of exercise‐trained mice, compared to controls (n=9, p<0.01). To determine the role of Tsg101 on physiological hypertrophy, we generated a transgenic mice model with cardiac‐specific overexpression of Tsg101. These transgenic mice exhibited a physiological hypertrophy‐like phenotype at 8 weeks, evidenced by the absence of cardiac fibrosis, significant improvement of cardiac function, increased total and plasma membrane levels of IGF‐1R and increased phosphorylation of Akt. Mechanistically, we identified that Tsg101 interacted with IGF‐1R and Rab11FIP3, which constitutively binds to Rab11a at endosomal recycling compartments to initiate recycling of endosomes. In vitro, adenovirus‐mediated overexpression of Tsg101 in neonatal rat cardiomyocytes resulted in increased cardiomyocyte size, which was blocked by addition of monensin, an inhibitor of Rab11/FIP3‐endosome recycling. Furthermore, cardiac‐specific knockdown of Tsg101 showed a significant reduction in levels of Rab11a, Rab11FIP3, IGF‐1R and Akt phosphorylation. Most interestingly, Tsg101‐knockdown mice failed to develop cardiac hypertrophy after intense treadmill training.

Conclusion

Our data identify Tsg101 as a novel regulator of physiological cardiac hypertrophy through facilitating the Rab11FIP3‐mediated endosomal recycling of IGF‐1R.

Support or Funding Information

NIH 2R01HL‐087861
AICAR Treatment Does Not Prevent Increases in Exercise Capacity or Muscle Heat Shock Protein 25 with Treadmill Training in Mice
Authors: Godwin Kyle , Huey Kimberly
Published: November 2023

Exercise and 5‐aminoimidazole‐4‐carboxamide‐1‐β‐D‐ribofuranoside (AICAR) are agonists of AMP‐activated protein kinase (AMPK) and are used in type II diabetes treatment. Treatment effectiveness may be due to AMPK activation and up‐regulation of heat shock proteins (Hsps) in skeletal muscle, including Hsp25 and αB‐crystallin. Decreased Hsp25 expression in skeletal muscle is associated with insulin resistance in rats and data in both animals and humans suggests that increased Hsp expression in skeletal muscle may contribute to the prevention and treatment of insulin resistance. However, some evidence in both animals and humans suggests the combination of exercise and AMPK‐activating drugs such as AICAR may decrease exercise‐training adaptations. These experiments tested the hypothesis that AICAR + treadmill training (TM) would attenuate increases in exercise capacity, muscle force, and Hsp expression compared to training alone. Adult, male C57 mice were divided into 4 groups (n = 8–10/group): 1‐Placebo, 2‐AICAR, 3‐Placebo + TM, and 4‐Aicar + TM. Groups received daily placebo or AICAR with or without TM over 7 days. Plantarflexor muscle force and fatigue (% of max force after 10 contractions) were measured in vivo and exercise capacity was assessed with pre‐ and post‐treadmill tests. Muscle Hsp25 and αB‐crystallin protein levels were quantified with western blot. Data was statistically analyzed with 2‐way ANOVAs and post‐hoc tests. AICAR + TM did not affect training‐associated increases in exercise capacity compared to Placebo + TM (D time pre to post: 903 ± 164 vs. 1,188 ± 99 sec. for AICAR and TM, respectively, p<0.05). Muscle force was unchanged with AICAR in either TM or sedentary groups compared to placebo (Placebo: 1.2 ± 0.07 vs. 1.3± 0.07 and AICAR: 1.4 ± 0.08 vs. 1.5 ± 0.12 g/g body mass, for sedentary and TM, respectively, p<0.05). Fatigability was greater with AICAR in sedentary mice; however, AICAR + TM decreased fatigability compared to AICAR alone (p<0.05). TM increased Hsp25 levels independent of treatment (Placebo: 0.09 ± 0.01 vs. 0.15 ± 0.01 and AICAR 0.15 ± 0.02 vs. 0.17 ±0.02 AU, for sedentary and TM, respectively, p<0.05) and AICAR increased Hsp25 in the sedentary group compared to placebo (0.15 ± 0.02 vs. 0.09 ± 0.01 AU, p<0.05). AICAR prevented the TM‐associated increase in αB‐crystallin compared to placebo (Placebo: 0.11 ± 0.02 vs. 0.17 ± 0.01 and AICAR: 0.10 ± 0.01 vs. 0.01 ± 0.02 AU, for sedentary and TM, respectively, p<0.05). These findings suggest AICAR does not impair training‐associated increases in exercise capacity or Hsp25 muscle protein or negatively impact muscle force production. Taken together, these treatments could positively impact type II diabetics who often have reduced exercise capacity and skeletal muscle Hsp25 levels.

