bluuebunny/crossref_metadata_2025 huggingface dataset:
Steady State vs. Pulsatile Blood Pressure Component and Regional Cerebral Perfusion
Authors: Laosiripisan Jitanan , Haley Andreana P , Tanaka Hirofumi
Published: November 2023

Arterial blood pressure can be divided into steady state component that is determined by mean arterial pressure and pulsatile component that is explored by pulse pressure. The brain is a region that has vascular bed with high blood flow and low vascular impedance, which is affected greatly by excessive and/or fluctuated blood pressure. Indeed high blood pressure is related to impaired cognitive function. In the present study, we aimed to determine the relationship between steady state and pulsatile blood pressure components and regional cerebral perfusion at 10 regions of interest. A total of 52 apparently healthy adults aged 40–60 years were studied. All the subjects had normal global cognitive function as assessed by the Mini‐Mental Status Exam score greater than 28. Regional cerebral perfusions were measured using arterial spin labeling technique in 10 a priori regions of interest. Correlational analyses revealed 5 regions that their cerebral perfusion values were significantly and inversely associated with blood pressure components (i.e., hippocampus, anterior white matter, posterior insula, central white matter, and occipitoparietal area). After controlling for potential confounding factors (i.e., age, sex, race, education, and BMI) in multiple regression analyses, however, significant associations were observed only in 3 regions (i.e., hippocampus, posterior insula, and occipitoparietal area). In general, the strengths of associations with regional cerebral perfusion were greater with pulse pressure than with mean arterial pressure. Central (carotid) pulse pressure did not record greater associations compared with peripheral (brachial) pulse pressure. In conclusion, pulsatile component of blood pressure was significantly and inversely related to regional cerebral perfusion in the areas that are affected by fluctuating blood pressure in apparently healthy adults with normal cognitive function.
Reactivity of Basilar and Circle of Willis Arteries Measured Simultaneously at 7 Tesla
Authors: Shoemaker Leena , Al‐Khazraji Baraa , Gati Joe , Tzekeres Trevor , Shoemaker Kevin
Published: November 2023

The subcortical conduit vessels contribute significantly to the total cerebral vascular resistance making knowledge regarding their vasoreactivity to physiological stimuli a requirement when attempting to understand regional brain perfusion. Recent evidence points to significant dilatory and constrictor potential in the middle cerebral artery. However, reactivity of the remaining conduit arteries remains poorly understood due to a need for improved imaging methods that can assess these vessels simultaneously while each receives the same stimulus. In this study we characterize the basilar and all Circle of Willis conduit arteries' reactivity to changes in end‐tidal CO2 (ETCO2). All imaging was performed on a 7T Siemens MAGNETOM neuro‐optimized MRI using an 8‐channel transmit, 32‐channel receive head coil. Cross‐sectional area (%ΔCSA) measurements were evaluated from images collected using a T1‐weighted 3D SPACE pulse sequence, optimized to produce black‐blood and high signal contrast between vessel lumen and surrounding tissue. The acquisition was tuned to produce high‐resolution (0.5mm isotropic) information with no inflow signal (TE=8.2ms, TR=700ms, FOV=224mm sagittal, radial trajectory, iPat=2) and a whole‐brain acquisition time of 5.63 minutes. Collection of isotropic data allowed us to arbitrarily re‐orient the image data to evaluate the relative change in cross‐sectional area (%ΔCSA) of the subcortical conduit arteries perpendicular to the direction of flow. Change in ETCO2 (ΔETCO2, ADInstruments) and %ΔCSA data were produced from 7 healthy individuals (age range, 18–23 years). Cerebrovascular CO2 reactivity was calculated as %ΔCSA/ΔETCO2. All 9 subcortical conduit arteries (basilar, right and left internal carotid, as well as the right and left posterior, middle and anterior cerebral arteries) were evaluated during normocapnia (37±6 mm Hg), hypercapnia (51±6 mmHg achieved by breathing a gas mixture of 5% CO2, balance oxygen), and hypocapnia (27±4 mmHg achieved by hyperventilation). Cerebral artery reactivity to hypercapnia exhibited a range of dilation from 0.27%/mm Hg in the right internal carotid artery to 2.5%/mm Hg in the left anterior cerebral artery. In response to hypocapnia, cerebral artery vasoconstriction ranged from 1.1%/mm Hg in the left anterior cerebral artery to 3.2%/mm Hg in the right posterior cerebral artery. This study demonstrated the heterogeneous cerebrovascular reactivity to hypercapnia and hypocapnia across the nine subcortical conduit arteries.

Support or Funding Information

Canadian Institute of Health Research (201503MOP‐342412‐MOV‐CEEA)
Pro‐atherogenic disturbed flow increases endothelial stiffness via enhanced CD36/Cav1‐ mediated oxLDL uptake
Authors: LeMaster Elizabeth , Shentu Tzu‐Pin , Huang Ru‐Ting , Zhang Chongxu , Adamos Crystal , Fancher Ibra , Ng Carlos , Christoforidis Theodore , Subbaiah Papasani , Eddington David , Cho Michael , Fang Yun , Minshall Richard , Levitan Irena
Published: November 2023

Objective

Disturbed flow (DF) is known to induce endothelial dysfunction and synergistically with plasma dyslipidemia promote plaque formation. Little is known, however, about the synergistic impact of DF and dyslipidemia on endothelial biomechanical properties. Our goal was to determine the impact of DF on endothelial stiffness and evaluate the role of dyslipidemia/oxidized low density lipoprotein (oxLDL) in this process.