Support or Funding Information

Supported by APS UGSRF.
Effects of Eccentric and Concentric Cycling Exercise Regimens on Hypoxia‐Mediated Mitochondrial Bioenergetics of Platelets in Sedentary Males
Authors: Wu Yi Chen , Wang Jong‐Shyan
Published: November 2023

Rehabilitation Science, Medical College, Chang Gung University, Taoyuan City, Taiwan Physical exercise influences platelet function according to responses dependent on the type and intensity of exercise. Mitochondrial bioenergetics is a critical role in the platelets function. The purpose of this study was to investigate the effects of eccentric (ECE) and concentric (CCE) cycling exercise regimens on mitochondrial oxidative phosphorylation of platelets during hypoxic stress. Twenty‐two healthy sedentary men were randomized to either ECE (n=11) or CCE (n=11) group. These subjects progressively performed ECE or CCE at 45% to 70% VO2max on a bicycle ergometer for 40 min/day, 5 days/week for 6 weeks. Mitochondrial oxidative phosphorylation were measured by a high resolution respirometer (Oxygraph‐2k) at rest and after hypoxia exercise test (HE, 100W under 12% O2 for 40 min). The result demonstrated that both ECE and CCE regimens increased complex I‐linked O2 consumption rate (OCR), complex‐II linked OCR, fatty acid oxidation (FAO)‐linked OCR and GpDH‐linked OCR. Besides, ECE significantly diminished the suppressions of complex II‐ and GpDH‐linked respirations during HE. Hence, either ECE or CCE effectively enhances efficacy of mitochondrial oxidative phosphorylation in platelets. Moreover, ECE has more superior to alleviate the extent of mitochondrial dysfunction evoked by hypoxia stress.
Skeletal Muscle Adaptations to Exercise in a Pre‐clinical Model of Myotonic Dystrophy Type 1
Authors: Manta Alexander , Stouth Derek W , Rebalka Irena A , Kalmar Jayne M , Hawke Thomas J , Ljubicic Vladimir
Published: November 2023

Myotonic dystrophy type I (DM1) is the second most common muscular dystrophy (MD), and most prevalent adult form of MD. Caused by a CTG microsatellite repeat expansion in the 3′ untranslated region (UTR) of the DMPK gene, muscle weakness, wasting, myotonia, and insulin resistance most prominently characterize DM1. Recent studies investigating the therapeutic efficacy of exercise training in DM1 patients demonstrate that chronic physical activity can elicit some functional benefits. Enhancing our understanding of exercise‐induced alterations in DM1 biology may assist in the discovery of effective lifestyle and/or pharmacological interventions to mitigate DM1. Thus, the purpose of this investigation was to examine exercise‐induced skeletal muscle plasticity in a pre‐clinical model of DM1. Three groups of mice (3–6 months old, n = 10–14/group) were utilized: i) sedentary human skeletal actin‐long repeat (HSA‐LR) mice (SED‐DM1), ii) HSA‐LR mice with volitional access to a home cage running wheel for 6–8 weeks (EX‐DM1), and iii) sedentary wild‐type mice (WT). HSA‐LR animals are engineered to possess a CTG expansion of ~250 repeats in the 3′ UTR of the HSA gene. These mice best recapitulate the myopathy characteristic of the human disorder, and thus serve as the most heavily employed pre‐clinical model of DM1. EX‐DM1 animals ran 5.6 km/day, which is similar to the running volume of healthy, WT mice previously reported in the literature. Utilizing the pen test to examine muscular endurance and motor performance, the WT group exhibited a significantly higher score, as compared to SED‐DM1 mice. The pen test score was normalized in the EX‐DM1 group. EX‐DM1 mice also demonstrated rescued forelimb grip strength, which was 24% lower (p < 0.05) in the SED‐DM1 animals versus the WT group. Direct, in situ stimulation of the plantar flexor muscle group revealed that chronic exercise normalized the aberrant force‐frequency relationship observed between WT and SED‐DM1 groups. Furthermore, EX‐DM1 animals demonstrated a tendency for enhanced fatigue resistance relative to WT and SED‐DM1 mice during repetitive, electrical stimulation‐evoked muscle contractile activity in situ. Finally, preliminary results suggest that chronic exercise can diminish the severity of myotonic discharges observed in the muscle of DM1 mice. Collectively, our data suggest that chronic physical activity elicits numerous favorable adaptations in DM1 biology. Examination of the underlying molecular mechanisms driving this beneficial muscle remodelling is warranted.

Support or Funding Information

Natural Science and Engineering Research Council of Canada (NSERC)
Effects of Cycling Exercise on Mitochondrial Function and Efficacy of Peripheral Blood Mononuclear Cells Under Hypoxic Condition in Sedentary Men
Authors: Chang Shao‐Chiang , Wang Jong‐Shyan
Published: November 2023

Dysfunction of peripheral blood mononuclear cells (PBMCs) has been found in hypoxemic patients suffering from cardiopulmonary disorders or those exposed to hypoxic environments such as high altitudes. The mitochondrial bioenergetics of PBMCs serves a critical role in PBMC‐related immune function. The purpose of this study is to elucidate whether cycling exercise affect mitochondrial function and efficacy in PBMCs under hypoxic stress. Twelve sedentary males engaged in moderate exercise (60% VO2max) for 40 min while exposed to 12%O2 (HE) in a normobaric hypoxia chamber. Before and immediately after HE, Substrate‐Uncoupler‐Inhibitor Titrations (SUIT) protocols and TMRE, a mitochondrial membrane potential fluorescent dye, were applied on PBMCs and analyzed by a high resolution respirometer (OROBOROS Oxygraph‐2k). This study can be summarized as follows: (1) although no differences in routine or maximal mitochondrial O2 consumption rate, the HE heightened mitochondrial membrane potential in intact PBMCs and (2) the HE depressed pyruvate‐/glutamate‐dependent complex I (NADH‐related) O2 consumption rate in mitochondria of permeabilized PBMCs. Hence, we conclude that the HE is insufficient to influence maximal oxidative phosphorylation and electron transport capacity of mitochondria despite of depressing the NADH‐related mitochondrial efficacy in PBMCs.
PHYSIOLOGICAL, IMMUNOLOGICAL AND BIOCHEMICAL CHANGES IN ATHLETES DURING ADVENTURE RACE
Authors: Silva Romeu Paulo Martins , Silva Carolina Freitas , Bortolini Cristiane Soares Ferreira , Maggi Luiz Eduardo , Bortolini Miguel Junior Sordi , Vilaça Alexandre , Penha‐Silva Nilson
Published: November 2023

Objective

To investigate the occurrence of physiological, immunological and biochemical changes in adventure race.

Methods

Twenty‐five professional athletes, 15 men (age 31.4 ± 5.36 years) and 10 women (age 27.8 ± 5.18 years) traveled 460 km for 4 days long in an international edition of Ecomotion/Pro AR World. Blood and saliva samples were collected before (day 0) and after (day 4) the competition.

Results

There were risings of α‐amylase and cortisol levels in saliva after the race (p<0.05). The relative changing percentages of α‐amylase and cortisol were significantly higher in women than in men (p<0.05). There were less relative changing percentages of glucose and lactate levels in women than in men (p<0.05). After the competition leukocyte counts got higher compare to the beginning and among gender women got higher leukocyte counts than men (p<0.05).

Conclusion

Long‐lasting exercises with high intensity moments and little sleep, as adventure race, promoted an increased stress and changes in the immune system which can harm athletes' sports performance and health.