Methods and Results

Endothelial elastic modulus of intact mouse aortas ex vivo and of human aortic ECs (HAECs) exposed to laminar or disturbed flow in vitro was measured using atomic force microscopy. The endothelial monolayer of the aortic arch (AA) was found to be significantly stiffer than the descending aorta (DA) (4.2+1.1 vs. 2.5+0.2 kPa for AA vs. DA) in mice maintained on low fat diet (LFD). This effect was significantly exacerbated by a short‐term high‐fat diet (HFD) (8.7+2.5 vs. 4.5+1.2 kPa for AA vs. DA). Exposure of HAECs to DF in vitro resulted in a 50% increase in oxLDL uptake and significant endothelial stiffening in the presence but not in the absence of oxLDL. DF was shown to increase the expression of oxLDL receptor CD36 and the downregulation of CD36 abrogated DF‐induced endothelial oxLDL uptake and stiffening. ECs deficient in caveolin1 (Cav1) had no significant oxLDL uptake and no DF‐induced EC stiffening. Furthermore, genetic deficiencies of CD36 and of Cav1 abrogated endothelial stiffening in the aortic arch ex vivo in mice fed either LFD or HFD.

Conclusions

Disturbed flow facilitates endothelial CD36/Cav1‐dependent uptake of oxidized lipids resulting in a local increase of endothelial stiffness in pro‐atherogenic areas of the aorta.

Support or Funding Information

This study is supported by NIH grants HL‐073965 (IL,DE), HL‐083298 (IL,RM,MC,PVS), and R00 HL‐103789 (YF); AHA MWA Pre‐doctoral Fellow 14PRE20490156 (EL) and the Chicago Biomedical Consortium with support from the Searle Funds at the Chicago Community Trust (DE).
ENDOTHELIAL FUNCTION AND ANTIOXIDANT CAPACITY ARE IMPAIRED IN ADULTS WHO REPORT ADVERSE CHILDHOOD EVENTS
Authors: Miguelez Paula Rodriguez , Looney Jacob , Blackburn Marsha , Thomas Jeffrey , Pollock Jennifer , Harris Ryan
Published: November 2023

INTRODUCTION

Adverse childhood events (ACEs), comprised of adversity early in life among others, have been associated with the development of cardiovascular disease (CVDs) during adulthood. Endothelial dysfunction plays a pivotal role in the etiology of CVDs and has been associated with higher production of reactive oxygen species (ROS). Apart from the body's endogenous ability to counteract ROS, the consumption of exogenous antioxidants also enhance the capacity to scavenge free radicals and improve endothelial function. Whether or not ACEs predisposes adults to a reduction in antioxidant capacity and an impaired endothelial function has yet to be investigated.

PURPOSE

This study sought to test the hypotheses that 1) ACEs contribute to a lower total antioxidant capacity and an impaired endothelial function, and 2) the ingestion of oral antioxidants will increase antioxidant capacity and improve endothelial function.

METHODS

Forty‐four young adults (34 ± 3 yrs), with no evidence of overt CVDs, were divided into two groups based on their self‐reported ACE questionnaire score: HiA: ACE score ≥ 4 (n=15) or NoA: ACE score = 0 (n=29). Utilizing a randomized, placebo‐controlled, crossover experimental design, flow‐mediated dilation (FMD), an index of endothelial function, and plasma total antioxidant capacity (TAC) were assessed in all participants at baseline and following ingestion of either placebo (P) or an antioxidant cocktail (AOC: vitamin C, vitamin E and α‐lipoic acid) on separate days.

RESULTS

At baseline, TAC tended to be lower in HiA compared with NoA (2.01 ± 0.42 vs. 2.47 ± 0.93 mM; p=0.063, respectively). FMD was significantly (p=0.026) lower in HiA (6.5 ± 3.0 %) compared to NoA (8.5 ± 2.8 %). In addition, a significant moderate correlation between TAC and FMD (r=0.350; p=0.022) was identified at baseline. After the AOC, a significant increase (p=0.049) in TAC was only observed in NoA compared with HiA (ΔTAC: 0.29 ± 0.01 vs. 0.09 ± 0.02 mM, respectively). Likewise, FMD was significantly (p=0.037) higher after the AOC in NoA (ΔFMD: 1.5 ± 0.2 %) and unchanged in HiA (ΔFMD: 0.1 ± 0.1 %). No differences in either TAC or FMD (p≥0.321) were observed after the P in either group.

CONCLUSION

For the first time, we have documented that adults who reported ACEs exhibit a lower antioxidant capacity and impaired endothelial function compared with adults who did not report ACEs. However, an acute AOC was only able to improve antioxidant capacity and endothelial function in those individuals who did not experience ACEs. Future studies are warranted to evaluate possible therapies to improve antioxidant capacity and vascular function in adults who experienced ACEs.

Support or Funding Information

Support in part by NIH/NHLBI P01HL06999 (RAH).
HDAC1, NOS3, and circadian clock gene expression in the endothelium
Authors: Pati Paramita , Pollock David , Pollock Jennifer
Published: November 2023

Histone deacetylases (HDACs) are in a family of enzymes that have important roles in a number of biological processes. Previous work in our lab has shown that upregulation of HDAC1 deacetylates endothelial nitric oxide synthase (NOS3) and results in decreased NO production in bovine aortic endothelial cells. HDACs have also been demonstrated to serve as regulators of circadian clock gene function. Clock, a core component of the molecular circadian clock, is a histone acetyltransferase, thus acetylation pathways are implicated in the circadian control mechanism. More recently, HDAC1 has been implicated in the circadian clock negative feedback mechanism. Circadian clock genes have an important influence in the endothelium as blood vessels from mice with Bmal1 knockout (Bmal1‐KO) exhibit endothelial dysfunction and reduced NO signaling. We hypothesized that HDAC1 expression displays circadian variation similar to NOS3 and that inhibition of HDAC1 would improve circadian clock gene oscillation in primary mouse aortic endothelial cells (MAECs). Further, we also hypothesized that HDAC1 inhibition improves endothelial NOS‐dependent function in aortic rings from Bmal1‐KO mice. To determine whether basal HDAC1 expression displays circadian variation, protein was harvested from confluent MAECs at 4 hr intervals over a 12 hr period between 10 AM and 10 PM. Western blot analysis (n=3 per time point, p=0.0002) revealed significantly increased HDAC1 expression over the course of the day, with 5‐fold greater expression at 10 PM (0.5±0.05, 1.2±0.28, 2.3±0.19, 2.6±0.16 relative densitometric units). Similarly, nighttime NOS3 protein expression was also elevated relative to daytime expression (p=0.0048). siRNA knockdown of HDAC1 resulted in a 50% reduction in HDAC1 protein expression. Protein expression was quantified relative to actin. 24 hrs after transfection with siRNA, cells were serum shocked with 50% horse serum for circadian synchronization and harvested at 6 hr intervals for 30 hrs (n=4 per group at each time point). QPCR analysis revealed more robust oscillation of core clock genes with HDAC1 siRNA relative to the scramble control. The trough in Bmal1 and Clock expression was at ZT20 whereas Per2 expression peaked at ZT20. At ZT14 Bmal1 expression peaked and Per2 expression showed a trough. Additionally, with HDAC1 knockdown NOS3 mRNA expression peaked at ZT8 and troughed at ZT14 in contrast to the scramble control which did not show temporal variation in mRNA expression. Incubation with the HDAC1 inhibitor MS‐275 (8uM for 1 hr) did not improve the drastically impaired endothelium‐dependent relaxation to acetylcholine in aortic rings from Bmal1‐KO mice while endothelium‐independent relaxation was intact and unaffected by MS‐275 in response to the exogenous NO donor sodium nitroprusside. These findings indicate that HDAC1 displays temporal variation and affects circadian clock and NOS3 gene expression in endothelial cells.
Voluntary Exercise Enhances Cardiac Growth in Response to Chronic β‐Adrenergic Receptor Stimulation
Authors: Lenth Moira Kate O'Connor , Soo Sherilynn , Luckey Stephen , McLaughlin Nathan
Published: November 2023

Exercise has been demonstrated to protect the heart against the adverse effects of cardiovascular disease. Given the prevalence of cardiovascular disease (CVD), the role that exercise plays in protecting the heart prior to CVD is an important area of research given its clinical implications. Therefore, this study aims to examine how voluntary exercise can impact the progression of heart failure. To do this, a mouse model with nine‐week‐old female and male CB6F1 hybrid mice was used to test the impact of voluntary wheel running on heart failure resulting from chronic β‐adrenergic receptor stimulation. Mice either exercised for five weeks on a voluntary wheel (EX) or remained sedentary during the duration of the study (SED). After three weeks, both SED and EX mice were administered either vehicle (VEH) or isoproterenol (ISO, 30mg/kg/day) via an osmotic pump for two weeks. In the EX group, mice were further divided into two groups: one that continued exercising while receiving ISO (EX+ISOe) and one that became sedentary (EX+ISOs). At the end of the treatment, morphometric data was collected including heart weight‐to‐tibia length (HW/TL). Significant cardiac growth was observed in the both males and females in the mice that exercised for the entire five weeks (EX+VEH) as compared to their sedentary counterparts (SED+VEH). Additionally, male and female mice that were sedentary for 21 days and received ISO (SED+ISO) had increased heart size in comparison to the control group (SED+VEH). In male and female EX+ISOs mice, both sexes had similar cardiac growth to the SED+ISO group. Finally, cardiac growth in both EX+ISOe males and female was greater than any of the other groups of mice. Our results suggest that there is an additive effect of both exercise and ISO causing this significant increase in size. This data is in contrast to previous studies that demonstrated forced exercise reduced cardiac hypertrophy in response to chronic β‐adrenergic receptor stimulation. To better understand these differences in our study, we are currently performing quantitative PCR on left ventricular tissue to identify changes in a number of hypertrophic gene markers. These investigations will allow us to better understand the cardioprotective effects of exercise on the progression of heart failure.

Support or Funding Information

Murdock Faculty Start‐up Funding (SL)
Multiple Sclerosis Patients Do not Show Changes in Wave Intensity Analysis Following Home‐Based Exercise
Authors: Griffith Garett , Wee Sang Ouk , Klaren Rachel , Motl Robert , Baynard Tracy , Fernhall Bo
Published: November 2023

Physical inactivity and a host of other behavioral and lifestyle characteristics result in increased prevalence rates of cardiovascular disease (CVD) among multiple sclerosis (MS) patients. Non‐invasive assessment techniques can quantify arterial dysfunction, and have been shown to detect positive arterial responses to aerobic exercise training. Wave intensity analysis (WI), an ultrasound measurement which serves as a surrogate measure of ventricular‐arterial interaction, is one such non‐invasive methodology. Our purpose was to determine if WI changes as a result of home‐based aerobic exercise in MS patients. Participants completed either a 3 month home‐based aerobic exercise (N=26, 49±11 years) or stretching (N=22, 43±13 years) intervention. Exercisers completed 3 days per week of moderate intensity cycling (progressing from 40% to 60% of aerobic capacity and from 10 to 30 minutes), and stretchers completed 3 days per week of a whole body routine (progressing from 5 to 20 stretches). Ultrasound assessments of the carotid artery were performed after 15 minutes of supine rest at baseline and after 12 weeks. Carotid blood pressures were measured with applanation tonometry and entered into the ultrasound. P < 0.05 for all analyses. Group differences at baseline were found for carotid artery diameter difference, WD1, and velocity range. No Time*Group interactions were found for any WI variables. See table 1 for carotid artery WI analysis results. Our data suggest that 3 months of home‐based aerobic exercise at moderate intensity is insufficient to impact wave intensity in multiple sclerosis patients. Since WI is able to assess ventricular‐arterial interaction at a specific point in the arterial tree, future studies in this population should consider assessing WI in locations different than the carotid artery. Additionally, effects on WI of increased volume of aerobic exercise have yet to be explored in this population.

Support or Funding Information

This project was supported by the National Multiple Sclerosis Society RG 4702A1/2.

Data are presented as Mean ± SD.