Support or Funding Information

FUNDAÇÃO DE AMPARO A PESQUISA DE MINAS GERAIS (FAPEMIG)
Influence of Muscle Fiber Recruitment on Local Vasodilation During Work‐Matched Exercise in Humans: Role for KIR Channel Activation
Authors: Terwoord Janee D. , Hearon Christopher M. , Racine Matthew L. , Luckasen Gary J. , Dinenno Frank A.
Published: November 2023

Under conditions of constant muscle contractile work, blood flow to active skeletal muscle is augmented with greater muscle fiber recruitment (MFR), but the mechanisms coordinating this response remain poorly understood. We tested the hypothesis that activation of inwardly‐rectifying potassium channels (KIR) underlies the augmented local vasodilation and hyperemia observed with increased MFR during work‐matched exercise in humans. We measured forearm blood flow (FBF; Doppler ultrasound) and calculated vascular conductance (FVC; quotient of FBF and mean arterial pressure) in 10 young adults (5 male, 5 female) during dynamic handgrip exercise protocols in which work was held constant but MFR was manipulated. Two bouts of rhythmic handgrip exercise (4 min each) were performed before and during local, intra‐arterial infusion of barium chloride (BaCl2) to inhibit KIR channels: 1) “High MFR,” in which participants used a pulley system to lift a load equivalent to 25% of maximal voluntary contraction (MVC) with a contraction‐to‐relaxation duty cycle of 1:7 seconds and 2) “Low MFR,” with contractions at 12.5% MVC and a 1:3 sec contraction‐to‐relaxation duty cycle. As expected, under control conditions, EMG activity of the flexor digitorum muscles was ~ 75% greater during the high vs. low MFR trial (P < 0.05). In control conditions, FBF (200 ± 28 vs. 166 ± 24 ml· min−1, P < 0.05) and FVC (207 ± 28 vs. 171 ± 24 ml· min−1· 100 mmHg−1, P < 0.05) were greater during the high vs. low MFR trials. Inhibition of KIR channels reduced steady‐state FBF and FVC during both high and low MFR trials, and abolished the differences between the two conditions (FBF: 143 ± 23 vs. 136 ± 21 ml· min−1, P = 0.36; FVC: 140 ± 21 vs. 134 ± 21 ml· min−1· 100 mmHg−1, P = 0.32) As such, the effect of KIR channel inhibition on FBF (−28 ± 7 vs. −17 ± 6%, P = 0.059) and FVC (−32 ± 6 vs. −21 ± 6%, P < 0.05) was greater in the high vs. low MFR condition. We conclude that augmenting MFR independent of contractile work elicits vasodilation via activation of KIR channels. We speculate that K+ released from skeletal muscle fibers upon repolarization may activate KIR channels and serve as a feed forward mechanism to increase muscle blood flow in proportion to the amount of muscle fibers recruited during exercise.

Support or Funding Information

Supported by NIH HL119337
The Effect of a High‐Fat Meal on Vascular Stiffness in Young Healthy Males
Authors: Tucker Wesley , Patik Jordan , Curtis Bryon , Park Suwon , Nelson Michael , Brothers R. Matthew
Published: November 2023