Baseline
12 Weeks

Stretching (N=22)
Exercise (N=26)
Stretching (N=22)
Exercise (N=26)

Diameter Δ (cm)#
0.50 ± 0.11
0.41 ± 0.14
0.49 ± 0.13
0.43 ± 0.15

1st (w1)
9152.3 ± 5901.4
7431.3 ± 4925.5
10500.0 ± 8296.1
6975.8 ± 6361.3

Wd1 (m/s3)#
19.7 ± 16.1
12.5 ± 9.7
18.7 ± 13.6
11.7 ± 11.6

2nd (w2)
552.3 ± 648.9
1275.0 ± 1246.2
940.9 ± 970.6
1162.5 ± 1203.0

Wd2 (m/s3)
1.0 ± 1.3
1.9 ± 2.0
1.5 ± 1.5
1.8 ± 1.9

Velocity Range (cm/s)#
44.5 ± 16.9
35.3 ± 13.7
48.7 ± 14.5
41.0 ± 14.5

* Interaction (Time*Group).

Difference between Stretching and Exercise at baseline.
Relationships between Functional Capacity and Hemodynamic Characteristics in Patients with Peripheral Arterial Disease
Authors: Fu Tieh‐Cheng , Lin Yu‐Ching , Soh‐Ching NG , Wang Jong‐Shyan , Yeh Chi‐Hsiao
Published: November 2023

Peripheral arterial disease (PAD) causes chronic narrowing of arteries and reduces the capacity of blood flow to the legs, which can progress in severity to greatly limit mobility in the patients. What kind of exercise test serves as a functional indicator of PAD progression needs for further investigation. Sixty‐four patients with PAD were recruited and subsequently performed three exercise tests [6 minutes walking test (6MWT), 3 minutes stepping test (3MST) and cardiopulmonary exercise test on a bicycle ergometer (CPET)]. Magnetic resonance angiography (MRA) was adopted to measure hemodynamic characteristics, whereas sphygmomanometry and duplex ultrasonography were employed to assess arterial brachial index (ABI). The results demonstrated that the values of ABI were associated with the levels of blood flow in posterior tibial artery/peroneal artery/femoral artery, but not relative to the measures of CPET, 6MWT or 3MST. However, the initial pain time in CPET or 3MST was associated with the initial pain distance of 6MWT. Additionally, functional parameters of CPET and 6MWT were positively correlated with hemodynamic parameters of MRA. Therefore, we conclude that functional parameters obtained from 6MWT and CPET effectively predict hemodynamic characteristics in patients with PAD.

Support or Funding Information

Chang Gung Memorial Hospital, Keelung, Taiwan (CMRPG2F0191)Ministry of Science and Technology, Taiwan (105‐2314‐B‐182A‐130‐)
Parkin‐Mediated Mitophagy in Skeletal Muscle with Endurance Training
Authors: Chen Chris , Hood David
Published: November 2023

Skeletal muscle is a highly adaptive tissue that is responsive to environmental cues. With exercise training, intracellular signaling pathways are activated that promote the synthesis of mitochondria, a process termed biogenesis. The increased number of mitochondria allows for efficient substrate utilization and greater muscle endurance. However, little is known regarding mitochondrial turnover with training. Mitophagy is a process involved in the specific elimination of dysfunctional mitochondria. It is unclear if mitophagy undergoes adaptive responses in muscle with training. Parkin is a ubiquitin ligase involved in neuronal mitophagy but its role in muscle remains inconclusive. To investigate Parkin's role in muscle with exercise training, we subjected 3‐month‐old wild‐type (WT) and Parkin knock out (KO) mice to a 6‐week voluntary wheel running training paradigm. Overall, WT mice ran 28% longer than KO mice in average total running distance. Endurance training elicited 1.5‐ and 1.4‐fold increases in whole muscle mitochondrial content in WT and KO mice, respectively. Furthermore, subunits I and IV of cytochrome c oxidase and mitochondrial transcription factor A were augmented on intermyofibrillar mitochondria (IMF) isolated from hindlimb muscles of trained WT animals. This was supported by a 1.7‐fold increase in State 3 (active) IMF respiration in trained WT mice. Following 6 weeks of training, both Parkin KO and WT mice exhibited 2‐fold increases in running performance during an exhaustive bout of exercise, compared to their untrained counterparts. Interestingly, basal mitophagy flux and mitochondrial localization of LC3II were augmented by 1.5‐fold in muscle of trained WT mice. However, this increase was abolished in KO animals. Acute exercise‐induced a 2‐fold increase in LC3‐II flux in untrained WT mice, which was attenuated to a 1.6‐fold increase with training. In contrast, acute exercise decreased mitophagy flux in untrained and trained KO muscle by 10–20%. Our findings indicate that the localization of autophagy proteins to mitochondria is increased in trained muscle, but is reduced when Parkin is absent. However, during exercise‐induced mitophagy, an attenuation of autophagy proteins localized on mitochondria occurs, which is partly Parkin‐mediated. With training, exercise‐induced mitophagic signaling is reduced, likely due to enhanced mitochondrial biogenesis, leading to improved endurance.

Support or Funding Information

Supported by NSERC.
Effect of Exercise Training on Mobilization and Functionality of Endothelial Progenitor Cells undergoing Hypoxic Stress
Authors: Wang Jong‐Shyan
Published: November 2023

Exercise training improves endothelium‐dependent vasodilation, whereas hypoxic stress causes vascular endothelial dysfunction. This study investigates how high‐intensity interval (HIT) and moderate intensity‐continuous (MCT) exercise training affect mobilization and functionality of endothelial progenitor cells undergoing hypoxic stress. Forty healthy sedentary males were randomized to engage either HIT (3‐minute intervals at 40% and 80%VO2max, n=20) or MCT (sustained 60%VO2max, n=20) for 30 minutes/day, 5 days/week for 6 weeks. Characteristics and functionality of circulating progenitor cells (CPCs) under hypoxic exercise (HE, 100W under

12%O2) were determined before and after various interventions. The results demonstrated that both HIT and MCT regimens significantly increased endothelial progenitor cell (EPC) cell count, whereas only HIT considerably increased hemangioblast stem cell (HSC) and endothelial precursor cell (CEP) cell counts at rest and following HE. Moreover, HIT, rather than MCT, significantly diminished the extent of endothelial shedding caused by HE. The HIT regimen also increased resting and HE‐related tube cover area, tube length, and tube count of CPCs. However, MCT did not change migration of CPCs and modestly increased resting tube formation of CPCs at rest or following HE. Therefore, we conclude that HIT is superior to MCT for enhancing functionality of CPCs and suppressing endothelial injury undergoing hypoxia.

Support or Funding Information

National Science Council of Taiwan (grant number NSC 100‐2314‐B‐182‐004‐MY3), Chang Gung Medical Research Program (grant number CMRPD1A0132 and CMRPD2C0161), and Healthy Aging Research Center, Chang Gung University (grant number EMRPD1A0841)
Acute Folic Acid Ingestion Improves Skeletal Muscle Blood Flow during Graded Handgrip and Plantar Flexion Exercise in Aged Humans
Authors: Romero Steven A. , Gagnon Daniel , Adams Amy N. , Cramer Matthew N. , Jaffery Manall F , Kouda Ken , Moralez Gilbert , Crandall Craig G.
Published: November 2023

Skeletal muscle blood flow is attenuated in aged humans performing aerobic exercise, which is thought to be due, in part, to impaired local vasodilatory mechanisms. Recent evidence suggests that folic acid improves cutaneous vasodilation during localized and whole‐body heating through nitric oxide‐dependent mechanisms. However, it is unclear if folic acid can improve vasodilation in other vascular beds during conditions of increased metabolism (i.e. exercise). Therefore, the purpose of this study was to test the hypothesis that acute folic acid ingestion would improve skeletal muscle blood flow in aged adults during graded handgrip and plantar flexion exercise via increased vascular conductance. Eight healthy aged adults (2 males; age 68 ± 5 years; height 165 ± 6 cm; weight 70 ± 8 kg; mean ± SD) performed graded handgrip (3, 6, 9 kg) and plantar flexion (5, 9, and 14 kg) exercise before (control) and two hours after folic acid ingestion (5 mg). Exercise was performed using a duty cycle of 1 s contraction and 2 s relaxation (20 contractions min−1). Steady‐state forearm (brachial artery) and leg (superficial femoral artery) blood flow and diameter were measured via Duplex ultrasonography. Vascular conductance was calculated as flow/pressure and multiplied by 100. Blood flow and vascular conductance are presented as the mean response across exercise intensity. Acute folic acid ingestion increased serum folate (control 12.8 ± 1.7 ng ml−1 vs folic acid 493.3 ± 85.5 ng ml−1; P < 0.01). During handgrip exercise, folic acid ingestion increased forearm blood flow (control Δ 91 ± 7 ml min−1 vs folic acid Δ 113 ± 9 ml min−1; P < 0.01) and vascular conductance (control Δ 97 ± 7 ml min−1 100 mmHg−1 vs folic acid Δ 114 ± 8 ml min−1 100 mmHg−1; P < 0.01). Similarly, during plantar flexion exercise, folic acid ingestion increased leg blood flow (control Δ 226 ± 19 ml min−1 vs folic acid Δ 284 ± 21 ml min−1; P < 0.01) and vascular conductance (control Δ 244 ± 20 ml min−1 100 mmHg−1 vs folic acid Δ 281 ± 20 ml min−1 100 mmHg−1; P = 0.01). Taken together, acute folic acid ingestion improves blood flow to active skeletal muscle via improved local vasodilation in aged adults.

Support or Funding Information

Funded by National Institutes of Health (GM 068865 & GM 117693).
Measurement of Skeletal Muscle Blood Flow with Near‐infrared Diffuse Correlation Spectroscopy
Authors: Rosenberry Ryan , Ganesh Chandan , Tian Fenghua , Nelson Michael D.
Published: November 2023

Direct continuous noninvasive measurement of local muscle blood flow in humans remains limited. Conventional measurements of limb blood flow, such as Doppler ultrasound or venous occlusion plethysmography, measure changes in bulk conduit flow and do not provide regional information. Near‐infrared diffuse correlation spectroscopy (DCS) is an emerging technique for non‐invasive measurement of local muscle blood flow at the microvascular level. In order to better understand the strengths and limitations of this novel approach, we performed a validation study by comparing muscle blood flow changes measured by DCS and Doppler ultrasound during exercise. Ten subjects were recruited for this study (age: 27±3 yrs; female/male: 1/9; BMI: 27.0±3.6 kg/m2). The DCS probe was affixed to the forearm over the belly of the flexor digitorum profundus. Brachial artery blood velocity and diameter were measured with Doppler ultrasound, integrated, and reported as brachial artery blood flow. After a brief period of rest, each participant performed rhythmic handgrip exercise at 20% and 50% of their maximum voluntary contraction (MVC). As expected, brachial artery blood flow increased significantly from baseline by 312±56% at 20% MVC, and 613±90% at 50% MVC. Blood flow index (BFI), the primary output from DCS, shared a similar change from baseline, increasing 112±18% and 262±35%, respectively. To more appropriately compare these two approaches, the data were normalized to each person's individual maximum for each respective technique. Remarkably, the increase in skeletal muscle blood flow was strikingly similar between the two techniques, when reported in normalized units (20%: 0.42±0.03 vs. 0.45±0.03; 50%: 0.69±0.04 vs. 0.79±0.02, DCS vs. BA flow, respectively). The change in skeletal muscle blood flow by DCS and Doppler ultrasound were also strongly correlated (r2=0.77, P<0.001). Taken together, these data show that DCS and Doppler ultrasound quantify the same temporal dynamics of skeletal muscle blood flow during exercise. While these results are indeed encouraging, more work is needed to fully validate this approach for measuring local microvascular blood flow in humans.