Consumption of a high‐fat meal (HFM) has been implicated in the pathogenesis of cardiovascular disease (CVD). While the exact mechanism remains unclear, postprandial lipemia, low‐grade inflammation, and endothelial dysfunction are contributing factors. Whether impairments in other indices of vascular function, such as central aortic pressures and arterial stiffness, also occurs following a HFM remains unknown and was the focus of this investigation. Six (n=6) healthy young males (27±5 years) were randomized to the following conditions, performed on separate days following an overnight fast: a) HFM challenge (928 kcal, ~50% fat) or, b) time control (fasting). Measures were assessed at baseline, 2h‐, and 4h post‐HFM or at a similar time point on the fasting day. Peripheral blood pressure, central aortic blood pressure and augmentation indices (augmentation pressure [AP] and augmentation index normalized for heart rate 75 bpm [Aix@75]) were non‐invasively assessed by brachial pulse wave analysis (SphygmoCor System, ATCor Medical, Australia). Arterial stiffness was assessed by carotid‐femoral pulse wave velocity (cf‐PWV) using applanation tonometry (SphygmoCor System, ATCor Medical, Australia). Endothelial function was assessed as flow‐mediated dilation (FMD) of the brachial artery using high‐resolution 2D and Doppler ultrasound (GE Logiq P5, GE Healthcare, UK) and normalized for shear rate area under the curve (AUC). Blood triglycerides (TG) were assessed at baseline and 2h post‐meal for each condition. Two‐way repeated measures ANOVA was used to detect time, condition, or time × condition interaction effects. Consistent with previous reports, consumption of the HFM significantly elevated blood TG relative to the time control day (HFM: 101±38 to 169±77 mg/dl, Fasting day: 107±32 to 92±31 mg/dl, P=0.007). Likewise, endothelial function also tended to be reduced 2h following the HFM (Baseline: 0.17±0.13, 2h: 0.12±0.07 % FMD/shear AUC) compared to the fasting day which tended to increase at 2h (Baseline: 0.12±0.05, 2h: 0.15±0.10 % FMD/shear AUC) (p=0.09). In contrast to our hypothesis, the HFM had no effect on central systolic BP (p=0.43), central diastolic BP (p=0.81), AP (p=0.20), Aix @75 (p=0.21) and cf‐PWV (p=0.20). These preliminary data suggest that central aortic blood pressures and arterial stiffness do not change acutely following a HFM in young healthy males.
The Effect of an Antioxidant Cocktail on Endothelial Function in Healthy Caucasian and African American Men
Authors: Patik Jordan C , Vranish Jennifer R , Curtis Bryon M , Kaur Jasdeep , Young Benjamin E , Fadel Paul J , Brothers R. Matthew
Published: November 2023

African Americans (AA) have elevated risk of developing a variety of cardiovascular and metabolic diseases relative to Caucasian Americans (CA). The reason for this elevated disease risk in the AA population is multifactorial with impaired vascular function being a key contributing factor. The exact mechanism(s) leading to vascular dysfunction in AA are not well understood; however, elevated oxidative stress is likely a factor. We have recently demonstrated that local administration of the superoxide dismutase mimetic Tempol improves endothelial function in the cutaneous microvasculature of AA. However, the systemic effects of antioxidants on indices of vascular function are not well characterized in this population. Therefore, the purpose of the current investigation was to test the hypothesis that an antioxidant cocktail (AOX), previously shown to decrease superoxide production in young, healthy men, will acutely augment endothelial function in AA as determined by flow mediated dilation (FMD). Four healthy, college‐aged AA men and 3 age‐matched CA men were studied on two mornings after an overnight fast separated by ~1 week. Upon arrival to the lab, either AOX (vitamin C: 2g, vitamin E: 150IU, and coenzyme Q10: 100mg) or a placebo (three sugar pills) was given in a randomized order. 120min after treatment, following a 2 min baseline a cuff placed 3cm distal to the elbow was inflated to 220 mmHg for 5 min and then rapidly deflated. Post‐occlusion data was collected for an additional 3 min. Brachial artery diameter and blood velocity were continuously assessed via duplex Doppler ultrasound. AOX had no effect on FMD in either group (AA Placebo: 6.6 ± 2.1; AA AOX: 5.9 ±1.7; CA Placebo: 3.6 ± 1, CA AOX: 5.0 ± 1.5% FMD, P=0.32). This result remained when FMD was corrected for hyperemic shear rate area under the curve (AUC) (P=0.11). In contrast, the hyperemic velocity AUC was augmented by AOX in the AA (Placebo: 1014.7 ± 537, AOX: 1944 ± 564 a.u., P=0.03) but not in the CA (Placebo: 1781.3 ± 362, AOX: 1468.1 ± 644 a.u., P=0.54) suggesting AOX improves microvascular reactivity in AA. Collectively, these preliminary findings suggest that AOX does not affect conduit artery endothelial function in AA or CA as assessed by FMD. However, AOX augments microvascular function in skeletal muscle of AA. These data are consistent with our previous findings suggesting oxidative stress attenuates microvascular function in healthy, young AA.