Support or Funding Information

This work was support by an Interdisciplinary Research Program grant from the University of Texas at Arlington.
Basal Endothelial Cell Autophagy is Elevated in Trained vs. Sedentary Mice
Authors: Cho Jaemin , Kim Ji‐Seok , Allsop Jeff , Bean Tyler , Bonn Trevor , Hestwood Gabby , Yang Kevin , Drummond Micah , Babu Pon Velayutham Anandh , Symons J David
Published: November 2023

Autophagy is a process whereby damaged cellular cargo is delivered to the lysosome for degradation and eventual recycling or removal. A reduction of autophagy‐related (Atg) mRNA and protein expression in endothelial cells (ECs) from old rodents and humans is associated with arterial dysfunction. One study reports increased indices of autophagy in aortae from trained vs. sedentary rats (Sun et al., Cardiovascular Res, 2013), but the cellular subtypes were not evaluated. Exercise‐training could improve vascular health by upregulating EC autophagy. We hypothesized that exercise‐training increases basal EC autophagy. Five‐month old male C57Bl6 mice were treadmill‐trained (ETR, n=6, 32±1 g) or remained sedentary (SED, n=5, 32±1 g) 6 days per week. After 10‐weeks, total workload performed during a maximal exercise test was greater (p<0.05) in ETR (3.63±0.48 kgm) vs. SED animals (1.08± 0.22 kgm). 24 hours following the total workload test, soleus muscle, iliac artery, carotid artery, and aorta were obtained. The respiratory control ratio (RCR, state III to state IV respiration) was greater (p<0.05) in soleus from ETR (2.04±0.14) vs. SED mice (1.31±0.16). Citrate synthase activity (μmol/min/g) was greater (p<0.05) in soleus from ETR (0.99 ± 0.07) vs. SED (0.54 ± 0.14) mice. These findings verify the efficacy of our training protocol. ECs and media + adventitia (M+A) were obtained from the iliac and carotid arteries. mRNA expression was quantified by real‐time RT‐PCR using SYBR green fluorescence. Cycle threshold (Ct) values were normalized to the housekeeping gene 18S. Purity of the EC and M+A fractions obtained from carotid and iliac artery was confirmed by measuring PECAM‐1 and α‐SMA expression respectively. mRNA expression increased 1.8 – 4.1‐fold (p<0.05) for beclin‐1, LC3‐II, Atg3, Atg5, Atg7, Atg12, and Atg16 in iliac artery ECs, but not carotid artery ECs, from ETR vs. SED mice. All of these autophagy‐related genes in the M+A from iliac and carotid artery were similar in ETR and SED mice. LC3II:GAPDH and Atg3:GAPDH protein expression was greater (p<0.05) in aortic homogenates from ETR vs. SED mice. Collectively, exercise‐training increases the expression of autophagy‐related mRNA in iliac artery ECs, and autophagy‐related protein in arterial homogenates, relative to results obtained from sedentary animals. Ongoing experiments are determining whether exercise‐training increases basal expression of autophagy‐related mRNA and protein in the vasculature of old mice to an extent that attenuates age‐related arterial dysfunction.

Support or Funding Information

Supported by: UU Diabetes and Metabolism Center; UU Center on Aging; UU College of Health Research Committee; DRC at Washington University (5 P30 DK020579); and AHA 16GRNT31050004 (JDS).
Combined Norepinephrine and ATP Antagonism Attenuates the Vasoconstriction Response in Young Adult Skin
Authors: Krajek Alex C , Smaller Kevin A , Lang James A
Published: November 2023

Norepinephrine (NE) is responsible for ~60% of the vasoconstriction (VC) response to cold exposure in young adults whereas the remainder is due to unknown coreleased sympathetic adrenergic neurotransmitter(s). We hypothesize that ATP is a cotransmitter and thus, combined ATP and NE antagonism will further inhibit the reflex cutaneous VC response. Two protocols were conducted in young adults; both involved the placement of three microdialysis (MD) fibers in forearm skin and whole‐body cooling (Tsk = 30.5 °C). Protocol 1 infused 1) lactated Ringer's solution (control), 2) 10mM L‐NAME, and 3) purinergic receptor blockade with 1mM suramin + L‐NAME. Protocol 2 infused 1) Ringer's, 2) suramin + L‐NAME, and 3) suramin + L‐NAME + adrenoreceptor blockade with 5mM yohimbine + 1mM propranolol. Laser Doppler flux (LDF) was measured over each MD site and cutaneous vascular conductance (CVC) was calculated as CVC = LDF/MAP and expressed as percent changes from baseline (%ΔCVC). L‐NAME was used to block the vasodilatory influence of ATP and unmask the P2X‐mediated VC response to exogenous ATP infusion (−21 ± 2 %ΔCVC). During whole body cooling, the VC response (control: −39 ± 3 %ΔCVC) was attenuated in the suramin site (−21 ± 2 %ΔCVC) and further blunted with combined adrenoreceptor blockade (9 ± 1 %ΔCVC; p < 0.05). Compared to control (22 ± 1 %ΔCVC), suramin inhibited pharmacologically‐induced VC to tyramine (12 ± 2 %ΔCVC), which acts to displace adrenergic neurotransmitters from axon terminals. Collectively, these data indicate that ATP contributes to the cutaneous adrenergic VC response in humans.

Support or Funding Information

Funded by Iowa Osteopathic & Education Research Grant (IOER #03‐14‐01)
Intermittent Hypoxic Challenge in Conscious Rats Elevates Heart Rate But Does Not Increase Lumbar Sympathetic Nerve Activity
Authors: Muntzel Martin , Loera Jaclquelin , Coffee Gregory , Getsy Paulina , Lewis Stephen J
Published: November 2023

In humans, moderate duration hypoxia (20 min) stimulates well‐described increases in muscle sympathetic nerve activity (SNA) that persist after withdrawal of the hypoxic challenge. However, episodes of naturally occurring apnea in humans and animals are of shorter duration, and the effects of such brief exposures to hypoxia on SNA have been little studied. To test this, male Sprague‐Dawley rats were instrumented with radiotelemetry devices to record mean arterial pressure (MAP), heart rate (HR) and lumbar SNA. After 3 days of recovery from surgery, the animals were exposed to four consecutive episodes of hypoxia (10% O2, 90% N2), that were 5 min in duration and given 10 min apart, all while recording cardiovascular and ventilatory responses. In ongoing studies, we found that the repeated hypoxic episodes produced expected increases in tidal volume, breathing frequency, and minute veltilation. Hypoxia also activated increases in HR (+57 ± 21 bpm) accompanied by mild elevations in MAP (+6 ± 5 mmHg). Unexpectedly, the hypoxic challenges caused no change in lumbar SNA (from 100% to 106 ± 14%), and did not increase SNA following offset of the challenges. At study end, a testing of lumbar SNA quality revealed that the nerves responded appropriately to sodium nitroprusside, phenylephrine and to hexamethonium bromide. These data show that repeated short‐term hypoxic challenges did not did not elevate lumbar SNA in conscious rats.

Support or Funding Information

GalaxoSmithKline Pharmaceuticals
Adrenal chromaffin cell function in high‐altitude deer mice (Peromyscus maniculatus)
Authors: Pranckevicius Nicole A , Scott Angela L , Nurse Colin A , Scott Graham R
Published: November 2023

Hypoxia at high altitudes can activate the sympathetic nervous system, which could become maladaptive in high‐altitude natives if it is maintained over chronic periods. The deer mouse (Peromyscus maniculatus) has the largest altitudinal range of all North American mammals, with populations living above 4300m elevation. We hypothesized that high‐altitude deer mice might have altered the physiology of chromaffin cells in the adrenal gland to avoid chronic activation of the sympathetic response. We used captive breeding colonies derived from wild populations at high and low altitudes, and compared them in normoxia and after 6–8 weeks of acclimation to hypoxia (12kPa O2, simulating the PO2 at ~4300m). High‐altitude mice show lower rates of catecholamine secretion from adrenal slices (measured via carbon fibre amperometry) in response to stimulation by a nicotinic acetylcholine receptor agonist (nicotine). Here, we used ratiometric Ca2+ imaging of cultured chromaffin cells to assess whether the variation in catecholamine secretion resulted from variation in the Ca2+ signal for vesicular catecholamine release. The rise of intracellular Ca2+ in response to nicotine (1, 5, 25, 125μM) did not vary between populations and was not affected by hypoxia acclimation, suggesting that events downstream of Ca2+ influx likely contribute to population differences in catecholamine secretion. This appeared to include differences in catecholamine stores, which were lower in highlanders compared to lowlanders in cultured cells from normoxia‐acclimated mice. Our data therefore suggest that chronic sympathetic activation may be avoided in deer mice at high altitudes by a reduction in catecholamine storage and release from the adrenal gland.
The Effect of Methylglyoxal (MGO) on the Cardiac Myofilament
Authors: Papadaki Maria , Holewinski Ronald , Stachowski Marisa , Kirk Jonathan
Published: November 2023

Methylglyoxal (MGO), a byproduct of glycolysis and a reactive carbonyl species (RCS), is significantly elevated in diabetes. MGO adds post‐translational modifications by reacting with arginine and lysine residues to form irreversible carbonyl adducts. At basal concentrations, MGO is removed by glyoxal‐1 (GLO‐1), but at concentrations observed in diabetes, GLO‐1 cannot meet the demands and MGO modifications can accumulate. In the heart, MGO has been previously found to act on the ryanodine receptor and SERCA to depress calcium transients, and other proteins to induce cardiomyocyte apoptosis. However, the effect of MGO on the cardiac myofilament has never been studied. The aim of this study is to characterize the structural and functional effects of MGO on the myofilament. Skinned myocytes were isolated from ~100 μg of mouse left ventricle heart tissue, skinned using 0.3% Triton for 20 minutes and force‐Ca2+ relationships were measured. 20 minute exposure to 100 μM MGO reduced the myocyte maximal calcium activated force (Fmax) by 12 ± 4 % (n = 8, p = 0.048) and Ca2+ sensitivity by 45 ± 11 % (n = 8, p = 0.02). With 10 μM MGO, Ca2+ sensitivity was decreased by 67 ± 17 % (n = 9, p<0.01) but there was no effect on Fmax. Using mass spectrometry, we identified MGO modifications on several myofilament proteins in mouse myocytes treated with MGO including actin, myosin and myosin essential light chain. In a pilot study, using immunoprecipitation assay we were able to detect similar MGO modifications on myofilament proteins from human diabetic cardiomyopathy tissue that were not present in control hearts (n = 2/group). Our data show that these modifications would have significant implications on myofilament function in patients suffering from diabetic cardiomyopathy and other diseases affecting glucose metabolism.

Support or Funding Information

This project is supported by American Heart Association
Cholesterol Depletion Increased Cardiomyocyte Contractility Associated with Phosphorylation of Cytosolic AKT
Authors: Haque Mohammed Ziaul , McIntosh Victoria J. , Mohammad Ramzi M , Samra Abdul Badi Abou , Lasley Robert D
Published: November 2023

Introduction

Sarcolemmal cholesterol is concentrated in lipid rafts and caveolae, which are flask‐shaped invaginations of the plasma membrane and plays an important role for cell function. In cardiomyocyte the scaffolding protein caveolin‐3 permits the enrichment of cholesterol in caveolae, and caveolin‐3 interactions with numerous proteins regulate their function.

Hypothesis

We hypothesized that acute cholesterol depletion increases cardiomyocyte intracellular Ca2+ and contractility.

Methods

Ventricular myocytes, isolated from adult Sprague Dawley rats, were treated with the cholesterol reducing agent methyl‐β‐cyclodextrin (MβCD, 5 mM, 1 hr, room temperature). Total cellular cholesterol levels, caveolin‐3 localization, subcellular, AKT, ERK and p38 signaling, [Ca2+]i and contractility were assessed.

Results

Treatment with MβCD reduced ~45% cholesterol and shifted caveolin‐3 from cytoskeleton and triton‐insoluble fractions to the triton‐soluble fraction. Cholesterol depletion increased 2.4‐fold AKT phosphorylation only in cytosolic fraction, an effect that was independent of total cytosolic AKT. Cholesterol depletion increased ERK isoform phosphorylation in cytoskeletal, cytosolic, triton‐soluble and triton‐insoluble membrane fractions without altering their subcellular distributions. The primary effect of MβCD was on p38 subcellular distribution of p38α with little effect on p38 phosphorylation. Cholesterol depletion increased cardiomyocyte twitch amplitude and the rates of shortening and relaxation in conjunction with increased diastolic and systolic [Ca2+]i.

Conclusion

These results indicate that acute reductions in membrane cholesterol levels modulates subcellular caveolin‐3, AKT, ERK, p38 signaling, as well as increasing [Ca2+]i and contractility.

Support or Funding Information

This work was supported by National Heart, Lung, and Blood Institute, Grants HL‐66132 to RDL.
Time‐Released Caffeine Ingestion in Habitual Users May Extend Parasympathetic Influence as Determined by Heart Rate Variability
Authors: La Monica Michael B , Fukuda David H , Gonzalez Adam M , Wang Ran , Wells Adam J , Stout Jeffrey R , Hoffman Jay R
Published: November 2023

Heart rate variability (HRV) is a noninvasive method of identifying vagal and sympathetic control of heart rate via time‐domain and frequency‐domain measures. Caffeine has shown to enhance autonomic responsiveness by increasing parasympathetic influence, however a time‐release caffeine supplement has not yet been investigated.

OBJECTIVE

To determine the effects of a time‐release caffeine supplement on HRV over 8 hours.

METHODS

Ten men (25.9 ± 3.2 y; 1.81 ± 0.08 m; 92.9 ± 9.9 kg), who were habitual caffeine users (>200mg/day), volunteered to participate in an acute randomized, double‐blind, placebo‐controlled study. Participants performed three trials with seven days between each trial. During each trial, participants randomly consumed either 194 mg of caffeine in a multi‐ingredient supplement containing time‐release caffeine (TR‐CAF); a regular caffeine supplement (CAF); or a placebo (PL). Participants reported to the lab at 0800 hour following an 8‐hour fast and having abstained from caffeine. HRV was assessed for 10 min via Polar heart rate monitor with the participant lying in the supine position during baseline, before supplementation, and each hour during each 8 hour trial. Time‐domain [mean standard deviation of all normal‐to‐normal (NN) intervals (SDNN in ms), root mean square of differences between adjacent NN intervals (RMSSD in ms), the number of pairs of adjacent NN intervals differing by more than 50 ms within the entire recording (NN50), the proportion of NN50 count relative to the total number of all NN intervals (pNN50)] and frequency‐domain [low frequency (LF in ms2), high frequency (HF in ms2), total power (in ms2), LF/HF, an index of parasympathetic nervous system (PNS=HF/total power) measures were recorded. A two‐way [trial (CAF vs. TR‐CAF vs. PL) × time (BL, 1hr, 2hr, 3hr, 4hr, 5hr, 6hr, 7hr, 8hr)] RMANOVA was used to assess all HRV parameters.

RESULTS

A significant interaction was noted for PNS (p = .045). Post‐hoc analyses revealed elevations in PNS influence occurred in both TR‐CAF (0.27 ± 0.12, p = .045) and CAF (0.29 ± 0.16, p = .009) compared to PL (0.18 ± 0.08) at hour 6 and hour 7 in TR‐CAF (0.34 ± 0.15, p = .018) compared to PL (0.23 ± 0.13). There were significant main effects of time for RMSSD (p = .021) and pNN50 (p = .012).

DISCUSSION

Both caffeine supplements increased parasympathetic influences within the autonomic nervous system over an 8‐hour span. However, the time‐release caffeine supplement appeared to have a slightly longer lasting effect on parasympathetic influence than regular caffeine. Overall, caffeine in the concentrations ingested in this study increases vagal stimulation, but has no effect on other elements of HRV in habitual caffeine users.
Acute Changes in Left Ventricular Mechanics During Voluntary Apnea
Authors: Sutterfield Shelbi L , Smith Joshua R , Baumfalk Dryden R , Didier Kaylin D , Ade Carl J
Published: November 2023

Introduction

Obstructive sleep apnea (OSA) is characterized by intermittent apneic events and is associated with hypertension, sudden cardiac death, and acute cardiac infarction. During an apneic event asphyxia‐induced increases in sympathetic nerve activity result in subsequent increases in arterial blood pressure and systemic vascular resistance. However, it is currently unknown how cardiac mechanics are acutely impacted by these systemic responses to an apneic event. Therefore, the purpose of the present study was to evaluate changes in left ventricular systolic and diastolic function during voluntary apnea. We hypothesized that during voluntary apnea left ventricular systolic and diastolic function would be compromised in parallel with increases in arterial blood pressure and myocardial work.

Methods

9 healthy men (23 ± 3 yrs) were recruited for the study. Subjects performed multiple voluntary breath holds at functional residual capacity with 3–5 minutes in between. Beat‐by‐beat blood pressure, heart rate and stroke volume were measured continuously. End‐tidal CO2 was measured at end‐apnea. Tissue Doppler echocardiography was used to measure tissue velocities, and myocardial deformation via strain (S), and strain rate (SR) at the mid‐interventricular septum across 3 continuous cardiac cycles at baseline and end‐apnea.

Results

Systolic blood pressure (Δ13.8 ± 8.4 mmHg, p<0.01), mean arterial pressure (Δ12.4 ± 7.0 mmHg, p<0.01), and rate pressure product (Δ8.4 ± 5.6 mmHg × bpm 10−2, p<0.01) significantly increased with apnea, but not stroke volume (Δ3.3 ± 8.1 ml, p=0.26). Peak longitudinal systolic (Δ −0.56 ± 0.69 cm s−1, p=0.04) and early LV filling (Δ −2.32 ± 2.04 cm s−1, p<0.01) myocardial velocities were significantly decreased during the apnea. Longitudinal Systolic S (Δ −2.17 ± 2.36%, p=0.02) and SR (Δ −0.20 ± 0.29 1/s, p=0.07) were significantly decreased during the apnea. Early LV filling SR was not different compared to baseline with apnea (p=0.41).

Conclusion

Consistent with our hypotheses, left ventricular deformation was significantly impaired with voluntary apnea. These data suggest that the systemic increases in arterial pressure during voluntary apnea have an adverse effect on left ventricular systolic mechanics.